The American Journal of Orthopedics

Restoring native kinematics of the knee has been a primary goal of anterior cruciate ligament (ACL) procedures. Double-bundle ACL reconstruction, compared to single-bundle, has been hypothesized to more effectively re-establish rotational stability by re-creating the anatomic ACL, but has not yet proven to result in better clinical outcomes.¹

In 1879, Dr. Paul Segond described a “fibrous, pearly band” at the lateral aspect of the knee that avulsed off the anterolateral proximal tibia during many ACL injuries.² The role of the lateral tissues in knee stability and their relationship with ACL pathology has attracted noteworthy attention in recent time. There have been multiple studies presenting an anatomical description of a structure at the anterolateral portion of the knee with definitive femoral, meniscal, and tibial attachments, which helps control internal rotational forces.^3-7 Claes and colleagues⁴ later found that band of tissue to be the anterolateral ligament (ALL) and determined its injury to be pathognomonic with ACL ruptures.

The ALL is a vital static stabilizer of the tibio-femoral joint, especially during internal tibial rotation.^8-10 In their report on ALL and ACL reconstruction, Helito and colleagues¹¹ acknowledge the necessity of accurate assessment of the lateral structures through imaging to determine the presence of extra-articular injury. Musculoskeletal diagnostic ultrasound has been established as an appropriate means to identify the ALL.¹²

Ultrasound can accurately determine the exact anatomic location of the origin and insertion of the ALL. Reconstruction of the ALL could yield better patient outcomes for those who experience concurrent ACL/ALL injury. Here we present an innovative technique for an ultrasound-guided percutaneous method for reconstruction of the ALL and report on a patient who had underwent ALL reconstruction.

Surgical Indications

All patients undergo an ultrasound evaluation preoperatively to determine if the ALL is intact or injured. Our experience has shown that when ultrasound evaluation reveals an intact ALL, the pivot shift has never been a grade III.

Surgical Technique

For a demonstration of this technique, see the video that accompanies this article.

The pivot shift test is conducted under anesthesia to determine whether an ALL reconstruction is required. The patient is placed in a supine position with the knee flexed at 30^o, at neutral rotation, and without any varus or valgus stress.

Rehabilitation

Rehabilitation following an ALL procedure is similar to traditional ACL rehabilitation with an added emphasis on minimizing rotational torque of the tibia in the early stages.

Case Report

In January 2013, a 17-year-old male soccer player suffered an ACL rupture of his right knee. Later that spring, he had an ACL reconstruction with an allograft. Twelve months postoperatively, the patient returned, saying that he felt much better; however, anytime he tried to plant his foot and rotate over that fixed foot, his knee felt unstable. The physical examination revealed both negative Lachman and anterior drawer tests but a I+ pivot shift test. A magnetic resonance imaging (MRI) examination revealed an intact ACL graft. A diagnostic ultrasound evaluation revealed a distal ALL injury. After discussing the risks, benefits, and goals with the patient, we opted for a diagnostic arthroscopy and a percutaneous, ultrasound-guided reconstruction of the ALL.

Postoperatively, the patient did very well. One week after surgery, he returned, saying he felt completely stable and demonstrated by repeating the rotation of his knee. The patient continued to have no issues until he returned 13 months post-ALL surgery, complaining of a recent injury that had caused the return of his feelings of instability. An MRI evaluation showed an intact ACL graft and the possibility of a ruptured ALL. Fifteen months after the initial ALL reconstruction, we proceeded with surgery. At arthroscopy, the patient was found to have a pivot shift of I+ and an intact ACL graft. The ALL was reconstructed again using an allograft, internal brace, and bone marrow concentrate. At 13 months post-ALL reconstruction revision, the patient had no complaints.

Discussion

Reconstruction of the ALL is aimed to restore anatomic rotational kinematics. Sonnery-Cottet and colleagues¹⁴ have reported promising initial results in their 2-year follow-up study of combined ACL and ALL reconstruction outcomes. This surgical technique includes use of an internal brace, which negates the necessity for external support devices and allows for earlier mobilization of the joint. A reconstruction of the ALL, performed concurrently with the ACL, does not add recovery time, but could prevent postsurgical complications and improve rehabilitation by eliminating rotational instability that presents in some ACL-reconstructed patients.

Sonnery-Cottet and colleagues¹⁵ state that their arthroscopic identification of the ALL can help to cultivate a “less invasive and more anatomic” reconstruction. The use of musculoskeletal ultrasound allows our technique to utilize a completely noninvasive imaging tool that allows proper establishment of ALL anatomy prior to the procedure. The entirety of the ALL is easily identifiable,^4,12 which has proven to be shortcoming of MRI evaluation.^15-17 Accurate preoperative assessment of the lateral structures is necessary in ACL-deficient individuals.^11,15 Sonography also provides a means of accurate guidance and socket creation, without generating large incisions.

If the ALL is responsible for internal rotatory stability as asserted, the structure should exhibit biomechanical properties during movement. In their study on the function of the ligament, Parsons and colleagues⁹ established the inverse relationship between the ALL and ACL during internal rotation. As their cadaveric knees were subjected to an internal rotatory force through increasing angles of flexion, the contribution of the ALL towards stability significantly increased while the ACL declined. Helito and colleagues⁸ and Zens and colleagues¹⁰ have demonstrated length changes of the ligament through varying degrees of flexion and internal rotation. Their reports indicate greater tension during knee movements, coinciding with the description of increasing ALL stability contribution by Parsons and colleagues.⁹ Kennedy and colleagues⁷ conducted a pull-to-failure test on the ALL. The average failure load was 175 N with a stiffness of 20 N/mm, illustrating the structure is a candidate for most traditional soft tissue grafts. The biomechanical evidence of the structural properties of the ALL confirms its importance in knee function and the necessity for its reconstruction.

With the understanding that ACL contributes to rotatory stability to some extent, the notion begs the question of how a centrally located ligament is able to prevent excessive rotation in a structure with a large relative radius. Biomechanically, with such a small moment arm, the ACL would experience tremendous stress when a rotatory force is applied. The same torque applied to a more superficial structure, with a greater moment, would sustain a large reduction in the applied force. The concept of a wheel and an axle should be considered. The equation is F₁ × R₁ = F₂ × R₂. We measured on a cadaveric knee the distance from the center of rotation to the ACL and the ALL, finding the radii were 5 mm and 30 mm, respectively. Taking these measurements, we would then expect the force experienced on the axle (ACL) to be 6 times greater than what would be experienced on the periphery of the wheel (ALL). The ALL (wheel) has a significant biomechanical advantage over the ACL (axle) in controlling and enduring internal rotatory forces of the knee. This would imply that if the ALL were damaged and not re-established, the ACL would experience a 6 times greater force trying to control internal rotation, which would result in a significantly increased chance of failure and rupture.

While there is a degree of dissent on the presence of the ALL, a number of studies have classified the tissue as an independent ligamentous structure.^3-7 While there is disagreement on the precise location of the femoral attachment, there is a consensus on the location of the tibial and meniscal attachments. Claes and colleagues⁴ originally outlined the femoral attachment as anterior and distal to the origin of the fibular collateral ligament (FCL), which is the description this technique follows. Since Claes and colleagues’⁴ report, many have investigated the ligament’s femoral origin with delineations ranging from posterior and proximal^3,5,7 to anterior and distal.^6,16-18

The accurate, noninvasive nature of the musculoskeletal ultrasound prior to any incisions being made makes this technique innovative and superior to other open surgical techniques or those that require fluoroscopy.

Conclusion

The ALL has been determined to play an integral role in the rotational stability of the knee. In the setting of instability and insufficiency, reconstruction will lead to better patient outcomes for concurrent ACL/ALL injuries and postsurgical rotatory instability following ACL procedures. This innovative technique utilizes ultrasound to ascertain the precise anatomical attachments of the ALL prior to the operation. The novel nature of this ultrasound-guided reconstruction has the potential to be applicable in many other surgical procedures.

Restoring native kinematics of the knee has been a primary goal of anterior cruciate ligament (ACL) procedures. Double-bundle ACL reconstruction, compared to single-bundle, has been hypothesized to more effectively re-establish rotational stability by re-creating the anatomic ACL, but has not yet proven to result in better clinical outcomes.¹

In 1879, Dr. Paul Segond described a “fibrous, pearly band” at the lateral aspect of the knee that avulsed off the anterolateral proximal tibia during many ACL injuries.² The role of the lateral tissues in knee stability and their relationship with ACL pathology has attracted noteworthy attention in recent time. There have been multiple studies presenting an anatomical description of a structure at the anterolateral portion of the knee with definitive femoral, meniscal, and tibial attachments, which helps control internal rotational forces.^3-7 Claes and colleagues⁴ later found that band of tissue to be the anterolateral ligament (ALL) and determined its injury to be pathognomonic with ACL ruptures.

The ALL is a vital static stabilizer of the tibio-femoral joint, especially during internal tibial rotation.^8-10 In their report on ALL and ACL reconstruction, Helito and colleagues¹¹ acknowledge the necessity of accurate assessment of the lateral structures through imaging to determine the presence of extra-articular injury. Musculoskeletal diagnostic ultrasound has been established as an appropriate means to identify the ALL.¹²

Ultrasound can accurately determine the exact anatomic location of the origin and insertion of the ALL. Reconstruction of the ALL could yield better patient outcomes for those who experience concurrent ACL/ALL injury. Here we present an innovative technique for an ultrasound-guided percutaneous method for reconstruction of the ALL and report on a patient who had underwent ALL reconstruction.

Surgical Indications

All patients undergo an ultrasound evaluation preoperatively to determine if the ALL is intact or injured. Our experience has shown that when ultrasound evaluation reveals an intact ALL, the pivot shift has never been a grade III.

Surgical Technique

For a demonstration of this technique, see the video that accompanies this article.

The pivot shift test is conducted under anesthesia to determine whether an ALL reconstruction is required. The patient is placed in a supine position with the knee flexed at 30^o, at neutral rotation, and without any varus or valgus stress.

Rehabilitation

Rehabilitation following an ALL procedure is similar to traditional ACL rehabilitation with an added emphasis on minimizing rotational torque of the tibia in the early stages.

Case Report

In January 2013, a 17-year-old male soccer player suffered an ACL rupture of his right knee. Later that spring, he had an ACL reconstruction with an allograft. Twelve months postoperatively, the patient returned, saying that he felt much better; however, anytime he tried to plant his foot and rotate over that fixed foot, his knee felt unstable. The physical examination revealed both negative Lachman and anterior drawer tests but a I+ pivot shift test. A magnetic resonance imaging (MRI) examination revealed an intact ACL graft. A diagnostic ultrasound evaluation revealed a distal ALL injury. After discussing the risks, benefits, and goals with the patient, we opted for a diagnostic arthroscopy and a percutaneous, ultrasound-guided reconstruction of the ALL.

Postoperatively, the patient did very well. One week after surgery, he returned, saying he felt completely stable and demonstrated by repeating the rotation of his knee. The patient continued to have no issues until he returned 13 months post-ALL surgery, complaining of a recent injury that had caused the return of his feelings of instability. An MRI evaluation showed an intact ACL graft and the possibility of a ruptured ALL. Fifteen months after the initial ALL reconstruction, we proceeded with surgery. At arthroscopy, the patient was found to have a pivot shift of I+ and an intact ACL graft. The ALL was reconstructed again using an allograft, internal brace, and bone marrow concentrate. At 13 months post-ALL reconstruction revision, the patient had no complaints.

Discussion

Reconstruction of the ALL is aimed to restore anatomic rotational kinematics. Sonnery-Cottet and colleagues¹⁴ have reported promising initial results in their 2-year follow-up study of combined ACL and ALL reconstruction outcomes. This surgical technique includes use of an internal brace, which negates the necessity for external support devices and allows for earlier mobilization of the joint. A reconstruction of the ALL, performed concurrently with the ACL, does not add recovery time, but could prevent postsurgical complications and improve rehabilitation by eliminating rotational instability that presents in some ACL-reconstructed patients.

Sonnery-Cottet and colleagues¹⁵ state that their arthroscopic identification of the ALL can help to cultivate a “less invasive and more anatomic” reconstruction. The use of musculoskeletal ultrasound allows our technique to utilize a completely noninvasive imaging tool that allows proper establishment of ALL anatomy prior to the procedure. The entirety of the ALL is easily identifiable,^4,12 which has proven to be shortcoming of MRI evaluation.^15-17 Accurate preoperative assessment of the lateral structures is necessary in ACL-deficient individuals.^11,15 Sonography also provides a means of accurate guidance and socket creation, without generating large incisions.

If the ALL is responsible for internal rotatory stability as asserted, the structure should exhibit biomechanical properties during movement. In their study on the function of the ligament, Parsons and colleagues⁹ established the inverse relationship between the ALL and ACL during internal rotation. As their cadaveric knees were subjected to an internal rotatory force through increasing angles of flexion, the contribution of the ALL towards stability significantly increased while the ACL declined. Helito and colleagues⁸ and Zens and colleagues¹⁰ have demonstrated length changes of the ligament through varying degrees of flexion and internal rotation. Their reports indicate greater tension during knee movements, coinciding with the description of increasing ALL stability contribution by Parsons and colleagues.⁹ Kennedy and colleagues⁷ conducted a pull-to-failure test on the ALL. The average failure load was 175 N with a stiffness of 20 N/mm, illustrating the structure is a candidate for most traditional soft tissue grafts. The biomechanical evidence of the structural properties of the ALL confirms its importance in knee function and the necessity for its reconstruction.

With the understanding that ACL contributes to rotatory stability to some extent, the notion begs the question of how a centrally located ligament is able to prevent excessive rotation in a structure with a large relative radius. Biomechanically, with such a small moment arm, the ACL would experience tremendous stress when a rotatory force is applied. The same torque applied to a more superficial structure, with a greater moment, would sustain a large reduction in the applied force. The concept of a wheel and an axle should be considered. The equation is F₁ × R₁ = F₂ × R₂. We measured on a cadaveric knee the distance from the center of rotation to the ACL and the ALL, finding the radii were 5 mm and 30 mm, respectively. Taking these measurements, we would then expect the force experienced on the axle (ACL) to be 6 times greater than what would be experienced on the periphery of the wheel (ALL). The ALL (wheel) has a significant biomechanical advantage over the ACL (axle) in controlling and enduring internal rotatory forces of the knee. This would imply that if the ALL were damaged and not re-established, the ACL would experience a 6 times greater force trying to control internal rotation, which would result in a significantly increased chance of failure and rupture.

While there is a degree of dissent on the presence of the ALL, a number of studies have classified the tissue as an independent ligamentous structure.^3-7 While there is disagreement on the precise location of the femoral attachment, there is a consensus on the location of the tibial and meniscal attachments. Claes and colleagues⁴ originally outlined the femoral attachment as anterior and distal to the origin of the fibular collateral ligament (FCL), which is the description this technique follows. Since Claes and colleagues’⁴ report, many have investigated the ligament’s femoral origin with delineations ranging from posterior and proximal^3,5,7 to anterior and distal.^6,16-18

The accurate, noninvasive nature of the musculoskeletal ultrasound prior to any incisions being made makes this technique innovative and superior to other open surgical techniques or those that require fluoroscopy.

Conclusion

The ALL has been determined to play an integral role in the rotational stability of the knee. In the setting of instability and insufficiency, reconstruction will lead to better patient outcomes for concurrent ACL/ALL injuries and postsurgical rotatory instability following ACL procedures. This innovative technique utilizes ultrasound to ascertain the precise anatomical attachments of the ALL prior to the operation. The novel nature of this ultrasound-guided reconstruction has the potential to be applicable in many other surgical procedures.

Restoring native kinematics of the knee has been a primary goal of anterior cruciate ligament (ACL) procedures. Double-bundle ACL reconstruction, compared to single-bundle, has been hypothesized to more effectively re-establish rotational stability by re-creating the anatomic ACL, but has not yet proven to result in better clinical outcomes.¹

In 1879, Dr. Paul Segond described a “fibrous, pearly band” at the lateral aspect of the knee that avulsed off the anterolateral proximal tibia during many ACL injuries.² The role of the lateral tissues in knee stability and their relationship with ACL pathology has attracted noteworthy attention in recent time. There have been multiple studies presenting an anatomical description of a structure at the anterolateral portion of the knee with definitive femoral, meniscal, and tibial attachments, which helps control internal rotational forces.^3-7 Claes and colleagues⁴ later found that band of tissue to be the anterolateral ligament (ALL) and determined its injury to be pathognomonic with ACL ruptures.

The ALL is a vital static stabilizer of the tibio-femoral joint, especially during internal tibial rotation.^8-10 In their report on ALL and ACL reconstruction, Helito and colleagues¹¹ acknowledge the necessity of accurate assessment of the lateral structures through imaging to determine the presence of extra-articular injury. Musculoskeletal diagnostic ultrasound has been established as an appropriate means to identify the ALL.¹²

Ultrasound can accurately determine the exact anatomic location of the origin and insertion of the ALL. Reconstruction of the ALL could yield better patient outcomes for those who experience concurrent ACL/ALL injury. Here we present an innovative technique for an ultrasound-guided percutaneous method for reconstruction of the ALL and report on a patient who had underwent ALL reconstruction.

Surgical Indications

All patients undergo an ultrasound evaluation preoperatively to determine if the ALL is intact or injured. Our experience has shown that when ultrasound evaluation reveals an intact ALL, the pivot shift has never been a grade III.

Surgical Technique

For a demonstration of this technique, see the video that accompanies this article.

The pivot shift test is conducted under anesthesia to determine whether an ALL reconstruction is required. The patient is placed in a supine position with the knee flexed at 30^o, at neutral rotation, and without any varus or valgus stress.

Rehabilitation

Rehabilitation following an ALL procedure is similar to traditional ACL rehabilitation with an added emphasis on minimizing rotational torque of the tibia in the early stages.

Case Report

In January 2013, a 17-year-old male soccer player suffered an ACL rupture of his right knee. Later that spring, he had an ACL reconstruction with an allograft. Twelve months postoperatively, the patient returned, saying that he felt much better; however, anytime he tried to plant his foot and rotate over that fixed foot, his knee felt unstable. The physical examination revealed both negative Lachman and anterior drawer tests but a I+ pivot shift test. A magnetic resonance imaging (MRI) examination revealed an intact ACL graft. A diagnostic ultrasound evaluation revealed a distal ALL injury. After discussing the risks, benefits, and goals with the patient, we opted for a diagnostic arthroscopy and a percutaneous, ultrasound-guided reconstruction of the ALL.

Postoperatively, the patient did very well. One week after surgery, he returned, saying he felt completely stable and demonstrated by repeating the rotation of his knee. The patient continued to have no issues until he returned 13 months post-ALL surgery, complaining of a recent injury that had caused the return of his feelings of instability. An MRI evaluation showed an intact ACL graft and the possibility of a ruptured ALL. Fifteen months after the initial ALL reconstruction, we proceeded with surgery. At arthroscopy, the patient was found to have a pivot shift of I+ and an intact ACL graft. The ALL was reconstructed again using an allograft, internal brace, and bone marrow concentrate. At 13 months post-ALL reconstruction revision, the patient had no complaints.

Discussion

Reconstruction of the ALL is aimed to restore anatomic rotational kinematics. Sonnery-Cottet and colleagues¹⁴ have reported promising initial results in their 2-year follow-up study of combined ACL and ALL reconstruction outcomes. This surgical technique includes use of an internal brace, which negates the necessity for external support devices and allows for earlier mobilization of the joint. A reconstruction of the ALL, performed concurrently with the ACL, does not add recovery time, but could prevent postsurgical complications and improve rehabilitation by eliminating rotational instability that presents in some ACL-reconstructed patients.

Sonnery-Cottet and colleagues¹⁵ state that their arthroscopic identification of the ALL can help to cultivate a “less invasive and more anatomic” reconstruction. The use of musculoskeletal ultrasound allows our technique to utilize a completely noninvasive imaging tool that allows proper establishment of ALL anatomy prior to the procedure. The entirety of the ALL is easily identifiable,^4,12 which has proven to be shortcoming of MRI evaluation.^15-17 Accurate preoperative assessment of the lateral structures is necessary in ACL-deficient individuals.^11,15 Sonography also provides a means of accurate guidance and socket creation, without generating large incisions.

If the ALL is responsible for internal rotatory stability as asserted, the structure should exhibit biomechanical properties during movement. In their study on the function of the ligament, Parsons and colleagues⁹ established the inverse relationship between the ALL and ACL during internal rotation. As their cadaveric knees were subjected to an internal rotatory force through increasing angles of flexion, the contribution of the ALL towards stability significantly increased while the ACL declined. Helito and colleagues⁸ and Zens and colleagues¹⁰ have demonstrated length changes of the ligament through varying degrees of flexion and internal rotation. Their reports indicate greater tension during knee movements, coinciding with the description of increasing ALL stability contribution by Parsons and colleagues.⁹ Kennedy and colleagues⁷ conducted a pull-to-failure test on the ALL. The average failure load was 175 N with a stiffness of 20 N/mm, illustrating the structure is a candidate for most traditional soft tissue grafts. The biomechanical evidence of the structural properties of the ALL confirms its importance in knee function and the necessity for its reconstruction.

With the understanding that ACL contributes to rotatory stability to some extent, the notion begs the question of how a centrally located ligament is able to prevent excessive rotation in a structure with a large relative radius. Biomechanically, with such a small moment arm, the ACL would experience tremendous stress when a rotatory force is applied. The same torque applied to a more superficial structure, with a greater moment, would sustain a large reduction in the applied force. The concept of a wheel and an axle should be considered. The equation is F₁ × R₁ = F₂ × R₂. We measured on a cadaveric knee the distance from the center of rotation to the ACL and the ALL, finding the radii were 5 mm and 30 mm, respectively. Taking these measurements, we would then expect the force experienced on the axle (ACL) to be 6 times greater than what would be experienced on the periphery of the wheel (ALL). The ALL (wheel) has a significant biomechanical advantage over the ACL (axle) in controlling and enduring internal rotatory forces of the knee. This would imply that if the ALL were damaged and not re-established, the ACL would experience a 6 times greater force trying to control internal rotation, which would result in a significantly increased chance of failure and rupture.

While there is a degree of dissent on the presence of the ALL, a number of studies have classified the tissue as an independent ligamentous structure.^3-7 While there is disagreement on the precise location of the femoral attachment, there is a consensus on the location of the tibial and meniscal attachments. Claes and colleagues⁴ originally outlined the femoral attachment as anterior and distal to the origin of the fibular collateral ligament (FCL), which is the description this technique follows. Since Claes and colleagues’⁴ report, many have investigated the ligament’s femoral origin with delineations ranging from posterior and proximal^3,5,7 to anterior and distal.^6,16-18

The accurate, noninvasive nature of the musculoskeletal ultrasound prior to any incisions being made makes this technique innovative and superior to other open surgical techniques or those that require fluoroscopy.

Conclusion

The ALL has been determined to play an integral role in the rotational stability of the knee. In the setting of instability and insufficiency, reconstruction will lead to better patient outcomes for concurrent ACL/ALL injuries and postsurgical rotatory instability following ACL procedures. This innovative technique utilizes ultrasound to ascertain the precise anatomical attachments of the ALL prior to the operation. The novel nature of this ultrasound-guided reconstruction has the potential to be applicable in many other surgical procedures.

Those who cannot remember the past are condemned to repeat it.

—George Santayana (Life of Reason, 1905)

Zero. That’s the number I put on the screen when I start the lecture I give to residents about the future of orthopedics. It represents the number of cases I still do exactly the same way now as I did when I graduated from my residency program. It represents the commitment to lifelong learning that we’ve made as orthopedists. Surgical techniques innovate so rapidly that they often outpace our research, leaving us performing new techniques based solely on industry and key opinion leader recommendation, and not on randomized controlled studies. Sometimes we’re led down the wrong path (remember when the meniscus was thought to be vestigial?) and other times new techniques lead to disappointing long-term results (the transtibial anterior cruciate ligament’s (ACL’s) failure to prevent arthritis). Sometimes, the old way is just as good as the new (there is no evidence to suggest that results from arthroscopic cuff repair are better than open in the long term). If we’ve been in practice long enough, we see the same ideas come around again (meniscal spacers, ACL repair, anterolateral ligament [ALL]). Most often, these new variations offer a slightly different twist and supporting literature.

So it seems “everything old is new again.” That’s why this issue of AJO is called The Throwback Issue. In this issue, we revisit ideas whose time has come and gone and now come again.

Our lead article this month focuses on ACL repair. Once abandoned after a landmark paper by Feagin and Curl¹ showed poor mid-term results, new and innovative techniques and instrumentation for knee surgery have made this possible. Investigators such as Murray² and DiFelice³ have done outstanding work showing the feasibility of ACL repair. In this issue we offer a comprehensive review and surgical technique for adding ACL repair to your portfolio of surgical offerings (see pages 408 and 454). Expanded versions of both of these articles are available at amjorthopedics.com.

Our second feature article discusses the reemergence of the ALL, an idea so hot in the public domain that it has been featured as a Jeopardy question. Described originally by Müller⁴ as the missing link in persistent rotational instability, the ALL might offer the key to improved long-term outcomes for patients undergoing ACL surgery. Read the article on page 418 and learn how to identify which patients are candidates for ALL reconstruction, and a simple surgical technique you can apply to your practice. Scan the provided QR code to watch the accompanying surgical technique video.

The Throwback Issue marks the fifth edition of the “new AJO.” It’s time to let us know how we are doing. Please email us at [email protected] to suggest future themes, articles you’d like to read, or suggestions for improvement.

Recently, based on the work of the authors mentioned above, I’ve begun offering ACL repair to select patients in my practice. I wouldn’t be able to do this if we as orthopedists weren’t constantly looking to improve, and weren’t willing to revisit old ideas to do it. Our goal at AJO is to present something in every article that can be immediately applied to your practice. Take a look at the articles presented this month, as we go “Back to the Future” to see what discarded ideas from our recent past can be applied to improve outcomes for your patients in the future.

Those who cannot remember the past are condemned to repeat it.

—George Santayana (Life of Reason, 1905)

Zero. That’s the number I put on the screen when I start the lecture I give to residents about the future of orthopedics. It represents the number of cases I still do exactly the same way now as I did when I graduated from my residency program. It represents the commitment to lifelong learning that we’ve made as orthopedists. Surgical techniques innovate so rapidly that they often outpace our research, leaving us performing new techniques based solely on industry and key opinion leader recommendation, and not on randomized controlled studies. Sometimes we’re led down the wrong path (remember when the meniscus was thought to be vestigial?) and other times new techniques lead to disappointing long-term results (the transtibial anterior cruciate ligament’s (ACL’s) failure to prevent arthritis). Sometimes, the old way is just as good as the new (there is no evidence to suggest that results from arthroscopic cuff repair are better than open in the long term). If we’ve been in practice long enough, we see the same ideas come around again (meniscal spacers, ACL repair, anterolateral ligament [ALL]). Most often, these new variations offer a slightly different twist and supporting literature.

So it seems “everything old is new again.” That’s why this issue of AJO is called The Throwback Issue. In this issue, we revisit ideas whose time has come and gone and now come again.

Our lead article this month focuses on ACL repair. Once abandoned after a landmark paper by Feagin and Curl¹ showed poor mid-term results, new and innovative techniques and instrumentation for knee surgery have made this possible. Investigators such as Murray² and DiFelice³ have done outstanding work showing the feasibility of ACL repair. In this issue we offer a comprehensive review and surgical technique for adding ACL repair to your portfolio of surgical offerings (see pages 408 and 454). Expanded versions of both of these articles are available at amjorthopedics.com.

Our second feature article discusses the reemergence of the ALL, an idea so hot in the public domain that it has been featured as a Jeopardy question. Described originally by Müller⁴ as the missing link in persistent rotational instability, the ALL might offer the key to improved long-term outcomes for patients undergoing ACL surgery. Read the article on page 418 and learn how to identify which patients are candidates for ALL reconstruction, and a simple surgical technique you can apply to your practice. Scan the provided QR code to watch the accompanying surgical technique video.

The Throwback Issue marks the fifth edition of the “new AJO.” It’s time to let us know how we are doing. Please email us at [email protected] to suggest future themes, articles you’d like to read, or suggestions for improvement.

Recently, based on the work of the authors mentioned above, I’ve begun offering ACL repair to select patients in my practice. I wouldn’t be able to do this if we as orthopedists weren’t constantly looking to improve, and weren’t willing to revisit old ideas to do it. Our goal at AJO is to present something in every article that can be immediately applied to your practice. Take a look at the articles presented this month, as we go “Back to the Future” to see what discarded ideas from our recent past can be applied to improve outcomes for your patients in the future.

Those who cannot remember the past are condemned to repeat it.

—George Santayana (Life of Reason, 1905)

Zero. That’s the number I put on the screen when I start the lecture I give to residents about the future of orthopedics. It represents the number of cases I still do exactly the same way now as I did when I graduated from my residency program. It represents the commitment to lifelong learning that we’ve made as orthopedists. Surgical techniques innovate so rapidly that they often outpace our research, leaving us performing new techniques based solely on industry and key opinion leader recommendation, and not on randomized controlled studies. Sometimes we’re led down the wrong path (remember when the meniscus was thought to be vestigial?) and other times new techniques lead to disappointing long-term results (the transtibial anterior cruciate ligament’s (ACL’s) failure to prevent arthritis). Sometimes, the old way is just as good as the new (there is no evidence to suggest that results from arthroscopic cuff repair are better than open in the long term). If we’ve been in practice long enough, we see the same ideas come around again (meniscal spacers, ACL repair, anterolateral ligament [ALL]). Most often, these new variations offer a slightly different twist and supporting literature.

So it seems “everything old is new again.” That’s why this issue of AJO is called The Throwback Issue. In this issue, we revisit ideas whose time has come and gone and now come again.

Our lead article this month focuses on ACL repair. Once abandoned after a landmark paper by Feagin and Curl¹ showed poor mid-term results, new and innovative techniques and instrumentation for knee surgery have made this possible. Investigators such as Murray² and DiFelice³ have done outstanding work showing the feasibility of ACL repair. In this issue we offer a comprehensive review and surgical technique for adding ACL repair to your portfolio of surgical offerings (see pages 408 and 454). Expanded versions of both of these articles are available at amjorthopedics.com.

Our second feature article discusses the reemergence of the ALL, an idea so hot in the public domain that it has been featured as a Jeopardy question. Described originally by Müller⁴ as the missing link in persistent rotational instability, the ALL might offer the key to improved long-term outcomes for patients undergoing ACL surgery. Read the article on page 418 and learn how to identify which patients are candidates for ALL reconstruction, and a simple surgical technique you can apply to your practice. Scan the provided QR code to watch the accompanying surgical technique video.

The Throwback Issue marks the fifth edition of the “new AJO.” It’s time to let us know how we are doing. Please email us at [email protected] to suggest future themes, articles you’d like to read, or suggestions for improvement.

Recently, based on the work of the authors mentioned above, I’ve begun offering ACL repair to select patients in my practice. I wouldn’t be able to do this if we as orthopedists weren’t constantly looking to improve, and weren’t willing to revisit old ideas to do it. Our goal at AJO is to present something in every article that can be immediately applied to your practice. Take a look at the articles presented this month, as we go “Back to the Future” to see what discarded ideas from our recent past can be applied to improve outcomes for your patients in the future.

Hospital readmissions are undesirable and expensive.¹ The Centers for Medicare & Medicaid Services (CMS) use hospital readmission rates as one measure of healthcare quality and hospital performance.² In addition, the Patient Protection and Affordable Care Act of 2010 established a provision that decreases payments to hospitals with above-average readmission rates.³ Total knee arthroplasties (TKAs) and total hip arthroplasties (THAs) are among the most common surgical procedures leading to readmission and cost almost $20 billion dollars annually in the Medicare population alone.¹ Identifying factors that lead to readmissions after certain popular procedures may be a way to improve healthcare quality and outcomes while decreasing costs.

One such operation is shoulder arthroplasty (SA), which has surged in popularity over the past decade and is projected to increase faster than TKAs and THAs.^4-6 SA is used to treat a variety of shoulder conditions, including osteoarthritis, inflammatory arthritis, severe proximal humeral fracture, avascular necrosis, and rotator cuff tear arthropathy.^7-12 Much as with knee and hip arthroplasty, good outcomes have been reported with SA: decreased pain, improved range of motion, and high patient satisfaction.^10,13 However, there have been few studies of rates of readmission after SA and the associated risk factors.^3,14,15 The reported rates of early readmission after SA have ranged from 5.6% to 7.3%.^3,14,15 These rates are comparable to rates of readmission after TKA (4.0%-6.6%) and THA (3.5%-8.4%).^15-17Recently, CMS introduced legislation to void payments for hospital-acquired conditions (HACs), preventable medical conditions that patients develop during or as a result of their hospital care and that were not present on admission.¹⁸ Although many factors contribute to readmission, a recent study regarding all-cause readmission during the first 30 days after discharge found that almost 50% of 30-day readmissions after knee and hip replacements were potentially preventable.¹⁹ HACs resulting in readmission after SAs make up 9.3% to 34.5% of all readmissions, after anatomical total shoulder arthroplasties (ATSAs) and reverse total shoulder arthroplasties (RTSAs).^3,14 The most common HACs include retained foreign body after surgery, air embolism, falls and trauma, catheter-associated urinary tract infection (CAUTI), surgical-site infection, deep vein thrombosis (DVT), and pulmonary embolism (PE).¹⁸ Raines and colleagues¹⁶ found that HACs accounted for 41.7% of all complications in knee or hip arthroplasty and that HACs were the greatest predictors of early readmission after both procedures.

We conducted a study to evaluate rates of readmission within 30 days after ATSA and RTSA and to describe the independent risk factors for readmission. We hypothesized that the rate of readmission after SA would be similar to the rate after knee and hip arthroplasty and that readmission risk factors would be similar. Elucidating these rates and associated risk factors may ultimately help to minimize the burden of disability on patients and the burden of financial costs on healthcare institutions.

Materials and Methods

Institutional Review Board approval was not required for this study, and all data used were de-identified to Health Insurance Portability and Accountability Act (HIPAA) standards. We used the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database for this study. The NSQIP was developed in the 1990s to improve surgical quality in the Veterans Health Administration and was later adapted by the ACS.²⁰ NSQIP follows patients for 30 days after operations and provides clinical data and outcome measures that are closely regulated and internally audited.²¹ The program has continued to expand and now includes more than 400 institutions. The NSQIP database has been validated as a reliable source of surgical outcomes data, including outcomes data for orthopedic procedures, and has been used in other studies of readmissions.^17,22

In the present study, the ACS-NSQIP files for the period 2011-2013 were queried for all total shoulder arthroplasties (TSAs) (Current Procedural Terminology [CPT] code 23472, which includes ATSA and RTSA). Descriptive analysis was performed to determine the overall readmission rate as well as the percentages of readmissions for medical and surgical complications. Reasons for readmission were collected from 2012 and 2013 (information from 2011 was absent).

The various patient parameters compiled within the database were examined in a review of ATSAs and RTSAs. Demographics, comorbidities, operative characteristics, and predischarge complications were amassed from these data. Demographics included age, sex, race, body mass index, smoking status, preoperative functional health status, and American Society of Anesthesiologists (ASA) score. Comorbidities included diabetes mellitus, hypertension, chronic corticosteroid use, coagulation disorder, peripheral vascular disease, chronic obstructive pulmonary disease (COPD), cardiac comorbidity (including congestive heart failure, history of myocardial infarction, previous coronary intervention or cardiac surgery, and angina), renal comorbidity (including acute renal failure and preoperative dialysis), neurologic comorbidity (including impaired sensorium, hemiplegia, history of transient ischemic attack, and history of cerebrovascular accident with or without residual deficit), and preoperative blood transfusion. Operative characteristics included resident involvement, operative time more than 1 SD from the mean (>164.4 minutes), intraoperative blood transfusion, and revision surgery. Predischarge complications included pneumonia, CAUTI, DVT, PE, postoperative bleeding that required transfusion, cerebrovascular accident, myocardial infarction, and sepsis. Surgical-site infection, CAUTI, DVT, and PE were selected for analysis because these HACs are common in our cohort.

After the data on these characteristics were collected, univariate analysis was performed to determine association with any readmission. Factors with P < .20 were then entered into multivariate analysis to determine independent risk factors for readmission. This P value was selected to make the model inclusive of any potentially important predictor. Univariate analysis was performed using the Fisher exact test. Multivariate analysis was performed using backward conditional binary logistic regression. Statistical significance was set at P < .05. All analysis was performed with SPSS Version 22.0 (SPSS).

Results

This study included a combined total of 3501 ATSAs and RTSAs performed between 2011 and 2013. The overall readmission rate was 2.7%. The associated diagnosis for readmission was available for 54% of the readmitted patients. Of the known readmission diagnoses, 33% were secondary to HACs.

Of the 51 readmissions, 34 (67%) were for medical complications, and 17 (33%) were for surgical complications. Pneumonia was the most common medical complication (11.8%), followed by UTI (7.8%), DVT (5.9%), PE (5.9%), and renal insufficiency (3.9%). Surgical-site infection was the most common surgical complication (13.7%), followed by prosthetic joint dislocation (9.8%) and hematoma (3.9%).

Discussion

Hospital readmissions are important because they represent quality of care and play a role in patient outcomes. Arthroplasty research has focused mainly on readmissions after primary knee and hip replacements.^23-25

Historical rates of early readmission after SA¹⁴ are comparable to those found in our study. Previously identified risk factors have included increasing age, Medicaid insurance status, low-volume surgical centers, and SA type.³ Mahoney and colleagues¹⁴ reported a 90-day readmission rate of 5.9%, but, when they removed hemiarthroplasty replacement from the analysis and shortened the readmission timeline to 30 days, the readmission rate was identical to the 2.7% rate in the present study. In their series from a single high-volume institution, the highest 90-day readmission rate was found for hemiarthroplasty (8.8%), followed by RTSA (6.6%) and ATSA (4.5%). In a study by Schairer and colleagues,³ the readmission rate was also influenced by replacement type, but their results differed from those of Mahoney and colleagues.¹⁴ Schairer and colleagues³ analyzed data from 7 state inpatient databases and found that the highest readmission rate was associated with RTSA (11.2%), followed by hemiarthroplasty (8.2%) and ATSA (6.0%). In both series, RTSA readmission rates were higher than ATSA readmission rates—consistent with the complication profiles of these procedures, with RTSA often provided as a surgery of last resort, after failure of other procedures, including ATSA.²⁶ The lower 30-day readmission rate in the present study may be attributable to the fact that some surgical and medical complications may not have developed within this short time. Nonetheless, the majority of readmissions typically present within the first 30 days after SA.^14,15 Other factors, including hospital volume, surgeon volume, race, and hospital type, may also influence readmission rates but could not be compared between studies.^27,28

The present study found that revision surgery, 3 or more comorbidities, and extended LOS (>4.3 days) more than doubled the risk of readmission. Published SA revision rates range from 5% to 42%, with most revisions performed for instability, dislocation, infection, and component loosening.^6,29 Complication rates are higher for revision SA than for primary SA, which may explain why revisions predispose patients to readmission.³⁰ Compared with primary SAs, revision SAs are also more likely to be RTSAs, and these salvage procedures have been found to have high complication rates.³¹ In the present study, the most common comorbidities were hypertension, diabetes, and COPD; the literature supports these as some of the most common comorbid medical conditions in patients who undergo ATSA or RTSA.^5,26,32 Furthermore, all 3 of these comorbidities have been shown to be independent predictors of increased postoperative complications in patients who undergo SA, which ultimately would increase the risk of readmission.^3,26,33,34 Last, extended LOS has also been shown to increase the risk of unplanned readmissions after orthopedic procedures.³⁵ Risk factors associated with increased LOS after ATSA or RTSA include female sex, advanced age, multiple comorbidities, and postoperative complications.³²Several other factors must be noted with respect to individual risk for readmission. In the present study, age over 75 years, dependent functional status, ASA score of 4 or higher, and cardiac comorbidity were found to have a significant association with readmission. Increased age is a risk factor for increased postoperative complications, more medical comorbidities, and increased LOS.^34,36 Older people are at higher risk of developing osteoarthritis and rotator cuff tear arthropathy and are more likely to undergo SA.^5,6 Older people also are more likely to be dependent, which itself is a risk factor for readmission.¹⁹ An ASA score of 3 or 4 has been found to be associated with increased LOS and complications after SA, and cardiac comorbidities predispose patients to a variety of complications.^34,36,37In studies that have combined surgical and medical factors, rates of complications early after ATSA and RTSA have ranged from 3.6% to 17.8%.^26,38,39 After SAs, medical complications (80%) are more common than surgical complications (20%).³⁹ In the present cohort, many more readmissions were for medical complications (67%) than for surgical complications (33%). In addition, Schairer and colleagues³ found medical complications associated with more than 80% of readmissions after SA.³ Infection was the most common medical reason (pneumonia) and surgical reason (surgical-site infection) for readmission—consistent with findings of other studies.^3,35,40 Infection has accounted for 9.4% to 41.4% of readmissions after ATSA and RTSA.^3,14In joint arthroplasty, infection occurs more often in patients with coexisting medical comorbidities, leading to higher mortality and increased LOS.⁴¹ Prosthetic joint dislocation was common as well—similar to findings in other studies.^3,10In the present study, 33% of known readmission diagnoses were secondary to HACs. Surgical-site infection was the most common, followed by CAUTI, DVT, and PE. In another study, of knee and hip arthroplasties, HACs accounted for more than 40% of all complications and were the strongest predictor of early readmission.¹⁶ In SA studies, HACs were responsible for 9.3% to 34.5% of readmissions after ATSA and RTSA.^3,14 Our finding (33%) is more in line with Mahoney and colleagues¹⁴ (34.5%) than Schairer and colleagues³ (9.3%). One explanation for the large discrepancy with Schairer and colleagues³ is that UTI was not among the medical reasons for readmission in their study, but it was in ours. Another difference is that we used a database that included data from multiple institutions. Last, Schairer and colleagues³ excluded revision SAs from their analysis (complication rates are higher for revision SAs than for primary SAs³⁰). They also excluded cases of SA used for fracture (shown to increase the risk for PE⁴²). The US Department of Health and Human Services estimated that patients experienced 1.3 million fewer HACs during the period 2010-2013, corresponding to a 17% decline over the 3 years.⁴³ This translates to an estimated 50,000 fewer mortalities, and $12 billion saved in healthcare costs, over the same period.⁴³ Preventing HACs helps reduce readmission rates while improving patient outcomes and decreasing healthcare costs.

This study had several limitations. We could not differentiate between ATSA and RTSA readmission rates because, for the study period, these procedures are collectively organized under a common CPT code in the NSQIP database. Readmission and complication rates are higher for RTSAs than for ATSAs.^3,14 In addition, our data were limited to hospitals that were participating in NSQIP, which could lead to selection bias. We studied rates of only those readmissions and complications that occurred within 30 days, but many complications develop after 30 days, and these increase the readmission rate. Last, reasons for readmission were not recorded for 2011, so this information was available only for the final 2 years of the study. Despite these limitations, NSQIP still allows for a powerful study, as it includes multiple institutions and a very large cohort.

Conclusion

With medical costs increasing, focus has shifted to quality care and good outcomes with the goal of reducing readmissions and complications after various procedures. SA has recently become more popular because of its multiple indications, and this trend will continue. In the present study, the rate of readmission within 30 days after ATSA or RTSA was 2.7%. Revision surgery, 3 or more comorbidities, and extended LOS were independent risk factors that more than doubled the risk of readmission. Understanding the risk factors for short-term readmission will allow for better patient care and decreased costs, and will benefit the healthcare system as a whole.

Am J Orthop. 2016;45(6):E386-E392. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Hospital readmissions are undesirable and expensive.¹ The Centers for Medicare & Medicaid Services (CMS) use hospital readmission rates as one measure of healthcare quality and hospital performance.² In addition, the Patient Protection and Affordable Care Act of 2010 established a provision that decreases payments to hospitals with above-average readmission rates.³ Total knee arthroplasties (TKAs) and total hip arthroplasties (THAs) are among the most common surgical procedures leading to readmission and cost almost $20 billion dollars annually in the Medicare population alone.¹ Identifying factors that lead to readmissions after certain popular procedures may be a way to improve healthcare quality and outcomes while decreasing costs.

One such operation is shoulder arthroplasty (SA), which has surged in popularity over the past decade and is projected to increase faster than TKAs and THAs.^4-6 SA is used to treat a variety of shoulder conditions, including osteoarthritis, inflammatory arthritis, severe proximal humeral fracture, avascular necrosis, and rotator cuff tear arthropathy.^7-12 Much as with knee and hip arthroplasty, good outcomes have been reported with SA: decreased pain, improved range of motion, and high patient satisfaction.^10,13 However, there have been few studies of rates of readmission after SA and the associated risk factors.^3,14,15 The reported rates of early readmission after SA have ranged from 5.6% to 7.3%.^3,14,15 These rates are comparable to rates of readmission after TKA (4.0%-6.6%) and THA (3.5%-8.4%).^15-17Recently, CMS introduced legislation to void payments for hospital-acquired conditions (HACs), preventable medical conditions that patients develop during or as a result of their hospital care and that were not present on admission.¹⁸ Although many factors contribute to readmission, a recent study regarding all-cause readmission during the first 30 days after discharge found that almost 50% of 30-day readmissions after knee and hip replacements were potentially preventable.¹⁹ HACs resulting in readmission after SAs make up 9.3% to 34.5% of all readmissions, after anatomical total shoulder arthroplasties (ATSAs) and reverse total shoulder arthroplasties (RTSAs).^3,14 The most common HACs include retained foreign body after surgery, air embolism, falls and trauma, catheter-associated urinary tract infection (CAUTI), surgical-site infection, deep vein thrombosis (DVT), and pulmonary embolism (PE).¹⁸ Raines and colleagues¹⁶ found that HACs accounted for 41.7% of all complications in knee or hip arthroplasty and that HACs were the greatest predictors of early readmission after both procedures.

We conducted a study to evaluate rates of readmission within 30 days after ATSA and RTSA and to describe the independent risk factors for readmission. We hypothesized that the rate of readmission after SA would be similar to the rate after knee and hip arthroplasty and that readmission risk factors would be similar. Elucidating these rates and associated risk factors may ultimately help to minimize the burden of disability on patients and the burden of financial costs on healthcare institutions.

Materials and Methods

Institutional Review Board approval was not required for this study, and all data used were de-identified to Health Insurance Portability and Accountability Act (HIPAA) standards. We used the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database for this study. The NSQIP was developed in the 1990s to improve surgical quality in the Veterans Health Administration and was later adapted by the ACS.²⁰ NSQIP follows patients for 30 days after operations and provides clinical data and outcome measures that are closely regulated and internally audited.²¹ The program has continued to expand and now includes more than 400 institutions. The NSQIP database has been validated as a reliable source of surgical outcomes data, including outcomes data for orthopedic procedures, and has been used in other studies of readmissions.^17,22

In the present study, the ACS-NSQIP files for the period 2011-2013 were queried for all total shoulder arthroplasties (TSAs) (Current Procedural Terminology [CPT] code 23472, which includes ATSA and RTSA). Descriptive analysis was performed to determine the overall readmission rate as well as the percentages of readmissions for medical and surgical complications. Reasons for readmission were collected from 2012 and 2013 (information from 2011 was absent).

The various patient parameters compiled within the database were examined in a review of ATSAs and RTSAs. Demographics, comorbidities, operative characteristics, and predischarge complications were amassed from these data. Demographics included age, sex, race, body mass index, smoking status, preoperative functional health status, and American Society of Anesthesiologists (ASA) score. Comorbidities included diabetes mellitus, hypertension, chronic corticosteroid use, coagulation disorder, peripheral vascular disease, chronic obstructive pulmonary disease (COPD), cardiac comorbidity (including congestive heart failure, history of myocardial infarction, previous coronary intervention or cardiac surgery, and angina), renal comorbidity (including acute renal failure and preoperative dialysis), neurologic comorbidity (including impaired sensorium, hemiplegia, history of transient ischemic attack, and history of cerebrovascular accident with or without residual deficit), and preoperative blood transfusion. Operative characteristics included resident involvement, operative time more than 1 SD from the mean (>164.4 minutes), intraoperative blood transfusion, and revision surgery. Predischarge complications included pneumonia, CAUTI, DVT, PE, postoperative bleeding that required transfusion, cerebrovascular accident, myocardial infarction, and sepsis. Surgical-site infection, CAUTI, DVT, and PE were selected for analysis because these HACs are common in our cohort.

After the data on these characteristics were collected, univariate analysis was performed to determine association with any readmission. Factors with P < .20 were then entered into multivariate analysis to determine independent risk factors for readmission. This P value was selected to make the model inclusive of any potentially important predictor. Univariate analysis was performed using the Fisher exact test. Multivariate analysis was performed using backward conditional binary logistic regression. Statistical significance was set at P < .05. All analysis was performed with SPSS Version 22.0 (SPSS).

Results

This study included a combined total of 3501 ATSAs and RTSAs performed between 2011 and 2013. The overall readmission rate was 2.7%. The associated diagnosis for readmission was available for 54% of the readmitted patients. Of the known readmission diagnoses, 33% were secondary to HACs.

Of the 51 readmissions, 34 (67%) were for medical complications, and 17 (33%) were for surgical complications. Pneumonia was the most common medical complication (11.8%), followed by UTI (7.8%), DVT (5.9%), PE (5.9%), and renal insufficiency (3.9%). Surgical-site infection was the most common surgical complication (13.7%), followed by prosthetic joint dislocation (9.8%) and hematoma (3.9%).

Discussion

Hospital readmissions are important because they represent quality of care and play a role in patient outcomes. Arthroplasty research has focused mainly on readmissions after primary knee and hip replacements.^23-25

Historical rates of early readmission after SA¹⁴ are comparable to those found in our study. Previously identified risk factors have included increasing age, Medicaid insurance status, low-volume surgical centers, and SA type.³ Mahoney and colleagues¹⁴ reported a 90-day readmission rate of 5.9%, but, when they removed hemiarthroplasty replacement from the analysis and shortened the readmission timeline to 30 days, the readmission rate was identical to the 2.7% rate in the present study. In their series from a single high-volume institution, the highest 90-day readmission rate was found for hemiarthroplasty (8.8%), followed by RTSA (6.6%) and ATSA (4.5%). In a study by Schairer and colleagues,³ the readmission rate was also influenced by replacement type, but their results differed from those of Mahoney and colleagues.¹⁴ Schairer and colleagues³ analyzed data from 7 state inpatient databases and found that the highest readmission rate was associated with RTSA (11.2%), followed by hemiarthroplasty (8.2%) and ATSA (6.0%). In both series, RTSA readmission rates were higher than ATSA readmission rates—consistent with the complication profiles of these procedures, with RTSA often provided as a surgery of last resort, after failure of other procedures, including ATSA.²⁶ The lower 30-day readmission rate in the present study may be attributable to the fact that some surgical and medical complications may not have developed within this short time. Nonetheless, the majority of readmissions typically present within the first 30 days after SA.^14,15 Other factors, including hospital volume, surgeon volume, race, and hospital type, may also influence readmission rates but could not be compared between studies.^27,28

The present study found that revision surgery, 3 or more comorbidities, and extended LOS (>4.3 days) more than doubled the risk of readmission. Published SA revision rates range from 5% to 42%, with most revisions performed for instability, dislocation, infection, and component loosening.^6,29 Complication rates are higher for revision SA than for primary SA, which may explain why revisions predispose patients to readmission.³⁰ Compared with primary SAs, revision SAs are also more likely to be RTSAs, and these salvage procedures have been found to have high complication rates.³¹ In the present study, the most common comorbidities were hypertension, diabetes, and COPD; the literature supports these as some of the most common comorbid medical conditions in patients who undergo ATSA or RTSA.^5,26,32 Furthermore, all 3 of these comorbidities have been shown to be independent predictors of increased postoperative complications in patients who undergo SA, which ultimately would increase the risk of readmission.^3,26,33,34 Last, extended LOS has also been shown to increase the risk of unplanned readmissions after orthopedic procedures.³⁵ Risk factors associated with increased LOS after ATSA or RTSA include female sex, advanced age, multiple comorbidities, and postoperative complications.³²Several other factors must be noted with respect to individual risk for readmission. In the present study, age over 75 years, dependent functional status, ASA score of 4 or higher, and cardiac comorbidity were found to have a significant association with readmission. Increased age is a risk factor for increased postoperative complications, more medical comorbidities, and increased LOS.^34,36 Older people are at higher risk of developing osteoarthritis and rotator cuff tear arthropathy and are more likely to undergo SA.^5,6 Older people also are more likely to be dependent, which itself is a risk factor for readmission.¹⁹ An ASA score of 3 or 4 has been found to be associated with increased LOS and complications after SA, and cardiac comorbidities predispose patients to a variety of complications.^34,36,37In studies that have combined surgical and medical factors, rates of complications early after ATSA and RTSA have ranged from 3.6% to 17.8%.^26,38,39 After SAs, medical complications (80%) are more common than surgical complications (20%).³⁹ In the present cohort, many more readmissions were for medical complications (67%) than for surgical complications (33%). In addition, Schairer and colleagues³ found medical complications associated with more than 80% of readmissions after SA.³ Infection was the most common medical reason (pneumonia) and surgical reason (surgical-site infection) for readmission—consistent with findings of other studies.^3,35,40 Infection has accounted for 9.4% to 41.4% of readmissions after ATSA and RTSA.^3,14In joint arthroplasty, infection occurs more often in patients with coexisting medical comorbidities, leading to higher mortality and increased LOS.⁴¹ Prosthetic joint dislocation was common as well—similar to findings in other studies.^3,10In the present study, 33% of known readmission diagnoses were secondary to HACs. Surgical-site infection was the most common, followed by CAUTI, DVT, and PE. In another study, of knee and hip arthroplasties, HACs accounted for more than 40% of all complications and were the strongest predictor of early readmission.¹⁶ In SA studies, HACs were responsible for 9.3% to 34.5% of readmissions after ATSA and RTSA.^3,14 Our finding (33%) is more in line with Mahoney and colleagues¹⁴ (34.5%) than Schairer and colleagues³ (9.3%). One explanation for the large discrepancy with Schairer and colleagues³ is that UTI was not among the medical reasons for readmission in their study, but it was in ours. Another difference is that we used a database that included data from multiple institutions. Last, Schairer and colleagues³ excluded revision SAs from their analysis (complication rates are higher for revision SAs than for primary SAs³⁰). They also excluded cases of SA used for fracture (shown to increase the risk for PE⁴²). The US Department of Health and Human Services estimated that patients experienced 1.3 million fewer HACs during the period 2010-2013, corresponding to a 17% decline over the 3 years.⁴³ This translates to an estimated 50,000 fewer mortalities, and $12 billion saved in healthcare costs, over the same period.⁴³ Preventing HACs helps reduce readmission rates while improving patient outcomes and decreasing healthcare costs.

This study had several limitations. We could not differentiate between ATSA and RTSA readmission rates because, for the study period, these procedures are collectively organized under a common CPT code in the NSQIP database. Readmission and complication rates are higher for RTSAs than for ATSAs.^3,14 In addition, our data were limited to hospitals that were participating in NSQIP, which could lead to selection bias. We studied rates of only those readmissions and complications that occurred within 30 days, but many complications develop after 30 days, and these increase the readmission rate. Last, reasons for readmission were not recorded for 2011, so this information was available only for the final 2 years of the study. Despite these limitations, NSQIP still allows for a powerful study, as it includes multiple institutions and a very large cohort.

Conclusion

With medical costs increasing, focus has shifted to quality care and good outcomes with the goal of reducing readmissions and complications after various procedures. SA has recently become more popular because of its multiple indications, and this trend will continue. In the present study, the rate of readmission within 30 days after ATSA or RTSA was 2.7%. Revision surgery, 3 or more comorbidities, and extended LOS were independent risk factors that more than doubled the risk of readmission. Understanding the risk factors for short-term readmission will allow for better patient care and decreased costs, and will benefit the healthcare system as a whole.

Am J Orthop. 2016;45(6):E386-E392. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Hospital readmissions are undesirable and expensive.¹ The Centers for Medicare & Medicaid Services (CMS) use hospital readmission rates as one measure of healthcare quality and hospital performance.² In addition, the Patient Protection and Affordable Care Act of 2010 established a provision that decreases payments to hospitals with above-average readmission rates.³ Total knee arthroplasties (TKAs) and total hip arthroplasties (THAs) are among the most common surgical procedures leading to readmission and cost almost $20 billion dollars annually in the Medicare population alone.¹ Identifying factors that lead to readmissions after certain popular procedures may be a way to improve healthcare quality and outcomes while decreasing costs.

One such operation is shoulder arthroplasty (SA), which has surged in popularity over the past decade and is projected to increase faster than TKAs and THAs.^4-6 SA is used to treat a variety of shoulder conditions, including osteoarthritis, inflammatory arthritis, severe proximal humeral fracture, avascular necrosis, and rotator cuff tear arthropathy.^7-12 Much as with knee and hip arthroplasty, good outcomes have been reported with SA: decreased pain, improved range of motion, and high patient satisfaction.^10,13 However, there have been few studies of rates of readmission after SA and the associated risk factors.^3,14,15 The reported rates of early readmission after SA have ranged from 5.6% to 7.3%.^3,14,15 These rates are comparable to rates of readmission after TKA (4.0%-6.6%) and THA (3.5%-8.4%).^15-17Recently, CMS introduced legislation to void payments for hospital-acquired conditions (HACs), preventable medical conditions that patients develop during or as a result of their hospital care and that were not present on admission.¹⁸ Although many factors contribute to readmission, a recent study regarding all-cause readmission during the first 30 days after discharge found that almost 50% of 30-day readmissions after knee and hip replacements were potentially preventable.¹⁹ HACs resulting in readmission after SAs make up 9.3% to 34.5% of all readmissions, after anatomical total shoulder arthroplasties (ATSAs) and reverse total shoulder arthroplasties (RTSAs).^3,14 The most common HACs include retained foreign body after surgery, air embolism, falls and trauma, catheter-associated urinary tract infection (CAUTI), surgical-site infection, deep vein thrombosis (DVT), and pulmonary embolism (PE).¹⁸ Raines and colleagues¹⁶ found that HACs accounted for 41.7% of all complications in knee or hip arthroplasty and that HACs were the greatest predictors of early readmission after both procedures.

We conducted a study to evaluate rates of readmission within 30 days after ATSA and RTSA and to describe the independent risk factors for readmission. We hypothesized that the rate of readmission after SA would be similar to the rate after knee and hip arthroplasty and that readmission risk factors would be similar. Elucidating these rates and associated risk factors may ultimately help to minimize the burden of disability on patients and the burden of financial costs on healthcare institutions.

Materials and Methods

Institutional Review Board approval was not required for this study, and all data used were de-identified to Health Insurance Portability and Accountability Act (HIPAA) standards. We used the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database for this study. The NSQIP was developed in the 1990s to improve surgical quality in the Veterans Health Administration and was later adapted by the ACS.²⁰ NSQIP follows patients for 30 days after operations and provides clinical data and outcome measures that are closely regulated and internally audited.²¹ The program has continued to expand and now includes more than 400 institutions. The NSQIP database has been validated as a reliable source of surgical outcomes data, including outcomes data for orthopedic procedures, and has been used in other studies of readmissions.^17,22

In the present study, the ACS-NSQIP files for the period 2011-2013 were queried for all total shoulder arthroplasties (TSAs) (Current Procedural Terminology [CPT] code 23472, which includes ATSA and RTSA). Descriptive analysis was performed to determine the overall readmission rate as well as the percentages of readmissions for medical and surgical complications. Reasons for readmission were collected from 2012 and 2013 (information from 2011 was absent).

The various patient parameters compiled within the database were examined in a review of ATSAs and RTSAs. Demographics, comorbidities, operative characteristics, and predischarge complications were amassed from these data. Demographics included age, sex, race, body mass index, smoking status, preoperative functional health status, and American Society of Anesthesiologists (ASA) score. Comorbidities included diabetes mellitus, hypertension, chronic corticosteroid use, coagulation disorder, peripheral vascular disease, chronic obstructive pulmonary disease (COPD), cardiac comorbidity (including congestive heart failure, history of myocardial infarction, previous coronary intervention or cardiac surgery, and angina), renal comorbidity (including acute renal failure and preoperative dialysis), neurologic comorbidity (including impaired sensorium, hemiplegia, history of transient ischemic attack, and history of cerebrovascular accident with or without residual deficit), and preoperative blood transfusion. Operative characteristics included resident involvement, operative time more than 1 SD from the mean (>164.4 minutes), intraoperative blood transfusion, and revision surgery. Predischarge complications included pneumonia, CAUTI, DVT, PE, postoperative bleeding that required transfusion, cerebrovascular accident, myocardial infarction, and sepsis. Surgical-site infection, CAUTI, DVT, and PE were selected for analysis because these HACs are common in our cohort.

After the data on these characteristics were collected, univariate analysis was performed to determine association with any readmission. Factors with P < .20 were then entered into multivariate analysis to determine independent risk factors for readmission. This P value was selected to make the model inclusive of any potentially important predictor. Univariate analysis was performed using the Fisher exact test. Multivariate analysis was performed using backward conditional binary logistic regression. Statistical significance was set at P < .05. All analysis was performed with SPSS Version 22.0 (SPSS).

Results

This study included a combined total of 3501 ATSAs and RTSAs performed between 2011 and 2013. The overall readmission rate was 2.7%. The associated diagnosis for readmission was available for 54% of the readmitted patients. Of the known readmission diagnoses, 33% were secondary to HACs.

Of the 51 readmissions, 34 (67%) were for medical complications, and 17 (33%) were for surgical complications. Pneumonia was the most common medical complication (11.8%), followed by UTI (7.8%), DVT (5.9%), PE (5.9%), and renal insufficiency (3.9%). Surgical-site infection was the most common surgical complication (13.7%), followed by prosthetic joint dislocation (9.8%) and hematoma (3.9%).

Discussion

Hospital readmissions are important because they represent quality of care and play a role in patient outcomes. Arthroplasty research has focused mainly on readmissions after primary knee and hip replacements.^23-25

Historical rates of early readmission after SA¹⁴ are comparable to those found in our study. Previously identified risk factors have included increasing age, Medicaid insurance status, low-volume surgical centers, and SA type.³ Mahoney and colleagues¹⁴ reported a 90-day readmission rate of 5.9%, but, when they removed hemiarthroplasty replacement from the analysis and shortened the readmission timeline to 30 days, the readmission rate was identical to the 2.7% rate in the present study. In their series from a single high-volume institution, the highest 90-day readmission rate was found for hemiarthroplasty (8.8%), followed by RTSA (6.6%) and ATSA (4.5%). In a study by Schairer and colleagues,³ the readmission rate was also influenced by replacement type, but their results differed from those of Mahoney and colleagues.¹⁴ Schairer and colleagues³ analyzed data from 7 state inpatient databases and found that the highest readmission rate was associated with RTSA (11.2%), followed by hemiarthroplasty (8.2%) and ATSA (6.0%). In both series, RTSA readmission rates were higher than ATSA readmission rates—consistent with the complication profiles of these procedures, with RTSA often provided as a surgery of last resort, after failure of other procedures, including ATSA.²⁶ The lower 30-day readmission rate in the present study may be attributable to the fact that some surgical and medical complications may not have developed within this short time. Nonetheless, the majority of readmissions typically present within the first 30 days after SA.^14,15 Other factors, including hospital volume, surgeon volume, race, and hospital type, may also influence readmission rates but could not be compared between studies.^27,28

The present study found that revision surgery, 3 or more comorbidities, and extended LOS (>4.3 days) more than doubled the risk of readmission. Published SA revision rates range from 5% to 42%, with most revisions performed for instability, dislocation, infection, and component loosening.^6,29 Complication rates are higher for revision SA than for primary SA, which may explain why revisions predispose patients to readmission.³⁰ Compared with primary SAs, revision SAs are also more likely to be RTSAs, and these salvage procedures have been found to have high complication rates.³¹ In the present study, the most common comorbidities were hypertension, diabetes, and COPD; the literature supports these as some of the most common comorbid medical conditions in patients who undergo ATSA or RTSA.^5,26,32 Furthermore, all 3 of these comorbidities have been shown to be independent predictors of increased postoperative complications in patients who undergo SA, which ultimately would increase the risk of readmission.^3,26,33,34 Last, extended LOS has also been shown to increase the risk of unplanned readmissions after orthopedic procedures.³⁵ Risk factors associated with increased LOS after ATSA or RTSA include female sex, advanced age, multiple comorbidities, and postoperative complications.³²Several other factors must be noted with respect to individual risk for readmission. In the present study, age over 75 years, dependent functional status, ASA score of 4 or higher, and cardiac comorbidity were found to have a significant association with readmission. Increased age is a risk factor for increased postoperative complications, more medical comorbidities, and increased LOS.^34,36 Older people are at higher risk of developing osteoarthritis and rotator cuff tear arthropathy and are more likely to undergo SA.^5,6 Older people also are more likely to be dependent, which itself is a risk factor for readmission.¹⁹ An ASA score of 3 or 4 has been found to be associated with increased LOS and complications after SA, and cardiac comorbidities predispose patients to a variety of complications.^34,36,37In studies that have combined surgical and medical factors, rates of complications early after ATSA and RTSA have ranged from 3.6% to 17.8%.^26,38,39 After SAs, medical complications (80%) are more common than surgical complications (20%).³⁹ In the present cohort, many more readmissions were for medical complications (67%) than for surgical complications (33%). In addition, Schairer and colleagues³ found medical complications associated with more than 80% of readmissions after SA.³ Infection was the most common medical reason (pneumonia) and surgical reason (surgical-site infection) for readmission—consistent with findings of other studies.^3,35,40 Infection has accounted for 9.4% to 41.4% of readmissions after ATSA and RTSA.^3,14In joint arthroplasty, infection occurs more often in patients with coexisting medical comorbidities, leading to higher mortality and increased LOS.⁴¹ Prosthetic joint dislocation was common as well—similar to findings in other studies.^3,10In the present study, 33% of known readmission diagnoses were secondary to HACs. Surgical-site infection was the most common, followed by CAUTI, DVT, and PE. In another study, of knee and hip arthroplasties, HACs accounted for more than 40% of all complications and were the strongest predictor of early readmission.¹⁶ In SA studies, HACs were responsible for 9.3% to 34.5% of readmissions after ATSA and RTSA.^3,14 Our finding (33%) is more in line with Mahoney and colleagues¹⁴ (34.5%) than Schairer and colleagues³ (9.3%). One explanation for the large discrepancy with Schairer and colleagues³ is that UTI was not among the medical reasons for readmission in their study, but it was in ours. Another difference is that we used a database that included data from multiple institutions. Last, Schairer and colleagues³ excluded revision SAs from their analysis (complication rates are higher for revision SAs than for primary SAs³⁰). They also excluded cases of SA used for fracture (shown to increase the risk for PE⁴²). The US Department of Health and Human Services estimated that patients experienced 1.3 million fewer HACs during the period 2010-2013, corresponding to a 17% decline over the 3 years.⁴³ This translates to an estimated 50,000 fewer mortalities, and $12 billion saved in healthcare costs, over the same period.⁴³ Preventing HACs helps reduce readmission rates while improving patient outcomes and decreasing healthcare costs.

This study had several limitations. We could not differentiate between ATSA and RTSA readmission rates because, for the study period, these procedures are collectively organized under a common CPT code in the NSQIP database. Readmission and complication rates are higher for RTSAs than for ATSAs.^3,14 In addition, our data were limited to hospitals that were participating in NSQIP, which could lead to selection bias. We studied rates of only those readmissions and complications that occurred within 30 days, but many complications develop after 30 days, and these increase the readmission rate. Last, reasons for readmission were not recorded for 2011, so this information was available only for the final 2 years of the study. Despite these limitations, NSQIP still allows for a powerful study, as it includes multiple institutions and a very large cohort.

Conclusion

With medical costs increasing, focus has shifted to quality care and good outcomes with the goal of reducing readmissions and complications after various procedures. SA has recently become more popular because of its multiple indications, and this trend will continue. In the present study, the rate of readmission within 30 days after ATSA or RTSA was 2.7%. Revision surgery, 3 or more comorbidities, and extended LOS were independent risk factors that more than doubled the risk of readmission. Understanding the risk factors for short-term readmission will allow for better patient care and decreased costs, and will benefit the healthcare system as a whole.

Am J Orthop. 2016;45(6):E386-E392. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Venous thromboembolism (VTE) after shoulder arthroplasty (SA) is relatively uncommon. Reported rates of VTE development are highly variable, ranging from 0.2% to 13% (pulmonary embolism [PE], 0.2%-10.8%; deep venous thrombosis [DVT], 0.1%-13%).^1-4 Sources of this variability include different methods of capturing cases (small clinical series vs large database studies, which capture mainly hospital readmissions), differences in defining or detecting VTE, and different patient populations (fracture vs osteoarthritis).^1-3 Most studies have also tried to identify factors associated with increased risk for VTE. Risk factors associated with development of VTE after SA include history of VTE, advanced age, prolonged operating room time, higher body mass index (BMI), trauma, history of cancer, female sex, and raised Charlson Comorbidity Index (CCI).^1-7 Limitations of clinical series include the smaller number of reporting institutions—a potential source of bias given regional variability.^1,3,4,7 Limitations of large state or national databases include capturing only events coded during inpatient admission and capturing readmissions for complications at the same institution. This underreporting may lead to very conservative estimates of VTE incidence.^2,5,6,8

In this study, we retrospectively identified all the SAs performed at a single institution over a 13-year period and evaluated the cases for development of VTE (DVT, PE). We hypothesized that the VTE rate would be lower than the very high rates reported by Hoxie and colleagues¹ and Willis and colleagues⁴ but higher than those reported for large state or national databases.^2,3 We also evaluated clotting risk factors, including many never analyzed before.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we searched our database for all SAs performed at our institution between January 1999 and May 2012 and identified cases in which symptomatic VTE developed within the first 90 days after surgery. Charts were reviewed for information on medical history, surgical procedure, and in-hospital and out-of-hospital care within the 90-day postoperative period. We recorded data on symptomatic VTE (DVT, PE) as documented by lower or upper extremity duplex ultrasonography (US) or chest computed tomography (CT) angiography. There had been no routine screening of patients; duplex US or CT angiography was performed only if a patient was clinically symptomatic (leg swelling, leg pain, shortness of breath, tachycardia, chest pain) for a potential DVT or PE. For a patient who had repeat SAs on the same shoulder or bilateral SAs at different times, only the first procedure was included in the analysis. Arthroplasties performed for fracture were excluded.

Study data were collected and managed with REDCap (Research Electronic Data Capture) tools hosted at the University of Utah School of Medicine.⁹ Continuous and discrete data collected on medical history and postoperative course included BMI, age at surgery, preoperative hemoglobin (Hb) and hematocrit (Hct) levels, days in hospital, days until out of bed and days until ambulation (both documented in nursing and physical therapy notes), postoperative Hb and Hct levels, and CCI. Categorical data included sex, diagnosis (primary osteoarthritis, rotator cuff arthropathy, rheumatoid arthritis, failed hemiarthroplasty [HA], failed total SA [TSA], others), attending surgeon, procedure (TSA, HA, reverse TSA, revision SA), anesthesia (general endotracheal anesthesia [GETA] alone, interscalene nerve block alone, GETA plus block), prophylactic use of aspirin after surgery, presence of various medical comorbidities (diabetes, hypertension, cardiac disease, clotting disorders, cancer), hormone replacement therapy, family history of a clotting disorder, and VTE consequences (cardiac events, death).

Statistical Analysis

Descriptive statistics were calculated to summarize aspects of the surgical procedures, the study cohort’s demographics and medical histories, and the incidence of VTE. Logistic regression analysis was performed to explore the association between development of VTE (DVT, PE) and potential risk factors. Unadjusted odds ratios (ORs) were estimated for the risk factors of age, BMI, revision SA, CCI, prophylactic use of aspirin after surgery, preoperative history of VTE, preoperative and postoperative Hb and Hct levels, diabetes, anesthesia (GETA with and without interscalene nerve block), family history of a clotting disorder, days until out of bed, hormone replacement therapy, race, discharge home or to rehabilitation, distance traveled for surgery, hypertension, cardiac disease, cement use, and history of cancer. In addition, ORs were adjusted for age, BMI, and revision SA. For all statistical tests, significance was set at P < .05. All analyses were performed with SAS Version 9.3 (SAS Institute).

Results

We identified 533 SAs: 245 anatomical TSAs, 112 reverse TSAs, 92 HAs, and 84 revision SAs. Three different surgeons performed the procedures, and no patients were lost to follow-up within the first 90 days after surgery. Although SAs were performed for various diagnoses, more than 50% (274) of the SAs were for primary osteoarthritis; 97 were performed for rotator cuff arthropathy, 16 for rheumatoid arthritis, 43 for failed HA, 23 for failed TSA, and 79 for other diagnoses.

Of the 533 patients, 288 were female and 245 were male. Mean age at surgery was 65.2 years (range, 16-93 years). Mean (SD) BMI was 29.2 (6.4) kg/m². Mean (SD) preoperative Hb level was 13.7 (1.8) g/dL, and mean preoperative Hct level was 40.1% (4.8%). Mean (SD) length of hospital stay was 2.6 (1.5) days. Mean (SD) time before patients were out of bed was 1.1 (0.7) days. On postoperative day 1, mean Hb level was 11.1 (1.7) g/dL, and mean (SD) Hct level was 33.2% (4.8%). Mean (SD) CCI was 1.1 (0.9).

Anesthesia for the 533 patients consisted of GETA (209 patients, 39.0%), interscalene nerve block (2, 0.4%), or GETA with nerve block (314, 59.0%). After surgery, 125 patients (24.3%) received aspirin as prophylaxis. Diabetes was reported by 83 patients, hypertension by 286, cardiac disease by 74, a history of a clotting disorder by 2, a family history of a clotting disorder by 8, ongoing cancer by 4, a history of cancer by 67, and hormone replacement therapy by 104.

For the entire cohort of 533 patients, the symptomatic VTE rate was 2.6% (14 patients), the DVT rate was 0.9% (5), and the PE rate was 2.3% (12). Although VTE did not cause any deaths, there were 3 cardiac events.

Discussion

VTE after SA is rare. We report an overall VTE incidence of 2.6%, with DVT at 0.9% and PE at 2.3%. These rates are similar to those reported in clinical series and significantly higher than those reported for large institutional or national databases.^2-7 Our results also support a previously reported trend: The ratio of PE to DVT for SA is significantly higher than historically reported ratios for lower extremity arthroplasty.^2,6-8 We have identified many VTE risk factors: raised CCI, preoperative thrombotic event, lower preoperative Hb and Hct levels, lower postoperative Hb level, diabetes, use of GETA without interscalene nerve block, higher BMI, and revision SA. Results of other studies support 3 findings (higher BMI, raised CCI, preoperative thrombotic event); new findings include correlation with Hb and Hct levels, diabetes, type of anesthesia, and revision SA.^6,7 Identification of these other factors may be useful in making treatment decisions in patients symptomatic after SA and in lowering the threshold for performing diagnostic tests in these patients at risk for VTE.

Reported rates of VTE after SA are highly variable, ranging from 0.2% to 13%.¹⁰ Our rationale for investigating VTE rates at a single institution was to estimate the rates that can be expected in a university-based practice and to determine whether these rates are high enough to warrant routine thromboprophylaxis. The rate variability seems to result in part from variability in the data sources. Most studies that have reported very low VTE rates typically used large state or national databases, which likely were subject to underreporting.

Lyman and colleagues⁶ found 0.5% DVT and 0.2% PE rates in a New York state hospital database, but only in-hospital immediate postoperative symptomatic complications were included; slightly delayed complications may have been missed. Farng and colleagues⁵ reported a 0.6% VTE rate, but only inpatient (immediate postoperative or readmission) events were included; all outpatient events were missed. Jameson and colleagues,² using a national database that included only cases involving inpatient treatment, reported 0% DVT and 0.2% PE rates, again missing outpatient events, and relying on appropriate coding to capture events. Using electronic health records from a large healthcare system, Navarro and colleagues⁸ queried for VTE cases and reported 0.5% DVT and 0.5% PE rates. The inclusiveness of their data source for the outcome of interest was potentially improved relative to national or statewide databases—and the resulting data reported in their study should reflect that improvement. However, the authors relied on ICD–9 (International Classification of Diseases, Ninth Revision) coding to screen for VTE events and excluded patients with prior VTE, preoperative prophylaxis (enoxaparin or warfarin), or follow-up of <90 days. As patients with prior VTE are those most at risk (present study OR, 6-7), excluding them significantly reduces the overall incidence of clotting reported.

Only 4 studies specifically used information drawn directly from physicians’ clinic notes, vs data retrieved (using code-based queries) from databases.^1,3,4,7 These studies may provide a better representation of the rate of VTE after SA, as they were not reliant on codes, included both inpatient and outpatient events, and were inclusive of outpatient follow-up of at least 3 months.

Three of the 4 studies used the Mayo Clinic Total Joint Registry.^1,3,4 Hoxie and colleagues¹ reported an 11% rate of PE after HA performed for fracture (we excluded SA for fracture). As several other investigators have reported an association between trauma and increased risk for VTE, postoperative anticoagulation should be considered in this patient population (though it was not the focus of the present study).^6-8 Sperling and Cofield³ and Singh and colleagues⁷ reported on the risk for PE among SA patients at the Mayo Clinic. Sperling and Cofield³ included only those events that occurred within the first 7 days after surgery; Singh and colleagues⁷ included events out to 90 days after surgery. Sperling and Cofield³ reported a 0.17% PE rate; Singh and colleagues⁷ reported 0.6% PE and 0.1% DVT rates. Sperling and Cofield³ reported on 2885 SAs; Singh and colleagues⁷ reported on 4019 SAs from the same database. As it is unclear whether these 2 studies had complete information on all patients, underreporting may be an issue. Information was obtained through “clinic visits, medical records and/or standardized mailed and telephone-administered questionnaires.”⁷The fourth study, a prospective study of 100 patients by Willis and colleagues,⁴ had the best data on development of symptomatic PE after SA. The authors reported a 2% PE rate and a high (13%) DVT rate. Because US was not performed before the surgical procedures, the number of patients with new and existing DVT cases could not be determined. However, all PEs were new, and the 2% rate found there is similar to the 2.3% in our study. Therefore, we think these rates capture the data most accurately and avoid the underreporting that marks large databases.⁴Studies have identified various factors that increase the risk for VTE after SA. Singh and colleagues⁷ identified the risk factors of age over 70 years, female sex, higher BMI (25-29.9 kg/m²), CCI above 1, traumatic etiology, prior history of VTE, and HA. However, their use of univariate regression analysis may have confounded the effects—one factor may have become a surrogate for another (ie, trauma and HA, as most fractures treated with SA during the study period were treated with HA). Lyman and colleagues⁶ also found advanced age and trauma were associated with higher VTE risk, and reported prior history of cancer as a risk factor as well. Navarro and colleagues⁸ identified trauma as a risk factor, as in the other 2 studies.^6,7 Our data support prior history of VTE, higher BMI, and raised CCI as increasing the risk for VTE.

Other factors identified in the present study are use of GETA without interscalene nerve block, lower preoperative and postoperative Hb levels, diabetes, and revision SA. Because of the limited number of events, only ORs with and without limited control of confounders were performed. Just as in the study by Singh and colleagues,⁷ uncontrolled confounding could have occurred. A nerve block may be protective, as less postoperative pain may allow patients quicker mobilization and therapy. Diabetes may be a surrogate for other medical comorbidities, as reflected by the higher overall risk with raised CCI. Lower preoperative and postoperative Hb levels were associated with clotting and may be representative of patients with poorer overall health and more complicated surgical procedures (eg, revision SA). In an earlier study, we found increased risk for transfusions in revision SA relative to primary SA.¹¹ Lower preoperative Hb level correlated with development of VTE after lower extremity arthroplasty.¹² Postoperative use of aspirin was not found to significantly reduce the incidence of clotting, though this finding may have resulted from lack of power. Therefore, from the present data, there is nothing to conclude about the efficacy of aspirin in preventing thrombosis.

Our findings can be placed in the context of the Virchow triad. Specifically, 3 categories of factors are thought to contribute to thrombosis: hypercoagulability, hemodynamic stasis, and endothelial injury. In grouping factors, we identified prior thrombotic event and obesity as increasing hypercoagulability; revision SA, more comorbidities, lower Hb and Hct levels, diabetes, and GETA as increasing hemodynamic stasis; and revision SA (longer operating room times) as leading to stasis. More comorbidities can be associated with delayed postoperative ambulation, and diabetes and lower Hb and Hct levels can be surrogates for more comorbidities. Surgery performed with the patient under GETA without interscalene nerve block can lead to higher levels of pain and less early mobility.

The present findings have made us more aware of patients at risk for VTE, and we have lowered our threshold for evaluating them for potential clots. Before this study, we used warfarin or enoxaparin for anticoagulation in patients with a history of VTE or active cancer. We are continuing this protocol, but not with other patients. Patients with many comorbidities, lower preoperative Hb level, revision SA, high BMI, or diabetes are carefully monitored for clots early in the postoperative course. Our new threshold for these high-risk patients is to order diagnostic testing, including duplex US or CT angiography. Now, even mild oxygen requirements or mild tachycardia within postoperative week 1 typically prompt a study in these patients. We hope this increased awareness will limit the potential negative consequences associated with development of VTE. Given the present data, we do not think the simple presence of increased comorbidities, lower preoperative Hb, revision SA, high BMI or diabetes should rule out performing SA; rather, it should increase surgeons’ postoperative vigilance in evaluating for potential clots.

Limitations of our study include its retrospective nature and reliance on clinic chart review. Patients were not directly questioned about venous thrombus at follow-up, so all events may not have been captured. Although retrospective review has its drawbacks, it allows for accurate identification of events, even uncoded events. Therefore, more events are likely to be captured with this technique than with large database analyses using only coding information. We tried to identify as many cases as possible by reviewing all outpatient records (orthopedic, nonorthopedic), inpatient records, radiologic studies, and scanned outside records. Another limitation is that having a small number of VTE events limited our ability to perform a multivariate analysis, and uncontrolled confounding likely resulted. Only a very large multi-institutional study can capture enough events to allow a multivariate analysis. A third limitation is that the small number of events may have underpowered the study. Having more patients would have allowed other potential factors to be identified as being significantly associated with VTE. Last, as the study captured only symptomatic VTE events, it may have underreported VTE events. Given our complete review of the medical records, however, most clinically significant events likely were captured.

Conclusion

VTE after SA is rare. In our single-institution study, the symptomatic DVT rate was 0.9%, and the symptomatic PE rate was 2.3%. Risk factors associated with clotting included prior VTE, higher BMI, lower preoperative and postoperative Hb levels, raised CCI, diabetes, use of GETA without interscalene nerve block, and revision SA. Risk factors can be used to identify patients who may benefit from a more scrutinized postoperative evaluation and from increased surgeon awareness of the potential for VTE development. Rates of VTE can be used to counsel SA patients regarding overall surgical risks.

Am J Orthop. 2016;45(6):E379-E385. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Venous thromboembolism (VTE) after shoulder arthroplasty (SA) is relatively uncommon. Reported rates of VTE development are highly variable, ranging from 0.2% to 13% (pulmonary embolism [PE], 0.2%-10.8%; deep venous thrombosis [DVT], 0.1%-13%).^1-4 Sources of this variability include different methods of capturing cases (small clinical series vs large database studies, which capture mainly hospital readmissions), differences in defining or detecting VTE, and different patient populations (fracture vs osteoarthritis).^1-3 Most studies have also tried to identify factors associated with increased risk for VTE. Risk factors associated with development of VTE after SA include history of VTE, advanced age, prolonged operating room time, higher body mass index (BMI), trauma, history of cancer, female sex, and raised Charlson Comorbidity Index (CCI).^1-7 Limitations of clinical series include the smaller number of reporting institutions—a potential source of bias given regional variability.^1,3,4,7 Limitations of large state or national databases include capturing only events coded during inpatient admission and capturing readmissions for complications at the same institution. This underreporting may lead to very conservative estimates of VTE incidence.^2,5,6,8

In this study, we retrospectively identified all the SAs performed at a single institution over a 13-year period and evaluated the cases for development of VTE (DVT, PE). We hypothesized that the VTE rate would be lower than the very high rates reported by Hoxie and colleagues¹ and Willis and colleagues⁴ but higher than those reported for large state or national databases.^2,3 We also evaluated clotting risk factors, including many never analyzed before.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we searched our database for all SAs performed at our institution between January 1999 and May 2012 and identified cases in which symptomatic VTE developed within the first 90 days after surgery. Charts were reviewed for information on medical history, surgical procedure, and in-hospital and out-of-hospital care within the 90-day postoperative period. We recorded data on symptomatic VTE (DVT, PE) as documented by lower or upper extremity duplex ultrasonography (US) or chest computed tomography (CT) angiography. There had been no routine screening of patients; duplex US or CT angiography was performed only if a patient was clinically symptomatic (leg swelling, leg pain, shortness of breath, tachycardia, chest pain) for a potential DVT or PE. For a patient who had repeat SAs on the same shoulder or bilateral SAs at different times, only the first procedure was included in the analysis. Arthroplasties performed for fracture were excluded.

Study data were collected and managed with REDCap (Research Electronic Data Capture) tools hosted at the University of Utah School of Medicine.⁹ Continuous and discrete data collected on medical history and postoperative course included BMI, age at surgery, preoperative hemoglobin (Hb) and hematocrit (Hct) levels, days in hospital, days until out of bed and days until ambulation (both documented in nursing and physical therapy notes), postoperative Hb and Hct levels, and CCI. Categorical data included sex, diagnosis (primary osteoarthritis, rotator cuff arthropathy, rheumatoid arthritis, failed hemiarthroplasty [HA], failed total SA [TSA], others), attending surgeon, procedure (TSA, HA, reverse TSA, revision SA), anesthesia (general endotracheal anesthesia [GETA] alone, interscalene nerve block alone, GETA plus block), prophylactic use of aspirin after surgery, presence of various medical comorbidities (diabetes, hypertension, cardiac disease, clotting disorders, cancer), hormone replacement therapy, family history of a clotting disorder, and VTE consequences (cardiac events, death).

Statistical Analysis

Descriptive statistics were calculated to summarize aspects of the surgical procedures, the study cohort’s demographics and medical histories, and the incidence of VTE. Logistic regression analysis was performed to explore the association between development of VTE (DVT, PE) and potential risk factors. Unadjusted odds ratios (ORs) were estimated for the risk factors of age, BMI, revision SA, CCI, prophylactic use of aspirin after surgery, preoperative history of VTE, preoperative and postoperative Hb and Hct levels, diabetes, anesthesia (GETA with and without interscalene nerve block), family history of a clotting disorder, days until out of bed, hormone replacement therapy, race, discharge home or to rehabilitation, distance traveled for surgery, hypertension, cardiac disease, cement use, and history of cancer. In addition, ORs were adjusted for age, BMI, and revision SA. For all statistical tests, significance was set at P < .05. All analyses were performed with SAS Version 9.3 (SAS Institute).

Results

We identified 533 SAs: 245 anatomical TSAs, 112 reverse TSAs, 92 HAs, and 84 revision SAs. Three different surgeons performed the procedures, and no patients were lost to follow-up within the first 90 days after surgery. Although SAs were performed for various diagnoses, more than 50% (274) of the SAs were for primary osteoarthritis; 97 were performed for rotator cuff arthropathy, 16 for rheumatoid arthritis, 43 for failed HA, 23 for failed TSA, and 79 for other diagnoses.

Of the 533 patients, 288 were female and 245 were male. Mean age at surgery was 65.2 years (range, 16-93 years). Mean (SD) BMI was 29.2 (6.4) kg/m². Mean (SD) preoperative Hb level was 13.7 (1.8) g/dL, and mean preoperative Hct level was 40.1% (4.8%). Mean (SD) length of hospital stay was 2.6 (1.5) days. Mean (SD) time before patients were out of bed was 1.1 (0.7) days. On postoperative day 1, mean Hb level was 11.1 (1.7) g/dL, and mean (SD) Hct level was 33.2% (4.8%). Mean (SD) CCI was 1.1 (0.9).

Anesthesia for the 533 patients consisted of GETA (209 patients, 39.0%), interscalene nerve block (2, 0.4%), or GETA with nerve block (314, 59.0%). After surgery, 125 patients (24.3%) received aspirin as prophylaxis. Diabetes was reported by 83 patients, hypertension by 286, cardiac disease by 74, a history of a clotting disorder by 2, a family history of a clotting disorder by 8, ongoing cancer by 4, a history of cancer by 67, and hormone replacement therapy by 104.

For the entire cohort of 533 patients, the symptomatic VTE rate was 2.6% (14 patients), the DVT rate was 0.9% (5), and the PE rate was 2.3% (12). Although VTE did not cause any deaths, there were 3 cardiac events.

Discussion

VTE after SA is rare. We report an overall VTE incidence of 2.6%, with DVT at 0.9% and PE at 2.3%. These rates are similar to those reported in clinical series and significantly higher than those reported for large institutional or national databases.^2-7 Our results also support a previously reported trend: The ratio of PE to DVT for SA is significantly higher than historically reported ratios for lower extremity arthroplasty.^2,6-8 We have identified many VTE risk factors: raised CCI, preoperative thrombotic event, lower preoperative Hb and Hct levels, lower postoperative Hb level, diabetes, use of GETA without interscalene nerve block, higher BMI, and revision SA. Results of other studies support 3 findings (higher BMI, raised CCI, preoperative thrombotic event); new findings include correlation with Hb and Hct levels, diabetes, type of anesthesia, and revision SA.^6,7 Identification of these other factors may be useful in making treatment decisions in patients symptomatic after SA and in lowering the threshold for performing diagnostic tests in these patients at risk for VTE.

Reported rates of VTE after SA are highly variable, ranging from 0.2% to 13%.¹⁰ Our rationale for investigating VTE rates at a single institution was to estimate the rates that can be expected in a university-based practice and to determine whether these rates are high enough to warrant routine thromboprophylaxis. The rate variability seems to result in part from variability in the data sources. Most studies that have reported very low VTE rates typically used large state or national databases, which likely were subject to underreporting.

Lyman and colleagues⁶ found 0.5% DVT and 0.2% PE rates in a New York state hospital database, but only in-hospital immediate postoperative symptomatic complications were included; slightly delayed complications may have been missed. Farng and colleagues⁵ reported a 0.6% VTE rate, but only inpatient (immediate postoperative or readmission) events were included; all outpatient events were missed. Jameson and colleagues,² using a national database that included only cases involving inpatient treatment, reported 0% DVT and 0.2% PE rates, again missing outpatient events, and relying on appropriate coding to capture events. Using electronic health records from a large healthcare system, Navarro and colleagues⁸ queried for VTE cases and reported 0.5% DVT and 0.5% PE rates. The inclusiveness of their data source for the outcome of interest was potentially improved relative to national or statewide databases—and the resulting data reported in their study should reflect that improvement. However, the authors relied on ICD–9 (International Classification of Diseases, Ninth Revision) coding to screen for VTE events and excluded patients with prior VTE, preoperative prophylaxis (enoxaparin or warfarin), or follow-up of <90 days. As patients with prior VTE are those most at risk (present study OR, 6-7), excluding them significantly reduces the overall incidence of clotting reported.

Only 4 studies specifically used information drawn directly from physicians’ clinic notes, vs data retrieved (using code-based queries) from databases.^1,3,4,7 These studies may provide a better representation of the rate of VTE after SA, as they were not reliant on codes, included both inpatient and outpatient events, and were inclusive of outpatient follow-up of at least 3 months.

Three of the 4 studies used the Mayo Clinic Total Joint Registry.^1,3,4 Hoxie and colleagues¹ reported an 11% rate of PE after HA performed for fracture (we excluded SA for fracture). As several other investigators have reported an association between trauma and increased risk for VTE, postoperative anticoagulation should be considered in this patient population (though it was not the focus of the present study).^6-8 Sperling and Cofield³ and Singh and colleagues⁷ reported on the risk for PE among SA patients at the Mayo Clinic. Sperling and Cofield³ included only those events that occurred within the first 7 days after surgery; Singh and colleagues⁷ included events out to 90 days after surgery. Sperling and Cofield³ reported a 0.17% PE rate; Singh and colleagues⁷ reported 0.6% PE and 0.1% DVT rates. Sperling and Cofield³ reported on 2885 SAs; Singh and colleagues⁷ reported on 4019 SAs from the same database. As it is unclear whether these 2 studies had complete information on all patients, underreporting may be an issue. Information was obtained through “clinic visits, medical records and/or standardized mailed and telephone-administered questionnaires.”⁷The fourth study, a prospective study of 100 patients by Willis and colleagues,⁴ had the best data on development of symptomatic PE after SA. The authors reported a 2% PE rate and a high (13%) DVT rate. Because US was not performed before the surgical procedures, the number of patients with new and existing DVT cases could not be determined. However, all PEs were new, and the 2% rate found there is similar to the 2.3% in our study. Therefore, we think these rates capture the data most accurately and avoid the underreporting that marks large databases.⁴Studies have identified various factors that increase the risk for VTE after SA. Singh and colleagues⁷ identified the risk factors of age over 70 years, female sex, higher BMI (25-29.9 kg/m²), CCI above 1, traumatic etiology, prior history of VTE, and HA. However, their use of univariate regression analysis may have confounded the effects—one factor may have become a surrogate for another (ie, trauma and HA, as most fractures treated with SA during the study period were treated with HA). Lyman and colleagues⁶ also found advanced age and trauma were associated with higher VTE risk, and reported prior history of cancer as a risk factor as well. Navarro and colleagues⁸ identified trauma as a risk factor, as in the other 2 studies.^6,7 Our data support prior history of VTE, higher BMI, and raised CCI as increasing the risk for VTE.

Other factors identified in the present study are use of GETA without interscalene nerve block, lower preoperative and postoperative Hb levels, diabetes, and revision SA. Because of the limited number of events, only ORs with and without limited control of confounders were performed. Just as in the study by Singh and colleagues,⁷ uncontrolled confounding could have occurred. A nerve block may be protective, as less postoperative pain may allow patients quicker mobilization and therapy. Diabetes may be a surrogate for other medical comorbidities, as reflected by the higher overall risk with raised CCI. Lower preoperative and postoperative Hb levels were associated with clotting and may be representative of patients with poorer overall health and more complicated surgical procedures (eg, revision SA). In an earlier study, we found increased risk for transfusions in revision SA relative to primary SA.¹¹ Lower preoperative Hb level correlated with development of VTE after lower extremity arthroplasty.¹² Postoperative use of aspirin was not found to significantly reduce the incidence of clotting, though this finding may have resulted from lack of power. Therefore, from the present data, there is nothing to conclude about the efficacy of aspirin in preventing thrombosis.

Our findings can be placed in the context of the Virchow triad. Specifically, 3 categories of factors are thought to contribute to thrombosis: hypercoagulability, hemodynamic stasis, and endothelial injury. In grouping factors, we identified prior thrombotic event and obesity as increasing hypercoagulability; revision SA, more comorbidities, lower Hb and Hct levels, diabetes, and GETA as increasing hemodynamic stasis; and revision SA (longer operating room times) as leading to stasis. More comorbidities can be associated with delayed postoperative ambulation, and diabetes and lower Hb and Hct levels can be surrogates for more comorbidities. Surgery performed with the patient under GETA without interscalene nerve block can lead to higher levels of pain and less early mobility.

The present findings have made us more aware of patients at risk for VTE, and we have lowered our threshold for evaluating them for potential clots. Before this study, we used warfarin or enoxaparin for anticoagulation in patients with a history of VTE or active cancer. We are continuing this protocol, but not with other patients. Patients with many comorbidities, lower preoperative Hb level, revision SA, high BMI, or diabetes are carefully monitored for clots early in the postoperative course. Our new threshold for these high-risk patients is to order diagnostic testing, including duplex US or CT angiography. Now, even mild oxygen requirements or mild tachycardia within postoperative week 1 typically prompt a study in these patients. We hope this increased awareness will limit the potential negative consequences associated with development of VTE. Given the present data, we do not think the simple presence of increased comorbidities, lower preoperative Hb, revision SA, high BMI or diabetes should rule out performing SA; rather, it should increase surgeons’ postoperative vigilance in evaluating for potential clots.

Limitations of our study include its retrospective nature and reliance on clinic chart review. Patients were not directly questioned about venous thrombus at follow-up, so all events may not have been captured. Although retrospective review has its drawbacks, it allows for accurate identification of events, even uncoded events. Therefore, more events are likely to be captured with this technique than with large database analyses using only coding information. We tried to identify as many cases as possible by reviewing all outpatient records (orthopedic, nonorthopedic), inpatient records, radiologic studies, and scanned outside records. Another limitation is that having a small number of VTE events limited our ability to perform a multivariate analysis, and uncontrolled confounding likely resulted. Only a very large multi-institutional study can capture enough events to allow a multivariate analysis. A third limitation is that the small number of events may have underpowered the study. Having more patients would have allowed other potential factors to be identified as being significantly associated with VTE. Last, as the study captured only symptomatic VTE events, it may have underreported VTE events. Given our complete review of the medical records, however, most clinically significant events likely were captured.

Conclusion

VTE after SA is rare. In our single-institution study, the symptomatic DVT rate was 0.9%, and the symptomatic PE rate was 2.3%. Risk factors associated with clotting included prior VTE, higher BMI, lower preoperative and postoperative Hb levels, raised CCI, diabetes, use of GETA without interscalene nerve block, and revision SA. Risk factors can be used to identify patients who may benefit from a more scrutinized postoperative evaluation and from increased surgeon awareness of the potential for VTE development. Rates of VTE can be used to counsel SA patients regarding overall surgical risks.

Am J Orthop. 2016;45(6):E379-E385. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Venous thromboembolism (VTE) after shoulder arthroplasty (SA) is relatively uncommon. Reported rates of VTE development are highly variable, ranging from 0.2% to 13% (pulmonary embolism [PE], 0.2%-10.8%; deep venous thrombosis [DVT], 0.1%-13%).^1-4 Sources of this variability include different methods of capturing cases (small clinical series vs large database studies, which capture mainly hospital readmissions), differences in defining or detecting VTE, and different patient populations (fracture vs osteoarthritis).^1-3 Most studies have also tried to identify factors associated with increased risk for VTE. Risk factors associated with development of VTE after SA include history of VTE, advanced age, prolonged operating room time, higher body mass index (BMI), trauma, history of cancer, female sex, and raised Charlson Comorbidity Index (CCI).^1-7 Limitations of clinical series include the smaller number of reporting institutions—a potential source of bias given regional variability.^1,3,4,7 Limitations of large state or national databases include capturing only events coded during inpatient admission and capturing readmissions for complications at the same institution. This underreporting may lead to very conservative estimates of VTE incidence.^2,5,6,8

In this study, we retrospectively identified all the SAs performed at a single institution over a 13-year period and evaluated the cases for development of VTE (DVT, PE). We hypothesized that the VTE rate would be lower than the very high rates reported by Hoxie and colleagues¹ and Willis and colleagues⁴ but higher than those reported for large state or national databases.^2,3 We also evaluated clotting risk factors, including many never analyzed before.

Materials and Methods

After obtaining Institutional Review Board approval for this study, we searched our database for all SAs performed at our institution between January 1999 and May 2012 and identified cases in which symptomatic VTE developed within the first 90 days after surgery. Charts were reviewed for information on medical history, surgical procedure, and in-hospital and out-of-hospital care within the 90-day postoperative period. We recorded data on symptomatic VTE (DVT, PE) as documented by lower or upper extremity duplex ultrasonography (US) or chest computed tomography (CT) angiography. There had been no routine screening of patients; duplex US or CT angiography was performed only if a patient was clinically symptomatic (leg swelling, leg pain, shortness of breath, tachycardia, chest pain) for a potential DVT or PE. For a patient who had repeat SAs on the same shoulder or bilateral SAs at different times, only the first procedure was included in the analysis. Arthroplasties performed for fracture were excluded.

Study data were collected and managed with REDCap (Research Electronic Data Capture) tools hosted at the University of Utah School of Medicine.⁹ Continuous and discrete data collected on medical history and postoperative course included BMI, age at surgery, preoperative hemoglobin (Hb) and hematocrit (Hct) levels, days in hospital, days until out of bed and days until ambulation (both documented in nursing and physical therapy notes), postoperative Hb and Hct levels, and CCI. Categorical data included sex, diagnosis (primary osteoarthritis, rotator cuff arthropathy, rheumatoid arthritis, failed hemiarthroplasty [HA], failed total SA [TSA], others), attending surgeon, procedure (TSA, HA, reverse TSA, revision SA), anesthesia (general endotracheal anesthesia [GETA] alone, interscalene nerve block alone, GETA plus block), prophylactic use of aspirin after surgery, presence of various medical comorbidities (diabetes, hypertension, cardiac disease, clotting disorders, cancer), hormone replacement therapy, family history of a clotting disorder, and VTE consequences (cardiac events, death).

Statistical Analysis

Descriptive statistics were calculated to summarize aspects of the surgical procedures, the study cohort’s demographics and medical histories, and the incidence of VTE. Logistic regression analysis was performed to explore the association between development of VTE (DVT, PE) and potential risk factors. Unadjusted odds ratios (ORs) were estimated for the risk factors of age, BMI, revision SA, CCI, prophylactic use of aspirin after surgery, preoperative history of VTE, preoperative and postoperative Hb and Hct levels, diabetes, anesthesia (GETA with and without interscalene nerve block), family history of a clotting disorder, days until out of bed, hormone replacement therapy, race, discharge home or to rehabilitation, distance traveled for surgery, hypertension, cardiac disease, cement use, and history of cancer. In addition, ORs were adjusted for age, BMI, and revision SA. For all statistical tests, significance was set at P < .05. All analyses were performed with SAS Version 9.3 (SAS Institute).

Results

We identified 533 SAs: 245 anatomical TSAs, 112 reverse TSAs, 92 HAs, and 84 revision SAs. Three different surgeons performed the procedures, and no patients were lost to follow-up within the first 90 days after surgery. Although SAs were performed for various diagnoses, more than 50% (274) of the SAs were for primary osteoarthritis; 97 were performed for rotator cuff arthropathy, 16 for rheumatoid arthritis, 43 for failed HA, 23 for failed TSA, and 79 for other diagnoses.

Of the 533 patients, 288 were female and 245 were male. Mean age at surgery was 65.2 years (range, 16-93 years). Mean (SD) BMI was 29.2 (6.4) kg/m². Mean (SD) preoperative Hb level was 13.7 (1.8) g/dL, and mean preoperative Hct level was 40.1% (4.8%). Mean (SD) length of hospital stay was 2.6 (1.5) days. Mean (SD) time before patients were out of bed was 1.1 (0.7) days. On postoperative day 1, mean Hb level was 11.1 (1.7) g/dL, and mean (SD) Hct level was 33.2% (4.8%). Mean (SD) CCI was 1.1 (0.9).

Anesthesia for the 533 patients consisted of GETA (209 patients, 39.0%), interscalene nerve block (2, 0.4%), or GETA with nerve block (314, 59.0%). After surgery, 125 patients (24.3%) received aspirin as prophylaxis. Diabetes was reported by 83 patients, hypertension by 286, cardiac disease by 74, a history of a clotting disorder by 2, a family history of a clotting disorder by 8, ongoing cancer by 4, a history of cancer by 67, and hormone replacement therapy by 104.

For the entire cohort of 533 patients, the symptomatic VTE rate was 2.6% (14 patients), the DVT rate was 0.9% (5), and the PE rate was 2.3% (12). Although VTE did not cause any deaths, there were 3 cardiac events.

Discussion

VTE after SA is rare. We report an overall VTE incidence of 2.6%, with DVT at 0.9% and PE at 2.3%. These rates are similar to those reported in clinical series and significantly higher than those reported for large institutional or national databases.^2-7 Our results also support a previously reported trend: The ratio of PE to DVT for SA is significantly higher than historically reported ratios for lower extremity arthroplasty.^2,6-8 We have identified many VTE risk factors: raised CCI, preoperative thrombotic event, lower preoperative Hb and Hct levels, lower postoperative Hb level, diabetes, use of GETA without interscalene nerve block, higher BMI, and revision SA. Results of other studies support 3 findings (higher BMI, raised CCI, preoperative thrombotic event); new findings include correlation with Hb and Hct levels, diabetes, type of anesthesia, and revision SA.^6,7 Identification of these other factors may be useful in making treatment decisions in patients symptomatic after SA and in lowering the threshold for performing diagnostic tests in these patients at risk for VTE.

Reported rates of VTE after SA are highly variable, ranging from 0.2% to 13%.¹⁰ Our rationale for investigating VTE rates at a single institution was to estimate the rates that can be expected in a university-based practice and to determine whether these rates are high enough to warrant routine thromboprophylaxis. The rate variability seems to result in part from variability in the data sources. Most studies that have reported very low VTE rates typically used large state or national databases, which likely were subject to underreporting.

Lyman and colleagues⁶ found 0.5% DVT and 0.2% PE rates in a New York state hospital database, but only in-hospital immediate postoperative symptomatic complications were included; slightly delayed complications may have been missed. Farng and colleagues⁵ reported a 0.6% VTE rate, but only inpatient (immediate postoperative or readmission) events were included; all outpatient events were missed. Jameson and colleagues,² using a national database that included only cases involving inpatient treatment, reported 0% DVT and 0.2% PE rates, again missing outpatient events, and relying on appropriate coding to capture events. Using electronic health records from a large healthcare system, Navarro and colleagues⁸ queried for VTE cases and reported 0.5% DVT and 0.5% PE rates. The inclusiveness of their data source for the outcome of interest was potentially improved relative to national or statewide databases—and the resulting data reported in their study should reflect that improvement. However, the authors relied on ICD–9 (International Classification of Diseases, Ninth Revision) coding to screen for VTE events and excluded patients with prior VTE, preoperative prophylaxis (enoxaparin or warfarin), or follow-up of <90 days. As patients with prior VTE are those most at risk (present study OR, 6-7), excluding them significantly reduces the overall incidence of clotting reported.

Only 4 studies specifically used information drawn directly from physicians’ clinic notes, vs data retrieved (using code-based queries) from databases.^1,3,4,7 These studies may provide a better representation of the rate of VTE after SA, as they were not reliant on codes, included both inpatient and outpatient events, and were inclusive of outpatient follow-up of at least 3 months.

Three of the 4 studies used the Mayo Clinic Total Joint Registry.^1,3,4 Hoxie and colleagues¹ reported an 11% rate of PE after HA performed for fracture (we excluded SA for fracture). As several other investigators have reported an association between trauma and increased risk for VTE, postoperative anticoagulation should be considered in this patient population (though it was not the focus of the present study).^6-8 Sperling and Cofield³ and Singh and colleagues⁷ reported on the risk for PE among SA patients at the Mayo Clinic. Sperling and Cofield³ included only those events that occurred within the first 7 days after surgery; Singh and colleagues⁷ included events out to 90 days after surgery. Sperling and Cofield³ reported a 0.17% PE rate; Singh and colleagues⁷ reported 0.6% PE and 0.1% DVT rates. Sperling and Cofield³ reported on 2885 SAs; Singh and colleagues⁷ reported on 4019 SAs from the same database. As it is unclear whether these 2 studies had complete information on all patients, underreporting may be an issue. Information was obtained through “clinic visits, medical records and/or standardized mailed and telephone-administered questionnaires.”⁷The fourth study, a prospective study of 100 patients by Willis and colleagues,⁴ had the best data on development of symptomatic PE after SA. The authors reported a 2% PE rate and a high (13%) DVT rate. Because US was not performed before the surgical procedures, the number of patients with new and existing DVT cases could not be determined. However, all PEs were new, and the 2% rate found there is similar to the 2.3% in our study. Therefore, we think these rates capture the data most accurately and avoid the underreporting that marks large databases.⁴Studies have identified various factors that increase the risk for VTE after SA. Singh and colleagues⁷ identified the risk factors of age over 70 years, female sex, higher BMI (25-29.9 kg/m²), CCI above 1, traumatic etiology, prior history of VTE, and HA. However, their use of univariate regression analysis may have confounded the effects—one factor may have become a surrogate for another (ie, trauma and HA, as most fractures treated with SA during the study period were treated with HA). Lyman and colleagues⁶ also found advanced age and trauma were associated with higher VTE risk, and reported prior history of cancer as a risk factor as well. Navarro and colleagues⁸ identified trauma as a risk factor, as in the other 2 studies.^6,7 Our data support prior history of VTE, higher BMI, and raised CCI as increasing the risk for VTE.

Other factors identified in the present study are use of GETA without interscalene nerve block, lower preoperative and postoperative Hb levels, diabetes, and revision SA. Because of the limited number of events, only ORs with and without limited control of confounders were performed. Just as in the study by Singh and colleagues,⁷ uncontrolled confounding could have occurred. A nerve block may be protective, as less postoperative pain may allow patients quicker mobilization and therapy. Diabetes may be a surrogate for other medical comorbidities, as reflected by the higher overall risk with raised CCI. Lower preoperative and postoperative Hb levels were associated with clotting and may be representative of patients with poorer overall health and more complicated surgical procedures (eg, revision SA). In an earlier study, we found increased risk for transfusions in revision SA relative to primary SA.¹¹ Lower preoperative Hb level correlated with development of VTE after lower extremity arthroplasty.¹² Postoperative use of aspirin was not found to significantly reduce the incidence of clotting, though this finding may have resulted from lack of power. Therefore, from the present data, there is nothing to conclude about the efficacy of aspirin in preventing thrombosis.

Our findings can be placed in the context of the Virchow triad. Specifically, 3 categories of factors are thought to contribute to thrombosis: hypercoagulability, hemodynamic stasis, and endothelial injury. In grouping factors, we identified prior thrombotic event and obesity as increasing hypercoagulability; revision SA, more comorbidities, lower Hb and Hct levels, diabetes, and GETA as increasing hemodynamic stasis; and revision SA (longer operating room times) as leading to stasis. More comorbidities can be associated with delayed postoperative ambulation, and diabetes and lower Hb and Hct levels can be surrogates for more comorbidities. Surgery performed with the patient under GETA without interscalene nerve block can lead to higher levels of pain and less early mobility.

The present findings have made us more aware of patients at risk for VTE, and we have lowered our threshold for evaluating them for potential clots. Before this study, we used warfarin or enoxaparin for anticoagulation in patients with a history of VTE or active cancer. We are continuing this protocol, but not with other patients. Patients with many comorbidities, lower preoperative Hb level, revision SA, high BMI, or diabetes are carefully monitored for clots early in the postoperative course. Our new threshold for these high-risk patients is to order diagnostic testing, including duplex US or CT angiography. Now, even mild oxygen requirements or mild tachycardia within postoperative week 1 typically prompt a study in these patients. We hope this increased awareness will limit the potential negative consequences associated with development of VTE. Given the present data, we do not think the simple presence of increased comorbidities, lower preoperative Hb, revision SA, high BMI or diabetes should rule out performing SA; rather, it should increase surgeons’ postoperative vigilance in evaluating for potential clots.

Limitations of our study include its retrospective nature and reliance on clinic chart review. Patients were not directly questioned about venous thrombus at follow-up, so all events may not have been captured. Although retrospective review has its drawbacks, it allows for accurate identification of events, even uncoded events. Therefore, more events are likely to be captured with this technique than with large database analyses using only coding information. We tried to identify as many cases as possible by reviewing all outpatient records (orthopedic, nonorthopedic), inpatient records, radiologic studies, and scanned outside records. Another limitation is that having a small number of VTE events limited our ability to perform a multivariate analysis, and uncontrolled confounding likely resulted. Only a very large multi-institutional study can capture enough events to allow a multivariate analysis. A third limitation is that the small number of events may have underpowered the study. Having more patients would have allowed other potential factors to be identified as being significantly associated with VTE. Last, as the study captured only symptomatic VTE events, it may have underreported VTE events. Given our complete review of the medical records, however, most clinically significant events likely were captured.

Conclusion

VTE after SA is rare. In our single-institution study, the symptomatic DVT rate was 0.9%, and the symptomatic PE rate was 2.3%. Risk factors associated with clotting included prior VTE, higher BMI, lower preoperative and postoperative Hb levels, raised CCI, diabetes, use of GETA without interscalene nerve block, and revision SA. Risk factors can be used to identify patients who may benefit from a more scrutinized postoperative evaluation and from increased surgeon awareness of the potential for VTE development. Rates of VTE can be used to counsel SA patients regarding overall surgical risks.

Am J Orthop. 2016;45(6):E379-E385. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

End-stage osteoarthritis of the hip is a debilitating disease that is reliably treated with total hip arthroplasty (THA).¹ Up to 35% of patients who undergo THA eventually require contralateral THA.^2,3 In patients who present with advanced bilateral disease and undergo unilateral THA, the risk of ultimately requiring a contralateral procedure is as high as 97%.^3-6 In patients with bilateral hip disease, function is not fully optimized until both hips have been replaced, particularly in the setting of fixed flexion contractures.^7-9 Naturally, there has been some interest in simultaneous bilateral THAs for select patients.

The potential benefits of bilateral THAs over staged procedures include faster overall rehabilitation, exposure to a single anesthetic, reduced hospital length of stay (LOS), and cost savings.^10-12 However, opinion on recommending bilateral THAs is mixed. Although bilateral procedures historically have been fraught with perioperative complications,^13,14 advances in surgical and anesthetic techniques have led to improved outcomes.¹⁵ Whether surgical approach is a factor in these outcomes is unclear.

The popularity of the direct anterior (DA) approach for THA has increased in recent years.¹⁶ Although the relative advantages of various approaches remain in debate, one potential benefit of the DA approach is supine positioning, which allows simultaneous bilateral THAs to be performed without the need for repositioning before proceeding with the contralateral side. However, simultaneous bilateral THAs performed through the DA approach and those performed through other surgical approaches are lacking in comparative outcomes data.¹⁷In this study, we evaluated operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who had simultaneous bilateral THAs through either the DA approach or the posterior approach.

Methods

Study Design

This single-center study was conducted at the Mayo Clinic in Rochester, Minnesota. After obtaining approval from our Institutional Review Board, we performed a retrospective cohort analysis. We used our institution’s total joint registry to identify all patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach. The first bilateral THAs to use the DA approach at our institution were performed in 2012. To ensure that the DA and posterior groups’ perioperative management would be similar, we included only cases performed between 2012 and 2014.

There were 19 patients in the DA group and 21 in the posterior group. The groups were similar in mean age (54 vs 54 years; P = .90), sex (73% vs 57% males; P = .33), body mass index (BMI; 25 vs 28 kg/m²; P = .38), preoperative hemoglobin level (14.3 vs 14.0 g/dL; P = .37), preoperative diagnosis (71.1% vs 78.6% degenerative joint disease; P = .75), and American Society of Anesthesiologists (ASA) score (1.9 vs 2.0; P = .63) (Table 1).

Patient Care

All cases were performed by 1 of 3 dedicated arthroplasty surgeons (Dr. Taunton, Dr. Sierra, Dr. Trousdale). Dr. Taunton exclusively uses the DA approach, and Dr. Sierra and Dr. Trousdale exclusively use the posterior approach. Patients in both groups received preoperative medical clearance and attended the same preoperative education class.

Patients in the DA group were positioned supine on an orthopedic table that allows hyperextension and adduction of the operative leg. Both hips were prepared and draped simultaneously. The most symptomatic hip was operated on first, with a sterile drape covering the contralateral hip. Between hips, fluoroscopy was moved to the other side of the operative suite, but no changes in positioning or preparation were necessary. A deep drain was placed on each side, and then was removed the morning of postoperative day 1. The same set of instruments was used on both sides.

Patients in the posterior group were positioned lateral on a regular operative table with hip rests. The most symptomatic hip was operated on first. After wound closure and dressing application, the patient was flipped to allow access to the contralateral hip and was prepared and draped again. The same instruments were used on each side. Drains were not used.

All patients received the same comprehensive multimodal pain management, which combined general and epidural anesthesia (remaining in place until postoperative day 2) and included an oral pain regimen of scheduled acetaminophen and as-needed tramadol and oxycodone. In all cases, intraoperative blood salvage and intravenous tranexamic acid (1 g at time of incision on first hip, 1 g at wound closure on second hip) were used. Preoperative autologous blood donation was not used. For deep vein thrombosis prophylaxis, patients were treated with bilateral sequential compression devices while hospitalized, but chemoprophylaxis was different between groups. Patients in the DA group received prophylactic low-molecular-weight heparin for 10 days, followed by twice-daily aspirin (325 mg) for 4 weeks. Patients in the posterior group received warfarin (goal international normalized ratio, 1.7-2.2) for 3 weeks, followed by twice-daily aspirin (325 mg) for 3 weeks. The decision to transfuse allogenic red blood cells was made by the treating surgeon, based on standardized hospital protocols, wherein patients are transfused for hemoglobin levels under 7.0 g/dL, or for hemoglobin levels less than 8.0 g/dL in the presence of persistent symptoms. All patients received care on an orthopedic specialty floor and were assisted by the same physical therapists. Discharge disposition was coordinated with the same group of social workers.

Two to 3 months after surgery, patients returned for routine examination and radiographs. All patients were followed up for at least 90 days.

Statistical Analysis

All outcomes were analyzed with appropriate summary statistics. Chi-square tests or logistic regression analyses (for categorical outcomes) were used to compare baseline covariates with perioperative outcomes, and 2-sample tests or Wilcoxon rank-sum tests were used to compare outcomes measured on a continuous scale. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated as appropriate. Operative time was calculated by adding time from incision to wound closure for both hips (room turnover time between hips was not included). Anesthesia time was defined as total time patients were in the operating room. All statistical tests were 2-sided, and the threshold for statistical significance was set at α = 0.05.

Results

Compared with patients who underwent simultaneous bilateral THAs through the posterior approach, patients who underwent simultaneous bilateral THAs through the DA approach had longer mean operative times (153 vs 106 min; P < .001) and anesthesia times (257 vs 221 min; P = .007). The 2 groups’ hospital stays were similar in length (3.1 vs 3.5 days; P = .31), but patients in the DA group were more likely to be discharged home (100.0% vs 71.4%; P = .02) (Table 2).

Patients in the DA group were more likely to have sufficient intraoperative blood salvage for autologous transfusion (89.5% vs 57.1%; OR, 6.4; 95% CI, 1.16-34.94; P = .03) (Table 3) and received more mean units of salvaged autologous blood (1.4 vs 0.5; P = .003) (Table 2). Allogenic blood was not given to any patients in the DA group, but 3 patients in the posterior group (14.3%) required allogenic blood transfusion (P = .23) (Table 2). Salvaged autologous and allogenic blood transfusion was not associated with sex, age 60 years or older, or hospital LOS of 4 days or more (Table 3). The groups’ mean hemoglobin levels, measured the morning of postoperative day 1, were similar: 10.6 g/dL (range, 8.5-12.4 g/dL) for the DA group and 10.3 g/dL (range 8.6-12.3 g/dL) for the posterior group (Table 2).

In-hospital complications were uncommon in both groups (5% vs 14%; P = .61) (Table 2). One patient in the posterior group sustained a unilateral dislocation the day of surgery, and closed reduction was required; other complications (1 ileus, 2 tachyarrhythmias) did not require intervention. Ninety-day complications were also rare; 1 patient in the posterior group developed a hematoma with wound drainage, and this was successfully managed conservatively. There were no reoperations or readmissions in either group (Table 2).

Discussion

Although bilateral procedures account for less than 1% of THAs in the United States,¹¹ debate about their role in patients with severe bilateral hip disease continues. The potential benefits of a single episode of care must be weighed against the slightly increased risk for systemic complications.^7,10-15 Recent innovations in perioperative management have been shown to minimize complications,¹⁵ but it is unclear whether surgical approach affects perioperative outcomes. Our goals in this study were to evaluate operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach.

Patients in our DA group had longer operative and anesthesia times. Other studies have found longer operative times for the DA approach relative to the posterior approach in unilateral THAs.¹⁸ One potential benefit of the DA approach in the setting of simultaneous bilateral THAs is the ability to prepare and drape both sides before surgery and thereby keep the interruption between hips to a minimum. In the present study, however, time saved during turnover between hips was overshadowed by the time added for each THA.

Although it was uncommon for complications to occur within 90 days after surgery in this study, many patients are needed to fully investigate these rare occurrences. Because of inherent selection bias, these risks are difficult to directly compare in patients who undergo unilateral procedures. Although small studies have failed to clarify the issue,^7,19,20 a recent review of the almost 20,000 bilateral THA cases in the US Nationwide Inpatient Sample database found that bilateral (vs unilateral) THAs were associated with increased risk of local and systemic complications.¹¹ Therefore, bilateral THAs should be reserved for select cases, with attention given to excluding patients with preexisting cardiopulmonary disease and providing appropriate preoperative counseling.

Most studies have reported a higher transfusion rate in bilateral THAs relative to staged procedures.^7,21-23 Allogenic blood transfusion leads to immune suppression, coagulopathy, and other systemic effects in general, and has been specifically associated with infection in patients who undergo total joint arthroplasty.^24-29 Parvizi and colleagues¹⁷ reported reduced blood loss and fewer blood transfusions in patients who had simultaneous bilateral THAs through the DA approach, compared with the direct lateral approach. Patients in our DA group received more salvaged autologous blood, which we suppose was a function of longer operative times. However, postoperative hemoglobin levels and allogenic blood transfusion rates were statistically similar between the 2 groups. It is important to consider the increased risk of required allogenic blood transfusion associated with simultaneous bilateral THAs, but it is not fully clear if this risk is lower in THAs performed through the DA approach relative to other approaches. In our experience, the required transfusion risk is limited in DA and posterior approaches with use of contemporary perioperative blood management strategies.

Although hospital LOS is longer with simultaneous bilateral THAs than with unilateral THAs, historically it is shorter than the combined LOS of staged bilateral THAs.²⁰ Patients in our study had a relatively short LOS after bilateral THAs, and there was no difference in LOS between groups. However, patients were more likely to be discharged home after bilateral THAs through the DA approach vs the posterior approach. Although discharge location was not affected by age, sex, ASA score, or LOS, unrecognized social factors unrelated to surgical approach likely influenced this finding.

This study should be interpreted in light of important limitations. Foremost, although data were prospectively collected, we examined them retrospectively. Thus, it is possible there may be unaccounted for differences between our DA and posterior THA groups. For example, the DA and posterior approaches were used by different surgeons with differing experience, technique, and preferences, all of which could have affected outcomes. Furthermore, our sample was relatively small (simultaneous bilateral THAs are performed relatively infrequently). Last, although anesthesia, pain management, blood conservation, and physical therapy were similar for the 2 groups, there was no standardized protocol for determining eligibility for simultaneous bilateral THAs.

In conclusion, we found that simultaneous bilateral THAs can be safely performed through either the DA approach or the posterior approach. Although the transition between hips is shorter with the DA approach, this time savings is overshadowed by the increased duration of each procedure. Transfusion rates are low in both groups, and in-hospital and 90-day complications are quite rare. Furthermore, patients can routinely be discharged home without elevating readmission rates. We will continue to perform simultaneous bilateral THAs through the DA approach or the posterior approach, according to surgeon preference.

Am J Orthop. 2016;45(6):E373-E378. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

End-stage osteoarthritis of the hip is a debilitating disease that is reliably treated with total hip arthroplasty (THA).¹ Up to 35% of patients who undergo THA eventually require contralateral THA.^2,3 In patients who present with advanced bilateral disease and undergo unilateral THA, the risk of ultimately requiring a contralateral procedure is as high as 97%.^3-6 In patients with bilateral hip disease, function is not fully optimized until both hips have been replaced, particularly in the setting of fixed flexion contractures.^7-9 Naturally, there has been some interest in simultaneous bilateral THAs for select patients.

The potential benefits of bilateral THAs over staged procedures include faster overall rehabilitation, exposure to a single anesthetic, reduced hospital length of stay (LOS), and cost savings.^10-12 However, opinion on recommending bilateral THAs is mixed. Although bilateral procedures historically have been fraught with perioperative complications,^13,14 advances in surgical and anesthetic techniques have led to improved outcomes.¹⁵ Whether surgical approach is a factor in these outcomes is unclear.

The popularity of the direct anterior (DA) approach for THA has increased in recent years.¹⁶ Although the relative advantages of various approaches remain in debate, one potential benefit of the DA approach is supine positioning, which allows simultaneous bilateral THAs to be performed without the need for repositioning before proceeding with the contralateral side. However, simultaneous bilateral THAs performed through the DA approach and those performed through other surgical approaches are lacking in comparative outcomes data.¹⁷In this study, we evaluated operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who had simultaneous bilateral THAs through either the DA approach or the posterior approach.

Methods

Study Design

This single-center study was conducted at the Mayo Clinic in Rochester, Minnesota. After obtaining approval from our Institutional Review Board, we performed a retrospective cohort analysis. We used our institution’s total joint registry to identify all patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach. The first bilateral THAs to use the DA approach at our institution were performed in 2012. To ensure that the DA and posterior groups’ perioperative management would be similar, we included only cases performed between 2012 and 2014.

There were 19 patients in the DA group and 21 in the posterior group. The groups were similar in mean age (54 vs 54 years; P = .90), sex (73% vs 57% males; P = .33), body mass index (BMI; 25 vs 28 kg/m²; P = .38), preoperative hemoglobin level (14.3 vs 14.0 g/dL; P = .37), preoperative diagnosis (71.1% vs 78.6% degenerative joint disease; P = .75), and American Society of Anesthesiologists (ASA) score (1.9 vs 2.0; P = .63) (Table 1).

Patient Care

All cases were performed by 1 of 3 dedicated arthroplasty surgeons (Dr. Taunton, Dr. Sierra, Dr. Trousdale). Dr. Taunton exclusively uses the DA approach, and Dr. Sierra and Dr. Trousdale exclusively use the posterior approach. Patients in both groups received preoperative medical clearance and attended the same preoperative education class.

Patients in the DA group were positioned supine on an orthopedic table that allows hyperextension and adduction of the operative leg. Both hips were prepared and draped simultaneously. The most symptomatic hip was operated on first, with a sterile drape covering the contralateral hip. Between hips, fluoroscopy was moved to the other side of the operative suite, but no changes in positioning or preparation were necessary. A deep drain was placed on each side, and then was removed the morning of postoperative day 1. The same set of instruments was used on both sides.

Patients in the posterior group were positioned lateral on a regular operative table with hip rests. The most symptomatic hip was operated on first. After wound closure and dressing application, the patient was flipped to allow access to the contralateral hip and was prepared and draped again. The same instruments were used on each side. Drains were not used.

All patients received the same comprehensive multimodal pain management, which combined general and epidural anesthesia (remaining in place until postoperative day 2) and included an oral pain regimen of scheduled acetaminophen and as-needed tramadol and oxycodone. In all cases, intraoperative blood salvage and intravenous tranexamic acid (1 g at time of incision on first hip, 1 g at wound closure on second hip) were used. Preoperative autologous blood donation was not used. For deep vein thrombosis prophylaxis, patients were treated with bilateral sequential compression devices while hospitalized, but chemoprophylaxis was different between groups. Patients in the DA group received prophylactic low-molecular-weight heparin for 10 days, followed by twice-daily aspirin (325 mg) for 4 weeks. Patients in the posterior group received warfarin (goal international normalized ratio, 1.7-2.2) for 3 weeks, followed by twice-daily aspirin (325 mg) for 3 weeks. The decision to transfuse allogenic red blood cells was made by the treating surgeon, based on standardized hospital protocols, wherein patients are transfused for hemoglobin levels under 7.0 g/dL, or for hemoglobin levels less than 8.0 g/dL in the presence of persistent symptoms. All patients received care on an orthopedic specialty floor and were assisted by the same physical therapists. Discharge disposition was coordinated with the same group of social workers.

Two to 3 months after surgery, patients returned for routine examination and radiographs. All patients were followed up for at least 90 days.

Statistical Analysis

All outcomes were analyzed with appropriate summary statistics. Chi-square tests or logistic regression analyses (for categorical outcomes) were used to compare baseline covariates with perioperative outcomes, and 2-sample tests or Wilcoxon rank-sum tests were used to compare outcomes measured on a continuous scale. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated as appropriate. Operative time was calculated by adding time from incision to wound closure for both hips (room turnover time between hips was not included). Anesthesia time was defined as total time patients were in the operating room. All statistical tests were 2-sided, and the threshold for statistical significance was set at α = 0.05.

Results

Compared with patients who underwent simultaneous bilateral THAs through the posterior approach, patients who underwent simultaneous bilateral THAs through the DA approach had longer mean operative times (153 vs 106 min; P < .001) and anesthesia times (257 vs 221 min; P = .007). The 2 groups’ hospital stays were similar in length (3.1 vs 3.5 days; P = .31), but patients in the DA group were more likely to be discharged home (100.0% vs 71.4%; P = .02) (Table 2).

Patients in the DA group were more likely to have sufficient intraoperative blood salvage for autologous transfusion (89.5% vs 57.1%; OR, 6.4; 95% CI, 1.16-34.94; P = .03) (Table 3) and received more mean units of salvaged autologous blood (1.4 vs 0.5; P = .003) (Table 2). Allogenic blood was not given to any patients in the DA group, but 3 patients in the posterior group (14.3%) required allogenic blood transfusion (P = .23) (Table 2). Salvaged autologous and allogenic blood transfusion was not associated with sex, age 60 years or older, or hospital LOS of 4 days or more (Table 3). The groups’ mean hemoglobin levels, measured the morning of postoperative day 1, were similar: 10.6 g/dL (range, 8.5-12.4 g/dL) for the DA group and 10.3 g/dL (range 8.6-12.3 g/dL) for the posterior group (Table 2).

In-hospital complications were uncommon in both groups (5% vs 14%; P = .61) (Table 2). One patient in the posterior group sustained a unilateral dislocation the day of surgery, and closed reduction was required; other complications (1 ileus, 2 tachyarrhythmias) did not require intervention. Ninety-day complications were also rare; 1 patient in the posterior group developed a hematoma with wound drainage, and this was successfully managed conservatively. There were no reoperations or readmissions in either group (Table 2).

Discussion

Although bilateral procedures account for less than 1% of THAs in the United States,¹¹ debate about their role in patients with severe bilateral hip disease continues. The potential benefits of a single episode of care must be weighed against the slightly increased risk for systemic complications.^7,10-15 Recent innovations in perioperative management have been shown to minimize complications,¹⁵ but it is unclear whether surgical approach affects perioperative outcomes. Our goals in this study were to evaluate operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach.

Patients in our DA group had longer operative and anesthesia times. Other studies have found longer operative times for the DA approach relative to the posterior approach in unilateral THAs.¹⁸ One potential benefit of the DA approach in the setting of simultaneous bilateral THAs is the ability to prepare and drape both sides before surgery and thereby keep the interruption between hips to a minimum. In the present study, however, time saved during turnover between hips was overshadowed by the time added for each THA.

Although it was uncommon for complications to occur within 90 days after surgery in this study, many patients are needed to fully investigate these rare occurrences. Because of inherent selection bias, these risks are difficult to directly compare in patients who undergo unilateral procedures. Although small studies have failed to clarify the issue,^7,19,20 a recent review of the almost 20,000 bilateral THA cases in the US Nationwide Inpatient Sample database found that bilateral (vs unilateral) THAs were associated with increased risk of local and systemic complications.¹¹ Therefore, bilateral THAs should be reserved for select cases, with attention given to excluding patients with preexisting cardiopulmonary disease and providing appropriate preoperative counseling.

Most studies have reported a higher transfusion rate in bilateral THAs relative to staged procedures.^7,21-23 Allogenic blood transfusion leads to immune suppression, coagulopathy, and other systemic effects in general, and has been specifically associated with infection in patients who undergo total joint arthroplasty.^24-29 Parvizi and colleagues¹⁷ reported reduced blood loss and fewer blood transfusions in patients who had simultaneous bilateral THAs through the DA approach, compared with the direct lateral approach. Patients in our DA group received more salvaged autologous blood, which we suppose was a function of longer operative times. However, postoperative hemoglobin levels and allogenic blood transfusion rates were statistically similar between the 2 groups. It is important to consider the increased risk of required allogenic blood transfusion associated with simultaneous bilateral THAs, but it is not fully clear if this risk is lower in THAs performed through the DA approach relative to other approaches. In our experience, the required transfusion risk is limited in DA and posterior approaches with use of contemporary perioperative blood management strategies.

Although hospital LOS is longer with simultaneous bilateral THAs than with unilateral THAs, historically it is shorter than the combined LOS of staged bilateral THAs.²⁰ Patients in our study had a relatively short LOS after bilateral THAs, and there was no difference in LOS between groups. However, patients were more likely to be discharged home after bilateral THAs through the DA approach vs the posterior approach. Although discharge location was not affected by age, sex, ASA score, or LOS, unrecognized social factors unrelated to surgical approach likely influenced this finding.

This study should be interpreted in light of important limitations. Foremost, although data were prospectively collected, we examined them retrospectively. Thus, it is possible there may be unaccounted for differences between our DA and posterior THA groups. For example, the DA and posterior approaches were used by different surgeons with differing experience, technique, and preferences, all of which could have affected outcomes. Furthermore, our sample was relatively small (simultaneous bilateral THAs are performed relatively infrequently). Last, although anesthesia, pain management, blood conservation, and physical therapy were similar for the 2 groups, there was no standardized protocol for determining eligibility for simultaneous bilateral THAs.

In conclusion, we found that simultaneous bilateral THAs can be safely performed through either the DA approach or the posterior approach. Although the transition between hips is shorter with the DA approach, this time savings is overshadowed by the increased duration of each procedure. Transfusion rates are low in both groups, and in-hospital and 90-day complications are quite rare. Furthermore, patients can routinely be discharged home without elevating readmission rates. We will continue to perform simultaneous bilateral THAs through the DA approach or the posterior approach, according to surgeon preference.

Am J Orthop. 2016;45(6):E373-E378. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

End-stage osteoarthritis of the hip is a debilitating disease that is reliably treated with total hip arthroplasty (THA).¹ Up to 35% of patients who undergo THA eventually require contralateral THA.^2,3 In patients who present with advanced bilateral disease and undergo unilateral THA, the risk of ultimately requiring a contralateral procedure is as high as 97%.^3-6 In patients with bilateral hip disease, function is not fully optimized until both hips have been replaced, particularly in the setting of fixed flexion contractures.^7-9 Naturally, there has been some interest in simultaneous bilateral THAs for select patients.

The potential benefits of bilateral THAs over staged procedures include faster overall rehabilitation, exposure to a single anesthetic, reduced hospital length of stay (LOS), and cost savings.^10-12 However, opinion on recommending bilateral THAs is mixed. Although bilateral procedures historically have been fraught with perioperative complications,^13,14 advances in surgical and anesthetic techniques have led to improved outcomes.¹⁵ Whether surgical approach is a factor in these outcomes is unclear.

The popularity of the direct anterior (DA) approach for THA has increased in recent years.¹⁶ Although the relative advantages of various approaches remain in debate, one potential benefit of the DA approach is supine positioning, which allows simultaneous bilateral THAs to be performed without the need for repositioning before proceeding with the contralateral side. However, simultaneous bilateral THAs performed through the DA approach and those performed through other surgical approaches are lacking in comparative outcomes data.¹⁷In this study, we evaluated operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who had simultaneous bilateral THAs through either the DA approach or the posterior approach.

Methods

Study Design

This single-center study was conducted at the Mayo Clinic in Rochester, Minnesota. After obtaining approval from our Institutional Review Board, we performed a retrospective cohort analysis. We used our institution’s total joint registry to identify all patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach. The first bilateral THAs to use the DA approach at our institution were performed in 2012. To ensure that the DA and posterior groups’ perioperative management would be similar, we included only cases performed between 2012 and 2014.

There were 19 patients in the DA group and 21 in the posterior group. The groups were similar in mean age (54 vs 54 years; P = .90), sex (73% vs 57% males; P = .33), body mass index (BMI; 25 vs 28 kg/m²; P = .38), preoperative hemoglobin level (14.3 vs 14.0 g/dL; P = .37), preoperative diagnosis (71.1% vs 78.6% degenerative joint disease; P = .75), and American Society of Anesthesiologists (ASA) score (1.9 vs 2.0; P = .63) (Table 1).

Patient Care

All cases were performed by 1 of 3 dedicated arthroplasty surgeons (Dr. Taunton, Dr. Sierra, Dr. Trousdale). Dr. Taunton exclusively uses the DA approach, and Dr. Sierra and Dr. Trousdale exclusively use the posterior approach. Patients in both groups received preoperative medical clearance and attended the same preoperative education class.

Patients in the DA group were positioned supine on an orthopedic table that allows hyperextension and adduction of the operative leg. Both hips were prepared and draped simultaneously. The most symptomatic hip was operated on first, with a sterile drape covering the contralateral hip. Between hips, fluoroscopy was moved to the other side of the operative suite, but no changes in positioning or preparation were necessary. A deep drain was placed on each side, and then was removed the morning of postoperative day 1. The same set of instruments was used on both sides.

Patients in the posterior group were positioned lateral on a regular operative table with hip rests. The most symptomatic hip was operated on first. After wound closure and dressing application, the patient was flipped to allow access to the contralateral hip and was prepared and draped again. The same instruments were used on each side. Drains were not used.

All patients received the same comprehensive multimodal pain management, which combined general and epidural anesthesia (remaining in place until postoperative day 2) and included an oral pain regimen of scheduled acetaminophen and as-needed tramadol and oxycodone. In all cases, intraoperative blood salvage and intravenous tranexamic acid (1 g at time of incision on first hip, 1 g at wound closure on second hip) were used. Preoperative autologous blood donation was not used. For deep vein thrombosis prophylaxis, patients were treated with bilateral sequential compression devices while hospitalized, but chemoprophylaxis was different between groups. Patients in the DA group received prophylactic low-molecular-weight heparin for 10 days, followed by twice-daily aspirin (325 mg) for 4 weeks. Patients in the posterior group received warfarin (goal international normalized ratio, 1.7-2.2) for 3 weeks, followed by twice-daily aspirin (325 mg) for 3 weeks. The decision to transfuse allogenic red blood cells was made by the treating surgeon, based on standardized hospital protocols, wherein patients are transfused for hemoglobin levels under 7.0 g/dL, or for hemoglobin levels less than 8.0 g/dL in the presence of persistent symptoms. All patients received care on an orthopedic specialty floor and were assisted by the same physical therapists. Discharge disposition was coordinated with the same group of social workers.

Two to 3 months after surgery, patients returned for routine examination and radiographs. All patients were followed up for at least 90 days.

Statistical Analysis

All outcomes were analyzed with appropriate summary statistics. Chi-square tests or logistic regression analyses (for categorical outcomes) were used to compare baseline covariates with perioperative outcomes, and 2-sample tests or Wilcoxon rank-sum tests were used to compare outcomes measured on a continuous scale. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated as appropriate. Operative time was calculated by adding time from incision to wound closure for both hips (room turnover time between hips was not included). Anesthesia time was defined as total time patients were in the operating room. All statistical tests were 2-sided, and the threshold for statistical significance was set at α = 0.05.

Results

Compared with patients who underwent simultaneous bilateral THAs through the posterior approach, patients who underwent simultaneous bilateral THAs through the DA approach had longer mean operative times (153 vs 106 min; P < .001) and anesthesia times (257 vs 221 min; P = .007). The 2 groups’ hospital stays were similar in length (3.1 vs 3.5 days; P = .31), but patients in the DA group were more likely to be discharged home (100.0% vs 71.4%; P = .02) (Table 2).

Patients in the DA group were more likely to have sufficient intraoperative blood salvage for autologous transfusion (89.5% vs 57.1%; OR, 6.4; 95% CI, 1.16-34.94; P = .03) (Table 3) and received more mean units of salvaged autologous blood (1.4 vs 0.5; P = .003) (Table 2). Allogenic blood was not given to any patients in the DA group, but 3 patients in the posterior group (14.3%) required allogenic blood transfusion (P = .23) (Table 2). Salvaged autologous and allogenic blood transfusion was not associated with sex, age 60 years or older, or hospital LOS of 4 days or more (Table 3). The groups’ mean hemoglobin levels, measured the morning of postoperative day 1, were similar: 10.6 g/dL (range, 8.5-12.4 g/dL) for the DA group and 10.3 g/dL (range 8.6-12.3 g/dL) for the posterior group (Table 2).

In-hospital complications were uncommon in both groups (5% vs 14%; P = .61) (Table 2). One patient in the posterior group sustained a unilateral dislocation the day of surgery, and closed reduction was required; other complications (1 ileus, 2 tachyarrhythmias) did not require intervention. Ninety-day complications were also rare; 1 patient in the posterior group developed a hematoma with wound drainage, and this was successfully managed conservatively. There were no reoperations or readmissions in either group (Table 2).

Discussion

Although bilateral procedures account for less than 1% of THAs in the United States,¹¹ debate about their role in patients with severe bilateral hip disease continues. The potential benefits of a single episode of care must be weighed against the slightly increased risk for systemic complications.^7,10-15 Recent innovations in perioperative management have been shown to minimize complications,¹⁵ but it is unclear whether surgical approach affects perioperative outcomes. Our goals in this study were to evaluate operative times, transfusion requirements, hospital discharge data, and 90-day complication rates in patients who underwent simultaneous bilateral THAs through either the DA approach or the posterior approach.

Patients in our DA group had longer operative and anesthesia times. Other studies have found longer operative times for the DA approach relative to the posterior approach in unilateral THAs.¹⁸ One potential benefit of the DA approach in the setting of simultaneous bilateral THAs is the ability to prepare and drape both sides before surgery and thereby keep the interruption between hips to a minimum. In the present study, however, time saved during turnover between hips was overshadowed by the time added for each THA.

Although it was uncommon for complications to occur within 90 days after surgery in this study, many patients are needed to fully investigate these rare occurrences. Because of inherent selection bias, these risks are difficult to directly compare in patients who undergo unilateral procedures. Although small studies have failed to clarify the issue,^7,19,20 a recent review of the almost 20,000 bilateral THA cases in the US Nationwide Inpatient Sample database found that bilateral (vs unilateral) THAs were associated with increased risk of local and systemic complications.¹¹ Therefore, bilateral THAs should be reserved for select cases, with attention given to excluding patients with preexisting cardiopulmonary disease and providing appropriate preoperative counseling.

Most studies have reported a higher transfusion rate in bilateral THAs relative to staged procedures.^7,21-23 Allogenic blood transfusion leads to immune suppression, coagulopathy, and other systemic effects in general, and has been specifically associated with infection in patients who undergo total joint arthroplasty.^24-29 Parvizi and colleagues¹⁷ reported reduced blood loss and fewer blood transfusions in patients who had simultaneous bilateral THAs through the DA approach, compared with the direct lateral approach. Patients in our DA group received more salvaged autologous blood, which we suppose was a function of longer operative times. However, postoperative hemoglobin levels and allogenic blood transfusion rates were statistically similar between the 2 groups. It is important to consider the increased risk of required allogenic blood transfusion associated with simultaneous bilateral THAs, but it is not fully clear if this risk is lower in THAs performed through the DA approach relative to other approaches. In our experience, the required transfusion risk is limited in DA and posterior approaches with use of contemporary perioperative blood management strategies.

Although hospital LOS is longer with simultaneous bilateral THAs than with unilateral THAs, historically it is shorter than the combined LOS of staged bilateral THAs.²⁰ Patients in our study had a relatively short LOS after bilateral THAs, and there was no difference in LOS between groups. However, patients were more likely to be discharged home after bilateral THAs through the DA approach vs the posterior approach. Although discharge location was not affected by age, sex, ASA score, or LOS, unrecognized social factors unrelated to surgical approach likely influenced this finding.

This study should be interpreted in light of important limitations. Foremost, although data were prospectively collected, we examined them retrospectively. Thus, it is possible there may be unaccounted for differences between our DA and posterior THA groups. For example, the DA and posterior approaches were used by different surgeons with differing experience, technique, and preferences, all of which could have affected outcomes. Furthermore, our sample was relatively small (simultaneous bilateral THAs are performed relatively infrequently). Last, although anesthesia, pain management, blood conservation, and physical therapy were similar for the 2 groups, there was no standardized protocol for determining eligibility for simultaneous bilateral THAs.

In conclusion, we found that simultaneous bilateral THAs can be safely performed through either the DA approach or the posterior approach. Although the transition between hips is shorter with the DA approach, this time savings is overshadowed by the increased duration of each procedure. Transfusion rates are low in both groups, and in-hospital and 90-day complications are quite rare. Furthermore, patients can routinely be discharged home without elevating readmission rates. We will continue to perform simultaneous bilateral THAs through the DA approach or the posterior approach, according to surgeon preference.

Am J Orthop. 2016;45(6):E373-E378. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

Aneurysmal bone cysts (ABC) are expansile, hemorrhagic, non-neoplastic lesions that can be locally destructive¹ and that can arise either de novo or secondary to another benign or malignant lesion.² Although primary and secondary ABCs typically are benign, there are cases of malignant degeneration of primary ABCs, though the transformation arises almost exclusively in the context of prior radiation exposure.^3-5 Malignant change without history of irradiation is rare; only 6 such cases have been reported.^5-10 In 4 of these cases, the transformation was to osteosarcoma.^5,8-10

Here we report on an ABC that degenerated into a fibroblastic osteosarcoma—the fifth such case in the medical literature. In addition to reviewing the earlier cases, we describe the radiologic and histologic underpinnings of this diagnosis and the insight that they provide into the pathogenesis of this rare process. Although the prevailing view is that ABCs are benign, it is important to know these lesions have the potential to undergo malignant transformation, even in the absence of prior radiation exposure. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A healthy and previously asymptomatic 37-year-old man presented with thigh pain after a minor fall onto a couch. Radiographs showed a diaphyseal femoral pathologic fracture adjacent to a small but benign-appearing cystic lesion (Figures 1A, 1B).

Two years later, the patient had a bicycle accident and, after 2 weeks of significantly increased thigh swelling, presented to the emergency department at the referring institution. Radiographs showed a lytic lesion in the femoral diaphysis that was highly suspicious for malignancy (Figures 3A, 3B).

Discussion

Aneurysmal bone cysts are expansile, hemorrhagic, locally destructive lesions that generally develop within the first 3 decades of life. Ever since they were first described by Jaffe and Lichtenstein¹¹ in 1942, the most widely accepted theory of their pathogenesis has been that they begin as a benign reactive vascular process.¹² However, more recent molecular studies by Oliveira and colleagues¹³ and Panoutsakopoulos and colleagues¹⁴ have demonstrated a clonal neoplastic basis for primary ABCs related to cytogenetic upregulation of oncogenes USP6 and CDH11 after translocation of 17p13 and 16q22.

Given the clonal nature of these lesions, it is surprising that malignant transformation is so rare. Until now, there have been only 4 reports of an ABC undergoing malignant degeneration to osteosarcoma without prior radiation exposure.

Aneurysmal bone cysts (ABC) are expansile, hemorrhagic, non-neoplastic lesions that can be locally destructive¹ and that can arise either de novo or secondary to another benign or malignant lesion.² Although primary and secondary ABCs typically are benign, there are cases of malignant degeneration of primary ABCs, though the transformation arises almost exclusively in the context of prior radiation exposure.^3-5 Malignant change without history of irradiation is rare; only 6 such cases have been reported.^5-10 In 4 of these cases, the transformation was to osteosarcoma.^5,8-10

Here we report on an ABC that degenerated into a fibroblastic osteosarcoma—the fifth such case in the medical literature. In addition to reviewing the earlier cases, we describe the radiologic and histologic underpinnings of this diagnosis and the insight that they provide into the pathogenesis of this rare process. Although the prevailing view is that ABCs are benign, it is important to know these lesions have the potential to undergo malignant transformation, even in the absence of prior radiation exposure. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A healthy and previously asymptomatic 37-year-old man presented with thigh pain after a minor fall onto a couch. Radiographs showed a diaphyseal femoral pathologic fracture adjacent to a small but benign-appearing cystic lesion (Figures 1A, 1B).

Two years later, the patient had a bicycle accident and, after 2 weeks of significantly increased thigh swelling, presented to the emergency department at the referring institution. Radiographs showed a lytic lesion in the femoral diaphysis that was highly suspicious for malignancy (Figures 3A, 3B).

Discussion

Aneurysmal bone cysts are expansile, hemorrhagic, locally destructive lesions that generally develop within the first 3 decades of life. Ever since they were first described by Jaffe and Lichtenstein¹¹ in 1942, the most widely accepted theory of their pathogenesis has been that they begin as a benign reactive vascular process.¹² However, more recent molecular studies by Oliveira and colleagues¹³ and Panoutsakopoulos and colleagues¹⁴ have demonstrated a clonal neoplastic basis for primary ABCs related to cytogenetic upregulation of oncogenes USP6 and CDH11 after translocation of 17p13 and 16q22.

Given the clonal nature of these lesions, it is surprising that malignant transformation is so rare. Until now, there have been only 4 reports of an ABC undergoing malignant degeneration to osteosarcoma without prior radiation exposure.

Aneurysmal bone cysts (ABC) are expansile, hemorrhagic, non-neoplastic lesions that can be locally destructive¹ and that can arise either de novo or secondary to another benign or malignant lesion.² Although primary and secondary ABCs typically are benign, there are cases of malignant degeneration of primary ABCs, though the transformation arises almost exclusively in the context of prior radiation exposure.^3-5 Malignant change without history of irradiation is rare; only 6 such cases have been reported.^5-10 In 4 of these cases, the transformation was to osteosarcoma.^5,8-10

Here we report on an ABC that degenerated into a fibroblastic osteosarcoma—the fifth such case in the medical literature. In addition to reviewing the earlier cases, we describe the radiologic and histologic underpinnings of this diagnosis and the insight that they provide into the pathogenesis of this rare process. Although the prevailing view is that ABCs are benign, it is important to know these lesions have the potential to undergo malignant transformation, even in the absence of prior radiation exposure. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A healthy and previously asymptomatic 37-year-old man presented with thigh pain after a minor fall onto a couch. Radiographs showed a diaphyseal femoral pathologic fracture adjacent to a small but benign-appearing cystic lesion (Figures 1A, 1B).

Two years later, the patient had a bicycle accident and, after 2 weeks of significantly increased thigh swelling, presented to the emergency department at the referring institution. Radiographs showed a lytic lesion in the femoral diaphysis that was highly suspicious for malignancy (Figures 3A, 3B).

Discussion

Aneurysmal bone cysts are expansile, hemorrhagic, locally destructive lesions that generally develop within the first 3 decades of life. Ever since they were first described by Jaffe and Lichtenstein¹¹ in 1942, the most widely accepted theory of their pathogenesis has been that they begin as a benign reactive vascular process.¹² However, more recent molecular studies by Oliveira and colleagues¹³ and Panoutsakopoulos and colleagues¹⁴ have demonstrated a clonal neoplastic basis for primary ABCs related to cytogenetic upregulation of oncogenes USP6 and CDH11 after translocation of 17p13 and 16q22.

Given the clonal nature of these lesions, it is surprising that malignant transformation is so rare. Until now, there have been only 4 reports of an ABC undergoing malignant degeneration to osteosarcoma without prior radiation exposure.

An increasingly number of patients with symptomatic isolated medial unicompartmental knee osteoarthritis (OA) are too young and too functionally active to be ideal candidates for total knee arthroplasty (TKA). Isolated medial compartment OA occurs in 10% to 29.5% of all cases, whereas the isolated lateral variant is less common, with a reported incidence of 1% to 7%.^1,2 In 1961, Jackson and Waugh³ introduced the high tibial osteotomy (HTO) as a surgical treatment for single-compartment OA. This procedure is designed to increase the life span of articular cartilage by unloading and redistributing the mechanical forces over the nonaffected compartment. Unicompartmental knee arthroplasty (UKA) was introduced in the 1970s as an alternative to TKA or HTO for single-compartment OA.

Since the introduction of these methods, there has been debate about which patients are appropriate candidates for each procedure. Improved surgical techniques and implant designs have led surgeons to reexamine the selection criteria and contraindications for these procedures. Furthermore, given the increasing popularity and use of UKA, the question arises as to whether HTO still has a role in clinical practice in the surgical treatment of medial OA of the knee.

To clarify current ambiguities, we review the modern indications, subjective outcome scores, and survivorship results of UKA and HTO in the treatment of isolated medial compartment degeneration of the knee. In addition, in a thorough review of the literature, we evaluate global trends in the use of both methods.

High Tibial Osteotomy for Medial Compartment OA

Indications

Before the introduction of TKA and UKA for single-compartment OA, surgical management consisted of HTO. When the mechanical axis is slightly overcorrected, the medial compartment is decompressed, ensuring tissue viability and delaying progressive compartment degeneration.

Traditionally, HTO is indicated for young (age <60 years), normal-weight, active patients with radiographic single-compartment OA.⁶ The knee should be stable and have good range of motion (ROM; flexion >120°), and pain should be localized to the tibiofemoral joint line.

Over the past few decades, numerous authors have reported similar inclusion criteria, clarifying their definition. This definition should be further refined in order to optimize survivorship and clinical outcomes.

Confirming age as an inclusion criterion for HTO, Trieb and colleagues⁷ found that the risk of failure was significantly (P = .046) higher for HTO patients older than 65 years than for those younger than 65 years (relative risk, 1.5). This finding agrees with findings of other studies, which suggests that, in particular, young patients benefit from HTO.^8-11

Moreover, there is a clear relation between HTO survival and obesity. In a study of 159 CWHTOs, Akizuki and colleagues¹² reported that preoperative body mass index (BMI) higher than 27.5 kg/m² was a significant risk factor for early failure. Using BMI higher than 30 kg/m² as a threshold, Howells and colleagues⁹ found significantly inferior Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) results for the obese group 5 years after HTO.

Radiographic evidence of severe preoperative compartment degeneration has been associated with early conversion to TKA. Flecher and colleagues¹¹ and van Raaij and colleagues¹³ both concluded the best long-term survival grades are achieved in HTO patients with mild compartment OA (Ahlbäck^14 grade I). The question then becomes whether these patients should be treated nonoperatively instead.^15,16The literature supports strict adherence to inclusion criteria in the selection of a potential HTO candidate. Age, BMI, and the preoperative state of OA should be taken into account in order to optimize clinical outcome and survivorship results in patients about to undergo HTO.

Outcomes

Multiple authors have described or compared the midterm or long-term results of the various surgical HTO techniques. Howells and colleagues⁹ noted overall survival rates of 87% (5 years after CWHTO) and 79% (10 years after CWHTO). Over the 10-year postoperative period, there was significant deterioration in clinical outcome scores and survivorship. Others authors have had similar findings.^17-19 van Raaij and colleagues¹³ found that the 10-year probability of survival after CWHTO was 75%. In 455 patients who underwent lateral CWHTO, Hui and colleagues⁸ found that 5-year probability of survival was 95%, 10-year probability was 79%, and 15-year probability was 56%. Niinimäki and colleagues¹⁰ used the Finnish Arthroplasty Register to report HTO survivorship at a national level. Using conversion to TKA as a cutoff, they noted 5-year survivorship of 89% and 10-year survivorship of 73%. To our knowledge, 2 groups, both in Japan, have reported substantially higher 15-year survival rates: 90%¹² and 93%.²⁰ The authors acknowledged that their results were significantly better than in other countries and that Japanese lifestyle, culture, and body habitus therefore require further investigation. At this time, it is not possible to compare their results with Western results.

In an attempt to compare the different survival rates of the various HTO techniques, Schallberger and colleagues²¹ conducted a retrospective study of OWHTOs and CWHTOs. At median follow-up of 16.5 years, comparative survival rates showed a trend of deterioration. Although data were limited, there were no significant differences in survival or functional outcome between the 2 techniques. In a recent randomized clinical trial, Duivenvoorden and colleagues⁵ compared these techniques’ midterm results (mean follow-up, 6 years). Clinical outcomes were not significantly different. There were more complications in the OWHTO group and more conversions to TKA in the CWHTO group. Considering these results, the authors suggested OWHTO without autologous bone graft is the best HTO treatment strategy for medial gonarthritis with varus malalignment of <12°.

The HTO results noted in these studies show a similar deteriorating trend; expected 10-year survivorship is 75%. Although modern implants and surgical techniques are being used, evidence supporting use of one surgical HTO method over another is lacking.

UKA for Medial Compartment OA

Indications

Since it was first introduced in the 1970s, use of UKA for single-compartment OA has been a subject of debate. The high failure rates reported at the time raised skepticism about the new treatment.²² Kozinn and Scott²³ defined classic indications and contraindications. Indications included isolated medial or lateral compartment OA or osteonecrosis of the knee, age over 60 years, and weight under 82 kg. In addition, the angular deformity of the affected lower extremity had to be <15° and passively correctable to neutral at time of surgery. Last, the flexion contracture had to be <5°, and ideal ROM was 90°. Contraindications included high activity, age under 60 years, and inflammatory arthritis. Strict adherence led to improved implant survival and lower revision rates. Because of improved surgical techniques, modern implant designs, and accumulating experience with the procedure, the surgical indications for UKA have expanded. Exact thresholds for UKA inclusion, however, remain unclear.

The modern literature is overturning the traditional idea that UKA is not indicated for patients under age 60 years.²³ Using KSS, Thompson and colleagues²⁴ found that younger patients did better than older patients 2 years after UKA using various types of implants. Analyzing survivorship results, Heyse and colleagues²⁵ concluded that UKA can be successful in patients under age 60 years and reported a 15-year survivorship rate of 85.6% and excellent outcome scores. Other authors have had similar findings.^26-28

Evaluating the influence of weight, Thompson and colleagues²⁴ found obese patients did not have a higher revision rate but did have slower progression of improvement 2 years after UKA. Cavaignac and colleagues²⁹ concluded that, at minimum follow-up of 7 years (range, 7-22 years), weight did not influence UKA survivorship. Other authors^30-33 have found no significant influence of BMI on survival.

Reports on preoperative radiographic parameters that can potentially influence UKA results are limited. In 113 medial UKAs studied by Niinimäki and colleagues,³⁴ mild medial compartment degeneration, seen on preoperative radiographs, was associated with significantly higher failure rates. The authors concluded that other treatment options should be favored in the absence of severe isolated compartment OA.

Although the classic indications defined by Kozinn and Scott²³ have yielded good to excellent UKA results, improvements in implants and surgical techniques^35-38 have extended the criteria. The modern literature demonstrates that age and BMI should not be used as criteria for excluding UKA candidates. Radiographically, there should be significant isolated compartment degeneration in order to optimize patient-reported outcome and survivorship.

Outcomes

Improved implant designs and modern minimally invasive techniques have effected a change in outcome results and a renewed interest in implants. Over the past decade, multiple authors have described the various modern UKA implants and their survivorship. Reports published since UKA was introduced in the 1970s show a continual increase in implant survival. Koskinen and colleagues,³⁹ using Finnish Arthroplasty Register data on 1819 UKAs performed between 1985 and 2003, found 10-year survival rates of 81% for Oxford implants (Zimmer Biomet), 79% for Miller-Galante II (Zimmer Biomet), 78% for Duracon (Howmedica), and 53% for PCA unicompartmental knee (Howmedica). Heyse and colleagues²⁵ reported 10- and 15-year survivorship data (93.5% and 86.3%, respectively) for 223 patients under age 60 years at the time of their index surgery (Genesis Unicondylar implant, Smith & Nephew), performed between 1993 and 2005. KSS was good to excellent. Similar numbers in cohorts under age 60 years were reported by Schai and colleagues²⁶ using the PFC system (Johnson & Johnson) and by Price and colleagues²⁷ using the medial Oxford UKA. Both groups reported excellent survivorship rates: 93% at 2- to 6-year follow-up and 91% at 10-year follow-up. The outcome in older patients seems satisfactory as well. In another multicenter report, by Price and colleagues,⁴⁰ medial Oxford UKAs had a 15-year survival rate of 93%. Berger and colleagues⁴¹ reported similar numbers for the Miller-Galante prosthesis. Survival rates were 98% (10 years) and 95.7% (13 years), and 92% of patients had good to excellent Hospital for Special Surgery knee scores.

Although various modern implants have had good to excellent results, the historical question of what type of UKA to use (mobile or fixed-bearing) remains unanswered. To try to address it, Peersman and colleagues⁴² performed a systematic review of 44 papers (9463 knees). The 2 implant types had comparable revision rates. Another recent retrospective study tried to determine what is crucial for implant survival: implant design or surgeon experience.⁴³ The authors concluded that prosthetic component positioning is key. Other authors have reported high-volume centers are crucial for satisfactory UKA results and lower revision rates.^44-46

Results of these studies indicate that, where UKAs are being performed in volume, 10-year survivorship rates higher than 90% and good to excellent outcomes can be expected.

UKA vs HTO

Cohort studies that have directly compared the 2 treatment modalities are scarce, and most have been retrospective. In a prospective study, Stukenborg-Colsman and colleagues⁴⁷ randomized patients with medial compartment OA to undergo either CWHTO (32 patients) with a technique reported by Coventry⁴⁸ or UKA (28 patients) with the unicondylar knee sliding prosthesis, Tübingen pattern (Aesculap), between 1988 and 1991. Patients were assessed 2.5, 4.5, and 7.5 years after surgery. More postoperative complications were noted in the HTO group. At 7- to 10-year follow-up, 71% of the HTO group and 65% of the UKA group had excellent KSS. Mean ROM was 103° after UKA (range, 35°-140°) and 117° after HTO (range, 85°-135°) during the same assessment. Although differences were not significant, Kaplan-Meier survival analysis was 60% for HTO and 77% for UKA at 10 years. Results were not promising for the implants used, compared with other implants, but the authors concluded that, because of improvements in implant designs and image-guided techniques, better long-term success can be expected with UKA than with HTO.

In another prospective study, Börjesson and colleagues⁴⁹ evaluated pain during walking, ROM, British Orthopaedic Association (BOA) scores, and gait variables at 1- and 5-year follow-up. Patients with moderate medial OA (Ahlbäck¹⁴ grade I-III) were randomly selected to undergo CWHTO or UKA (Brigham, DePuy). There were no significant differences in BOA scores, ROM, or pain during walking between the 2 groups at 3 months, 1 year, and 5 years after surgery. Gait analysis showed a significant difference in favor of UKA only at 3 months after surgery. At 1- and 5-year follow-up, no significant differences were noted.

To clarify current ambiguities, Fu and colleagues⁵⁰ performed a systematic review of all (11) comparative studies. These studies had a total of 5840 (5081 UKA, 759 HTO) patients. Although ROM was significantly better for the HTO group than the UKA group, the UKA group had significantly better functional results. Walking after surgery was significantly faster for the UKA group. The authors suggested the difference might be attributed to the different postoperative regimens—HTO patients wore a whole-leg plaster cast for 6 weeks, and UKA patients were allowed immediate postoperative weight-bearing. Regarding rates of survival and complications, pooled data showed no significant differences. Despite these results, the authors acknowledged the limitation of available randomized clinical trials and the multiple techniques and implants used. We share their assertion that larger prospective controlled trials are needed. These are crucial to getting a definitive answer regarding which of the 2 treatment strategies should be used for isolated compartment OA.

Current Trends in Use of UKA and HTO

Evaluation of national registries and recent reports showed a global shift in use of both HTO and UKA. Despite the lack of national HTO registries, a few reports have described use of TKA, UKA, and HTO in Western populations over the past 2 decades. Using 1998-2007 data from the Swedish Knee Arthroplasty Register, W-Dahl and colleagues⁵¹ found a 3-fold increase in UKA use, whereas HTO use was halved over the same period. Niinimäki and colleagues⁵² reported similar findings with the Finnish National Hospital Discharge Register. They noted a steady 6.8% annual decrease in osteotomies, whereas UKA use increased sharply after the Oxford UKA was introduced (Phase 3; Biomet). These findings are consistent with several reports from North America. In their epidemiologic analysis covering the period 1985-1990, Wright and colleagues⁵³ found an 11% to 14% annual decrease in osteotomies among the elderly, compared with an annual decrease of only 3% to 4% among patients younger than 65 years. Nwachukwu and colleagues⁵⁴ recently compared UKA and HTO practice patterns between 2007 and 2011, using data from a large US private payer insurance database. They noted an annual growth rate of 4.7% in UKA use, compared with an annual 3.9% decrease in HTO use. Furthermore, based on their subgroup analysis, they speculated there was a demographic shift toward UKA, as opposed to TKA, particularly in older women. Bolognesi and colleagues⁵⁵ investigated further. Evaluating all Medicare beneficiaries who underwent knee arthroplasty in the United States between 2000 and 2009, they noted a 1.7-fold increase in TKA use and a 6.2-fold increase in UKA use. As there were no substantial changes in patient characteristics over that period, the authors hypothesized that a possible broadening of inclusion criteria may have led to the increased use of UKA.

There is a possible multifactorial explanation for the current global shift in favor of UKA. First, UKA was once a technically demanding procedure, but improved surgical techniques, image guidance, and robot assistance⁵⁶ have made it relatively less difficult. Second, UKA surgery is associated with lower reported perioperative morbidities.⁵⁷ We think these factors have contributed to the global trend of less HTO use and more UKA use in the treatment of unicompartmental OA.

Conclusion

The modern literature suggests the inclusion criteria for HTO have been well investigated and defined; the UKA criteria remain a matter of debate but seem to be expanding. Long-term survival results seem to favor UKA, though patient satisfaction with both procedures is good to excellent. The broadening range of inclusion criteria and consistent reports of durable outcomes, coupled with excellent patient satisfaction, likely explain the shift toward UKA in the treatment of isolated compartment degeneration.

Am J Orthop. 2016;45(6):E355-E361. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

An increasingly number of patients with symptomatic isolated medial unicompartmental knee osteoarthritis (OA) are too young and too functionally active to be ideal candidates for total knee arthroplasty (TKA). Isolated medial compartment OA occurs in 10% to 29.5% of all cases, whereas the isolated lateral variant is less common, with a reported incidence of 1% to 7%.^1,2 In 1961, Jackson and Waugh³ introduced the high tibial osteotomy (HTO) as a surgical treatment for single-compartment OA. This procedure is designed to increase the life span of articular cartilage by unloading and redistributing the mechanical forces over the nonaffected compartment. Unicompartmental knee arthroplasty (UKA) was introduced in the 1970s as an alternative to TKA or HTO for single-compartment OA.

Since the introduction of these methods, there has been debate about which patients are appropriate candidates for each procedure. Improved surgical techniques and implant designs have led surgeons to reexamine the selection criteria and contraindications for these procedures. Furthermore, given the increasing popularity and use of UKA, the question arises as to whether HTO still has a role in clinical practice in the surgical treatment of medial OA of the knee.

To clarify current ambiguities, we review the modern indications, subjective outcome scores, and survivorship results of UKA and HTO in the treatment of isolated medial compartment degeneration of the knee. In addition, in a thorough review of the literature, we evaluate global trends in the use of both methods.

High Tibial Osteotomy for Medial Compartment OA

Indications

Before the introduction of TKA and UKA for single-compartment OA, surgical management consisted of HTO. When the mechanical axis is slightly overcorrected, the medial compartment is decompressed, ensuring tissue viability and delaying progressive compartment degeneration.

Traditionally, HTO is indicated for young (age <60 years), normal-weight, active patients with radiographic single-compartment OA.⁶ The knee should be stable and have good range of motion (ROM; flexion >120°), and pain should be localized to the tibiofemoral joint line.

Over the past few decades, numerous authors have reported similar inclusion criteria, clarifying their definition. This definition should be further refined in order to optimize survivorship and clinical outcomes.

Confirming age as an inclusion criterion for HTO, Trieb and colleagues⁷ found that the risk of failure was significantly (P = .046) higher for HTO patients older than 65 years than for those younger than 65 years (relative risk, 1.5). This finding agrees with findings of other studies, which suggests that, in particular, young patients benefit from HTO.^8-11

Moreover, there is a clear relation between HTO survival and obesity. In a study of 159 CWHTOs, Akizuki and colleagues¹² reported that preoperative body mass index (BMI) higher than 27.5 kg/m² was a significant risk factor for early failure. Using BMI higher than 30 kg/m² as a threshold, Howells and colleagues⁹ found significantly inferior Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) results for the obese group 5 years after HTO.

Radiographic evidence of severe preoperative compartment degeneration has been associated with early conversion to TKA. Flecher and colleagues¹¹ and van Raaij and colleagues¹³ both concluded the best long-term survival grades are achieved in HTO patients with mild compartment OA (Ahlbäck^14 grade I). The question then becomes whether these patients should be treated nonoperatively instead.^15,16The literature supports strict adherence to inclusion criteria in the selection of a potential HTO candidate. Age, BMI, and the preoperative state of OA should be taken into account in order to optimize clinical outcome and survivorship results in patients about to undergo HTO.

Outcomes

Multiple authors have described or compared the midterm or long-term results of the various surgical HTO techniques. Howells and colleagues⁹ noted overall survival rates of 87% (5 years after CWHTO) and 79% (10 years after CWHTO). Over the 10-year postoperative period, there was significant deterioration in clinical outcome scores and survivorship. Others authors have had similar findings.^17-19 van Raaij and colleagues¹³ found that the 10-year probability of survival after CWHTO was 75%. In 455 patients who underwent lateral CWHTO, Hui and colleagues⁸ found that 5-year probability of survival was 95%, 10-year probability was 79%, and 15-year probability was 56%. Niinimäki and colleagues¹⁰ used the Finnish Arthroplasty Register to report HTO survivorship at a national level. Using conversion to TKA as a cutoff, they noted 5-year survivorship of 89% and 10-year survivorship of 73%. To our knowledge, 2 groups, both in Japan, have reported substantially higher 15-year survival rates: 90%¹² and 93%.²⁰ The authors acknowledged that their results were significantly better than in other countries and that Japanese lifestyle, culture, and body habitus therefore require further investigation. At this time, it is not possible to compare their results with Western results.

In an attempt to compare the different survival rates of the various HTO techniques, Schallberger and colleagues²¹ conducted a retrospective study of OWHTOs and CWHTOs. At median follow-up of 16.5 years, comparative survival rates showed a trend of deterioration. Although data were limited, there were no significant differences in survival or functional outcome between the 2 techniques. In a recent randomized clinical trial, Duivenvoorden and colleagues⁵ compared these techniques’ midterm results (mean follow-up, 6 years). Clinical outcomes were not significantly different. There were more complications in the OWHTO group and more conversions to TKA in the CWHTO group. Considering these results, the authors suggested OWHTO without autologous bone graft is the best HTO treatment strategy for medial gonarthritis with varus malalignment of <12°.

The HTO results noted in these studies show a similar deteriorating trend; expected 10-year survivorship is 75%. Although modern implants and surgical techniques are being used, evidence supporting use of one surgical HTO method over another is lacking.

UKA for Medial Compartment OA

Indications

Since it was first introduced in the 1970s, use of UKA for single-compartment OA has been a subject of debate. The high failure rates reported at the time raised skepticism about the new treatment.²² Kozinn and Scott²³ defined classic indications and contraindications. Indications included isolated medial or lateral compartment OA or osteonecrosis of the knee, age over 60 years, and weight under 82 kg. In addition, the angular deformity of the affected lower extremity had to be <15° and passively correctable to neutral at time of surgery. Last, the flexion contracture had to be <5°, and ideal ROM was 90°. Contraindications included high activity, age under 60 years, and inflammatory arthritis. Strict adherence led to improved implant survival and lower revision rates. Because of improved surgical techniques, modern implant designs, and accumulating experience with the procedure, the surgical indications for UKA have expanded. Exact thresholds for UKA inclusion, however, remain unclear.

The modern literature is overturning the traditional idea that UKA is not indicated for patients under age 60 years.²³ Using KSS, Thompson and colleagues²⁴ found that younger patients did better than older patients 2 years after UKA using various types of implants. Analyzing survivorship results, Heyse and colleagues²⁵ concluded that UKA can be successful in patients under age 60 years and reported a 15-year survivorship rate of 85.6% and excellent outcome scores. Other authors have had similar findings.^26-28

Evaluating the influence of weight, Thompson and colleagues²⁴ found obese patients did not have a higher revision rate but did have slower progression of improvement 2 years after UKA. Cavaignac and colleagues²⁹ concluded that, at minimum follow-up of 7 years (range, 7-22 years), weight did not influence UKA survivorship. Other authors^30-33 have found no significant influence of BMI on survival.

Reports on preoperative radiographic parameters that can potentially influence UKA results are limited. In 113 medial UKAs studied by Niinimäki and colleagues,³⁴ mild medial compartment degeneration, seen on preoperative radiographs, was associated with significantly higher failure rates. The authors concluded that other treatment options should be favored in the absence of severe isolated compartment OA.

Although the classic indications defined by Kozinn and Scott²³ have yielded good to excellent UKA results, improvements in implants and surgical techniques^35-38 have extended the criteria. The modern literature demonstrates that age and BMI should not be used as criteria for excluding UKA candidates. Radiographically, there should be significant isolated compartment degeneration in order to optimize patient-reported outcome and survivorship.

Outcomes

Improved implant designs and modern minimally invasive techniques have effected a change in outcome results and a renewed interest in implants. Over the past decade, multiple authors have described the various modern UKA implants and their survivorship. Reports published since UKA was introduced in the 1970s show a continual increase in implant survival. Koskinen and colleagues,³⁹ using Finnish Arthroplasty Register data on 1819 UKAs performed between 1985 and 2003, found 10-year survival rates of 81% for Oxford implants (Zimmer Biomet), 79% for Miller-Galante II (Zimmer Biomet), 78% for Duracon (Howmedica), and 53% for PCA unicompartmental knee (Howmedica). Heyse and colleagues²⁵ reported 10- and 15-year survivorship data (93.5% and 86.3%, respectively) for 223 patients under age 60 years at the time of their index surgery (Genesis Unicondylar implant, Smith & Nephew), performed between 1993 and 2005. KSS was good to excellent. Similar numbers in cohorts under age 60 years were reported by Schai and colleagues²⁶ using the PFC system (Johnson & Johnson) and by Price and colleagues²⁷ using the medial Oxford UKA. Both groups reported excellent survivorship rates: 93% at 2- to 6-year follow-up and 91% at 10-year follow-up. The outcome in older patients seems satisfactory as well. In another multicenter report, by Price and colleagues,⁴⁰ medial Oxford UKAs had a 15-year survival rate of 93%. Berger and colleagues⁴¹ reported similar numbers for the Miller-Galante prosthesis. Survival rates were 98% (10 years) and 95.7% (13 years), and 92% of patients had good to excellent Hospital for Special Surgery knee scores.

Although various modern implants have had good to excellent results, the historical question of what type of UKA to use (mobile or fixed-bearing) remains unanswered. To try to address it, Peersman and colleagues⁴² performed a systematic review of 44 papers (9463 knees). The 2 implant types had comparable revision rates. Another recent retrospective study tried to determine what is crucial for implant survival: implant design or surgeon experience.⁴³ The authors concluded that prosthetic component positioning is key. Other authors have reported high-volume centers are crucial for satisfactory UKA results and lower revision rates.^44-46

Results of these studies indicate that, where UKAs are being performed in volume, 10-year survivorship rates higher than 90% and good to excellent outcomes can be expected.

UKA vs HTO

Cohort studies that have directly compared the 2 treatment modalities are scarce, and most have been retrospective. In a prospective study, Stukenborg-Colsman and colleagues⁴⁷ randomized patients with medial compartment OA to undergo either CWHTO (32 patients) with a technique reported by Coventry⁴⁸ or UKA (28 patients) with the unicondylar knee sliding prosthesis, Tübingen pattern (Aesculap), between 1988 and 1991. Patients were assessed 2.5, 4.5, and 7.5 years after surgery. More postoperative complications were noted in the HTO group. At 7- to 10-year follow-up, 71% of the HTO group and 65% of the UKA group had excellent KSS. Mean ROM was 103° after UKA (range, 35°-140°) and 117° after HTO (range, 85°-135°) during the same assessment. Although differences were not significant, Kaplan-Meier survival analysis was 60% for HTO and 77% for UKA at 10 years. Results were not promising for the implants used, compared with other implants, but the authors concluded that, because of improvements in implant designs and image-guided techniques, better long-term success can be expected with UKA than with HTO.

In another prospective study, Börjesson and colleagues⁴⁹ evaluated pain during walking, ROM, British Orthopaedic Association (BOA) scores, and gait variables at 1- and 5-year follow-up. Patients with moderate medial OA (Ahlbäck¹⁴ grade I-III) were randomly selected to undergo CWHTO or UKA (Brigham, DePuy). There were no significant differences in BOA scores, ROM, or pain during walking between the 2 groups at 3 months, 1 year, and 5 years after surgery. Gait analysis showed a significant difference in favor of UKA only at 3 months after surgery. At 1- and 5-year follow-up, no significant differences were noted.

To clarify current ambiguities, Fu and colleagues⁵⁰ performed a systematic review of all (11) comparative studies. These studies had a total of 5840 (5081 UKA, 759 HTO) patients. Although ROM was significantly better for the HTO group than the UKA group, the UKA group had significantly better functional results. Walking after surgery was significantly faster for the UKA group. The authors suggested the difference might be attributed to the different postoperative regimens—HTO patients wore a whole-leg plaster cast for 6 weeks, and UKA patients were allowed immediate postoperative weight-bearing. Regarding rates of survival and complications, pooled data showed no significant differences. Despite these results, the authors acknowledged the limitation of available randomized clinical trials and the multiple techniques and implants used. We share their assertion that larger prospective controlled trials are needed. These are crucial to getting a definitive answer regarding which of the 2 treatment strategies should be used for isolated compartment OA.

Current Trends in Use of UKA and HTO

Evaluation of national registries and recent reports showed a global shift in use of both HTO and UKA. Despite the lack of national HTO registries, a few reports have described use of TKA, UKA, and HTO in Western populations over the past 2 decades. Using 1998-2007 data from the Swedish Knee Arthroplasty Register, W-Dahl and colleagues⁵¹ found a 3-fold increase in UKA use, whereas HTO use was halved over the same period. Niinimäki and colleagues⁵² reported similar findings with the Finnish National Hospital Discharge Register. They noted a steady 6.8% annual decrease in osteotomies, whereas UKA use increased sharply after the Oxford UKA was introduced (Phase 3; Biomet). These findings are consistent with several reports from North America. In their epidemiologic analysis covering the period 1985-1990, Wright and colleagues⁵³ found an 11% to 14% annual decrease in osteotomies among the elderly, compared with an annual decrease of only 3% to 4% among patients younger than 65 years. Nwachukwu and colleagues⁵⁴ recently compared UKA and HTO practice patterns between 2007 and 2011, using data from a large US private payer insurance database. They noted an annual growth rate of 4.7% in UKA use, compared with an annual 3.9% decrease in HTO use. Furthermore, based on their subgroup analysis, they speculated there was a demographic shift toward UKA, as opposed to TKA, particularly in older women. Bolognesi and colleagues⁵⁵ investigated further. Evaluating all Medicare beneficiaries who underwent knee arthroplasty in the United States between 2000 and 2009, they noted a 1.7-fold increase in TKA use and a 6.2-fold increase in UKA use. As there were no substantial changes in patient characteristics over that period, the authors hypothesized that a possible broadening of inclusion criteria may have led to the increased use of UKA.

There is a possible multifactorial explanation for the current global shift in favor of UKA. First, UKA was once a technically demanding procedure, but improved surgical techniques, image guidance, and robot assistance⁵⁶ have made it relatively less difficult. Second, UKA surgery is associated with lower reported perioperative morbidities.⁵⁷ We think these factors have contributed to the global trend of less HTO use and more UKA use in the treatment of unicompartmental OA.

Conclusion

The modern literature suggests the inclusion criteria for HTO have been well investigated and defined; the UKA criteria remain a matter of debate but seem to be expanding. Long-term survival results seem to favor UKA, though patient satisfaction with both procedures is good to excellent. The broadening range of inclusion criteria and consistent reports of durable outcomes, coupled with excellent patient satisfaction, likely explain the shift toward UKA in the treatment of isolated compartment degeneration.

Am J Orthop. 2016;45(6):E355-E361. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.

An increasingly number of patients with symptomatic isolated medial unicompartmental knee osteoarthritis (OA) are too young and too functionally active to be ideal candidates for total knee arthroplasty (TKA). Isolated medial compartment OA occurs in 10% to 29.5% of all cases, whereas the isolated lateral variant is less common, with a reported incidence of 1% to 7%.^1,2 In 1961, Jackson and Waugh³ introduced the high tibial osteotomy (HTO) as a surgical treatment for single-compartment OA. This procedure is designed to increase the life span of articular cartilage by unloading and redistributing the mechanical forces over the nonaffected compartment. Unicompartmental knee arthroplasty (UKA) was introduced in the 1970s as an alternative to TKA or HTO for single-compartment OA.

Since the introduction of these methods, there has been debate about which patients are appropriate candidates for each procedure. Improved surgical techniques and implant designs have led surgeons to reexamine the selection criteria and contraindications for these procedures. Furthermore, given the increasing popularity and use of UKA, the question arises as to whether HTO still has a role in clinical practice in the surgical treatment of medial OA of the knee.

To clarify current ambiguities, we review the modern indications, subjective outcome scores, and survivorship results of UKA and HTO in the treatment of isolated medial compartment degeneration of the knee. In addition, in a thorough review of the literature, we evaluate global trends in the use of both methods.

High Tibial Osteotomy for Medial Compartment OA

Indications

Before the introduction of TKA and UKA for single-compartment OA, surgical management consisted of HTO. When the mechanical axis is slightly overcorrected, the medial compartment is decompressed, ensuring tissue viability and delaying progressive compartment degeneration.

Traditionally, HTO is indicated for young (age <60 years), normal-weight, active patients with radiographic single-compartment OA.⁶ The knee should be stable and have good range of motion (ROM; flexion >120°), and pain should be localized to the tibiofemoral joint line.

Over the past few decades, numerous authors have reported similar inclusion criteria, clarifying their definition. This definition should be further refined in order to optimize survivorship and clinical outcomes.

Confirming age as an inclusion criterion for HTO, Trieb and colleagues⁷ found that the risk of failure was significantly (P = .046) higher for HTO patients older than 65 years than for those younger than 65 years (relative risk, 1.5). This finding agrees with findings of other studies, which suggests that, in particular, young patients benefit from HTO.^8-11

Moreover, there is a clear relation between HTO survival and obesity. In a study of 159 CWHTOs, Akizuki and colleagues¹² reported that preoperative body mass index (BMI) higher than 27.5 kg/m² was a significant risk factor for early failure. Using BMI higher than 30 kg/m² as a threshold, Howells and colleagues⁹ found significantly inferior Knee Society Score (KSS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) results for the obese group 5 years after HTO.

Radiographic evidence of severe preoperative compartment degeneration has been associated with early conversion to TKA. Flecher and colleagues¹¹ and van Raaij and colleagues¹³ both concluded the best long-term survival grades are achieved in HTO patients with mild compartment OA (Ahlbäck^14 grade I). The question then becomes whether these patients should be treated nonoperatively instead.^15,16The literature supports strict adherence to inclusion criteria in the selection of a potential HTO candidate. Age, BMI, and the preoperative state of OA should be taken into account in order to optimize clinical outcome and survivorship results in patients about to undergo HTO.

Outcomes

Multiple authors have described or compared the midterm or long-term results of the various surgical HTO techniques. Howells and colleagues⁹ noted overall survival rates of 87% (5 years after CWHTO) and 79% (10 years after CWHTO). Over the 10-year postoperative period, there was significant deterioration in clinical outcome scores and survivorship. Others authors have had similar findings.^17-19 van Raaij and colleagues¹³ found that the 10-year probability of survival after CWHTO was 75%. In 455 patients who underwent lateral CWHTO, Hui and colleagues⁸ found that 5-year probability of survival was 95%, 10-year probability was 79%, and 15-year probability was 56%. Niinimäki and colleagues¹⁰ used the Finnish Arthroplasty Register to report HTO survivorship at a national level. Using conversion to TKA as a cutoff, they noted 5-year survivorship of 89% and 10-year survivorship of 73%. To our knowledge, 2 groups, both in Japan, have reported substantially higher 15-year survival rates: 90%¹² and 93%.²⁰ The authors acknowledged that their results were significantly better than in other countries and that Japanese lifestyle, culture, and body habitus therefore require further investigation. At this time, it is not possible to compare their results with Western results.

In an attempt to compare the different survival rates of the various HTO techniques, Schallberger and colleagues²¹ conducted a retrospective study of OWHTOs and CWHTOs. At median follow-up of 16.5 years, comparative survival rates showed a trend of deterioration. Although data were limited, there were no significant differences in survival or functional outcome between the 2 techniques. In a recent randomized clinical trial, Duivenvoorden and colleagues⁵ compared these techniques’ midterm results (mean follow-up, 6 years). Clinical outcomes were not significantly different. There were more complications in the OWHTO group and more conversions to TKA in the CWHTO group. Considering these results, the authors suggested OWHTO without autologous bone graft is the best HTO treatment strategy for medial gonarthritis with varus malalignment of <12°.

The HTO results noted in these studies show a similar deteriorating trend; expected 10-year survivorship is 75%. Although modern implants and surgical techniques are being used, evidence supporting use of one surgical HTO method over another is lacking.

UKA for Medial Compartment OA

Indications

Since it was first introduced in the 1970s, use of UKA for single-compartment OA has been a subject of debate. The high failure rates reported at the time raised skepticism about the new treatment.²² Kozinn and Scott²³ defined classic indications and contraindications. Indications included isolated medial or lateral compartment OA or osteonecrosis of the knee, age over 60 years, and weight under 82 kg. In addition, the angular deformity of the affected lower extremity had to be <15° and passively correctable to neutral at time of surgery. Last, the flexion contracture had to be <5°, and ideal ROM was 90°. Contraindications included high activity, age under 60 years, and inflammatory arthritis. Strict adherence led to improved implant survival and lower revision rates. Because of improved surgical techniques, modern implant designs, and accumulating experience with the procedure, the surgical indications for UKA have expanded. Exact thresholds for UKA inclusion, however, remain unclear.

The modern literature is overturning the traditional idea that UKA is not indicated for patients under age 60 years.²³ Using KSS, Thompson and colleagues²⁴ found that younger patients did better than older patients 2 years after UKA using various types of implants. Analyzing survivorship results, Heyse and colleagues²⁵ concluded that UKA can be successful in patients under age 60 years and reported a 15-year survivorship rate of 85.6% and excellent outcome scores. Other authors have had similar findings.^26-28

Evaluating the influence of weight, Thompson and colleagues²⁴ found obese patients did not have a higher revision rate but did have slower progression of improvement 2 years after UKA. Cavaignac and colleagues²⁹ concluded that, at minimum follow-up of 7 years (range, 7-22 years), weight did not influence UKA survivorship. Other authors^30-33 have found no significant influence of BMI on survival.

Reports on preoperative radiographic parameters that can potentially influence UKA results are limited. In 113 medial UKAs studied by Niinimäki and colleagues,³⁴ mild medial compartment degeneration, seen on preoperative radiographs, was associated with significantly higher failure rates. The authors concluded that other treatment options should be favored in the absence of severe isolated compartment OA.

Although the classic indications defined by Kozinn and Scott²³ have yielded good to excellent UKA results, improvements in implants and surgical techniques^35-38 have extended the criteria. The modern literature demonstrates that age and BMI should not be used as criteria for excluding UKA candidates. Radiographically, there should be significant isolated compartment degeneration in order to optimize patient-reported outcome and survivorship.

Outcomes

Improved implant designs and modern minimally invasive techniques have effected a change in outcome results and a renewed interest in implants. Over the past decade, multiple authors have described the various modern UKA implants and their survivorship. Reports published since UKA was introduced in the 1970s show a continual increase in implant survival. Koskinen and colleagues,³⁹ using Finnish Arthroplasty Register data on 1819 UKAs performed between 1985 and 2003, found 10-year survival rates of 81% for Oxford implants (Zimmer Biomet), 79% for Miller-Galante II (Zimmer Biomet), 78% for Duracon (Howmedica), and 53% for PCA unicompartmental knee (Howmedica). Heyse and colleagues²⁵ reported 10- and 15-year survivorship data (93.5% and 86.3%, respectively) for 223 patients under age 60 years at the time of their index surgery (Genesis Unicondylar implant, Smith & Nephew), performed between 1993 and 2005. KSS was good to excellent. Similar numbers in cohorts under age 60 years were reported by Schai and colleagues²⁶ using the PFC system (Johnson & Johnson) and by Price and colleagues²⁷ using the medial Oxford UKA. Both groups reported excellent survivorship rates: 93% at 2- to 6-year follow-up and 91% at 10-year follow-up. The outcome in older patients seems satisfactory as well. In another multicenter report, by Price and colleagues,⁴⁰ medial Oxford UKAs had a 15-year survival rate of 93%. Berger and colleagues⁴¹ reported similar numbers for the Miller-Galante prosthesis. Survival rates were 98% (10 years) and 95.7% (13 years), and 92% of patients had good to excellent Hospital for Special Surgery knee scores.

Although various modern implants have had good to excellent results, the historical question of what type of UKA to use (mobile or fixed-bearing) remains unanswered. To try to address it, Peersman and colleagues⁴² performed a systematic review of 44 papers (9463 knees). The 2 implant types had comparable revision rates. Another recent retrospective study tried to determine what is crucial for implant survival: implant design or surgeon experience.⁴³ The authors concluded that prosthetic component positioning is key. Other authors have reported high-volume centers are crucial for satisfactory UKA results and lower revision rates.^44-46

Results of these studies indicate that, where UKAs are being performed in volume, 10-year survivorship rates higher than 90% and good to excellent outcomes can be expected.

UKA vs HTO

Cohort studies that have directly compared the 2 treatment modalities are scarce, and most have been retrospective. In a prospective study, Stukenborg-Colsman and colleagues⁴⁷ randomized patients with medial compartment OA to undergo either CWHTO (32 patients) with a technique reported by Coventry⁴⁸ or UKA (28 patients) with the unicondylar knee sliding prosthesis, Tübingen pattern (Aesculap), between 1988 and 1991. Patients were assessed 2.5, 4.5, and 7.5 years after surgery. More postoperative complications were noted in the HTO group. At 7- to 10-year follow-up, 71% of the HTO group and 65% of the UKA group had excellent KSS. Mean ROM was 103° after UKA (range, 35°-140°) and 117° after HTO (range, 85°-135°) during the same assessment. Although differences were not significant, Kaplan-Meier survival analysis was 60% for HTO and 77% for UKA at 10 years. Results were not promising for the implants used, compared with other implants, but the authors concluded that, because of improvements in implant designs and image-guided techniques, better long-term success can be expected with UKA than with HTO.

In another prospective study, Börjesson and colleagues⁴⁹ evaluated pain during walking, ROM, British Orthopaedic Association (BOA) scores, and gait variables at 1- and 5-year follow-up. Patients with moderate medial OA (Ahlbäck¹⁴ grade I-III) were randomly selected to undergo CWHTO or UKA (Brigham, DePuy). There were no significant differences in BOA scores, ROM, or pain during walking between the 2 groups at 3 months, 1 year, and 5 years after surgery. Gait analysis showed a significant difference in favor of UKA only at 3 months after surgery. At 1- and 5-year follow-up, no significant differences were noted.

To clarify current ambiguities, Fu and colleagues⁵⁰ performed a systematic review of all (11) comparative studies. These studies had a total of 5840 (5081 UKA, 759 HTO) patients. Although ROM was significantly better for the HTO group than the UKA group, the UKA group had significantly better functional results. Walking after surgery was significantly faster for the UKA group. The authors suggested the difference might be attributed to the different postoperative regimens—HTO patients wore a whole-leg plaster cast for 6 weeks, and UKA patients were allowed immediate postoperative weight-bearing. Regarding rates of survival and complications, pooled data showed no significant differences. Despite these results, the authors acknowledged the limitation of available randomized clinical trials and the multiple techniques and implants used. We share their assertion that larger prospective controlled trials are needed. These are crucial to getting a definitive answer regarding which of the 2 treatment strategies should be used for isolated compartment OA.

Current Trends in Use of UKA and HTO

Evaluation of national registries and recent reports showed a global shift in use of both HTO and UKA. Despite the lack of national HTO registries, a few reports have described use of TKA, UKA, and HTO in Western populations over the past 2 decades. Using 1998-2007 data from the Swedish Knee Arthroplasty Register, W-Dahl and colleagues⁵¹ found a 3-fold increase in UKA use, whereas HTO use was halved over the same period. Niinimäki and colleagues⁵² reported similar findings with the Finnish National Hospital Discharge Register. They noted a steady 6.8% annual decrease in osteotomies, whereas UKA use increased sharply after the Oxford UKA was introduced (Phase 3; Biomet). These findings are consistent with several reports from North America. In their epidemiologic analysis covering the period 1985-1990, Wright and colleagues⁵³ found an 11% to 14% annual decrease in osteotomies among the elderly, compared with an annual decrease of only 3% to 4% among patients younger than 65 years. Nwachukwu and colleagues⁵⁴ recently compared UKA and HTO practice patterns between 2007 and 2011, using data from a large US private payer insurance database. They noted an annual growth rate of 4.7% in UKA use, compared with an annual 3.9% decrease in HTO use. Furthermore, based on their subgroup analysis, they speculated there was a demographic shift toward UKA, as opposed to TKA, particularly in older women. Bolognesi and colleagues⁵⁵ investigated further. Evaluating all Medicare beneficiaries who underwent knee arthroplasty in the United States between 2000 and 2009, they noted a 1.7-fold increase in TKA use and a 6.2-fold increase in UKA use. As there were no substantial changes in patient characteristics over that period, the authors hypothesized that a possible broadening of inclusion criteria may have led to the increased use of UKA.

There is a possible multifactorial explanation for the current global shift in favor of UKA. First, UKA was once a technically demanding procedure, but improved surgical techniques, image guidance, and robot assistance⁵⁶ have made it relatively less difficult. Second, UKA surgery is associated with lower reported perioperative morbidities.⁵⁷ We think these factors have contributed to the global trend of less HTO use and more UKA use in the treatment of unicompartmental OA.

Conclusion

The modern literature suggests the inclusion criteria for HTO have been well investigated and defined; the UKA criteria remain a matter of debate but seem to be expanding. Long-term survival results seem to favor UKA, though patient satisfaction with both procedures is good to excellent. The broadening range of inclusion criteria and consistent reports of durable outcomes, coupled with excellent patient satisfaction, likely explain the shift toward UKA in the treatment of isolated compartment degeneration.

Am J Orthop. 2016;45(6):E355-E361. Copyright Frontline Medical Communications Inc. 2016. All rights reserved.