The American Journal of Orthopedics

Patients with atherosclerosis are at a greater risk of osteoporosis, and a recent study published in the American Journal of Physiology—Endocrinology and Metabolism explores how the development of atherosclerosis might encourage osteoporosis.

Researchers used mice to investigate the impact of oxidized lipids on bone homeostasis and to search for underlying pathogenic pathways.

Mice fed a high-fat diet for 3 months showed increased levels of oxidized lipids in bone, and decreased femoral and vertebral trabecular and cortical bone mass, compared with mice on a normal diet.

Researchers also found that atherosclerotic mice had fewer osteoblasts. While osteoclasts numbers decreased modestly in some bones, there were significantly more osteoclasts than osteoblasts overall, favoring bone loss. The researchers also observed that atherosclerosis-induced inflammation in the bone interfered with the maturation of new osteoblast cells, which accounted for the reduction in number of osteoblasts.

Patients with atherosclerosis are at a greater risk of osteoporosis, and a recent study published in the American Journal of Physiology—Endocrinology and Metabolism explores how the development of atherosclerosis might encourage osteoporosis.

Researchers used mice to investigate the impact of oxidized lipids on bone homeostasis and to search for underlying pathogenic pathways.

Mice fed a high-fat diet for 3 months showed increased levels of oxidized lipids in bone, and decreased femoral and vertebral trabecular and cortical bone mass, compared with mice on a normal diet.

Researchers also found that atherosclerotic mice had fewer osteoblasts. While osteoclasts numbers decreased modestly in some bones, there were significantly more osteoclasts than osteoblasts overall, favoring bone loss. The researchers also observed that atherosclerosis-induced inflammation in the bone interfered with the maturation of new osteoblast cells, which accounted for the reduction in number of osteoblasts.

Patients with atherosclerosis are at a greater risk of osteoporosis, and a recent study published in the American Journal of Physiology—Endocrinology and Metabolism explores how the development of atherosclerosis might encourage osteoporosis.

Researchers used mice to investigate the impact of oxidized lipids on bone homeostasis and to search for underlying pathogenic pathways.

Mice fed a high-fat diet for 3 months showed increased levels of oxidized lipids in bone, and decreased femoral and vertebral trabecular and cortical bone mass, compared with mice on a normal diet.

Researchers also found that atherosclerotic mice had fewer osteoblasts. While osteoclasts numbers decreased modestly in some bones, there were significantly more osteoclasts than osteoblasts overall, favoring bone loss. The researchers also observed that atherosclerosis-induced inflammation in the bone interfered with the maturation of new osteoblast cells, which accounted for the reduction in number of osteoblasts.

Patients who receive a peripheral nerve block during hip or knee replacement surgery are less likely to experience complications, according to a recent large retrospective study.

Researchers reviewed more than 1 million hip and knee replacements performed between 2006 and 2013 using data from approximately 3,000 hospitals in the United States.

Investigators compiled information on cardiac, pulmonary, gastrointestinal, and renal complications. They also determined the rate of infections, wound complications, and inpatient falls. In addition, they analyzed data on resource utilization, which included the number of blood transfusions needed, admission to an intensive care unit, opioid consumption, length of hospital stay, and the cost of hospitalization.

They looked at data for 342,726 patients who had hip replacement surgery and 719,426 who had knee replacement surgery.

Overall, 18% of the patients received a peripheral nerve block. They found the rate peripheral nerve block use among patients with knee replacement increased from 15.2% in 2006 to 24.5% in 2013. The use of peripheral nerve blocks was associated with significantly lower odds for almost all complications.

A strong effect was seen for cardiac complications in patients with knee replacement and for wound complications in people who had hip replacement. Similar patterns were observed for resource utilization, particularly in length of hospital stay among patients with hip replacement.

Patients who receive a peripheral nerve block during hip or knee replacement surgery are less likely to experience complications, according to a recent large retrospective study.

Researchers reviewed more than 1 million hip and knee replacements performed between 2006 and 2013 using data from approximately 3,000 hospitals in the United States.

Investigators compiled information on cardiac, pulmonary, gastrointestinal, and renal complications. They also determined the rate of infections, wound complications, and inpatient falls. In addition, they analyzed data on resource utilization, which included the number of blood transfusions needed, admission to an intensive care unit, opioid consumption, length of hospital stay, and the cost of hospitalization.

They looked at data for 342,726 patients who had hip replacement surgery and 719,426 who had knee replacement surgery.

Overall, 18% of the patients received a peripheral nerve block. They found the rate peripheral nerve block use among patients with knee replacement increased from 15.2% in 2006 to 24.5% in 2013. The use of peripheral nerve blocks was associated with significantly lower odds for almost all complications.

A strong effect was seen for cardiac complications in patients with knee replacement and for wound complications in people who had hip replacement. Similar patterns were observed for resource utilization, particularly in length of hospital stay among patients with hip replacement.

Patients who receive a peripheral nerve block during hip or knee replacement surgery are less likely to experience complications, according to a recent large retrospective study.

Researchers reviewed more than 1 million hip and knee replacements performed between 2006 and 2013 using data from approximately 3,000 hospitals in the United States.

Investigators compiled information on cardiac, pulmonary, gastrointestinal, and renal complications. They also determined the rate of infections, wound complications, and inpatient falls. In addition, they analyzed data on resource utilization, which included the number of blood transfusions needed, admission to an intensive care unit, opioid consumption, length of hospital stay, and the cost of hospitalization.

They looked at data for 342,726 patients who had hip replacement surgery and 719,426 who had knee replacement surgery.

Overall, 18% of the patients received a peripheral nerve block. They found the rate peripheral nerve block use among patients with knee replacement increased from 15.2% in 2006 to 24.5% in 2013. The use of peripheral nerve blocks was associated with significantly lower odds for almost all complications.

A strong effect was seen for cardiac complications in patients with knee replacement and for wound complications in people who had hip replacement. Similar patterns were observed for resource utilization, particularly in length of hospital stay among patients with hip replacement.

Chronic anticoagulation is a common preex­isting condition in patients undergoing total joint arthroplasty (TJA). Atrial fibrillation (AF), the most common underlying disorder requiring chronic anticoagulation, affects more than 3 million patients in the United States—a number that is projected to increase to 16 million by 2050.^1,2 Other common indications for anticoagulation are deep vein thrombosis (DVT) treatment, presence of a prosthetic heart valve, and venous thromboembolism (VTE) prevention after hip or knee arthroplasty. These patients face the additional risks of hemorrhage, persistent wound drainage, hematoma formation, transfusion requirements, periprosthetic joint infection, and longer hospital stay.¹ Chronic anticoagulation traditionally has been managed with warfarin, which inhibits production of the vitamin K–dependent clotting factors II, VII, IX, and X. However, the new novel oral anticoagulants (NOACs), which target individual factors in the clotting cascade, are gaining favor as chronic anticoagulant agents because of their ease of use and improved efficacy and safety. These agents include the factor IIA inhibitor dabigatran (Pradaxa) and the direct factor Xa inhibitors rivaroxaban (Xarelto) and apixaban (Eliquis).

Management of patients at risk for thromboembolism and bleeding issues, particularly within the context of elective, urgent, or emergent orthopedic surgeries, is an evolving area. Understanding the pharmacokinetics, conventional laboratory tests, dosing, and reversal methods for NOACs is important, especially because clinical data are limited and the treatment itself can cause clinically significant harm.

In this article, we review the medical literature on these medications, their mechanism of action, and their reversal agents, and outline a practical approach for managing patients during the perioperative period.

Dabigatran

In October 2010, dabigatran became the first NOAC approved by the US Food and Drug Administration (FDA) for the prevention of arterial thromboembolic events in patients with nonvalvular AF, on the basis of the results of the RELY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial. Dabigatran is an oral factor IIA (thrombin) inhibitor. From time of ingestion, dabigatran takes 1.25 to 3 hours to reach peak plasma concentration. It has a half-life of 12 to 14 hours, is excreted predominantly by the kidneys (80%), and is renally dosed. The usual dose is 150 mg 2 times daily if creatinine clearance (CrCl) is >30 mL/minute, or 75 mg 2 times daily if CrCl is 15 to 30 mL/minute.³ Dabigatran is not recommended for patients with CrCl <15 mL/minute.

Dabigatran affects prothrombin time (PT), activated partial thromboplastin time (aPTT), ecarin clotting time, and thrombin time, with the latter 2 providing the most accurate means of monitoring appropriate drug levels.^3,4 Of the tests commonly used to assess coagulation hemostasis in hospitals, normalization of thrombin time and aPTT provide the most accurate results (Table 1). The pharmacokinetics of dabigatran mandate consideration of dose, time of ingestion relative to time of blood sampling, and renal function in the assessment of coagulation hemostasis.

For elective surgeries, the periprocedure recommendation for patients being treated with dabigatran is to discontinue the medication 3 to 4 days before an operation if CrCl is ≥50 mL/minute, or 4 to 5 days beforehand if CrCl is <50 mL/minute.³ There is no antidote for dabigatran. In an in vitro model, activated charcoal reduced 99.9% of dabigatran absorption after recent ingestion.³ According to case reports, acute hemodialysis successfully removed 60% of the medication after 6 hours.⁵ In patients with end-stage renal disease, hemodialysis removed up to 68% of active dabigatran after 4 hours.³

Pernod and colleagues6 proposed that urgent surgeries can proceed if the concentration of dabigatran is ≤30 ng/mL—equivalent to normal aPTT. Their dictum was extrapolated from the data of patients who underwent elective surgeries while being treated with dabigatran, as recorded during the RELY trial. According to Pernod and colleagues,⁶ if aPTT is increased (probable drug level, ≥30 ng/mL), surgery should be postponed for up to 12 hours, with aPTT checked again and the process repeated if the concentration of dabigatran is still elevated and surgery can continue to be delayed. In patients who require urgent surgical interventions, we previously utilized nanofiltered activated prothrombin complex concentrate (aPCC; Feiba NF) 30 to 50 IU/kg over prothrombin complex concentrate (PCC; Kcentra or Bebulin) 25 to 50 IU/kg, as supported by in vitro and animal model studies and anecdotal case reports. However, neither aPCC nor PCC fully corrects the abnormalities evident on hemostasis tests.3,6 In October 2015, the FDA approved Idarucizumab (Praxbind), an injectable monoclonal antibody fragment that binds to dabigatran, as a reversing agent for use in urgent/emergent settings. Recommendation is to administer two 50-ml bolus infusions, each containing 2.5 g of idarucizumab, no more than 15 minutes apart.⁷ Additionally, hemodialysis could be discussed before surgery, with the understanding that it will take a long time to reach the threshold of 30 ng/mL in these patients (Table 2).

Rivaroxaban

Rivaroxaban is an oral direct factor Xa inhibitor that was initially approved in November 2011 for the prevention of stroke and systemic embolism in patients with nonvalvular AF. Since then, clinical use of rivaroxaban has been expanded to include prevention of VTE after elective hip or knee arthroplasty as well as treatment of DVT and prevention of recurrent VTE after acute DVT. In the phase 3 ROCKET AF (Rivaroxaban Once-Daily Oral Direct Factor Xa Inhibition Compared With Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation) study, rivaroxaban 20 mg daily (CrCl, ≥50 mL/min) and rivaroxaban 15 mg daily (CrCl, 15-49 mL/min) were equally effective as warfarin. Compared with warfarin, rivaroxaban had a similar safety rate for bleeding and adverse events but fewer intracranial hemorrhage and fatal bleeding events.⁸ On the basis of the outcomes of the RECORD (Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Venous Thrombosis and Pulmonary Embolism) studies comparing rivaroxaban and enoxaparin sodium, rivaroxaban 10 mg daily was approved for the prevention of VTE and pulmonary embolism after elective hip or knee arthroplasty.⁸

The half-life of rivaroxaban is 5 to 9 hours in the young and 11 to 13 hours in the elderly.⁸ As rivaroxaban takes 2 to 4 hours after ingestion to reach peak plasma concentration, it is important to know the timing and the dose taken. Because of the short half-life and rapid onset of action of this medication, bridging with another anticoagulant is not required when rivaroxaban is discontinued before surgery or initiated after surgery.⁸ The recommendation is to withhold rivaroxaban for 24 to 48 hours before surgery and then to administer the first postoperative dose 6 to 10 hours after surgery, or when hemostasis is achieved (Table 1).

PT is recommended for rivaroxaban detection. Conventional assays are not sensitive at low concentrations, and degree of prolongation does not reliably predict amount of medication present.^3,9 However, normal PT corresponds to a drug concentration of about 30 ng/mL and is considered safe for patients undergoing surgical intervention without increased risk for bleeding.⁶ This recommendation was extrapolated from data in the ROCKET AF study of patients who underwent elective surgeries while on rivaroxaban.⁶ Commercially available chromogenic anti–factor Xa assays, used with a rivaroxaban calibration curve, are sensitive and specific for rivaroxaban plasma concentrations.^3,8 However, these assays are not widely available.

If a bleeding complication occurs in a patient who is being treated with rivaroxaban, the next rivaroxaban dose should be delayed, or treatment should be discontinued, as appropriate.⁸ Urgency of surgery should be weighed against risk for bleeding complications on a case-by-case basis. This decision is deferred to the clinical judgment of the surgeon. In the case of a patient with severe, life-threatening bleeding or a patient who requires emergent surgery, PCC 25-50 IU/kg is the recommended reversal agent.⁹ Recombinant factor VIIa and aPCC have been used in experimental settings, but there is concern about the greater prothrombotic potential of these agents compared with PCC⁸ (Table 2).

Apixaban

Apixaban is the second factor Xa inhibitor introduced in the United States and the first to show—in the ARISTOTLE (Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation) study—efficacy superior to that of warfarin for the prevention of stroke and systemic embolism, all-cause mortality, and major bleeding. Furthermore, in the AVERROES (Apixaban Versus Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin K Antagonist Treatment) study, apixaban used in AF patients who were deemed not suitable for warfarin proved to be more effective than aspirin for stroke prevention, and had a similar rate of major bleeding.¹⁰ Apixaban is administered in a 5-mg dose 2 times daily. It has a half-life of 10 to 14 hours, is highly protein-bound, and has predominantly fecal excretion (27% is renal). Apixaban can prolong PT, but the correlation is nonlinear. Barrett and colleagues¹¹ found that chromogenic anti–factor Xa assays provided the most accurate readings of apixaban plasma concentrations. Normal anti–factor Xa activity in patients being treated with apixaban suggests low drug levels and an intact hemostatic function, which are indicators of low bleeding risk with surgical intervention³ (Table 1).

Similar to other NOACs, apixaban has no antidote. In vitro testing showed that PCC improved thrombin generation when added to the blood of healthy donors who had received apixaban. Despite the lack of clinical experience, use of PCC 50 IU/kg may be reasonable for apixaban patients with severe or life-threatening bleeding³ (Table 2). Unlike dabigatran, apixaban cannot be eliminated with dialysis because of its high degree of protein binding. In nonemergent circumstances, delaying surgery 24 to 48 hours is considered effective in reducing the concentration of apixaban to a range that does not cause additional risk for bleeding.

Conclusion

Compared with warfarin, the NOACs dabigatran, rivaroxaban, and apixaban are efficacious and safe. Because of their steady pharmacokinetics, they do not require regular coagulation testing, as is the case with warfarin. These NOACs have been approved for the prevention of stroke and thromboembolic events in patients with nonvalvular AF; rivaroxaban has also been approved for VTE prevention after total hip or knee arthroplasty, for DVT treatment, and for prevention of recurrent VTE after acute DVT. Other options for VTE prophylaxis after hip and knee surgery are addressed in the guidelines issued by the American Academy of Orthopaedic Surgeons in 2011.¹² As the incidence of chronic anticoagulation continues to increase among patients undergoing TJA, orthopedic surgeons need to be aware of the mechanism of action of these NOACs, as well as their pharmacokinetics and available reversal agents. Aggarwal and colleagues1 found that AF patients undergoing TJA had longer hospital stays, increased transfusion requirements, and increased risk for periprosthetic joint infection and unplanned hospital readmission.

The anticoagulation tests recommended for evaluation of hemostasis and drug reversal are normalization of aPTT for dabigatran; PT for rivaroxaban; and chromogenic anti–factor Xa activity for apixaban³ (Table 2). Although several research projects are being planned to develop an antidote for these medications, no antidote has been approved for human trials. The coagulation agents currently being used for reversal of NOACs are nonactivated PCC (Kcentra, Bebulin) and aPCC. Kcentra is a 4-factor PCC (II, VII, IX, X), and Bebulin is a 3-factor PCC (II, IX, X). Most authors recommend using 4-factor PCC 25 to 50 IU/kg. In vivo studies and animal studies have shown that nanofiltered aPCC (Feiba NF) at doses of 30 to 50 IU/kg can to some extent reverse anticoagulation in patients receiving NOACs. The current, limited data support use of reversal agent PCC for rivaroxaban and apixaban (no human studies for apixaban) and use of aPCC for dabigatran.^3,6,8 Activated charcoal can be used for patients who have taken dabigatran <6 hours before presentation.³ Hemodialysis is another option for dabigatran removal. Hemodialysis, however, takes 4 to 6 hours or longer to remove about 60% of the medication (Table 2).^3,5

In major orthopedic surgeries, such as TJA, bleeding is a critical concern. Using reversal agents to overcome the anticoagulation effect adds to the potential concern for thromboembolism secondary to these agents. Therefore, in cases in which surgery cannot be delayed any longer, the decision to use reversal agents should be made on a case-by-case basis. For most patients on rivaroxaban or apixaban, it is sufficient to delay for 24 to 48 hours before proceeding safely with surgery; for dabigatran, a delay of 3 to 4 days is recommended. Delay before surgery may need to be extended for the elderly and for patients with renal failure. The pharmacokinetics of these medications is summarized in Table 1.

There are no guidelines for perioperative management of patients undergoing elective, urgent, or emergent surgeries while on NOACs. As discussed, Pernod and colleagues6 proposed better perioperative management of major bleeding risks in patients receiving rivaroxaban or dabigatran. Adapting their approach, and using the data available from the medical literature, we propose a perioperative algorithm that can guide practicing orthopedic surgeons performing urgent and emergent surgeries (Figure).

The population of patients receiving chronic anticoagulation therapy is growing, and anticoagulant and antiplatelet options are increasing in the United States and around the world. We propose a team approach for patient care, with orthopedic surgeon and cardiologist or vascular medicine specialist collaborating to ensure the safety and effectiveness of this treatment.

Chronic anticoagulation is a common preex­isting condition in patients undergoing total joint arthroplasty (TJA). Atrial fibrillation (AF), the most common underlying disorder requiring chronic anticoagulation, affects more than 3 million patients in the United States—a number that is projected to increase to 16 million by 2050.^1,2 Other common indications for anticoagulation are deep vein thrombosis (DVT) treatment, presence of a prosthetic heart valve, and venous thromboembolism (VTE) prevention after hip or knee arthroplasty. These patients face the additional risks of hemorrhage, persistent wound drainage, hematoma formation, transfusion requirements, periprosthetic joint infection, and longer hospital stay.¹ Chronic anticoagulation traditionally has been managed with warfarin, which inhibits production of the vitamin K–dependent clotting factors II, VII, IX, and X. However, the new novel oral anticoagulants (NOACs), which target individual factors in the clotting cascade, are gaining favor as chronic anticoagulant agents because of their ease of use and improved efficacy and safety. These agents include the factor IIA inhibitor dabigatran (Pradaxa) and the direct factor Xa inhibitors rivaroxaban (Xarelto) and apixaban (Eliquis).

Management of patients at risk for thromboembolism and bleeding issues, particularly within the context of elective, urgent, or emergent orthopedic surgeries, is an evolving area. Understanding the pharmacokinetics, conventional laboratory tests, dosing, and reversal methods for NOACs is important, especially because clinical data are limited and the treatment itself can cause clinically significant harm.

In this article, we review the medical literature on these medications, their mechanism of action, and their reversal agents, and outline a practical approach for managing patients during the perioperative period.

Dabigatran

In October 2010, dabigatran became the first NOAC approved by the US Food and Drug Administration (FDA) for the prevention of arterial thromboembolic events in patients with nonvalvular AF, on the basis of the results of the RELY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial. Dabigatran is an oral factor IIA (thrombin) inhibitor. From time of ingestion, dabigatran takes 1.25 to 3 hours to reach peak plasma concentration. It has a half-life of 12 to 14 hours, is excreted predominantly by the kidneys (80%), and is renally dosed. The usual dose is 150 mg 2 times daily if creatinine clearance (CrCl) is >30 mL/minute, or 75 mg 2 times daily if CrCl is 15 to 30 mL/minute.³ Dabigatran is not recommended for patients with CrCl <15 mL/minute.

Dabigatran affects prothrombin time (PT), activated partial thromboplastin time (aPTT), ecarin clotting time, and thrombin time, with the latter 2 providing the most accurate means of monitoring appropriate drug levels.^3,4 Of the tests commonly used to assess coagulation hemostasis in hospitals, normalization of thrombin time and aPTT provide the most accurate results (Table 1). The pharmacokinetics of dabigatran mandate consideration of dose, time of ingestion relative to time of blood sampling, and renal function in the assessment of coagulation hemostasis.

For elective surgeries, the periprocedure recommendation for patients being treated with dabigatran is to discontinue the medication 3 to 4 days before an operation if CrCl is ≥50 mL/minute, or 4 to 5 days beforehand if CrCl is <50 mL/minute.³ There is no antidote for dabigatran. In an in vitro model, activated charcoal reduced 99.9% of dabigatran absorption after recent ingestion.³ According to case reports, acute hemodialysis successfully removed 60% of the medication after 6 hours.⁵ In patients with end-stage renal disease, hemodialysis removed up to 68% of active dabigatran after 4 hours.³

Pernod and colleagues6 proposed that urgent surgeries can proceed if the concentration of dabigatran is ≤30 ng/mL—equivalent to normal aPTT. Their dictum was extrapolated from the data of patients who underwent elective surgeries while being treated with dabigatran, as recorded during the RELY trial. According to Pernod and colleagues,⁶ if aPTT is increased (probable drug level, ≥30 ng/mL), surgery should be postponed for up to 12 hours, with aPTT checked again and the process repeated if the concentration of dabigatran is still elevated and surgery can continue to be delayed. In patients who require urgent surgical interventions, we previously utilized nanofiltered activated prothrombin complex concentrate (aPCC; Feiba NF) 30 to 50 IU/kg over prothrombin complex concentrate (PCC; Kcentra or Bebulin) 25 to 50 IU/kg, as supported by in vitro and animal model studies and anecdotal case reports. However, neither aPCC nor PCC fully corrects the abnormalities evident on hemostasis tests.3,6 In October 2015, the FDA approved Idarucizumab (Praxbind), an injectable monoclonal antibody fragment that binds to dabigatran, as a reversing agent for use in urgent/emergent settings. Recommendation is to administer two 50-ml bolus infusions, each containing 2.5 g of idarucizumab, no more than 15 minutes apart.⁷ Additionally, hemodialysis could be discussed before surgery, with the understanding that it will take a long time to reach the threshold of 30 ng/mL in these patients (Table 2).

Rivaroxaban

Rivaroxaban is an oral direct factor Xa inhibitor that was initially approved in November 2011 for the prevention of stroke and systemic embolism in patients with nonvalvular AF. Since then, clinical use of rivaroxaban has been expanded to include prevention of VTE after elective hip or knee arthroplasty as well as treatment of DVT and prevention of recurrent VTE after acute DVT. In the phase 3 ROCKET AF (Rivaroxaban Once-Daily Oral Direct Factor Xa Inhibition Compared With Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation) study, rivaroxaban 20 mg daily (CrCl, ≥50 mL/min) and rivaroxaban 15 mg daily (CrCl, 15-49 mL/min) were equally effective as warfarin. Compared with warfarin, rivaroxaban had a similar safety rate for bleeding and adverse events but fewer intracranial hemorrhage and fatal bleeding events.⁸ On the basis of the outcomes of the RECORD (Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Venous Thrombosis and Pulmonary Embolism) studies comparing rivaroxaban and enoxaparin sodium, rivaroxaban 10 mg daily was approved for the prevention of VTE and pulmonary embolism after elective hip or knee arthroplasty.⁸

The half-life of rivaroxaban is 5 to 9 hours in the young and 11 to 13 hours in the elderly.⁸ As rivaroxaban takes 2 to 4 hours after ingestion to reach peak plasma concentration, it is important to know the timing and the dose taken. Because of the short half-life and rapid onset of action of this medication, bridging with another anticoagulant is not required when rivaroxaban is discontinued before surgery or initiated after surgery.⁸ The recommendation is to withhold rivaroxaban for 24 to 48 hours before surgery and then to administer the first postoperative dose 6 to 10 hours after surgery, or when hemostasis is achieved (Table 1).

PT is recommended for rivaroxaban detection. Conventional assays are not sensitive at low concentrations, and degree of prolongation does not reliably predict amount of medication present.^3,9 However, normal PT corresponds to a drug concentration of about 30 ng/mL and is considered safe for patients undergoing surgical intervention without increased risk for bleeding.⁶ This recommendation was extrapolated from data in the ROCKET AF study of patients who underwent elective surgeries while on rivaroxaban.⁶ Commercially available chromogenic anti–factor Xa assays, used with a rivaroxaban calibration curve, are sensitive and specific for rivaroxaban plasma concentrations.^3,8 However, these assays are not widely available.

If a bleeding complication occurs in a patient who is being treated with rivaroxaban, the next rivaroxaban dose should be delayed, or treatment should be discontinued, as appropriate.⁸ Urgency of surgery should be weighed against risk for bleeding complications on a case-by-case basis. This decision is deferred to the clinical judgment of the surgeon. In the case of a patient with severe, life-threatening bleeding or a patient who requires emergent surgery, PCC 25-50 IU/kg is the recommended reversal agent.⁹ Recombinant factor VIIa and aPCC have been used in experimental settings, but there is concern about the greater prothrombotic potential of these agents compared with PCC⁸ (Table 2).

Apixaban

Apixaban is the second factor Xa inhibitor introduced in the United States and the first to show—in the ARISTOTLE (Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation) study—efficacy superior to that of warfarin for the prevention of stroke and systemic embolism, all-cause mortality, and major bleeding. Furthermore, in the AVERROES (Apixaban Versus Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin K Antagonist Treatment) study, apixaban used in AF patients who were deemed not suitable for warfarin proved to be more effective than aspirin for stroke prevention, and had a similar rate of major bleeding.¹⁰ Apixaban is administered in a 5-mg dose 2 times daily. It has a half-life of 10 to 14 hours, is highly protein-bound, and has predominantly fecal excretion (27% is renal). Apixaban can prolong PT, but the correlation is nonlinear. Barrett and colleagues¹¹ found that chromogenic anti–factor Xa assays provided the most accurate readings of apixaban plasma concentrations. Normal anti–factor Xa activity in patients being treated with apixaban suggests low drug levels and an intact hemostatic function, which are indicators of low bleeding risk with surgical intervention³ (Table 1).

Similar to other NOACs, apixaban has no antidote. In vitro testing showed that PCC improved thrombin generation when added to the blood of healthy donors who had received apixaban. Despite the lack of clinical experience, use of PCC 50 IU/kg may be reasonable for apixaban patients with severe or life-threatening bleeding³ (Table 2). Unlike dabigatran, apixaban cannot be eliminated with dialysis because of its high degree of protein binding. In nonemergent circumstances, delaying surgery 24 to 48 hours is considered effective in reducing the concentration of apixaban to a range that does not cause additional risk for bleeding.

Conclusion

Compared with warfarin, the NOACs dabigatran, rivaroxaban, and apixaban are efficacious and safe. Because of their steady pharmacokinetics, they do not require regular coagulation testing, as is the case with warfarin. These NOACs have been approved for the prevention of stroke and thromboembolic events in patients with nonvalvular AF; rivaroxaban has also been approved for VTE prevention after total hip or knee arthroplasty, for DVT treatment, and for prevention of recurrent VTE after acute DVT. Other options for VTE prophylaxis after hip and knee surgery are addressed in the guidelines issued by the American Academy of Orthopaedic Surgeons in 2011.¹² As the incidence of chronic anticoagulation continues to increase among patients undergoing TJA, orthopedic surgeons need to be aware of the mechanism of action of these NOACs, as well as their pharmacokinetics and available reversal agents. Aggarwal and colleagues1 found that AF patients undergoing TJA had longer hospital stays, increased transfusion requirements, and increased risk for periprosthetic joint infection and unplanned hospital readmission.

The anticoagulation tests recommended for evaluation of hemostasis and drug reversal are normalization of aPTT for dabigatran; PT for rivaroxaban; and chromogenic anti–factor Xa activity for apixaban³ (Table 2). Although several research projects are being planned to develop an antidote for these medications, no antidote has been approved for human trials. The coagulation agents currently being used for reversal of NOACs are nonactivated PCC (Kcentra, Bebulin) and aPCC. Kcentra is a 4-factor PCC (II, VII, IX, X), and Bebulin is a 3-factor PCC (II, IX, X). Most authors recommend using 4-factor PCC 25 to 50 IU/kg. In vivo studies and animal studies have shown that nanofiltered aPCC (Feiba NF) at doses of 30 to 50 IU/kg can to some extent reverse anticoagulation in patients receiving NOACs. The current, limited data support use of reversal agent PCC for rivaroxaban and apixaban (no human studies for apixaban) and use of aPCC for dabigatran.^3,6,8 Activated charcoal can be used for patients who have taken dabigatran <6 hours before presentation.³ Hemodialysis is another option for dabigatran removal. Hemodialysis, however, takes 4 to 6 hours or longer to remove about 60% of the medication (Table 2).^3,5

In major orthopedic surgeries, such as TJA, bleeding is a critical concern. Using reversal agents to overcome the anticoagulation effect adds to the potential concern for thromboembolism secondary to these agents. Therefore, in cases in which surgery cannot be delayed any longer, the decision to use reversal agents should be made on a case-by-case basis. For most patients on rivaroxaban or apixaban, it is sufficient to delay for 24 to 48 hours before proceeding safely with surgery; for dabigatran, a delay of 3 to 4 days is recommended. Delay before surgery may need to be extended for the elderly and for patients with renal failure. The pharmacokinetics of these medications is summarized in Table 1.

There are no guidelines for perioperative management of patients undergoing elective, urgent, or emergent surgeries while on NOACs. As discussed, Pernod and colleagues6 proposed better perioperative management of major bleeding risks in patients receiving rivaroxaban or dabigatran. Adapting their approach, and using the data available from the medical literature, we propose a perioperative algorithm that can guide practicing orthopedic surgeons performing urgent and emergent surgeries (Figure).

The population of patients receiving chronic anticoagulation therapy is growing, and anticoagulant and antiplatelet options are increasing in the United States and around the world. We propose a team approach for patient care, with orthopedic surgeon and cardiologist or vascular medicine specialist collaborating to ensure the safety and effectiveness of this treatment.

Chronic anticoagulation is a common preex­isting condition in patients undergoing total joint arthroplasty (TJA). Atrial fibrillation (AF), the most common underlying disorder requiring chronic anticoagulation, affects more than 3 million patients in the United States—a number that is projected to increase to 16 million by 2050.^1,2 Other common indications for anticoagulation are deep vein thrombosis (DVT) treatment, presence of a prosthetic heart valve, and venous thromboembolism (VTE) prevention after hip or knee arthroplasty. These patients face the additional risks of hemorrhage, persistent wound drainage, hematoma formation, transfusion requirements, periprosthetic joint infection, and longer hospital stay.¹ Chronic anticoagulation traditionally has been managed with warfarin, which inhibits production of the vitamin K–dependent clotting factors II, VII, IX, and X. However, the new novel oral anticoagulants (NOACs), which target individual factors in the clotting cascade, are gaining favor as chronic anticoagulant agents because of their ease of use and improved efficacy and safety. These agents include the factor IIA inhibitor dabigatran (Pradaxa) and the direct factor Xa inhibitors rivaroxaban (Xarelto) and apixaban (Eliquis).

Management of patients at risk for thromboembolism and bleeding issues, particularly within the context of elective, urgent, or emergent orthopedic surgeries, is an evolving area. Understanding the pharmacokinetics, conventional laboratory tests, dosing, and reversal methods for NOACs is important, especially because clinical data are limited and the treatment itself can cause clinically significant harm.

In this article, we review the medical literature on these medications, their mechanism of action, and their reversal agents, and outline a practical approach for managing patients during the perioperative period.

Dabigatran

In October 2010, dabigatran became the first NOAC approved by the US Food and Drug Administration (FDA) for the prevention of arterial thromboembolic events in patients with nonvalvular AF, on the basis of the results of the RELY (Randomized Evaluation of Long-Term Anticoagulation Therapy) trial. Dabigatran is an oral factor IIA (thrombin) inhibitor. From time of ingestion, dabigatran takes 1.25 to 3 hours to reach peak plasma concentration. It has a half-life of 12 to 14 hours, is excreted predominantly by the kidneys (80%), and is renally dosed. The usual dose is 150 mg 2 times daily if creatinine clearance (CrCl) is >30 mL/minute, or 75 mg 2 times daily if CrCl is 15 to 30 mL/minute.³ Dabigatran is not recommended for patients with CrCl <15 mL/minute.

Dabigatran affects prothrombin time (PT), activated partial thromboplastin time (aPTT), ecarin clotting time, and thrombin time, with the latter 2 providing the most accurate means of monitoring appropriate drug levels.^3,4 Of the tests commonly used to assess coagulation hemostasis in hospitals, normalization of thrombin time and aPTT provide the most accurate results (Table 1). The pharmacokinetics of dabigatran mandate consideration of dose, time of ingestion relative to time of blood sampling, and renal function in the assessment of coagulation hemostasis.

For elective surgeries, the periprocedure recommendation for patients being treated with dabigatran is to discontinue the medication 3 to 4 days before an operation if CrCl is ≥50 mL/minute, or 4 to 5 days beforehand if CrCl is <50 mL/minute.³ There is no antidote for dabigatran. In an in vitro model, activated charcoal reduced 99.9% of dabigatran absorption after recent ingestion.³ According to case reports, acute hemodialysis successfully removed 60% of the medication after 6 hours.⁵ In patients with end-stage renal disease, hemodialysis removed up to 68% of active dabigatran after 4 hours.³

Pernod and colleagues6 proposed that urgent surgeries can proceed if the concentration of dabigatran is ≤30 ng/mL—equivalent to normal aPTT. Their dictum was extrapolated from the data of patients who underwent elective surgeries while being treated with dabigatran, as recorded during the RELY trial. According to Pernod and colleagues,⁶ if aPTT is increased (probable drug level, ≥30 ng/mL), surgery should be postponed for up to 12 hours, with aPTT checked again and the process repeated if the concentration of dabigatran is still elevated and surgery can continue to be delayed. In patients who require urgent surgical interventions, we previously utilized nanofiltered activated prothrombin complex concentrate (aPCC; Feiba NF) 30 to 50 IU/kg over prothrombin complex concentrate (PCC; Kcentra or Bebulin) 25 to 50 IU/kg, as supported by in vitro and animal model studies and anecdotal case reports. However, neither aPCC nor PCC fully corrects the abnormalities evident on hemostasis tests.3,6 In October 2015, the FDA approved Idarucizumab (Praxbind), an injectable monoclonal antibody fragment that binds to dabigatran, as a reversing agent for use in urgent/emergent settings. Recommendation is to administer two 50-ml bolus infusions, each containing 2.5 g of idarucizumab, no more than 15 minutes apart.⁷ Additionally, hemodialysis could be discussed before surgery, with the understanding that it will take a long time to reach the threshold of 30 ng/mL in these patients (Table 2).

Rivaroxaban

Rivaroxaban is an oral direct factor Xa inhibitor that was initially approved in November 2011 for the prevention of stroke and systemic embolism in patients with nonvalvular AF. Since then, clinical use of rivaroxaban has been expanded to include prevention of VTE after elective hip or knee arthroplasty as well as treatment of DVT and prevention of recurrent VTE after acute DVT. In the phase 3 ROCKET AF (Rivaroxaban Once-Daily Oral Direct Factor Xa Inhibition Compared With Vitamin K Antagonism for Prevention of Stroke and Embolism Trial in Atrial Fibrillation) study, rivaroxaban 20 mg daily (CrCl, ≥50 mL/min) and rivaroxaban 15 mg daily (CrCl, 15-49 mL/min) were equally effective as warfarin. Compared with warfarin, rivaroxaban had a similar safety rate for bleeding and adverse events but fewer intracranial hemorrhage and fatal bleeding events.⁸ On the basis of the outcomes of the RECORD (Regulation of Coagulation in Orthopedic Surgery to Prevent Deep Venous Thrombosis and Pulmonary Embolism) studies comparing rivaroxaban and enoxaparin sodium, rivaroxaban 10 mg daily was approved for the prevention of VTE and pulmonary embolism after elective hip or knee arthroplasty.⁸

The half-life of rivaroxaban is 5 to 9 hours in the young and 11 to 13 hours in the elderly.⁸ As rivaroxaban takes 2 to 4 hours after ingestion to reach peak plasma concentration, it is important to know the timing and the dose taken. Because of the short half-life and rapid onset of action of this medication, bridging with another anticoagulant is not required when rivaroxaban is discontinued before surgery or initiated after surgery.⁸ The recommendation is to withhold rivaroxaban for 24 to 48 hours before surgery and then to administer the first postoperative dose 6 to 10 hours after surgery, or when hemostasis is achieved (Table 1).

PT is recommended for rivaroxaban detection. Conventional assays are not sensitive at low concentrations, and degree of prolongation does not reliably predict amount of medication present.^3,9 However, normal PT corresponds to a drug concentration of about 30 ng/mL and is considered safe for patients undergoing surgical intervention without increased risk for bleeding.⁶ This recommendation was extrapolated from data in the ROCKET AF study of patients who underwent elective surgeries while on rivaroxaban.⁶ Commercially available chromogenic anti–factor Xa assays, used with a rivaroxaban calibration curve, are sensitive and specific for rivaroxaban plasma concentrations.^3,8 However, these assays are not widely available.

If a bleeding complication occurs in a patient who is being treated with rivaroxaban, the next rivaroxaban dose should be delayed, or treatment should be discontinued, as appropriate.⁸ Urgency of surgery should be weighed against risk for bleeding complications on a case-by-case basis. This decision is deferred to the clinical judgment of the surgeon. In the case of a patient with severe, life-threatening bleeding or a patient who requires emergent surgery, PCC 25-50 IU/kg is the recommended reversal agent.⁹ Recombinant factor VIIa and aPCC have been used in experimental settings, but there is concern about the greater prothrombotic potential of these agents compared with PCC⁸ (Table 2).

Apixaban

Apixaban is the second factor Xa inhibitor introduced in the United States and the first to show—in the ARISTOTLE (Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation) study—efficacy superior to that of warfarin for the prevention of stroke and systemic embolism, all-cause mortality, and major bleeding. Furthermore, in the AVERROES (Apixaban Versus Acetylsalicylic Acid to Prevent Stroke in Atrial Fibrillation Patients Who Have Failed or Are Unsuitable for Vitamin K Antagonist Treatment) study, apixaban used in AF patients who were deemed not suitable for warfarin proved to be more effective than aspirin for stroke prevention, and had a similar rate of major bleeding.¹⁰ Apixaban is administered in a 5-mg dose 2 times daily. It has a half-life of 10 to 14 hours, is highly protein-bound, and has predominantly fecal excretion (27% is renal). Apixaban can prolong PT, but the correlation is nonlinear. Barrett and colleagues¹¹ found that chromogenic anti–factor Xa assays provided the most accurate readings of apixaban plasma concentrations. Normal anti–factor Xa activity in patients being treated with apixaban suggests low drug levels and an intact hemostatic function, which are indicators of low bleeding risk with surgical intervention³ (Table 1).

Similar to other NOACs, apixaban has no antidote. In vitro testing showed that PCC improved thrombin generation when added to the blood of healthy donors who had received apixaban. Despite the lack of clinical experience, use of PCC 50 IU/kg may be reasonable for apixaban patients with severe or life-threatening bleeding³ (Table 2). Unlike dabigatran, apixaban cannot be eliminated with dialysis because of its high degree of protein binding. In nonemergent circumstances, delaying surgery 24 to 48 hours is considered effective in reducing the concentration of apixaban to a range that does not cause additional risk for bleeding.

Conclusion

Compared with warfarin, the NOACs dabigatran, rivaroxaban, and apixaban are efficacious and safe. Because of their steady pharmacokinetics, they do not require regular coagulation testing, as is the case with warfarin. These NOACs have been approved for the prevention of stroke and thromboembolic events in patients with nonvalvular AF; rivaroxaban has also been approved for VTE prevention after total hip or knee arthroplasty, for DVT treatment, and for prevention of recurrent VTE after acute DVT. Other options for VTE prophylaxis after hip and knee surgery are addressed in the guidelines issued by the American Academy of Orthopaedic Surgeons in 2011.¹² As the incidence of chronic anticoagulation continues to increase among patients undergoing TJA, orthopedic surgeons need to be aware of the mechanism of action of these NOACs, as well as their pharmacokinetics and available reversal agents. Aggarwal and colleagues1 found that AF patients undergoing TJA had longer hospital stays, increased transfusion requirements, and increased risk for periprosthetic joint infection and unplanned hospital readmission.

The anticoagulation tests recommended for evaluation of hemostasis and drug reversal are normalization of aPTT for dabigatran; PT for rivaroxaban; and chromogenic anti–factor Xa activity for apixaban³ (Table 2). Although several research projects are being planned to develop an antidote for these medications, no antidote has been approved for human trials. The coagulation agents currently being used for reversal of NOACs are nonactivated PCC (Kcentra, Bebulin) and aPCC. Kcentra is a 4-factor PCC (II, VII, IX, X), and Bebulin is a 3-factor PCC (II, IX, X). Most authors recommend using 4-factor PCC 25 to 50 IU/kg. In vivo studies and animal studies have shown that nanofiltered aPCC (Feiba NF) at doses of 30 to 50 IU/kg can to some extent reverse anticoagulation in patients receiving NOACs. The current, limited data support use of reversal agent PCC for rivaroxaban and apixaban (no human studies for apixaban) and use of aPCC for dabigatran.^3,6,8 Activated charcoal can be used for patients who have taken dabigatran <6 hours before presentation.³ Hemodialysis is another option for dabigatran removal. Hemodialysis, however, takes 4 to 6 hours or longer to remove about 60% of the medication (Table 2).^3,5

In major orthopedic surgeries, such as TJA, bleeding is a critical concern. Using reversal agents to overcome the anticoagulation effect adds to the potential concern for thromboembolism secondary to these agents. Therefore, in cases in which surgery cannot be delayed any longer, the decision to use reversal agents should be made on a case-by-case basis. For most patients on rivaroxaban or apixaban, it is sufficient to delay for 24 to 48 hours before proceeding safely with surgery; for dabigatran, a delay of 3 to 4 days is recommended. Delay before surgery may need to be extended for the elderly and for patients with renal failure. The pharmacokinetics of these medications is summarized in Table 1.

There are no guidelines for perioperative management of patients undergoing elective, urgent, or emergent surgeries while on NOACs. As discussed, Pernod and colleagues6 proposed better perioperative management of major bleeding risks in patients receiving rivaroxaban or dabigatran. Adapting their approach, and using the data available from the medical literature, we propose a perioperative algorithm that can guide practicing orthopedic surgeons performing urgent and emergent surgeries (Figure).

The population of patients receiving chronic anticoagulation therapy is growing, and anticoagulant and antiplatelet options are increasing in the United States and around the world. We propose a team approach for patient care, with orthopedic surgeon and cardiologist or vascular medicine specialist collaborating to ensure the safety and effectiveness of this treatment.

Total hip arthroplasty (THA) is an effective treatment for advanced hip arthritis from a variety of causes, including osteoarthritis, inflammatory arthritis, posttraumatic arthritis, and sequelae of developmental disorders. It is not uncommon to perform THA in the presence of a previous proximal femoral osteotomy that may have been performed for slipped capital femoral epiphysis (SCFE), Legg-Calvé-Perthes disease, or developmental dysplasia of the hip, among other conditions. These osteotomies are commonly combined with internal fixation, a plate-and-screw device. These patients are at risk for developing degenerative arthritis at an earlier age than patients with other types of arthritis and subsequently may undergo THA at a younger age.^1-3 Presence of a plate can pose a technical challenge during THA surgery. THA performed after intertrochanteric osteotomy has higher rates of perioperative and postoperative complications.4 Ferguson and colleagues4 noted difficulty during hardware removal in 24% of cases. Among the complications encountered were broken hardware, stripped screws, greater trochanteric fracture, stress risers from previous screw holes, canal narrowing from endosteal hypertrophy around hardware, and lateral cortical deficiency after removal of the side plate. As intertrochanteric osteotomies are often performed in patients who have yet to reach skeletal maturity, cortical hypertrophy can lead to complete coverage of the side plate and an “intracortical” position.

This article reports on 2 THA cases in which a technique was used to avoid intracortical plate removal and the resulting problems of lateral cortical deficiency. During each THA, the plate was left in place to avoid compromise of the lateral femoral cortex. The patients provided written informed consent for print and electronic publication of these case reports.

Case Reports

Case 1

An adolescent with bilateral SCFE was treated first with internal fixation of the right hip and subsequently with left proximal femoral osteotomy with internal fixation. He did well until age 31 years, when he developed progressively worsening pain about the left hip. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the left hip. Radiographs showed a sliding hip screw in place, with proximal femoral deformity consisting of femoral neck shortening and posterior angulation (Figures 1A, 1B). Preoperative Harris Hip Score was 54.5.

Case 2

A 51-year-old woman presented with a history of right hip problems dating back to age 13 years, when she sustained a fracture of the right hip and was treated with internal fixation. At age 15 years, she underwent proximal femoral osteotomy to correct residual deformity. She did well until age 45 years, when she developed worsening hip symptoms. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the right hip. Radiographs showed a fixed-angle blade plate in the proximal femur, with significant proximal femoral deformity (Figures 1C, 1D). Preoperative Harris Hip Score was 53.6.

Surgical Technique

In both cases, a standard series of radiographs was obtained—an anteroposterior (AP) radiograph of the pelvis and AP and cross-table lateral radiographs of the operative hip (Figure 1). Computed tomography (CT) with a metal-artifact-reducing technique may be useful in determining amount of cortical bone remaining under the plate. CT showed limited lateral cortex beneath the side plate and bony overgrowth covering the side plate. Preoperative templating was performed using previously described techniques.⁵

During THA, before removing any portion of any retained hardware, the surgeon should perform 3 important actions: Dislocate the hip, perform all appropriate capsular releases, and reduce the hip. Dislocating the hip before hardware removal significantly decreases the risk for fracture caused by stress risers, as the force required for dislocation is much more controlled because of the capsular releases. After hardware removal, the hip can be easily redislocated, and the femoral neck osteotomy can be performed.

When plate and screws are in an intracortical position, the screws can be removed only after removing the small shell of cortical bone covering them. The amount of bone to be removed is minimal. After the screws are removed, the plate remains in place. A motorized device with a metal-cutting attachment is used to transect the construct at the junction of the plate and barrel (case 1) or at the bend of a fixed-angle device (case 2). Laparotomy sponges are placed around the proximal femur to minimize the amount of soft tissue that could be exposed to metal shavings. Copious irrigation is used throughout this part of the procedure. Osteotomes are used to elevate the proximal portion of the plate and the barrel, preserving the distal portion of the plate on the lateral cortex of the femoral shaft.

After the head is removed, the rest of the THA can be performed using standard press-fit insertion technique (Figures 2A-2D). Care must be taken to ensure that the distal aspect of the femoral stem bypasses the most distal screw hole by at least 2 cortical diameters in order to reduce the risk for periprosthetic fracture.

By 2-year follow-up, both patients had regained excellent range of motion, ambulation, and overall function. Postoperative Harris Hip Scores were 86.6 and 83.8, respectively. There were no radiographic signs of complications.

Discussion

THA can be challenging in the setting of previously placed internal fixation devices, particularly devices inserted during a patient’s adolescence, as significant bony overgrowth can occur. The standard approach has been to remove the internal fixation device and then perform the THA. In most cases, and particularly when the internal fixation device is in an intracortical position, the result is significant compromise of bone. This article describes a technique in which a portion of the hardware is retained to avoid compromise of the lateral femoral cortex, thereby allowing insertion of a noncemented femoral component.

THA is the most effective procedure for reducing hip pain and disability in the setting of degenerative changes.6 Patients with SCFE, Legg-Calvé-Perthes disease, or developmental dysplasia of the hip generally are younger at the time they may be sufficiently symptomatic to consider THA^.7,8 Many have had previous surgery using internal fixation devices. THAs after previous osteotomies with internal fixation devices are more technically demanding, require more operative time, are subject to more blood loss, and have a higher rate of complications, including femoral fracture. Ferguson and colleagues⁴ and Boos and colleagues9 found these surgeries were more difficult 33.8% and 36.8% of the time, respectively. For these reasons, some authors have recommended removing the internal fixation device as soon as the osteotomy is healed.⁴ However, this has not become the standard of care, and surgeons continue to perform THAs in the presence of a previous osteotomy with an internal fixation device in place.

The technique described in this article was used successfully in 2 cases. In each case, leaving the intracortical plate in place avoided compromise of the lateral femoral cortex and allowed insertion of a noncemented femoral component without complication. Of course, with the screw holes representing stress risers, careful insertion of the femoral component was required. Retaining the intracortical plate allowed it to function as part of the lateral femoral cortex, thereby maintaining the structural integrity of the femoral canal. As has been described for the 2 cases, a blade plate and plate and barrel were converted to a limited intracortical plate by removing the proximal portion of the plates—a modification that could be applied to other types of internal fixation devices that extend into the femoral neck as long as appropriate cutting tools are available.

Conclusion

THA in the setting of a retained internal fixation device is relatively common. This article describes a technique that can be used when a plate applied to the lateral femoral cortex has become intracortical as a result of extensive bony overgrowth. In using this technique to avoid plate removal, the surgeon eliminates the need for more extensive procedures aimed at compensating for deficiency of the femoral cortex in the area of plate removal. Although only 2 cases are presented here, this technique potentially can be used more broadly in these specific clinical situations.

Total hip arthroplasty (THA) is an effective treatment for advanced hip arthritis from a variety of causes, including osteoarthritis, inflammatory arthritis, posttraumatic arthritis, and sequelae of developmental disorders. It is not uncommon to perform THA in the presence of a previous proximal femoral osteotomy that may have been performed for slipped capital femoral epiphysis (SCFE), Legg-Calvé-Perthes disease, or developmental dysplasia of the hip, among other conditions. These osteotomies are commonly combined with internal fixation, a plate-and-screw device. These patients are at risk for developing degenerative arthritis at an earlier age than patients with other types of arthritis and subsequently may undergo THA at a younger age.^1-3 Presence of a plate can pose a technical challenge during THA surgery. THA performed after intertrochanteric osteotomy has higher rates of perioperative and postoperative complications.4 Ferguson and colleagues4 noted difficulty during hardware removal in 24% of cases. Among the complications encountered were broken hardware, stripped screws, greater trochanteric fracture, stress risers from previous screw holes, canal narrowing from endosteal hypertrophy around hardware, and lateral cortical deficiency after removal of the side plate. As intertrochanteric osteotomies are often performed in patients who have yet to reach skeletal maturity, cortical hypertrophy can lead to complete coverage of the side plate and an “intracortical” position.

This article reports on 2 THA cases in which a technique was used to avoid intracortical plate removal and the resulting problems of lateral cortical deficiency. During each THA, the plate was left in place to avoid compromise of the lateral femoral cortex. The patients provided written informed consent for print and electronic publication of these case reports.

Case Reports

Case 1

An adolescent with bilateral SCFE was treated first with internal fixation of the right hip and subsequently with left proximal femoral osteotomy with internal fixation. He did well until age 31 years, when he developed progressively worsening pain about the left hip. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the left hip. Radiographs showed a sliding hip screw in place, with proximal femoral deformity consisting of femoral neck shortening and posterior angulation (Figures 1A, 1B). Preoperative Harris Hip Score was 54.5.

Case 2

A 51-year-old woman presented with a history of right hip problems dating back to age 13 years, when she sustained a fracture of the right hip and was treated with internal fixation. At age 15 years, she underwent proximal femoral osteotomy to correct residual deformity. She did well until age 45 years, when she developed worsening hip symptoms. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the right hip. Radiographs showed a fixed-angle blade plate in the proximal femur, with significant proximal femoral deformity (Figures 1C, 1D). Preoperative Harris Hip Score was 53.6.

Surgical Technique

In both cases, a standard series of radiographs was obtained—an anteroposterior (AP) radiograph of the pelvis and AP and cross-table lateral radiographs of the operative hip (Figure 1). Computed tomography (CT) with a metal-artifact-reducing technique may be useful in determining amount of cortical bone remaining under the plate. CT showed limited lateral cortex beneath the side plate and bony overgrowth covering the side plate. Preoperative templating was performed using previously described techniques.⁵

During THA, before removing any portion of any retained hardware, the surgeon should perform 3 important actions: Dislocate the hip, perform all appropriate capsular releases, and reduce the hip. Dislocating the hip before hardware removal significantly decreases the risk for fracture caused by stress risers, as the force required for dislocation is much more controlled because of the capsular releases. After hardware removal, the hip can be easily redislocated, and the femoral neck osteotomy can be performed.

When plate and screws are in an intracortical position, the screws can be removed only after removing the small shell of cortical bone covering them. The amount of bone to be removed is minimal. After the screws are removed, the plate remains in place. A motorized device with a metal-cutting attachment is used to transect the construct at the junction of the plate and barrel (case 1) or at the bend of a fixed-angle device (case 2). Laparotomy sponges are placed around the proximal femur to minimize the amount of soft tissue that could be exposed to metal shavings. Copious irrigation is used throughout this part of the procedure. Osteotomes are used to elevate the proximal portion of the plate and the barrel, preserving the distal portion of the plate on the lateral cortex of the femoral shaft.

After the head is removed, the rest of the THA can be performed using standard press-fit insertion technique (Figures 2A-2D). Care must be taken to ensure that the distal aspect of the femoral stem bypasses the most distal screw hole by at least 2 cortical diameters in order to reduce the risk for periprosthetic fracture.

By 2-year follow-up, both patients had regained excellent range of motion, ambulation, and overall function. Postoperative Harris Hip Scores were 86.6 and 83.8, respectively. There were no radiographic signs of complications.

Discussion

THA can be challenging in the setting of previously placed internal fixation devices, particularly devices inserted during a patient’s adolescence, as significant bony overgrowth can occur. The standard approach has been to remove the internal fixation device and then perform the THA. In most cases, and particularly when the internal fixation device is in an intracortical position, the result is significant compromise of bone. This article describes a technique in which a portion of the hardware is retained to avoid compromise of the lateral femoral cortex, thereby allowing insertion of a noncemented femoral component.

THA is the most effective procedure for reducing hip pain and disability in the setting of degenerative changes.6 Patients with SCFE, Legg-Calvé-Perthes disease, or developmental dysplasia of the hip generally are younger at the time they may be sufficiently symptomatic to consider THA^.7,8 Many have had previous surgery using internal fixation devices. THAs after previous osteotomies with internal fixation devices are more technically demanding, require more operative time, are subject to more blood loss, and have a higher rate of complications, including femoral fracture. Ferguson and colleagues⁴ and Boos and colleagues9 found these surgeries were more difficult 33.8% and 36.8% of the time, respectively. For these reasons, some authors have recommended removing the internal fixation device as soon as the osteotomy is healed.⁴ However, this has not become the standard of care, and surgeons continue to perform THAs in the presence of a previous osteotomy with an internal fixation device in place.

The technique described in this article was used successfully in 2 cases. In each case, leaving the intracortical plate in place avoided compromise of the lateral femoral cortex and allowed insertion of a noncemented femoral component without complication. Of course, with the screw holes representing stress risers, careful insertion of the femoral component was required. Retaining the intracortical plate allowed it to function as part of the lateral femoral cortex, thereby maintaining the structural integrity of the femoral canal. As has been described for the 2 cases, a blade plate and plate and barrel were converted to a limited intracortical plate by removing the proximal portion of the plates—a modification that could be applied to other types of internal fixation devices that extend into the femoral neck as long as appropriate cutting tools are available.

Conclusion

THA in the setting of a retained internal fixation device is relatively common. This article describes a technique that can be used when a plate applied to the lateral femoral cortex has become intracortical as a result of extensive bony overgrowth. In using this technique to avoid plate removal, the surgeon eliminates the need for more extensive procedures aimed at compensating for deficiency of the femoral cortex in the area of plate removal. Although only 2 cases are presented here, this technique potentially can be used more broadly in these specific clinical situations.

Total hip arthroplasty (THA) is an effective treatment for advanced hip arthritis from a variety of causes, including osteoarthritis, inflammatory arthritis, posttraumatic arthritis, and sequelae of developmental disorders. It is not uncommon to perform THA in the presence of a previous proximal femoral osteotomy that may have been performed for slipped capital femoral epiphysis (SCFE), Legg-Calvé-Perthes disease, or developmental dysplasia of the hip, among other conditions. These osteotomies are commonly combined with internal fixation, a plate-and-screw device. These patients are at risk for developing degenerative arthritis at an earlier age than patients with other types of arthritis and subsequently may undergo THA at a younger age.^1-3 Presence of a plate can pose a technical challenge during THA surgery. THA performed after intertrochanteric osteotomy has higher rates of perioperative and postoperative complications.4 Ferguson and colleagues4 noted difficulty during hardware removal in 24% of cases. Among the complications encountered were broken hardware, stripped screws, greater trochanteric fracture, stress risers from previous screw holes, canal narrowing from endosteal hypertrophy around hardware, and lateral cortical deficiency after removal of the side plate. As intertrochanteric osteotomies are often performed in patients who have yet to reach skeletal maturity, cortical hypertrophy can lead to complete coverage of the side plate and an “intracortical” position.

This article reports on 2 THA cases in which a technique was used to avoid intracortical plate removal and the resulting problems of lateral cortical deficiency. During each THA, the plate was left in place to avoid compromise of the lateral femoral cortex. The patients provided written informed consent for print and electronic publication of these case reports.

Case Reports

Case 1

An adolescent with bilateral SCFE was treated first with internal fixation of the right hip and subsequently with left proximal femoral osteotomy with internal fixation. He did well until age 31 years, when he developed progressively worsening pain about the left hip. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the left hip. Radiographs showed a sliding hip screw in place, with proximal femoral deformity consisting of femoral neck shortening and posterior angulation (Figures 1A, 1B). Preoperative Harris Hip Score was 54.5.

Case 2

A 51-year-old woman presented with a history of right hip problems dating back to age 13 years, when she sustained a fracture of the right hip and was treated with internal fixation. At age 15 years, she underwent proximal femoral osteotomy to correct residual deformity. She did well until age 45 years, when she developed worsening hip symptoms. Clinical findings and imaging studies were consistent with advanced degenerative arthritis of the right hip. Radiographs showed a fixed-angle blade plate in the proximal femur, with significant proximal femoral deformity (Figures 1C, 1D). Preoperative Harris Hip Score was 53.6.

Surgical Technique

In both cases, a standard series of radiographs was obtained—an anteroposterior (AP) radiograph of the pelvis and AP and cross-table lateral radiographs of the operative hip (Figure 1). Computed tomography (CT) with a metal-artifact-reducing technique may be useful in determining amount of cortical bone remaining under the plate. CT showed limited lateral cortex beneath the side plate and bony overgrowth covering the side plate. Preoperative templating was performed using previously described techniques.⁵

During THA, before removing any portion of any retained hardware, the surgeon should perform 3 important actions: Dislocate the hip, perform all appropriate capsular releases, and reduce the hip. Dislocating the hip before hardware removal significantly decreases the risk for fracture caused by stress risers, as the force required for dislocation is much more controlled because of the capsular releases. After hardware removal, the hip can be easily redislocated, and the femoral neck osteotomy can be performed.

When plate and screws are in an intracortical position, the screws can be removed only after removing the small shell of cortical bone covering them. The amount of bone to be removed is minimal. After the screws are removed, the plate remains in place. A motorized device with a metal-cutting attachment is used to transect the construct at the junction of the plate and barrel (case 1) or at the bend of a fixed-angle device (case 2). Laparotomy sponges are placed around the proximal femur to minimize the amount of soft tissue that could be exposed to metal shavings. Copious irrigation is used throughout this part of the procedure. Osteotomes are used to elevate the proximal portion of the plate and the barrel, preserving the distal portion of the plate on the lateral cortex of the femoral shaft.

After the head is removed, the rest of the THA can be performed using standard press-fit insertion technique (Figures 2A-2D). Care must be taken to ensure that the distal aspect of the femoral stem bypasses the most distal screw hole by at least 2 cortical diameters in order to reduce the risk for periprosthetic fracture.

By 2-year follow-up, both patients had regained excellent range of motion, ambulation, and overall function. Postoperative Harris Hip Scores were 86.6 and 83.8, respectively. There were no radiographic signs of complications.

Discussion

THA can be challenging in the setting of previously placed internal fixation devices, particularly devices inserted during a patient’s adolescence, as significant bony overgrowth can occur. The standard approach has been to remove the internal fixation device and then perform the THA. In most cases, and particularly when the internal fixation device is in an intracortical position, the result is significant compromise of bone. This article describes a technique in which a portion of the hardware is retained to avoid compromise of the lateral femoral cortex, thereby allowing insertion of a noncemented femoral component.

THA is the most effective procedure for reducing hip pain and disability in the setting of degenerative changes.6 Patients with SCFE, Legg-Calvé-Perthes disease, or developmental dysplasia of the hip generally are younger at the time they may be sufficiently symptomatic to consider THA^.7,8 Many have had previous surgery using internal fixation devices. THAs after previous osteotomies with internal fixation devices are more technically demanding, require more operative time, are subject to more blood loss, and have a higher rate of complications, including femoral fracture. Ferguson and colleagues⁴ and Boos and colleagues9 found these surgeries were more difficult 33.8% and 36.8% of the time, respectively. For these reasons, some authors have recommended removing the internal fixation device as soon as the osteotomy is healed.⁴ However, this has not become the standard of care, and surgeons continue to perform THAs in the presence of a previous osteotomy with an internal fixation device in place.

The technique described in this article was used successfully in 2 cases. In each case, leaving the intracortical plate in place avoided compromise of the lateral femoral cortex and allowed insertion of a noncemented femoral component without complication. Of course, with the screw holes representing stress risers, careful insertion of the femoral component was required. Retaining the intracortical plate allowed it to function as part of the lateral femoral cortex, thereby maintaining the structural integrity of the femoral canal. As has been described for the 2 cases, a blade plate and plate and barrel were converted to a limited intracortical plate by removing the proximal portion of the plates—a modification that could be applied to other types of internal fixation devices that extend into the femoral neck as long as appropriate cutting tools are available.

Conclusion

THA in the setting of a retained internal fixation device is relatively common. This article describes a technique that can be used when a plate applied to the lateral femoral cortex has become intracortical as a result of extensive bony overgrowth. In using this technique to avoid plate removal, the surgeon eliminates the need for more extensive procedures aimed at compensating for deficiency of the femoral cortex in the area of plate removal. Although only 2 cases are presented here, this technique potentially can be used more broadly in these specific clinical situations.

Total knee arthroplasty (TKA) is a reliable and successful treatment for end-stage degenerative joint disease of the knee. Given the reproducibility of its generally excellent outcomes, TKA is increasingly being performed.¹ However, the potential complications of this procedure can be devastating.^2-4 The arthroplasty literature has shed light on the detrimental effects of postoperative blood loss and anemia.^5,6 In addition, the increase in transfusion burden among patients is not without risk.⁷ Given these concerns, surgeons have been tasked with determining the ideal methods for minimizing blood transfusions and postoperative hematomas and anemia. Several strategies have been described.^8-11 Hemostasis can be achieved with use of intravenous medications, intra-articular agents, or electrocautery devices. Electrocautery technologies include traditional electrocautery (TE), saline-coupled bipolar sealer (BS), and argon beam coagulation (ABC). There is controversy as to whether outcomes are better with one hemostasis method over another and whether these methods are worth the additional cost.

In traditional (Bovie) electrocautery, a unipolar device delivers an electrical current to tissues through a pencil-like instrument. Intraoperative tissue temperatures can exceed 400°C.¹² In BS, radiofrequency energy is delivered through a saline medium, which increases the contact area, acts as an electrode, and maintains a cooler environment during electrocautery. Proposed advantages are reduced tissue destruction and absence of smoke.¹² There is evidence both for^10,12-16 and against^17-20 use of BS in total joint arthroplasty. ABC, a novel hemostasis method, has been studied in the context of orthopedics^21,22 but not TKA specifically. ABC establishes a monopolar electric circuit between a handheld device and the target tissues by channeling electrons through ionized argon gas. Hemostasis is achieved through thermal coagulation. Tissue penetration can be adjusted by changing power, probe-to-target distance, and duration of use.²³ We conducted a study to assess the efficacy of all 3 electrocautery methods during TKA. We hypothesized the 3 methods would be clinically equivalent with respect to estimated blood loss (EBL), 48-hour wound drainage, operative time, and change from preoperative hemoglobin (Hb) level.

Methods

We conducted a retrospective cohort study of consecutive primary TKAs performed by Dr. Levine between October 2010 and November 2011. Patients were identified by querying an internal database. Exclusion criteria were prior ipsilateral open knee procedure, prior fracture, nonuse of our standard hemostatic protocol, and either tourniquet time under 40 minutes or intraoperative documentation of tourniquet failure. As only 9 patients were initially identified for the TE cohort, the same database was used to add 32 patients treated between April 2009 and October 2009 (before our institution began using BS and ABC).

Clinical charts were reviewed, and baseline demographics (age, body mass index [BMI], preoperative Hb level) were abstracted, as were outcome metrics (EBL, 48-hour wound drainage, operative time, postoperative transfusions, adverse events (AEs) before discharge, and change in Hb level from before surgery to after surgery, in recovery room and on discharge). Statistical analyses were performed with JMP Version 10.0.0 (SAS Institute). Given the hypothesis that the 3 hemostasis methods would be clinically equivalent, 2 one-sided tests (TOSTs) of equivalence were performed with an α of 0.05. With TOST, the traditional null and alternative hypotheses are reversed; thus, P < .05 identifies statistical equivalence. The advantage of this study design is that equivalence can be identified, whereas traditional study designs can identify only a lack of statistical difference.²⁴ We used our consensus opinions to set clinical insignificance thresholds for EBL (150 mL), wound drainage (150 mL), decrease from postoperative Hb level (1 g/dL), and operative time (10 minutes). Patients who received a blood transfusion were subsequently excluded from analysis in order to avoid skewing Hb-level depreciation calculations. Analysis of variance (ANOVA) and χ² tests were used to compare preoperative variables, transfusion requirements, hospital length of stay, and AE rates by hemostasis type.

Cautery Technique

In all cases, TE was used for surgical dissection, which followed a standard midvastus approach. Then, for meniscal excision, the capsule and meniscal attachment sites were treated with TE, BS, or ABC. During cement hardening, an available supplemental cautery option was used to achieve hemostasis of the suprapatellar fat pad and visible meniscal attachment sites. All other aspects of the procedure and the postoperative protocols—including the anticoagulation and rapid rehabilitation (early ambulation and therapy) protocols—were similar for all patients. The standard anticoagulation protocol was to use low-molecular-weight heparin, unless contraindicated. Tranexamic acid was not used at our institution during the study period.

Results

For the study period, 280 cases (41 TE, 203 BS, 36 ABC) met the inclusion criteria. Of the 280 TKAs, 261 (93.21%) were performed for degenerative arthritis. There was no statistically significant difference among cohorts in indication (χ² = 1.841, P = .398) or sex (χ² = 1.176, P= .555).

Table 1 lists the cohorts’ baseline demographics (mean age, BMI, preoperative Hb level) and comparative ANOVA results. TOSTs of equivalence were performed to compare operative time, EBL, 48-hour wound drainage, and postoperative Hb-level depreciation among hemostasis types. Changes in Hb level were calculated for the immediate postoperative period and time of discharge (Table 2). ANOVA of hospital length of stay demonstrated no significant difference in means among groups (P = .09).

The cohorts were compared with respect to use of postoperative transfusions and incidence of postoperative AEs (Table 3). The TE cohort did not have any AEs. Of the 203 BS patients, 14 (7%) had 1 or more AEs, which included acute kidney injury (3 cases), electrolyte disturbance (3), urinary tract infection (2), oxygen desaturation (2), altered mental status (1), pneumonia (1), arrhythmia (1), congestive heart failure exacerbation (1), dehiscence (1), pulmonary embolism (2), and hypotension (1). Of the 36 ABC patients, 1 (3%) had arrhythmia, pneumonia, sepsis, and altered mental status.

Discussion

With the population aging, the demand for TKA is greater than ever.¹ As surgical volume increases, the ability to minimize the rates of intraoperative bleeding, postoperative anemia, and transfusion is becoming increasingly important to patients and the healthcare system. There is no consensus as to which cautery method is ideal. Other investigators have identified differences in clinical outcomes between cautery systems, but reported results are largely conflicting.^10,12-20 In addition, no one has studied the utility of ABC in TKA. In the present retrospective cohort analysis, we hypothesized that TE, BS, and ABC would be clinically equivalent in primary TKA with respect to EBL, 48-hour wound drainage, operative time, and change from preoperative Hb level.

The data on hemostatic technology in primary TKA are inconclusive. In an age- and sex-matched study comparing TE and BS in primary TKA, BS used with shed blood autotransfusion reduced homologous blood transfusions by a factor of 5.16 In addition, BS patients lost significantly less total visible blood (intraoperative EBL, postoperative drain output), and their magnitude of postoperative Hb-level depreciations at time of discharge was significantly lower. In a multicenter, prospective randomized trial comparing TE with BS, adjusted blood loss and need for autologous blood transfusions were lower in BS patients,¹⁰ though there was no significant difference in Knee Society Scale scores between the 2 treatment arms. However, analysis was potentially biased in that multiple authors had financial ties to Salient Surgical Technologies, the manufacturer of the BS device used in the study. Other prospective randomized trials of patients who had primary TKA with either TE or BS did not find any significant difference in postoperative Hb level, postoperative drainage, or transfusion requirements.¹⁹ ABC has been studied in the context of orthopedics but not joint arthroplasty specifically. This technology was anecdotally identified as a means of attaining hemostasis in foot and ankle surgery after failure of TE and other conventional means.²² ABC has also been identified as a successful adjuvant to curettage in the treatment of aneurysmal bone cysts.²¹ However, ABC has not been compared with TE or BS in the orthopedic literature.

In the present study, analysis of preoperative variables revealed a statistically but not clinically significant difference in BMI among cohorts. Mean (SD) BMI was 35.6 (6.5) for TE patients, 35.8 (9.7) for BS patients, and 40.9 (11.3) for ABC patients. (Previously, BMI did not correlate with intraoperative blood loss in TKA.²⁵) Analysis also revealed a statistically significant but clinically insignificant and inconsequential difference in Hb level among cohorts. Mean (SD) preoperative Hb level was 13.5 (1.6) g/dL for TE patients, 12.8 (1.4) g/dL for BS patients, and 13.0 (1.6) g/dL for ABC patients. As decreases from preoperative baseline Hb levels were the intended focus of analysis—not absolute Hb levels—this finding does not refute postoperative analyses.

Our results suggest that, though TE may have relatively longer operative times in primary TKA, it is clinically equivalent to BS and ABC with respect to EBL and postoperative change in Hb levels. In addition, postoperative drainage was lower in TE than in BS and ABC, which were equivalent. No significant differences were found among hemostasis types with respect to postoperative transfusion requirements.

The prevalence distribution of predischarge AEs trended toward significance (χ² = 5.957, P = .051), despite not meeting the predetermined α level. Rates of predischarge AEs were 0% (0/41) for TE patients, 7% (14/203) for BS patients, and 3% (1/36) for ABC patients. AEs included acute kidney injuries, electrolyte disturbances, urinary tract infections, oxygen desaturation, altered mental status, sepsis/infections, arrhythmias, congestive heart failure exacerbation, dehiscence, pulmonary embolism, and hypotension. Clearly, many of these AEs are not attributable to the hemostasis system used.

Limitations of this study include its retrospective design, documentation inadequate to account for drainage amount reinfused, and limited data on which clinical insignificance thresholds were based. In addition, reliance on historical data may have introduced bias into the analysis. The historical data used to increase the size of the TE cohort may reflect a period of relative inexperience and may have contributed to the longer operative times relative to those of the ABC cohort (Dr. Levine used ABC later in his career).

Traditional electrocautery remains a viable option in primary TKA. With its low cost and hemostasis equivalent to that of BS and ABC, TE deserves consideration equal to that given to these more modern hemostasis technologies. Cost per case is about $10 for TE versus $500 for BS and $110 for ABC.¹⁷ Soaring healthcare expenditures may warrant returning to TE or combining cautery techniques and other agents in primary TKA in order to reduce the number of transfusions and associated surgical costs.

Total knee arthroplasty (TKA) is a reliable and successful treatment for end-stage degenerative joint disease of the knee. Given the reproducibility of its generally excellent outcomes, TKA is increasingly being performed.¹ However, the potential complications of this procedure can be devastating.^2-4 The arthroplasty literature has shed light on the detrimental effects of postoperative blood loss and anemia.^5,6 In addition, the increase in transfusion burden among patients is not without risk.⁷ Given these concerns, surgeons have been tasked with determining the ideal methods for minimizing blood transfusions and postoperative hematomas and anemia. Several strategies have been described.^8-11 Hemostasis can be achieved with use of intravenous medications, intra-articular agents, or electrocautery devices. Electrocautery technologies include traditional electrocautery (TE), saline-coupled bipolar sealer (BS), and argon beam coagulation (ABC). There is controversy as to whether outcomes are better with one hemostasis method over another and whether these methods are worth the additional cost.

In traditional (Bovie) electrocautery, a unipolar device delivers an electrical current to tissues through a pencil-like instrument. Intraoperative tissue temperatures can exceed 400°C.¹² In BS, radiofrequency energy is delivered through a saline medium, which increases the contact area, acts as an electrode, and maintains a cooler environment during electrocautery. Proposed advantages are reduced tissue destruction and absence of smoke.¹² There is evidence both for^10,12-16 and against^17-20 use of BS in total joint arthroplasty. ABC, a novel hemostasis method, has been studied in the context of orthopedics^21,22 but not TKA specifically. ABC establishes a monopolar electric circuit between a handheld device and the target tissues by channeling electrons through ionized argon gas. Hemostasis is achieved through thermal coagulation. Tissue penetration can be adjusted by changing power, probe-to-target distance, and duration of use.²³ We conducted a study to assess the efficacy of all 3 electrocautery methods during TKA. We hypothesized the 3 methods would be clinically equivalent with respect to estimated blood loss (EBL), 48-hour wound drainage, operative time, and change from preoperative hemoglobin (Hb) level.

Methods

We conducted a retrospective cohort study of consecutive primary TKAs performed by Dr. Levine between October 2010 and November 2011. Patients were identified by querying an internal database. Exclusion criteria were prior ipsilateral open knee procedure, prior fracture, nonuse of our standard hemostatic protocol, and either tourniquet time under 40 minutes or intraoperative documentation of tourniquet failure. As only 9 patients were initially identified for the TE cohort, the same database was used to add 32 patients treated between April 2009 and October 2009 (before our institution began using BS and ABC).

Clinical charts were reviewed, and baseline demographics (age, body mass index [BMI], preoperative Hb level) were abstracted, as were outcome metrics (EBL, 48-hour wound drainage, operative time, postoperative transfusions, adverse events (AEs) before discharge, and change in Hb level from before surgery to after surgery, in recovery room and on discharge). Statistical analyses were performed with JMP Version 10.0.0 (SAS Institute). Given the hypothesis that the 3 hemostasis methods would be clinically equivalent, 2 one-sided tests (TOSTs) of equivalence were performed with an α of 0.05. With TOST, the traditional null and alternative hypotheses are reversed; thus, P < .05 identifies statistical equivalence. The advantage of this study design is that equivalence can be identified, whereas traditional study designs can identify only a lack of statistical difference.²⁴ We used our consensus opinions to set clinical insignificance thresholds for EBL (150 mL), wound drainage (150 mL), decrease from postoperative Hb level (1 g/dL), and operative time (10 minutes). Patients who received a blood transfusion were subsequently excluded from analysis in order to avoid skewing Hb-level depreciation calculations. Analysis of variance (ANOVA) and χ² tests were used to compare preoperative variables, transfusion requirements, hospital length of stay, and AE rates by hemostasis type.

Cautery Technique

In all cases, TE was used for surgical dissection, which followed a standard midvastus approach. Then, for meniscal excision, the capsule and meniscal attachment sites were treated with TE, BS, or ABC. During cement hardening, an available supplemental cautery option was used to achieve hemostasis of the suprapatellar fat pad and visible meniscal attachment sites. All other aspects of the procedure and the postoperative protocols—including the anticoagulation and rapid rehabilitation (early ambulation and therapy) protocols—were similar for all patients. The standard anticoagulation protocol was to use low-molecular-weight heparin, unless contraindicated. Tranexamic acid was not used at our institution during the study period.

Results

For the study period, 280 cases (41 TE, 203 BS, 36 ABC) met the inclusion criteria. Of the 280 TKAs, 261 (93.21%) were performed for degenerative arthritis. There was no statistically significant difference among cohorts in indication (χ² = 1.841, P = .398) or sex (χ² = 1.176, P= .555).

Table 1 lists the cohorts’ baseline demographics (mean age, BMI, preoperative Hb level) and comparative ANOVA results. TOSTs of equivalence were performed to compare operative time, EBL, 48-hour wound drainage, and postoperative Hb-level depreciation among hemostasis types. Changes in Hb level were calculated for the immediate postoperative period and time of discharge (Table 2). ANOVA of hospital length of stay demonstrated no significant difference in means among groups (P = .09).

The cohorts were compared with respect to use of postoperative transfusions and incidence of postoperative AEs (Table 3). The TE cohort did not have any AEs. Of the 203 BS patients, 14 (7%) had 1 or more AEs, which included acute kidney injury (3 cases), electrolyte disturbance (3), urinary tract infection (2), oxygen desaturation (2), altered mental status (1), pneumonia (1), arrhythmia (1), congestive heart failure exacerbation (1), dehiscence (1), pulmonary embolism (2), and hypotension (1). Of the 36 ABC patients, 1 (3%) had arrhythmia, pneumonia, sepsis, and altered mental status.

Discussion

With the population aging, the demand for TKA is greater than ever.¹ As surgical volume increases, the ability to minimize the rates of intraoperative bleeding, postoperative anemia, and transfusion is becoming increasingly important to patients and the healthcare system. There is no consensus as to which cautery method is ideal. Other investigators have identified differences in clinical outcomes between cautery systems, but reported results are largely conflicting.^10,12-20 In addition, no one has studied the utility of ABC in TKA. In the present retrospective cohort analysis, we hypothesized that TE, BS, and ABC would be clinically equivalent in primary TKA with respect to EBL, 48-hour wound drainage, operative time, and change from preoperative Hb level.

The data on hemostatic technology in primary TKA are inconclusive. In an age- and sex-matched study comparing TE and BS in primary TKA, BS used with shed blood autotransfusion reduced homologous blood transfusions by a factor of 5.16 In addition, BS patients lost significantly less total visible blood (intraoperative EBL, postoperative drain output), and their magnitude of postoperative Hb-level depreciations at time of discharge was significantly lower. In a multicenter, prospective randomized trial comparing TE with BS, adjusted blood loss and need for autologous blood transfusions were lower in BS patients,¹⁰ though there was no significant difference in Knee Society Scale scores between the 2 treatment arms. However, analysis was potentially biased in that multiple authors had financial ties to Salient Surgical Technologies, the manufacturer of the BS device used in the study. Other prospective randomized trials of patients who had primary TKA with either TE or BS did not find any significant difference in postoperative Hb level, postoperative drainage, or transfusion requirements.¹⁹ ABC has been studied in the context of orthopedics but not joint arthroplasty specifically. This technology was anecdotally identified as a means of attaining hemostasis in foot and ankle surgery after failure of TE and other conventional means.²² ABC has also been identified as a successful adjuvant to curettage in the treatment of aneurysmal bone cysts.²¹ However, ABC has not been compared with TE or BS in the orthopedic literature.

In the present study, analysis of preoperative variables revealed a statistically but not clinically significant difference in BMI among cohorts. Mean (SD) BMI was 35.6 (6.5) for TE patients, 35.8 (9.7) for BS patients, and 40.9 (11.3) for ABC patients. (Previously, BMI did not correlate with intraoperative blood loss in TKA.²⁵) Analysis also revealed a statistically significant but clinically insignificant and inconsequential difference in Hb level among cohorts. Mean (SD) preoperative Hb level was 13.5 (1.6) g/dL for TE patients, 12.8 (1.4) g/dL for BS patients, and 13.0 (1.6) g/dL for ABC patients. As decreases from preoperative baseline Hb levels were the intended focus of analysis—not absolute Hb levels—this finding does not refute postoperative analyses.

Our results suggest that, though TE may have relatively longer operative times in primary TKA, it is clinically equivalent to BS and ABC with respect to EBL and postoperative change in Hb levels. In addition, postoperative drainage was lower in TE than in BS and ABC, which were equivalent. No significant differences were found among hemostasis types with respect to postoperative transfusion requirements.

The prevalence distribution of predischarge AEs trended toward significance (χ² = 5.957, P = .051), despite not meeting the predetermined α level. Rates of predischarge AEs were 0% (0/41) for TE patients, 7% (14/203) for BS patients, and 3% (1/36) for ABC patients. AEs included acute kidney injuries, electrolyte disturbances, urinary tract infections, oxygen desaturation, altered mental status, sepsis/infections, arrhythmias, congestive heart failure exacerbation, dehiscence, pulmonary embolism, and hypotension. Clearly, many of these AEs are not attributable to the hemostasis system used.

Limitations of this study include its retrospective design, documentation inadequate to account for drainage amount reinfused, and limited data on which clinical insignificance thresholds were based. In addition, reliance on historical data may have introduced bias into the analysis. The historical data used to increase the size of the TE cohort may reflect a period of relative inexperience and may have contributed to the longer operative times relative to those of the ABC cohort (Dr. Levine used ABC later in his career).

Traditional electrocautery remains a viable option in primary TKA. With its low cost and hemostasis equivalent to that of BS and ABC, TE deserves consideration equal to that given to these more modern hemostasis technologies. Cost per case is about $10 for TE versus $500 for BS and $110 for ABC.¹⁷ Soaring healthcare expenditures may warrant returning to TE or combining cautery techniques and other agents in primary TKA in order to reduce the number of transfusions and associated surgical costs.

Total knee arthroplasty (TKA) is a reliable and successful treatment for end-stage degenerative joint disease of the knee. Given the reproducibility of its generally excellent outcomes, TKA is increasingly being performed.¹ However, the potential complications of this procedure can be devastating.^2-4 The arthroplasty literature has shed light on the detrimental effects of postoperative blood loss and anemia.^5,6 In addition, the increase in transfusion burden among patients is not without risk.⁷ Given these concerns, surgeons have been tasked with determining the ideal methods for minimizing blood transfusions and postoperative hematomas and anemia. Several strategies have been described.^8-11 Hemostasis can be achieved with use of intravenous medications, intra-articular agents, or electrocautery devices. Electrocautery technologies include traditional electrocautery (TE), saline-coupled bipolar sealer (BS), and argon beam coagulation (ABC). There is controversy as to whether outcomes are better with one hemostasis method over another and whether these methods are worth the additional cost.

In traditional (Bovie) electrocautery, a unipolar device delivers an electrical current to tissues through a pencil-like instrument. Intraoperative tissue temperatures can exceed 400°C.¹² In BS, radiofrequency energy is delivered through a saline medium, which increases the contact area, acts as an electrode, and maintains a cooler environment during electrocautery. Proposed advantages are reduced tissue destruction and absence of smoke.¹² There is evidence both for^10,12-16 and against^17-20 use of BS in total joint arthroplasty. ABC, a novel hemostasis method, has been studied in the context of orthopedics^21,22 but not TKA specifically. ABC establishes a monopolar electric circuit between a handheld device and the target tissues by channeling electrons through ionized argon gas. Hemostasis is achieved through thermal coagulation. Tissue penetration can be adjusted by changing power, probe-to-target distance, and duration of use.²³ We conducted a study to assess the efficacy of all 3 electrocautery methods during TKA. We hypothesized the 3 methods would be clinically equivalent with respect to estimated blood loss (EBL), 48-hour wound drainage, operative time, and change from preoperative hemoglobin (Hb) level.

Methods

We conducted a retrospective cohort study of consecutive primary TKAs performed by Dr. Levine between October 2010 and November 2011. Patients were identified by querying an internal database. Exclusion criteria were prior ipsilateral open knee procedure, prior fracture, nonuse of our standard hemostatic protocol, and either tourniquet time under 40 minutes or intraoperative documentation of tourniquet failure. As only 9 patients were initially identified for the TE cohort, the same database was used to add 32 patients treated between April 2009 and October 2009 (before our institution began using BS and ABC).

Clinical charts were reviewed, and baseline demographics (age, body mass index [BMI], preoperative Hb level) were abstracted, as were outcome metrics (EBL, 48-hour wound drainage, operative time, postoperative transfusions, adverse events (AEs) before discharge, and change in Hb level from before surgery to after surgery, in recovery room and on discharge). Statistical analyses were performed with JMP Version 10.0.0 (SAS Institute). Given the hypothesis that the 3 hemostasis methods would be clinically equivalent, 2 one-sided tests (TOSTs) of equivalence were performed with an α of 0.05. With TOST, the traditional null and alternative hypotheses are reversed; thus, P < .05 identifies statistical equivalence. The advantage of this study design is that equivalence can be identified, whereas traditional study designs can identify only a lack of statistical difference.²⁴ We used our consensus opinions to set clinical insignificance thresholds for EBL (150 mL), wound drainage (150 mL), decrease from postoperative Hb level (1 g/dL), and operative time (10 minutes). Patients who received a blood transfusion were subsequently excluded from analysis in order to avoid skewing Hb-level depreciation calculations. Analysis of variance (ANOVA) and χ² tests were used to compare preoperative variables, transfusion requirements, hospital length of stay, and AE rates by hemostasis type.

Cautery Technique

In all cases, TE was used for surgical dissection, which followed a standard midvastus approach. Then, for meniscal excision, the capsule and meniscal attachment sites were treated with TE, BS, or ABC. During cement hardening, an available supplemental cautery option was used to achieve hemostasis of the suprapatellar fat pad and visible meniscal attachment sites. All other aspects of the procedure and the postoperative protocols—including the anticoagulation and rapid rehabilitation (early ambulation and therapy) protocols—were similar for all patients. The standard anticoagulation protocol was to use low-molecular-weight heparin, unless contraindicated. Tranexamic acid was not used at our institution during the study period.

Results

For the study period, 280 cases (41 TE, 203 BS, 36 ABC) met the inclusion criteria. Of the 280 TKAs, 261 (93.21%) were performed for degenerative arthritis. There was no statistically significant difference among cohorts in indication (χ² = 1.841, P = .398) or sex (χ² = 1.176, P= .555).

Table 1 lists the cohorts’ baseline demographics (mean age, BMI, preoperative Hb level) and comparative ANOVA results. TOSTs of equivalence were performed to compare operative time, EBL, 48-hour wound drainage, and postoperative Hb-level depreciation among hemostasis types. Changes in Hb level were calculated for the immediate postoperative period and time of discharge (Table 2). ANOVA of hospital length of stay demonstrated no significant difference in means among groups (P = .09).

The cohorts were compared with respect to use of postoperative transfusions and incidence of postoperative AEs (Table 3). The TE cohort did not have any AEs. Of the 203 BS patients, 14 (7%) had 1 or more AEs, which included acute kidney injury (3 cases), electrolyte disturbance (3), urinary tract infection (2), oxygen desaturation (2), altered mental status (1), pneumonia (1), arrhythmia (1), congestive heart failure exacerbation (1), dehiscence (1), pulmonary embolism (2), and hypotension (1). Of the 36 ABC patients, 1 (3%) had arrhythmia, pneumonia, sepsis, and altered mental status.

Discussion

With the population aging, the demand for TKA is greater than ever.¹ As surgical volume increases, the ability to minimize the rates of intraoperative bleeding, postoperative anemia, and transfusion is becoming increasingly important to patients and the healthcare system. There is no consensus as to which cautery method is ideal. Other investigators have identified differences in clinical outcomes between cautery systems, but reported results are largely conflicting.^10,12-20 In addition, no one has studied the utility of ABC in TKA. In the present retrospective cohort analysis, we hypothesized that TE, BS, and ABC would be clinically equivalent in primary TKA with respect to EBL, 48-hour wound drainage, operative time, and change from preoperative Hb level.

The data on hemostatic technology in primary TKA are inconclusive. In an age- and sex-matched study comparing TE and BS in primary TKA, BS used with shed blood autotransfusion reduced homologous blood transfusions by a factor of 5.16 In addition, BS patients lost significantly less total visible blood (intraoperative EBL, postoperative drain output), and their magnitude of postoperative Hb-level depreciations at time of discharge was significantly lower. In a multicenter, prospective randomized trial comparing TE with BS, adjusted blood loss and need for autologous blood transfusions were lower in BS patients,¹⁰ though there was no significant difference in Knee Society Scale scores between the 2 treatment arms. However, analysis was potentially biased in that multiple authors had financial ties to Salient Surgical Technologies, the manufacturer of the BS device used in the study. Other prospective randomized trials of patients who had primary TKA with either TE or BS did not find any significant difference in postoperative Hb level, postoperative drainage, or transfusion requirements.¹⁹ ABC has been studied in the context of orthopedics but not joint arthroplasty specifically. This technology was anecdotally identified as a means of attaining hemostasis in foot and ankle surgery after failure of TE and other conventional means.²² ABC has also been identified as a successful adjuvant to curettage in the treatment of aneurysmal bone cysts.²¹ However, ABC has not been compared with TE or BS in the orthopedic literature.

In the present study, analysis of preoperative variables revealed a statistically but not clinically significant difference in BMI among cohorts. Mean (SD) BMI was 35.6 (6.5) for TE patients, 35.8 (9.7) for BS patients, and 40.9 (11.3) for ABC patients. (Previously, BMI did not correlate with intraoperative blood loss in TKA.²⁵) Analysis also revealed a statistically significant but clinically insignificant and inconsequential difference in Hb level among cohorts. Mean (SD) preoperative Hb level was 13.5 (1.6) g/dL for TE patients, 12.8 (1.4) g/dL for BS patients, and 13.0 (1.6) g/dL for ABC patients. As decreases from preoperative baseline Hb levels were the intended focus of analysis—not absolute Hb levels—this finding does not refute postoperative analyses.

Our results suggest that, though TE may have relatively longer operative times in primary TKA, it is clinically equivalent to BS and ABC with respect to EBL and postoperative change in Hb levels. In addition, postoperative drainage was lower in TE than in BS and ABC, which were equivalent. No significant differences were found among hemostasis types with respect to postoperative transfusion requirements.

The prevalence distribution of predischarge AEs trended toward significance (χ² = 5.957, P = .051), despite not meeting the predetermined α level. Rates of predischarge AEs were 0% (0/41) for TE patients, 7% (14/203) for BS patients, and 3% (1/36) for ABC patients. AEs included acute kidney injuries, electrolyte disturbances, urinary tract infections, oxygen desaturation, altered mental status, sepsis/infections, arrhythmias, congestive heart failure exacerbation, dehiscence, pulmonary embolism, and hypotension. Clearly, many of these AEs are not attributable to the hemostasis system used.

Limitations of this study include its retrospective design, documentation inadequate to account for drainage amount reinfused, and limited data on which clinical insignificance thresholds were based. In addition, reliance on historical data may have introduced bias into the analysis. The historical data used to increase the size of the TE cohort may reflect a period of relative inexperience and may have contributed to the longer operative times relative to those of the ABC cohort (Dr. Levine used ABC later in his career).

Traditional electrocautery remains a viable option in primary TKA. With its low cost and hemostasis equivalent to that of BS and ABC, TE deserves consideration equal to that given to these more modern hemostasis technologies. Cost per case is about $10 for TE versus $500 for BS and $110 for ABC.¹⁷ Soaring healthcare expenditures may warrant returning to TE or combining cautery techniques and other agents in primary TKA in order to reduce the number of transfusions and associated surgical costs.

Body mass index (BMI) is thought to be a predictor of body composition, with higher values indicating more adipose tissue. BMI is a measure of mass with respect to height. The World Health Organization¹ has established health categories based on BMI measurements. Values from 18.5 to 24.9 kg/m² are deemed to represent normal weight; those from 25 to 30 kg/m², overweight; and those higher than 30 kg/m², obesity. BMI is not a perfect tool, but it is the most widely used tool in clinical and research practice because of its relative reliability and ease of use.² Being overweight or obese (according to BMI) is increasingly common among adults worldwide, and particularly in the United States. An estimated 39% of adults worldwide are overweight, and 13% are obese.¹ An estimated 69% of US adults are overweight, including 35.1% who are obese.²

Various pathologies have been treated with reverse shoulder arthroplasty (RSA), and results have been promising,^3-9 but little is known about patient demographic and clinical factors that may adversely affect outcomes. Recent work suggests younger age⁷ and failed prior arthroplasty may adversely affect RSA outcomes.¹⁰ Higher BMI has also been implicated as a cause of increased perioperative and immediate postoperative complications of RSA with minimum 90-day follow-up, but no one has examined shoulder function scores at minimum 2-year follow-up.^11,12

We conducted a study to examine shoulder function scores, mobility, patient satisfaction, and complications at minimum 2-year follow-up in normal-weight, overweight, and obese patients who underwent RSA. We hypothesized that, compared with normal-weight patients, obese patients would have worse shoulder function scores, worse mobility, and more complications.

Materials and Methods

Inclusion Criteria and Demographics

After obtaining Institutional Review Board approval for this study, we used a prospective shoulder arthroplasty registry to identify patients (N = 77) who had rotator cuff tear arthropathy (RCTA) treated with primary RSA and then had minimum 2-year follow-up. The study period was 2004-2011. All patients had RCTA diagnosed with physical examination findings and anteroposterior, scapular Y, and axillary radiographs. RCTA was graded 1 to 5 using the classification system of Hamada and colleagues.¹³ Rotator cuff status was determined with preoperative computed tomography arthrogram (CTA) or magnetic resonance imaging (MRI) and confirmed at time of surgery. BMI calculations were based on height and weight measured at initial office visit. Thirty-four patients had normal weight (BMI <25 kg/m²), 21 were overweight (BMI 25-30 kg/m²), and 22 were obese (BMI >30 kg/m²). Patient demographic and clinical characteristics reviewed also included age, sex, follow-up duration, arm dominance, complications, prevalence of depression, and prevalence of diabetes. All RSAs were performed by the same surgeon (Dr. Edwards) at a single high-volume shoulder arthroplasty center.

Shoulder function scores evaluated before surgery and at final follow-up included Constant score,¹⁴ American Shoulder and Elbow Surgeons (ASES) score,¹⁵ Western Ontario Osteoarthritis Shoulder (WOOS) index,¹⁶ Single Assessment Numeric Evaluation (SANE),¹⁷ and mobility. Satisfaction was assessed by having patients describe themselves as very dissatisfied, dissatisfied, satisfied, or very satisfied. All intraoperative and postoperative complications were recorded.

Surgical Technique and Postoperative Rehabilitation

The Aequalis RSA system (Tornier) was used for all patients during the study period. The RSA technique used has been well described.^18,19 A standard postoperative rehabilitation protocol was followed.^19,20

Clinical and Radiographic Assessment

Patients were prospectively enrolled in a shoulder arthroplasty outcomes registry and followed clinically. Mean follow-up was 3.16 years (range, 2-8 years). Before surgery, patients were examined by the surgeon. Examinations were repeated 1 week, 6 weeks, 3 months, 6 months, and 12 months after surgery and annually thereafter. Mobility (active range of motion) was determined with a handheld goniometer. Strength of abduction was measured with a handheld digital dynamometer (Chatillon digital force gauge, 200 lbf; Ametek). Anteroposterior in plane of scapula, scapular Y, and axillary radiographs were obtained at each clinic appointment.

Before surgery, the surgeon reviewed all radiographs. Each RCTA was given a Hamada grade (1-5).¹³ Glenoid erosion in the coronal plane was classified (E0, E1, E2, E3) according to Sirveaux and colleagues.²¹ Hamada grades and glenoid erosion types are listed in Table 1. The overall trend in classification by BMI group was statistically significant for Hamada grade (P = .004) but not glenoid erosion type (P = .153).

Before surgery, the surgeon also evaluated rotator cuff status using CTA or MRI. All patients had full-thickness tears of the supraspinatus and infraspinatus. The subscapularis was variably present, and subscapularis repair was performed when the subscapularis was intact. Rotator cuff status is listed in Table 2. There were no significant differences in the distribution of intact subscapularis (P = .402) or teres minor (P = .188) among the normal-weight, overweight, and obese groups. No patient had a latissimus dorsi transfer at time of RSA.

Statistical Analysis

Independent-samples t tests assuming unequal variances were used to compare the 3 BMI groups on age, follow-up duration, preoperative shoulder function scores, and mobility. Chi-square tests were used to identify any significant group differences in comorbidities (eg, complications, arm dominance, prevalence of depression, prevalence of diabetes) and patient satisfaction. Repeated-measures analysis of variance was used to evaluate main effects, changes from before surgery to final follow-up, and BMI group differences, as well as differences in changes from before surgery to final follow-up among the 3 BMI groups.

Results

Among BMI groups (<25 kg/m², 25-30 kg/m², >30 kg/m²), there were no statistically significant preoperative differences in age, sex, follow-up duration, complications, arm dominance, prevalence of depression, or prevalence of diabetes (P >. 05) (Table 3). Table 4 lists the groups’ preoperative and final follow-up data (Constant score, ASES score, WOOS index, SANE, mobility). There were no statistically significant preoperative group differences in Constant score, ASES score, WOOS index, SANE, mobility, or patient satisfaction (P > .05) (Tables 5, 6).

All groups’ shoulder function scores and mobility improved significantly from before surgery to final follow-up (P < .001) (Table 5). The groups’ magnitudes of change (improvement) from before surgery to final follow-up were almost identical, with no significant differences in shoulder function scores or mobility (Table 5). The only significant difference was in Constant–Strength, which was higher in the obese group (P = .017) (Table 5). Patient satisfaction ratings improved after surgery, with 79% of the normal-weight group reporting being satisfied or very satisfied with their shoulders (Table 6). The overweight and obese groups gave similar satisfied (81%) and very satisfied (82%) ratings. The small differences between group satisfaction scores were nonsignificant (P = .967).

Complications

The normal-weight group had 4 complications: periprosthetic infection (2 cases), intraoperative humeral fracture (1), and scapular spine stress fracture (1). The overweight group had 1 complication, an acromial stress fracture that was successfully treated with conservative measures. The obese group had 1 patient with 2 postoperative dislocations. The first dislocation was treated with closed reduction and bracing, and the second required revision surgery. There was no statistical difference in complications among the groups (P = .680).

Discussion

To our knowledge, this is the first study of the effects of varying BMI on functional outcomes of RSA with minimum 2-year follow-up. There appears to be minimal impact on shoulder function scores, complications, and patient satisfaction among normal-weight, overweight, and obese patients with RCTA treated by the same surgeon using similar techniques.

The relationship between obesity and increased perioperative risks or poorer surgical outcomes has been well established in orthopedic surgery. In a systematic review, Falagas and Kompoti²² found increased risk for perioperative and nosocomial infections in obese patients. Schoenfeld and colleagues²³ and Jiang and colleagues²⁴ reported increased risk for complications in spinal surgery. The total joint arthroplasty literature is rife with evidence suggesting higher BMI leads to increased risk for complications, including infection and deep venous thrombosis, as well as decreased functional outcome scores.^25-29 Recent studies on shoulder surgery have shown worse outcomes in rotator cuff repair³⁰ and a higher revision rate in hemiarthroplasy.³¹

Other RSA studies have examined short-term complications or perioperative risk factors associated with BMI. In a study using slightly different BMI groupings, Gupta and colleagues¹² reported significantly higher complication rates for RSA patients with BMI higher than 35 kg/m² compared to patients with BMI of 25 to 35 kg/m² and compared to patients with BMI lower than 25 kg/m². Their study highlighted medical and surgical complications and used a short follow-up period (minimum, 90 days). It did not assess shoulder function scores, and included multiple indications for RSA (eg, RCTA, proximal humerus fracture, inflammatory arthropathy). In another study, higher BMI was reported as a risk factor for early dislocation after RSA, but only 11 patients with a history of dislocation were assessed, and minimum follow-up was 6 months.³² We know of only one study that addressed RSA outcomes in obese patients and used minimum 2-year follow-up, but its primary endpoint was rate of complications, and it did not report shoulder function scores.¹¹ Li and colleagues³³ conducted a study similar to ours, but with primary total shoulder arthroplasty (TSA) patients, and reported similar results. Relative to normal BMI, higher BMI did not have a detrimental effect on short-term improvement in shoulder function after TSA.

Given the US obesity epidemic, our study results are encouraging. Depending on many factors, obesity remains a risk factor for poor outcomes in patients who undergo orthopedic surgery. As our results show, however, patients with higher BMI can obtain functional outcomes similar to those experienced by patients with normal-weight BMI after RSA for RCTA.

The primary limitation of this study was its retrospective design. Strengths of the study included its having a single surgeon and a single diagnosis: RCTA. In addition, each group was robust in size, a standard operative/postoperative protocol was used, and clinical results were measured with multiple validated shoulder function scores.

Conclusion

Improved shoulder function scores, mobility, and patient satisfaction can be expected after RSA for RCTA in patients with BMI higher than 30 kg/m². These patients did not exhibit an increase in complications at short-term follow-up.

Body mass index (BMI) is thought to be a predictor of body composition, with higher values indicating more adipose tissue. BMI is a measure of mass with respect to height. The World Health Organization¹ has established health categories based on BMI measurements. Values from 18.5 to 24.9 kg/m² are deemed to represent normal weight; those from 25 to 30 kg/m², overweight; and those higher than 30 kg/m², obesity. BMI is not a perfect tool, but it is the most widely used tool in clinical and research practice because of its relative reliability and ease of use.² Being overweight or obese (according to BMI) is increasingly common among adults worldwide, and particularly in the United States. An estimated 39% of adults worldwide are overweight, and 13% are obese.¹ An estimated 69% of US adults are overweight, including 35.1% who are obese.²

Various pathologies have been treated with reverse shoulder arthroplasty (RSA), and results have been promising,^3-9 but little is known about patient demographic and clinical factors that may adversely affect outcomes. Recent work suggests younger age⁷ and failed prior arthroplasty may adversely affect RSA outcomes.¹⁰ Higher BMI has also been implicated as a cause of increased perioperative and immediate postoperative complications of RSA with minimum 90-day follow-up, but no one has examined shoulder function scores at minimum 2-year follow-up.^11,12

We conducted a study to examine shoulder function scores, mobility, patient satisfaction, and complications at minimum 2-year follow-up in normal-weight, overweight, and obese patients who underwent RSA. We hypothesized that, compared with normal-weight patients, obese patients would have worse shoulder function scores, worse mobility, and more complications.

Materials and Methods

Inclusion Criteria and Demographics

After obtaining Institutional Review Board approval for this study, we used a prospective shoulder arthroplasty registry to identify patients (N = 77) who had rotator cuff tear arthropathy (RCTA) treated with primary RSA and then had minimum 2-year follow-up. The study period was 2004-2011. All patients had RCTA diagnosed with physical examination findings and anteroposterior, scapular Y, and axillary radiographs. RCTA was graded 1 to 5 using the classification system of Hamada and colleagues.¹³ Rotator cuff status was determined with preoperative computed tomography arthrogram (CTA) or magnetic resonance imaging (MRI) and confirmed at time of surgery. BMI calculations were based on height and weight measured at initial office visit. Thirty-four patients had normal weight (BMI <25 kg/m²), 21 were overweight (BMI 25-30 kg/m²), and 22 were obese (BMI >30 kg/m²). Patient demographic and clinical characteristics reviewed also included age, sex, follow-up duration, arm dominance, complications, prevalence of depression, and prevalence of diabetes. All RSAs were performed by the same surgeon (Dr. Edwards) at a single high-volume shoulder arthroplasty center.

Shoulder function scores evaluated before surgery and at final follow-up included Constant score,¹⁴ American Shoulder and Elbow Surgeons (ASES) score,¹⁵ Western Ontario Osteoarthritis Shoulder (WOOS) index,¹⁶ Single Assessment Numeric Evaluation (SANE),¹⁷ and mobility. Satisfaction was assessed by having patients describe themselves as very dissatisfied, dissatisfied, satisfied, or very satisfied. All intraoperative and postoperative complications were recorded.

Surgical Technique and Postoperative Rehabilitation

The Aequalis RSA system (Tornier) was used for all patients during the study period. The RSA technique used has been well described.^18,19 A standard postoperative rehabilitation protocol was followed.^19,20

Clinical and Radiographic Assessment

Patients were prospectively enrolled in a shoulder arthroplasty outcomes registry and followed clinically. Mean follow-up was 3.16 years (range, 2-8 years). Before surgery, patients were examined by the surgeon. Examinations were repeated 1 week, 6 weeks, 3 months, 6 months, and 12 months after surgery and annually thereafter. Mobility (active range of motion) was determined with a handheld goniometer. Strength of abduction was measured with a handheld digital dynamometer (Chatillon digital force gauge, 200 lbf; Ametek). Anteroposterior in plane of scapula, scapular Y, and axillary radiographs were obtained at each clinic appointment.

Before surgery, the surgeon reviewed all radiographs. Each RCTA was given a Hamada grade (1-5).¹³ Glenoid erosion in the coronal plane was classified (E0, E1, E2, E3) according to Sirveaux and colleagues.²¹ Hamada grades and glenoid erosion types are listed in Table 1. The overall trend in classification by BMI group was statistically significant for Hamada grade (P = .004) but not glenoid erosion type (P = .153).

Before surgery, the surgeon also evaluated rotator cuff status using CTA or MRI. All patients had full-thickness tears of the supraspinatus and infraspinatus. The subscapularis was variably present, and subscapularis repair was performed when the subscapularis was intact. Rotator cuff status is listed in Table 2. There were no significant differences in the distribution of intact subscapularis (P = .402) or teres minor (P = .188) among the normal-weight, overweight, and obese groups. No patient had a latissimus dorsi transfer at time of RSA.

Statistical Analysis

Independent-samples t tests assuming unequal variances were used to compare the 3 BMI groups on age, follow-up duration, preoperative shoulder function scores, and mobility. Chi-square tests were used to identify any significant group differences in comorbidities (eg, complications, arm dominance, prevalence of depression, prevalence of diabetes) and patient satisfaction. Repeated-measures analysis of variance was used to evaluate main effects, changes from before surgery to final follow-up, and BMI group differences, as well as differences in changes from before surgery to final follow-up among the 3 BMI groups.

Results

Among BMI groups (<25 kg/m², 25-30 kg/m², >30 kg/m²), there were no statistically significant preoperative differences in age, sex, follow-up duration, complications, arm dominance, prevalence of depression, or prevalence of diabetes (P >. 05) (Table 3). Table 4 lists the groups’ preoperative and final follow-up data (Constant score, ASES score, WOOS index, SANE, mobility). There were no statistically significant preoperative group differences in Constant score, ASES score, WOOS index, SANE, mobility, or patient satisfaction (P > .05) (Tables 5, 6).

All groups’ shoulder function scores and mobility improved significantly from before surgery to final follow-up (P < .001) (Table 5). The groups’ magnitudes of change (improvement) from before surgery to final follow-up were almost identical, with no significant differences in shoulder function scores or mobility (Table 5). The only significant difference was in Constant–Strength, which was higher in the obese group (P = .017) (Table 5). Patient satisfaction ratings improved after surgery, with 79% of the normal-weight group reporting being satisfied or very satisfied with their shoulders (Table 6). The overweight and obese groups gave similar satisfied (81%) and very satisfied (82%) ratings. The small differences between group satisfaction scores were nonsignificant (P = .967).

Complications

The normal-weight group had 4 complications: periprosthetic infection (2 cases), intraoperative humeral fracture (1), and scapular spine stress fracture (1). The overweight group had 1 complication, an acromial stress fracture that was successfully treated with conservative measures. The obese group had 1 patient with 2 postoperative dislocations. The first dislocation was treated with closed reduction and bracing, and the second required revision surgery. There was no statistical difference in complications among the groups (P = .680).

Discussion

To our knowledge, this is the first study of the effects of varying BMI on functional outcomes of RSA with minimum 2-year follow-up. There appears to be minimal impact on shoulder function scores, complications, and patient satisfaction among normal-weight, overweight, and obese patients with RCTA treated by the same surgeon using similar techniques.

The relationship between obesity and increased perioperative risks or poorer surgical outcomes has been well established in orthopedic surgery. In a systematic review, Falagas and Kompoti²² found increased risk for perioperative and nosocomial infections in obese patients. Schoenfeld and colleagues²³ and Jiang and colleagues²⁴ reported increased risk for complications in spinal surgery. The total joint arthroplasty literature is rife with evidence suggesting higher BMI leads to increased risk for complications, including infection and deep venous thrombosis, as well as decreased functional outcome scores.^25-29 Recent studies on shoulder surgery have shown worse outcomes in rotator cuff repair³⁰ and a higher revision rate in hemiarthroplasy.³¹

Other RSA studies have examined short-term complications or perioperative risk factors associated with BMI. In a study using slightly different BMI groupings, Gupta and colleagues¹² reported significantly higher complication rates for RSA patients with BMI higher than 35 kg/m² compared to patients with BMI of 25 to 35 kg/m² and compared to patients with BMI lower than 25 kg/m². Their study highlighted medical and surgical complications and used a short follow-up period (minimum, 90 days). It did not assess shoulder function scores, and included multiple indications for RSA (eg, RCTA, proximal humerus fracture, inflammatory arthropathy). In another study, higher BMI was reported as a risk factor for early dislocation after RSA, but only 11 patients with a history of dislocation were assessed, and minimum follow-up was 6 months.³² We know of only one study that addressed RSA outcomes in obese patients and used minimum 2-year follow-up, but its primary endpoint was rate of complications, and it did not report shoulder function scores.¹¹ Li and colleagues³³ conducted a study similar to ours, but with primary total shoulder arthroplasty (TSA) patients, and reported similar results. Relative to normal BMI, higher BMI did not have a detrimental effect on short-term improvement in shoulder function after TSA.

Given the US obesity epidemic, our study results are encouraging. Depending on many factors, obesity remains a risk factor for poor outcomes in patients who undergo orthopedic surgery. As our results show, however, patients with higher BMI can obtain functional outcomes similar to those experienced by patients with normal-weight BMI after RSA for RCTA.

The primary limitation of this study was its retrospective design. Strengths of the study included its having a single surgeon and a single diagnosis: RCTA. In addition, each group was robust in size, a standard operative/postoperative protocol was used, and clinical results were measured with multiple validated shoulder function scores.

Conclusion

Improved shoulder function scores, mobility, and patient satisfaction can be expected after RSA for RCTA in patients with BMI higher than 30 kg/m². These patients did not exhibit an increase in complications at short-term follow-up.

Body mass index (BMI) is thought to be a predictor of body composition, with higher values indicating more adipose tissue. BMI is a measure of mass with respect to height. The World Health Organization¹ has established health categories based on BMI measurements. Values from 18.5 to 24.9 kg/m² are deemed to represent normal weight; those from 25 to 30 kg/m², overweight; and those higher than 30 kg/m², obesity. BMI is not a perfect tool, but it is the most widely used tool in clinical and research practice because of its relative reliability and ease of use.² Being overweight or obese (according to BMI) is increasingly common among adults worldwide, and particularly in the United States. An estimated 39% of adults worldwide are overweight, and 13% are obese.¹ An estimated 69% of US adults are overweight, including 35.1% who are obese.²

Various pathologies have been treated with reverse shoulder arthroplasty (RSA), and results have been promising,^3-9 but little is known about patient demographic and clinical factors that may adversely affect outcomes. Recent work suggests younger age⁷ and failed prior arthroplasty may adversely affect RSA outcomes.¹⁰ Higher BMI has also been implicated as a cause of increased perioperative and immediate postoperative complications of RSA with minimum 90-day follow-up, but no one has examined shoulder function scores at minimum 2-year follow-up.^11,12

We conducted a study to examine shoulder function scores, mobility, patient satisfaction, and complications at minimum 2-year follow-up in normal-weight, overweight, and obese patients who underwent RSA. We hypothesized that, compared with normal-weight patients, obese patients would have worse shoulder function scores, worse mobility, and more complications.

Materials and Methods

Inclusion Criteria and Demographics

After obtaining Institutional Review Board approval for this study, we used a prospective shoulder arthroplasty registry to identify patients (N = 77) who had rotator cuff tear arthropathy (RCTA) treated with primary RSA and then had minimum 2-year follow-up. The study period was 2004-2011. All patients had RCTA diagnosed with physical examination findings and anteroposterior, scapular Y, and axillary radiographs. RCTA was graded 1 to 5 using the classification system of Hamada and colleagues.¹³ Rotator cuff status was determined with preoperative computed tomography arthrogram (CTA) or magnetic resonance imaging (MRI) and confirmed at time of surgery. BMI calculations were based on height and weight measured at initial office visit. Thirty-four patients had normal weight (BMI <25 kg/m²), 21 were overweight (BMI 25-30 kg/m²), and 22 were obese (BMI >30 kg/m²). Patient demographic and clinical characteristics reviewed also included age, sex, follow-up duration, arm dominance, complications, prevalence of depression, and prevalence of diabetes. All RSAs were performed by the same surgeon (Dr. Edwards) at a single high-volume shoulder arthroplasty center.

Shoulder function scores evaluated before surgery and at final follow-up included Constant score,¹⁴ American Shoulder and Elbow Surgeons (ASES) score,¹⁵ Western Ontario Osteoarthritis Shoulder (WOOS) index,¹⁶ Single Assessment Numeric Evaluation (SANE),¹⁷ and mobility. Satisfaction was assessed by having patients describe themselves as very dissatisfied, dissatisfied, satisfied, or very satisfied. All intraoperative and postoperative complications were recorded.

Surgical Technique and Postoperative Rehabilitation

The Aequalis RSA system (Tornier) was used for all patients during the study period. The RSA technique used has been well described.^18,19 A standard postoperative rehabilitation protocol was followed.^19,20

Clinical and Radiographic Assessment

Patients were prospectively enrolled in a shoulder arthroplasty outcomes registry and followed clinically. Mean follow-up was 3.16 years (range, 2-8 years). Before surgery, patients were examined by the surgeon. Examinations were repeated 1 week, 6 weeks, 3 months, 6 months, and 12 months after surgery and annually thereafter. Mobility (active range of motion) was determined with a handheld goniometer. Strength of abduction was measured with a handheld digital dynamometer (Chatillon digital force gauge, 200 lbf; Ametek). Anteroposterior in plane of scapula, scapular Y, and axillary radiographs were obtained at each clinic appointment.

Before surgery, the surgeon reviewed all radiographs. Each RCTA was given a Hamada grade (1-5).¹³ Glenoid erosion in the coronal plane was classified (E0, E1, E2, E3) according to Sirveaux and colleagues.²¹ Hamada grades and glenoid erosion types are listed in Table 1. The overall trend in classification by BMI group was statistically significant for Hamada grade (P = .004) but not glenoid erosion type (P = .153).

Before surgery, the surgeon also evaluated rotator cuff status using CTA or MRI. All patients had full-thickness tears of the supraspinatus and infraspinatus. The subscapularis was variably present, and subscapularis repair was performed when the subscapularis was intact. Rotator cuff status is listed in Table 2. There were no significant differences in the distribution of intact subscapularis (P = .402) or teres minor (P = .188) among the normal-weight, overweight, and obese groups. No patient had a latissimus dorsi transfer at time of RSA.

Statistical Analysis

Independent-samples t tests assuming unequal variances were used to compare the 3 BMI groups on age, follow-up duration, preoperative shoulder function scores, and mobility. Chi-square tests were used to identify any significant group differences in comorbidities (eg, complications, arm dominance, prevalence of depression, prevalence of diabetes) and patient satisfaction. Repeated-measures analysis of variance was used to evaluate main effects, changes from before surgery to final follow-up, and BMI group differences, as well as differences in changes from before surgery to final follow-up among the 3 BMI groups.

Results

Among BMI groups (<25 kg/m², 25-30 kg/m², >30 kg/m²), there were no statistically significant preoperative differences in age, sex, follow-up duration, complications, arm dominance, prevalence of depression, or prevalence of diabetes (P >. 05) (Table 3). Table 4 lists the groups’ preoperative and final follow-up data (Constant score, ASES score, WOOS index, SANE, mobility). There were no statistically significant preoperative group differences in Constant score, ASES score, WOOS index, SANE, mobility, or patient satisfaction (P > .05) (Tables 5, 6).

All groups’ shoulder function scores and mobility improved significantly from before surgery to final follow-up (P < .001) (Table 5). The groups’ magnitudes of change (improvement) from before surgery to final follow-up were almost identical, with no significant differences in shoulder function scores or mobility (Table 5). The only significant difference was in Constant–Strength, which was higher in the obese group (P = .017) (Table 5). Patient satisfaction ratings improved after surgery, with 79% of the normal-weight group reporting being satisfied or very satisfied with their shoulders (Table 6). The overweight and obese groups gave similar satisfied (81%) and very satisfied (82%) ratings. The small differences between group satisfaction scores were nonsignificant (P = .967).

Complications

The normal-weight group had 4 complications: periprosthetic infection (2 cases), intraoperative humeral fracture (1), and scapular spine stress fracture (1). The overweight group had 1 complication, an acromial stress fracture that was successfully treated with conservative measures. The obese group had 1 patient with 2 postoperative dislocations. The first dislocation was treated with closed reduction and bracing, and the second required revision surgery. There was no statistical difference in complications among the groups (P = .680).

Discussion

To our knowledge, this is the first study of the effects of varying BMI on functional outcomes of RSA with minimum 2-year follow-up. There appears to be minimal impact on shoulder function scores, complications, and patient satisfaction among normal-weight, overweight, and obese patients with RCTA treated by the same surgeon using similar techniques.

The relationship between obesity and increased perioperative risks or poorer surgical outcomes has been well established in orthopedic surgery. In a systematic review, Falagas and Kompoti²² found increased risk for perioperative and nosocomial infections in obese patients. Schoenfeld and colleagues²³ and Jiang and colleagues²⁴ reported increased risk for complications in spinal surgery. The total joint arthroplasty literature is rife with evidence suggesting higher BMI leads to increased risk for complications, including infection and deep venous thrombosis, as well as decreased functional outcome scores.^25-29 Recent studies on shoulder surgery have shown worse outcomes in rotator cuff repair³⁰ and a higher revision rate in hemiarthroplasy.³¹

Other RSA studies have examined short-term complications or perioperative risk factors associated with BMI. In a study using slightly different BMI groupings, Gupta and colleagues¹² reported significantly higher complication rates for RSA patients with BMI higher than 35 kg/m² compared to patients with BMI of 25 to 35 kg/m² and compared to patients with BMI lower than 25 kg/m². Their study highlighted medical and surgical complications and used a short follow-up period (minimum, 90 days). It did not assess shoulder function scores, and included multiple indications for RSA (eg, RCTA, proximal humerus fracture, inflammatory arthropathy). In another study, higher BMI was reported as a risk factor for early dislocation after RSA, but only 11 patients with a history of dislocation were assessed, and minimum follow-up was 6 months.³² We know of only one study that addressed RSA outcomes in obese patients and used minimum 2-year follow-up, but its primary endpoint was rate of complications, and it did not report shoulder function scores.¹¹ Li and colleagues³³ conducted a study similar to ours, but with primary total shoulder arthroplasty (TSA) patients, and reported similar results. Relative to normal BMI, higher BMI did not have a detrimental effect on short-term improvement in shoulder function after TSA.

Given the US obesity epidemic, our study results are encouraging. Depending on many factors, obesity remains a risk factor for poor outcomes in patients who undergo orthopedic surgery. As our results show, however, patients with higher BMI can obtain functional outcomes similar to those experienced by patients with normal-weight BMI after RSA for RCTA.

The primary limitation of this study was its retrospective design. Strengths of the study included its having a single surgeon and a single diagnosis: RCTA. In addition, each group was robust in size, a standard operative/postoperative protocol was used, and clinical results were measured with multiple validated shoulder function scores.

Conclusion

Improved shoulder function scores, mobility, and patient satisfaction can be expected after RSA for RCTA in patients with BMI higher than 30 kg/m². These patients did not exhibit an increase in complications at short-term follow-up.

Patients undergoing total knee arthroplasty (TKA) may benefit from focused postoperative rehabilitation. Although there is limited research comparing different rehabilitation protocols after TKA,¹ any type of rehabilitation often helps to optimize range of motion (ROM), strength, balance, and ambulation.² Early mobilization and rehabilitation after TKA reduces pain, fear, anxiety, and risk of postoperative venous thromboembolic disease.³ Earlier discharge to home or community settings deceases time for inpatient rehabilitation, patient and family education, and gait training, which places a greater emphasis on outpatient rehabilitation.⁴

Although rapid rehabilitation protocols have gained wide acceptance, concern remains that a higher intensity intervention initiated immediately after hospital discharge could lead to an increased incidence of pain and swelling, and to poorer ROM and functional outcomes.⁵ Progressive weight-bearing activities, such as walking, are routinely recommended during rehabilitation to facilitate return to normal function. Not all patients are capable of full weight-bearing activity in the early postoperative period and assistive devices (ADs), such as walkers, crutches, and canes, are routinely employed. An opportunity to enhance early TKA rehabilitation exists with devices that allow functional gait training while modifying weight-bearing forces across the joint. Assistive devices, hydrotherapy (walking in water),^6,7 and lower body positive-pressure chambers⁸ can reduce the forces at the knee during weight-bearing exercise.

Lower body positive-pressure devices have been extensively studied in physiological response of healthy humans;^9-12 in disease states such as cerebral palsy¹³ and obesity;¹⁴ and in other postoperative orthopedic conditions, such as anterior cruciate ligament reconstruction, meniscectomy,⁸ microfracture,¹⁵ TKA,¹⁶ and Achilles tendon repair.¹⁷ These studies demonstrate that a lower body positive-pressure treadmill is associated with minimal cardiovascular effect while producing a significant decrease in ground reaction forces without altering gait kinematics.

We postulated that an anti-gravity treadmill may be safe and effective for gait training during rehabilitation following TKA. The primary objective was to determine the safety and feasibility of using the AlterG^® Anti-Gravity Treadmill^® device for postoperative gait training during rehabilitation following TKA. The secondary objective was to determine the effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on subjective patient outcomes assessed by Knee Injury and Osteoarthritis Outcome Score (KOOS), mobility assessed by the Timed Up and Go test (TUG), and pain assessed by a Numerical Rating Scale (NRS) to conduct a power analysis to determine sample sizes for efficacy studies based on these preliminary findings.

MethodsParticipants/Patient Enrollment and Study Overview

After signing an Institutional Review Board-approved consent, 30 patients were enrolled, and TKA surgeries were performed by 1 of 5 surgeons at 1 hospital. To be enrolled in the study, subjects must have (1) had a unilateral primary TKA, (2) been discharged from the hospital to home (not to a skilled nursing facility), (3) had only 3 to 4 home physical therapy (PT) sessions, (4) agreed to further outpatient PT at a single site, and (5) agreed to complete patient questionnaires. Exclusion criteria included (1) inability to meet inclusion criteria, (2) gross musculoskeletal deformity, (3) uncontrolled chronic or systemic disease, and (4) inability to follow instructions because of mental impairment, substance abuse, or addiction. Home PT was conducted for 3 to 4 sessions after surgery, and outpatient PT was continued at the study site per protocol for 4 weeks; subjects were asked to return for follow-up 3 months postoperatively. Patients were randomized on the first day of their outpatient PT to either a land-based (control) or an anti-gravity-based group using the AlterG Anti-Gravity Treadmill (AlterG group) gait training during outpatient PT sessions. Patients attended outpatient PT 2 days per week for 4 weeks for a total of 8 sessions. Therapy sessions lasted 45 to 60 minutes and included manual therapy, gait training, and therapeutic exercises/activities. The KOOS^18,19 and TUG²⁰ scores were evaluated at baseline (ie, first therapy session), end of physical therapy (EOPT) (ie, at final therapy session), and end of study (EOS) (ie, 3 months postoperatively). The NRS for pain was evaluated at baseline and at EOPT. Physical therapists were questioned for satisfaction with the anti-gravity rehabilitation protocol at EOPT.

Physical Therapy Protocols

All patients were treated consistently by 1 of 5 physical therapists at 1 outpatient setting; physical therapists averaged 11 years of experience in treating orthopedic conditions. Care was delivered in accordance with professional standards and the therapist’s assessment of medical necessity. Considerations included, but were not limited to, overall general health, any medical comorbidity, support system, and an ongoing assessment of ROM, strength, pain, and functional status. Each PT session started with a 5- to 10-minute warm-up on a standard cycle ergometer and was followed by manual therapy, gait training (land-based vs anti-gravity), therapeutic exercises/activities, and treatment modalities.

The time spent, activities selected, and modalities or physical agents chosen during the PT session were based on the patient’s needs and progress toward his/her functional goals. Manual therapy techniques consisted of soft-tissue mobilization, passive ROM, joint mobilization, passive stretching, scar mobilization, manual resistive exercises, and proprioceptive neuromuscular facilitation techniques. Therapeutic exercises/activities consisted of lower extremity resistance exercises (weight bearing and non-weight bearing), ROM exercises, stretching, balance, stair training, agility, activities of daily life (ADL) training, and a comprehensive home exercise program. Modalities or physical agents used during this study included moist hot packs, cold packs, ultrasound, electrical stimulation, and Kinesio Tape. Physical agents were incorporated into the individual’s plan of care based on medical necessity when deemed appropriate by the treating therapist. The exercise prescription was based on an individual’s status and tolerance and the number of sets and repetitions were based on fatigue.

Gait Training

The patients were randomized (1:1) to either land-based or anti-gravity gait training. For the control group, land-based gait training was performed with or without an appropriate AD and appropriate assistance, tactile cueing, and verbal cueing from a physical therapist. Duration (minutes) and gait-training progression were dependent on the participant’s functional goals, pain level (assessed throughout treatment), and level of fatigue. For the AlterG group, gait training was performed in the AlterG Anti-Gravity Treadmill, M320 (Alter-G; Figure 1). On day 1, the AlterG pressure chamber was set to allow only 50% of the patient’s body weight to be transmitted to the treadmill floor, and speed was controlled by the patient according to his/her comfort level. The percentage of body weight was adjusted to allow for a safe and normalized gait pattern with a pain level no greater than 5 (0 to 10 scale) throughout the PT session. A report card was recorded at each PT session, including body-weight setting (%), speed (miles per hour), incline (%), and duration (minutes) (Figure 2). For subsequent visits, the body-weight setting was started from the end point of the previous session.

Data Collection and Analysis

SPSS version 12.0 (SPSS Inc.) was used for all analyses, and an alpha level of .05 determined statistical significance when comparing group differences. The safety and feasibility of the anti-gravity (AlterG) vs land-based (control) gait training was assessed by the presence (or absence) of adverse events (AEs) and complications, and the date the patient discontinued use of his/her AD. A chi-square test was used to assess differences between control and AlterG groups regarding patient discontinuance of an AD. Additionally, for patients randomized to AlterG, a report card summarized means and frequencies for body weight, speed, incline, and duration. At EOPT, the frequency of therapists who were satisfied with the AlterG Anti-Gravity Treadmill as part of the rehabilitation protocol was reported. The preliminary effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on functional outcomes (subjective patient outcomes assessed by KOOS, mobility assessed by the TUG test, and pain assessed by a NRS) were evaluated by independent sample t tests. Paired sample t tests were used to compare each of the functional outcomes at EOPT or EOS to the baseline value.

Results

Of the 30 patients enrolled, 29 (96.7%; 29/30) patients completed the study; 1 patient, who could not complete all PT sessions because of medical and transportation issues, was excluded. The remaining 29 patients comprised the study population (control = 15; AlterG = 14). All patients were compliant with PT protocols.

Patient demographics were similar between the control and AlterG groups (Table 1). The control group comprised 9 women (60%; 9/15) and 6 men (40%; 6/15), age 69.9 ± 7.8 years and a body mass index of 28.8 ± 4.2. Similarly, the AlterG group comprised 7 women (50%; 7/14) and 7 men (50%; 7/14), age 66.5 ± 7.8 years and a body mass index of 28.4 ± 5.2.

At the baseline PT visit, patients in the control and AlterG groups had similar KOOS, TUG, and NRS scores. At baseline, mean KOOS for symptoms, pain, sports/recreation, ADL, and quality of life were 52.7, 52.9, 22.7, 64, and 31.8, respectively, although 50% of patients did not complete the sports/recreation subset of the KOOS. In addition, the mean time to complete the TUG test was 14.5 seconds, which was within the normal limits for disabled patients. This was slightly longer than normal mobility (TUG <10 seconds),20 but patients had relatively low levels of pain (mean NRS = 2.5, on a scale of 0-11).

All patients completed the PT protocols without indication of injury or AEs related to their operative knee. Three patients (10.3%; 3/29) experienced a deep venous thromboembolism (DVT), 2 in the control group (13.3%; 2/15), and 1 in the AlterG group (7.1%; 1/14). Venous thromboembolism protocol of enoxaparin 30 mg twice daily while in the hospital and enoxaparin 40 mg once daily for 10 days after discharge was followed for all patients.

Overall, more than half of patients (55.2%; 16/29) discontinued their AD during the 4-week PT period, with the remaining discontinuing prior to EOPT (24.1%; 7/29) or after EOPT (20.7%; 6/29). No statistically significant differences were found between the control and AlterG groups regarding discontinuance of AD.

Among those randomized to the AlterG group, all patients performed within the protocol established for the device for body-weight setting, treadmill speed, and duration of walking. The average body-weight treadmill setting increased by ~30% over the treatment period, from 55% at baseline to 84% at EOPT. The average speed increased by ~70%, from 1.6 mph at baseline to 2.7 mph at EOPT. The mean duration of AlterG use increased by ~75%, from 7.2 minutes at baseline to 12.7 minutes at EOPT. All physical therapists (100%) reported satisfaction with the AlterG for use in early postoperative rehabilitation and reported that patients’ treatment progressed positively.

While functional outcomes (KOOS, TUG, or NRS) did not vary with the type of gait training (P > .2 for land-based vs anti-gravity), functional outcomes improved over time (all P < .01 from baseline to EOPT and all P < .01 from baseline to EOS).

The KOOS scores improved from baseline to EOPT and from baseline to EOS (ie, 3-month follow-up visit) for both treatment groups (Figure 3). More patients completed the sports/recreation portion of the KOOS scores at EOPT and EOS compared to baseline. Forty-three percent and 25% of patients did not complete KOOS sports/recreation questions at EOPT and EOS, respectively, compared to 50% at baseline. This suggests that patients were improving to a level where sports/recreation scores were more applicable than directly after TKA surgery. The TUG scores had the greatest improvement from baseline to EOPT, with a decrease in time of 5 seconds and 7 seconds for the control and AlterG groups, respectively, and slight improvement from EOPT to EOS, with a decrease in time of 1 second and 2 seconds for the control and AlterG groups, respectively (Table 2). By the EOS, the values for the TUG tests for both treatment groups were within normal (<10 seconds) range.²⁰ The NRS scores improved from baseline to EOPT with a score of 1 ± 1 in both control and AlterG groups.

Using these preliminary efficacy results, a post-hoc power analysis (α = .05 and 1β = 80%) was performed with the ADL domain of KOOS as the primary endpoint. Based on a standard deviation of 20 points and an effect size of 5 points, the sample size was estimated to be N = 250 per treatment group.

Discussion

We conducted a pilot study to assess, primarily, the feasibility and safety, and, secondarily, the efficacy, of a lower body positive-pressure treadmill for rehabilitation of patients after TKA. This small study showed that use of the AlterG Anti-Gravity Treadmill was not only safe and feasible during postoperative TKA rehabilitation, but also was well tolerated by patients and was rated highly satisfactory by physical therapists. Patients who used AlterG during gait training improved functionally (in terms of KOOS, TUG, and NRS) after 8 treatment sessions compared to baseline. However, there were no statistical differences between groups (control vs AlterG). Thus, these results suggest that an anti-gravity device for gait training may be a useful adjunct for postoperative TKA rehabilitation, but further studies are needed to determine the efficacy of anti-gravity compared to traditional land-based gait training.

The study of rehabilitation protocols during postoperative PT involved consideration of a number of issues. First, differences in functional outcomes compared to traditional rehabilitation could not be detected in this study because of the small number of patients, but the patients treated with anti-gravity gait training showed improvement in functional outcomes over time and did not report any added complications. Given that the primary outcome of this study was safety and feasibility, these added efficacy results are supplemental and useful in helping to plan studies. Second, the functional outcomes used to measure the efficacy of the anti-gravity treadmill may not be sensitive enough to detect differences between rehabilitation protocols. Use of a treadmill to measure speed improvement, endurance, and tolerance in both groups could be valuable in future studies. More studies may need to refine characteristics that are important to postoperative rehabilitation success, and quantitative and subjective measures that must be defined.

The results reported here using an anti-gravity treadmill for postoperative TKA rehabilitation support the safety and feasibility that has been reported in other orthopedic rehabilitation settings. Anti-gravity treadmills, which have been used to study patients after meniscectomy or anterior cruciate ligament reconstruction8 and Achilles repair,¹⁷ have demonstrated predictable decreases in ground reaction forces with increasing positive-pressure unweighting, reductions in pain with ambulation, and allowance of earlier institution of walking and jogging during rehabilitation.¹⁷

Patient safety is an important attribute for any postoperative rehabilitation protocol, especially in an elderly population undergoing major surgery. One of our important goals was to assess the safety of AlterG. We noted no AEs attributable to the device, which was supported by work indicating no adverse impact on systemic cardiovascular parameters in a similar lower body positive-pressure environment.⁹ Although 3 patients (10%) developed symptomatic DVT, there were no differences between the groups in the incidence of DVT. Use of an anti-gravity treadmill has also been examined for cardiovascular responses in TKA patients. In a study of 24 adults with TKA, researchers found that anti-gravity support allowed TKA patients to walk at faster speeds and tolerate greater inclines with lower heart rate, blood pressure, and oxygen consumption.²¹ With respect to efficacy of the rehabilitation intervention, we demonstrated significant improvements in all functional outcomes in both groups but no differences between the study groups. We concluded that AlterG was at least as effective as standard therapy in this small cohort. TKA is a very successful procedure, and the improvement in pain and function after surgery is fairly dramatic in most patients, regardless of specific rehabilitation protocols. Therefore, the substantial improvement in clinical outcomes may overshadow any enhanced benefits of the anti-gravity treadmill. Further investigations into the efficacy of AlterG are needed in a larger cohort to determine if this type of treatment is more beneficial than traditional land-based gait training.

Standard scoring systems such as KOOS, TUG, and NRS may not be sensitive enough to detect differences between treatment groups with small sample sizes. Given the results of the post hoc power analysis, a large number of patients (N = 250/group) would be necessary to detect any potential difference in clinical outcomes between the 2 groups. Larger studies are required to answer relevant questions, and additional outcome measures may be needed to detect differences between treatment groups. Relevant questions include whether earlier institution of the anti-gravity device during the immediate TKA postoperative period would be beneficial compared to standard postoperative PT, and whether PT enhanced with the anti-gravity device has incremental benefit in functional outcomes and in time to reach those goals. Finally, given the present attention to healthcare expenses, a cost-benefit analysis of anti-gravity device treatment vs traditional PT would be useful. Once the patient has become familiar with the function of an anti-gravity treadmill, gait therapy could proceed without the direct intervention of the therapist, potentially improving efficient delivery of rehabilitation services.

Studying the effect of different postoperative rehabilitation protocols after orthopedic surgeries can be challenging. In a large (N > 350) randomized controlled trial to study the effect of ergometer cycling after hip and knee replacement, patients who used the cycle ergometer had a higher Western Ontario and McMaster Universities Arthritis Index and greater satisfaction than those who did not after hip arthroplasty, but not after TKA.²² Improvements in muscular coordination and proprioception with the cycle ergometer may have been offset by increases in edema, joint effusion, and pain from the loading of the joint and the relatively fast rate of cycling compared to passive motion or ambulation. While many therapists and surgeons advocate cycling for rehabilitation after knee surgery, the need remains for a better definition of an optimal TKA rehabilitation program. A study of 82 patients comparing early progressive strength training to no early strength training showed no difference in the 6-minute walk test at 8 weeks.²³ A systematic review of progressive resistance training (PRT) found that although postoperative PRT is safe and feasible, the methodological quality of existing studies is too low to allow conclusions regarding its efficacy.²⁴ Gait training in an environment where weight-bearing loads can be closely controlled, monitored, and individualized may be an ideal methodology to enhance rehabilitation and return to function for knee replacement surgery.

This current study showed that the use of AlterG as an adjunct for postoperative rehabilitation is safe, accepted by patients and therapists, and leads to clinical functional outcomes that are at least as good as traditional postoperative TKA rehabilitation. We conclude that AlterG demonstrates utility and a potential for innovation in TKA rehabilitation.

Patients undergoing total knee arthroplasty (TKA) may benefit from focused postoperative rehabilitation. Although there is limited research comparing different rehabilitation protocols after TKA,¹ any type of rehabilitation often helps to optimize range of motion (ROM), strength, balance, and ambulation.² Early mobilization and rehabilitation after TKA reduces pain, fear, anxiety, and risk of postoperative venous thromboembolic disease.³ Earlier discharge to home or community settings deceases time for inpatient rehabilitation, patient and family education, and gait training, which places a greater emphasis on outpatient rehabilitation.⁴

Although rapid rehabilitation protocols have gained wide acceptance, concern remains that a higher intensity intervention initiated immediately after hospital discharge could lead to an increased incidence of pain and swelling, and to poorer ROM and functional outcomes.⁵ Progressive weight-bearing activities, such as walking, are routinely recommended during rehabilitation to facilitate return to normal function. Not all patients are capable of full weight-bearing activity in the early postoperative period and assistive devices (ADs), such as walkers, crutches, and canes, are routinely employed. An opportunity to enhance early TKA rehabilitation exists with devices that allow functional gait training while modifying weight-bearing forces across the joint. Assistive devices, hydrotherapy (walking in water),^6,7 and lower body positive-pressure chambers⁸ can reduce the forces at the knee during weight-bearing exercise.

Lower body positive-pressure devices have been extensively studied in physiological response of healthy humans;^9-12 in disease states such as cerebral palsy¹³ and obesity;¹⁴ and in other postoperative orthopedic conditions, such as anterior cruciate ligament reconstruction, meniscectomy,⁸ microfracture,¹⁵ TKA,¹⁶ and Achilles tendon repair.¹⁷ These studies demonstrate that a lower body positive-pressure treadmill is associated with minimal cardiovascular effect while producing a significant decrease in ground reaction forces without altering gait kinematics.

We postulated that an anti-gravity treadmill may be safe and effective for gait training during rehabilitation following TKA. The primary objective was to determine the safety and feasibility of using the AlterG^® Anti-Gravity Treadmill^® device for postoperative gait training during rehabilitation following TKA. The secondary objective was to determine the effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on subjective patient outcomes assessed by Knee Injury and Osteoarthritis Outcome Score (KOOS), mobility assessed by the Timed Up and Go test (TUG), and pain assessed by a Numerical Rating Scale (NRS) to conduct a power analysis to determine sample sizes for efficacy studies based on these preliminary findings.

MethodsParticipants/Patient Enrollment and Study Overview

After signing an Institutional Review Board-approved consent, 30 patients were enrolled, and TKA surgeries were performed by 1 of 5 surgeons at 1 hospital. To be enrolled in the study, subjects must have (1) had a unilateral primary TKA, (2) been discharged from the hospital to home (not to a skilled nursing facility), (3) had only 3 to 4 home physical therapy (PT) sessions, (4) agreed to further outpatient PT at a single site, and (5) agreed to complete patient questionnaires. Exclusion criteria included (1) inability to meet inclusion criteria, (2) gross musculoskeletal deformity, (3) uncontrolled chronic or systemic disease, and (4) inability to follow instructions because of mental impairment, substance abuse, or addiction. Home PT was conducted for 3 to 4 sessions after surgery, and outpatient PT was continued at the study site per protocol for 4 weeks; subjects were asked to return for follow-up 3 months postoperatively. Patients were randomized on the first day of their outpatient PT to either a land-based (control) or an anti-gravity-based group using the AlterG Anti-Gravity Treadmill (AlterG group) gait training during outpatient PT sessions. Patients attended outpatient PT 2 days per week for 4 weeks for a total of 8 sessions. Therapy sessions lasted 45 to 60 minutes and included manual therapy, gait training, and therapeutic exercises/activities. The KOOS^18,19 and TUG²⁰ scores were evaluated at baseline (ie, first therapy session), end of physical therapy (EOPT) (ie, at final therapy session), and end of study (EOS) (ie, 3 months postoperatively). The NRS for pain was evaluated at baseline and at EOPT. Physical therapists were questioned for satisfaction with the anti-gravity rehabilitation protocol at EOPT.

Physical Therapy Protocols

All patients were treated consistently by 1 of 5 physical therapists at 1 outpatient setting; physical therapists averaged 11 years of experience in treating orthopedic conditions. Care was delivered in accordance with professional standards and the therapist’s assessment of medical necessity. Considerations included, but were not limited to, overall general health, any medical comorbidity, support system, and an ongoing assessment of ROM, strength, pain, and functional status. Each PT session started with a 5- to 10-minute warm-up on a standard cycle ergometer and was followed by manual therapy, gait training (land-based vs anti-gravity), therapeutic exercises/activities, and treatment modalities.

The time spent, activities selected, and modalities or physical agents chosen during the PT session were based on the patient’s needs and progress toward his/her functional goals. Manual therapy techniques consisted of soft-tissue mobilization, passive ROM, joint mobilization, passive stretching, scar mobilization, manual resistive exercises, and proprioceptive neuromuscular facilitation techniques. Therapeutic exercises/activities consisted of lower extremity resistance exercises (weight bearing and non-weight bearing), ROM exercises, stretching, balance, stair training, agility, activities of daily life (ADL) training, and a comprehensive home exercise program. Modalities or physical agents used during this study included moist hot packs, cold packs, ultrasound, electrical stimulation, and Kinesio Tape. Physical agents were incorporated into the individual’s plan of care based on medical necessity when deemed appropriate by the treating therapist. The exercise prescription was based on an individual’s status and tolerance and the number of sets and repetitions were based on fatigue.

Gait Training

The patients were randomized (1:1) to either land-based or anti-gravity gait training. For the control group, land-based gait training was performed with or without an appropriate AD and appropriate assistance, tactile cueing, and verbal cueing from a physical therapist. Duration (minutes) and gait-training progression were dependent on the participant’s functional goals, pain level (assessed throughout treatment), and level of fatigue. For the AlterG group, gait training was performed in the AlterG Anti-Gravity Treadmill, M320 (Alter-G; Figure 1). On day 1, the AlterG pressure chamber was set to allow only 50% of the patient’s body weight to be transmitted to the treadmill floor, and speed was controlled by the patient according to his/her comfort level. The percentage of body weight was adjusted to allow for a safe and normalized gait pattern with a pain level no greater than 5 (0 to 10 scale) throughout the PT session. A report card was recorded at each PT session, including body-weight setting (%), speed (miles per hour), incline (%), and duration (minutes) (Figure 2). For subsequent visits, the body-weight setting was started from the end point of the previous session.

Data Collection and Analysis

SPSS version 12.0 (SPSS Inc.) was used for all analyses, and an alpha level of .05 determined statistical significance when comparing group differences. The safety and feasibility of the anti-gravity (AlterG) vs land-based (control) gait training was assessed by the presence (or absence) of adverse events (AEs) and complications, and the date the patient discontinued use of his/her AD. A chi-square test was used to assess differences between control and AlterG groups regarding patient discontinuance of an AD. Additionally, for patients randomized to AlterG, a report card summarized means and frequencies for body weight, speed, incline, and duration. At EOPT, the frequency of therapists who were satisfied with the AlterG Anti-Gravity Treadmill as part of the rehabilitation protocol was reported. The preliminary effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on functional outcomes (subjective patient outcomes assessed by KOOS, mobility assessed by the TUG test, and pain assessed by a NRS) were evaluated by independent sample t tests. Paired sample t tests were used to compare each of the functional outcomes at EOPT or EOS to the baseline value.

Results

Of the 30 patients enrolled, 29 (96.7%; 29/30) patients completed the study; 1 patient, who could not complete all PT sessions because of medical and transportation issues, was excluded. The remaining 29 patients comprised the study population (control = 15; AlterG = 14). All patients were compliant with PT protocols.

Patient demographics were similar between the control and AlterG groups (Table 1). The control group comprised 9 women (60%; 9/15) and 6 men (40%; 6/15), age 69.9 ± 7.8 years and a body mass index of 28.8 ± 4.2. Similarly, the AlterG group comprised 7 women (50%; 7/14) and 7 men (50%; 7/14), age 66.5 ± 7.8 years and a body mass index of 28.4 ± 5.2.

At the baseline PT visit, patients in the control and AlterG groups had similar KOOS, TUG, and NRS scores. At baseline, mean KOOS for symptoms, pain, sports/recreation, ADL, and quality of life were 52.7, 52.9, 22.7, 64, and 31.8, respectively, although 50% of patients did not complete the sports/recreation subset of the KOOS. In addition, the mean time to complete the TUG test was 14.5 seconds, which was within the normal limits for disabled patients. This was slightly longer than normal mobility (TUG <10 seconds),20 but patients had relatively low levels of pain (mean NRS = 2.5, on a scale of 0-11).

All patients completed the PT protocols without indication of injury or AEs related to their operative knee. Three patients (10.3%; 3/29) experienced a deep venous thromboembolism (DVT), 2 in the control group (13.3%; 2/15), and 1 in the AlterG group (7.1%; 1/14). Venous thromboembolism protocol of enoxaparin 30 mg twice daily while in the hospital and enoxaparin 40 mg once daily for 10 days after discharge was followed for all patients.

Overall, more than half of patients (55.2%; 16/29) discontinued their AD during the 4-week PT period, with the remaining discontinuing prior to EOPT (24.1%; 7/29) or after EOPT (20.7%; 6/29). No statistically significant differences were found between the control and AlterG groups regarding discontinuance of AD.

Among those randomized to the AlterG group, all patients performed within the protocol established for the device for body-weight setting, treadmill speed, and duration of walking. The average body-weight treadmill setting increased by ~30% over the treatment period, from 55% at baseline to 84% at EOPT. The average speed increased by ~70%, from 1.6 mph at baseline to 2.7 mph at EOPT. The mean duration of AlterG use increased by ~75%, from 7.2 minutes at baseline to 12.7 minutes at EOPT. All physical therapists (100%) reported satisfaction with the AlterG for use in early postoperative rehabilitation and reported that patients’ treatment progressed positively.

While functional outcomes (KOOS, TUG, or NRS) did not vary with the type of gait training (P > .2 for land-based vs anti-gravity), functional outcomes improved over time (all P < .01 from baseline to EOPT and all P < .01 from baseline to EOS).

The KOOS scores improved from baseline to EOPT and from baseline to EOS (ie, 3-month follow-up visit) for both treatment groups (Figure 3). More patients completed the sports/recreation portion of the KOOS scores at EOPT and EOS compared to baseline. Forty-three percent and 25% of patients did not complete KOOS sports/recreation questions at EOPT and EOS, respectively, compared to 50% at baseline. This suggests that patients were improving to a level where sports/recreation scores were more applicable than directly after TKA surgery. The TUG scores had the greatest improvement from baseline to EOPT, with a decrease in time of 5 seconds and 7 seconds for the control and AlterG groups, respectively, and slight improvement from EOPT to EOS, with a decrease in time of 1 second and 2 seconds for the control and AlterG groups, respectively (Table 2). By the EOS, the values for the TUG tests for both treatment groups were within normal (<10 seconds) range.²⁰ The NRS scores improved from baseline to EOPT with a score of 1 ± 1 in both control and AlterG groups.

Using these preliminary efficacy results, a post-hoc power analysis (α = .05 and 1β = 80%) was performed with the ADL domain of KOOS as the primary endpoint. Based on a standard deviation of 20 points and an effect size of 5 points, the sample size was estimated to be N = 250 per treatment group.

Discussion

We conducted a pilot study to assess, primarily, the feasibility and safety, and, secondarily, the efficacy, of a lower body positive-pressure treadmill for rehabilitation of patients after TKA. This small study showed that use of the AlterG Anti-Gravity Treadmill was not only safe and feasible during postoperative TKA rehabilitation, but also was well tolerated by patients and was rated highly satisfactory by physical therapists. Patients who used AlterG during gait training improved functionally (in terms of KOOS, TUG, and NRS) after 8 treatment sessions compared to baseline. However, there were no statistical differences between groups (control vs AlterG). Thus, these results suggest that an anti-gravity device for gait training may be a useful adjunct for postoperative TKA rehabilitation, but further studies are needed to determine the efficacy of anti-gravity compared to traditional land-based gait training.

The study of rehabilitation protocols during postoperative PT involved consideration of a number of issues. First, differences in functional outcomes compared to traditional rehabilitation could not be detected in this study because of the small number of patients, but the patients treated with anti-gravity gait training showed improvement in functional outcomes over time and did not report any added complications. Given that the primary outcome of this study was safety and feasibility, these added efficacy results are supplemental and useful in helping to plan studies. Second, the functional outcomes used to measure the efficacy of the anti-gravity treadmill may not be sensitive enough to detect differences between rehabilitation protocols. Use of a treadmill to measure speed improvement, endurance, and tolerance in both groups could be valuable in future studies. More studies may need to refine characteristics that are important to postoperative rehabilitation success, and quantitative and subjective measures that must be defined.

The results reported here using an anti-gravity treadmill for postoperative TKA rehabilitation support the safety and feasibility that has been reported in other orthopedic rehabilitation settings. Anti-gravity treadmills, which have been used to study patients after meniscectomy or anterior cruciate ligament reconstruction8 and Achilles repair,¹⁷ have demonstrated predictable decreases in ground reaction forces with increasing positive-pressure unweighting, reductions in pain with ambulation, and allowance of earlier institution of walking and jogging during rehabilitation.¹⁷

Patient safety is an important attribute for any postoperative rehabilitation protocol, especially in an elderly population undergoing major surgery. One of our important goals was to assess the safety of AlterG. We noted no AEs attributable to the device, which was supported by work indicating no adverse impact on systemic cardiovascular parameters in a similar lower body positive-pressure environment.⁹ Although 3 patients (10%) developed symptomatic DVT, there were no differences between the groups in the incidence of DVT. Use of an anti-gravity treadmill has also been examined for cardiovascular responses in TKA patients. In a study of 24 adults with TKA, researchers found that anti-gravity support allowed TKA patients to walk at faster speeds and tolerate greater inclines with lower heart rate, blood pressure, and oxygen consumption.²¹ With respect to efficacy of the rehabilitation intervention, we demonstrated significant improvements in all functional outcomes in both groups but no differences between the study groups. We concluded that AlterG was at least as effective as standard therapy in this small cohort. TKA is a very successful procedure, and the improvement in pain and function after surgery is fairly dramatic in most patients, regardless of specific rehabilitation protocols. Therefore, the substantial improvement in clinical outcomes may overshadow any enhanced benefits of the anti-gravity treadmill. Further investigations into the efficacy of AlterG are needed in a larger cohort to determine if this type of treatment is more beneficial than traditional land-based gait training.

Standard scoring systems such as KOOS, TUG, and NRS may not be sensitive enough to detect differences between treatment groups with small sample sizes. Given the results of the post hoc power analysis, a large number of patients (N = 250/group) would be necessary to detect any potential difference in clinical outcomes between the 2 groups. Larger studies are required to answer relevant questions, and additional outcome measures may be needed to detect differences between treatment groups. Relevant questions include whether earlier institution of the anti-gravity device during the immediate TKA postoperative period would be beneficial compared to standard postoperative PT, and whether PT enhanced with the anti-gravity device has incremental benefit in functional outcomes and in time to reach those goals. Finally, given the present attention to healthcare expenses, a cost-benefit analysis of anti-gravity device treatment vs traditional PT would be useful. Once the patient has become familiar with the function of an anti-gravity treadmill, gait therapy could proceed without the direct intervention of the therapist, potentially improving efficient delivery of rehabilitation services.

Studying the effect of different postoperative rehabilitation protocols after orthopedic surgeries can be challenging. In a large (N > 350) randomized controlled trial to study the effect of ergometer cycling after hip and knee replacement, patients who used the cycle ergometer had a higher Western Ontario and McMaster Universities Arthritis Index and greater satisfaction than those who did not after hip arthroplasty, but not after TKA.²² Improvements in muscular coordination and proprioception with the cycle ergometer may have been offset by increases in edema, joint effusion, and pain from the loading of the joint and the relatively fast rate of cycling compared to passive motion or ambulation. While many therapists and surgeons advocate cycling for rehabilitation after knee surgery, the need remains for a better definition of an optimal TKA rehabilitation program. A study of 82 patients comparing early progressive strength training to no early strength training showed no difference in the 6-minute walk test at 8 weeks.²³ A systematic review of progressive resistance training (PRT) found that although postoperative PRT is safe and feasible, the methodological quality of existing studies is too low to allow conclusions regarding its efficacy.²⁴ Gait training in an environment where weight-bearing loads can be closely controlled, monitored, and individualized may be an ideal methodology to enhance rehabilitation and return to function for knee replacement surgery.

This current study showed that the use of AlterG as an adjunct for postoperative rehabilitation is safe, accepted by patients and therapists, and leads to clinical functional outcomes that are at least as good as traditional postoperative TKA rehabilitation. We conclude that AlterG demonstrates utility and a potential for innovation in TKA rehabilitation.

Patients undergoing total knee arthroplasty (TKA) may benefit from focused postoperative rehabilitation. Although there is limited research comparing different rehabilitation protocols after TKA,¹ any type of rehabilitation often helps to optimize range of motion (ROM), strength, balance, and ambulation.² Early mobilization and rehabilitation after TKA reduces pain, fear, anxiety, and risk of postoperative venous thromboembolic disease.³ Earlier discharge to home or community settings deceases time for inpatient rehabilitation, patient and family education, and gait training, which places a greater emphasis on outpatient rehabilitation.⁴

Although rapid rehabilitation protocols have gained wide acceptance, concern remains that a higher intensity intervention initiated immediately after hospital discharge could lead to an increased incidence of pain and swelling, and to poorer ROM and functional outcomes.⁵ Progressive weight-bearing activities, such as walking, are routinely recommended during rehabilitation to facilitate return to normal function. Not all patients are capable of full weight-bearing activity in the early postoperative period and assistive devices (ADs), such as walkers, crutches, and canes, are routinely employed. An opportunity to enhance early TKA rehabilitation exists with devices that allow functional gait training while modifying weight-bearing forces across the joint. Assistive devices, hydrotherapy (walking in water),^6,7 and lower body positive-pressure chambers⁸ can reduce the forces at the knee during weight-bearing exercise.

Lower body positive-pressure devices have been extensively studied in physiological response of healthy humans;^9-12 in disease states such as cerebral palsy¹³ and obesity;¹⁴ and in other postoperative orthopedic conditions, such as anterior cruciate ligament reconstruction, meniscectomy,⁸ microfracture,¹⁵ TKA,¹⁶ and Achilles tendon repair.¹⁷ These studies demonstrate that a lower body positive-pressure treadmill is associated with minimal cardiovascular effect while producing a significant decrease in ground reaction forces without altering gait kinematics.

We postulated that an anti-gravity treadmill may be safe and effective for gait training during rehabilitation following TKA. The primary objective was to determine the safety and feasibility of using the AlterG^® Anti-Gravity Treadmill^® device for postoperative gait training during rehabilitation following TKA. The secondary objective was to determine the effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on subjective patient outcomes assessed by Knee Injury and Osteoarthritis Outcome Score (KOOS), mobility assessed by the Timed Up and Go test (TUG), and pain assessed by a Numerical Rating Scale (NRS) to conduct a power analysis to determine sample sizes for efficacy studies based on these preliminary findings.

MethodsParticipants/Patient Enrollment and Study Overview

After signing an Institutional Review Board-approved consent, 30 patients were enrolled, and TKA surgeries were performed by 1 of 5 surgeons at 1 hospital. To be enrolled in the study, subjects must have (1) had a unilateral primary TKA, (2) been discharged from the hospital to home (not to a skilled nursing facility), (3) had only 3 to 4 home physical therapy (PT) sessions, (4) agreed to further outpatient PT at a single site, and (5) agreed to complete patient questionnaires. Exclusion criteria included (1) inability to meet inclusion criteria, (2) gross musculoskeletal deformity, (3) uncontrolled chronic or systemic disease, and (4) inability to follow instructions because of mental impairment, substance abuse, or addiction. Home PT was conducted for 3 to 4 sessions after surgery, and outpatient PT was continued at the study site per protocol for 4 weeks; subjects were asked to return for follow-up 3 months postoperatively. Patients were randomized on the first day of their outpatient PT to either a land-based (control) or an anti-gravity-based group using the AlterG Anti-Gravity Treadmill (AlterG group) gait training during outpatient PT sessions. Patients attended outpatient PT 2 days per week for 4 weeks for a total of 8 sessions. Therapy sessions lasted 45 to 60 minutes and included manual therapy, gait training, and therapeutic exercises/activities. The KOOS^18,19 and TUG²⁰ scores were evaluated at baseline (ie, first therapy session), end of physical therapy (EOPT) (ie, at final therapy session), and end of study (EOS) (ie, 3 months postoperatively). The NRS for pain was evaluated at baseline and at EOPT. Physical therapists were questioned for satisfaction with the anti-gravity rehabilitation protocol at EOPT.

Physical Therapy Protocols

All patients were treated consistently by 1 of 5 physical therapists at 1 outpatient setting; physical therapists averaged 11 years of experience in treating orthopedic conditions. Care was delivered in accordance with professional standards and the therapist’s assessment of medical necessity. Considerations included, but were not limited to, overall general health, any medical comorbidity, support system, and an ongoing assessment of ROM, strength, pain, and functional status. Each PT session started with a 5- to 10-minute warm-up on a standard cycle ergometer and was followed by manual therapy, gait training (land-based vs anti-gravity), therapeutic exercises/activities, and treatment modalities.

The time spent, activities selected, and modalities or physical agents chosen during the PT session were based on the patient’s needs and progress toward his/her functional goals. Manual therapy techniques consisted of soft-tissue mobilization, passive ROM, joint mobilization, passive stretching, scar mobilization, manual resistive exercises, and proprioceptive neuromuscular facilitation techniques. Therapeutic exercises/activities consisted of lower extremity resistance exercises (weight bearing and non-weight bearing), ROM exercises, stretching, balance, stair training, agility, activities of daily life (ADL) training, and a comprehensive home exercise program. Modalities or physical agents used during this study included moist hot packs, cold packs, ultrasound, electrical stimulation, and Kinesio Tape. Physical agents were incorporated into the individual’s plan of care based on medical necessity when deemed appropriate by the treating therapist. The exercise prescription was based on an individual’s status and tolerance and the number of sets and repetitions were based on fatigue.

Gait Training

The patients were randomized (1:1) to either land-based or anti-gravity gait training. For the control group, land-based gait training was performed with or without an appropriate AD and appropriate assistance, tactile cueing, and verbal cueing from a physical therapist. Duration (minutes) and gait-training progression were dependent on the participant’s functional goals, pain level (assessed throughout treatment), and level of fatigue. For the AlterG group, gait training was performed in the AlterG Anti-Gravity Treadmill, M320 (Alter-G; Figure 1). On day 1, the AlterG pressure chamber was set to allow only 50% of the patient’s body weight to be transmitted to the treadmill floor, and speed was controlled by the patient according to his/her comfort level. The percentage of body weight was adjusted to allow for a safe and normalized gait pattern with a pain level no greater than 5 (0 to 10 scale) throughout the PT session. A report card was recorded at each PT session, including body-weight setting (%), speed (miles per hour), incline (%), and duration (minutes) (Figure 2). For subsequent visits, the body-weight setting was started from the end point of the previous session.

Data Collection and Analysis

SPSS version 12.0 (SPSS Inc.) was used for all analyses, and an alpha level of .05 determined statistical significance when comparing group differences. The safety and feasibility of the anti-gravity (AlterG) vs land-based (control) gait training was assessed by the presence (or absence) of adverse events (AEs) and complications, and the date the patient discontinued use of his/her AD. A chi-square test was used to assess differences between control and AlterG groups regarding patient discontinuance of an AD. Additionally, for patients randomized to AlterG, a report card summarized means and frequencies for body weight, speed, incline, and duration. At EOPT, the frequency of therapists who were satisfied with the AlterG Anti-Gravity Treadmill as part of the rehabilitation protocol was reported. The preliminary effects of gait training (land-based vs anti-gravity) during postoperative rehabilitation on functional outcomes (subjective patient outcomes assessed by KOOS, mobility assessed by the TUG test, and pain assessed by a NRS) were evaluated by independent sample t tests. Paired sample t tests were used to compare each of the functional outcomes at EOPT or EOS to the baseline value.

Results

Of the 30 patients enrolled, 29 (96.7%; 29/30) patients completed the study; 1 patient, who could not complete all PT sessions because of medical and transportation issues, was excluded. The remaining 29 patients comprised the study population (control = 15; AlterG = 14). All patients were compliant with PT protocols.

Patient demographics were similar between the control and AlterG groups (Table 1). The control group comprised 9 women (60%; 9/15) and 6 men (40%; 6/15), age 69.9 ± 7.8 years and a body mass index of 28.8 ± 4.2. Similarly, the AlterG group comprised 7 women (50%; 7/14) and 7 men (50%; 7/14), age 66.5 ± 7.8 years and a body mass index of 28.4 ± 5.2.

At the baseline PT visit, patients in the control and AlterG groups had similar KOOS, TUG, and NRS scores. At baseline, mean KOOS for symptoms, pain, sports/recreation, ADL, and quality of life were 52.7, 52.9, 22.7, 64, and 31.8, respectively, although 50% of patients did not complete the sports/recreation subset of the KOOS. In addition, the mean time to complete the TUG test was 14.5 seconds, which was within the normal limits for disabled patients. This was slightly longer than normal mobility (TUG <10 seconds),20 but patients had relatively low levels of pain (mean NRS = 2.5, on a scale of 0-11).

All patients completed the PT protocols without indication of injury or AEs related to their operative knee. Three patients (10.3%; 3/29) experienced a deep venous thromboembolism (DVT), 2 in the control group (13.3%; 2/15), and 1 in the AlterG group (7.1%; 1/14). Venous thromboembolism protocol of enoxaparin 30 mg twice daily while in the hospital and enoxaparin 40 mg once daily for 10 days after discharge was followed for all patients.

Overall, more than half of patients (55.2%; 16/29) discontinued their AD during the 4-week PT period, with the remaining discontinuing prior to EOPT (24.1%; 7/29) or after EOPT (20.7%; 6/29). No statistically significant differences were found between the control and AlterG groups regarding discontinuance of AD.

Among those randomized to the AlterG group, all patients performed within the protocol established for the device for body-weight setting, treadmill speed, and duration of walking. The average body-weight treadmill setting increased by ~30% over the treatment period, from 55% at baseline to 84% at EOPT. The average speed increased by ~70%, from 1.6 mph at baseline to 2.7 mph at EOPT. The mean duration of AlterG use increased by ~75%, from 7.2 minutes at baseline to 12.7 minutes at EOPT. All physical therapists (100%) reported satisfaction with the AlterG for use in early postoperative rehabilitation and reported that patients’ treatment progressed positively.

While functional outcomes (KOOS, TUG, or NRS) did not vary with the type of gait training (P > .2 for land-based vs anti-gravity), functional outcomes improved over time (all P < .01 from baseline to EOPT and all P < .01 from baseline to EOS).

The KOOS scores improved from baseline to EOPT and from baseline to EOS (ie, 3-month follow-up visit) for both treatment groups (Figure 3). More patients completed the sports/recreation portion of the KOOS scores at EOPT and EOS compared to baseline. Forty-three percent and 25% of patients did not complete KOOS sports/recreation questions at EOPT and EOS, respectively, compared to 50% at baseline. This suggests that patients were improving to a level where sports/recreation scores were more applicable than directly after TKA surgery. The TUG scores had the greatest improvement from baseline to EOPT, with a decrease in time of 5 seconds and 7 seconds for the control and AlterG groups, respectively, and slight improvement from EOPT to EOS, with a decrease in time of 1 second and 2 seconds for the control and AlterG groups, respectively (Table 2). By the EOS, the values for the TUG tests for both treatment groups were within normal (<10 seconds) range.²⁰ The NRS scores improved from baseline to EOPT with a score of 1 ± 1 in both control and AlterG groups.

Using these preliminary efficacy results, a post-hoc power analysis (α = .05 and 1β = 80%) was performed with the ADL domain of KOOS as the primary endpoint. Based on a standard deviation of 20 points and an effect size of 5 points, the sample size was estimated to be N = 250 per treatment group.

Discussion

We conducted a pilot study to assess, primarily, the feasibility and safety, and, secondarily, the efficacy, of a lower body positive-pressure treadmill for rehabilitation of patients after TKA. This small study showed that use of the AlterG Anti-Gravity Treadmill was not only safe and feasible during postoperative TKA rehabilitation, but also was well tolerated by patients and was rated highly satisfactory by physical therapists. Patients who used AlterG during gait training improved functionally (in terms of KOOS, TUG, and NRS) after 8 treatment sessions compared to baseline. However, there were no statistical differences between groups (control vs AlterG). Thus, these results suggest that an anti-gravity device for gait training may be a useful adjunct for postoperative TKA rehabilitation, but further studies are needed to determine the efficacy of anti-gravity compared to traditional land-based gait training.

The study of rehabilitation protocols during postoperative PT involved consideration of a number of issues. First, differences in functional outcomes compared to traditional rehabilitation could not be detected in this study because of the small number of patients, but the patients treated with anti-gravity gait training showed improvement in functional outcomes over time and did not report any added complications. Given that the primary outcome of this study was safety and feasibility, these added efficacy results are supplemental and useful in helping to plan studies. Second, the functional outcomes used to measure the efficacy of the anti-gravity treadmill may not be sensitive enough to detect differences between rehabilitation protocols. Use of a treadmill to measure speed improvement, endurance, and tolerance in both groups could be valuable in future studies. More studies may need to refine characteristics that are important to postoperative rehabilitation success, and quantitative and subjective measures that must be defined.

The results reported here using an anti-gravity treadmill for postoperative TKA rehabilitation support the safety and feasibility that has been reported in other orthopedic rehabilitation settings. Anti-gravity treadmills, which have been used to study patients after meniscectomy or anterior cruciate ligament reconstruction8 and Achilles repair,¹⁷ have demonstrated predictable decreases in ground reaction forces with increasing positive-pressure unweighting, reductions in pain with ambulation, and allowance of earlier institution of walking and jogging during rehabilitation.¹⁷

Patient safety is an important attribute for any postoperative rehabilitation protocol, especially in an elderly population undergoing major surgery. One of our important goals was to assess the safety of AlterG. We noted no AEs attributable to the device, which was supported by work indicating no adverse impact on systemic cardiovascular parameters in a similar lower body positive-pressure environment.⁹ Although 3 patients (10%) developed symptomatic DVT, there were no differences between the groups in the incidence of DVT. Use of an anti-gravity treadmill has also been examined for cardiovascular responses in TKA patients. In a study of 24 adults with TKA, researchers found that anti-gravity support allowed TKA patients to walk at faster speeds and tolerate greater inclines with lower heart rate, blood pressure, and oxygen consumption.²¹ With respect to efficacy of the rehabilitation intervention, we demonstrated significant improvements in all functional outcomes in both groups but no differences between the study groups. We concluded that AlterG was at least as effective as standard therapy in this small cohort. TKA is a very successful procedure, and the improvement in pain and function after surgery is fairly dramatic in most patients, regardless of specific rehabilitation protocols. Therefore, the substantial improvement in clinical outcomes may overshadow any enhanced benefits of the anti-gravity treadmill. Further investigations into the efficacy of AlterG are needed in a larger cohort to determine if this type of treatment is more beneficial than traditional land-based gait training.

Standard scoring systems such as KOOS, TUG, and NRS may not be sensitive enough to detect differences between treatment groups with small sample sizes. Given the results of the post hoc power analysis, a large number of patients (N = 250/group) would be necessary to detect any potential difference in clinical outcomes between the 2 groups. Larger studies are required to answer relevant questions, and additional outcome measures may be needed to detect differences between treatment groups. Relevant questions include whether earlier institution of the anti-gravity device during the immediate TKA postoperative period would be beneficial compared to standard postoperative PT, and whether PT enhanced with the anti-gravity device has incremental benefit in functional outcomes and in time to reach those goals. Finally, given the present attention to healthcare expenses, a cost-benefit analysis of anti-gravity device treatment vs traditional PT would be useful. Once the patient has become familiar with the function of an anti-gravity treadmill, gait therapy could proceed without the direct intervention of the therapist, potentially improving efficient delivery of rehabilitation services.

Studying the effect of different postoperative rehabilitation protocols after orthopedic surgeries can be challenging. In a large (N > 350) randomized controlled trial to study the effect of ergometer cycling after hip and knee replacement, patients who used the cycle ergometer had a higher Western Ontario and McMaster Universities Arthritis Index and greater satisfaction than those who did not after hip arthroplasty, but not after TKA.²² Improvements in muscular coordination and proprioception with the cycle ergometer may have been offset by increases in edema, joint effusion, and pain from the loading of the joint and the relatively fast rate of cycling compared to passive motion or ambulation. While many therapists and surgeons advocate cycling for rehabilitation after knee surgery, the need remains for a better definition of an optimal TKA rehabilitation program. A study of 82 patients comparing early progressive strength training to no early strength training showed no difference in the 6-minute walk test at 8 weeks.²³ A systematic review of progressive resistance training (PRT) found that although postoperative PRT is safe and feasible, the methodological quality of existing studies is too low to allow conclusions regarding its efficacy.²⁴ Gait training in an environment where weight-bearing loads can be closely controlled, monitored, and individualized may be an ideal methodology to enhance rehabilitation and return to function for knee replacement surgery.

This current study showed that the use of AlterG as an adjunct for postoperative rehabilitation is safe, accepted by patients and therapists, and leads to clinical functional outcomes that are at least as good as traditional postoperative TKA rehabilitation. We conclude that AlterG demonstrates utility and a potential for innovation in TKA rehabilitation.

Hinge knee arthroplasty was introduced in the 1950s.¹ All 4 major ligaments were replaced by the hinge, which provided stabilization while allowing sagittal plane motion. Its goal was stability, not replication of normal kinematics. The addition of methyl methacrylate cement improved fixation and allowed surface design modifications that addressed normal articular motion. Implants such as the Gunston Polycentric,² the Duocondylar,³ and the Geometric⁴ resurfaced the medial and lateral compartments of the knee while preserving the cruciate ligaments. The implants were subject to greater translational forces without the hinge and loosening became a major problem despite the advances in cementing. It became evident in the 1970s that preservation of the cruciates complicated the procedure. Cruciate resection simplified the operation and allowed improved fixation. The ICLH prosthesis resected the cruciates and used the articular surface design to give stability to the knee.^5,6 The total condylar prosthesis had a “tibial” imminence that mimicked the shape of the tibial surface but also sacrificed both of the cruciate ligaments (Figure 1).

Designers recognized that the cruciate ligaments affected knee kinematics; however, they elected to sacrifice the anterior cruciate ligament (ACL) for surgical simplicity and implant longevity.⁶ In the early 1980s, both the cruciate-retaining (CR) total knee arthroplasty (TKA) (Figure 2) and posterior-stabilized (PS) TKA (Figure 3) designs addressed the posterior cruciate ligament (PCL) function. The PCL was preserved in the “cruciate-retaining” TKA, substituted in the “posterior-stabilized” TKA using a cam-post mechanism. The CR TKA designers believed that PCL preservation produced a more balanced knee with a more anatomical result, a more normal joint line, and better function, especially on stair climbing. The PS TKA designers admitted the value of posterior stabilization but argued that it was too difficult to consistently save the PCL in all cases, and that the PS knee was easier for surgeons to implant with more reliable roll back.⁷

The Geometric knee was developed in the 1970s to retain both cruciate ligaments.⁴ Unfortunately, it created a kinematic conflict by using a constrained articular surface design that prevented the motion required by the cruciate ligaments. This conflict resulted in tibial loosening and early failures. The compromised results decreased interest in the bicruciate-retaining (BCR) TKA designs, allowing the CR TKA and PS TKA designs to flourish for the next 20 years with little or no attempts to retain the ACL.

In the 1980s the BCR TKA design was pursued by Townley⁸ and Cartier.⁹ Townley⁸ believed that cruciate resection was a concession to “improper joint synchronization”⁸ and Cartier⁹ thought that cruciate preservation permitted more normal proprioception.⁹ Unlike prior BCR TKA designs, the mid-term clinical results were equal to or better than the standard CR TKA or PS TKA of the time, and 9- to 11-year follow-up demonstrated comparable outcomes.⁸ While these results highlighted the possibility of a BCR TKA, the surgical technique and failures of the Geometric knee discouraged surgeons from pursuing the BCR TKA.

Interest in cruciate-preserving knee arthroplasty returned with partial knee replacements, with patients reporting more normal proprioception and motion.¹⁰ The techniques became more popular with the introduction of the minimally invasive surgeries in the early 2000s and cruciate ligament preservation became a more interesting concept.^11,12 Some surgeons preserved the cruciates by using separate implants for the medial, lateral, and patellofemoral surfaces.¹⁰ These results were acceptable for the time but required considerable surgical talent and did not report 20-year results similar to the CR and PS knees.

Most prosthetic designs attempt to copy the normal knee anatomy. Using fluoroscopic studies and computer analysis, designers began to investigate the motion (or kinematics) of the normal knee and realized that despite the fact the TKA looked like the human knee, the designs were not kinematically correct.¹³

Although TKA successfully treats pain secondary to degenerative joint disease, many patients are unable to return to their prior level of function, with up to 20% reporting dissatisfaction with their level of activity.¹⁴ The observed differences in kinematics between a normal knee and a TKA may explain part of this discrepancy.

Normal Knee Motion

The tibiofemoral articulation in a normal knee follows a reproducible pattern of motion as the knee moves from extension to flexion. The lateral femoral condyle (LFC) translates posteriorly with a combination of rolling and sliding motion, while the medial femoral condyle (MFC) has minimal posterior translation and thus acts as a pivot for knee motion. The MFC is larger, less curved, and has a biphasic shape with 2 distinct radiuses of curvature that correspond to an “extension” and “flexion” facet. The transition between the MFC facets occurs at approximately 30° of flexion, whereby the contact point transfers posteriorly with little condylar translation.^15-17 In contrast, the LFC is smaller, has a single radius of curvature, and gradually translates posteriorly throughout flexion. Static magnetic resonance imaging of the knee from 0° to 120° shows an average of 19 mm posterior translation for the LFC and 2 mm for the MFC.^15-20

In deep flexion, beyond 130°, posterior translation continues for both condyles. The LFC experiences enough excursion to cause loss of joint congruity and partial posterior subluxation.^19,20 The MFC shows little additional posterior translation, yet it too loses joint congruity through condylar lift-off. Contact between the posterior horn of the medial meniscus and the posterior femoral condyle limits further flexion.^16,21

The difference in motion between the condyles leads to internal tibial rotation during flexion. The initial 10° of knee flexion produces 5° of internal rotation, and an additional 15° of internal tibial rotation occurs throughout the remainder of knee flexion.

Fluoroscopic imaging with computed tomography (CT)- or magnetic resonance (MR)-based modeling has shown the dynamic in vivo relationship of the tibiofemoral joint. Studies have confirmed significantly greater LFC posterior translation as compared to the MFC;²² however, in vivo studies have also shown notable variability in articular rotation and translation based on activity. This highlights the role of ligamentous tension and muscle contraction in kinematics.^21-23

The ACL in TKA

The majority of current TKA designs sacrifice the ACL without substituting for its function. The loss of the ACL has significant effects upon the kinematics of the knee.

The ACL is composed of 2 bundles, the anteromedial and posterolateral bundles, which originate on the LFC and insert broadly onto the tibial intercondylar eminence. Its primary role is to resist anterior tibial translation, particularly from 0° to 30° of flexion, which corresponds to the peak quadriceps force that pulls the tibia anteriorly.²⁴ ACL deficiency causes anterior tibial translation during early flexion and abnormal internal tibial rotation.^25-27 ACL deficient knees demonstrate a posterior femoral position in full extension, and increased MFC translation during knee flexion.^28-32

The role of the ACL in knee arthroplasty has been evaluated by comparing unicompartmental knee arthroplasty (UKA) with TKA, as a reflection of ACL preserving vs sacrificing procedures.^33-35 Sagittal plane translation is similar between UKA and normal knees,^33,34 while the CR TKA and PS TKA designs show anterior tibia subluxation in full extension.^33-35 The difference between UKA and TKA is greatest in extension, corresponding to the ACL functional range. These findings highlight kinematic similarities between TKA designs and the ACL deficient knee.

The majority of UKAs demonstrate near-normal kinematics. A small percentage of the study group demonstrated aberrant anterior tibial motion, highlighting a concern over ACL attenuation with time. Additionally, studies that evaluate the ACL in osteoarthritic knees have questioned the baseline integrity of the ACL.36 Yet the long-term outcomes in UKA design have shown preservation of kinematics due to intact cruciates.³⁷

The PCL in TKA

Because the majority of TKA designs sacrifice the ACL, the classic debate has focused on the utility of the native PCL. Both the CR and PS TKA are designed to offer posterior stabilization; however, kinematic studies have demonstrated notable differences.^38,39

The CR TKA design relies on the PCL to resist posterior sag and to prevent the hamstring musculature from pulling the tibia posteriorly during flexion. Studies have shown paradoxical anterior translation of both femoral condyles during flexion, particularly on the medial side of the knee.⁴⁰ There is also increased variability in femoral rollback. It is unclear whether the PCL can function normally in the absence of the ACL, which causes the PCL to adapt a less anatomic vertical position. The PCL may also be unable to function significantly without the ACL because of pre-existing degenerative histological changes.⁴¹

The PS TKA utilizes a cam-post mechanism for posterior stabilization. In contrast to normal knee kinematics, this mechanism creates equal MFC and LFC posterior translation, 8 mm on average at 90° flexion.⁴⁰ The equivalent translation in PS designs contributes to decreased internal tibial rotation and an increased polyethylene wear at the post.

Role of Surface Geometry

The articular geometry of the knee plays an important role in normal knee kinematics. Initial TKA designs used a femoral component with a single radius of curvature for both femoral condyles.⁴²Current TKA designs that match the femoral component to the native femoral anatomy, by differing the medial and lateral condyle geometry, have demonstrated kinematics that better resemble a native knee.⁴³ Additional changes to the radius of curvature along the posterior facet of the femoral condyles may reduce impingement during deep flexion. These “high flex” designs have demonstrated equivalent range of motion in some studies⁴⁴ and improved weight-bearing motion in others.⁴⁵ Surface geometry is important but is not the entire answer to kinematics.

Advances in TKA Design

Knee motion is guided by multiple factors, including the tibiofemoral articular geometry, the surrounding soft tissue tension, and muscle tone. Bicruciate-substituting (BCS) TKA and BCR TKA are forms of evolution from the CR and PS TKA and attempt to respect the function of both cruciate ligaments and provide better kinematics.

The BCS TKA utilizes a modified cam-post articulation to provide both anterior and posterior stabilization (Figure 4).⁴⁶ The surgical approach remains the same and the implant geometry affects the motion. The BCS TKA design demonstrates femoral rollback at 90° with an average of 14 mm for the MFC and 23 mm for the LFC, and 10° internal tibial rotation.^46,47 Additionally, it provides increased sagittal stability during early flexion and an improved pivot shift (indicating improved anterior stabilization).

The BCR designs preserve both cruciates and provide anterior and posterior stabilization. Fluoroscopic imaging has demonstrated contact points in full extension, and posterior rollback at 90° flexion that more closely replicates the normal knee.⁴⁸

Design and Surgical Techniques for Bicruciate Knee Replacements

If all of the ligaments are preserved, the TKA surfaces must allow motion to be driven by the ligaments in combination with the surfaces alone. The femur can be designed anatomically with asymmetric condyles. The femoral box must allow for preservation of the tibial bone island without impinging upon the cruciate ligaments. The tibial surface must be minimally constrained with concavity medially and convexity laterally.

The bone island preservation does not permit a single-piece tibial polyethylene insert. Therefore, the inserts will replicate the UKA designs (Figure 5). The knee should allow greater range of motion with the possibility of heel to buttocks contact. This increased motion will lead to greater roll back of the femur on the tibia and can lead to subluxation of the femoral runner off of the tibial surface on the lateral side, mimicking the normal knee. This subluxation is desirable but may lead to increased wear of the polyethylene on the lateral side of the knee.

The instruments should be specific for the design but must also be user-friendly. The 2 major issues with the surgery are balancing the knee in full extension and flexion, and preservation of the tibial bone island. The preexisting knee deformity should be <10° in all planes to limit the amount of collateral ligament releases. The collaterals must be balanced in a similar fashion to the standard TKA. Flexion contracture can be treated with posterior capsular release around the cruciates or with an increased distal femoral resection (2 mm at the maximum).

It is important to size the femur correctly because it will be difficult to adjust the flexion gap on the tibial side. A 9-mm posterior medial femoral condyle resection is a reasonable guide if the condyle is not atrophic. However, the exact resection thickness will be implant-specific and should be correlated with the dimensions of the prosthesis being implanted. The tibial bone island must be properly rotated with respect to the center line (Akagi’s line)⁴⁹ and must not be undercut. The tibial instrument should include pins or blocks to prevent the sawblades from undercutting the island (Figure 6), as undermining leads to fracture in full extension. If undermining occurs, it may be possible to place a cancellous screw through the island and still preserve the ligaments. The integrity of the island is best tested by bringing the knee to full extension and checking for liftoff of the bone. If there is significant compromise of the island, the bone should be resected and either a CR or PS TKA can be implanted. Della Valle and colleagues⁵⁰ reported a 9.2% incidence (11 of 119 cases) of bone island fracture in their early experience with a BCR TKA and improved this to 1.9% (5/258 cases) after reassessing their technique.

The gap tension should be evaluated either with traditional spacer blocks or with tensioning devices on the medial and lateral side of the knee after the tibial resections are completed. The polyethylene inserts are anatomically different. It may be possible to vary the thickness from medial to lateral, but not in excess of 2 mm.

As the BCR surgical techniques evolve, the balancing and tibial resection may be refined through specialized instrumentation. Such “smart instruments” that incorporate gyros may expedite tibial alignment, and sensor devices may assist with gap balancing. Haptic surgical robotic guides may assist in the tibial resection, facilitating bone island preservation by avoiding any possibility of undermining. At present these assistive aides are not necessary for the operation but may play a future role.

Clinical Results of Knee Arthroplasties

The results of knee replacements improved steadily from the 1970s through the 1990s. The scoring systems were somewhat limited and there was little data on the perception of the patients. The prosthetic designs stabilized at the end of the 1990s with only minor modifications since the year 2000. The 20-year results show similar findings for both the CR and the PS designs. There is little evidence to suggest a clinical correlation with the observed kinematic differences between CR and PS TKA designs.^40,51-58 Multiple studies have demonstrated equivalent range of motion^38,39,59 and subjective outcome measures (Table 1).⁶⁰ A randomized prospective trial that compared kinematics and functional scores between the 2 designs failed to observe significant differences in function despite differences in kinematics.⁴⁶ Equivalence in clinical outcome was further supported by a Cochrane Review meta-analysis that evaluated 1810 patients in 17 selected studies.⁶¹ The Knee Society scores have all been in the 92% to 95% ratings with survivals between 90% and 95%.

However, only 80% to 90% of patients are fully satisfied with their implants. The reasons for the dissatisfaction include unexplained anterior knee pain, stiffness, unexplained swelling, loss of range of motion, changes in proprioception, and loss of preoperative functions.¹⁴

The mid-term results of the BCR knees that were performed in the 1980s showed similar results to the CR and PS knees. Townley⁸ reported excellent clinical results with only 2% loosening at 2 to 11 years after surgery. Cloutier and colleagues9 reported 95% survival with improved proprioception at 9 to 11 years after surgery(Table 2).^62,63

Studies comparing traditional TKA designs with cruciate preserving designs, both UKA and BCR, have found differences in subjective outcomes.^62,64 Comparison of UKA and TKA in the same patient demonstrated significant preference for UKA, particularly with stair-climbing.⁶⁵ Similarly, comparison between BCR and PS TKA or CR TKA demonstrated preference for BCR in 85% of patients.⁶²

The new BCR knee designs have just started to come to the market.⁵⁰ The surgical techniques are much improved over the 1980s and cruciate preservation is certainly much easier now. The new designs can produce full range of motion with kinematics that are almost identical to the normal knee in the cadaver laboratory and in computer analyses. These designs certainly should have a similar 20-year survival to the original BCR knees. However, the critical evaluation will be the patient satisfaction scores. With greater motion, better kinematics, and more precise balancing the scores would improve with these designs.

Conclusion

The cruciate ligaments of the knee are central to control of the motion of the normal knee. TKA is a successful operation with at least a 40- to 50-year history. The techniques have continued to develop but 15% to 20% of patients are dissatisfied with the results.¹⁴ Evaluations of the prostheses are more sophisticated and kinematics appears to have a central position in the evaluation. If the knee is to move more anatomically correctly, all of the ligaments must be preserved. Proprioception certainly plays a role in the patient’s judgment of the result. History has shown that a BCR knee can be implanted with good mid-term results and it should certainly be possible to build on these results and design a knee that will incorporate all of the ligaments with full range of motion and increased levels of activity.

Hinge knee arthroplasty was introduced in the 1950s.¹ All 4 major ligaments were replaced by the hinge, which provided stabilization while allowing sagittal plane motion. Its goal was stability, not replication of normal kinematics. The addition of methyl methacrylate cement improved fixation and allowed surface design modifications that addressed normal articular motion. Implants such as the Gunston Polycentric,² the Duocondylar,³ and the Geometric⁴ resurfaced the medial and lateral compartments of the knee while preserving the cruciate ligaments. The implants were subject to greater translational forces without the hinge and loosening became a major problem despite the advances in cementing. It became evident in the 1970s that preservation of the cruciates complicated the procedure. Cruciate resection simplified the operation and allowed improved fixation. The ICLH prosthesis resected the cruciates and used the articular surface design to give stability to the knee.^5,6 The total condylar prosthesis had a “tibial” imminence that mimicked the shape of the tibial surface but also sacrificed both of the cruciate ligaments (Figure 1).

Designers recognized that the cruciate ligaments affected knee kinematics; however, they elected to sacrifice the anterior cruciate ligament (ACL) for surgical simplicity and implant longevity.⁶ In the early 1980s, both the cruciate-retaining (CR) total knee arthroplasty (TKA) (Figure 2) and posterior-stabilized (PS) TKA (Figure 3) designs addressed the posterior cruciate ligament (PCL) function. The PCL was preserved in the “cruciate-retaining” TKA, substituted in the “posterior-stabilized” TKA using a cam-post mechanism. The CR TKA designers believed that PCL preservation produced a more balanced knee with a more anatomical result, a more normal joint line, and better function, especially on stair climbing. The PS TKA designers admitted the value of posterior stabilization but argued that it was too difficult to consistently save the PCL in all cases, and that the PS knee was easier for surgeons to implant with more reliable roll back.⁷

The Geometric knee was developed in the 1970s to retain both cruciate ligaments.⁴ Unfortunately, it created a kinematic conflict by using a constrained articular surface design that prevented the motion required by the cruciate ligaments. This conflict resulted in tibial loosening and early failures. The compromised results decreased interest in the bicruciate-retaining (BCR) TKA designs, allowing the CR TKA and PS TKA designs to flourish for the next 20 years with little or no attempts to retain the ACL.

In the 1980s the BCR TKA design was pursued by Townley⁸ and Cartier.⁹ Townley⁸ believed that cruciate resection was a concession to “improper joint synchronization”⁸ and Cartier⁹ thought that cruciate preservation permitted more normal proprioception.⁹ Unlike prior BCR TKA designs, the mid-term clinical results were equal to or better than the standard CR TKA or PS TKA of the time, and 9- to 11-year follow-up demonstrated comparable outcomes.⁸ While these results highlighted the possibility of a BCR TKA, the surgical technique and failures of the Geometric knee discouraged surgeons from pursuing the BCR TKA.

Interest in cruciate-preserving knee arthroplasty returned with partial knee replacements, with patients reporting more normal proprioception and motion.¹⁰ The techniques became more popular with the introduction of the minimally invasive surgeries in the early 2000s and cruciate ligament preservation became a more interesting concept.^11,12 Some surgeons preserved the cruciates by using separate implants for the medial, lateral, and patellofemoral surfaces.¹⁰ These results were acceptable for the time but required considerable surgical talent and did not report 20-year results similar to the CR and PS knees.

Most prosthetic designs attempt to copy the normal knee anatomy. Using fluoroscopic studies and computer analysis, designers began to investigate the motion (or kinematics) of the normal knee and realized that despite the fact the TKA looked like the human knee, the designs were not kinematically correct.¹³

Although TKA successfully treats pain secondary to degenerative joint disease, many patients are unable to return to their prior level of function, with up to 20% reporting dissatisfaction with their level of activity.¹⁴ The observed differences in kinematics between a normal knee and a TKA may explain part of this discrepancy.

Normal Knee Motion

The tibiofemoral articulation in a normal knee follows a reproducible pattern of motion as the knee moves from extension to flexion. The lateral femoral condyle (LFC) translates posteriorly with a combination of rolling and sliding motion, while the medial femoral condyle (MFC) has minimal posterior translation and thus acts as a pivot for knee motion. The MFC is larger, less curved, and has a biphasic shape with 2 distinct radiuses of curvature that correspond to an “extension” and “flexion” facet. The transition between the MFC facets occurs at approximately 30° of flexion, whereby the contact point transfers posteriorly with little condylar translation.^15-17 In contrast, the LFC is smaller, has a single radius of curvature, and gradually translates posteriorly throughout flexion. Static magnetic resonance imaging of the knee from 0° to 120° shows an average of 19 mm posterior translation for the LFC and 2 mm for the MFC.^15-20

In deep flexion, beyond 130°, posterior translation continues for both condyles. The LFC experiences enough excursion to cause loss of joint congruity and partial posterior subluxation.^19,20 The MFC shows little additional posterior translation, yet it too loses joint congruity through condylar lift-off. Contact between the posterior horn of the medial meniscus and the posterior femoral condyle limits further flexion.^16,21

The difference in motion between the condyles leads to internal tibial rotation during flexion. The initial 10° of knee flexion produces 5° of internal rotation, and an additional 15° of internal tibial rotation occurs throughout the remainder of knee flexion.

Fluoroscopic imaging with computed tomography (CT)- or magnetic resonance (MR)-based modeling has shown the dynamic in vivo relationship of the tibiofemoral joint. Studies have confirmed significantly greater LFC posterior translation as compared to the MFC;²² however, in vivo studies have also shown notable variability in articular rotation and translation based on activity. This highlights the role of ligamentous tension and muscle contraction in kinematics.^21-23

The ACL in TKA

The majority of current TKA designs sacrifice the ACL without substituting for its function. The loss of the ACL has significant effects upon the kinematics of the knee.

The ACL is composed of 2 bundles, the anteromedial and posterolateral bundles, which originate on the LFC and insert broadly onto the tibial intercondylar eminence. Its primary role is to resist anterior tibial translation, particularly from 0° to 30° of flexion, which corresponds to the peak quadriceps force that pulls the tibia anteriorly.²⁴ ACL deficiency causes anterior tibial translation during early flexion and abnormal internal tibial rotation.^25-27 ACL deficient knees demonstrate a posterior femoral position in full extension, and increased MFC translation during knee flexion.^28-32

The role of the ACL in knee arthroplasty has been evaluated by comparing unicompartmental knee arthroplasty (UKA) with TKA, as a reflection of ACL preserving vs sacrificing procedures.^33-35 Sagittal plane translation is similar between UKA and normal knees,^33,34 while the CR TKA and PS TKA designs show anterior tibia subluxation in full extension.^33-35 The difference between UKA and TKA is greatest in extension, corresponding to the ACL functional range. These findings highlight kinematic similarities between TKA designs and the ACL deficient knee.

The majority of UKAs demonstrate near-normal kinematics. A small percentage of the study group demonstrated aberrant anterior tibial motion, highlighting a concern over ACL attenuation with time. Additionally, studies that evaluate the ACL in osteoarthritic knees have questioned the baseline integrity of the ACL.36 Yet the long-term outcomes in UKA design have shown preservation of kinematics due to intact cruciates.³⁷

The PCL in TKA

Because the majority of TKA designs sacrifice the ACL, the classic debate has focused on the utility of the native PCL. Both the CR and PS TKA are designed to offer posterior stabilization; however, kinematic studies have demonstrated notable differences.^38,39

The CR TKA design relies on the PCL to resist posterior sag and to prevent the hamstring musculature from pulling the tibia posteriorly during flexion. Studies have shown paradoxical anterior translation of both femoral condyles during flexion, particularly on the medial side of the knee.⁴⁰ There is also increased variability in femoral rollback. It is unclear whether the PCL can function normally in the absence of the ACL, which causes the PCL to adapt a less anatomic vertical position. The PCL may also be unable to function significantly without the ACL because of pre-existing degenerative histological changes.⁴¹

The PS TKA utilizes a cam-post mechanism for posterior stabilization. In contrast to normal knee kinematics, this mechanism creates equal MFC and LFC posterior translation, 8 mm on average at 90° flexion.⁴⁰ The equivalent translation in PS designs contributes to decreased internal tibial rotation and an increased polyethylene wear at the post.

Role of Surface Geometry

The articular geometry of the knee plays an important role in normal knee kinematics. Initial TKA designs used a femoral component with a single radius of curvature for both femoral condyles.⁴²Current TKA designs that match the femoral component to the native femoral anatomy, by differing the medial and lateral condyle geometry, have demonstrated kinematics that better resemble a native knee.⁴³ Additional changes to the radius of curvature along the posterior facet of the femoral condyles may reduce impingement during deep flexion. These “high flex” designs have demonstrated equivalent range of motion in some studies⁴⁴ and improved weight-bearing motion in others.⁴⁵ Surface geometry is important but is not the entire answer to kinematics.

Advances in TKA Design

Knee motion is guided by multiple factors, including the tibiofemoral articular geometry, the surrounding soft tissue tension, and muscle tone. Bicruciate-substituting (BCS) TKA and BCR TKA are forms of evolution from the CR and PS TKA and attempt to respect the function of both cruciate ligaments and provide better kinematics.

The BCS TKA utilizes a modified cam-post articulation to provide both anterior and posterior stabilization (Figure 4).⁴⁶ The surgical approach remains the same and the implant geometry affects the motion. The BCS TKA design demonstrates femoral rollback at 90° with an average of 14 mm for the MFC and 23 mm for the LFC, and 10° internal tibial rotation.^46,47 Additionally, it provides increased sagittal stability during early flexion and an improved pivot shift (indicating improved anterior stabilization).

The BCR designs preserve both cruciates and provide anterior and posterior stabilization. Fluoroscopic imaging has demonstrated contact points in full extension, and posterior rollback at 90° flexion that more closely replicates the normal knee.⁴⁸

Design and Surgical Techniques for Bicruciate Knee Replacements

If all of the ligaments are preserved, the TKA surfaces must allow motion to be driven by the ligaments in combination with the surfaces alone. The femur can be designed anatomically with asymmetric condyles. The femoral box must allow for preservation of the tibial bone island without impinging upon the cruciate ligaments. The tibial surface must be minimally constrained with concavity medially and convexity laterally.

The bone island preservation does not permit a single-piece tibial polyethylene insert. Therefore, the inserts will replicate the UKA designs (Figure 5). The knee should allow greater range of motion with the possibility of heel to buttocks contact. This increased motion will lead to greater roll back of the femur on the tibia and can lead to subluxation of the femoral runner off of the tibial surface on the lateral side, mimicking the normal knee. This subluxation is desirable but may lead to increased wear of the polyethylene on the lateral side of the knee.

The instruments should be specific for the design but must also be user-friendly. The 2 major issues with the surgery are balancing the knee in full extension and flexion, and preservation of the tibial bone island. The preexisting knee deformity should be <10° in all planes to limit the amount of collateral ligament releases. The collaterals must be balanced in a similar fashion to the standard TKA. Flexion contracture can be treated with posterior capsular release around the cruciates or with an increased distal femoral resection (2 mm at the maximum).

It is important to size the femur correctly because it will be difficult to adjust the flexion gap on the tibial side. A 9-mm posterior medial femoral condyle resection is a reasonable guide if the condyle is not atrophic. However, the exact resection thickness will be implant-specific and should be correlated with the dimensions of the prosthesis being implanted. The tibial bone island must be properly rotated with respect to the center line (Akagi’s line)⁴⁹ and must not be undercut. The tibial instrument should include pins or blocks to prevent the sawblades from undercutting the island (Figure 6), as undermining leads to fracture in full extension. If undermining occurs, it may be possible to place a cancellous screw through the island and still preserve the ligaments. The integrity of the island is best tested by bringing the knee to full extension and checking for liftoff of the bone. If there is significant compromise of the island, the bone should be resected and either a CR or PS TKA can be implanted. Della Valle and colleagues⁵⁰ reported a 9.2% incidence (11 of 119 cases) of bone island fracture in their early experience with a BCR TKA and improved this to 1.9% (5/258 cases) after reassessing their technique.

The gap tension should be evaluated either with traditional spacer blocks or with tensioning devices on the medial and lateral side of the knee after the tibial resections are completed. The polyethylene inserts are anatomically different. It may be possible to vary the thickness from medial to lateral, but not in excess of 2 mm.

As the BCR surgical techniques evolve, the balancing and tibial resection may be refined through specialized instrumentation. Such “smart instruments” that incorporate gyros may expedite tibial alignment, and sensor devices may assist with gap balancing. Haptic surgical robotic guides may assist in the tibial resection, facilitating bone island preservation by avoiding any possibility of undermining. At present these assistive aides are not necessary for the operation but may play a future role.

Clinical Results of Knee Arthroplasties

The results of knee replacements improved steadily from the 1970s through the 1990s. The scoring systems were somewhat limited and there was little data on the perception of the patients. The prosthetic designs stabilized at the end of the 1990s with only minor modifications since the year 2000. The 20-year results show similar findings for both the CR and the PS designs. There is little evidence to suggest a clinical correlation with the observed kinematic differences between CR and PS TKA designs.^40,51-58 Multiple studies have demonstrated equivalent range of motion^38,39,59 and subjective outcome measures (Table 1).⁶⁰ A randomized prospective trial that compared kinematics and functional scores between the 2 designs failed to observe significant differences in function despite differences in kinematics.⁴⁶ Equivalence in clinical outcome was further supported by a Cochrane Review meta-analysis that evaluated 1810 patients in 17 selected studies.⁶¹ The Knee Society scores have all been in the 92% to 95% ratings with survivals between 90% and 95%.

However, only 80% to 90% of patients are fully satisfied with their implants. The reasons for the dissatisfaction include unexplained anterior knee pain, stiffness, unexplained swelling, loss of range of motion, changes in proprioception, and loss of preoperative functions.¹⁴

The mid-term results of the BCR knees that were performed in the 1980s showed similar results to the CR and PS knees. Townley⁸ reported excellent clinical results with only 2% loosening at 2 to 11 years after surgery. Cloutier and colleagues9 reported 95% survival with improved proprioception at 9 to 11 years after surgery(Table 2).^62,63

Studies comparing traditional TKA designs with cruciate preserving designs, both UKA and BCR, have found differences in subjective outcomes.^62,64 Comparison of UKA and TKA in the same patient demonstrated significant preference for UKA, particularly with stair-climbing.⁶⁵ Similarly, comparison between BCR and PS TKA or CR TKA demonstrated preference for BCR in 85% of patients.⁶²

The new BCR knee designs have just started to come to the market.⁵⁰ The surgical techniques are much improved over the 1980s and cruciate preservation is certainly much easier now. The new designs can produce full range of motion with kinematics that are almost identical to the normal knee in the cadaver laboratory and in computer analyses. These designs certainly should have a similar 20-year survival to the original BCR knees. However, the critical evaluation will be the patient satisfaction scores. With greater motion, better kinematics, and more precise balancing the scores would improve with these designs.

Conclusion

The cruciate ligaments of the knee are central to control of the motion of the normal knee. TKA is a successful operation with at least a 40- to 50-year history. The techniques have continued to develop but 15% to 20% of patients are dissatisfied with the results.¹⁴ Evaluations of the prostheses are more sophisticated and kinematics appears to have a central position in the evaluation. If the knee is to move more anatomically correctly, all of the ligaments must be preserved. Proprioception certainly plays a role in the patient’s judgment of the result. History has shown that a BCR knee can be implanted with good mid-term results and it should certainly be possible to build on these results and design a knee that will incorporate all of the ligaments with full range of motion and increased levels of activity.

Hinge knee arthroplasty was introduced in the 1950s.¹ All 4 major ligaments were replaced by the hinge, which provided stabilization while allowing sagittal plane motion. Its goal was stability, not replication of normal kinematics. The addition of methyl methacrylate cement improved fixation and allowed surface design modifications that addressed normal articular motion. Implants such as the Gunston Polycentric,² the Duocondylar,³ and the Geometric⁴ resurfaced the medial and lateral compartments of the knee while preserving the cruciate ligaments. The implants were subject to greater translational forces without the hinge and loosening became a major problem despite the advances in cementing. It became evident in the 1970s that preservation of the cruciates complicated the procedure. Cruciate resection simplified the operation and allowed improved fixation. The ICLH prosthesis resected the cruciates and used the articular surface design to give stability to the knee.^5,6 The total condylar prosthesis had a “tibial” imminence that mimicked the shape of the tibial surface but also sacrificed both of the cruciate ligaments (Figure 1).

Designers recognized that the cruciate ligaments affected knee kinematics; however, they elected to sacrifice the anterior cruciate ligament (ACL) for surgical simplicity and implant longevity.⁶ In the early 1980s, both the cruciate-retaining (CR) total knee arthroplasty (TKA) (Figure 2) and posterior-stabilized (PS) TKA (Figure 3) designs addressed the posterior cruciate ligament (PCL) function. The PCL was preserved in the “cruciate-retaining” TKA, substituted in the “posterior-stabilized” TKA using a cam-post mechanism. The CR TKA designers believed that PCL preservation produced a more balanced knee with a more anatomical result, a more normal joint line, and better function, especially on stair climbing. The PS TKA designers admitted the value of posterior stabilization but argued that it was too difficult to consistently save the PCL in all cases, and that the PS knee was easier for surgeons to implant with more reliable roll back.⁷

The Geometric knee was developed in the 1970s to retain both cruciate ligaments.⁴ Unfortunately, it created a kinematic conflict by using a constrained articular surface design that prevented the motion required by the cruciate ligaments. This conflict resulted in tibial loosening and early failures. The compromised results decreased interest in the bicruciate-retaining (BCR) TKA designs, allowing the CR TKA and PS TKA designs to flourish for the next 20 years with little or no attempts to retain the ACL.

In the 1980s the BCR TKA design was pursued by Townley⁸ and Cartier.⁹ Townley⁸ believed that cruciate resection was a concession to “improper joint synchronization”⁸ and Cartier⁹ thought that cruciate preservation permitted more normal proprioception.⁹ Unlike prior BCR TKA designs, the mid-term clinical results were equal to or better than the standard CR TKA or PS TKA of the time, and 9- to 11-year follow-up demonstrated comparable outcomes.⁸ While these results highlighted the possibility of a BCR TKA, the surgical technique and failures of the Geometric knee discouraged surgeons from pursuing the BCR TKA.

Interest in cruciate-preserving knee arthroplasty returned with partial knee replacements, with patients reporting more normal proprioception and motion.¹⁰ The techniques became more popular with the introduction of the minimally invasive surgeries in the early 2000s and cruciate ligament preservation became a more interesting concept.^11,12 Some surgeons preserved the cruciates by using separate implants for the medial, lateral, and patellofemoral surfaces.¹⁰ These results were acceptable for the time but required considerable surgical talent and did not report 20-year results similar to the CR and PS knees.

Most prosthetic designs attempt to copy the normal knee anatomy. Using fluoroscopic studies and computer analysis, designers began to investigate the motion (or kinematics) of the normal knee and realized that despite the fact the TKA looked like the human knee, the designs were not kinematically correct.¹³

Although TKA successfully treats pain secondary to degenerative joint disease, many patients are unable to return to their prior level of function, with up to 20% reporting dissatisfaction with their level of activity.¹⁴ The observed differences in kinematics between a normal knee and a TKA may explain part of this discrepancy.

Normal Knee Motion

The tibiofemoral articulation in a normal knee follows a reproducible pattern of motion as the knee moves from extension to flexion. The lateral femoral condyle (LFC) translates posteriorly with a combination of rolling and sliding motion, while the medial femoral condyle (MFC) has minimal posterior translation and thus acts as a pivot for knee motion. The MFC is larger, less curved, and has a biphasic shape with 2 distinct radiuses of curvature that correspond to an “extension” and “flexion” facet. The transition between the MFC facets occurs at approximately 30° of flexion, whereby the contact point transfers posteriorly with little condylar translation.^15-17 In contrast, the LFC is smaller, has a single radius of curvature, and gradually translates posteriorly throughout flexion. Static magnetic resonance imaging of the knee from 0° to 120° shows an average of 19 mm posterior translation for the LFC and 2 mm for the MFC.^15-20

In deep flexion, beyond 130°, posterior translation continues for both condyles. The LFC experiences enough excursion to cause loss of joint congruity and partial posterior subluxation.^19,20 The MFC shows little additional posterior translation, yet it too loses joint congruity through condylar lift-off. Contact between the posterior horn of the medial meniscus and the posterior femoral condyle limits further flexion.^16,21

The difference in motion between the condyles leads to internal tibial rotation during flexion. The initial 10° of knee flexion produces 5° of internal rotation, and an additional 15° of internal tibial rotation occurs throughout the remainder of knee flexion.

Fluoroscopic imaging with computed tomography (CT)- or magnetic resonance (MR)-based modeling has shown the dynamic in vivo relationship of the tibiofemoral joint. Studies have confirmed significantly greater LFC posterior translation as compared to the MFC;²² however, in vivo studies have also shown notable variability in articular rotation and translation based on activity. This highlights the role of ligamentous tension and muscle contraction in kinematics.^21-23

The ACL in TKA

The majority of current TKA designs sacrifice the ACL without substituting for its function. The loss of the ACL has significant effects upon the kinematics of the knee.

The ACL is composed of 2 bundles, the anteromedial and posterolateral bundles, which originate on the LFC and insert broadly onto the tibial intercondylar eminence. Its primary role is to resist anterior tibial translation, particularly from 0° to 30° of flexion, which corresponds to the peak quadriceps force that pulls the tibia anteriorly.²⁴ ACL deficiency causes anterior tibial translation during early flexion and abnormal internal tibial rotation.^25-27 ACL deficient knees demonstrate a posterior femoral position in full extension, and increased MFC translation during knee flexion.^28-32

The role of the ACL in knee arthroplasty has been evaluated by comparing unicompartmental knee arthroplasty (UKA) with TKA, as a reflection of ACL preserving vs sacrificing procedures.^33-35 Sagittal plane translation is similar between UKA and normal knees,^33,34 while the CR TKA and PS TKA designs show anterior tibia subluxation in full extension.^33-35 The difference between UKA and TKA is greatest in extension, corresponding to the ACL functional range. These findings highlight kinematic similarities between TKA designs and the ACL deficient knee.

The majority of UKAs demonstrate near-normal kinematics. A small percentage of the study group demonstrated aberrant anterior tibial motion, highlighting a concern over ACL attenuation with time. Additionally, studies that evaluate the ACL in osteoarthritic knees have questioned the baseline integrity of the ACL.36 Yet the long-term outcomes in UKA design have shown preservation of kinematics due to intact cruciates.³⁷

The PCL in TKA

Because the majority of TKA designs sacrifice the ACL, the classic debate has focused on the utility of the native PCL. Both the CR and PS TKA are designed to offer posterior stabilization; however, kinematic studies have demonstrated notable differences.^38,39

The CR TKA design relies on the PCL to resist posterior sag and to prevent the hamstring musculature from pulling the tibia posteriorly during flexion. Studies have shown paradoxical anterior translation of both femoral condyles during flexion, particularly on the medial side of the knee.⁴⁰ There is also increased variability in femoral rollback. It is unclear whether the PCL can function normally in the absence of the ACL, which causes the PCL to adapt a less anatomic vertical position. The PCL may also be unable to function significantly without the ACL because of pre-existing degenerative histological changes.⁴¹

The PS TKA utilizes a cam-post mechanism for posterior stabilization. In contrast to normal knee kinematics, this mechanism creates equal MFC and LFC posterior translation, 8 mm on average at 90° flexion.⁴⁰ The equivalent translation in PS designs contributes to decreased internal tibial rotation and an increased polyethylene wear at the post.

Role of Surface Geometry

The articular geometry of the knee plays an important role in normal knee kinematics. Initial TKA designs used a femoral component with a single radius of curvature for both femoral condyles.⁴²Current TKA designs that match the femoral component to the native femoral anatomy, by differing the medial and lateral condyle geometry, have demonstrated kinematics that better resemble a native knee.⁴³ Additional changes to the radius of curvature along the posterior facet of the femoral condyles may reduce impingement during deep flexion. These “high flex” designs have demonstrated equivalent range of motion in some studies⁴⁴ and improved weight-bearing motion in others.⁴⁵ Surface geometry is important but is not the entire answer to kinematics.

Advances in TKA Design

Knee motion is guided by multiple factors, including the tibiofemoral articular geometry, the surrounding soft tissue tension, and muscle tone. Bicruciate-substituting (BCS) TKA and BCR TKA are forms of evolution from the CR and PS TKA and attempt to respect the function of both cruciate ligaments and provide better kinematics.

The BCS TKA utilizes a modified cam-post articulation to provide both anterior and posterior stabilization (Figure 4).⁴⁶ The surgical approach remains the same and the implant geometry affects the motion. The BCS TKA design demonstrates femoral rollback at 90° with an average of 14 mm for the MFC and 23 mm for the LFC, and 10° internal tibial rotation.^46,47 Additionally, it provides increased sagittal stability during early flexion and an improved pivot shift (indicating improved anterior stabilization).

The BCR designs preserve both cruciates and provide anterior and posterior stabilization. Fluoroscopic imaging has demonstrated contact points in full extension, and posterior rollback at 90° flexion that more closely replicates the normal knee.⁴⁸

Design and Surgical Techniques for Bicruciate Knee Replacements

If all of the ligaments are preserved, the TKA surfaces must allow motion to be driven by the ligaments in combination with the surfaces alone. The femur can be designed anatomically with asymmetric condyles. The femoral box must allow for preservation of the tibial bone island without impinging upon the cruciate ligaments. The tibial surface must be minimally constrained with concavity medially and convexity laterally.

The bone island preservation does not permit a single-piece tibial polyethylene insert. Therefore, the inserts will replicate the UKA designs (Figure 5). The knee should allow greater range of motion with the possibility of heel to buttocks contact. This increased motion will lead to greater roll back of the femur on the tibia and can lead to subluxation of the femoral runner off of the tibial surface on the lateral side, mimicking the normal knee. This subluxation is desirable but may lead to increased wear of the polyethylene on the lateral side of the knee.

The instruments should be specific for the design but must also be user-friendly. The 2 major issues with the surgery are balancing the knee in full extension and flexion, and preservation of the tibial bone island. The preexisting knee deformity should be <10° in all planes to limit the amount of collateral ligament releases. The collaterals must be balanced in a similar fashion to the standard TKA. Flexion contracture can be treated with posterior capsular release around the cruciates or with an increased distal femoral resection (2 mm at the maximum).

It is important to size the femur correctly because it will be difficult to adjust the flexion gap on the tibial side. A 9-mm posterior medial femoral condyle resection is a reasonable guide if the condyle is not atrophic. However, the exact resection thickness will be implant-specific and should be correlated with the dimensions of the prosthesis being implanted. The tibial bone island must be properly rotated with respect to the center line (Akagi’s line)⁴⁹ and must not be undercut. The tibial instrument should include pins or blocks to prevent the sawblades from undercutting the island (Figure 6), as undermining leads to fracture in full extension. If undermining occurs, it may be possible to place a cancellous screw through the island and still preserve the ligaments. The integrity of the island is best tested by bringing the knee to full extension and checking for liftoff of the bone. If there is significant compromise of the island, the bone should be resected and either a CR or PS TKA can be implanted. Della Valle and colleagues⁵⁰ reported a 9.2% incidence (11 of 119 cases) of bone island fracture in their early experience with a BCR TKA and improved this to 1.9% (5/258 cases) after reassessing their technique.

The gap tension should be evaluated either with traditional spacer blocks or with tensioning devices on the medial and lateral side of the knee after the tibial resections are completed. The polyethylene inserts are anatomically different. It may be possible to vary the thickness from medial to lateral, but not in excess of 2 mm.

As the BCR surgical techniques evolve, the balancing and tibial resection may be refined through specialized instrumentation. Such “smart instruments” that incorporate gyros may expedite tibial alignment, and sensor devices may assist with gap balancing. Haptic surgical robotic guides may assist in the tibial resection, facilitating bone island preservation by avoiding any possibility of undermining. At present these assistive aides are not necessary for the operation but may play a future role.

Clinical Results of Knee Arthroplasties

The results of knee replacements improved steadily from the 1970s through the 1990s. The scoring systems were somewhat limited and there was little data on the perception of the patients. The prosthetic designs stabilized at the end of the 1990s with only minor modifications since the year 2000. The 20-year results show similar findings for both the CR and the PS designs. There is little evidence to suggest a clinical correlation with the observed kinematic differences between CR and PS TKA designs.^40,51-58 Multiple studies have demonstrated equivalent range of motion^38,39,59 and subjective outcome measures (Table 1).⁶⁰ A randomized prospective trial that compared kinematics and functional scores between the 2 designs failed to observe significant differences in function despite differences in kinematics.⁴⁶ Equivalence in clinical outcome was further supported by a Cochrane Review meta-analysis that evaluated 1810 patients in 17 selected studies.⁶¹ The Knee Society scores have all been in the 92% to 95% ratings with survivals between 90% and 95%.

However, only 80% to 90% of patients are fully satisfied with their implants. The reasons for the dissatisfaction include unexplained anterior knee pain, stiffness, unexplained swelling, loss of range of motion, changes in proprioception, and loss of preoperative functions.¹⁴

The mid-term results of the BCR knees that were performed in the 1980s showed similar results to the CR and PS knees. Townley⁸ reported excellent clinical results with only 2% loosening at 2 to 11 years after surgery. Cloutier and colleagues9 reported 95% survival with improved proprioception at 9 to 11 years after surgery(Table 2).^62,63

Studies comparing traditional TKA designs with cruciate preserving designs, both UKA and BCR, have found differences in subjective outcomes.^62,64 Comparison of UKA and TKA in the same patient demonstrated significant preference for UKA, particularly with stair-climbing.⁶⁵ Similarly, comparison between BCR and PS TKA or CR TKA demonstrated preference for BCR in 85% of patients.⁶²

The new BCR knee designs have just started to come to the market.⁵⁰ The surgical techniques are much improved over the 1980s and cruciate preservation is certainly much easier now. The new designs can produce full range of motion with kinematics that are almost identical to the normal knee in the cadaver laboratory and in computer analyses. These designs certainly should have a similar 20-year survival to the original BCR knees. However, the critical evaluation will be the patient satisfaction scores. With greater motion, better kinematics, and more precise balancing the scores would improve with these designs.

Conclusion

The cruciate ligaments of the knee are central to control of the motion of the normal knee. TKA is a successful operation with at least a 40- to 50-year history. The techniques have continued to develop but 15% to 20% of patients are dissatisfied with the results.¹⁴ Evaluations of the prostheses are more sophisticated and kinematics appears to have a central position in the evaluation. If the knee is to move more anatomically correctly, all of the ligaments must be preserved. Proprioception certainly plays a role in the patient’s judgment of the result. History has shown that a BCR knee can be implanted with good mid-term results and it should certainly be possible to build on these results and design a knee that will incorporate all of the ligaments with full range of motion and increased levels of activity.