The American Journal of Orthopedics

Risk factors for dislocation after reverse total shoulder arthroplasty (RTSA) are not clearly defined. Prosthetic dislocation can result in poor patient satisfaction, worse functional outcomes, and return to the operating room.^1-3 As a result, identification of modifiable risk factors for complications represents an important research initiative for shoulder surgeons.

There is a paucity of literature devoted to the study of dislocation after RTSA. Chalmers and colleagues⁴ found a 2.9% (11/385) incidence of early dislocation within 3 months after index surgery—an improvement over the 15.8% reported for early instability over the period 2004–2006.⁵ As prosthesis design has improved and surgeons have become more comfortable with the RTSA prosthesis, surgical indications have expanded,^6,7 and dislocation rates appear to have decreased. Although the most common indication for RTSA continues to be cuff tear arthropathy (CTA),⁶ there has been increased use in rheumatoid arthritis^8-10; proximal humerus fractures, especially in cases of poor bone quality and unreliable fixation of tuberosities^11-13; and failed previous shoulder reconstruction.^14,15 As RTSA is performed more often, limiting the complications will become more important for both patient care and economics.

We conducted a study to analyze dislocation rates at our institution and to identify both modifiable and nonmodifiable risk factors for dislocation after RTSA. By identifying risk factors for dislocation, we will be able to implement additional perioperative clinical measures to reduce the incidence of dislocation.

Materials and Methods

This retrospective study of dislocation after RTSA was conducted at the Rothman Institute of Orthopedics and Methodist Hospital (Thomas Jefferson University Hospitals, Philadelphia, PA). After obtaining Institutional Review Board approval for the study, we searched our institution’s electronic database of shoulder arthroplasties to identify all RTSAs performed at our 2 large-volume urban institutions between September 27, 2010 and December 31, 2013. For the record search, International Classification of Diseases, Ninth Revision (ICD-9) codes were used (Table 1).

The medical records of each patient were used to identify independent variables that could be associated with dislocation rate. Demographic variables included sex, age, and race. Preoperative clinical data included body mass index (BMI), etiology of shoulder disease leading to RTSA, individual comorbidities, and Charlson Comorbidity Index (CCI)¹⁶ modified to be used with ICD-9 codes.¹⁷ In addition, prior shoulder surgery history and arthroplasty type (primary or revision) were determined. Postoperative considerations were time to dislocation, mechanism of dislocation, and intervention(s) needed for dislocation. Although the institutional database did not include operative variables such as prosthesis type and surgical approach, all 6 surgeons in this study were using a standard deltopectoral approach in beach-chair position with a Grammont style prosthesis for RTSA cases.

Descriptive statistics for RTSA patients and the dislocation subpopulation were compiled. Bivariate analysis was used to evaluate which of the previously described variables influenced dislocation rates. Last, multivariate logistic regression analysis was performed to evaluate which factors were independent predictors of dislocation. We included demographic variables (age, sex, ethnicity), clinical variables (BMI, individual comorbidities, CCI), and surgical variables (primary vs revision, diagnosis at time of surgery). All statistical analyses were performed with Excel 2013 (Microsoft) and SPSS Statistics Version 20.0 (SPSS Inc.).

Results

From the database, we identified 487 patients who underwent 510 RTSAs during the study period. These surgeries were performed by 6 shoulder and elbow fellowship–trained surgeons. Of the 510 RTSAs, 393 (77.1%) were primary cases, and 117 (22.9%) were revision cases.

Of the 510 shoulders that underwent RTSA, 15 (2.9%; 14 patients) dislocated. Of these 15 cases, 5 were primary (1.3% of all primary cases) and 10 were revision (8.5% of all revision cases). Mean time from index surgery to diagnosis of dislocation was 58.2 days (range, 0-319 days). One dislocation occurred immediately after surgery, 2 after falls, 4 from patient-identified low-energy mechanisms of injury, and 8 without known inciting events. Nine dislocations (60%) did not have a subscapularis repair (7 were irreparable, 2 underwent subscapularis peel without repair), and the other 6 were repaired primarily (Table 2).

Discussion

With more RTSAs being performed, evaluation of their common complications becomes increasingly important.¹⁸ We found a 3.0% rate of dislocation after RTSA, which is consistent with the most recently reported incidence⁴ and falls within the previously described range of 0% to 8.6%.^19-26 Of the clinical risk factors identified in this study, those previously described were prior surgery, subscapularis insufficiency, higher BMI, and male sex.⁴ However, our finding of lower risk of dislocation after RTSA for primary rotator cuff pathology was not previously described. Although Chalmers and colleagues⁴ did not report this lower risk, 3 (27.3%) of their 11 patients with dislocation had primary CTA, compared with 1 (6.7%) of 15 patients in the present study.⁴ Our literature review did not identify any studies that independently reported the dislocation rate in patients who underwent RTSA for rotator cuff failure.

The risk factors of subscapularis irreparability and revision surgery suggest the importance of the soft-tissue envelope and bony anatomy in dislocation prevention. Previous analyses have suggested implant malpositioning,^27,28 poor subscapularis quality,²⁹ and inadequate muscle tensioning^5,30-32 as risk factors for RTSA. Patients with an irreparable subscapularis tendon have often had multiple surgeries with compromise to the muscle/soft-tissue envelope or bony anatomy of the shoulder. A biomechanical study by Gutiérrez and colleagues³¹ found the compressive forces of the soft tissue at the glenohumeral joint to be the most important contributor to stability in the RTSA prosthesis. In clinical studies, the role of the subscapularis in preventing instability after RTSA remains unclear. Edwards and colleagues²⁹ prospectively compared dislocation rates in patients with reparable and irreparable subscapularis tendons during RTSA and found a higher rate of dislocation in the irreparable subscapularis group. Of note, patients in the irreparable subscapularis group also had more complex diagnoses, including proximal humeral nonunion, fixed glenohumeral dislocation, and failed prior arthroplasty. Clark and colleagues³³ retrospectively analyzed subscapularis repair in 2 RTSA groups and found no appreciable effect on complication rate, dislocation events, range-of-motion gains, or pain relief.

Our finding that higher BMI is an independent risk factor was previously described.⁴ The association is unclear but could be related to implant positioning, difficulty in intraoperative assessment of muscle tensioning, or body habitus that may generate a lever arm for impingement and dislocation when the arm is in adduction. Last, our finding that male sex is a risk factor for dislocation approached significance, and this relationship was previously reported.⁴ This could be attributable to a higher rate of activity or of indolent infection in male patients.^34,35Besides studying risk factors for dislocation after RTSA, we investigated treatment. None of our patients were treated successfully and definitively with closed reduction in the clinic. This finding diverges from findings in studies by Teusink and colleagues² and Chalmers and colleagues,⁴who respectively reported 62% and 44% rates of success with closed reduction. Our cohort of 14 patients with 15 dislocations required a total of 17 trips to the operating room after dislocation. This significantly higher rate of return to the operating room suggests that dislocation after RTSA may be a more costly and morbid problem than has been previously described.

This study had several weaknesses. Despite its large consecutive series of patients, the study was retrospective, and several variables that would be documented and controlled in a prospective study could not be measured here. Specifically, neither preoperative physical examination nor patient-specific assessments of pain or function were consistently obtained. Similarly, postoperative patient-specific instruments of outcomes evaluation were not obtained consistently, so results of patients with dislocation could not be compared with those of a control group. In addition, preoperative and postoperative radiographs were not consistently present in our electronic medical records, so the influence of preoperative bony anatomy, intraoperative limb lengthening, and any implant malpositioning could not be determined. Furthermore, operative details, such as reparability of the subscapularis, were not fully available for the control group and could not be included in statistical analysis. In addition, that the known dislocation risk factor of male sex⁴ was identified here but was not significant in multivariate regression analysis suggests that this study may not have been adequately powered to identify a significant difference in dislocation rate between the sexes. Last, though our results suggested associations between the aforementioned variables and dislocation after RTSA, a truly causative relationship could not be confirmed with this study design or analysis. Therefore, our study findings are hypothesis-generating and may indicate a benefit to greater deltoid tensioning, use of retentive liners, or more conservative rehabilitation protocols for high-risk patients.

Conclusion

Dislocation after RTSA is an uncommon complication that often requires a return to the operating room. This study identified a modifiable risk factor (higher BMI) and 3 nonmodifiable risk factors (male sex, subscapularis insufficiency, revision surgery) for dislocation after RTSA. In contrast, patients who undergo RTSA for primary rotator cuff pathology are unlikely to dislocate after surgery. This low risk of dislocation after RTSA for primary cuff pathology was not previously described. Patients in the higher risk category may benefit from preoperative lifestyle modification, intraoperative techniques for increasing stability, and more conservative therapy after surgery. In addition, unlike previous investigations, this study did not find closed reduction in the clinic alone to be successful in definitively treating this patient population.

Am J Orthop. 2016;45(7):E444-E450. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Risk factors for dislocation after reverse total shoulder arthroplasty (RTSA) are not clearly defined. Prosthetic dislocation can result in poor patient satisfaction, worse functional outcomes, and return to the operating room.^1-3 As a result, identification of modifiable risk factors for complications represents an important research initiative for shoulder surgeons.

There is a paucity of literature devoted to the study of dislocation after RTSA. Chalmers and colleagues⁴ found a 2.9% (11/385) incidence of early dislocation within 3 months after index surgery—an improvement over the 15.8% reported for early instability over the period 2004–2006.⁵ As prosthesis design has improved and surgeons have become more comfortable with the RTSA prosthesis, surgical indications have expanded,^6,7 and dislocation rates appear to have decreased. Although the most common indication for RTSA continues to be cuff tear arthropathy (CTA),⁶ there has been increased use in rheumatoid arthritis^8-10; proximal humerus fractures, especially in cases of poor bone quality and unreliable fixation of tuberosities^11-13; and failed previous shoulder reconstruction.^14,15 As RTSA is performed more often, limiting the complications will become more important for both patient care and economics.

We conducted a study to analyze dislocation rates at our institution and to identify both modifiable and nonmodifiable risk factors for dislocation after RTSA. By identifying risk factors for dislocation, we will be able to implement additional perioperative clinical measures to reduce the incidence of dislocation.

Materials and Methods

This retrospective study of dislocation after RTSA was conducted at the Rothman Institute of Orthopedics and Methodist Hospital (Thomas Jefferson University Hospitals, Philadelphia, PA). After obtaining Institutional Review Board approval for the study, we searched our institution’s electronic database of shoulder arthroplasties to identify all RTSAs performed at our 2 large-volume urban institutions between September 27, 2010 and December 31, 2013. For the record search, International Classification of Diseases, Ninth Revision (ICD-9) codes were used (Table 1).

The medical records of each patient were used to identify independent variables that could be associated with dislocation rate. Demographic variables included sex, age, and race. Preoperative clinical data included body mass index (BMI), etiology of shoulder disease leading to RTSA, individual comorbidities, and Charlson Comorbidity Index (CCI)¹⁶ modified to be used with ICD-9 codes.¹⁷ In addition, prior shoulder surgery history and arthroplasty type (primary or revision) were determined. Postoperative considerations were time to dislocation, mechanism of dislocation, and intervention(s) needed for dislocation. Although the institutional database did not include operative variables such as prosthesis type and surgical approach, all 6 surgeons in this study were using a standard deltopectoral approach in beach-chair position with a Grammont style prosthesis for RTSA cases.

Descriptive statistics for RTSA patients and the dislocation subpopulation were compiled. Bivariate analysis was used to evaluate which of the previously described variables influenced dislocation rates. Last, multivariate logistic regression analysis was performed to evaluate which factors were independent predictors of dislocation. We included demographic variables (age, sex, ethnicity), clinical variables (BMI, individual comorbidities, CCI), and surgical variables (primary vs revision, diagnosis at time of surgery). All statistical analyses were performed with Excel 2013 (Microsoft) and SPSS Statistics Version 20.0 (SPSS Inc.).

Results

From the database, we identified 487 patients who underwent 510 RTSAs during the study period. These surgeries were performed by 6 shoulder and elbow fellowship–trained surgeons. Of the 510 RTSAs, 393 (77.1%) were primary cases, and 117 (22.9%) were revision cases.

Of the 510 shoulders that underwent RTSA, 15 (2.9%; 14 patients) dislocated. Of these 15 cases, 5 were primary (1.3% of all primary cases) and 10 were revision (8.5% of all revision cases). Mean time from index surgery to diagnosis of dislocation was 58.2 days (range, 0-319 days). One dislocation occurred immediately after surgery, 2 after falls, 4 from patient-identified low-energy mechanisms of injury, and 8 without known inciting events. Nine dislocations (60%) did not have a subscapularis repair (7 were irreparable, 2 underwent subscapularis peel without repair), and the other 6 were repaired primarily (Table 2).

Discussion

With more RTSAs being performed, evaluation of their common complications becomes increasingly important.¹⁸ We found a 3.0% rate of dislocation after RTSA, which is consistent with the most recently reported incidence⁴ and falls within the previously described range of 0% to 8.6%.^19-26 Of the clinical risk factors identified in this study, those previously described were prior surgery, subscapularis insufficiency, higher BMI, and male sex.⁴ However, our finding of lower risk of dislocation after RTSA for primary rotator cuff pathology was not previously described. Although Chalmers and colleagues⁴ did not report this lower risk, 3 (27.3%) of their 11 patients with dislocation had primary CTA, compared with 1 (6.7%) of 15 patients in the present study.⁴ Our literature review did not identify any studies that independently reported the dislocation rate in patients who underwent RTSA for rotator cuff failure.

The risk factors of subscapularis irreparability and revision surgery suggest the importance of the soft-tissue envelope and bony anatomy in dislocation prevention. Previous analyses have suggested implant malpositioning,^27,28 poor subscapularis quality,²⁹ and inadequate muscle tensioning^5,30-32 as risk factors for RTSA. Patients with an irreparable subscapularis tendon have often had multiple surgeries with compromise to the muscle/soft-tissue envelope or bony anatomy of the shoulder. A biomechanical study by Gutiérrez and colleagues³¹ found the compressive forces of the soft tissue at the glenohumeral joint to be the most important contributor to stability in the RTSA prosthesis. In clinical studies, the role of the subscapularis in preventing instability after RTSA remains unclear. Edwards and colleagues²⁹ prospectively compared dislocation rates in patients with reparable and irreparable subscapularis tendons during RTSA and found a higher rate of dislocation in the irreparable subscapularis group. Of note, patients in the irreparable subscapularis group also had more complex diagnoses, including proximal humeral nonunion, fixed glenohumeral dislocation, and failed prior arthroplasty. Clark and colleagues³³ retrospectively analyzed subscapularis repair in 2 RTSA groups and found no appreciable effect on complication rate, dislocation events, range-of-motion gains, or pain relief.

Our finding that higher BMI is an independent risk factor was previously described.⁴ The association is unclear but could be related to implant positioning, difficulty in intraoperative assessment of muscle tensioning, or body habitus that may generate a lever arm for impingement and dislocation when the arm is in adduction. Last, our finding that male sex is a risk factor for dislocation approached significance, and this relationship was previously reported.⁴ This could be attributable to a higher rate of activity or of indolent infection in male patients.^34,35Besides studying risk factors for dislocation after RTSA, we investigated treatment. None of our patients were treated successfully and definitively with closed reduction in the clinic. This finding diverges from findings in studies by Teusink and colleagues² and Chalmers and colleagues,⁴who respectively reported 62% and 44% rates of success with closed reduction. Our cohort of 14 patients with 15 dislocations required a total of 17 trips to the operating room after dislocation. This significantly higher rate of return to the operating room suggests that dislocation after RTSA may be a more costly and morbid problem than has been previously described.

This study had several weaknesses. Despite its large consecutive series of patients, the study was retrospective, and several variables that would be documented and controlled in a prospective study could not be measured here. Specifically, neither preoperative physical examination nor patient-specific assessments of pain or function were consistently obtained. Similarly, postoperative patient-specific instruments of outcomes evaluation were not obtained consistently, so results of patients with dislocation could not be compared with those of a control group. In addition, preoperative and postoperative radiographs were not consistently present in our electronic medical records, so the influence of preoperative bony anatomy, intraoperative limb lengthening, and any implant malpositioning could not be determined. Furthermore, operative details, such as reparability of the subscapularis, were not fully available for the control group and could not be included in statistical analysis. In addition, that the known dislocation risk factor of male sex⁴ was identified here but was not significant in multivariate regression analysis suggests that this study may not have been adequately powered to identify a significant difference in dislocation rate between the sexes. Last, though our results suggested associations between the aforementioned variables and dislocation after RTSA, a truly causative relationship could not be confirmed with this study design or analysis. Therefore, our study findings are hypothesis-generating and may indicate a benefit to greater deltoid tensioning, use of retentive liners, or more conservative rehabilitation protocols for high-risk patients.

Conclusion

Dislocation after RTSA is an uncommon complication that often requires a return to the operating room. This study identified a modifiable risk factor (higher BMI) and 3 nonmodifiable risk factors (male sex, subscapularis insufficiency, revision surgery) for dislocation after RTSA. In contrast, patients who undergo RTSA for primary rotator cuff pathology are unlikely to dislocate after surgery. This low risk of dislocation after RTSA for primary cuff pathology was not previously described. Patients in the higher risk category may benefit from preoperative lifestyle modification, intraoperative techniques for increasing stability, and more conservative therapy after surgery. In addition, unlike previous investigations, this study did not find closed reduction in the clinic alone to be successful in definitively treating this patient population.

Am J Orthop. 2016;45(7):E444-E450. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Risk factors for dislocation after reverse total shoulder arthroplasty (RTSA) are not clearly defined. Prosthetic dislocation can result in poor patient satisfaction, worse functional outcomes, and return to the operating room.^1-3 As a result, identification of modifiable risk factors for complications represents an important research initiative for shoulder surgeons.

There is a paucity of literature devoted to the study of dislocation after RTSA. Chalmers and colleagues⁴ found a 2.9% (11/385) incidence of early dislocation within 3 months after index surgery—an improvement over the 15.8% reported for early instability over the period 2004–2006.⁵ As prosthesis design has improved and surgeons have become more comfortable with the RTSA prosthesis, surgical indications have expanded,^6,7 and dislocation rates appear to have decreased. Although the most common indication for RTSA continues to be cuff tear arthropathy (CTA),⁶ there has been increased use in rheumatoid arthritis^8-10; proximal humerus fractures, especially in cases of poor bone quality and unreliable fixation of tuberosities^11-13; and failed previous shoulder reconstruction.^14,15 As RTSA is performed more often, limiting the complications will become more important for both patient care and economics.

We conducted a study to analyze dislocation rates at our institution and to identify both modifiable and nonmodifiable risk factors for dislocation after RTSA. By identifying risk factors for dislocation, we will be able to implement additional perioperative clinical measures to reduce the incidence of dislocation.

Materials and Methods

This retrospective study of dislocation after RTSA was conducted at the Rothman Institute of Orthopedics and Methodist Hospital (Thomas Jefferson University Hospitals, Philadelphia, PA). After obtaining Institutional Review Board approval for the study, we searched our institution’s electronic database of shoulder arthroplasties to identify all RTSAs performed at our 2 large-volume urban institutions between September 27, 2010 and December 31, 2013. For the record search, International Classification of Diseases, Ninth Revision (ICD-9) codes were used (Table 1).

The medical records of each patient were used to identify independent variables that could be associated with dislocation rate. Demographic variables included sex, age, and race. Preoperative clinical data included body mass index (BMI), etiology of shoulder disease leading to RTSA, individual comorbidities, and Charlson Comorbidity Index (CCI)¹⁶ modified to be used with ICD-9 codes.¹⁷ In addition, prior shoulder surgery history and arthroplasty type (primary or revision) were determined. Postoperative considerations were time to dislocation, mechanism of dislocation, and intervention(s) needed for dislocation. Although the institutional database did not include operative variables such as prosthesis type and surgical approach, all 6 surgeons in this study were using a standard deltopectoral approach in beach-chair position with a Grammont style prosthesis for RTSA cases.

Descriptive statistics for RTSA patients and the dislocation subpopulation were compiled. Bivariate analysis was used to evaluate which of the previously described variables influenced dislocation rates. Last, multivariate logistic regression analysis was performed to evaluate which factors were independent predictors of dislocation. We included demographic variables (age, sex, ethnicity), clinical variables (BMI, individual comorbidities, CCI), and surgical variables (primary vs revision, diagnosis at time of surgery). All statistical analyses were performed with Excel 2013 (Microsoft) and SPSS Statistics Version 20.0 (SPSS Inc.).

Results

From the database, we identified 487 patients who underwent 510 RTSAs during the study period. These surgeries were performed by 6 shoulder and elbow fellowship–trained surgeons. Of the 510 RTSAs, 393 (77.1%) were primary cases, and 117 (22.9%) were revision cases.

Of the 510 shoulders that underwent RTSA, 15 (2.9%; 14 patients) dislocated. Of these 15 cases, 5 were primary (1.3% of all primary cases) and 10 were revision (8.5% of all revision cases). Mean time from index surgery to diagnosis of dislocation was 58.2 days (range, 0-319 days). One dislocation occurred immediately after surgery, 2 after falls, 4 from patient-identified low-energy mechanisms of injury, and 8 without known inciting events. Nine dislocations (60%) did not have a subscapularis repair (7 were irreparable, 2 underwent subscapularis peel without repair), and the other 6 were repaired primarily (Table 2).

Discussion

With more RTSAs being performed, evaluation of their common complications becomes increasingly important.¹⁸ We found a 3.0% rate of dislocation after RTSA, which is consistent with the most recently reported incidence⁴ and falls within the previously described range of 0% to 8.6%.^19-26 Of the clinical risk factors identified in this study, those previously described were prior surgery, subscapularis insufficiency, higher BMI, and male sex.⁴ However, our finding of lower risk of dislocation after RTSA for primary rotator cuff pathology was not previously described. Although Chalmers and colleagues⁴ did not report this lower risk, 3 (27.3%) of their 11 patients with dislocation had primary CTA, compared with 1 (6.7%) of 15 patients in the present study.⁴ Our literature review did not identify any studies that independently reported the dislocation rate in patients who underwent RTSA for rotator cuff failure.

The risk factors of subscapularis irreparability and revision surgery suggest the importance of the soft-tissue envelope and bony anatomy in dislocation prevention. Previous analyses have suggested implant malpositioning,^27,28 poor subscapularis quality,²⁹ and inadequate muscle tensioning^5,30-32 as risk factors for RTSA. Patients with an irreparable subscapularis tendon have often had multiple surgeries with compromise to the muscle/soft-tissue envelope or bony anatomy of the shoulder. A biomechanical study by Gutiérrez and colleagues³¹ found the compressive forces of the soft tissue at the glenohumeral joint to be the most important contributor to stability in the RTSA prosthesis. In clinical studies, the role of the subscapularis in preventing instability after RTSA remains unclear. Edwards and colleagues²⁹ prospectively compared dislocation rates in patients with reparable and irreparable subscapularis tendons during RTSA and found a higher rate of dislocation in the irreparable subscapularis group. Of note, patients in the irreparable subscapularis group also had more complex diagnoses, including proximal humeral nonunion, fixed glenohumeral dislocation, and failed prior arthroplasty. Clark and colleagues³³ retrospectively analyzed subscapularis repair in 2 RTSA groups and found no appreciable effect on complication rate, dislocation events, range-of-motion gains, or pain relief.

Our finding that higher BMI is an independent risk factor was previously described.⁴ The association is unclear but could be related to implant positioning, difficulty in intraoperative assessment of muscle tensioning, or body habitus that may generate a lever arm for impingement and dislocation when the arm is in adduction. Last, our finding that male sex is a risk factor for dislocation approached significance, and this relationship was previously reported.⁴ This could be attributable to a higher rate of activity or of indolent infection in male patients.^34,35Besides studying risk factors for dislocation after RTSA, we investigated treatment. None of our patients were treated successfully and definitively with closed reduction in the clinic. This finding diverges from findings in studies by Teusink and colleagues² and Chalmers and colleagues,⁴who respectively reported 62% and 44% rates of success with closed reduction. Our cohort of 14 patients with 15 dislocations required a total of 17 trips to the operating room after dislocation. This significantly higher rate of return to the operating room suggests that dislocation after RTSA may be a more costly and morbid problem than has been previously described.

This study had several weaknesses. Despite its large consecutive series of patients, the study was retrospective, and several variables that would be documented and controlled in a prospective study could not be measured here. Specifically, neither preoperative physical examination nor patient-specific assessments of pain or function were consistently obtained. Similarly, postoperative patient-specific instruments of outcomes evaluation were not obtained consistently, so results of patients with dislocation could not be compared with those of a control group. In addition, preoperative and postoperative radiographs were not consistently present in our electronic medical records, so the influence of preoperative bony anatomy, intraoperative limb lengthening, and any implant malpositioning could not be determined. Furthermore, operative details, such as reparability of the subscapularis, were not fully available for the control group and could not be included in statistical analysis. In addition, that the known dislocation risk factor of male sex⁴ was identified here but was not significant in multivariate regression analysis suggests that this study may not have been adequately powered to identify a significant difference in dislocation rate between the sexes. Last, though our results suggested associations between the aforementioned variables and dislocation after RTSA, a truly causative relationship could not be confirmed with this study design or analysis. Therefore, our study findings are hypothesis-generating and may indicate a benefit to greater deltoid tensioning, use of retentive liners, or more conservative rehabilitation protocols for high-risk patients.

Conclusion

Dislocation after RTSA is an uncommon complication that often requires a return to the operating room. This study identified a modifiable risk factor (higher BMI) and 3 nonmodifiable risk factors (male sex, subscapularis insufficiency, revision surgery) for dislocation after RTSA. In contrast, patients who undergo RTSA for primary rotator cuff pathology are unlikely to dislocate after surgery. This low risk of dislocation after RTSA for primary cuff pathology was not previously described. Patients in the higher risk category may benefit from preoperative lifestyle modification, intraoperative techniques for increasing stability, and more conservative therapy after surgery. In addition, unlike previous investigations, this study did not find closed reduction in the clinic alone to be successful in definitively treating this patient population.

Am J Orthop. 2016;45(7):E444-E450. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The training model for orthopedic resident education has been transformed. Surgeon factors, patient expectations, financial and legal concerns, associated costs, and work hour restrictions have put pressure on resident autonomy in the operating room.^1,2 At the end of resident training, the expectation is that board-eligible surgeons will have the surgical skills necessary to perform a wide range of surgical procedures.^3,4 Helping residents become proficient for independent practice requires a multidisciplinary approach.⁵ This approach, regardless of its details, requires investment in time, resources, expertise, and funding.

Many residency programs are trying to bridge the gap between observation and autonomy with surgical simulation. According to one study, 76% of residency programs have a surgical skills laboratory, and 46% have a structured surgical skills curriculum.⁶Surgical skills preparation is available in different modalities. Synthetic bones, virtual reality, and arthroscopic simulators represent potential opportunities for practice. Through these modalities, residents become more comfortable with the tools used in orthopedic procedures. Cadaveric dissection allows them to practice surgical approaches in the setting of real anatomy.¹ Independent dissection helps them appreciate the planes, layers, and proximity of crucial body structures and understand important surgical anatomy.⁴Surgical simulation can be expensive, and funding comes in many forms. Cadaver laboratories require investment in specimens, facilities, and time away from clinical obligations.⁴ Cadaver availability varies with regional resources, and the cost of a cadaver ranges from $1000 to $2000.^7,8 Arthroscopic simulators and virtual reality programs are expensive as well. These modalities range from a less expensive video box (with standard arthroscopic equipment) to a virtual reality haptic simulation costing a residency program as much as $80,000.⁹ Synthetic bone simulations are less expensive but require investment in faculty time and outside implants and instrumentation.¹⁰ The cost of simulation raises the question of funding sources.

Funding surgical simulation is a challenge. In a national survey of program directors, conducted by Karam and colleagues,⁶ 87.3% of residencies cited lack of funding as the most significant barrier to a formal surgical skills program. Simulation can be residency-sponsored, industry-sponsored, or specialty-sponsored. Karam and colleagues⁶ found that department, hospital, and industry funding were the 3 main sponsors of surgical simulation. Each funding mechanism brings its own set of challenges and opportunities. Industry-sponsored simulation provides a cost-effective outlet for residency programs. However, this type of funding is under scrutiny, as industry funding for education becomes more transparent. In addition, industry funding typically limits the technology that can be used during the simulation to the sponsor’s technology. Courses offered by the American Academy of Orthopaedic Surgeons (AAOS) and a number of subspecialty societies provide less conflicted simulation at reasonable cost.

If residents, residency programs, hospitals, industry, subspecialty societies, and the AAOS are going to invest in resident education through simulation, then the effect of simulation on resident education must be understood. Intuitively, simulation as a modality for improving resident skills makes sense. For residency programs to invest in simulation and surgical skills, different modalities must be objectively evaluated and their utility validated. If simulation is to become valuable, first it must be done correctly.

Kneebone¹¹ proposed a framework for evaluating simulation. In this framework, simulation should allow for sustained, deliberate practice in a safe environment. It should provide access to expert tutors when appropriate. It should map onto real-life clinical experience. Last, it should provide a supportive, motivational, learner-centered milieu. Residents and program directors should consider this framework when deciding which simulation exercises to engage in and which resources to supply for exercises. Having supportive supervision during simulation can lead to a positive outcome. Likewise, learning incorrect techniques or bad habits or having inexperienced teachers can have the opposite effect.

Several authors have reviewed the evidence and found simulation to be an important part of orthopedic resident education.^{1,2,4,9,12,13} They have evaluated cadaveric simulation, synthetic bone simulation, arthroscopic simulation, and virtual reality simulation. Their studies demonstrated that simulation is an effective tool and provided objective criteria for evaluating residents on a larger scale. In a blinded, randomized study by Howells and colleagues,¹⁴ junior residents were either trained on a knee simulator or received no training before evaluation. Those who received the training scored significantly better than their peers on validated assessment measures.

The literature on different modalities shows simulation is an effective teaching tool for general orthopedic surgical skills⁵; knee, shoulder, and ankle arthroscopy^14-21; spine surgery²²; and orthopedic trauma surgery.^23-26 Investigators in several other surgical specialties have studied the utility of simulation, and many are incorporating simulation into their resident curricula.

More effective simulation seems correlated with a yearlong structured curriculum rather than with intermittent, isolated experiences.³ Dunn and colleagues²⁷ evaluated arthroscopic shoulder simulation 1 year after a training exercise. The group that received formal training did better than the control group on an initial arthroscopic surgery skill evaluation tool. At 1 year, however, the gains made through training were lost.

Simulation is a new paradigm for resident education. It offers multiple opportunities and challenges for residents, residency programs, industry partners, specialty and subspecialty societies, and medical examiners. The Accreditation Council for Graduate Medical Education’s ACGME Program Requirements for Graduate Medical Education in Orthopaedic Surgery requires of residency programs a didactic curriculum dedicated to basic motor skills in addition to a dedicated space for facilitating basic surgical skills training.²⁸ Residency programs must demonstrate to ACGME their commitment to surgical skills training and simulation. Implementation of simulation for resident education has many variables, including funding, type of simulation, demonstrated efficacy, provision of supervision, resident time, and establishment of a formal curriculum. Residents and residency programs should embrace this changing paradigm to bridge the gap between observation and autonomy in orthopedic surgical and arthroscopic technique.

Am J Orthop. 2016;45(7):E426-E428. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The training model for orthopedic resident education has been transformed. Surgeon factors, patient expectations, financial and legal concerns, associated costs, and work hour restrictions have put pressure on resident autonomy in the operating room.^1,2 At the end of resident training, the expectation is that board-eligible surgeons will have the surgical skills necessary to perform a wide range of surgical procedures.^3,4 Helping residents become proficient for independent practice requires a multidisciplinary approach.⁵ This approach, regardless of its details, requires investment in time, resources, expertise, and funding.

Many residency programs are trying to bridge the gap between observation and autonomy with surgical simulation. According to one study, 76% of residency programs have a surgical skills laboratory, and 46% have a structured surgical skills curriculum.⁶Surgical skills preparation is available in different modalities. Synthetic bones, virtual reality, and arthroscopic simulators represent potential opportunities for practice. Through these modalities, residents become more comfortable with the tools used in orthopedic procedures. Cadaveric dissection allows them to practice surgical approaches in the setting of real anatomy.¹ Independent dissection helps them appreciate the planes, layers, and proximity of crucial body structures and understand important surgical anatomy.⁴Surgical simulation can be expensive, and funding comes in many forms. Cadaver laboratories require investment in specimens, facilities, and time away from clinical obligations.⁴ Cadaver availability varies with regional resources, and the cost of a cadaver ranges from $1000 to $2000.^7,8 Arthroscopic simulators and virtual reality programs are expensive as well. These modalities range from a less expensive video box (with standard arthroscopic equipment) to a virtual reality haptic simulation costing a residency program as much as $80,000.⁹ Synthetic bone simulations are less expensive but require investment in faculty time and outside implants and instrumentation.¹⁰ The cost of simulation raises the question of funding sources.

Funding surgical simulation is a challenge. In a national survey of program directors, conducted by Karam and colleagues,⁶ 87.3% of residencies cited lack of funding as the most significant barrier to a formal surgical skills program. Simulation can be residency-sponsored, industry-sponsored, or specialty-sponsored. Karam and colleagues⁶ found that department, hospital, and industry funding were the 3 main sponsors of surgical simulation. Each funding mechanism brings its own set of challenges and opportunities. Industry-sponsored simulation provides a cost-effective outlet for residency programs. However, this type of funding is under scrutiny, as industry funding for education becomes more transparent. In addition, industry funding typically limits the technology that can be used during the simulation to the sponsor’s technology. Courses offered by the American Academy of Orthopaedic Surgeons (AAOS) and a number of subspecialty societies provide less conflicted simulation at reasonable cost.

If residents, residency programs, hospitals, industry, subspecialty societies, and the AAOS are going to invest in resident education through simulation, then the effect of simulation on resident education must be understood. Intuitively, simulation as a modality for improving resident skills makes sense. For residency programs to invest in simulation and surgical skills, different modalities must be objectively evaluated and their utility validated. If simulation is to become valuable, first it must be done correctly.

Kneebone¹¹ proposed a framework for evaluating simulation. In this framework, simulation should allow for sustained, deliberate practice in a safe environment. It should provide access to expert tutors when appropriate. It should map onto real-life clinical experience. Last, it should provide a supportive, motivational, learner-centered milieu. Residents and program directors should consider this framework when deciding which simulation exercises to engage in and which resources to supply for exercises. Having supportive supervision during simulation can lead to a positive outcome. Likewise, learning incorrect techniques or bad habits or having inexperienced teachers can have the opposite effect.

Several authors have reviewed the evidence and found simulation to be an important part of orthopedic resident education.^{1,2,4,9,12,13} They have evaluated cadaveric simulation, synthetic bone simulation, arthroscopic simulation, and virtual reality simulation. Their studies demonstrated that simulation is an effective tool and provided objective criteria for evaluating residents on a larger scale. In a blinded, randomized study by Howells and colleagues,¹⁴ junior residents were either trained on a knee simulator or received no training before evaluation. Those who received the training scored significantly better than their peers on validated assessment measures.

The literature on different modalities shows simulation is an effective teaching tool for general orthopedic surgical skills⁵; knee, shoulder, and ankle arthroscopy^14-21; spine surgery²²; and orthopedic trauma surgery.^23-26 Investigators in several other surgical specialties have studied the utility of simulation, and many are incorporating simulation into their resident curricula.

More effective simulation seems correlated with a yearlong structured curriculum rather than with intermittent, isolated experiences.³ Dunn and colleagues²⁷ evaluated arthroscopic shoulder simulation 1 year after a training exercise. The group that received formal training did better than the control group on an initial arthroscopic surgery skill evaluation tool. At 1 year, however, the gains made through training were lost.

Simulation is a new paradigm for resident education. It offers multiple opportunities and challenges for residents, residency programs, industry partners, specialty and subspecialty societies, and medical examiners. The Accreditation Council for Graduate Medical Education’s ACGME Program Requirements for Graduate Medical Education in Orthopaedic Surgery requires of residency programs a didactic curriculum dedicated to basic motor skills in addition to a dedicated space for facilitating basic surgical skills training.²⁸ Residency programs must demonstrate to ACGME their commitment to surgical skills training and simulation. Implementation of simulation for resident education has many variables, including funding, type of simulation, demonstrated efficacy, provision of supervision, resident time, and establishment of a formal curriculum. Residents and residency programs should embrace this changing paradigm to bridge the gap between observation and autonomy in orthopedic surgical and arthroscopic technique.

Am J Orthop. 2016;45(7):E426-E428. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The training model for orthopedic resident education has been transformed. Surgeon factors, patient expectations, financial and legal concerns, associated costs, and work hour restrictions have put pressure on resident autonomy in the operating room.^1,2 At the end of resident training, the expectation is that board-eligible surgeons will have the surgical skills necessary to perform a wide range of surgical procedures.^3,4 Helping residents become proficient for independent practice requires a multidisciplinary approach.⁵ This approach, regardless of its details, requires investment in time, resources, expertise, and funding.

Many residency programs are trying to bridge the gap between observation and autonomy with surgical simulation. According to one study, 76% of residency programs have a surgical skills laboratory, and 46% have a structured surgical skills curriculum.⁶Surgical skills preparation is available in different modalities. Synthetic bones, virtual reality, and arthroscopic simulators represent potential opportunities for practice. Through these modalities, residents become more comfortable with the tools used in orthopedic procedures. Cadaveric dissection allows them to practice surgical approaches in the setting of real anatomy.¹ Independent dissection helps them appreciate the planes, layers, and proximity of crucial body structures and understand important surgical anatomy.⁴Surgical simulation can be expensive, and funding comes in many forms. Cadaver laboratories require investment in specimens, facilities, and time away from clinical obligations.⁴ Cadaver availability varies with regional resources, and the cost of a cadaver ranges from $1000 to $2000.^7,8 Arthroscopic simulators and virtual reality programs are expensive as well. These modalities range from a less expensive video box (with standard arthroscopic equipment) to a virtual reality haptic simulation costing a residency program as much as $80,000.⁹ Synthetic bone simulations are less expensive but require investment in faculty time and outside implants and instrumentation.¹⁰ The cost of simulation raises the question of funding sources.

Funding surgical simulation is a challenge. In a national survey of program directors, conducted by Karam and colleagues,⁶ 87.3% of residencies cited lack of funding as the most significant barrier to a formal surgical skills program. Simulation can be residency-sponsored, industry-sponsored, or specialty-sponsored. Karam and colleagues⁶ found that department, hospital, and industry funding were the 3 main sponsors of surgical simulation. Each funding mechanism brings its own set of challenges and opportunities. Industry-sponsored simulation provides a cost-effective outlet for residency programs. However, this type of funding is under scrutiny, as industry funding for education becomes more transparent. In addition, industry funding typically limits the technology that can be used during the simulation to the sponsor’s technology. Courses offered by the American Academy of Orthopaedic Surgeons (AAOS) and a number of subspecialty societies provide less conflicted simulation at reasonable cost.

If residents, residency programs, hospitals, industry, subspecialty societies, and the AAOS are going to invest in resident education through simulation, then the effect of simulation on resident education must be understood. Intuitively, simulation as a modality for improving resident skills makes sense. For residency programs to invest in simulation and surgical skills, different modalities must be objectively evaluated and their utility validated. If simulation is to become valuable, first it must be done correctly.

Kneebone¹¹ proposed a framework for evaluating simulation. In this framework, simulation should allow for sustained, deliberate practice in a safe environment. It should provide access to expert tutors when appropriate. It should map onto real-life clinical experience. Last, it should provide a supportive, motivational, learner-centered milieu. Residents and program directors should consider this framework when deciding which simulation exercises to engage in and which resources to supply for exercises. Having supportive supervision during simulation can lead to a positive outcome. Likewise, learning incorrect techniques or bad habits or having inexperienced teachers can have the opposite effect.

Several authors have reviewed the evidence and found simulation to be an important part of orthopedic resident education.^{1,2,4,9,12,13} They have evaluated cadaveric simulation, synthetic bone simulation, arthroscopic simulation, and virtual reality simulation. Their studies demonstrated that simulation is an effective tool and provided objective criteria for evaluating residents on a larger scale. In a blinded, randomized study by Howells and colleagues,¹⁴ junior residents were either trained on a knee simulator or received no training before evaluation. Those who received the training scored significantly better than their peers on validated assessment measures.

The literature on different modalities shows simulation is an effective teaching tool for general orthopedic surgical skills⁵; knee, shoulder, and ankle arthroscopy^14-21; spine surgery²²; and orthopedic trauma surgery.^23-26 Investigators in several other surgical specialties have studied the utility of simulation, and many are incorporating simulation into their resident curricula.

More effective simulation seems correlated with a yearlong structured curriculum rather than with intermittent, isolated experiences.³ Dunn and colleagues²⁷ evaluated arthroscopic shoulder simulation 1 year after a training exercise. The group that received formal training did better than the control group on an initial arthroscopic surgery skill evaluation tool. At 1 year, however, the gains made through training were lost.

Simulation is a new paradigm for resident education. It offers multiple opportunities and challenges for residents, residency programs, industry partners, specialty and subspecialty societies, and medical examiners. The Accreditation Council for Graduate Medical Education’s ACGME Program Requirements for Graduate Medical Education in Orthopaedic Surgery requires of residency programs a didactic curriculum dedicated to basic motor skills in addition to a dedicated space for facilitating basic surgical skills training.²⁸ Residency programs must demonstrate to ACGME their commitment to surgical skills training and simulation. Implementation of simulation for resident education has many variables, including funding, type of simulation, demonstrated efficacy, provision of supervision, resident time, and establishment of a formal curriculum. Residents and residency programs should embrace this changing paradigm to bridge the gap between observation and autonomy in orthopedic surgical and arthroscopic technique.

Am J Orthop. 2016;45(7):E426-E428. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The rate of medical visits for rotator cuff pathology and the US incidence of arthroscopic rotator cuff repair (RCR) have increased over the past 10 years.¹ The increased use of RCR has been justified with improved patient outcomes.^2,3 Advances in surgical techniques and instrumentation have contributed to better outcomes for patients with rotator cuff pathology.^3-5 Several studies have validated RCR with functional outcome measures, cost–benefit analysis, and health-related quality-of-life measurements.^6-9

Healthcare reimbursement models are being changed to include capitated care, pay for performance, and penalties.¹⁰ Given the changing healthcare climate and the increasing incidence of RCR, it is becoming increasingly important for orthopedic surgeons to critically evaluate and modify their practice and procedures to decrease costs without compromising outcomes.¹¹ RCR outcome studies have focused on comparing open/mini-open with arthroscopic techniques, and single-row with double-row techniques, among others.^4,12-18 Furthermore, several studies on the cost-effectiveness of these surgical techniques have been conducted.^19-21Arthroscopic anchorless (transosseous [TO]) RCR, which is increasingly popular,²² combines the minimal invasiveness of arthroscopic procedures with the biomechanical strength of open TO repair. In addition, this technique avoids the potential complications and costs associated with suture anchors, such as anchor pullout and greater tuberosity osteolysis.^22,23 Several studies have documented the effectiveness of this technique.^24-26 Biomechanical and clinical outcome data supporting arthroscopic TO-RCR have been published, but there are no reports of studies that have analyzed the cost savings associated with this technique.

In this study, we compared implant costs associated with arthroscopic TO-RCR and arthroscopic TO-equivalent (TOE) RCR. We also evaluated these techniques’ operative time and outcomes. Our hypothesis was that arthroscopic TO-RCR can be performed at lower cost and without increasing operative time or compromising outcomes.

Materials and Methods

Our Institutional Review Board approved this study. Between February 2013 and January 2014, participating surgeons performed 43 arthroscopic TO-RCRs that met the study’s inclusion criteria. Twenty-one of the 43 patients enrolled and became the study group. The control group of 21 patients, who underwent arthroscopic TOE-RCR the preceding year (between January 2012 and January 2013), was matched to the study group on tear size and concomitant procedures, including biceps treatment, labral treatment, acromioplasty, and distal clavicle excision (Table 1).

The primary outcome measure was implant cost (amount paid by institution). Cost was determined and reported by an independent third party using Cerner Surginet as the operating room documentation system and McKessen Pathways Materials Management System for item pricing.

All arthroscopic RCRs were performed by 1 of 3 orthopedic surgeons fellowship-trained in either sports medicine or shoulder and elbow surgery. Using the Cofield classification,²⁷ the treating surgeon recorded the size of the rotator cuff tear: small (<1 cm), medium (1-3 cm), large (3-5 cm), massive (>5 cm). The surgeon also recorded the number of suture anchors used, repair technique, biceps treatment, execution of subacromial decompression, execution of distal clavicle excision, and intraoperative complications. TO repair surgical technique is described in the next section. TOE repair was double-row repair with suture anchors. The number of suture anchors varied by tear size: small (3 anchors), medium (2-5 anchors), large (4-6 anchors), massive (4-5 anchors).

Secondary outcome measures were operative time (time from cut to close) and scores on pain VAS (visual analog scale), SANE (Single Assessment Numeric Evaluation), and SST (Simple Shoulder Test). Demographic information was also obtained: age, sex, body mass index, smoking status (Table 1). All patients were asked to fill out questionnaires before surgery and 3, 6, and >12 months after surgery. Outcome surveys were scored by a single research coordinator, who recorded each patient’s outcome scores at the preoperative and postoperative intervals. Follow-up of >12 months was reached by 17 (81%) of the 21 TO patients and 14 (67%) of the 21 TOE patients. For >12 months, the overall rate of follow-up was 74%.

All patients followed the same postoperative rehabilitation protocol: sling immobilization with pendulums for 6 weeks starting at 2 weeks, passive range of motion starting at 6 weeks, and active range of motion starting at 8 weeks. At 3 months, they were allowed progressive resistant exercises with a 10-pound limit, and at 4.5 months they progressed to a 20-pound limit. At 6 months, they were cleared for discharge.

Surgical Technique: Arthroscopic Transosseous Repair

Surgery was performed with the patient in either the beach-chair position or the lateral decubitus position, based on surgeon preference. Our technique is similar to what has been described in the past.^22,28 The glenohumeral joint is accessed through a standard posterior portal, followed by an anterior accessory portal through the rotator interval. Standard diagnostic arthroscopy is performed and intra-articular pathology addressed. Next, the scope is placed in the subacromial space through the posterior portal. A lateral subacromial portal is established and cannulated, and a bursectomy performed. The scope is then placed in a posterolateral portal for better visualization of the rotator cuff tear. The greater tuberosity is débrided with a curette to prepare the bed for repair. An ArthroTunneler (Tornier) is used to pass sutures through the greater tuberosity. For standard 2-tunnel repair, 3 sutures are placed through each tunnel. All 6 sutures are next passed (using a suture passer) through the rotator cuff. The second and fifth suture ends that are passed through the cuff are brought out through the cannula and tied together. They are then brought into the shoulder by pulling on the opposite ends and tied alongside the greater tuberosity to create a box stitch. The box stitch acts as a medial row fixation and as a rip stitch that strengthens the vertical mattress sutures against pullout. The other 4 sutures are tied in vertical mattress configuration.

Statistical Analysis

After obtaining the TO and TOE implant costs, we compared them using a generalized linear model with negative binomial distribution and an identity link function so returned parameters were in additive dollars. This comparison included evaluation of tear size and concomitant procedures. Operative times for TO and TOE were obtained and evaluated, and then compared using time-to-event analysis and the log-rank test. Outcome scores were obtained from patients at baseline and 3, 6, and >12 months after surgery and were compared using a linear mixed model that identified change in outcome scores over time, and difference in outcome scores between the TO and TOE groups.

Results

Table 1 lists patient demographics, including age, sex, body mass index, smoking status, and concomitant procedures. The TO and TOE groups had identical tear-size distributions. In addition, they had similar numbers of concomitant procedures, though our study was underpowered to confirm equivalence. Treatment techniques differed: more biceps tenodesis cases in the TO group (n = 12) than in the TOE group (n = 2) and more biceps tenotomy cases in the TOE group (n = 8) than in the TO group (n = 1).

TO implant cost was significantly lower than TOE implant cost for all tear sizes and independent of concomitant procedures (Figure 1).

Discussion

RCR is one of the most common orthopedic surgical procedures, and its use has increased over the past decade.^9,21 This increase coincides with the emergence of new repair techniques and implants. These advancements come at a cost. Given the increasingly cost-conscious healthcare environment and its changing reimbursement models, now surgeons must evaluate the economics of their surgical procedures in an attempt to decrease costs without compromising outcomes. We hypothesized that arthroscopic TO-RCR can be performed at lower cost relative to arthroscopic TOE-RCR and without increasing operative time or compromising short-term outcomes.

Studies on the cost-effectiveness of different RCR techniques have been conducted.^19-21 Adla and colleagues¹⁹ found that open RCR was more cost-effective than arthroscopic RCR, with most of the difference attributable to disposables and suture anchors. Genuario and colleagues²¹ found that double-row RCR was not as cost-effective as single-row RCR in treating tears of any size. They attributed the difference to 2 more anchors and about 15 more minutes in the operating room.

The increased interest in healthcare costs and the understanding that a substantial part of the cost of arthroscopic RCR is attributable to implants (suture anchors, specifically) led to recent efforts to eliminate the need for anchors. Newly available instrumentation was designed to assist in arthroscopic anchorless repair constructs using the concepts of traditional TO repair.²² Although still considered to be the RCR gold standard, TO fixation has been used less often in recent years, owing to the shift from open to arthroscopic surgery.²⁴ Arthroscopic TO-RCR allows for all the benefits of arthroscopic surgery, plus the biological and mechanical benefits of traditional open or mini-open TO repair. In addition, this technique eliminates the cost of anchors. Kummer and colleagues²⁵ confirmed with biomechanical testing that arthroscopic TO repair and double-row TOE repair are similar in strength, with a trend of less tendon displacement in the TO group.

Our study results support the hypothesis that arthroscopic TO repair provides significant cost savings over tear size–matched arthroscopic TOE repair. Implant cost was substantially higher for TOE repair than for TO repair. Mean (SD) total savings of $946.91 ($100.70) (P < .0001) can be realized performing TO rather than TOE repair. In the United States, where about 250,000 RCRs are performed each year, the use of TO repair would result in an annual savings of almost $250 million.⁶Operative time was analyzed as well. Running an operating room in the United States costs an estimated $62 per minute (range, $22-$133 per minute).²⁹ Much of this cost is indirect, unrelated to the surgery (eg, capital investment, personnel, insurance), and is being paid even when the operating room is not in use. Therefore, for the hospital’s bottom line, operative time savings are less important than direct cost savings (supplies, implants). However, operative time has more of an effect on the surgeon’s bottom line, and longer procedures reduce the number of surgeries that can be performed and billed. We found no significant difference in operative time between TO and TOE repairs. Critical evaluation revealed that operative time was 5.96 minutes shorter for TOE repairs, but this difference was not significant (P = .677).

Our study results showed no significant difference in clinical outcomes between TO and TOE repair patients. Both groups’ outcome scores improved. At all follow-ups, both groups’ VAS, SANE, and SST scores were significantly improved. Overall, this is the first study to validate the proposed cost benefit of arthroscopic TO repair and confirm no compromise in patient outcomes.

This study had limitations. First, it enrolled relatively few patients, particularly those with small tears. In addition, despite the fact that patients were matched on tear size and concomitant procedures, the groups differed in their biceps pathology treatments. Of the 13 TO patients who had biceps treatment, 12 underwent tenodesis (1 had tenotomy); in contrast, of the 10 TOE patients who had biceps treatment, only 2 underwent tenodesis (8 had tenotomy). The difference is explained by the consecutive course of this study and the increasing popularity of tenodesis over tenotomy. The TOE group underwent surgery before the TO group did, at a time when the involved surgeons were routinely performing tenotomy more than tenodesis. We did not include the costs of implants related to biceps treatment in our analysis, as our focus was on the implant cost of RCR. As for operative time, biceps tenodesis would be expected to extend surgery and potentially affect the comparison of operative times between the TO and TOE groups. However, despite the fact that 12 of the 13 TO patients underwent biceps tenodesis, there was no significant difference in overall operative time. Last, regarding the effect of biceps treatment on clinical outcomes, there are no data showing improved outcomes with tenodesis over tenotomy in the setting of RCR.

A final limitation is lack of data from longer term (>12 months) follow-up for all patients. Our analysis included cost and operative time data for all 42 enrolled patients, but our clinical outcome data represent only 74% of the patients enrolled. Eleven of the 42 patients were lost to follow-up at >12 months, and outcome scores could not be obtained, despite multiple attempts at contact (phone, mail, email). The study design and primary outcome variable focused on cost analysis rather than clinical outcomes. Nevertheless, our data support our hypothesis that there is no difference in clinical outcomes between TO and TOE repairs.

Conclusion

Arthroscopic TO-RCR provides significant cost savings over arthroscopic TOE-RCR without increasing operative time or compromising outcomes. Arthroscopic TO-RCR may have an important role in the evolving healthcare environment and its changing reimbursement models.

Am J Orthop. 2016;45(7):E415-E420. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The rate of medical visits for rotator cuff pathology and the US incidence of arthroscopic rotator cuff repair (RCR) have increased over the past 10 years.¹ The increased use of RCR has been justified with improved patient outcomes.^2,3 Advances in surgical techniques and instrumentation have contributed to better outcomes for patients with rotator cuff pathology.^3-5 Several studies have validated RCR with functional outcome measures, cost–benefit analysis, and health-related quality-of-life measurements.^6-9

Healthcare reimbursement models are being changed to include capitated care, pay for performance, and penalties.¹⁰ Given the changing healthcare climate and the increasing incidence of RCR, it is becoming increasingly important for orthopedic surgeons to critically evaluate and modify their practice and procedures to decrease costs without compromising outcomes.¹¹ RCR outcome studies have focused on comparing open/mini-open with arthroscopic techniques, and single-row with double-row techniques, among others.^4,12-18 Furthermore, several studies on the cost-effectiveness of these surgical techniques have been conducted.^19-21Arthroscopic anchorless (transosseous [TO]) RCR, which is increasingly popular,²² combines the minimal invasiveness of arthroscopic procedures with the biomechanical strength of open TO repair. In addition, this technique avoids the potential complications and costs associated with suture anchors, such as anchor pullout and greater tuberosity osteolysis.^22,23 Several studies have documented the effectiveness of this technique.^24-26 Biomechanical and clinical outcome data supporting arthroscopic TO-RCR have been published, but there are no reports of studies that have analyzed the cost savings associated with this technique.

In this study, we compared implant costs associated with arthroscopic TO-RCR and arthroscopic TO-equivalent (TOE) RCR. We also evaluated these techniques’ operative time and outcomes. Our hypothesis was that arthroscopic TO-RCR can be performed at lower cost and without increasing operative time or compromising outcomes.

Materials and Methods

Our Institutional Review Board approved this study. Between February 2013 and January 2014, participating surgeons performed 43 arthroscopic TO-RCRs that met the study’s inclusion criteria. Twenty-one of the 43 patients enrolled and became the study group. The control group of 21 patients, who underwent arthroscopic TOE-RCR the preceding year (between January 2012 and January 2013), was matched to the study group on tear size and concomitant procedures, including biceps treatment, labral treatment, acromioplasty, and distal clavicle excision (Table 1).

The primary outcome measure was implant cost (amount paid by institution). Cost was determined and reported by an independent third party using Cerner Surginet as the operating room documentation system and McKessen Pathways Materials Management System for item pricing.

All arthroscopic RCRs were performed by 1 of 3 orthopedic surgeons fellowship-trained in either sports medicine or shoulder and elbow surgery. Using the Cofield classification,²⁷ the treating surgeon recorded the size of the rotator cuff tear: small (<1 cm), medium (1-3 cm), large (3-5 cm), massive (>5 cm). The surgeon also recorded the number of suture anchors used, repair technique, biceps treatment, execution of subacromial decompression, execution of distal clavicle excision, and intraoperative complications. TO repair surgical technique is described in the next section. TOE repair was double-row repair with suture anchors. The number of suture anchors varied by tear size: small (3 anchors), medium (2-5 anchors), large (4-6 anchors), massive (4-5 anchors).

Secondary outcome measures were operative time (time from cut to close) and scores on pain VAS (visual analog scale), SANE (Single Assessment Numeric Evaluation), and SST (Simple Shoulder Test). Demographic information was also obtained: age, sex, body mass index, smoking status (Table 1). All patients were asked to fill out questionnaires before surgery and 3, 6, and >12 months after surgery. Outcome surveys were scored by a single research coordinator, who recorded each patient’s outcome scores at the preoperative and postoperative intervals. Follow-up of >12 months was reached by 17 (81%) of the 21 TO patients and 14 (67%) of the 21 TOE patients. For >12 months, the overall rate of follow-up was 74%.

All patients followed the same postoperative rehabilitation protocol: sling immobilization with pendulums for 6 weeks starting at 2 weeks, passive range of motion starting at 6 weeks, and active range of motion starting at 8 weeks. At 3 months, they were allowed progressive resistant exercises with a 10-pound limit, and at 4.5 months they progressed to a 20-pound limit. At 6 months, they were cleared for discharge.

Surgical Technique: Arthroscopic Transosseous Repair

Surgery was performed with the patient in either the beach-chair position or the lateral decubitus position, based on surgeon preference. Our technique is similar to what has been described in the past.^22,28 The glenohumeral joint is accessed through a standard posterior portal, followed by an anterior accessory portal through the rotator interval. Standard diagnostic arthroscopy is performed and intra-articular pathology addressed. Next, the scope is placed in the subacromial space through the posterior portal. A lateral subacromial portal is established and cannulated, and a bursectomy performed. The scope is then placed in a posterolateral portal for better visualization of the rotator cuff tear. The greater tuberosity is débrided with a curette to prepare the bed for repair. An ArthroTunneler (Tornier) is used to pass sutures through the greater tuberosity. For standard 2-tunnel repair, 3 sutures are placed through each tunnel. All 6 sutures are next passed (using a suture passer) through the rotator cuff. The second and fifth suture ends that are passed through the cuff are brought out through the cannula and tied together. They are then brought into the shoulder by pulling on the opposite ends and tied alongside the greater tuberosity to create a box stitch. The box stitch acts as a medial row fixation and as a rip stitch that strengthens the vertical mattress sutures against pullout. The other 4 sutures are tied in vertical mattress configuration.

Statistical Analysis

After obtaining the TO and TOE implant costs, we compared them using a generalized linear model with negative binomial distribution and an identity link function so returned parameters were in additive dollars. This comparison included evaluation of tear size and concomitant procedures. Operative times for TO and TOE were obtained and evaluated, and then compared using time-to-event analysis and the log-rank test. Outcome scores were obtained from patients at baseline and 3, 6, and >12 months after surgery and were compared using a linear mixed model that identified change in outcome scores over time, and difference in outcome scores between the TO and TOE groups.

Results

Table 1 lists patient demographics, including age, sex, body mass index, smoking status, and concomitant procedures. The TO and TOE groups had identical tear-size distributions. In addition, they had similar numbers of concomitant procedures, though our study was underpowered to confirm equivalence. Treatment techniques differed: more biceps tenodesis cases in the TO group (n = 12) than in the TOE group (n = 2) and more biceps tenotomy cases in the TOE group (n = 8) than in the TO group (n = 1).

TO implant cost was significantly lower than TOE implant cost for all tear sizes and independent of concomitant procedures (Figure 1).

Discussion

RCR is one of the most common orthopedic surgical procedures, and its use has increased over the past decade.^9,21 This increase coincides with the emergence of new repair techniques and implants. These advancements come at a cost. Given the increasingly cost-conscious healthcare environment and its changing reimbursement models, now surgeons must evaluate the economics of their surgical procedures in an attempt to decrease costs without compromising outcomes. We hypothesized that arthroscopic TO-RCR can be performed at lower cost relative to arthroscopic TOE-RCR and without increasing operative time or compromising short-term outcomes.

Studies on the cost-effectiveness of different RCR techniques have been conducted.^19-21 Adla and colleagues¹⁹ found that open RCR was more cost-effective than arthroscopic RCR, with most of the difference attributable to disposables and suture anchors. Genuario and colleagues²¹ found that double-row RCR was not as cost-effective as single-row RCR in treating tears of any size. They attributed the difference to 2 more anchors and about 15 more minutes in the operating room.

The increased interest in healthcare costs and the understanding that a substantial part of the cost of arthroscopic RCR is attributable to implants (suture anchors, specifically) led to recent efforts to eliminate the need for anchors. Newly available instrumentation was designed to assist in arthroscopic anchorless repair constructs using the concepts of traditional TO repair.²² Although still considered to be the RCR gold standard, TO fixation has been used less often in recent years, owing to the shift from open to arthroscopic surgery.²⁴ Arthroscopic TO-RCR allows for all the benefits of arthroscopic surgery, plus the biological and mechanical benefits of traditional open or mini-open TO repair. In addition, this technique eliminates the cost of anchors. Kummer and colleagues²⁵ confirmed with biomechanical testing that arthroscopic TO repair and double-row TOE repair are similar in strength, with a trend of less tendon displacement in the TO group.

Our study results support the hypothesis that arthroscopic TO repair provides significant cost savings over tear size–matched arthroscopic TOE repair. Implant cost was substantially higher for TOE repair than for TO repair. Mean (SD) total savings of $946.91 ($100.70) (P < .0001) can be realized performing TO rather than TOE repair. In the United States, where about 250,000 RCRs are performed each year, the use of TO repair would result in an annual savings of almost $250 million.⁶Operative time was analyzed as well. Running an operating room in the United States costs an estimated $62 per minute (range, $22-$133 per minute).²⁹ Much of this cost is indirect, unrelated to the surgery (eg, capital investment, personnel, insurance), and is being paid even when the operating room is not in use. Therefore, for the hospital’s bottom line, operative time savings are less important than direct cost savings (supplies, implants). However, operative time has more of an effect on the surgeon’s bottom line, and longer procedures reduce the number of surgeries that can be performed and billed. We found no significant difference in operative time between TO and TOE repairs. Critical evaluation revealed that operative time was 5.96 minutes shorter for TOE repairs, but this difference was not significant (P = .677).

Our study results showed no significant difference in clinical outcomes between TO and TOE repair patients. Both groups’ outcome scores improved. At all follow-ups, both groups’ VAS, SANE, and SST scores were significantly improved. Overall, this is the first study to validate the proposed cost benefit of arthroscopic TO repair and confirm no compromise in patient outcomes.

This study had limitations. First, it enrolled relatively few patients, particularly those with small tears. In addition, despite the fact that patients were matched on tear size and concomitant procedures, the groups differed in their biceps pathology treatments. Of the 13 TO patients who had biceps treatment, 12 underwent tenodesis (1 had tenotomy); in contrast, of the 10 TOE patients who had biceps treatment, only 2 underwent tenodesis (8 had tenotomy). The difference is explained by the consecutive course of this study and the increasing popularity of tenodesis over tenotomy. The TOE group underwent surgery before the TO group did, at a time when the involved surgeons were routinely performing tenotomy more than tenodesis. We did not include the costs of implants related to biceps treatment in our analysis, as our focus was on the implant cost of RCR. As for operative time, biceps tenodesis would be expected to extend surgery and potentially affect the comparison of operative times between the TO and TOE groups. However, despite the fact that 12 of the 13 TO patients underwent biceps tenodesis, there was no significant difference in overall operative time. Last, regarding the effect of biceps treatment on clinical outcomes, there are no data showing improved outcomes with tenodesis over tenotomy in the setting of RCR.

A final limitation is lack of data from longer term (>12 months) follow-up for all patients. Our analysis included cost and operative time data for all 42 enrolled patients, but our clinical outcome data represent only 74% of the patients enrolled. Eleven of the 42 patients were lost to follow-up at >12 months, and outcome scores could not be obtained, despite multiple attempts at contact (phone, mail, email). The study design and primary outcome variable focused on cost analysis rather than clinical outcomes. Nevertheless, our data support our hypothesis that there is no difference in clinical outcomes between TO and TOE repairs.

Conclusion

Arthroscopic TO-RCR provides significant cost savings over arthroscopic TOE-RCR without increasing operative time or compromising outcomes. Arthroscopic TO-RCR may have an important role in the evolving healthcare environment and its changing reimbursement models.

Am J Orthop. 2016;45(7):E415-E420. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The rate of medical visits for rotator cuff pathology and the US incidence of arthroscopic rotator cuff repair (RCR) have increased over the past 10 years.¹ The increased use of RCR has been justified with improved patient outcomes.^2,3 Advances in surgical techniques and instrumentation have contributed to better outcomes for patients with rotator cuff pathology.^3-5 Several studies have validated RCR with functional outcome measures, cost–benefit analysis, and health-related quality-of-life measurements.^6-9

Healthcare reimbursement models are being changed to include capitated care, pay for performance, and penalties.¹⁰ Given the changing healthcare climate and the increasing incidence of RCR, it is becoming increasingly important for orthopedic surgeons to critically evaluate and modify their practice and procedures to decrease costs without compromising outcomes.¹¹ RCR outcome studies have focused on comparing open/mini-open with arthroscopic techniques, and single-row with double-row techniques, among others.^4,12-18 Furthermore, several studies on the cost-effectiveness of these surgical techniques have been conducted.^19-21Arthroscopic anchorless (transosseous [TO]) RCR, which is increasingly popular,²² combines the minimal invasiveness of arthroscopic procedures with the biomechanical strength of open TO repair. In addition, this technique avoids the potential complications and costs associated with suture anchors, such as anchor pullout and greater tuberosity osteolysis.^22,23 Several studies have documented the effectiveness of this technique.^24-26 Biomechanical and clinical outcome data supporting arthroscopic TO-RCR have been published, but there are no reports of studies that have analyzed the cost savings associated with this technique.

In this study, we compared implant costs associated with arthroscopic TO-RCR and arthroscopic TO-equivalent (TOE) RCR. We also evaluated these techniques’ operative time and outcomes. Our hypothesis was that arthroscopic TO-RCR can be performed at lower cost and without increasing operative time or compromising outcomes.

Materials and Methods

Our Institutional Review Board approved this study. Between February 2013 and January 2014, participating surgeons performed 43 arthroscopic TO-RCRs that met the study’s inclusion criteria. Twenty-one of the 43 patients enrolled and became the study group. The control group of 21 patients, who underwent arthroscopic TOE-RCR the preceding year (between January 2012 and January 2013), was matched to the study group on tear size and concomitant procedures, including biceps treatment, labral treatment, acromioplasty, and distal clavicle excision (Table 1).

The primary outcome measure was implant cost (amount paid by institution). Cost was determined and reported by an independent third party using Cerner Surginet as the operating room documentation system and McKessen Pathways Materials Management System for item pricing.

All arthroscopic RCRs were performed by 1 of 3 orthopedic surgeons fellowship-trained in either sports medicine or shoulder and elbow surgery. Using the Cofield classification,²⁷ the treating surgeon recorded the size of the rotator cuff tear: small (<1 cm), medium (1-3 cm), large (3-5 cm), massive (>5 cm). The surgeon also recorded the number of suture anchors used, repair technique, biceps treatment, execution of subacromial decompression, execution of distal clavicle excision, and intraoperative complications. TO repair surgical technique is described in the next section. TOE repair was double-row repair with suture anchors. The number of suture anchors varied by tear size: small (3 anchors), medium (2-5 anchors), large (4-6 anchors), massive (4-5 anchors).

Secondary outcome measures were operative time (time from cut to close) and scores on pain VAS (visual analog scale), SANE (Single Assessment Numeric Evaluation), and SST (Simple Shoulder Test). Demographic information was also obtained: age, sex, body mass index, smoking status (Table 1). All patients were asked to fill out questionnaires before surgery and 3, 6, and >12 months after surgery. Outcome surveys were scored by a single research coordinator, who recorded each patient’s outcome scores at the preoperative and postoperative intervals. Follow-up of >12 months was reached by 17 (81%) of the 21 TO patients and 14 (67%) of the 21 TOE patients. For >12 months, the overall rate of follow-up was 74%.

All patients followed the same postoperative rehabilitation protocol: sling immobilization with pendulums for 6 weeks starting at 2 weeks, passive range of motion starting at 6 weeks, and active range of motion starting at 8 weeks. At 3 months, they were allowed progressive resistant exercises with a 10-pound limit, and at 4.5 months they progressed to a 20-pound limit. At 6 months, they were cleared for discharge.

Surgical Technique: Arthroscopic Transosseous Repair

Surgery was performed with the patient in either the beach-chair position or the lateral decubitus position, based on surgeon preference. Our technique is similar to what has been described in the past.^22,28 The glenohumeral joint is accessed through a standard posterior portal, followed by an anterior accessory portal through the rotator interval. Standard diagnostic arthroscopy is performed and intra-articular pathology addressed. Next, the scope is placed in the subacromial space through the posterior portal. A lateral subacromial portal is established and cannulated, and a bursectomy performed. The scope is then placed in a posterolateral portal for better visualization of the rotator cuff tear. The greater tuberosity is débrided with a curette to prepare the bed for repair. An ArthroTunneler (Tornier) is used to pass sutures through the greater tuberosity. For standard 2-tunnel repair, 3 sutures are placed through each tunnel. All 6 sutures are next passed (using a suture passer) through the rotator cuff. The second and fifth suture ends that are passed through the cuff are brought out through the cannula and tied together. They are then brought into the shoulder by pulling on the opposite ends and tied alongside the greater tuberosity to create a box stitch. The box stitch acts as a medial row fixation and as a rip stitch that strengthens the vertical mattress sutures against pullout. The other 4 sutures are tied in vertical mattress configuration.

Statistical Analysis

After obtaining the TO and TOE implant costs, we compared them using a generalized linear model with negative binomial distribution and an identity link function so returned parameters were in additive dollars. This comparison included evaluation of tear size and concomitant procedures. Operative times for TO and TOE were obtained and evaluated, and then compared using time-to-event analysis and the log-rank test. Outcome scores were obtained from patients at baseline and 3, 6, and >12 months after surgery and were compared using a linear mixed model that identified change in outcome scores over time, and difference in outcome scores between the TO and TOE groups.

Results

Table 1 lists patient demographics, including age, sex, body mass index, smoking status, and concomitant procedures. The TO and TOE groups had identical tear-size distributions. In addition, they had similar numbers of concomitant procedures, though our study was underpowered to confirm equivalence. Treatment techniques differed: more biceps tenodesis cases in the TO group (n = 12) than in the TOE group (n = 2) and more biceps tenotomy cases in the TOE group (n = 8) than in the TO group (n = 1).

TO implant cost was significantly lower than TOE implant cost for all tear sizes and independent of concomitant procedures (Figure 1).

Discussion

RCR is one of the most common orthopedic surgical procedures, and its use has increased over the past decade.^9,21 This increase coincides with the emergence of new repair techniques and implants. These advancements come at a cost. Given the increasingly cost-conscious healthcare environment and its changing reimbursement models, now surgeons must evaluate the economics of their surgical procedures in an attempt to decrease costs without compromising outcomes. We hypothesized that arthroscopic TO-RCR can be performed at lower cost relative to arthroscopic TOE-RCR and without increasing operative time or compromising short-term outcomes.

Studies on the cost-effectiveness of different RCR techniques have been conducted.^19-21 Adla and colleagues¹⁹ found that open RCR was more cost-effective than arthroscopic RCR, with most of the difference attributable to disposables and suture anchors. Genuario and colleagues²¹ found that double-row RCR was not as cost-effective as single-row RCR in treating tears of any size. They attributed the difference to 2 more anchors and about 15 more minutes in the operating room.

The increased interest in healthcare costs and the understanding that a substantial part of the cost of arthroscopic RCR is attributable to implants (suture anchors, specifically) led to recent efforts to eliminate the need for anchors. Newly available instrumentation was designed to assist in arthroscopic anchorless repair constructs using the concepts of traditional TO repair.²² Although still considered to be the RCR gold standard, TO fixation has been used less often in recent years, owing to the shift from open to arthroscopic surgery.²⁴ Arthroscopic TO-RCR allows for all the benefits of arthroscopic surgery, plus the biological and mechanical benefits of traditional open or mini-open TO repair. In addition, this technique eliminates the cost of anchors. Kummer and colleagues²⁵ confirmed with biomechanical testing that arthroscopic TO repair and double-row TOE repair are similar in strength, with a trend of less tendon displacement in the TO group.

Our study results support the hypothesis that arthroscopic TO repair provides significant cost savings over tear size–matched arthroscopic TOE repair. Implant cost was substantially higher for TOE repair than for TO repair. Mean (SD) total savings of $946.91 ($100.70) (P < .0001) can be realized performing TO rather than TOE repair. In the United States, where about 250,000 RCRs are performed each year, the use of TO repair would result in an annual savings of almost $250 million.⁶Operative time was analyzed as well. Running an operating room in the United States costs an estimated $62 per minute (range, $22-$133 per minute).²⁹ Much of this cost is indirect, unrelated to the surgery (eg, capital investment, personnel, insurance), and is being paid even when the operating room is not in use. Therefore, for the hospital’s bottom line, operative time savings are less important than direct cost savings (supplies, implants). However, operative time has more of an effect on the surgeon’s bottom line, and longer procedures reduce the number of surgeries that can be performed and billed. We found no significant difference in operative time between TO and TOE repairs. Critical evaluation revealed that operative time was 5.96 minutes shorter for TOE repairs, but this difference was not significant (P = .677).

Our study results showed no significant difference in clinical outcomes between TO and TOE repair patients. Both groups’ outcome scores improved. At all follow-ups, both groups’ VAS, SANE, and SST scores were significantly improved. Overall, this is the first study to validate the proposed cost benefit of arthroscopic TO repair and confirm no compromise in patient outcomes.

This study had limitations. First, it enrolled relatively few patients, particularly those with small tears. In addition, despite the fact that patients were matched on tear size and concomitant procedures, the groups differed in their biceps pathology treatments. Of the 13 TO patients who had biceps treatment, 12 underwent tenodesis (1 had tenotomy); in contrast, of the 10 TOE patients who had biceps treatment, only 2 underwent tenodesis (8 had tenotomy). The difference is explained by the consecutive course of this study and the increasing popularity of tenodesis over tenotomy. The TOE group underwent surgery before the TO group did, at a time when the involved surgeons were routinely performing tenotomy more than tenodesis. We did not include the costs of implants related to biceps treatment in our analysis, as our focus was on the implant cost of RCR. As for operative time, biceps tenodesis would be expected to extend surgery and potentially affect the comparison of operative times between the TO and TOE groups. However, despite the fact that 12 of the 13 TO patients underwent biceps tenodesis, there was no significant difference in overall operative time. Last, regarding the effect of biceps treatment on clinical outcomes, there are no data showing improved outcomes with tenodesis over tenotomy in the setting of RCR.

A final limitation is lack of data from longer term (>12 months) follow-up for all patients. Our analysis included cost and operative time data for all 42 enrolled patients, but our clinical outcome data represent only 74% of the patients enrolled. Eleven of the 42 patients were lost to follow-up at >12 months, and outcome scores could not be obtained, despite multiple attempts at contact (phone, mail, email). The study design and primary outcome variable focused on cost analysis rather than clinical outcomes. Nevertheless, our data support our hypothesis that there is no difference in clinical outcomes between TO and TOE repairs.

Conclusion

Arthroscopic TO-RCR provides significant cost savings over arthroscopic TOE-RCR without increasing operative time or compromising outcomes. Arthroscopic TO-RCR may have an important role in the evolving healthcare environment and its changing reimbursement models.

Am J Orthop. 2016;45(7):E415-E420. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

The amniotic membrane is a multilayer tissue forming the innermost layer of the amniotic sac that surrounds the developing fetus. It is comprised of 5 layers, from the inside out: a single layer of epithelial cells, a thick basement membrane, a compact layer, a fibroblast layer, and a spongy layer that abuts the surrounding chorion (Figure 1).¹

Amniotic epithelial cells are derived from the pluripotent epiblast at approximately day 8 of gestation. This is well before gastrulation occurs at days 15 to 17, considered the “tipping point” when pluripotent cells differentiate into ectoderm, mesoderm, and endoderm.³ These cells express Oct-4 and Nanog, 2 molecular markers that are indicative of pluripotency.³ Two cell types have been identified in amniotic tissues that possess stem cell-like characteristics: human amniotic epithelial cells and human amniotic mesenchymal stromal cells.⁴ Both of these cell types have demonstrated the ability to differentiate into various cell lineages, including endothelial cells, adipocytes, myogenic cells, neurogenic cells, chondrocytes, tenocytes, and osteogenic cells.^5-7 These previously reported findings indicate that amniotic cells and tissue have the capability to generate mesenchymal tissues.

FDA Classification and Available Forms

The US Food and Drug Administration (FDA) classifies amnion as an allograft tissue under Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) 361. To meet criteria, the tissue needs to be minimally manipulated. It is to be for homologous use and cannot be combined with other cells or tissues. There can be no systemic effect or dependence on the metabolic activity of living cells to achieve its primary function. The tissue has to have a localized effect in vivo. Therefore, amnion allograft tissue can be commercialized, provided it is not marketed as a stem cell product or to contain viable cells.

Amniotic tissue is commercially available in several forms.

Safety

Amniotic tissue has been used for over 100 years in burn, ophthalmology, and chronic wound patients with favorable outcomes and no adverse effects reported in the literature. Unlike embryonic stem cells, which may be tumorigenic,⁸ amniotic cells do not possess any known tumorigenicity.⁹ In one study, 50 immunodeficient mice were injected with 1 to 2 million amniotic epithelial cells and observed for a maximum of 516 days with no tumorigenicity observed in any of the animals.¹⁰ In another study, amniotic epithelial cells were implanted into the forearms of healthy volunteers and no immunologic response was observed in any of the recipients.¹¹ Furthermore, viable amniotic cells were recovered via biopsy 7 weeks following transplantation, demonstrating viability of the transplanted cells.¹¹ The lack of tumorigenicity and immunologic response in hosts is due in part to the fact that amniotic cells do not express human leukocyte antigen class II antigens and only express class I antigens in small amounts.³

Advantages of Amnion Tissue

Amniotic tissue is readily available, as it is often discarded after childbirth. The use of this tissue poses no added risk to the fetus or mother, eliminating the ethical concerns associated with obtaining embryonic stem cells. Amniotic tissue is comprised of an extracellular matrix, which acts as a natural scaffold for cellular attachment and structural support for cells as well as collagen types I, III, IV, V, and VI, hyaluronic acid, and a host of growth factors.¹² In addition, it possesses antimicrobial properties, including beta-defensins.¹³

Amniotic tissue has been shown to exert an anti-inflammatory effect by inhibiting the inflammatory cascade. Specifically, it has been shown to inhibit cytokines such as tumor necrosis factor-alpha in the presence of dendritic cells,¹⁴ as well as inhibiting transforming growth factor-beta, interleukin-8, and fibroblast proliferation.¹⁵ These findings indicate that amniotic tissue has the ability to dampen the “cytokine storm” that occurs after an injury in an adult, which would lead to beneficial impacts on healing and scar formation in patients.¹⁶

Basic Science and Animal Studies

Several studies have demonstrated promising outcomes for orthopedic applications in vitro. A comparison of osteogenic potential found that amniotic fluid-derived cells were able to produce approximately 5 times more mineralized matrix than bone marrow-derived mesenchymal stem cells.¹⁷ More recently, Si and colleagues¹⁸ compared the osteogenic potential of human amniotic epithelial cells, amniotic cells, and human bone marrow-derived mesenchymal stem cells. They found that all 3 cell lines were osteogenic, though the amniotic epithelial cells had better immunomodulatory properties and marginally less osteogenic potential than the other 2 cell types. Furthermore, several in vivo animal studies have demonstrated the ability of human amniotic cells to stimulate bone growth in rats,^19,20 rabbits,²¹ and sheep.²²

Amniotic tissue also possesses potential for chondrogenesis. Cryopreserved human amniotic membrane cells used for in vitro human osteoarthritis tissue scaffolds did not differentiate in culture, and they integrated and repaired damaged articular cartilage.²³ Various in vitro^24,25 and animal in vivo^26,27 studies have reported similar supportive findings. Kunisaki and colleagues²⁸ used sheep amniotic fluid mesenchymal stem cells to reconstruct lamb tracheal cartilage in utero, concluding that cells obtained from the amniotic fluid possess chondrogenic capabilities. Further in utero lamb studies of cartilage artificial defects, given 7 days to settle before adding a hypocellular matrix as a scaffold, showed chondrocyte density and cell architecture was restored at the defect site after 28 days without the formation of an inflammatory response or scar tissue.²⁹

Amniotic tissue has had similar success in tendon repair studies in vivo.^9,30,31 Barboni and colleagues³² implanted amniotic epithelial cells (AECs) into artificially created sheep Achilles tendon defects in situ, inducing superior structural and mechanical recovery in the defects at a faster rate compared to controls not receiving AECs. Healing via AECs started at the healthy tissue around the borders of the defect and progressed centrally, suggesting recruitment of native progenitor cells to the lesion.³² Kueckelhaus and colleagues³³ investigated the role of amnion-derived cellular cytokine solution in the healing of transections of rat Achilles tendons, reporting improved mechanical properties of healing tendons at early time points compared to controls. Beredjiklian and colleagues³⁴ compared the healing of transected extensor tendons of pregnant ewes and of their fetus in utero, reporting a reparative form of healing with scar formation in adult subjects and regenerative form of healing without scar formation or inflammation in fetal subjects.

Amniotic tissue has properties that prevent adhesion formation around tendons following injury and reconstruction.³⁵ Ozgenel³⁶ investigated the effects of hyaluronic acid and amniotic membrane alone and in combination on the presence of adhesions and the rate of healing following chicken flexor tendon repair. The study found amniotic membrane wrapped around the repaired tendon was superior in preventing adhesion formation. Kim and colleagues³⁷ report a similar reduction in fibrosis and adhesion following application of a human amniotic membrane wrap to rabbit ulnar neurorrhaphy sites.

This barrier function of amniotic tissue has also been investigated in the prevention of surgical scarring and peridural fibrosis in animal models following spinal discectomy. A study in canine models showed a reduction of scarring following the application of cross-linked amniotic membrane compared to freeze dried amniotic membrane.³⁸ Similar reductions in scarring in rat models with the application of freeze-dried amniotic membrane compared to negative controls have been reported.³⁹

Human Studies

A randomized trial investigated the outcomes of prenatal vs postnatal repair of myelomeningocele in humans, finding a reduced need for implanted shunts and improved functional outcomes at 30 months of life in the prenatal intervention group compared to the postnatal group.⁴⁰ This study was concluded early due to the efficacy of prenatal surgery and the benefit of nervous system repair in utero in the presence of amniotic growth factors.

Vines and colleagues⁴¹ performed a 6-patient feasibility study using amnion injections to treat symptomatic knee osteoarthritis. Each patient received a single intra-articular cryopreserved amniotic suspension allograft (ASA) injection and was followed for 1 year. No adverse outcomes were reported, with the only abnormal finding being a small increase in serum immunoglobulin G and immunoglobulin E levels. Intra-articular ASA injection was found to be safe, but a large-scale trial investigating symptomatic relief was recommended.⁴¹

Most of the human studies using amnion pertain to foot and ankle surgery. Its use as a treatment for diabetic foot ulcers and recalcitrant plantar fasciitis was one of the early-recognized successes.^42-45 Zelen and colleagues⁴⁶ investigated the applications of injectable micronized dehydrated human amniotic/chorionic membrane as an alternative to surgical intervention in the treatment of refractory plantar fasciitis. This prospective, randomized trial with 45 patients showed significant improvement in plantar fasciitis symptoms at 8 weeks compared to controls (saline injections). A similar study compared the use of cryopreserved human amniotic membrane (c-hAM) injections to corticosteroid injections in plantar fasciitis patients.⁴⁷ The results indicated that c-hAM is safe and comparable to corticosteroids, with the authors noting that pain improvement was greatest in patients receiving 2 injections of c-hAM at 18 weeks.

Tendon wrapping, in which the amniotic membrane is laid over a tendon repair, has been reported with success. Amniotic membrane is superior to collagen for tendon wrapping as it actively contributes to healing while minimizing adhesions, which collagen alone cannot do.⁴⁸ The membrane serves as a protective sheath around repaired tendons with anti-inflammatory, anti-adhesive, immunomodulatory, and antimicrobial benefits. A 124-patient study demonstrated the safety of using amnion in this manner, and the authors reported a decreased rate of complication compared to previously published data.⁴⁹ Another study of 14 patients undergoing foot and ankle surgery with tendon wrapping reported clinical improvement with reduced pain and greater functional outcomes postoperatively compared to preoperative measurements.⁵⁰

Conclusion

Amniotic membrane-derived tissues are safe and non-tumorigenic, producing an abundance of growth factors that have shown promise as tissue scaffolds and as aids in the regeneration of human bone and soft tissues. Amnion applications in orthopedic surgery may be numerous, but development is ongoing. Given the vast array of in vitro and in vivo animal data supporting the benefits of amnion in tissue regeneration, orthopedic surgeons and researchers should place emphasis on conducting clinical studies to validate the safety and efficacy of amniotic cells in the treatment of orthopedic conditions.

Am J Orthop. 2016;45(7):E421-E425. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Injury of the anterior cruciate ligament (ACL) is very common with over 200,000 annual injuries in the United Status.^1,2 There is a general consensus that these injuries should not be treated conservatively in patients that are younger, or who wish to remain active.^3,4 Reconstructive surgery is currently the preferred treatment in these patients, and anatomic single-bundle reconstruction with autografts is considered the gold standard.^5,6

Reconstruction of the ACL is, however, not a perfect treatment. Following single-bundle autograft reconstruction, revision rates of 3% to 8%,^6-9 contralateral injury rates of 3% to 8%,^10,11 and infection rates of 0.5% to 3%^7,12,13 have been reported. Furthermore, due to the invasive nature of graft harvesting and the surgical procedure, 10% to 25% of the patients are not satisfied following ACL reconstruction.^14,15 This can often be explained by common complaints, such as anterior knee pain (13%-43%), kneeling pain (12%-54%), quadriceps muscle atrophy (20%-30%),^16,17 and loss of range of motion (ROM) (12%-23%).^7,9,18,19 Furthermore, as a result of the invasive nature of reconstructive surgery, revisions can be difficult due to complications, such as tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22 This can lead to inferior outcomes and higher rates (13%) of revision surgery compared to primary reconstruction.^23-26 Finally, reconstructive surgery does not restore native kinematics of the ACL,^27-29 which may partially explain why reconstructive surgery has not been shown to prevent osteoarthritis.^28-31

Over the past decades, there has been an increasing interest in the preservation of the ACL in an attempt to ameliorate these issues.^32-37 Ligament preservation focuses on preserving the native tissues and biology, while minimizing the surgical morbidity to the patients.

Some authors have recently reported on arthroscopic primary repair of proximal ACL tears in which the ligament is reattached onto the femoral wall using modern-day suture anchor technology.^32,38 Others have augmented this repair technique with an internal brace^39,40 or with a synthetic device.^33,41 When performing primary repair, it is believed that proprioception is maintained,^42-44 while experimental studies have suggested that primary repair also restores the native kinematics,⁴⁵ and may prevent osteoarthritis.⁴⁶ Furthermore, primary repair is a conservative approach in that no grafts need to be harvested, no tunnels need to be drilled, and revision surgery, if necessary, is more analogous to primary reconstructions.³²In patients with partial tears, some surgeons have advocated preserving the anteromedial (AM) or posterolateral (PL) bundle and performing selective single-bundle augmentation.^34,35 In addition, several authors have used remnant tensioning^36,47 or remnant preservation^37,48 in combination with reconstructive surgery in order to benefit from the biological characteristics of the remnant. These techniques lead to better proprioceptive function,^44,49,50 vascularization and ligamentization of the graft,^50-52 provide an optical guide for anatomic tunnel placement,⁵³ and decrease the incidence of tunnel widening.^54,55The feasibility and applicability of these surgical techniques mainly depends on the tear type and tissue quality of the torn ligament. In this article we (I) discuss the history of ACL preservation, (II) discuss how modern advances alter the risk-benefit ratio for ACL preservation, and (III) propose a treatment algorithm for ACL injuries that is based on tear location and tissue quality.

History of ACL Preservation

The history of the surgical treatment of ACL injuries started in 1895 when Robson⁵⁶ treated a 41-year-old male who tore both cruciate ligaments from the femoral wall. Performing primary repair with catgut ligatures, both cruciate ligaments were preserved and the patients had resolution of pain symptoms and full function at 6-year follow-up. Over the following decades, Palmer^57,58 and O’Donoghue^59,60 further popularized open primary repair for the treatment of ACL injuries, and this technique was the most commonly performed treatment in the 1970s and early 1980s.^61-65 The initial short-term results of primary repair were excellent,^61,62 but Feagin and Curl⁶⁶ were the first to note that the results deteriorated at mid-term follow-up. Despite improvements in the surgical technique of repairing the ACL, such as the usage of nonabsorbable sutures and directly tying the sutures over bone,^63,67 the results remained disappointing at longer-term follow-up.^68-70

In response to these disappointing results, surgeons sought to improve the surgical treatment by either augmenting the primary repair with a semitendinosus, a patella tendon graft or an augmentation device,^71-74 or by performing primary reconstruction.^75-77 At the end of the 1980s and early 1990s, several randomized and prospective clinical trials were performed in order to compare the outcomes of these techniques.^74,78-82 Many studies showed that results of augmented repair were more reliable when compared to primary repair, which led to the abandonment of primary repair in favor of augmented repair, and eventually primary reconstruction.⁶⁵

The Important Role of Tear Location in Ligament Preservation

When taking a closer look at the outcomes of primary repair and augmented repair, it seems that the results of these preservation techniques were not as disappointing as was suggested. This can be explained, in large part, by the fact that the important roles of tear location and tissue quality were not widely recognized.

Sherman and colleagues⁷⁰ reported in 1991 their mid-term results of open primary repair. Similar to others, they noted a deterioration of their results at mid-term follow-up. However, they uniquely performed an extensive subgroup analysis in order to find an explanation for this. In their study, considered a landmark paper on primary repair,^65,70 they concluded that, “poor tissue quality is typical for midsubstance tears and that a repair of these injuries will predictably fail while type I tears (proximal), with better tissue quality, show a definite trend towards better results.”⁷⁰ With these findings, they confirmed the findings of others that had recognized a trend of better outcomes with proximal tears.^64,67,83-85

A majority of the historical studies that were published before 1991 had not considered the role of tear location and tissue quality on outcomes of open primary repair. This was also true for the aforementioned randomized studies that compared primary repair with augmented repair and primary reconstruction. Because these studies randomized patients and did not take tear location into account, it can be expected that patients with midsubstance tears were included in the cohorts of primary repair and the outcomes of these studies were therefore confounded.^74,78-82 If these studies would have been aware of the role that tear location plays on primary repair outcomes, different outcomes may have been found and different conclusions on the optimal treatment for different tear types may have been drawn.⁸⁶

Open Primary ACL Repair Outcomes Stratified by Tear Location

When reviewing the literature of open primary repair outcomes stratified by tear location, it is noted that multiple studies reported excellent outcomes following primary repair of proximal ACL tears.^{73,83,84,87-90} Weaver and colleagues⁶⁴ were among the first to stratify their results by tear location, and they found that more patients with proximal tears (52 of 66; 79%) were satisfied after the procedure when compared to patients with midsubstance tears (3 of 13; 23%) at 3.5-year follow-up. They concluded that, “selection can be made with some predictability of the type of injury to the ligament as to which patients will do better.”⁶⁴ Kühne and colleagues⁸⁹ reported the outcomes of 75 patients with proximal tears treated with open primary repair and noted no failures, negative pivot shift in 88% of patients, stable or nearly stable Lachman test in 87% of patients, and 89% return to sports rate at 4-year follow-up. Raunest and colleagues⁹¹ reported a negative pivot shift and negative anterior drawer test in 84%, return to sports in 71%, and satisfaction in 75% of 51 patients that underwent open primary repair of proximal tears at 3.5-year follow-up.

Interestingly, and in contrast to the findings of Feagin and Curl,⁶⁶ no deterioration of the outcomes at mid-term follow-up was noted in patients with proximal tears. Genelin and colleagues⁸⁸ reported their results of 42 patients with proximal tears treated with open primary repair at 5- to 7-year follow-up. They found a negative pivot shift in 81%, stable or nearly stable Lachman test in 81%, and patient satisfaction in 86% of patients. Similarly, Bräm and colleagues⁸⁷ found good results at mid-term follow-up with a good-excellent Lysholm score in 79%, return to a similar level of sports in 76%, stable or nearly stable Lachman test in 91%, and anterior drawer test in 94% of patients, along with an 88% satisfaction rate and 7% failure rate in patients who underwent open primary repair of proximal tears.

On the contrary, when the outcomes of studies that performed open primary repair in mainly, or only, patients with midsubstance tears are reviewed, significantly inferior results are found. Frank and colleagues⁹² reported outcomes in 42 patients with midsubstance tears at 4-year follow-up. They reported that 56% had a stable or nearly stable anterior drawer test, 78% had a positive pivot shift, and that only 61% were satisfied with the procedure. Odensten and colleagues⁷⁸ reported outcomes of open primary repair in a subgroup of 22 patients with midsubstance tears at 1.5-year follow-up, and noted a 14% failure rate.

When reviewing the mid-term results in patients with midsubstance tears, it seems that there was more deterioration in outcomes.^69,70 Firstly, the aforementioned study by Sherman and colleagues⁷⁰ showed poor results in the patients with (type IV) midsubstance tears at mid-term follow-up. Furthermore, Kaplan and colleagues⁶⁹ reported the mid-term outcomes of 70 patients, of which 56 patients had midsubstance tears. After having reported good outcomes at short-term follow-up,^63,67 they noted that 42% of patients had >3 mm anteroposterior stability when compared to the contralateral leg, only a 62% return to sport rate, and a 17% failure rate. They concluded that, “Although … primary repair of the anterior cruciate may work in some patients, it is an unpredictable operative procedure.”

These studies showed that the outcomes of open primary repair were significantly better in patients with proximal ACL tears and sufficient tissue quality when compared to midsubstance tears. This suggests that open primary ACL repair may have been prematurely abandoned as a treatment option for patients with proximal tears.

Augmented ACL Repair

There were several reasons why augmented repair became the preferred treatment in the early and mid 1990s. First of all, the results of augmented repair were more consistent compared to primary repair in the aforementioned randomized and prospective studies,^74,78-82 which is not surprising given the fact that the role of tear location was not widely recognized at the time. Secondly, in the 1970s and early 1980s, patients were treated postoperatively in a cast for 6 weeks, which led to problems, such as loss of ROM, pain, and decreased function.^93,94 At the end of the1980s and 1990s, the focus shifted from prolonged joint immobilization towards early postoperative ROM.^95-97 Since many authors believed that primary repair of the ACL was not strong enough to tolerate early mobilization, an augmentation was added to the technique in order to fortify the repair and enable early ROM.⁹⁸

Interestingly, augmented repair, which is essentially a combination of primary ACL repair and ACL reconstruction, was mainly performed in the 1990s and many surgeons did recognize the role of tear location in this treatment at this point.^73,98-103 In these years, the treatment algorithm consisted of augmented ACL repair in patients with proximal tears in the acute setting and ACL reconstruction in patients with midsubstance or chronic tears. Several different augmentation techniques were used to reinforce the primary repair in these years including autograft tissues (semitendinosus tendon,^102-104 patellar tendon,¹⁰⁰ or iliotibial band [ITB]¹⁰⁵) synthetic materials (polydioxanone [PDS],^101,102,106 carbon fibre,⁷⁴ and polyester [Trevira]⁹⁷), augmentation devices (Kennedy Ligament Augmentation Device [LAD]^98-100) and extra-articular augmentations.⁷³

When reviewing the outcomes of augmented repair of the ACL, good to excellent results can be found in studies that used this technique in patients with proximal tears.^73,98-106 Kdolsky and colleagues⁹⁸ were in one of the first groups that reported their results of augmented repair in only patients with proximal tears. In 1993, they reported their mid-term outcomes (5 to 8 years) in 66 patients who underwent primary repair and augmentation with the Kennedy LAD and found that 97% of patients had stable knees (<3 mm on KT-1000 examination), 98% had a negative pivot shift, and 76% returned to previous level of sports. However, often-reported problems with the augmentation devices were found in this study with rupture of the device (12%) and decreased ROM (14%).⁹⁸ In 1995, Grøntvedt and Engebretsen¹⁰⁰ compared augmentation with the Kennedy LAD to patellar tendon augmentation in a randomized study of patients with acute proximal tears. They noted that 50% of the patients in the Kennedy LAD group had a positive pivot shift compared to 23% in the patellar tendon group. Furthermore, they found KT-1000 leg differences of <3 mm in 92% of the patellar tendon group and 54% of the Kennedy LAD group. Because the authors found significant differences between both groups at 1- and 2-year follow-up, they stopped the clinical trial.

Several authors in the following years reported good results of augmented repair using autograft tissues. Natri and colleagues¹⁰⁵ reported the outcomes of 72 patients treated with primary repair of proximal tears augmented with the ITB at 3.5-year follow-up. They found 89% negative pivot shift rate, 93% stable or nearly stable Lachman test, 99% stable or nearly stable anterior drawer test, 79% satisfaction rate, and 91% return to previous level of sports rate. Krueger-Franke and colleagues¹⁰⁴ reported the outcomes of primary repair of proximal tears with augmentation using the semitendinosus tendon. In a retrospective study of 76 patients, they noted that 96% of patients had a negative pivot shift, 75% of patients had stable or nearly stable Lachman test, 93% were satisfied with the procedure, a mean Lysholm score of 92, a Tegner score that only decreased from 7.2 to 7.1, and KT-1000 testing with 78% <4 mm leg difference with the contralateral leg. The authors concluded that patients with femoral ruptures could be treated with augmented repair when performed in the acute setting. As this study was published in 1998, they stated that magnetic resonance imaging and arthroscopy could be helpful in identifying the tear location.

Final Abandonment of ACL Preservation

Reviewing these outcomes raises the question as to why these techniques were ultimately abandoned in the treatment algorithm of proximal ACL injuries, especially given the aforementioned advantages of ACL preservation. One of the possible answers can be found in a landmark study on ACL reconstruction and rehabilitation published by Shelbourne and colleagues¹⁰⁷ in 1991. At that time, arthrofibrosis and knee stiffness were frequently reported problems following ACL surgery, which could partially be explained by the standard conservative rehabilitation using postoperative joint immobilization.^67,70,80,88

Shelbourne and colleagues¹⁰⁷ aimed to assess the cause of arthrofibrosis and knee stiffness, and divided the patients into groups by number of days between injury and surgery (<7, 7 to 21 days, and >21 days between injury and surgery). Furthermore, patients within these groups underwent either a conventional or accelerated rehabilitation program. The authors not only found that patients undergoing accelerated rehabilitation had less arthrofibrosis, but they also noted that less arthrofibrosis was seen when surgery was delayed. These findings, however, contrasted with the general perception that the ACL should be repaired in the first 3 weeks postinjury to ensure optimal tissue quality with an augmented approach. As a result, the treatment of ACL injuries shifted towards ACL reconstruction after these findings. Krueger-Franke and colleagues¹⁰⁴ commented on the trend after the study of Shelbourne and colleagues:¹⁰⁷ “Less consideration has been given to the importance of the proprioceptive receptors in the tibial remnants of the torn ACL and the value of their preservation as part of a primary reconstruction.”

In addition to the trend away from an augmented repair approach due to the novel understanding of the importance of early mobilization, some discussion should focus on the technical limitations of arthroscopy at that time. While arthroscopy had been around for several decades, fluid management and arthroscopic instrumentation was slow to develop. All of the repair and augmentation techniques previously discussed had been performed via an open arthrotomy. Arthroscopic technologies of the time were not refined enough to enable surgeons to perform such complex, intra-articular techniques that would enable suturing of the ligament remnant. In this regard, arthroscopic ACL reconstruction was a much simpler technique to accomplish, and this also likely contributed to the final abandonment of the ligament preservation approach.

Role for ACL Preservation with Modern Advances

As stated in the introduction, there has been a recent resurgence of interest in preservation of the native ligament.^32-37 With the passage of time, many technologic advances have been made, which has allowed surgeons to reconsider the concept of ligament preservation.

First of all, appropriate patient selection was not applied historically, as the critical factors of tear location and tissue quality were not recognized in the era of open primary repair. In modern days, however, advances such as MRI have been developed, which can give the surgeon an idea of the status, and tear type of the ACL pre-operatively.¹⁰⁸ This may help the orthopaedic surgeon to plan the surgery and make an assessment as to whether ACL preservation is possible. Secondly, in the historic literature the postoperative regimen consisted of casting for 5 or 6 weeks,^67,70,80,88 while the focus later shifted towards early ROM.^95-97Modern day ACL rehabilitation focuses on immediate ROM to avoid the complications stiffness, pain and decreased function that plagued the outcomes when immobilization was used.^93,94 Thirdly, historically small tunnels were drilled with primary repair and sutures had to be tied over bone,^57,67 whereas currently suture anchors are available that prevent the need for tunnel drilling and enable direct suture tensioning.^32,38 Finally, and most importantly, in the historic literature patients were treated with an invasive arthrotomy technique, while modern day arthroscopic techniques readily enable the surgeon to effectively suture the remnant arthroscopically. Interestingly, in 2005, in their 20-year follow-up of primary repair surgeries, Strand and colleagues¹⁰⁹ stated, “if the same results could be accomplished by a smaller, arthroscopic procedure, primary repair might reduce the number of patients needing later reconstructions with small ‘costs’ in the way of risk and inconvenience for the patients. We therefore believe that further research and development of methods for closed (arthroscopic) repair are justified.”

Altered Risk-Benefit Ratio

Historically, the treatments of open primary repair and open ACL reconstruction were both invasive surgeries with an arthrotomy, drilling of bone tunnels, and postoperative joint immobilization for 4 to 6 weeks. However, with the modern-day advances, the risk-benefit ratio of both treatments has changed, as Strand and colleagues¹⁰⁹ had already suggested. Although ACL reconstruction can be performed arthroscopically, it remains an invasive procedure, in which tunnels are drilled, patellar tendons or hamstring tendons are harvested, and complications, such as knee pain and quadriceps atrophy, are common. The surgery of primary ACL repair, however, has benefited significantly from the modern developments.^32,38 Primary ACL repair can now be performed arthroscopically, and by using suture anchors no tunnels need to be drilled and the remnant can be tensioned directly. An additional benefit of the use of suture anchors is that revision surgery of a failed primary repair is analogous to primary reconstruction, whereas revision surgery of a failed ACL reconstruction can be problematic due to tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22

Reviewing the differences between arthroscopic primary ACL repair and ACL reconstruction, it becomes clear that primary repair has benefited significantly from the modern advances and that the risk-benefit ratio for primary repair has been altered. This means that patients with proximal tears can be treated with a relatively straight forward, minimally invasive surgery, which has been shown to be effective in 85% to 90% of patients.^32,38

Treatment Algorithm Based on Tear Location

Since 2008, in the practice of the senior author (GSD), the surgical treatment algorithm for ACL injuries is completely based on the tear location and tissue quality of the ligament.^110,111 To describe the different tear types, we use the modified Sherman classification in which we extended his classification towards the tibial side whereas Sherman and colleagues⁷⁰ only described the femoral side of the tears (Figures A-F, Table).

Type I Tears: Primary Repair

Type I tears are soft tissue avulsion type tears that can be easily treated with arthroscopic primary repair.¹⁰⁷ The length of the distal remnant has to be at least 90% and the tissue quality has to be good to excellent in order to approximate the remnant towards the femoral wall (Table).¹¹² The incidence of type I tears was 26% in the study of Sherman and colleagues,⁷⁰ although recent studies showed a lower incidence (6% to 10%) in a larger population.^32,38 Certainly, individual practices will see different percentages of type I tears based upon the mix of injury mechanisms they see most frequently. Over the last 2 years, with the recognition of the importance of tear type and tissue quality, there has been a renewed interest in arthroscopic primary ACL repair.^32,38

DiFelice and colleagues³² were the first to arthroscopically perform primary repair of the ACL in proximal tears using suture anchors. They reported the outcomes of the first 11 consecutive patients that underwent primary repair in a previously described technique.¹¹³ At mean 3.5-year follow-up, they noted only 1 failure (9%) due to re-injury; mean Lysholm score of 93.2; mean modified Cincinnati score of 91.5; pre- and postoperative Tegner score of 7.3 and 6.9, respectively; SANE score of 91.8; and subjective International Knee Documentation Committee (IKDC) score of 86.4. Of the patients with an intact repair, 9 patients had an objective IKDC rating A and 1 patient had B and all patients had KT-1000 leg differences of <3 mm with the contralateral side (three patients were not available for KT-1000 testing). The authors concluded that arthroscopic primary ACL repair could achieve short-term clinical success in a selected group of patients with proximal avulsion tears and excellent tissue quality. They further noted that mid-term outcomes are necessary given that the results of open primary repair deteriorated at longer-term follow-up in the historical literature. Recently, the senior author (GSD) has added an Internal Brace (Arthrex) to the primary repair with the goal of protecting the ligament in the first weeks to further promote healing of the ligament.^39,40,114

More recently, Achtnich and colleagues³⁸ compared the treatment of arthroscopic primary ACL repair with primary ACL reconstruction in 41 patients with type I tears at 2.3-years follow-up. Twenty-one patients consented for primary repair while 20 patients declined this procedure and underwent primary reconstruction. They noted no significant differences in Lachman test, pivot shift test, objective IKDC score, and KT-1000 scores. Although not significant, the clinical failure rate in the primary repair group (15%) was higher than the reconstruction group (0%). Interestingly, despite the higher failure rate in the repair group, the authors concluded that primary ACL repair is recommended in a carefully selected group of patients with type I tears and excellent tissue quality, which can likely be explained by the differences in the risk-benefit ratio between both procedures.

Over the last decade, the research group led by Murray^46,115,116 has performed experimental research on primary repair with a biological scaffold and reported many interesting findings that could be extrapolated to primary ACL repair. First of all, they compared bioenhanced primary repair with bioenhanced primary reconstruction in 64 Yucutan pigs and noted that there was significantly less macroscopic cartilage damage in the primary repair group at 1-year follow-up.⁴⁶ They concluded that bioenhanced ACL repair may provide a new, less invasive treatment option that reduces cartilage damage following joint injury. This may suggest that primary repair may have a lower incidence of osteoarthritis when compared to ACL reconstruction, which is interesting as osteoarthritis is very common after ACL reconstruction. Further research in this area is certainly warranted.

In another study they compared bioenhanced primary repair in juvenile, adolescent and mature Yucutan pigs and noted that functional healing depended on the level of skeletal maturity with immature animals having a more productive healing response.¹¹⁶ This indicates that primary repair might be a good treatment option in skeletally immature patients, especially since reconstruction increases the risk of premature closure of the epiphysis^117,118 and delaying treatment increases the risk of meniscus injury.¹¹⁹ Interestingly, a recent meta-analysis showed indeed that the risk of epiphysis closure was lower in primary repair when compared to ACL reconstruction and the rupture rate was also lower.¹¹⁸ Primary repair may be a good treatment option in children as the procedure has all the attributes that should be applicable to children: it is minimally morbid, tissue sparing, and it is a conservative approach that does not burn any surgical bridges for future reconstructive surgery if necessary.

Finally, the research group of Murray¹¹⁵ assessed the effect of surgical delay of primary repair following injury in Yucutan pigs and noted that better biomechanical outcomes were noted after delaying surgery for 2 weeks when compared to 6 weeks. This suggests that primary repair should preferably be performed in the acute setting, which has also been shown in historical studies since the ligament in the acute setting has optimal tissue quality and the ligament is less likely to be retracted or reabsorbed.^59,60,115

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the tear locations of the AM and PL bundle are not at the same location and Zantop and colleagues¹²⁰ reported in an arthroscopic study that this could be as frequent as in 30% of all complete tears. In some of these tears, one of the bundles can be avulsed of the femoral wall (type I tear) while the other bundle is not directly repairable (non-type I tear). In these cases, the senior author (GSD) will repair the type I tear bundle, whereas a hamstring augmentation is placed at the location of the other bundle. When reviewing the literature, a combination of primary repair of one bundle and reconstruction of the second bundle has not been described before. However, over the last decade several surgeons have performed augmentation of one bundle in the setting of partial tears.^{34,35,121-124}

Buda and colleagues³⁴ were the first to perform selective AM or PL bundle reconstruction in the setting of partial tears.³⁴ At 5-year follow-up, they reported no reruptures and only 1 patient with an IKDC C-score, although reoperation was necessary in 4 out of 47 patients (9%). Following this publication, many others reported on selective bundle reconstruction.^35,121-124 However, with partial tears, the knee is often stable and a selective augmentation technique is utilized to prevent complete rupture of the ligament. The application of this technique is essentially different from reconstruction for complete ACL tears in which the knee is unstable, there is a giving way sensation and patients have problems participating in sports.

Type II Tears: Augmented Repair

Type II tears often have good or excellent tissue quality and can be pulled up towards the femoral footprint, but are too short to be firmly attached. Sherman and colleagues⁷⁰ reported that approximately 22% patients had a type II tear, which corresponds to a tear located in the proximal part of the ligament. With this technique, multiple suture passes are used to stitch the remnant and, in addition, a smaller hamstring autograft or allograft is passed through the middle of the tibial remnant. A suture button is used proximally for the graft, and the tensioning repair sutures through the remnant are also passed through the suture button. The suture button is passed through the femoral tunnel and flipped so that the graft is proximally fixed. Then, the repair sutures of the remnant are tensioned, and the ligament is pulled towards the femoral wall as a sleeve around the graft. When the ligament is approximated to the femoral wall, the sutures are tied over the suture button. The graft is then tensioned distally to complete the augmented repair.

In the recent literature, the technique of augmentation of a primary repair using autograft tissue has not been reported. However, augmented repair using an internal brace^39,40 or augmentation devices^33,41 have been recently performed. MacKay and colleagues³⁹ reported good outcomes of arthroscopic primary repair of proximal tears using an internal brace. Eggli and colleagues³³ reported the results of the first 10 patients treated with ACL preservation using primary repair of the ligament with the addition of a dynamic screw-spring mechanism. The authors reported good preliminary results with one failure (10%) and good objective and subjective outcomes. In a next study, they reported the outcomes of 278 patients and although they reported good clinical outcomes and a revision rate of 4%, the reoperation rate for removal of the screw-spring mechanism was high (24%).⁴¹ This is not surprising when reviewing the historical literature in which high complication rates of the augmentation devices were reported.^99,100 We were unable to identify any other studies reporting surgical techniques of augmenting primary repair in the literature.

Type III Tears: Reconstruction With Remnant Tensioning

In patients with type III tears, the ligament cannot be approximated to the wall and reconstruction is necessary in order to restore knee stability. However, in these cases the ligament has sufficient length (25%-75%) and can be tensioned along or around the graft. Preservation of the ligament remnant has several (theoretical) advantages, such as better proprioceptive function,^42,49,50 vascularization and ligamentization of the graft,^50-52 an optical guide for anatomic tunnel placement,⁵³ and a decreased incidence of tunnel widening.^54,55 Furthermore, tensioning of the remnant is thought to lower the risk of cyclops lesions when compared to remnant preservation.¹²⁵ Although the difference between augmented repair and remnant tensioning seems small, the purpose of surgery is different. With augmented repair, the ligament can be approximated close to the femoral wall and the goal of surgery is to use the healing capacity that the ACL has in the proximal part of the ligament,¹²⁶ while with remnant tensioning the goal is only to benefit from some of the aforementioned advantages. Ahn and colleagues³⁶ were the first to perform this technique and stated, “Our concept is that the remnant tissue has only an additive effect.” Furthermore, with augmented repair multiple sutures are passed through the AM and PL bundle in order to sufficiently approximate the ligament to the femoral wall, while with the remnant tensioning technique generally one or a few sutures or lasso loop are passed through the proximal part to tension the ligament, prevent sagging of the remnant, and decrease the risk of cyclops lesions.^127,128

Several authors have recently performed remnant tensioning during ACL.^{36,47,125-127} Ahn and colleagues⁴⁷ reported excellent objective and subjective outcomes following this procedure and found that with re-arthroscopy nearly all patients had fair synovialization of the graft. Others have reported similarly good outcomes of these techniques.^125,129,130 However, studies comparing this treatment with normal ACL reconstruction and assessing outcomes, failure rates and proprioception are lacking.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some patients the ligament is torn distally or the tissue quality is not optimal. In these patients, the remnant can be debrided to the part of good tissue quality in order to preserve the biology and minimize the risk for cyclops lesions. A standard reconstruction needs to be performed to restore the instability, but by preserving the remnant, advantages, such as proprioception,^44,49,50 graft vascularization,^50-52 an optical guide for tibial tunnel placement,⁵³ and a decreased incidence of tunnel widening^54,55 can be expected.

Lee and colleagues³⁷ presented the tibial remnant technique in which standard reconstruction was performed, and the tibial tunnel was drilled through the center of the remnant. In a later study, they compared remnant preservation with a remnant of <20% of the total ACL length with >20% of the length and found that proprioception was better with more remnant volume.⁴⁸ Similarly, Muneta and colleagues¹³¹ assessed the role of remnant length and found that remnant length is positively correlated with better stability measured on KT-1000 anteroposterior stability.

Several studies compared ACL reconstruction with remnant preservation vs conventional ACL reconstruction.^52,54,129 Takazawa and colleagues⁵² performed a retrospective study of 183 patients and found that patients in the remnant preservation group had significantly better KT-2000 stability, while they also reported a significantly lower graft rupture rate in this group (1.1% vs 7.1%) at 2-year follow-up. Hong and colleagues¹²⁹ performed a randomized clinical trial of 80 patients and did not find these differences, although there was a trend towards higher Lysholm scores in the remnant preservation group. Finally, Zhang and colleagues⁵⁴ performed a randomized clinical trial and found a lower incidence and amount of tibial tunnel widening in the preserving-remnant group when compared to the removing-remnant group. These studies show that there is likely a role for remnant preservation.

Type V Tears: Primary Repair

In some patients, the ligament is torn in the distal 10% of the ligament, which can occur as a distal avulsion tear or as a distal bony avulsion fracture.¹³² Bony avulsion fractures are most commonly seen in children whereas true distal soft tissue avulsion tears are very rare.¹³²

Treatments of these tear types include antegrade screw fixation, pullout sutures or the use of suture anchors in case of bony avulsion fractures and pullout sutures with tying over a bony bridge or ligament button in case of soft tissue avulsions. Leeberg and colleagues¹³² recently performed a systematic review of all studies reporting on treatment of distal avulsion fractures.They noted that most treatments were currently performed arthroscopically and that outcomes were generally good. Another recent biomechanical study compared antegrade screw fixation with suture anchor fixation and pullout suture fixation.¹³³ The authors noted that suture anchor fixation has slightly less displacement of the bony fragment when compared to screw fixation and pull-out sutures, and that the strength to failure was higher in the suture anchor fixation when compared to the pullout suture fixation. The outcomes of this study suggest that screw fixation and suture anchor fixation might be superior to pullout suture fixation, which might be interesting as with pullout suture fixation the ligament cannot be directly tensioned to the tibial footprint, which can lead to anteroposterior laxity.¹³² Clinical studies are necessary to assess the preferred treatment in these tear types but it seems that screw fixation is preferred in large bony avulsion fractures, while suture anchor fixation or pullout suture fixation can be used for soft tissue avulsion tears.

Complex Tears or Poor Tissue Quality: Reconstruction

If the tear is complex, multiple tears are present, or the tissue quality is poor, then preservation of the ligament is not possible, and in these cases a standard reconstruction should be performed.

Conclusion

When reviewing the literature of ACL preservation, it becomes clear that the evolution of surgical treatment of ACL injuries was biased. Preservation of the native ligament has many advantages, such as better proprioception, graft vascularization, an optical guide for tibial tunnel placement, and a decreased incidence of tunnel widening that can be expected. Furthermore, arthroscopic primary ACL repair is minimally invasive and does not burn any bridges for future reconstructions, if necessary. This is in addition to the other (theoretical) advantages of primary repair, such as restoration of native kinematics and a decreased risk of osteoarthritis. Modern advances have significantly changed the risk-benefit ratio that should make us reconsider ACL preservation approaches. Certainly, further research in this area is warranted. In this article we have presented a treatment algorithm for ACL preservation, which is based on tear location and remnant tissue quality.

Am J Orthop. 2016;45(7):E393-E405. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Injury of the anterior cruciate ligament (ACL) is very common with over 200,000 annual injuries in the United Status.^1,2 There is a general consensus that these injuries should not be treated conservatively in patients that are younger, or who wish to remain active.^3,4 Reconstructive surgery is currently the preferred treatment in these patients, and anatomic single-bundle reconstruction with autografts is considered the gold standard.^5,6

Reconstruction of the ACL is, however, not a perfect treatment. Following single-bundle autograft reconstruction, revision rates of 3% to 8%,^6-9 contralateral injury rates of 3% to 8%,^10,11 and infection rates of 0.5% to 3%^7,12,13 have been reported. Furthermore, due to the invasive nature of graft harvesting and the surgical procedure, 10% to 25% of the patients are not satisfied following ACL reconstruction.^14,15 This can often be explained by common complaints, such as anterior knee pain (13%-43%), kneeling pain (12%-54%), quadriceps muscle atrophy (20%-30%),^16,17 and loss of range of motion (ROM) (12%-23%).^7,9,18,19 Furthermore, as a result of the invasive nature of reconstructive surgery, revisions can be difficult due to complications, such as tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22 This can lead to inferior outcomes and higher rates (13%) of revision surgery compared to primary reconstruction.^23-26 Finally, reconstructive surgery does not restore native kinematics of the ACL,^27-29 which may partially explain why reconstructive surgery has not been shown to prevent osteoarthritis.^28-31

Over the past decades, there has been an increasing interest in the preservation of the ACL in an attempt to ameliorate these issues.^32-37 Ligament preservation focuses on preserving the native tissues and biology, while minimizing the surgical morbidity to the patients.

Some authors have recently reported on arthroscopic primary repair of proximal ACL tears in which the ligament is reattached onto the femoral wall using modern-day suture anchor technology.^32,38 Others have augmented this repair technique with an internal brace^39,40 or with a synthetic device.^33,41 When performing primary repair, it is believed that proprioception is maintained,^42-44 while experimental studies have suggested that primary repair also restores the native kinematics,⁴⁵ and may prevent osteoarthritis.⁴⁶ Furthermore, primary repair is a conservative approach in that no grafts need to be harvested, no tunnels need to be drilled, and revision surgery, if necessary, is more analogous to primary reconstructions.³²In patients with partial tears, some surgeons have advocated preserving the anteromedial (AM) or posterolateral (PL) bundle and performing selective single-bundle augmentation.^34,35 In addition, several authors have used remnant tensioning^36,47 or remnant preservation^37,48 in combination with reconstructive surgery in order to benefit from the biological characteristics of the remnant. These techniques lead to better proprioceptive function,^44,49,50 vascularization and ligamentization of the graft,^50-52 provide an optical guide for anatomic tunnel placement,⁵³ and decrease the incidence of tunnel widening.^54,55The feasibility and applicability of these surgical techniques mainly depends on the tear type and tissue quality of the torn ligament. In this article we (I) discuss the history of ACL preservation, (II) discuss how modern advances alter the risk-benefit ratio for ACL preservation, and (III) propose a treatment algorithm for ACL injuries that is based on tear location and tissue quality.

History of ACL Preservation

The history of the surgical treatment of ACL injuries started in 1895 when Robson⁵⁶ treated a 41-year-old male who tore both cruciate ligaments from the femoral wall. Performing primary repair with catgut ligatures, both cruciate ligaments were preserved and the patients had resolution of pain symptoms and full function at 6-year follow-up. Over the following decades, Palmer^57,58 and O’Donoghue^59,60 further popularized open primary repair for the treatment of ACL injuries, and this technique was the most commonly performed treatment in the 1970s and early 1980s.^61-65 The initial short-term results of primary repair were excellent,^61,62 but Feagin and Curl⁶⁶ were the first to note that the results deteriorated at mid-term follow-up. Despite improvements in the surgical technique of repairing the ACL, such as the usage of nonabsorbable sutures and directly tying the sutures over bone,^63,67 the results remained disappointing at longer-term follow-up.^68-70

In response to these disappointing results, surgeons sought to improve the surgical treatment by either augmenting the primary repair with a semitendinosus, a patella tendon graft or an augmentation device,^71-74 or by performing primary reconstruction.^75-77 At the end of the 1980s and early 1990s, several randomized and prospective clinical trials were performed in order to compare the outcomes of these techniques.^74,78-82 Many studies showed that results of augmented repair were more reliable when compared to primary repair, which led to the abandonment of primary repair in favor of augmented repair, and eventually primary reconstruction.⁶⁵

The Important Role of Tear Location in Ligament Preservation

When taking a closer look at the outcomes of primary repair and augmented repair, it seems that the results of these preservation techniques were not as disappointing as was suggested. This can be explained, in large part, by the fact that the important roles of tear location and tissue quality were not widely recognized.

Sherman and colleagues⁷⁰ reported in 1991 their mid-term results of open primary repair. Similar to others, they noted a deterioration of their results at mid-term follow-up. However, they uniquely performed an extensive subgroup analysis in order to find an explanation for this. In their study, considered a landmark paper on primary repair,^65,70 they concluded that, “poor tissue quality is typical for midsubstance tears and that a repair of these injuries will predictably fail while type I tears (proximal), with better tissue quality, show a definite trend towards better results.”⁷⁰ With these findings, they confirmed the findings of others that had recognized a trend of better outcomes with proximal tears.^64,67,83-85

A majority of the historical studies that were published before 1991 had not considered the role of tear location and tissue quality on outcomes of open primary repair. This was also true for the aforementioned randomized studies that compared primary repair with augmented repair and primary reconstruction. Because these studies randomized patients and did not take tear location into account, it can be expected that patients with midsubstance tears were included in the cohorts of primary repair and the outcomes of these studies were therefore confounded.^74,78-82 If these studies would have been aware of the role that tear location plays on primary repair outcomes, different outcomes may have been found and different conclusions on the optimal treatment for different tear types may have been drawn.⁸⁶

Open Primary ACL Repair Outcomes Stratified by Tear Location

When reviewing the literature of open primary repair outcomes stratified by tear location, it is noted that multiple studies reported excellent outcomes following primary repair of proximal ACL tears.^{73,83,84,87-90} Weaver and colleagues⁶⁴ were among the first to stratify their results by tear location, and they found that more patients with proximal tears (52 of 66; 79%) were satisfied after the procedure when compared to patients with midsubstance tears (3 of 13; 23%) at 3.5-year follow-up. They concluded that, “selection can be made with some predictability of the type of injury to the ligament as to which patients will do better.”⁶⁴ Kühne and colleagues⁸⁹ reported the outcomes of 75 patients with proximal tears treated with open primary repair and noted no failures, negative pivot shift in 88% of patients, stable or nearly stable Lachman test in 87% of patients, and 89% return to sports rate at 4-year follow-up. Raunest and colleagues⁹¹ reported a negative pivot shift and negative anterior drawer test in 84%, return to sports in 71%, and satisfaction in 75% of 51 patients that underwent open primary repair of proximal tears at 3.5-year follow-up.

Interestingly, and in contrast to the findings of Feagin and Curl,⁶⁶ no deterioration of the outcomes at mid-term follow-up was noted in patients with proximal tears. Genelin and colleagues⁸⁸ reported their results of 42 patients with proximal tears treated with open primary repair at 5- to 7-year follow-up. They found a negative pivot shift in 81%, stable or nearly stable Lachman test in 81%, and patient satisfaction in 86% of patients. Similarly, Bräm and colleagues⁸⁷ found good results at mid-term follow-up with a good-excellent Lysholm score in 79%, return to a similar level of sports in 76%, stable or nearly stable Lachman test in 91%, and anterior drawer test in 94% of patients, along with an 88% satisfaction rate and 7% failure rate in patients who underwent open primary repair of proximal tears.

On the contrary, when the outcomes of studies that performed open primary repair in mainly, or only, patients with midsubstance tears are reviewed, significantly inferior results are found. Frank and colleagues⁹² reported outcomes in 42 patients with midsubstance tears at 4-year follow-up. They reported that 56% had a stable or nearly stable anterior drawer test, 78% had a positive pivot shift, and that only 61% were satisfied with the procedure. Odensten and colleagues⁷⁸ reported outcomes of open primary repair in a subgroup of 22 patients with midsubstance tears at 1.5-year follow-up, and noted a 14% failure rate.

When reviewing the mid-term results in patients with midsubstance tears, it seems that there was more deterioration in outcomes.^69,70 Firstly, the aforementioned study by Sherman and colleagues⁷⁰ showed poor results in the patients with (type IV) midsubstance tears at mid-term follow-up. Furthermore, Kaplan and colleagues⁶⁹ reported the mid-term outcomes of 70 patients, of which 56 patients had midsubstance tears. After having reported good outcomes at short-term follow-up,^63,67 they noted that 42% of patients had >3 mm anteroposterior stability when compared to the contralateral leg, only a 62% return to sport rate, and a 17% failure rate. They concluded that, “Although … primary repair of the anterior cruciate may work in some patients, it is an unpredictable operative procedure.”

These studies showed that the outcomes of open primary repair were significantly better in patients with proximal ACL tears and sufficient tissue quality when compared to midsubstance tears. This suggests that open primary ACL repair may have been prematurely abandoned as a treatment option for patients with proximal tears.

Augmented ACL Repair

There were several reasons why augmented repair became the preferred treatment in the early and mid 1990s. First of all, the results of augmented repair were more consistent compared to primary repair in the aforementioned randomized and prospective studies,^74,78-82 which is not surprising given the fact that the role of tear location was not widely recognized at the time. Secondly, in the 1970s and early 1980s, patients were treated postoperatively in a cast for 6 weeks, which led to problems, such as loss of ROM, pain, and decreased function.^93,94 At the end of the1980s and 1990s, the focus shifted from prolonged joint immobilization towards early postoperative ROM.^95-97 Since many authors believed that primary repair of the ACL was not strong enough to tolerate early mobilization, an augmentation was added to the technique in order to fortify the repair and enable early ROM.⁹⁸

Interestingly, augmented repair, which is essentially a combination of primary ACL repair and ACL reconstruction, was mainly performed in the 1990s and many surgeons did recognize the role of tear location in this treatment at this point.^73,98-103 In these years, the treatment algorithm consisted of augmented ACL repair in patients with proximal tears in the acute setting and ACL reconstruction in patients with midsubstance or chronic tears. Several different augmentation techniques were used to reinforce the primary repair in these years including autograft tissues (semitendinosus tendon,^102-104 patellar tendon,¹⁰⁰ or iliotibial band [ITB]¹⁰⁵) synthetic materials (polydioxanone [PDS],^101,102,106 carbon fibre,⁷⁴ and polyester [Trevira]⁹⁷), augmentation devices (Kennedy Ligament Augmentation Device [LAD]^98-100) and extra-articular augmentations.⁷³

When reviewing the outcomes of augmented repair of the ACL, good to excellent results can be found in studies that used this technique in patients with proximal tears.^73,98-106 Kdolsky and colleagues⁹⁸ were in one of the first groups that reported their results of augmented repair in only patients with proximal tears. In 1993, they reported their mid-term outcomes (5 to 8 years) in 66 patients who underwent primary repair and augmentation with the Kennedy LAD and found that 97% of patients had stable knees (<3 mm on KT-1000 examination), 98% had a negative pivot shift, and 76% returned to previous level of sports. However, often-reported problems with the augmentation devices were found in this study with rupture of the device (12%) and decreased ROM (14%).⁹⁸ In 1995, Grøntvedt and Engebretsen¹⁰⁰ compared augmentation with the Kennedy LAD to patellar tendon augmentation in a randomized study of patients with acute proximal tears. They noted that 50% of the patients in the Kennedy LAD group had a positive pivot shift compared to 23% in the patellar tendon group. Furthermore, they found KT-1000 leg differences of <3 mm in 92% of the patellar tendon group and 54% of the Kennedy LAD group. Because the authors found significant differences between both groups at 1- and 2-year follow-up, they stopped the clinical trial.

Several authors in the following years reported good results of augmented repair using autograft tissues. Natri and colleagues¹⁰⁵ reported the outcomes of 72 patients treated with primary repair of proximal tears augmented with the ITB at 3.5-year follow-up. They found 89% negative pivot shift rate, 93% stable or nearly stable Lachman test, 99% stable or nearly stable anterior drawer test, 79% satisfaction rate, and 91% return to previous level of sports rate. Krueger-Franke and colleagues¹⁰⁴ reported the outcomes of primary repair of proximal tears with augmentation using the semitendinosus tendon. In a retrospective study of 76 patients, they noted that 96% of patients had a negative pivot shift, 75% of patients had stable or nearly stable Lachman test, 93% were satisfied with the procedure, a mean Lysholm score of 92, a Tegner score that only decreased from 7.2 to 7.1, and KT-1000 testing with 78% <4 mm leg difference with the contralateral leg. The authors concluded that patients with femoral ruptures could be treated with augmented repair when performed in the acute setting. As this study was published in 1998, they stated that magnetic resonance imaging and arthroscopy could be helpful in identifying the tear location.

Final Abandonment of ACL Preservation

Reviewing these outcomes raises the question as to why these techniques were ultimately abandoned in the treatment algorithm of proximal ACL injuries, especially given the aforementioned advantages of ACL preservation. One of the possible answers can be found in a landmark study on ACL reconstruction and rehabilitation published by Shelbourne and colleagues¹⁰⁷ in 1991. At that time, arthrofibrosis and knee stiffness were frequently reported problems following ACL surgery, which could partially be explained by the standard conservative rehabilitation using postoperative joint immobilization.^67,70,80,88

Shelbourne and colleagues¹⁰⁷ aimed to assess the cause of arthrofibrosis and knee stiffness, and divided the patients into groups by number of days between injury and surgery (<7, 7 to 21 days, and >21 days between injury and surgery). Furthermore, patients within these groups underwent either a conventional or accelerated rehabilitation program. The authors not only found that patients undergoing accelerated rehabilitation had less arthrofibrosis, but they also noted that less arthrofibrosis was seen when surgery was delayed. These findings, however, contrasted with the general perception that the ACL should be repaired in the first 3 weeks postinjury to ensure optimal tissue quality with an augmented approach. As a result, the treatment of ACL injuries shifted towards ACL reconstruction after these findings. Krueger-Franke and colleagues¹⁰⁴ commented on the trend after the study of Shelbourne and colleagues:¹⁰⁷ “Less consideration has been given to the importance of the proprioceptive receptors in the tibial remnants of the torn ACL and the value of their preservation as part of a primary reconstruction.”

In addition to the trend away from an augmented repair approach due to the novel understanding of the importance of early mobilization, some discussion should focus on the technical limitations of arthroscopy at that time. While arthroscopy had been around for several decades, fluid management and arthroscopic instrumentation was slow to develop. All of the repair and augmentation techniques previously discussed had been performed via an open arthrotomy. Arthroscopic technologies of the time were not refined enough to enable surgeons to perform such complex, intra-articular techniques that would enable suturing of the ligament remnant. In this regard, arthroscopic ACL reconstruction was a much simpler technique to accomplish, and this also likely contributed to the final abandonment of the ligament preservation approach.

Role for ACL Preservation with Modern Advances

As stated in the introduction, there has been a recent resurgence of interest in preservation of the native ligament.^32-37 With the passage of time, many technologic advances have been made, which has allowed surgeons to reconsider the concept of ligament preservation.

First of all, appropriate patient selection was not applied historically, as the critical factors of tear location and tissue quality were not recognized in the era of open primary repair. In modern days, however, advances such as MRI have been developed, which can give the surgeon an idea of the status, and tear type of the ACL pre-operatively.¹⁰⁸ This may help the orthopaedic surgeon to plan the surgery and make an assessment as to whether ACL preservation is possible. Secondly, in the historic literature the postoperative regimen consisted of casting for 5 or 6 weeks,^67,70,80,88 while the focus later shifted towards early ROM.^95-97Modern day ACL rehabilitation focuses on immediate ROM to avoid the complications stiffness, pain and decreased function that plagued the outcomes when immobilization was used.^93,94 Thirdly, historically small tunnels were drilled with primary repair and sutures had to be tied over bone,^57,67 whereas currently suture anchors are available that prevent the need for tunnel drilling and enable direct suture tensioning.^32,38 Finally, and most importantly, in the historic literature patients were treated with an invasive arthrotomy technique, while modern day arthroscopic techniques readily enable the surgeon to effectively suture the remnant arthroscopically. Interestingly, in 2005, in their 20-year follow-up of primary repair surgeries, Strand and colleagues¹⁰⁹ stated, “if the same results could be accomplished by a smaller, arthroscopic procedure, primary repair might reduce the number of patients needing later reconstructions with small ‘costs’ in the way of risk and inconvenience for the patients. We therefore believe that further research and development of methods for closed (arthroscopic) repair are justified.”

Altered Risk-Benefit Ratio

Historically, the treatments of open primary repair and open ACL reconstruction were both invasive surgeries with an arthrotomy, drilling of bone tunnels, and postoperative joint immobilization for 4 to 6 weeks. However, with the modern-day advances, the risk-benefit ratio of both treatments has changed, as Strand and colleagues¹⁰⁹ had already suggested. Although ACL reconstruction can be performed arthroscopically, it remains an invasive procedure, in which tunnels are drilled, patellar tendons or hamstring tendons are harvested, and complications, such as knee pain and quadriceps atrophy, are common. The surgery of primary ACL repair, however, has benefited significantly from the modern developments.^32,38 Primary ACL repair can now be performed arthroscopically, and by using suture anchors no tunnels need to be drilled and the remnant can be tensioned directly. An additional benefit of the use of suture anchors is that revision surgery of a failed primary repair is analogous to primary reconstruction, whereas revision surgery of a failed ACL reconstruction can be problematic due to tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22

Reviewing the differences between arthroscopic primary ACL repair and ACL reconstruction, it becomes clear that primary repair has benefited significantly from the modern advances and that the risk-benefit ratio for primary repair has been altered. This means that patients with proximal tears can be treated with a relatively straight forward, minimally invasive surgery, which has been shown to be effective in 85% to 90% of patients.^32,38

Treatment Algorithm Based on Tear Location

Since 2008, in the practice of the senior author (GSD), the surgical treatment algorithm for ACL injuries is completely based on the tear location and tissue quality of the ligament.^110,111 To describe the different tear types, we use the modified Sherman classification in which we extended his classification towards the tibial side whereas Sherman and colleagues⁷⁰ only described the femoral side of the tears (Figures A-F, Table).

Type I Tears: Primary Repair

Type I tears are soft tissue avulsion type tears that can be easily treated with arthroscopic primary repair.¹⁰⁷ The length of the distal remnant has to be at least 90% and the tissue quality has to be good to excellent in order to approximate the remnant towards the femoral wall (Table).¹¹² The incidence of type I tears was 26% in the study of Sherman and colleagues,⁷⁰ although recent studies showed a lower incidence (6% to 10%) in a larger population.^32,38 Certainly, individual practices will see different percentages of type I tears based upon the mix of injury mechanisms they see most frequently. Over the last 2 years, with the recognition of the importance of tear type and tissue quality, there has been a renewed interest in arthroscopic primary ACL repair.^32,38

DiFelice and colleagues³² were the first to arthroscopically perform primary repair of the ACL in proximal tears using suture anchors. They reported the outcomes of the first 11 consecutive patients that underwent primary repair in a previously described technique.¹¹³ At mean 3.5-year follow-up, they noted only 1 failure (9%) due to re-injury; mean Lysholm score of 93.2; mean modified Cincinnati score of 91.5; pre- and postoperative Tegner score of 7.3 and 6.9, respectively; SANE score of 91.8; and subjective International Knee Documentation Committee (IKDC) score of 86.4. Of the patients with an intact repair, 9 patients had an objective IKDC rating A and 1 patient had B and all patients had KT-1000 leg differences of <3 mm with the contralateral side (three patients were not available for KT-1000 testing). The authors concluded that arthroscopic primary ACL repair could achieve short-term clinical success in a selected group of patients with proximal avulsion tears and excellent tissue quality. They further noted that mid-term outcomes are necessary given that the results of open primary repair deteriorated at longer-term follow-up in the historical literature. Recently, the senior author (GSD) has added an Internal Brace (Arthrex) to the primary repair with the goal of protecting the ligament in the first weeks to further promote healing of the ligament.^39,40,114

More recently, Achtnich and colleagues³⁸ compared the treatment of arthroscopic primary ACL repair with primary ACL reconstruction in 41 patients with type I tears at 2.3-years follow-up. Twenty-one patients consented for primary repair while 20 patients declined this procedure and underwent primary reconstruction. They noted no significant differences in Lachman test, pivot shift test, objective IKDC score, and KT-1000 scores. Although not significant, the clinical failure rate in the primary repair group (15%) was higher than the reconstruction group (0%). Interestingly, despite the higher failure rate in the repair group, the authors concluded that primary ACL repair is recommended in a carefully selected group of patients with type I tears and excellent tissue quality, which can likely be explained by the differences in the risk-benefit ratio between both procedures.

Over the last decade, the research group led by Murray^46,115,116 has performed experimental research on primary repair with a biological scaffold and reported many interesting findings that could be extrapolated to primary ACL repair. First of all, they compared bioenhanced primary repair with bioenhanced primary reconstruction in 64 Yucutan pigs and noted that there was significantly less macroscopic cartilage damage in the primary repair group at 1-year follow-up.⁴⁶ They concluded that bioenhanced ACL repair may provide a new, less invasive treatment option that reduces cartilage damage following joint injury. This may suggest that primary repair may have a lower incidence of osteoarthritis when compared to ACL reconstruction, which is interesting as osteoarthritis is very common after ACL reconstruction. Further research in this area is certainly warranted.

In another study they compared bioenhanced primary repair in juvenile, adolescent and mature Yucutan pigs and noted that functional healing depended on the level of skeletal maturity with immature animals having a more productive healing response.¹¹⁶ This indicates that primary repair might be a good treatment option in skeletally immature patients, especially since reconstruction increases the risk of premature closure of the epiphysis^117,118 and delaying treatment increases the risk of meniscus injury.¹¹⁹ Interestingly, a recent meta-analysis showed indeed that the risk of epiphysis closure was lower in primary repair when compared to ACL reconstruction and the rupture rate was also lower.¹¹⁸ Primary repair may be a good treatment option in children as the procedure has all the attributes that should be applicable to children: it is minimally morbid, tissue sparing, and it is a conservative approach that does not burn any surgical bridges for future reconstructive surgery if necessary.

Finally, the research group of Murray¹¹⁵ assessed the effect of surgical delay of primary repair following injury in Yucutan pigs and noted that better biomechanical outcomes were noted after delaying surgery for 2 weeks when compared to 6 weeks. This suggests that primary repair should preferably be performed in the acute setting, which has also been shown in historical studies since the ligament in the acute setting has optimal tissue quality and the ligament is less likely to be retracted or reabsorbed.^59,60,115

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the tear locations of the AM and PL bundle are not at the same location and Zantop and colleagues¹²⁰ reported in an arthroscopic study that this could be as frequent as in 30% of all complete tears. In some of these tears, one of the bundles can be avulsed of the femoral wall (type I tear) while the other bundle is not directly repairable (non-type I tear). In these cases, the senior author (GSD) will repair the type I tear bundle, whereas a hamstring augmentation is placed at the location of the other bundle. When reviewing the literature, a combination of primary repair of one bundle and reconstruction of the second bundle has not been described before. However, over the last decade several surgeons have performed augmentation of one bundle in the setting of partial tears.^{34,35,121-124}

Buda and colleagues³⁴ were the first to perform selective AM or PL bundle reconstruction in the setting of partial tears.³⁴ At 5-year follow-up, they reported no reruptures and only 1 patient with an IKDC C-score, although reoperation was necessary in 4 out of 47 patients (9%). Following this publication, many others reported on selective bundle reconstruction.^35,121-124 However, with partial tears, the knee is often stable and a selective augmentation technique is utilized to prevent complete rupture of the ligament. The application of this technique is essentially different from reconstruction for complete ACL tears in which the knee is unstable, there is a giving way sensation and patients have problems participating in sports.

Type II Tears: Augmented Repair

Type II tears often have good or excellent tissue quality and can be pulled up towards the femoral footprint, but are too short to be firmly attached. Sherman and colleagues⁷⁰ reported that approximately 22% patients had a type II tear, which corresponds to a tear located in the proximal part of the ligament. With this technique, multiple suture passes are used to stitch the remnant and, in addition, a smaller hamstring autograft or allograft is passed through the middle of the tibial remnant. A suture button is used proximally for the graft, and the tensioning repair sutures through the remnant are also passed through the suture button. The suture button is passed through the femoral tunnel and flipped so that the graft is proximally fixed. Then, the repair sutures of the remnant are tensioned, and the ligament is pulled towards the femoral wall as a sleeve around the graft. When the ligament is approximated to the femoral wall, the sutures are tied over the suture button. The graft is then tensioned distally to complete the augmented repair.

In the recent literature, the technique of augmentation of a primary repair using autograft tissue has not been reported. However, augmented repair using an internal brace^39,40 or augmentation devices^33,41 have been recently performed. MacKay and colleagues³⁹ reported good outcomes of arthroscopic primary repair of proximal tears using an internal brace. Eggli and colleagues³³ reported the results of the first 10 patients treated with ACL preservation using primary repair of the ligament with the addition of a dynamic screw-spring mechanism. The authors reported good preliminary results with one failure (10%) and good objective and subjective outcomes. In a next study, they reported the outcomes of 278 patients and although they reported good clinical outcomes and a revision rate of 4%, the reoperation rate for removal of the screw-spring mechanism was high (24%).⁴¹ This is not surprising when reviewing the historical literature in which high complication rates of the augmentation devices were reported.^99,100 We were unable to identify any other studies reporting surgical techniques of augmenting primary repair in the literature.

Type III Tears: Reconstruction With Remnant Tensioning

In patients with type III tears, the ligament cannot be approximated to the wall and reconstruction is necessary in order to restore knee stability. However, in these cases the ligament has sufficient length (25%-75%) and can be tensioned along or around the graft. Preservation of the ligament remnant has several (theoretical) advantages, such as better proprioceptive function,^42,49,50 vascularization and ligamentization of the graft,^50-52 an optical guide for anatomic tunnel placement,⁵³ and a decreased incidence of tunnel widening.^54,55 Furthermore, tensioning of the remnant is thought to lower the risk of cyclops lesions when compared to remnant preservation.¹²⁵ Although the difference between augmented repair and remnant tensioning seems small, the purpose of surgery is different. With augmented repair, the ligament can be approximated close to the femoral wall and the goal of surgery is to use the healing capacity that the ACL has in the proximal part of the ligament,¹²⁶ while with remnant tensioning the goal is only to benefit from some of the aforementioned advantages. Ahn and colleagues³⁶ were the first to perform this technique and stated, “Our concept is that the remnant tissue has only an additive effect.” Furthermore, with augmented repair multiple sutures are passed through the AM and PL bundle in order to sufficiently approximate the ligament to the femoral wall, while with the remnant tensioning technique generally one or a few sutures or lasso loop are passed through the proximal part to tension the ligament, prevent sagging of the remnant, and decrease the risk of cyclops lesions.^127,128

Several authors have recently performed remnant tensioning during ACL.^{36,47,125-127} Ahn and colleagues⁴⁷ reported excellent objective and subjective outcomes following this procedure and found that with re-arthroscopy nearly all patients had fair synovialization of the graft. Others have reported similarly good outcomes of these techniques.^125,129,130 However, studies comparing this treatment with normal ACL reconstruction and assessing outcomes, failure rates and proprioception are lacking.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some patients the ligament is torn distally or the tissue quality is not optimal. In these patients, the remnant can be debrided to the part of good tissue quality in order to preserve the biology and minimize the risk for cyclops lesions. A standard reconstruction needs to be performed to restore the instability, but by preserving the remnant, advantages, such as proprioception,^44,49,50 graft vascularization,^50-52 an optical guide for tibial tunnel placement,⁵³ and a decreased incidence of tunnel widening^54,55 can be expected.

Lee and colleagues³⁷ presented the tibial remnant technique in which standard reconstruction was performed, and the tibial tunnel was drilled through the center of the remnant. In a later study, they compared remnant preservation with a remnant of <20% of the total ACL length with >20% of the length and found that proprioception was better with more remnant volume.⁴⁸ Similarly, Muneta and colleagues¹³¹ assessed the role of remnant length and found that remnant length is positively correlated with better stability measured on KT-1000 anteroposterior stability.

Several studies compared ACL reconstruction with remnant preservation vs conventional ACL reconstruction.^52,54,129 Takazawa and colleagues⁵² performed a retrospective study of 183 patients and found that patients in the remnant preservation group had significantly better KT-2000 stability, while they also reported a significantly lower graft rupture rate in this group (1.1% vs 7.1%) at 2-year follow-up. Hong and colleagues¹²⁹ performed a randomized clinical trial of 80 patients and did not find these differences, although there was a trend towards higher Lysholm scores in the remnant preservation group. Finally, Zhang and colleagues⁵⁴ performed a randomized clinical trial and found a lower incidence and amount of tibial tunnel widening in the preserving-remnant group when compared to the removing-remnant group. These studies show that there is likely a role for remnant preservation.

Type V Tears: Primary Repair

In some patients, the ligament is torn in the distal 10% of the ligament, which can occur as a distal avulsion tear or as a distal bony avulsion fracture.¹³² Bony avulsion fractures are most commonly seen in children whereas true distal soft tissue avulsion tears are very rare.¹³²

Treatments of these tear types include antegrade screw fixation, pullout sutures or the use of suture anchors in case of bony avulsion fractures and pullout sutures with tying over a bony bridge or ligament button in case of soft tissue avulsions. Leeberg and colleagues¹³² recently performed a systematic review of all studies reporting on treatment of distal avulsion fractures.They noted that most treatments were currently performed arthroscopically and that outcomes were generally good. Another recent biomechanical study compared antegrade screw fixation with suture anchor fixation and pullout suture fixation.¹³³ The authors noted that suture anchor fixation has slightly less displacement of the bony fragment when compared to screw fixation and pull-out sutures, and that the strength to failure was higher in the suture anchor fixation when compared to the pullout suture fixation. The outcomes of this study suggest that screw fixation and suture anchor fixation might be superior to pullout suture fixation, which might be interesting as with pullout suture fixation the ligament cannot be directly tensioned to the tibial footprint, which can lead to anteroposterior laxity.¹³² Clinical studies are necessary to assess the preferred treatment in these tear types but it seems that screw fixation is preferred in large bony avulsion fractures, while suture anchor fixation or pullout suture fixation can be used for soft tissue avulsion tears.

Complex Tears or Poor Tissue Quality: Reconstruction

If the tear is complex, multiple tears are present, or the tissue quality is poor, then preservation of the ligament is not possible, and in these cases a standard reconstruction should be performed.

Conclusion

When reviewing the literature of ACL preservation, it becomes clear that the evolution of surgical treatment of ACL injuries was biased. Preservation of the native ligament has many advantages, such as better proprioception, graft vascularization, an optical guide for tibial tunnel placement, and a decreased incidence of tunnel widening that can be expected. Furthermore, arthroscopic primary ACL repair is minimally invasive and does not burn any bridges for future reconstructions, if necessary. This is in addition to the other (theoretical) advantages of primary repair, such as restoration of native kinematics and a decreased risk of osteoarthritis. Modern advances have significantly changed the risk-benefit ratio that should make us reconsider ACL preservation approaches. Certainly, further research in this area is warranted. In this article we have presented a treatment algorithm for ACL preservation, which is based on tear location and remnant tissue quality.

Am J Orthop. 2016;45(7):E393-E405. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Injury of the anterior cruciate ligament (ACL) is very common with over 200,000 annual injuries in the United Status.^1,2 There is a general consensus that these injuries should not be treated conservatively in patients that are younger, or who wish to remain active.^3,4 Reconstructive surgery is currently the preferred treatment in these patients, and anatomic single-bundle reconstruction with autografts is considered the gold standard.^5,6

Reconstruction of the ACL is, however, not a perfect treatment. Following single-bundle autograft reconstruction, revision rates of 3% to 8%,^6-9 contralateral injury rates of 3% to 8%,^10,11 and infection rates of 0.5% to 3%^7,12,13 have been reported. Furthermore, due to the invasive nature of graft harvesting and the surgical procedure, 10% to 25% of the patients are not satisfied following ACL reconstruction.^14,15 This can often be explained by common complaints, such as anterior knee pain (13%-43%), kneeling pain (12%-54%), quadriceps muscle atrophy (20%-30%),^16,17 and loss of range of motion (ROM) (12%-23%).^7,9,18,19 Furthermore, as a result of the invasive nature of reconstructive surgery, revisions can be difficult due to complications, such as tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22 This can lead to inferior outcomes and higher rates (13%) of revision surgery compared to primary reconstruction.^23-26 Finally, reconstructive surgery does not restore native kinematics of the ACL,^27-29 which may partially explain why reconstructive surgery has not been shown to prevent osteoarthritis.^28-31

Over the past decades, there has been an increasing interest in the preservation of the ACL in an attempt to ameliorate these issues.^32-37 Ligament preservation focuses on preserving the native tissues and biology, while minimizing the surgical morbidity to the patients.

Some authors have recently reported on arthroscopic primary repair of proximal ACL tears in which the ligament is reattached onto the femoral wall using modern-day suture anchor technology.^32,38 Others have augmented this repair technique with an internal brace^39,40 or with a synthetic device.^33,41 When performing primary repair, it is believed that proprioception is maintained,^42-44 while experimental studies have suggested that primary repair also restores the native kinematics,⁴⁵ and may prevent osteoarthritis.⁴⁶ Furthermore, primary repair is a conservative approach in that no grafts need to be harvested, no tunnels need to be drilled, and revision surgery, if necessary, is more analogous to primary reconstructions.³²In patients with partial tears, some surgeons have advocated preserving the anteromedial (AM) or posterolateral (PL) bundle and performing selective single-bundle augmentation.^34,35 In addition, several authors have used remnant tensioning^36,47 or remnant preservation^37,48 in combination with reconstructive surgery in order to benefit from the biological characteristics of the remnant. These techniques lead to better proprioceptive function,^44,49,50 vascularization and ligamentization of the graft,^50-52 provide an optical guide for anatomic tunnel placement,⁵³ and decrease the incidence of tunnel widening.^54,55The feasibility and applicability of these surgical techniques mainly depends on the tear type and tissue quality of the torn ligament. In this article we (I) discuss the history of ACL preservation, (II) discuss how modern advances alter the risk-benefit ratio for ACL preservation, and (III) propose a treatment algorithm for ACL injuries that is based on tear location and tissue quality.

History of ACL Preservation

The history of the surgical treatment of ACL injuries started in 1895 when Robson⁵⁶ treated a 41-year-old male who tore both cruciate ligaments from the femoral wall. Performing primary repair with catgut ligatures, both cruciate ligaments were preserved and the patients had resolution of pain symptoms and full function at 6-year follow-up. Over the following decades, Palmer^57,58 and O’Donoghue^59,60 further popularized open primary repair for the treatment of ACL injuries, and this technique was the most commonly performed treatment in the 1970s and early 1980s.^61-65 The initial short-term results of primary repair were excellent,^61,62 but Feagin and Curl⁶⁶ were the first to note that the results deteriorated at mid-term follow-up. Despite improvements in the surgical technique of repairing the ACL, such as the usage of nonabsorbable sutures and directly tying the sutures over bone,^63,67 the results remained disappointing at longer-term follow-up.^68-70

In response to these disappointing results, surgeons sought to improve the surgical treatment by either augmenting the primary repair with a semitendinosus, a patella tendon graft or an augmentation device,^71-74 or by performing primary reconstruction.^75-77 At the end of the 1980s and early 1990s, several randomized and prospective clinical trials were performed in order to compare the outcomes of these techniques.^74,78-82 Many studies showed that results of augmented repair were more reliable when compared to primary repair, which led to the abandonment of primary repair in favor of augmented repair, and eventually primary reconstruction.⁶⁵

The Important Role of Tear Location in Ligament Preservation

When taking a closer look at the outcomes of primary repair and augmented repair, it seems that the results of these preservation techniques were not as disappointing as was suggested. This can be explained, in large part, by the fact that the important roles of tear location and tissue quality were not widely recognized.

Sherman and colleagues⁷⁰ reported in 1991 their mid-term results of open primary repair. Similar to others, they noted a deterioration of their results at mid-term follow-up. However, they uniquely performed an extensive subgroup analysis in order to find an explanation for this. In their study, considered a landmark paper on primary repair,^65,70 they concluded that, “poor tissue quality is typical for midsubstance tears and that a repair of these injuries will predictably fail while type I tears (proximal), with better tissue quality, show a definite trend towards better results.”⁷⁰ With these findings, they confirmed the findings of others that had recognized a trend of better outcomes with proximal tears.^64,67,83-85

A majority of the historical studies that were published before 1991 had not considered the role of tear location and tissue quality on outcomes of open primary repair. This was also true for the aforementioned randomized studies that compared primary repair with augmented repair and primary reconstruction. Because these studies randomized patients and did not take tear location into account, it can be expected that patients with midsubstance tears were included in the cohorts of primary repair and the outcomes of these studies were therefore confounded.^74,78-82 If these studies would have been aware of the role that tear location plays on primary repair outcomes, different outcomes may have been found and different conclusions on the optimal treatment for different tear types may have been drawn.⁸⁶

Open Primary ACL Repair Outcomes Stratified by Tear Location

When reviewing the literature of open primary repair outcomes stratified by tear location, it is noted that multiple studies reported excellent outcomes following primary repair of proximal ACL tears.^{73,83,84,87-90} Weaver and colleagues⁶⁴ were among the first to stratify their results by tear location, and they found that more patients with proximal tears (52 of 66; 79%) were satisfied after the procedure when compared to patients with midsubstance tears (3 of 13; 23%) at 3.5-year follow-up. They concluded that, “selection can be made with some predictability of the type of injury to the ligament as to which patients will do better.”⁶⁴ Kühne and colleagues⁸⁹ reported the outcomes of 75 patients with proximal tears treated with open primary repair and noted no failures, negative pivot shift in 88% of patients, stable or nearly stable Lachman test in 87% of patients, and 89% return to sports rate at 4-year follow-up. Raunest and colleagues⁹¹ reported a negative pivot shift and negative anterior drawer test in 84%, return to sports in 71%, and satisfaction in 75% of 51 patients that underwent open primary repair of proximal tears at 3.5-year follow-up.

Interestingly, and in contrast to the findings of Feagin and Curl,⁶⁶ no deterioration of the outcomes at mid-term follow-up was noted in patients with proximal tears. Genelin and colleagues⁸⁸ reported their results of 42 patients with proximal tears treated with open primary repair at 5- to 7-year follow-up. They found a negative pivot shift in 81%, stable or nearly stable Lachman test in 81%, and patient satisfaction in 86% of patients. Similarly, Bräm and colleagues⁸⁷ found good results at mid-term follow-up with a good-excellent Lysholm score in 79%, return to a similar level of sports in 76%, stable or nearly stable Lachman test in 91%, and anterior drawer test in 94% of patients, along with an 88% satisfaction rate and 7% failure rate in patients who underwent open primary repair of proximal tears.

On the contrary, when the outcomes of studies that performed open primary repair in mainly, or only, patients with midsubstance tears are reviewed, significantly inferior results are found. Frank and colleagues⁹² reported outcomes in 42 patients with midsubstance tears at 4-year follow-up. They reported that 56% had a stable or nearly stable anterior drawer test, 78% had a positive pivot shift, and that only 61% were satisfied with the procedure. Odensten and colleagues⁷⁸ reported outcomes of open primary repair in a subgroup of 22 patients with midsubstance tears at 1.5-year follow-up, and noted a 14% failure rate.

When reviewing the mid-term results in patients with midsubstance tears, it seems that there was more deterioration in outcomes.^69,70 Firstly, the aforementioned study by Sherman and colleagues⁷⁰ showed poor results in the patients with (type IV) midsubstance tears at mid-term follow-up. Furthermore, Kaplan and colleagues⁶⁹ reported the mid-term outcomes of 70 patients, of which 56 patients had midsubstance tears. After having reported good outcomes at short-term follow-up,^63,67 they noted that 42% of patients had >3 mm anteroposterior stability when compared to the contralateral leg, only a 62% return to sport rate, and a 17% failure rate. They concluded that, “Although … primary repair of the anterior cruciate may work in some patients, it is an unpredictable operative procedure.”

These studies showed that the outcomes of open primary repair were significantly better in patients with proximal ACL tears and sufficient tissue quality when compared to midsubstance tears. This suggests that open primary ACL repair may have been prematurely abandoned as a treatment option for patients with proximal tears.

Augmented ACL Repair

There were several reasons why augmented repair became the preferred treatment in the early and mid 1990s. First of all, the results of augmented repair were more consistent compared to primary repair in the aforementioned randomized and prospective studies,^74,78-82 which is not surprising given the fact that the role of tear location was not widely recognized at the time. Secondly, in the 1970s and early 1980s, patients were treated postoperatively in a cast for 6 weeks, which led to problems, such as loss of ROM, pain, and decreased function.^93,94 At the end of the1980s and 1990s, the focus shifted from prolonged joint immobilization towards early postoperative ROM.^95-97 Since many authors believed that primary repair of the ACL was not strong enough to tolerate early mobilization, an augmentation was added to the technique in order to fortify the repair and enable early ROM.⁹⁸

Interestingly, augmented repair, which is essentially a combination of primary ACL repair and ACL reconstruction, was mainly performed in the 1990s and many surgeons did recognize the role of tear location in this treatment at this point.^73,98-103 In these years, the treatment algorithm consisted of augmented ACL repair in patients with proximal tears in the acute setting and ACL reconstruction in patients with midsubstance or chronic tears. Several different augmentation techniques were used to reinforce the primary repair in these years including autograft tissues (semitendinosus tendon,^102-104 patellar tendon,¹⁰⁰ or iliotibial band [ITB]¹⁰⁵) synthetic materials (polydioxanone [PDS],^101,102,106 carbon fibre,⁷⁴ and polyester [Trevira]⁹⁷), augmentation devices (Kennedy Ligament Augmentation Device [LAD]^98-100) and extra-articular augmentations.⁷³

When reviewing the outcomes of augmented repair of the ACL, good to excellent results can be found in studies that used this technique in patients with proximal tears.^73,98-106 Kdolsky and colleagues⁹⁸ were in one of the first groups that reported their results of augmented repair in only patients with proximal tears. In 1993, they reported their mid-term outcomes (5 to 8 years) in 66 patients who underwent primary repair and augmentation with the Kennedy LAD and found that 97% of patients had stable knees (<3 mm on KT-1000 examination), 98% had a negative pivot shift, and 76% returned to previous level of sports. However, often-reported problems with the augmentation devices were found in this study with rupture of the device (12%) and decreased ROM (14%).⁹⁸ In 1995, Grøntvedt and Engebretsen¹⁰⁰ compared augmentation with the Kennedy LAD to patellar tendon augmentation in a randomized study of patients with acute proximal tears. They noted that 50% of the patients in the Kennedy LAD group had a positive pivot shift compared to 23% in the patellar tendon group. Furthermore, they found KT-1000 leg differences of <3 mm in 92% of the patellar tendon group and 54% of the Kennedy LAD group. Because the authors found significant differences between both groups at 1- and 2-year follow-up, they stopped the clinical trial.

Several authors in the following years reported good results of augmented repair using autograft tissues. Natri and colleagues¹⁰⁵ reported the outcomes of 72 patients treated with primary repair of proximal tears augmented with the ITB at 3.5-year follow-up. They found 89% negative pivot shift rate, 93% stable or nearly stable Lachman test, 99% stable or nearly stable anterior drawer test, 79% satisfaction rate, and 91% return to previous level of sports rate. Krueger-Franke and colleagues¹⁰⁴ reported the outcomes of primary repair of proximal tears with augmentation using the semitendinosus tendon. In a retrospective study of 76 patients, they noted that 96% of patients had a negative pivot shift, 75% of patients had stable or nearly stable Lachman test, 93% were satisfied with the procedure, a mean Lysholm score of 92, a Tegner score that only decreased from 7.2 to 7.1, and KT-1000 testing with 78% <4 mm leg difference with the contralateral leg. The authors concluded that patients with femoral ruptures could be treated with augmented repair when performed in the acute setting. As this study was published in 1998, they stated that magnetic resonance imaging and arthroscopy could be helpful in identifying the tear location.

Final Abandonment of ACL Preservation

Reviewing these outcomes raises the question as to why these techniques were ultimately abandoned in the treatment algorithm of proximal ACL injuries, especially given the aforementioned advantages of ACL preservation. One of the possible answers can be found in a landmark study on ACL reconstruction and rehabilitation published by Shelbourne and colleagues¹⁰⁷ in 1991. At that time, arthrofibrosis and knee stiffness were frequently reported problems following ACL surgery, which could partially be explained by the standard conservative rehabilitation using postoperative joint immobilization.^67,70,80,88

Shelbourne and colleagues¹⁰⁷ aimed to assess the cause of arthrofibrosis and knee stiffness, and divided the patients into groups by number of days between injury and surgery (<7, 7 to 21 days, and >21 days between injury and surgery). Furthermore, patients within these groups underwent either a conventional or accelerated rehabilitation program. The authors not only found that patients undergoing accelerated rehabilitation had less arthrofibrosis, but they also noted that less arthrofibrosis was seen when surgery was delayed. These findings, however, contrasted with the general perception that the ACL should be repaired in the first 3 weeks postinjury to ensure optimal tissue quality with an augmented approach. As a result, the treatment of ACL injuries shifted towards ACL reconstruction after these findings. Krueger-Franke and colleagues¹⁰⁴ commented on the trend after the study of Shelbourne and colleagues:¹⁰⁷ “Less consideration has been given to the importance of the proprioceptive receptors in the tibial remnants of the torn ACL and the value of their preservation as part of a primary reconstruction.”

In addition to the trend away from an augmented repair approach due to the novel understanding of the importance of early mobilization, some discussion should focus on the technical limitations of arthroscopy at that time. While arthroscopy had been around for several decades, fluid management and arthroscopic instrumentation was slow to develop. All of the repair and augmentation techniques previously discussed had been performed via an open arthrotomy. Arthroscopic technologies of the time were not refined enough to enable surgeons to perform such complex, intra-articular techniques that would enable suturing of the ligament remnant. In this regard, arthroscopic ACL reconstruction was a much simpler technique to accomplish, and this also likely contributed to the final abandonment of the ligament preservation approach.

Role for ACL Preservation with Modern Advances

As stated in the introduction, there has been a recent resurgence of interest in preservation of the native ligament.^32-37 With the passage of time, many technologic advances have been made, which has allowed surgeons to reconsider the concept of ligament preservation.

First of all, appropriate patient selection was not applied historically, as the critical factors of tear location and tissue quality were not recognized in the era of open primary repair. In modern days, however, advances such as MRI have been developed, which can give the surgeon an idea of the status, and tear type of the ACL pre-operatively.¹⁰⁸ This may help the orthopaedic surgeon to plan the surgery and make an assessment as to whether ACL preservation is possible. Secondly, in the historic literature the postoperative regimen consisted of casting for 5 or 6 weeks,^67,70,80,88 while the focus later shifted towards early ROM.^95-97Modern day ACL rehabilitation focuses on immediate ROM to avoid the complications stiffness, pain and decreased function that plagued the outcomes when immobilization was used.^93,94 Thirdly, historically small tunnels were drilled with primary repair and sutures had to be tied over bone,^57,67 whereas currently suture anchors are available that prevent the need for tunnel drilling and enable direct suture tensioning.^32,38 Finally, and most importantly, in the historic literature patients were treated with an invasive arthrotomy technique, while modern day arthroscopic techniques readily enable the surgeon to effectively suture the remnant arthroscopically. Interestingly, in 2005, in their 20-year follow-up of primary repair surgeries, Strand and colleagues¹⁰⁹ stated, “if the same results could be accomplished by a smaller, arthroscopic procedure, primary repair might reduce the number of patients needing later reconstructions with small ‘costs’ in the way of risk and inconvenience for the patients. We therefore believe that further research and development of methods for closed (arthroscopic) repair are justified.”

Altered Risk-Benefit Ratio

Historically, the treatments of open primary repair and open ACL reconstruction were both invasive surgeries with an arthrotomy, drilling of bone tunnels, and postoperative joint immobilization for 4 to 6 weeks. However, with the modern-day advances, the risk-benefit ratio of both treatments has changed, as Strand and colleagues¹⁰⁹ had already suggested. Although ACL reconstruction can be performed arthroscopically, it remains an invasive procedure, in which tunnels are drilled, patellar tendons or hamstring tendons are harvested, and complications, such as knee pain and quadriceps atrophy, are common. The surgery of primary ACL repair, however, has benefited significantly from the modern developments.^32,38 Primary ACL repair can now be performed arthroscopically, and by using suture anchors no tunnels need to be drilled and the remnant can be tensioned directly. An additional benefit of the use of suture anchors is that revision surgery of a failed primary repair is analogous to primary reconstruction, whereas revision surgery of a failed ACL reconstruction can be problematic due to tunnel widening, tunnel malpositioning, and preexisting hardware.^20-22

Reviewing the differences between arthroscopic primary ACL repair and ACL reconstruction, it becomes clear that primary repair has benefited significantly from the modern advances and that the risk-benefit ratio for primary repair has been altered. This means that patients with proximal tears can be treated with a relatively straight forward, minimally invasive surgery, which has been shown to be effective in 85% to 90% of patients.^32,38

Treatment Algorithm Based on Tear Location

Since 2008, in the practice of the senior author (GSD), the surgical treatment algorithm for ACL injuries is completely based on the tear location and tissue quality of the ligament.^110,111 To describe the different tear types, we use the modified Sherman classification in which we extended his classification towards the tibial side whereas Sherman and colleagues⁷⁰ only described the femoral side of the tears (Figures A-F, Table).

Type I Tears: Primary Repair

Type I tears are soft tissue avulsion type tears that can be easily treated with arthroscopic primary repair.¹⁰⁷ The length of the distal remnant has to be at least 90% and the tissue quality has to be good to excellent in order to approximate the remnant towards the femoral wall (Table).¹¹² The incidence of type I tears was 26% in the study of Sherman and colleagues,⁷⁰ although recent studies showed a lower incidence (6% to 10%) in a larger population.^32,38 Certainly, individual practices will see different percentages of type I tears based upon the mix of injury mechanisms they see most frequently. Over the last 2 years, with the recognition of the importance of tear type and tissue quality, there has been a renewed interest in arthroscopic primary ACL repair.^32,38

DiFelice and colleagues³² were the first to arthroscopically perform primary repair of the ACL in proximal tears using suture anchors. They reported the outcomes of the first 11 consecutive patients that underwent primary repair in a previously described technique.¹¹³ At mean 3.5-year follow-up, they noted only 1 failure (9%) due to re-injury; mean Lysholm score of 93.2; mean modified Cincinnati score of 91.5; pre- and postoperative Tegner score of 7.3 and 6.9, respectively; SANE score of 91.8; and subjective International Knee Documentation Committee (IKDC) score of 86.4. Of the patients with an intact repair, 9 patients had an objective IKDC rating A and 1 patient had B and all patients had KT-1000 leg differences of <3 mm with the contralateral side (three patients were not available for KT-1000 testing). The authors concluded that arthroscopic primary ACL repair could achieve short-term clinical success in a selected group of patients with proximal avulsion tears and excellent tissue quality. They further noted that mid-term outcomes are necessary given that the results of open primary repair deteriorated at longer-term follow-up in the historical literature. Recently, the senior author (GSD) has added an Internal Brace (Arthrex) to the primary repair with the goal of protecting the ligament in the first weeks to further promote healing of the ligament.^39,40,114

More recently, Achtnich and colleagues³⁸ compared the treatment of arthroscopic primary ACL repair with primary ACL reconstruction in 41 patients with type I tears at 2.3-years follow-up. Twenty-one patients consented for primary repair while 20 patients declined this procedure and underwent primary reconstruction. They noted no significant differences in Lachman test, pivot shift test, objective IKDC score, and KT-1000 scores. Although not significant, the clinical failure rate in the primary repair group (15%) was higher than the reconstruction group (0%). Interestingly, despite the higher failure rate in the repair group, the authors concluded that primary ACL repair is recommended in a carefully selected group of patients with type I tears and excellent tissue quality, which can likely be explained by the differences in the risk-benefit ratio between both procedures.

Over the last decade, the research group led by Murray^46,115,116 has performed experimental research on primary repair with a biological scaffold and reported many interesting findings that could be extrapolated to primary ACL repair. First of all, they compared bioenhanced primary repair with bioenhanced primary reconstruction in 64 Yucutan pigs and noted that there was significantly less macroscopic cartilage damage in the primary repair group at 1-year follow-up.⁴⁶ They concluded that bioenhanced ACL repair may provide a new, less invasive treatment option that reduces cartilage damage following joint injury. This may suggest that primary repair may have a lower incidence of osteoarthritis when compared to ACL reconstruction, which is interesting as osteoarthritis is very common after ACL reconstruction. Further research in this area is certainly warranted.

In another study they compared bioenhanced primary repair in juvenile, adolescent and mature Yucutan pigs and noted that functional healing depended on the level of skeletal maturity with immature animals having a more productive healing response.¹¹⁶ This indicates that primary repair might be a good treatment option in skeletally immature patients, especially since reconstruction increases the risk of premature closure of the epiphysis^117,118 and delaying treatment increases the risk of meniscus injury.¹¹⁹ Interestingly, a recent meta-analysis showed indeed that the risk of epiphysis closure was lower in primary repair when compared to ACL reconstruction and the rupture rate was also lower.¹¹⁸ Primary repair may be a good treatment option in children as the procedure has all the attributes that should be applicable to children: it is minimally morbid, tissue sparing, and it is a conservative approach that does not burn any surgical bridges for future reconstructive surgery if necessary.

Finally, the research group of Murray¹¹⁵ assessed the effect of surgical delay of primary repair following injury in Yucutan pigs and noted that better biomechanical outcomes were noted after delaying surgery for 2 weeks when compared to 6 weeks. This suggests that primary repair should preferably be performed in the acute setting, which has also been shown in historical studies since the ligament in the acute setting has optimal tissue quality and the ligament is less likely to be retracted or reabsorbed.^59,60,115

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the tear locations of the AM and PL bundle are not at the same location and Zantop and colleagues¹²⁰ reported in an arthroscopic study that this could be as frequent as in 30% of all complete tears. In some of these tears, one of the bundles can be avulsed of the femoral wall (type I tear) while the other bundle is not directly repairable (non-type I tear). In these cases, the senior author (GSD) will repair the type I tear bundle, whereas a hamstring augmentation is placed at the location of the other bundle. When reviewing the literature, a combination of primary repair of one bundle and reconstruction of the second bundle has not been described before. However, over the last decade several surgeons have performed augmentation of one bundle in the setting of partial tears.^{34,35,121-124}

Buda and colleagues³⁴ were the first to perform selective AM or PL bundle reconstruction in the setting of partial tears.³⁴ At 5-year follow-up, they reported no reruptures and only 1 patient with an IKDC C-score, although reoperation was necessary in 4 out of 47 patients (9%). Following this publication, many others reported on selective bundle reconstruction.^35,121-124 However, with partial tears, the knee is often stable and a selective augmentation technique is utilized to prevent complete rupture of the ligament. The application of this technique is essentially different from reconstruction for complete ACL tears in which the knee is unstable, there is a giving way sensation and patients have problems participating in sports.

Type II Tears: Augmented Repair

Type II tears often have good or excellent tissue quality and can be pulled up towards the femoral footprint, but are too short to be firmly attached. Sherman and colleagues⁷⁰ reported that approximately 22% patients had a type II tear, which corresponds to a tear located in the proximal part of the ligament. With this technique, multiple suture passes are used to stitch the remnant and, in addition, a smaller hamstring autograft or allograft is passed through the middle of the tibial remnant. A suture button is used proximally for the graft, and the tensioning repair sutures through the remnant are also passed through the suture button. The suture button is passed through the femoral tunnel and flipped so that the graft is proximally fixed. Then, the repair sutures of the remnant are tensioned, and the ligament is pulled towards the femoral wall as a sleeve around the graft. When the ligament is approximated to the femoral wall, the sutures are tied over the suture button. The graft is then tensioned distally to complete the augmented repair.

In the recent literature, the technique of augmentation of a primary repair using autograft tissue has not been reported. However, augmented repair using an internal brace^39,40 or augmentation devices^33,41 have been recently performed. MacKay and colleagues³⁹ reported good outcomes of arthroscopic primary repair of proximal tears using an internal brace. Eggli and colleagues³³ reported the results of the first 10 patients treated with ACL preservation using primary repair of the ligament with the addition of a dynamic screw-spring mechanism. The authors reported good preliminary results with one failure (10%) and good objective and subjective outcomes. In a next study, they reported the outcomes of 278 patients and although they reported good clinical outcomes and a revision rate of 4%, the reoperation rate for removal of the screw-spring mechanism was high (24%).⁴¹ This is not surprising when reviewing the historical literature in which high complication rates of the augmentation devices were reported.^99,100 We were unable to identify any other studies reporting surgical techniques of augmenting primary repair in the literature.

Type III Tears: Reconstruction With Remnant Tensioning

In patients with type III tears, the ligament cannot be approximated to the wall and reconstruction is necessary in order to restore knee stability. However, in these cases the ligament has sufficient length (25%-75%) and can be tensioned along or around the graft. Preservation of the ligament remnant has several (theoretical) advantages, such as better proprioceptive function,^42,49,50 vascularization and ligamentization of the graft,^50-52 an optical guide for anatomic tunnel placement,⁵³ and a decreased incidence of tunnel widening.^54,55 Furthermore, tensioning of the remnant is thought to lower the risk of cyclops lesions when compared to remnant preservation.¹²⁵ Although the difference between augmented repair and remnant tensioning seems small, the purpose of surgery is different. With augmented repair, the ligament can be approximated close to the femoral wall and the goal of surgery is to use the healing capacity that the ACL has in the proximal part of the ligament,¹²⁶ while with remnant tensioning the goal is only to benefit from some of the aforementioned advantages. Ahn and colleagues³⁶ were the first to perform this technique and stated, “Our concept is that the remnant tissue has only an additive effect.” Furthermore, with augmented repair multiple sutures are passed through the AM and PL bundle in order to sufficiently approximate the ligament to the femoral wall, while with the remnant tensioning technique generally one or a few sutures or lasso loop are passed through the proximal part to tension the ligament, prevent sagging of the remnant, and decrease the risk of cyclops lesions.^127,128

Several authors have recently performed remnant tensioning during ACL.^{36,47,125-127} Ahn and colleagues⁴⁷ reported excellent objective and subjective outcomes following this procedure and found that with re-arthroscopy nearly all patients had fair synovialization of the graft. Others have reported similarly good outcomes of these techniques.^125,129,130 However, studies comparing this treatment with normal ACL reconstruction and assessing outcomes, failure rates and proprioception are lacking.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some patients the ligament is torn distally or the tissue quality is not optimal. In these patients, the remnant can be debrided to the part of good tissue quality in order to preserve the biology and minimize the risk for cyclops lesions. A standard reconstruction needs to be performed to restore the instability, but by preserving the remnant, advantages, such as proprioception,^44,49,50 graft vascularization,^50-52 an optical guide for tibial tunnel placement,⁵³ and a decreased incidence of tunnel widening^54,55 can be expected.

Lee and colleagues³⁷ presented the tibial remnant technique in which standard reconstruction was performed, and the tibial tunnel was drilled through the center of the remnant. In a later study, they compared remnant preservation with a remnant of <20% of the total ACL length with >20% of the length and found that proprioception was better with more remnant volume.⁴⁸ Similarly, Muneta and colleagues¹³¹ assessed the role of remnant length and found that remnant length is positively correlated with better stability measured on KT-1000 anteroposterior stability.

Several studies compared ACL reconstruction with remnant preservation vs conventional ACL reconstruction.^52,54,129 Takazawa and colleagues⁵² performed a retrospective study of 183 patients and found that patients in the remnant preservation group had significantly better KT-2000 stability, while they also reported a significantly lower graft rupture rate in this group (1.1% vs 7.1%) at 2-year follow-up. Hong and colleagues¹²⁹ performed a randomized clinical trial of 80 patients and did not find these differences, although there was a trend towards higher Lysholm scores in the remnant preservation group. Finally, Zhang and colleagues⁵⁴ performed a randomized clinical trial and found a lower incidence and amount of tibial tunnel widening in the preserving-remnant group when compared to the removing-remnant group. These studies show that there is likely a role for remnant preservation.

Type V Tears: Primary Repair

In some patients, the ligament is torn in the distal 10% of the ligament, which can occur as a distal avulsion tear or as a distal bony avulsion fracture.¹³² Bony avulsion fractures are most commonly seen in children whereas true distal soft tissue avulsion tears are very rare.¹³²

Treatments of these tear types include antegrade screw fixation, pullout sutures or the use of suture anchors in case of bony avulsion fractures and pullout sutures with tying over a bony bridge or ligament button in case of soft tissue avulsions. Leeberg and colleagues¹³² recently performed a systematic review of all studies reporting on treatment of distal avulsion fractures.They noted that most treatments were currently performed arthroscopically and that outcomes were generally good. Another recent biomechanical study compared antegrade screw fixation with suture anchor fixation and pullout suture fixation.¹³³ The authors noted that suture anchor fixation has slightly less displacement of the bony fragment when compared to screw fixation and pull-out sutures, and that the strength to failure was higher in the suture anchor fixation when compared to the pullout suture fixation. The outcomes of this study suggest that screw fixation and suture anchor fixation might be superior to pullout suture fixation, which might be interesting as with pullout suture fixation the ligament cannot be directly tensioned to the tibial footprint, which can lead to anteroposterior laxity.¹³² Clinical studies are necessary to assess the preferred treatment in these tear types but it seems that screw fixation is preferred in large bony avulsion fractures, while suture anchor fixation or pullout suture fixation can be used for soft tissue avulsion tears.

Complex Tears or Poor Tissue Quality: Reconstruction

If the tear is complex, multiple tears are present, or the tissue quality is poor, then preservation of the ligament is not possible, and in these cases a standard reconstruction should be performed.

Conclusion

When reviewing the literature of ACL preservation, it becomes clear that the evolution of surgical treatment of ACL injuries was biased. Preservation of the native ligament has many advantages, such as better proprioception, graft vascularization, an optical guide for tibial tunnel placement, and a decreased incidence of tunnel widening that can be expected. Furthermore, arthroscopic primary ACL repair is minimally invasive and does not burn any bridges for future reconstructions, if necessary. This is in addition to the other (theoretical) advantages of primary repair, such as restoration of native kinematics and a decreased risk of osteoarthritis. Modern advances have significantly changed the risk-benefit ratio that should make us reconsider ACL preservation approaches. Certainly, further research in this area is warranted. In this article we have presented a treatment algorithm for ACL preservation, which is based on tear location and remnant tissue quality.

Am J Orthop. 2016;45(7):E393-E405. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

In the first part of this series, “Preservation of the Anterior Cruciate Ligament: A Treatment Algorithm Based on Tear Location and Tissue Quality” we discussed the history of anterior cruciate ligament (ACL) preservation, and the historical outcomes of both open primary repair and augmented repair. We also presented our surgical treatment algorithm for ACL preservation, which is based on the tear location and tissue quality of the ligament remnant. In this article, we propose a modification of the Sherman classification¹ to identify the different tear types, and we will discuss the different surgical techniques that can be used for each one. Furthermore, we aim to provide an overview of the variations of these techniques that are seen in the literature. It is important to emphasize that these tear types and corresponding surgical techniques are to be seen as guidelines, rather than strict criteria, and that significant overlap between these tear types and surgical indications exist.

Assessment of Tear Type and Tissue Quality

The first assessment of the tear location and tissue quality is made using magnetic resonance imaging (MRI). Although MRI can give you an idea of where the tear is located, the final assessment for eligibility of each specific preservation technique is made during arthroscopy. Therefore, the routine preoperative discussion and informed consent process with the patient should encompass the gamut of surgical possibilities ranging from repair to reconstruction.

The Table shows our tear type classification, along with the corresponding preservation surgical techniques.

Surgical Preparation

In the operating room, the patient is placed in supine position on a standard operative table, such that the knee can be moved freely through its range of motion (ROM). The operative leg is then prepped and draped in standard fashion for knee arthroscopy. Standard knee arthroscopy equipment and implants are used, although some instruments from the standard shoulder set are also utilized. Anteromedial and anterolateral portals are created, and a general inspection of the knee is performed. By pulling the remnant ligament proximally using a broad tissue gasper, the available length of the remnant can be assessed. It is important to reduce possible anterior tibial subluxation in the sagittal plane in order to prevent “false” shortening of the distal ligament remnant. Once the length of the remnant tissue is assessed and the tissue quality is determined, the surgical preservation technique can be chosen (Table).

Type I Tears: Primary Repair

In order to be a candidate for arthroscopic primary repair, sufficient tissue length and tissue quality are necessary (Figures 1A and 1B, Table).

Sutures are then passed through the anteromedial bundle using the Scorpion Suture Passer (Arthrex) with a No. 2 FiberWire suture (Arthrex) (Figure 1C). Suturing is commenced at the intact distal end of the anteromedial bundle and is advanced in an alternating, interlocking Bunnell-type pattern towards the avulsed proximal end with approximately 4 mm to 5 mm between each pass. In general, 3 to 4 passes can be made before the final pass exits via the avulsed end of the ligament towards the femur (Figure 1D). The same process is then repeated for the posterolateral bundle of the ACL remnant with a No. 2 TigerWire suture (Arthrex) to optimize suture management. With each subsequent pass of the sutures, it is important to assess tissue resistance to prevent perforation of a previous stitch. Mild resistance is normal, but the suture-passing device should be repositioned when notably increased resistance is encountered. In addition, placing all of the bites in the same plane should be avoided since this can allow the sutures to “cheese cut” along the collagen fibers of the ligament remnant rather than holding firm.

After passing the sutures through both bundles, the sutures are guided outside the knee using an accessory stab incision situated just above the medial portal. Using this portal, the ligament can be retracted away from the femoral footprint for optimal visibility. The femoral footprint is then roughed using a shaver or burr, and bleeding is induced to stimulate a local healing response,² while the sutures and the ACL are protected via the portal. With the knee in flexion, an accessory inferomedial portal is then created under direct visualization using a spinal needle for localization. Care should be taken to enable the appropriate trajectory for anchor placement to be achieved.

Many different techniques can be used to provide fixation of the ACL repair to the femoral footprint; the 2 most straightforward techniques are presented here. The first technique provides fixation with knotless suture anchors,^3,4 whereas in the second technique the sutures are transosseously passed, and tied over a bone bridge, as was performed in the 1970s and 1980s.

Suture Anchor Fixation

With the suture anchor fixation technique, the knee is flexed in 90°, the anteromedial bundle origin within the femoral footprint is identified, and a 4.5-mm x 20-mm hole is drilled, punched, or tapped, in the case of high bone density. The FiberWire sutures are then retrieved through the accessory portal and passed through a 4.75-mm Vented BioComposite SwiveLock suture anchor (Arthrex). The suture anchor for the anteromedial bundle is then deployed into the hole within the anteromedial footprint, while tensioning the ACL remnant to the wall with a visual gap of <1 mm (Figure 1E).⁵ The procedure is then repeated using another suture anchor with TigerWire sutures for the posterolateral bundle with the knee flexed at 110° to 115°. This ensures an optimal angle of approach and avoids perforating the posterior condyle with the anchor. The drill hole and anchor are placed into the origin of the posterolateral bundle within the femoral footprint. The order of bundle tensioning and repair may be varied depending on the particulars of each case.

Once the anchors are fully deployed and flush with the femoral footprint, the handle is removed and the additional core stitches are unloaded. Occasionally, the core stitches can be passed from lateral to medial through the proximal ligament remnant and tied down with an arthroscopic knot pusher to add extra compression of the remnant to the origin. The free ends of the repair sutures are cut with an Open Ended Suture Cutter (Arthrex) so that they are flush with the notch. The repair is now complete (Figure 1F). Using a probe, the ACL remnant is tested for tension and stiffness. Finally, cycling of the knee through the full ROM confirms anatomic positioning without impingement of the graft. Manual laxity testing should reveal minimal anteroposterior translation with a firm endpoint on Lachman examination intraoperatively.

Bone Bridge Fixation

With this technique, parallel drill holes are created exiting at each bundle origin. The repair stitches can then be retrieved and tensioned proximally. One way to accomplish this is by using an ACL femoral guide (Arthrex) that is placed via the anterolateral portal and is centered on the anteromedial bundle insertion. This device guides a cannulated RetroDrill (Arthrex) to drill through the lateral femoral condyle towards the anteromedial footprint. A passing wire can then be delivered through the cannulation and used to retrieve that anteromedial bundle repair stitches. This process can then be repeated for the posterolateral bundle and the associated repair stitches. Drill holes can also be made retrograde from a low anteromedial accessory portal using a slotted pit that can be used to shuttle the repair stitches. When all the repair sutures are passed, the ligament is tensioned while being visualized arthroscopically. The knee is held at 20° of flexion and a posterior drawer force can be applied, if necessary, to reduce the tibia to its anatomic position. The suture limbs are then tensioned and can be fixated using any of a multitude of techniques, including tying over a bony bridge, tying over a 4-hole ligament button, and tying to a post.

One disadvantage of the bone bridge fixation technique, however, is the suspensory fixation that is not as stiff as tensioning and fixating with suture anchors. Despite this disadvantage, however, the senior author (GSD) has achieved excellent results with this technique at longer-term follow-up in a small group of patients. One advantage of the bone bridge fixation technique is that the procedure has lower costs than fixation with suture anchors.

One Anchor Repair Fixation

Achtnich and colleagues⁶ recently published a slightly different technique for repairing type I tears. The authors passed a No. 2 FiberWire suture through the midsubstance of both bundles of the ACL remnant to create a modified Mason-Allen stitch configuration. Subsequently, they tensioned the remnant towards the middle of the ACL footprint (between the anteromedial and posterolateral footprint) using one PushLock suture anchor (Arthrex). They hypothesized that using 1 anchor would be enough fixation for tears amenable to repair, and that doing so would minimize the invasion of the bone.

The preference of the senior author (GSD) is, however, to use 2 suture anchors for each bundle in order to more anatomically and biomechanically repair the remnant, since both bundles have different biomechanical characteristics.⁷ Similarly, the preference of the senior author is to commence the suturing as distal as possible and pass multiple sutures towards the proximal end. This ensures that the last suture pass is exited very proximally, and ensures that the proximal end is approximated towards the femoral wall. One suture passed at the midsubstance portion of the remnant might cause a different tension pattern and prevent optimal re-approximation of the most proximal part towards the femoral wall. Future studies are necessary to assess the efficacy of different suture and fixation techniques as these are currently lacking.

Addition of Internal Brace

Over the last few years, the senior author has added an internal brace (FiberTape, Arthrex) to the repair technique, which was first performed by MacKay and colleagues.⁸ The added internal brace protects the repair and the healing process in the first few weeks and enables early ROM.

With this technique, the previously described arthroscopic primary repair technique is performed with suturing of both bundles. However, after punching, tapping, or drilling a hole in the anteromedial origin of the femoral footprint, the anteromedial anchor is first loaded with the FiberTape in addition to the repair stitches. After placing the anteromedial suture anchor in the femoral footprint, the internal brace is fixated proximally with the suture anchor into the femoral wall.

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the anteromedial or posterolateral bundle is a type I tear with good or excellent tissue quality, whereas the other bundle is not a type I tear or has poor tissue quality (Figure 3A). In these cases, a primary repair of one bundle is performed with a hamstring reconstruction of the other bundle.

First, a No. 2 FiberWire is used to make 4 to 5 passes from distal to proximal, as previously described. Then, the remnants of the irreparable bundle are debrided (Figure 3B). Subsequently, the semitendinosus tendon is harvested in standard fashion, or soft tissue allografts can be used.

Type II Tears: Augmented Repair

In patients with type II tears, primary repair is not possible as the length of the remnant is too short to firmly approximate the remnant towards the femoral wall (75%-90% of native tissue length) (Figure 4A). In these patients, an augmented repair of the entire ACL is performed using hamstring autograft or soft tissue allograft.

With this technique, repair stitches are passed into the anteromedial bundle of the remnant as previously described (Figure 4B). Keeping the repair stitches anteriorly in the anteromedial bundle tends to prevent entanglement during graft passage later in the case.

Type III Tears: Reconstruction With Remnant Tensioning

The previously discussed techniques have the goals of preserving as much native ligament remnant as possible, approximating the ligament remnant towards the femoral wall, and promoting healing of the ligament. In some cases, however, the ligament remnant is too short for healing (Figure 5A). Although the ligament cannot be approximated to the femoral wall in these cases, there is still an argument for ACL preservation, as was discussed in the first article of this series.

If the ligament length is between 25% and 75% of the native tissue length, the senior author performs a remnant tensioning technique.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some cases, the distal remnant is small or the tissue quality in the largest part of the remnant is poor, and after debriding back to good tissue quality, only 10% to 25% of the native tissue length is left (Figure 6A). In these cases, the remnant is preserved, however, tensioning of the remnant with sutures is usually not necessary for the prevention of cyclops lesions. Nonetheless, it is important to debride the parts of the remnant ligament with poor tissue quality as mop-end patterns of the remnant may increase the chance of these lesions (Figure 6B).

In this situation, any of the standard ACL reconstruction techniques can be performed with simple attention being paid to preserving what is left of the tibial insertion site. At the very least, the small insertion remnant guides the anatomic placement of the graft, and prevents egress of joint fluid into the tibial tunnel and could minimize tunnel widening.

Type V Tears: Primary Repair

Finally, in some patients a soft tissue avulsion (Figure 7A) or bony avulsion of the distal attachment of the ACL can be seen. Both injuries are relatively rare, although bony avulsions are frequently seen in children, especially those younger than 12 years old. In these cases, the same techniques and theory that are applied to proximal avulsion type tears can be used and applied to distal avulsion type tears.

First, No. 2 FiberWire sutures are passed from proximal towards the distal end of the ligament in the anteromedial bundle, and the same process is then repeated for No. 2 TigerWire sutures for the posterolateral bundle. Then both sutures are exited at the distal avulsed end at the locations of the anteromedial and posterolateral footprints (Figure 7B). A 2.4-mm ACL guide wire and a Ninitol wire are used to drill 2 tunnels from the tibia towards the tibial footprint. The repair sutures are then retrieved through both tunnels (Figure 7C) and the sutures are tied distally over a ligament button after cycling of the knee (Figure 7D). This technique is very useful for soft tissue avulsions, or when there are only small flecks of bone or when the avulsed bone is significantly comminuted. If a large bony avulsion fragment is present, this technique can also be applied with some modification, although there have been multiple other techniques described in the literature that work well in this situation including fixation with screw and washer, or with suture anchors.

Complex Tear or Poor Tissue Quality: Reconstruction

In some cases, the tissue quality is poor, or the ligament has complex or multiple tears. Essentially, in these cases, there is nothing to preserve and a standard reconstruction approach is performed in these cases.

Conclusion

The uniform gold standard for all ACL tear types is currently primary reconstruction. However, several disadvantages of ACL reconstruction exist, while there are multiple advantages to the concept of ACL preservation. In this surgical technique article, we have discussed our tear type classification and the recommended surgical techniques for each. With this treatment algorithm, which is based on tear location and tissue quality, an optimal and minimally invasive treatment can be chosen for each individual patient. Future studies are needed to compare and contrast these treatments with the current gold standard of ACL reconstruction.

Am J Orthop. 2016;45(7):E406-E414. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

In the first part of this series, “Preservation of the Anterior Cruciate Ligament: A Treatment Algorithm Based on Tear Location and Tissue Quality” we discussed the history of anterior cruciate ligament (ACL) preservation, and the historical outcomes of both open primary repair and augmented repair. We also presented our surgical treatment algorithm for ACL preservation, which is based on the tear location and tissue quality of the ligament remnant. In this article, we propose a modification of the Sherman classification¹ to identify the different tear types, and we will discuss the different surgical techniques that can be used for each one. Furthermore, we aim to provide an overview of the variations of these techniques that are seen in the literature. It is important to emphasize that these tear types and corresponding surgical techniques are to be seen as guidelines, rather than strict criteria, and that significant overlap between these tear types and surgical indications exist.

Assessment of Tear Type and Tissue Quality

The first assessment of the tear location and tissue quality is made using magnetic resonance imaging (MRI). Although MRI can give you an idea of where the tear is located, the final assessment for eligibility of each specific preservation technique is made during arthroscopy. Therefore, the routine preoperative discussion and informed consent process with the patient should encompass the gamut of surgical possibilities ranging from repair to reconstruction.

The Table shows our tear type classification, along with the corresponding preservation surgical techniques.

Surgical Preparation

In the operating room, the patient is placed in supine position on a standard operative table, such that the knee can be moved freely through its range of motion (ROM). The operative leg is then prepped and draped in standard fashion for knee arthroscopy. Standard knee arthroscopy equipment and implants are used, although some instruments from the standard shoulder set are also utilized. Anteromedial and anterolateral portals are created, and a general inspection of the knee is performed. By pulling the remnant ligament proximally using a broad tissue gasper, the available length of the remnant can be assessed. It is important to reduce possible anterior tibial subluxation in the sagittal plane in order to prevent “false” shortening of the distal ligament remnant. Once the length of the remnant tissue is assessed and the tissue quality is determined, the surgical preservation technique can be chosen (Table).

Type I Tears: Primary Repair

In order to be a candidate for arthroscopic primary repair, sufficient tissue length and tissue quality are necessary (Figures 1A and 1B, Table).

Sutures are then passed through the anteromedial bundle using the Scorpion Suture Passer (Arthrex) with a No. 2 FiberWire suture (Arthrex) (Figure 1C). Suturing is commenced at the intact distal end of the anteromedial bundle and is advanced in an alternating, interlocking Bunnell-type pattern towards the avulsed proximal end with approximately 4 mm to 5 mm between each pass. In general, 3 to 4 passes can be made before the final pass exits via the avulsed end of the ligament towards the femur (Figure 1D). The same process is then repeated for the posterolateral bundle of the ACL remnant with a No. 2 TigerWire suture (Arthrex) to optimize suture management. With each subsequent pass of the sutures, it is important to assess tissue resistance to prevent perforation of a previous stitch. Mild resistance is normal, but the suture-passing device should be repositioned when notably increased resistance is encountered. In addition, placing all of the bites in the same plane should be avoided since this can allow the sutures to “cheese cut” along the collagen fibers of the ligament remnant rather than holding firm.

After passing the sutures through both bundles, the sutures are guided outside the knee using an accessory stab incision situated just above the medial portal. Using this portal, the ligament can be retracted away from the femoral footprint for optimal visibility. The femoral footprint is then roughed using a shaver or burr, and bleeding is induced to stimulate a local healing response,² while the sutures and the ACL are protected via the portal. With the knee in flexion, an accessory inferomedial portal is then created under direct visualization using a spinal needle for localization. Care should be taken to enable the appropriate trajectory for anchor placement to be achieved.

Many different techniques can be used to provide fixation of the ACL repair to the femoral footprint; the 2 most straightforward techniques are presented here. The first technique provides fixation with knotless suture anchors,^3,4 whereas in the second technique the sutures are transosseously passed, and tied over a bone bridge, as was performed in the 1970s and 1980s.

Suture Anchor Fixation

With the suture anchor fixation technique, the knee is flexed in 90°, the anteromedial bundle origin within the femoral footprint is identified, and a 4.5-mm x 20-mm hole is drilled, punched, or tapped, in the case of high bone density. The FiberWire sutures are then retrieved through the accessory portal and passed through a 4.75-mm Vented BioComposite SwiveLock suture anchor (Arthrex). The suture anchor for the anteromedial bundle is then deployed into the hole within the anteromedial footprint, while tensioning the ACL remnant to the wall with a visual gap of <1 mm (Figure 1E).⁵ The procedure is then repeated using another suture anchor with TigerWire sutures for the posterolateral bundle with the knee flexed at 110° to 115°. This ensures an optimal angle of approach and avoids perforating the posterior condyle with the anchor. The drill hole and anchor are placed into the origin of the posterolateral bundle within the femoral footprint. The order of bundle tensioning and repair may be varied depending on the particulars of each case.

Once the anchors are fully deployed and flush with the femoral footprint, the handle is removed and the additional core stitches are unloaded. Occasionally, the core stitches can be passed from lateral to medial through the proximal ligament remnant and tied down with an arthroscopic knot pusher to add extra compression of the remnant to the origin. The free ends of the repair sutures are cut with an Open Ended Suture Cutter (Arthrex) so that they are flush with the notch. The repair is now complete (Figure 1F). Using a probe, the ACL remnant is tested for tension and stiffness. Finally, cycling of the knee through the full ROM confirms anatomic positioning without impingement of the graft. Manual laxity testing should reveal minimal anteroposterior translation with a firm endpoint on Lachman examination intraoperatively.

Bone Bridge Fixation

With this technique, parallel drill holes are created exiting at each bundle origin. The repair stitches can then be retrieved and tensioned proximally. One way to accomplish this is by using an ACL femoral guide (Arthrex) that is placed via the anterolateral portal and is centered on the anteromedial bundle insertion. This device guides a cannulated RetroDrill (Arthrex) to drill through the lateral femoral condyle towards the anteromedial footprint. A passing wire can then be delivered through the cannulation and used to retrieve that anteromedial bundle repair stitches. This process can then be repeated for the posterolateral bundle and the associated repair stitches. Drill holes can also be made retrograde from a low anteromedial accessory portal using a slotted pit that can be used to shuttle the repair stitches. When all the repair sutures are passed, the ligament is tensioned while being visualized arthroscopically. The knee is held at 20° of flexion and a posterior drawer force can be applied, if necessary, to reduce the tibia to its anatomic position. The suture limbs are then tensioned and can be fixated using any of a multitude of techniques, including tying over a bony bridge, tying over a 4-hole ligament button, and tying to a post.

One disadvantage of the bone bridge fixation technique, however, is the suspensory fixation that is not as stiff as tensioning and fixating with suture anchors. Despite this disadvantage, however, the senior author (GSD) has achieved excellent results with this technique at longer-term follow-up in a small group of patients. One advantage of the bone bridge fixation technique is that the procedure has lower costs than fixation with suture anchors.

One Anchor Repair Fixation

Achtnich and colleagues⁶ recently published a slightly different technique for repairing type I tears. The authors passed a No. 2 FiberWire suture through the midsubstance of both bundles of the ACL remnant to create a modified Mason-Allen stitch configuration. Subsequently, they tensioned the remnant towards the middle of the ACL footprint (between the anteromedial and posterolateral footprint) using one PushLock suture anchor (Arthrex). They hypothesized that using 1 anchor would be enough fixation for tears amenable to repair, and that doing so would minimize the invasion of the bone.

The preference of the senior author (GSD) is, however, to use 2 suture anchors for each bundle in order to more anatomically and biomechanically repair the remnant, since both bundles have different biomechanical characteristics.⁷ Similarly, the preference of the senior author is to commence the suturing as distal as possible and pass multiple sutures towards the proximal end. This ensures that the last suture pass is exited very proximally, and ensures that the proximal end is approximated towards the femoral wall. One suture passed at the midsubstance portion of the remnant might cause a different tension pattern and prevent optimal re-approximation of the most proximal part towards the femoral wall. Future studies are necessary to assess the efficacy of different suture and fixation techniques as these are currently lacking.

Addition of Internal Brace

Over the last few years, the senior author has added an internal brace (FiberTape, Arthrex) to the repair technique, which was first performed by MacKay and colleagues.⁸ The added internal brace protects the repair and the healing process in the first few weeks and enables early ROM.

With this technique, the previously described arthroscopic primary repair technique is performed with suturing of both bundles. However, after punching, tapping, or drilling a hole in the anteromedial origin of the femoral footprint, the anteromedial anchor is first loaded with the FiberTape in addition to the repair stitches. After placing the anteromedial suture anchor in the femoral footprint, the internal brace is fixated proximally with the suture anchor into the femoral wall.

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the anteromedial or posterolateral bundle is a type I tear with good or excellent tissue quality, whereas the other bundle is not a type I tear or has poor tissue quality (Figure 3A). In these cases, a primary repair of one bundle is performed with a hamstring reconstruction of the other bundle.

First, a No. 2 FiberWire is used to make 4 to 5 passes from distal to proximal, as previously described. Then, the remnants of the irreparable bundle are debrided (Figure 3B). Subsequently, the semitendinosus tendon is harvested in standard fashion, or soft tissue allografts can be used.

Type II Tears: Augmented Repair

In patients with type II tears, primary repair is not possible as the length of the remnant is too short to firmly approximate the remnant towards the femoral wall (75%-90% of native tissue length) (Figure 4A). In these patients, an augmented repair of the entire ACL is performed using hamstring autograft or soft tissue allograft.

With this technique, repair stitches are passed into the anteromedial bundle of the remnant as previously described (Figure 4B). Keeping the repair stitches anteriorly in the anteromedial bundle tends to prevent entanglement during graft passage later in the case.

Type III Tears: Reconstruction With Remnant Tensioning

The previously discussed techniques have the goals of preserving as much native ligament remnant as possible, approximating the ligament remnant towards the femoral wall, and promoting healing of the ligament. In some cases, however, the ligament remnant is too short for healing (Figure 5A). Although the ligament cannot be approximated to the femoral wall in these cases, there is still an argument for ACL preservation, as was discussed in the first article of this series.

If the ligament length is between 25% and 75% of the native tissue length, the senior author performs a remnant tensioning technique.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some cases, the distal remnant is small or the tissue quality in the largest part of the remnant is poor, and after debriding back to good tissue quality, only 10% to 25% of the native tissue length is left (Figure 6A). In these cases, the remnant is preserved, however, tensioning of the remnant with sutures is usually not necessary for the prevention of cyclops lesions. Nonetheless, it is important to debride the parts of the remnant ligament with poor tissue quality as mop-end patterns of the remnant may increase the chance of these lesions (Figure 6B).

In this situation, any of the standard ACL reconstruction techniques can be performed with simple attention being paid to preserving what is left of the tibial insertion site. At the very least, the small insertion remnant guides the anatomic placement of the graft, and prevents egress of joint fluid into the tibial tunnel and could minimize tunnel widening.

Type V Tears: Primary Repair

Finally, in some patients a soft tissue avulsion (Figure 7A) or bony avulsion of the distal attachment of the ACL can be seen. Both injuries are relatively rare, although bony avulsions are frequently seen in children, especially those younger than 12 years old. In these cases, the same techniques and theory that are applied to proximal avulsion type tears can be used and applied to distal avulsion type tears.

First, No. 2 FiberWire sutures are passed from proximal towards the distal end of the ligament in the anteromedial bundle, and the same process is then repeated for No. 2 TigerWire sutures for the posterolateral bundle. Then both sutures are exited at the distal avulsed end at the locations of the anteromedial and posterolateral footprints (Figure 7B). A 2.4-mm ACL guide wire and a Ninitol wire are used to drill 2 tunnels from the tibia towards the tibial footprint. The repair sutures are then retrieved through both tunnels (Figure 7C) and the sutures are tied distally over a ligament button after cycling of the knee (Figure 7D). This technique is very useful for soft tissue avulsions, or when there are only small flecks of bone or when the avulsed bone is significantly comminuted. If a large bony avulsion fragment is present, this technique can also be applied with some modification, although there have been multiple other techniques described in the literature that work well in this situation including fixation with screw and washer, or with suture anchors.

Complex Tear or Poor Tissue Quality: Reconstruction

In some cases, the tissue quality is poor, or the ligament has complex or multiple tears. Essentially, in these cases, there is nothing to preserve and a standard reconstruction approach is performed in these cases.

Conclusion

The uniform gold standard for all ACL tear types is currently primary reconstruction. However, several disadvantages of ACL reconstruction exist, while there are multiple advantages to the concept of ACL preservation. In this surgical technique article, we have discussed our tear type classification and the recommended surgical techniques for each. With this treatment algorithm, which is based on tear location and tissue quality, an optimal and minimally invasive treatment can be chosen for each individual patient. Future studies are needed to compare and contrast these treatments with the current gold standard of ACL reconstruction.

Am J Orthop. 2016;45(7):E406-E414. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

In the first part of this series, “Preservation of the Anterior Cruciate Ligament: A Treatment Algorithm Based on Tear Location and Tissue Quality” we discussed the history of anterior cruciate ligament (ACL) preservation, and the historical outcomes of both open primary repair and augmented repair. We also presented our surgical treatment algorithm for ACL preservation, which is based on the tear location and tissue quality of the ligament remnant. In this article, we propose a modification of the Sherman classification¹ to identify the different tear types, and we will discuss the different surgical techniques that can be used for each one. Furthermore, we aim to provide an overview of the variations of these techniques that are seen in the literature. It is important to emphasize that these tear types and corresponding surgical techniques are to be seen as guidelines, rather than strict criteria, and that significant overlap between these tear types and surgical indications exist.

Assessment of Tear Type and Tissue Quality

The first assessment of the tear location and tissue quality is made using magnetic resonance imaging (MRI). Although MRI can give you an idea of where the tear is located, the final assessment for eligibility of each specific preservation technique is made during arthroscopy. Therefore, the routine preoperative discussion and informed consent process with the patient should encompass the gamut of surgical possibilities ranging from repair to reconstruction.

The Table shows our tear type classification, along with the corresponding preservation surgical techniques.

Surgical Preparation

In the operating room, the patient is placed in supine position on a standard operative table, such that the knee can be moved freely through its range of motion (ROM). The operative leg is then prepped and draped in standard fashion for knee arthroscopy. Standard knee arthroscopy equipment and implants are used, although some instruments from the standard shoulder set are also utilized. Anteromedial and anterolateral portals are created, and a general inspection of the knee is performed. By pulling the remnant ligament proximally using a broad tissue gasper, the available length of the remnant can be assessed. It is important to reduce possible anterior tibial subluxation in the sagittal plane in order to prevent “false” shortening of the distal ligament remnant. Once the length of the remnant tissue is assessed and the tissue quality is determined, the surgical preservation technique can be chosen (Table).

Type I Tears: Primary Repair

In order to be a candidate for arthroscopic primary repair, sufficient tissue length and tissue quality are necessary (Figures 1A and 1B, Table).

Sutures are then passed through the anteromedial bundle using the Scorpion Suture Passer (Arthrex) with a No. 2 FiberWire suture (Arthrex) (Figure 1C). Suturing is commenced at the intact distal end of the anteromedial bundle and is advanced in an alternating, interlocking Bunnell-type pattern towards the avulsed proximal end with approximately 4 mm to 5 mm between each pass. In general, 3 to 4 passes can be made before the final pass exits via the avulsed end of the ligament towards the femur (Figure 1D). The same process is then repeated for the posterolateral bundle of the ACL remnant with a No. 2 TigerWire suture (Arthrex) to optimize suture management. With each subsequent pass of the sutures, it is important to assess tissue resistance to prevent perforation of a previous stitch. Mild resistance is normal, but the suture-passing device should be repositioned when notably increased resistance is encountered. In addition, placing all of the bites in the same plane should be avoided since this can allow the sutures to “cheese cut” along the collagen fibers of the ligament remnant rather than holding firm.

After passing the sutures through both bundles, the sutures are guided outside the knee using an accessory stab incision situated just above the medial portal. Using this portal, the ligament can be retracted away from the femoral footprint for optimal visibility. The femoral footprint is then roughed using a shaver or burr, and bleeding is induced to stimulate a local healing response,² while the sutures and the ACL are protected via the portal. With the knee in flexion, an accessory inferomedial portal is then created under direct visualization using a spinal needle for localization. Care should be taken to enable the appropriate trajectory for anchor placement to be achieved.

Many different techniques can be used to provide fixation of the ACL repair to the femoral footprint; the 2 most straightforward techniques are presented here. The first technique provides fixation with knotless suture anchors,^3,4 whereas in the second technique the sutures are transosseously passed, and tied over a bone bridge, as was performed in the 1970s and 1980s.

Suture Anchor Fixation

With the suture anchor fixation technique, the knee is flexed in 90°, the anteromedial bundle origin within the femoral footprint is identified, and a 4.5-mm x 20-mm hole is drilled, punched, or tapped, in the case of high bone density. The FiberWire sutures are then retrieved through the accessory portal and passed through a 4.75-mm Vented BioComposite SwiveLock suture anchor (Arthrex). The suture anchor for the anteromedial bundle is then deployed into the hole within the anteromedial footprint, while tensioning the ACL remnant to the wall with a visual gap of <1 mm (Figure 1E).⁵ The procedure is then repeated using another suture anchor with TigerWire sutures for the posterolateral bundle with the knee flexed at 110° to 115°. This ensures an optimal angle of approach and avoids perforating the posterior condyle with the anchor. The drill hole and anchor are placed into the origin of the posterolateral bundle within the femoral footprint. The order of bundle tensioning and repair may be varied depending on the particulars of each case.

Once the anchors are fully deployed and flush with the femoral footprint, the handle is removed and the additional core stitches are unloaded. Occasionally, the core stitches can be passed from lateral to medial through the proximal ligament remnant and tied down with an arthroscopic knot pusher to add extra compression of the remnant to the origin. The free ends of the repair sutures are cut with an Open Ended Suture Cutter (Arthrex) so that they are flush with the notch. The repair is now complete (Figure 1F). Using a probe, the ACL remnant is tested for tension and stiffness. Finally, cycling of the knee through the full ROM confirms anatomic positioning without impingement of the graft. Manual laxity testing should reveal minimal anteroposterior translation with a firm endpoint on Lachman examination intraoperatively.

Bone Bridge Fixation

With this technique, parallel drill holes are created exiting at each bundle origin. The repair stitches can then be retrieved and tensioned proximally. One way to accomplish this is by using an ACL femoral guide (Arthrex) that is placed via the anterolateral portal and is centered on the anteromedial bundle insertion. This device guides a cannulated RetroDrill (Arthrex) to drill through the lateral femoral condyle towards the anteromedial footprint. A passing wire can then be delivered through the cannulation and used to retrieve that anteromedial bundle repair stitches. This process can then be repeated for the posterolateral bundle and the associated repair stitches. Drill holes can also be made retrograde from a low anteromedial accessory portal using a slotted pit that can be used to shuttle the repair stitches. When all the repair sutures are passed, the ligament is tensioned while being visualized arthroscopically. The knee is held at 20° of flexion and a posterior drawer force can be applied, if necessary, to reduce the tibia to its anatomic position. The suture limbs are then tensioned and can be fixated using any of a multitude of techniques, including tying over a bony bridge, tying over a 4-hole ligament button, and tying to a post.

One disadvantage of the bone bridge fixation technique, however, is the suspensory fixation that is not as stiff as tensioning and fixating with suture anchors. Despite this disadvantage, however, the senior author (GSD) has achieved excellent results with this technique at longer-term follow-up in a small group of patients. One advantage of the bone bridge fixation technique is that the procedure has lower costs than fixation with suture anchors.

One Anchor Repair Fixation

Achtnich and colleagues⁶ recently published a slightly different technique for repairing type I tears. The authors passed a No. 2 FiberWire suture through the midsubstance of both bundles of the ACL remnant to create a modified Mason-Allen stitch configuration. Subsequently, they tensioned the remnant towards the middle of the ACL footprint (between the anteromedial and posterolateral footprint) using one PushLock suture anchor (Arthrex). They hypothesized that using 1 anchor would be enough fixation for tears amenable to repair, and that doing so would minimize the invasion of the bone.

The preference of the senior author (GSD) is, however, to use 2 suture anchors for each bundle in order to more anatomically and biomechanically repair the remnant, since both bundles have different biomechanical characteristics.⁷ Similarly, the preference of the senior author is to commence the suturing as distal as possible and pass multiple sutures towards the proximal end. This ensures that the last suture pass is exited very proximally, and ensures that the proximal end is approximated towards the femoral wall. One suture passed at the midsubstance portion of the remnant might cause a different tension pattern and prevent optimal re-approximation of the most proximal part towards the femoral wall. Future studies are necessary to assess the efficacy of different suture and fixation techniques as these are currently lacking.

Addition of Internal Brace

Over the last few years, the senior author has added an internal brace (FiberTape, Arthrex) to the repair technique, which was first performed by MacKay and colleagues.⁸ The added internal brace protects the repair and the healing process in the first few weeks and enables early ROM.

With this technique, the previously described arthroscopic primary repair technique is performed with suturing of both bundles. However, after punching, tapping, or drilling a hole in the anteromedial origin of the femoral footprint, the anteromedial anchor is first loaded with the FiberTape in addition to the repair stitches. After placing the anteromedial suture anchor in the femoral footprint, the internal brace is fixated proximally with the suture anchor into the femoral wall.

One Bundle Type I Tears: Single Bundle Augmented Repair

In some cases, the anteromedial or posterolateral bundle is a type I tear with good or excellent tissue quality, whereas the other bundle is not a type I tear or has poor tissue quality (Figure 3A). In these cases, a primary repair of one bundle is performed with a hamstring reconstruction of the other bundle.

First, a No. 2 FiberWire is used to make 4 to 5 passes from distal to proximal, as previously described. Then, the remnants of the irreparable bundle are debrided (Figure 3B). Subsequently, the semitendinosus tendon is harvested in standard fashion, or soft tissue allografts can be used.

Type II Tears: Augmented Repair

In patients with type II tears, primary repair is not possible as the length of the remnant is too short to firmly approximate the remnant towards the femoral wall (75%-90% of native tissue length) (Figure 4A). In these patients, an augmented repair of the entire ACL is performed using hamstring autograft or soft tissue allograft.

With this technique, repair stitches are passed into the anteromedial bundle of the remnant as previously described (Figure 4B). Keeping the repair stitches anteriorly in the anteromedial bundle tends to prevent entanglement during graft passage later in the case.

Type III Tears: Reconstruction With Remnant Tensioning

The previously discussed techniques have the goals of preserving as much native ligament remnant as possible, approximating the ligament remnant towards the femoral wall, and promoting healing of the ligament. In some cases, however, the ligament remnant is too short for healing (Figure 5A). Although the ligament cannot be approximated to the femoral wall in these cases, there is still an argument for ACL preservation, as was discussed in the first article of this series.

If the ligament length is between 25% and 75% of the native tissue length, the senior author performs a remnant tensioning technique.

Type IV Tears: Reconstruction With Remnant Preservation

Finally, in some cases, the distal remnant is small or the tissue quality in the largest part of the remnant is poor, and after debriding back to good tissue quality, only 10% to 25% of the native tissue length is left (Figure 6A). In these cases, the remnant is preserved, however, tensioning of the remnant with sutures is usually not necessary for the prevention of cyclops lesions. Nonetheless, it is important to debride the parts of the remnant ligament with poor tissue quality as mop-end patterns of the remnant may increase the chance of these lesions (Figure 6B).

In this situation, any of the standard ACL reconstruction techniques can be performed with simple attention being paid to preserving what is left of the tibial insertion site. At the very least, the small insertion remnant guides the anatomic placement of the graft, and prevents egress of joint fluid into the tibial tunnel and could minimize tunnel widening.

Type V Tears: Primary Repair

Finally, in some patients a soft tissue avulsion (Figure 7A) or bony avulsion of the distal attachment of the ACL can be seen. Both injuries are relatively rare, although bony avulsions are frequently seen in children, especially those younger than 12 years old. In these cases, the same techniques and theory that are applied to proximal avulsion type tears can be used and applied to distal avulsion type tears.

First, No. 2 FiberWire sutures are passed from proximal towards the distal end of the ligament in the anteromedial bundle, and the same process is then repeated for No. 2 TigerWire sutures for the posterolateral bundle. Then both sutures are exited at the distal avulsed end at the locations of the anteromedial and posterolateral footprints (Figure 7B). A 2.4-mm ACL guide wire and a Ninitol wire are used to drill 2 tunnels from the tibia towards the tibial footprint. The repair sutures are then retrieved through both tunnels (Figure 7C) and the sutures are tied distally over a ligament button after cycling of the knee (Figure 7D). This technique is very useful for soft tissue avulsions, or when there are only small flecks of bone or when the avulsed bone is significantly comminuted. If a large bony avulsion fragment is present, this technique can also be applied with some modification, although there have been multiple other techniques described in the literature that work well in this situation including fixation with screw and washer, or with suture anchors.

Complex Tear or Poor Tissue Quality: Reconstruction

In some cases, the tissue quality is poor, or the ligament has complex or multiple tears. Essentially, in these cases, there is nothing to preserve and a standard reconstruction approach is performed in these cases.

Conclusion

The uniform gold standard for all ACL tear types is currently primary reconstruction. However, several disadvantages of ACL reconstruction exist, while there are multiple advantages to the concept of ACL preservation. In this surgical technique article, we have discussed our tear type classification and the recommended surgical techniques for each. With this treatment algorithm, which is based on tear location and tissue quality, an optimal and minimally invasive treatment can be chosen for each individual patient. Future studies are needed to compare and contrast these treatments with the current gold standard of ACL reconstruction.

Am J Orthop. 2016;45(7):E406-E414. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Musculoskeletal allografts are becoming increasingly accepted as a viable alternative to autografts in a variety of orthopedic procedures. A 2006 American Orthopaedic Society for Sports Medicine (AOSSM) survey indicated that 86% of the participating 365 orthopedic surgeons use allografts in their practice.¹ Although the overwhelming majority of orthopedic surgeons use allografts, they share common concerns, including safety, tissue integrity, and biologic incorporation. It is essential for the orthopedic surgeon to understand the current standards of tissue banking, risks and benefits related to the use of allografts, and common indications for safe use in clinical practice. This article reviews the current status of musculoskeletal allografts, including tissue procurement and processing, infections, complications, and specific uses tailored to ligament reconstruction.

Donor Bank, Processing, Sterilization, and Regulation

In the United States, the American Association of Tissue Banks (AATB) is responsible for establishing the standards for more than 100 accredited tissue banks. These tissue banks recover tissue from approximately 30,000 donors annually and account for an estimated 90% of the available musculoskeletal allografts used in the United States. While not all tissue banks are accredited by the AATB, all are required to register with the Food and Drug Administration (FDA), which allows for unannounced inspections of any facility. Facilities are required to abide by the FDA-implemented Current Good Tissue Practices (CGTP), which encompasses regulations on all donor tissue collected after May 2005 to help prevent the transmission of communicable diseases. The FDA released an updated draft in January 2009 that emphasizes safe practices and regulations spanning from environmental control to specific equipment.²

The safety of a transplanted allograft tissue begins within the tissue bank. Donor screening and testing is the first step in reducing the risk of transmission. Screening consists of collecting medical and social history from the family and any healthcare resources to assess the eligibility of the donor. If prior blood donations or autopsy information is available, that information is scrutinized. Donor tissue undergoes nucleic acid testing (NAT), which is required by both the AATB and FDA. All donor tissue must be screened for both types of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), treponema pallidum, and human transmissible spongiform encephalopathies.³ NAT of donor tissue effectively reduces the risk of viral transmission. Additionally, routine preprocessing swabs for bacterial and fungal cultures are performed, although the sensitivity of these cultures ranges from 78% to 92%.⁴

After donor screening and testing, allograft tissues are usually obtained under aseptic conditions, though this is not FDA-required.⁵ Once procured, the tissue undergoes sterilization. Currently, there is no standard method ubiquitous to all tissue banks, nor does the FDA require a specific method. Rather, the FDA and AATB require tissue banks to validate their sterilization process and provide supporting data. The goal of sterilization is to inactivate viruses and eradicate bacteria while maintaining the biological and mechanical properties of the tissue. The AATB requires a Sterility Assurance Level (SAL) of 10^-6, meaning there is no more than one in a million chance that a nonviral viable microbe exists on or within the tissue. Sterilization techniques may include both radiation and a variety of chemical reagents. Gamma irradiation is a commonly used method of sterilizing soft tissue allografts, although some studies indicate that it is detrimental to tissue biology.⁶ Newer methods of sterilization are being tested, one of which includes carbon dioxide in combination with antioxidants and irradiation. Bui and colleagues⁷ directly compared the biomechanical and histological properties of allograft tissue after either the standard 25 kGy gamma irradiation or supercritical carbon dioxide techniques. Although there is no histological difference, the samples treated with supercritical carbon dioxide had less biomechanical damage.⁷ Finally, the terminally sterilized allograft tissue is frozen to temperatures between -40°C and -80°C.⁵

Infections

One major concern of allografts is the risk of disease transmission. While numerous studies have investigated the incidence of bacterial infection following transplantation of allograft tissue, there are challenges associated with differentiating common postoperative infections from ones directly associated with the transmission of bacteria within the graft. There is a wide array of reported incidences of infection in the literature, from the Tomford and colleagues⁸ 1981 study that reported a 6.9% rateto the 2001 study by Munting and colleagues,⁹ who reported 0% in their series. Multiple confounding variables exist, such as possible contamination during handling of an otherwise noncontaminated or properly sterilized allograft with inappropriate inclusion of all postoperative infections. In contrast, recognizing viral transmission has been somewhat easier, although reporting of these incidences has been variable in the past. In either case, there is no accredited reporting system for infections related to allografts.

Bacterial Transmission

Clostridium species. Clostridium species are commonly found among intestinal flora. There is a general consensus that between 24 to 48 hours after death intestinal flora transmigrates into the surrounding tissue and blood. Therefore, a commonly accepted recommendation is that cadaveric tissue needs to be excised prior to 24 hours postmortem.¹⁰

In 2001, a 23-year-old man underwent reconstructive knee surgery with a femoral condyle allograft. A few days after surgery, he became septic and ultimately died from the infection. Clostridium sordellii was cultured from the tissue. Several days later, a 17-year-old boy underwent reconstructive knee surgery with a fresh femoral condyle and frozen meniscus from the same donor. Twenty-four hours after surgery, he developed a fever and was readmitted a week later for presumed infection and treated effectively with penicillin and ampicillin/sulbactam. Tissue from the same cadaveric donor had been transplanted into 7 other patients without reports of infection. In a 2002 Centers for Disease Control and Prevention (CDC) update report,¹¹ there were 26 total bacterial cases from allografts and 13 cases were attributed to Clostridium. Malinin and colleagues¹⁰ reviewed 795 consecutive cadaveric donors and found that 64 (8.1%) had positive cultures for Clostridia. Of all the positive cultures for Clostridia, 81.3% had positive blood cultures, 57.8% had positive bone marrow aspirate cultures, and 46.9% had positive tissue cultures. They concluded that multiple cultures are required for cadaveric tissue donors in order to reach a higher sensitivity for Clostridial contamination, and these should be done routinely to guide the sterilization process.

Strep species. In 2003, a 17-year-old boy underwent anterior cruciate ligament (ACL) reconstruction with a patellar tendon allograft.¹² About 1 week later, he was admitted for signs of infection and received intravenous antibiotics. He required surgical debridement, and intraoperative cultures grew Group A Streptococcus (GAS) that was also identified in the postmortem donor cultures. The tissues underwent processing in an antimicrobial solution and postprocessing cultures were negative for bacteria, but they were not sterilized. Tissues from this donor had been implanted in 5 other patients without report of infection. Following this event, recommendations have been made for prompt rejection of tissue with cultures positive for GAS, unless a sterilizing procedure is used.

Other bacteria. According to the 2002 CDC update, 11 of the 26 cases of bacterial infection reported to the agency were a combination of gram-negative bacilli, polymicrobial flora, or culture negative.¹¹

Viral Transmission

The most effective way to prevent transmission of a viral disease from allografts is thorough donor screening. Since the AATB implemented NAT in 2005 for HIV and HCV, there have been no reported cases of transmission.³ Even prior to this, regular blood screening along with social questionnaires completed by donors or donor families eliminated high-risk donors and significantly decreased the rate of transmission.

Human Immunodeficiency Virus. The first reported case of HIV transmission via implantation of allograft was in 1988. Further investigation revealed that there were 8 transmissions between 1984 and 1986, when routine screening of donors had not yet been implemented. The last reported case of HIV transmission occurred in 1996 with an untested donor.¹³Hepatitis C Virus. There are several reported cases of HCV transmission that occurred where the donors initially tested negative for HCV. In one case, 40 allografts from the same donor were transplanted over a period of nearly 2 years. This resulted in at least 8 patients being infected with HCV.¹⁴ Another case of HCV transmission was reported in 2005 after a patient developed acute HCV 6 weeks after transplantation of a patellar tendon allograft. Further investigation revealed that there had been 3 additional cases over a year from the same donor. Researchers determined that if the initial case had been reported, at least 3 transmissions could have been prevented.¹⁵Human T-cell Lymphotropic Virus (HTLV).The first reported transmission of HTLV was in 1991. This was reported in an asymptomatic patient who received a femoral head allograft from a donor who had been previously infected via a blood transfusion.¹⁶Zika virus. With recent outbreaks of the Zika virus, the FDA recently released recommendations regarding the screening and deferral of donors, mainly for blood transfusion. Orthopedists should take into consideration the potential for transmission through allografts. The FDA states that all potential donors should be screened for Zika virus using questionnaires and whole blood tests. Symptomatic donors are deferred at least 4 weeks following resolution of symptoms. While this is a recent recommendation from the FDA, orthopedists must be cognizant of the potential harms from this unfamiliar and evolving situation.¹⁷

Graft Specifics

Anterior Cruciate Ligament

ACL reconstruction is one of the most commonly performed surgeries by orthopedic surgeons, with an estimated 200,000 reconstructions per year.¹⁸Despite the popularity of this surgery, controversies remain regarding the optimal graft for reconstruction.^19,20 One would provide adequate strength, be readily available, not elicit an immunologic response from the host, rapidly incorporate, elicit low morbidity, and vascularize early. Current options include both autografts and allografts. Common autograft options include patellar bone-tendon-bone (PBTB), hamstrings tendon, quadriceps tendon, and iliotibial band. PBTB autograft remains a common choice among orthopedic surgeons, as it allows early incorporation of the graft into bone and eliminates immune rejection. However, donor site morbidity, including anterior knee pain, weakness of knee extension, joint stiffness, increased postoperative pain, and iatrogenic patella fractures, have been reported in the literature.²¹ Commonly used allograft options include donor bone-patellar tendon-bone, quadriceps tendon, Achilles tendon, anterior and posterior tibialis tendons, hamstring tendons, and iliotibial band. Allografts provide the advantage of avoiding donor site morbidity, being readily available, allowing for shorter operative times, and providing lower postoperative pain compared to autografts, although they carry the risk of disease transmission, rejection, and slower incorporation into bone.^22-27

Autograft donor site morbidities. One of the general disadvantages of autografts is the donor site morbidity associated with harvesting the grafts. In specific, PBTB grafts allow for bony blocks on both ends of the graft to incorporate into the host bone. However, this technique comes with the risk of disrupting the extensor mechanism.^28,29 Milankov and colleagues³⁰ published a retrospective review of over 2000 ACLs using autologous PBTB graft. They noted a 0.45% incidence of patella fracture and 0.18% patellar tendon rupture.³⁰ Others have reported that intraoperative repair of the patellar tendon after tendon harvesting can increase infrapatellar fibrosis, thus increasing the risk for stiffness.^31-33

Hamstring autografts include the semitendinosus and the gracilis tendons. The harvesting process is technically demanding and can be complicated by inadvertent amputation of the tendons, making the graft unsuitable for reconstructive purposes.³⁴ Additionally, several reports have identified persistent numbness and hyperesthesia following hamstring harvesting due to iatrogenic injury to the prepatellar branches of the saphenous nerve.^35,36A comprehensive review by Slone and colleagues³⁷ reported comparable functional outcomes with quadriceps tendon autograft compared to PBTB; however, this comes with the risk of postoperative hematoma formation and the potential for thigh compartment syndrome.

Biology and Biomechanics of Allografts

One of the major disadvantages of allografts is the reduced ability to incorporate into the host tissue. Several in vitro and animal studies have suggested that allografts incorporate in the host slower than autografts.^24,26,38 Early studies by Jackson and colleagues²⁴ on goat models demonstrated that allografts and autografts have similar structural and biological properties initially, but allografts display significantly slower incorporation into the host tissue at 6 months. Histologically, allografts demonstrated lower revascularization, a smaller cross-sectional area, and a prolonged inflammatory response at 6 months postoperatively.^24,39,40 Muramatsu and colleagues⁴¹ further showed through the use of magnetic resonance imaging a slower rate of revascularization of allografts over 2 years post-reconstruction.

Given the delayed biologic incorporation of allografts, studies have identified a lower strength-to-failure rate in the early postoperative period compared to autografts. An animal model study by Nikolaou and colleagues³⁸ showed that the strength of allografts was lower for up to 2 years following surgery. Additional biomechanical studies demonstrated that allografts were nearly 75% structurally weaker compared to autografts at 1 year following surgery.⁴²

Acknowledging these limitations, one should use caution when choosing to use an allograft or starting aggressive early rehabilitation after an allograft reconstruction, especially in athletes and young patients.

Clinical Outcomes

Although in vitro studies demonstrate inferior strength and delayed incorporation of allografts in the early postoperative period, there is still controversy surrounding the clinical and functional outcomes. Numerous studies have identified allografts as a viable option for ACL reconstruction, with similar reported patient satisfaction scores compared to autografts.^43,44

The MOON Consortium recently published a prospective study of nearly 2500 subjects looking to identify risk factors for failure of ACL reconstruction. The study found that allografts had an odds ratio for failure 5.2 times that of PBTB autografts, correlating this factor to an increased re-tear rate of 6.9% in the allograft group compared to 3.2% in the PBTB group (P < .01).⁴⁵ The elevated risk is more prevalent in younger patients, especially athletic teenagers. This issue has been reiterated in multiple studies.^45-50A meta-analysis by Hu and colleagues²³ identified 9 studies, either randomized control trials or prospective cohort studies, that looked at clinical outcomes between the different graft choices. They showed there was no significant difference between graft options in terms of instrumental laxity (P = .59), Lachman test (P = .41), pivot shift test (P = .88), and multiple functional outcome scores, including the International Knee Documentation Committee (IKDC), Lysholm, and Tegner scores.^23,51-59Processing and sterilization techniques are thought to play a role in allograft failure. Guo and other researchers have demonstrated a significantly higher rate of failure for patients who received gamma-irradiated allografts compared to fresh frozen allografts.^23,58-64 With improved sterilization techniques and a strict selection process of donors, gamma radiation has fallen out of favor to protect the biological characteristics of the tissue graft.^5,65,66Several factors need to be considered when selecting between allograft or autograft tissue for ligamentous reconstruction. The selection must be balanced between the surgeon’s experience, patient and surgeon preferences, age of the patient, level of physical activity, primary or revision surgical setting, multiligamentous failure, geographical availability of donor grafts, and economical factors.

Medial Patellofemoral Ligament Reconstruction

Another relatively recent application for allografts has been described for the reconstruction of the medial patellofemoral ligament (MPFL) in recurrent lateral patellar dislocations.^67-74

Typically, MPFL reconstructions make use of autografts, including quadriceps tendon, patellar tendon, and hamstring ligaments. However, allografts have the potential to limit postoperative donor site morbidity and to allow a faster rehabilitation.^75,76 Allografts include semitendinosus, gracilis, anterior tibialis, posterior tibialis, and quadriceps tendons.

Calvo Rodríguez and colleagues⁷⁶ performed a retrospective review in 2015 comparing allografts to autografts for MPFL reconstruction with respect to postoperative knee function and re-dislocation rates. Among the collective 28 patients, there was no difference in overall functional scores or dislocation rates between the grafts. Although this was a retrospective review and had a small number of subjects, the findings identify allografts as a reliable graft option for MPFL reconstruction.⁷⁶While there has been a surge of interest in techniques for MPFL reconstruction, there is limited research available regarding the superiority of allografts compared to autografts. For this specific application, it seems that clinical outcomes correlate more to adequate stabilization of the patellofemoral joint than to the type of graft used.^77,78 Future research should be dedicated to prospective randomized control trials to delineate any disadvantages to using allografts for MPFL reconstruction.

Discussion

Musculoskeletal allografts are gaining popularity for ligamentous reconstruction as their safety and efficacy continue to improve. With the great majority of tissue banks being accredited by the AATB and specific regulations such as NAT screening becoming common practice, infection rates and transmission of diseases have become incredibly rare. However, a thorough consideration needs to be taken into account when choosing between autograft and allograft on a case-by-case basis (Table).

Musculoskeletal allografts are becoming increasingly accepted as a viable alternative to autografts in a variety of orthopedic procedures. A 2006 American Orthopaedic Society for Sports Medicine (AOSSM) survey indicated that 86% of the participating 365 orthopedic surgeons use allografts in their practice.¹ Although the overwhelming majority of orthopedic surgeons use allografts, they share common concerns, including safety, tissue integrity, and biologic incorporation. It is essential for the orthopedic surgeon to understand the current standards of tissue banking, risks and benefits related to the use of allografts, and common indications for safe use in clinical practice. This article reviews the current status of musculoskeletal allografts, including tissue procurement and processing, infections, complications, and specific uses tailored to ligament reconstruction.

Donor Bank, Processing, Sterilization, and Regulation

In the United States, the American Association of Tissue Banks (AATB) is responsible for establishing the standards for more than 100 accredited tissue banks. These tissue banks recover tissue from approximately 30,000 donors annually and account for an estimated 90% of the available musculoskeletal allografts used in the United States. While not all tissue banks are accredited by the AATB, all are required to register with the Food and Drug Administration (FDA), which allows for unannounced inspections of any facility. Facilities are required to abide by the FDA-implemented Current Good Tissue Practices (CGTP), which encompasses regulations on all donor tissue collected after May 2005 to help prevent the transmission of communicable diseases. The FDA released an updated draft in January 2009 that emphasizes safe practices and regulations spanning from environmental control to specific equipment.²

The safety of a transplanted allograft tissue begins within the tissue bank. Donor screening and testing is the first step in reducing the risk of transmission. Screening consists of collecting medical and social history from the family and any healthcare resources to assess the eligibility of the donor. If prior blood donations or autopsy information is available, that information is scrutinized. Donor tissue undergoes nucleic acid testing (NAT), which is required by both the AATB and FDA. All donor tissue must be screened for both types of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), treponema pallidum, and human transmissible spongiform encephalopathies.³ NAT of donor tissue effectively reduces the risk of viral transmission. Additionally, routine preprocessing swabs for bacterial and fungal cultures are performed, although the sensitivity of these cultures ranges from 78% to 92%.⁴

After donor screening and testing, allograft tissues are usually obtained under aseptic conditions, though this is not FDA-required.⁵ Once procured, the tissue undergoes sterilization. Currently, there is no standard method ubiquitous to all tissue banks, nor does the FDA require a specific method. Rather, the FDA and AATB require tissue banks to validate their sterilization process and provide supporting data. The goal of sterilization is to inactivate viruses and eradicate bacteria while maintaining the biological and mechanical properties of the tissue. The AATB requires a Sterility Assurance Level (SAL) of 10^-6, meaning there is no more than one in a million chance that a nonviral viable microbe exists on or within the tissue. Sterilization techniques may include both radiation and a variety of chemical reagents. Gamma irradiation is a commonly used method of sterilizing soft tissue allografts, although some studies indicate that it is detrimental to tissue biology.⁶ Newer methods of sterilization are being tested, one of which includes carbon dioxide in combination with antioxidants and irradiation. Bui and colleagues⁷ directly compared the biomechanical and histological properties of allograft tissue after either the standard 25 kGy gamma irradiation or supercritical carbon dioxide techniques. Although there is no histological difference, the samples treated with supercritical carbon dioxide had less biomechanical damage.⁷ Finally, the terminally sterilized allograft tissue is frozen to temperatures between -40°C and -80°C.⁵

Infections

One major concern of allografts is the risk of disease transmission. While numerous studies have investigated the incidence of bacterial infection following transplantation of allograft tissue, there are challenges associated with differentiating common postoperative infections from ones directly associated with the transmission of bacteria within the graft. There is a wide array of reported incidences of infection in the literature, from the Tomford and colleagues⁸ 1981 study that reported a 6.9% rateto the 2001 study by Munting and colleagues,⁹ who reported 0% in their series. Multiple confounding variables exist, such as possible contamination during handling of an otherwise noncontaminated or properly sterilized allograft with inappropriate inclusion of all postoperative infections. In contrast, recognizing viral transmission has been somewhat easier, although reporting of these incidences has been variable in the past. In either case, there is no accredited reporting system for infections related to allografts.

Bacterial Transmission

Clostridium species. Clostridium species are commonly found among intestinal flora. There is a general consensus that between 24 to 48 hours after death intestinal flora transmigrates into the surrounding tissue and blood. Therefore, a commonly accepted recommendation is that cadaveric tissue needs to be excised prior to 24 hours postmortem.¹⁰

In 2001, a 23-year-old man underwent reconstructive knee surgery with a femoral condyle allograft. A few days after surgery, he became septic and ultimately died from the infection. Clostridium sordellii was cultured from the tissue. Several days later, a 17-year-old boy underwent reconstructive knee surgery with a fresh femoral condyle and frozen meniscus from the same donor. Twenty-four hours after surgery, he developed a fever and was readmitted a week later for presumed infection and treated effectively with penicillin and ampicillin/sulbactam. Tissue from the same cadaveric donor had been transplanted into 7 other patients without reports of infection. In a 2002 Centers for Disease Control and Prevention (CDC) update report,¹¹ there were 26 total bacterial cases from allografts and 13 cases were attributed to Clostridium. Malinin and colleagues¹⁰ reviewed 795 consecutive cadaveric donors and found that 64 (8.1%) had positive cultures for Clostridia. Of all the positive cultures for Clostridia, 81.3% had positive blood cultures, 57.8% had positive bone marrow aspirate cultures, and 46.9% had positive tissue cultures. They concluded that multiple cultures are required for cadaveric tissue donors in order to reach a higher sensitivity for Clostridial contamination, and these should be done routinely to guide the sterilization process.

Strep species. In 2003, a 17-year-old boy underwent anterior cruciate ligament (ACL) reconstruction with a patellar tendon allograft.¹² About 1 week later, he was admitted for signs of infection and received intravenous antibiotics. He required surgical debridement, and intraoperative cultures grew Group A Streptococcus (GAS) that was also identified in the postmortem donor cultures. The tissues underwent processing in an antimicrobial solution and postprocessing cultures were negative for bacteria, but they were not sterilized. Tissues from this donor had been implanted in 5 other patients without report of infection. Following this event, recommendations have been made for prompt rejection of tissue with cultures positive for GAS, unless a sterilizing procedure is used.

Other bacteria. According to the 2002 CDC update, 11 of the 26 cases of bacterial infection reported to the agency were a combination of gram-negative bacilli, polymicrobial flora, or culture negative.¹¹

Viral Transmission

The most effective way to prevent transmission of a viral disease from allografts is thorough donor screening. Since the AATB implemented NAT in 2005 for HIV and HCV, there have been no reported cases of transmission.³ Even prior to this, regular blood screening along with social questionnaires completed by donors or donor families eliminated high-risk donors and significantly decreased the rate of transmission.

Human Immunodeficiency Virus. The first reported case of HIV transmission via implantation of allograft was in 1988. Further investigation revealed that there were 8 transmissions between 1984 and 1986, when routine screening of donors had not yet been implemented. The last reported case of HIV transmission occurred in 1996 with an untested donor.¹³Hepatitis C Virus. There are several reported cases of HCV transmission that occurred where the donors initially tested negative for HCV. In one case, 40 allografts from the same donor were transplanted over a period of nearly 2 years. This resulted in at least 8 patients being infected with HCV.¹⁴ Another case of HCV transmission was reported in 2005 after a patient developed acute HCV 6 weeks after transplantation of a patellar tendon allograft. Further investigation revealed that there had been 3 additional cases over a year from the same donor. Researchers determined that if the initial case had been reported, at least 3 transmissions could have been prevented.¹⁵Human T-cell Lymphotropic Virus (HTLV).The first reported transmission of HTLV was in 1991. This was reported in an asymptomatic patient who received a femoral head allograft from a donor who had been previously infected via a blood transfusion.¹⁶Zika virus. With recent outbreaks of the Zika virus, the FDA recently released recommendations regarding the screening and deferral of donors, mainly for blood transfusion. Orthopedists should take into consideration the potential for transmission through allografts. The FDA states that all potential donors should be screened for Zika virus using questionnaires and whole blood tests. Symptomatic donors are deferred at least 4 weeks following resolution of symptoms. While this is a recent recommendation from the FDA, orthopedists must be cognizant of the potential harms from this unfamiliar and evolving situation.¹⁷

Graft Specifics

Anterior Cruciate Ligament

ACL reconstruction is one of the most commonly performed surgeries by orthopedic surgeons, with an estimated 200,000 reconstructions per year.¹⁸Despite the popularity of this surgery, controversies remain regarding the optimal graft for reconstruction.^19,20 One would provide adequate strength, be readily available, not elicit an immunologic response from the host, rapidly incorporate, elicit low morbidity, and vascularize early. Current options include both autografts and allografts. Common autograft options include patellar bone-tendon-bone (PBTB), hamstrings tendon, quadriceps tendon, and iliotibial band. PBTB autograft remains a common choice among orthopedic surgeons, as it allows early incorporation of the graft into bone and eliminates immune rejection. However, donor site morbidity, including anterior knee pain, weakness of knee extension, joint stiffness, increased postoperative pain, and iatrogenic patella fractures, have been reported in the literature.²¹ Commonly used allograft options include donor bone-patellar tendon-bone, quadriceps tendon, Achilles tendon, anterior and posterior tibialis tendons, hamstring tendons, and iliotibial band. Allografts provide the advantage of avoiding donor site morbidity, being readily available, allowing for shorter operative times, and providing lower postoperative pain compared to autografts, although they carry the risk of disease transmission, rejection, and slower incorporation into bone.^22-27

Autograft donor site morbidities. One of the general disadvantages of autografts is the donor site morbidity associated with harvesting the grafts. In specific, PBTB grafts allow for bony blocks on both ends of the graft to incorporate into the host bone. However, this technique comes with the risk of disrupting the extensor mechanism.^28,29 Milankov and colleagues³⁰ published a retrospective review of over 2000 ACLs using autologous PBTB graft. They noted a 0.45% incidence of patella fracture and 0.18% patellar tendon rupture.³⁰ Others have reported that intraoperative repair of the patellar tendon after tendon harvesting can increase infrapatellar fibrosis, thus increasing the risk for stiffness.^31-33

Hamstring autografts include the semitendinosus and the gracilis tendons. The harvesting process is technically demanding and can be complicated by inadvertent amputation of the tendons, making the graft unsuitable for reconstructive purposes.³⁴ Additionally, several reports have identified persistent numbness and hyperesthesia following hamstring harvesting due to iatrogenic injury to the prepatellar branches of the saphenous nerve.^35,36A comprehensive review by Slone and colleagues³⁷ reported comparable functional outcomes with quadriceps tendon autograft compared to PBTB; however, this comes with the risk of postoperative hematoma formation and the potential for thigh compartment syndrome.

Biology and Biomechanics of Allografts

One of the major disadvantages of allografts is the reduced ability to incorporate into the host tissue. Several in vitro and animal studies have suggested that allografts incorporate in the host slower than autografts.^24,26,38 Early studies by Jackson and colleagues²⁴ on goat models demonstrated that allografts and autografts have similar structural and biological properties initially, but allografts display significantly slower incorporation into the host tissue at 6 months. Histologically, allografts demonstrated lower revascularization, a smaller cross-sectional area, and a prolonged inflammatory response at 6 months postoperatively.^24,39,40 Muramatsu and colleagues⁴¹ further showed through the use of magnetic resonance imaging a slower rate of revascularization of allografts over 2 years post-reconstruction.

Given the delayed biologic incorporation of allografts, studies have identified a lower strength-to-failure rate in the early postoperative period compared to autografts. An animal model study by Nikolaou and colleagues³⁸ showed that the strength of allografts was lower for up to 2 years following surgery. Additional biomechanical studies demonstrated that allografts were nearly 75% structurally weaker compared to autografts at 1 year following surgery.⁴²

Acknowledging these limitations, one should use caution when choosing to use an allograft or starting aggressive early rehabilitation after an allograft reconstruction, especially in athletes and young patients.

Clinical Outcomes

Although in vitro studies demonstrate inferior strength and delayed incorporation of allografts in the early postoperative period, there is still controversy surrounding the clinical and functional outcomes. Numerous studies have identified allografts as a viable option for ACL reconstruction, with similar reported patient satisfaction scores compared to autografts.^43,44

The MOON Consortium recently published a prospective study of nearly 2500 subjects looking to identify risk factors for failure of ACL reconstruction. The study found that allografts had an odds ratio for failure 5.2 times that of PBTB autografts, correlating this factor to an increased re-tear rate of 6.9% in the allograft group compared to 3.2% in the PBTB group (P < .01).⁴⁵ The elevated risk is more prevalent in younger patients, especially athletic teenagers. This issue has been reiterated in multiple studies.^45-50A meta-analysis by Hu and colleagues²³ identified 9 studies, either randomized control trials or prospective cohort studies, that looked at clinical outcomes between the different graft choices. They showed there was no significant difference between graft options in terms of instrumental laxity (P = .59), Lachman test (P = .41), pivot shift test (P = .88), and multiple functional outcome scores, including the International Knee Documentation Committee (IKDC), Lysholm, and Tegner scores.^23,51-59Processing and sterilization techniques are thought to play a role in allograft failure. Guo and other researchers have demonstrated a significantly higher rate of failure for patients who received gamma-irradiated allografts compared to fresh frozen allografts.^23,58-64 With improved sterilization techniques and a strict selection process of donors, gamma radiation has fallen out of favor to protect the biological characteristics of the tissue graft.^5,65,66Several factors need to be considered when selecting between allograft or autograft tissue for ligamentous reconstruction. The selection must be balanced between the surgeon’s experience, patient and surgeon preferences, age of the patient, level of physical activity, primary or revision surgical setting, multiligamentous failure, geographical availability of donor grafts, and economical factors.

Medial Patellofemoral Ligament Reconstruction

Another relatively recent application for allografts has been described for the reconstruction of the medial patellofemoral ligament (MPFL) in recurrent lateral patellar dislocations.^67-74

Typically, MPFL reconstructions make use of autografts, including quadriceps tendon, patellar tendon, and hamstring ligaments. However, allografts have the potential to limit postoperative donor site morbidity and to allow a faster rehabilitation.^75,76 Allografts include semitendinosus, gracilis, anterior tibialis, posterior tibialis, and quadriceps tendons.

Calvo Rodríguez and colleagues⁷⁶ performed a retrospective review in 2015 comparing allografts to autografts for MPFL reconstruction with respect to postoperative knee function and re-dislocation rates. Among the collective 28 patients, there was no difference in overall functional scores or dislocation rates between the grafts. Although this was a retrospective review and had a small number of subjects, the findings identify allografts as a reliable graft option for MPFL reconstruction.⁷⁶While there has been a surge of interest in techniques for MPFL reconstruction, there is limited research available regarding the superiority of allografts compared to autografts. For this specific application, it seems that clinical outcomes correlate more to adequate stabilization of the patellofemoral joint than to the type of graft used.^77,78 Future research should be dedicated to prospective randomized control trials to delineate any disadvantages to using allografts for MPFL reconstruction.

Discussion

Musculoskeletal allografts are gaining popularity for ligamentous reconstruction as their safety and efficacy continue to improve. With the great majority of tissue banks being accredited by the AATB and specific regulations such as NAT screening becoming common practice, infection rates and transmission of diseases have become incredibly rare. However, a thorough consideration needs to be taken into account when choosing between autograft and allograft on a case-by-case basis (Table).

Musculoskeletal allografts are becoming increasingly accepted as a viable alternative to autografts in a variety of orthopedic procedures. A 2006 American Orthopaedic Society for Sports Medicine (AOSSM) survey indicated that 86% of the participating 365 orthopedic surgeons use allografts in their practice.¹ Although the overwhelming majority of orthopedic surgeons use allografts, they share common concerns, including safety, tissue integrity, and biologic incorporation. It is essential for the orthopedic surgeon to understand the current standards of tissue banking, risks and benefits related to the use of allografts, and common indications for safe use in clinical practice. This article reviews the current status of musculoskeletal allografts, including tissue procurement and processing, infections, complications, and specific uses tailored to ligament reconstruction.

Donor Bank, Processing, Sterilization, and Regulation

In the United States, the American Association of Tissue Banks (AATB) is responsible for establishing the standards for more than 100 accredited tissue banks. These tissue banks recover tissue from approximately 30,000 donors annually and account for an estimated 90% of the available musculoskeletal allografts used in the United States. While not all tissue banks are accredited by the AATB, all are required to register with the Food and Drug Administration (FDA), which allows for unannounced inspections of any facility. Facilities are required to abide by the FDA-implemented Current Good Tissue Practices (CGTP), which encompasses regulations on all donor tissue collected after May 2005 to help prevent the transmission of communicable diseases. The FDA released an updated draft in January 2009 that emphasizes safe practices and regulations spanning from environmental control to specific equipment.²

The safety of a transplanted allograft tissue begins within the tissue bank. Donor screening and testing is the first step in reducing the risk of transmission. Screening consists of collecting medical and social history from the family and any healthcare resources to assess the eligibility of the donor. If prior blood donations or autopsy information is available, that information is scrutinized. Donor tissue undergoes nucleic acid testing (NAT), which is required by both the AATB and FDA. All donor tissue must be screened for both types of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), treponema pallidum, and human transmissible spongiform encephalopathies.³ NAT of donor tissue effectively reduces the risk of viral transmission. Additionally, routine preprocessing swabs for bacterial and fungal cultures are performed, although the sensitivity of these cultures ranges from 78% to 92%.⁴

After donor screening and testing, allograft tissues are usually obtained under aseptic conditions, though this is not FDA-required.⁵ Once procured, the tissue undergoes sterilization. Currently, there is no standard method ubiquitous to all tissue banks, nor does the FDA require a specific method. Rather, the FDA and AATB require tissue banks to validate their sterilization process and provide supporting data. The goal of sterilization is to inactivate viruses and eradicate bacteria while maintaining the biological and mechanical properties of the tissue. The AATB requires a Sterility Assurance Level (SAL) of 10^-6, meaning there is no more than one in a million chance that a nonviral viable microbe exists on or within the tissue. Sterilization techniques may include both radiation and a variety of chemical reagents. Gamma irradiation is a commonly used method of sterilizing soft tissue allografts, although some studies indicate that it is detrimental to tissue biology.⁶ Newer methods of sterilization are being tested, one of which includes carbon dioxide in combination with antioxidants and irradiation. Bui and colleagues⁷ directly compared the biomechanical and histological properties of allograft tissue after either the standard 25 kGy gamma irradiation or supercritical carbon dioxide techniques. Although there is no histological difference, the samples treated with supercritical carbon dioxide had less biomechanical damage.⁷ Finally, the terminally sterilized allograft tissue is frozen to temperatures between -40°C and -80°C.⁵

Infections

One major concern of allografts is the risk of disease transmission. While numerous studies have investigated the incidence of bacterial infection following transplantation of allograft tissue, there are challenges associated with differentiating common postoperative infections from ones directly associated with the transmission of bacteria within the graft. There is a wide array of reported incidences of infection in the literature, from the Tomford and colleagues⁸ 1981 study that reported a 6.9% rateto the 2001 study by Munting and colleagues,⁹ who reported 0% in their series. Multiple confounding variables exist, such as possible contamination during handling of an otherwise noncontaminated or properly sterilized allograft with inappropriate inclusion of all postoperative infections. In contrast, recognizing viral transmission has been somewhat easier, although reporting of these incidences has been variable in the past. In either case, there is no accredited reporting system for infections related to allografts.

Bacterial Transmission

Clostridium species. Clostridium species are commonly found among intestinal flora. There is a general consensus that between 24 to 48 hours after death intestinal flora transmigrates into the surrounding tissue and blood. Therefore, a commonly accepted recommendation is that cadaveric tissue needs to be excised prior to 24 hours postmortem.¹⁰

In 2001, a 23-year-old man underwent reconstructive knee surgery with a femoral condyle allograft. A few days after surgery, he became septic and ultimately died from the infection. Clostridium sordellii was cultured from the tissue. Several days later, a 17-year-old boy underwent reconstructive knee surgery with a fresh femoral condyle and frozen meniscus from the same donor. Twenty-four hours after surgery, he developed a fever and was readmitted a week later for presumed infection and treated effectively with penicillin and ampicillin/sulbactam. Tissue from the same cadaveric donor had been transplanted into 7 other patients without reports of infection. In a 2002 Centers for Disease Control and Prevention (CDC) update report,¹¹ there were 26 total bacterial cases from allografts and 13 cases were attributed to Clostridium. Malinin and colleagues¹⁰ reviewed 795 consecutive cadaveric donors and found that 64 (8.1%) had positive cultures for Clostridia. Of all the positive cultures for Clostridia, 81.3% had positive blood cultures, 57.8% had positive bone marrow aspirate cultures, and 46.9% had positive tissue cultures. They concluded that multiple cultures are required for cadaveric tissue donors in order to reach a higher sensitivity for Clostridial contamination, and these should be done routinely to guide the sterilization process.

Strep species. In 2003, a 17-year-old boy underwent anterior cruciate ligament (ACL) reconstruction with a patellar tendon allograft.¹² About 1 week later, he was admitted for signs of infection and received intravenous antibiotics. He required surgical debridement, and intraoperative cultures grew Group A Streptococcus (GAS) that was also identified in the postmortem donor cultures. The tissues underwent processing in an antimicrobial solution and postprocessing cultures were negative for bacteria, but they were not sterilized. Tissues from this donor had been implanted in 5 other patients without report of infection. Following this event, recommendations have been made for prompt rejection of tissue with cultures positive for GAS, unless a sterilizing procedure is used.

Other bacteria. According to the 2002 CDC update, 11 of the 26 cases of bacterial infection reported to the agency were a combination of gram-negative bacilli, polymicrobial flora, or culture negative.¹¹

Viral Transmission

The most effective way to prevent transmission of a viral disease from allografts is thorough donor screening. Since the AATB implemented NAT in 2005 for HIV and HCV, there have been no reported cases of transmission.³ Even prior to this, regular blood screening along with social questionnaires completed by donors or donor families eliminated high-risk donors and significantly decreased the rate of transmission.

Human Immunodeficiency Virus. The first reported case of HIV transmission via implantation of allograft was in 1988. Further investigation revealed that there were 8 transmissions between 1984 and 1986, when routine screening of donors had not yet been implemented. The last reported case of HIV transmission occurred in 1996 with an untested donor.¹³Hepatitis C Virus. There are several reported cases of HCV transmission that occurred where the donors initially tested negative for HCV. In one case, 40 allografts from the same donor were transplanted over a period of nearly 2 years. This resulted in at least 8 patients being infected with HCV.¹⁴ Another case of HCV transmission was reported in 2005 after a patient developed acute HCV 6 weeks after transplantation of a patellar tendon allograft. Further investigation revealed that there had been 3 additional cases over a year from the same donor. Researchers determined that if the initial case had been reported, at least 3 transmissions could have been prevented.¹⁵Human T-cell Lymphotropic Virus (HTLV).The first reported transmission of HTLV was in 1991. This was reported in an asymptomatic patient who received a femoral head allograft from a donor who had been previously infected via a blood transfusion.¹⁶Zika virus. With recent outbreaks of the Zika virus, the FDA recently released recommendations regarding the screening and deferral of donors, mainly for blood transfusion. Orthopedists should take into consideration the potential for transmission through allografts. The FDA states that all potential donors should be screened for Zika virus using questionnaires and whole blood tests. Symptomatic donors are deferred at least 4 weeks following resolution of symptoms. While this is a recent recommendation from the FDA, orthopedists must be cognizant of the potential harms from this unfamiliar and evolving situation.¹⁷

Graft Specifics

Anterior Cruciate Ligament

ACL reconstruction is one of the most commonly performed surgeries by orthopedic surgeons, with an estimated 200,000 reconstructions per year.¹⁸Despite the popularity of this surgery, controversies remain regarding the optimal graft for reconstruction.^19,20 One would provide adequate strength, be readily available, not elicit an immunologic response from the host, rapidly incorporate, elicit low morbidity, and vascularize early. Current options include both autografts and allografts. Common autograft options include patellar bone-tendon-bone (PBTB), hamstrings tendon, quadriceps tendon, and iliotibial band. PBTB autograft remains a common choice among orthopedic surgeons, as it allows early incorporation of the graft into bone and eliminates immune rejection. However, donor site morbidity, including anterior knee pain, weakness of knee extension, joint stiffness, increased postoperative pain, and iatrogenic patella fractures, have been reported in the literature.²¹ Commonly used allograft options include donor bone-patellar tendon-bone, quadriceps tendon, Achilles tendon, anterior and posterior tibialis tendons, hamstring tendons, and iliotibial band. Allografts provide the advantage of avoiding donor site morbidity, being readily available, allowing for shorter operative times, and providing lower postoperative pain compared to autografts, although they carry the risk of disease transmission, rejection, and slower incorporation into bone.^22-27

Autograft donor site morbidities. One of the general disadvantages of autografts is the donor site morbidity associated with harvesting the grafts. In specific, PBTB grafts allow for bony blocks on both ends of the graft to incorporate into the host bone. However, this technique comes with the risk of disrupting the extensor mechanism.^28,29 Milankov and colleagues³⁰ published a retrospective review of over 2000 ACLs using autologous PBTB graft. They noted a 0.45% incidence of patella fracture and 0.18% patellar tendon rupture.³⁰ Others have reported that intraoperative repair of the patellar tendon after tendon harvesting can increase infrapatellar fibrosis, thus increasing the risk for stiffness.^31-33

Hamstring autografts include the semitendinosus and the gracilis tendons. The harvesting process is technically demanding and can be complicated by inadvertent amputation of the tendons, making the graft unsuitable for reconstructive purposes.³⁴ Additionally, several reports have identified persistent numbness and hyperesthesia following hamstring harvesting due to iatrogenic injury to the prepatellar branches of the saphenous nerve.^35,36A comprehensive review by Slone and colleagues³⁷ reported comparable functional outcomes with quadriceps tendon autograft compared to PBTB; however, this comes with the risk of postoperative hematoma formation and the potential for thigh compartment syndrome.

Biology and Biomechanics of Allografts

One of the major disadvantages of allografts is the reduced ability to incorporate into the host tissue. Several in vitro and animal studies have suggested that allografts incorporate in the host slower than autografts.^24,26,38 Early studies by Jackson and colleagues²⁴ on goat models demonstrated that allografts and autografts have similar structural and biological properties initially, but allografts display significantly slower incorporation into the host tissue at 6 months. Histologically, allografts demonstrated lower revascularization, a smaller cross-sectional area, and a prolonged inflammatory response at 6 months postoperatively.^24,39,40 Muramatsu and colleagues⁴¹ further showed through the use of magnetic resonance imaging a slower rate of revascularization of allografts over 2 years post-reconstruction.

Given the delayed biologic incorporation of allografts, studies have identified a lower strength-to-failure rate in the early postoperative period compared to autografts. An animal model study by Nikolaou and colleagues³⁸ showed that the strength of allografts was lower for up to 2 years following surgery. Additional biomechanical studies demonstrated that allografts were nearly 75% structurally weaker compared to autografts at 1 year following surgery.⁴²

Acknowledging these limitations, one should use caution when choosing to use an allograft or starting aggressive early rehabilitation after an allograft reconstruction, especially in athletes and young patients.

Clinical Outcomes

Although in vitro studies demonstrate inferior strength and delayed incorporation of allografts in the early postoperative period, there is still controversy surrounding the clinical and functional outcomes. Numerous studies have identified allografts as a viable option for ACL reconstruction, with similar reported patient satisfaction scores compared to autografts.^43,44

The MOON Consortium recently published a prospective study of nearly 2500 subjects looking to identify risk factors for failure of ACL reconstruction. The study found that allografts had an odds ratio for failure 5.2 times that of PBTB autografts, correlating this factor to an increased re-tear rate of 6.9% in the allograft group compared to 3.2% in the PBTB group (P < .01).⁴⁵ The elevated risk is more prevalent in younger patients, especially athletic teenagers. This issue has been reiterated in multiple studies.^45-50A meta-analysis by Hu and colleagues²³ identified 9 studies, either randomized control trials or prospective cohort studies, that looked at clinical outcomes between the different graft choices. They showed there was no significant difference between graft options in terms of instrumental laxity (P = .59), Lachman test (P = .41), pivot shift test (P = .88), and multiple functional outcome scores, including the International Knee Documentation Committee (IKDC), Lysholm, and Tegner scores.^23,51-59Processing and sterilization techniques are thought to play a role in allograft failure. Guo and other researchers have demonstrated a significantly higher rate of failure for patients who received gamma-irradiated allografts compared to fresh frozen allografts.^23,58-64 With improved sterilization techniques and a strict selection process of donors, gamma radiation has fallen out of favor to protect the biological characteristics of the tissue graft.^5,65,66Several factors need to be considered when selecting between allograft or autograft tissue for ligamentous reconstruction. The selection must be balanced between the surgeon’s experience, patient and surgeon preferences, age of the patient, level of physical activity, primary or revision surgical setting, multiligamentous failure, geographical availability of donor grafts, and economical factors.

Medial Patellofemoral Ligament Reconstruction

Another relatively recent application for allografts has been described for the reconstruction of the medial patellofemoral ligament (MPFL) in recurrent lateral patellar dislocations.^67-74

Typically, MPFL reconstructions make use of autografts, including quadriceps tendon, patellar tendon, and hamstring ligaments. However, allografts have the potential to limit postoperative donor site morbidity and to allow a faster rehabilitation.^75,76 Allografts include semitendinosus, gracilis, anterior tibialis, posterior tibialis, and quadriceps tendons.

Calvo Rodríguez and colleagues⁷⁶ performed a retrospective review in 2015 comparing allografts to autografts for MPFL reconstruction with respect to postoperative knee function and re-dislocation rates. Among the collective 28 patients, there was no difference in overall functional scores or dislocation rates between the grafts. Although this was a retrospective review and had a small number of subjects, the findings identify allografts as a reliable graft option for MPFL reconstruction.⁷⁶While there has been a surge of interest in techniques for MPFL reconstruction, there is limited research available regarding the superiority of allografts compared to autografts. For this specific application, it seems that clinical outcomes correlate more to adequate stabilization of the patellofemoral joint than to the type of graft used.^77,78 Future research should be dedicated to prospective randomized control trials to delineate any disadvantages to using allografts for MPFL reconstruction.

Discussion

Musculoskeletal allografts are gaining popularity for ligamentous reconstruction as their safety and efficacy continue to improve. With the great majority of tissue banks being accredited by the AATB and specific regulations such as NAT screening becoming common practice, infection rates and transmission of diseases have become incredibly rare. However, a thorough consideration needs to be taken into account when choosing between autograft and allograft on a case-by-case basis (Table).