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30-Year Survival of the Oxford Mobile Bearing Unicompartmental Knee Arthroplasty
2017 ISAKOS ABSTRACTS
underwent primary TKA through the KA or MA technique were included. Results: Six studies were included in the meta-analysis. The proportion of patients who developed postoperative complications (OR 1.10, 95% CI: 0.49 to 2.46; P¼0.69) did not differ significantly between the KA and MA techniques. The two groups were also similar in terms of change in hemoglobin (95% CI: -0.38 to 0.34; P¼0.91), length of hospital stay (95% CI: -0.04 to 0.55; P¼0.10), hip-knee-ankle angle (95% CI: -1.76 to 0.75; P¼0.43), joint line orientation angle (95% CI: -4.27 to 4.23; P¼0.99), tibial component slope (95% CI: -0.53 to 3.56; P¼0.15), and femoral component flexion (95% CI: -2.61 to 7.57; P¼0.34). In contrast, operation time (95% CI: -27.16 to -3.71; P¼0.01), overall functional outcome (95% CI: 6.59 to 11.51; P<0.0001), knee anatomical axis (95% CI: -1.38 to -0.01; P¼0.05), femoral component relative to the mechanical axis (95% CI: -2.47 to -1.40; P<0.0001), and tibial component relative to the mechanical axis (95% CI: 1.56 to 2.95; P<0.0001) were significantly different between the two groups. Conclusion: There were no significant differences in postoperative complications, change in hemoglobin, length of hospital stay, hip-knee-ankle angle, joint line orientation angle, tibial component slope, or femoral component flexion between the KA and MA techniques for primary TKA. However, the KA technique resulted in a significantly shorter operation time and better overall functional outcome than the MA technique, even though the femoral component was placed slightly more valgus and the tibial component slightly more varus relative to the mechanical axis with the KA technique. Category: Knee - Arthroplasty Paper #166: No Difference in 2-Year Functional Outcomes Using Kinematic Versus Mechanical Alignment in TKA: A Randomized Controlled Clinical Trial SIMON W. YOUNG, MD, FRACS, NEW ZEALAND MATTHEW WALKER, MBCHB, FRACS, NEW ZEALAND ALI BAYAN, MBCHB, FRACS, NEW ZEALAND TOBY BRIANT-EVANS, BMED SCI (HONS), BM BS, FRCS (TR & ORTH), UNITED KINGDOM PAUL PAVLOU, FRCS, NEW ZEALAND BILL FARRINGTON, FRCS, NEW ZEALAND North Shore Hospital, Auckland, NEW ZEALAND SUMMARY In this randomized controlled trial, no difference in 2 year functional outcome was seen between kinematic versus mechanical alignment in TKA. ABSTRACT DATA Background: Neutral mechanical alignment (MA) in total knee arthroplasty (TKA) aims to position femoral and tibial components perpendicular to the mechanical axis of the limb. In contrast, kinematic alignment (KA) attempts to match implant position to the prearthritic anatomy of
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the individual patient with the aim of improving functional outcome. However, comparative data between the two techniques are lacking. Questions/purposes: In this randomized trial, we asked (1) Are 2-year patient-reported outcome scores enhanced in patients with KA compared with an MA technique? (2) How does postoperative component alignment differ between the techniques? (3) Is the proportion of patients undergoing reoperation at 2 years different between the techniques? Methods: Ninety-nine primary TKAs in 95 patients were randomized to either MA (n ¼ 50) or KA (n ¼ 49) groups. A pilot study of 20 TKAs was performed before this trial using the same patient-specific guides positioning in kinematic alignment. In the KA group, patient-specific cutting blocks were manufactured using individual preoperative MRI data. In the MA group, computer navigation was used to ensure neutral mechanical alignment accuracy. Postoperative alignment was assessed with CT scan, and functional scores (including the Oxford Knee Score, WOMAC, and the Forgotten Joint Score) were assessed preoperatively and at 6 weeks, 6 months, and 1 and 2 years postoperatively. No patients were lost to followup. We set sample size at a minimum of 45 patients per treatment arm, based on a 5-point improvement in the mean OKS (the previously reported minimum clinically significant difference for the OKS in TKA), a pooled SD of 8.3, 80% power, and a two-sided significance level of 5%. Results: We observed no difference in 2-year change scores (postoperative minus preoperative score) in KA versus MA patients for the Oxford Knee Score (mean 21.4 SD 7.9 vs 20.4 SD 8.3, least square means 1.0 95% confidence interval [CI] -1.4 - 3.4, p ¼ 0.4), WOMAC score (mean 38 SD17.8 vs 35 SD 8.3, least square means 2.8 95% CI -3.2 e 8.9 p ¼ 0.3), or Forgotten Joint score (28.4 SD 37 vs 27.6 SD 28, least square means 0.8 95%CI -9.1-10.7 p ¼ 0.8). Postoperative hip-knee-ankle axis was not different between groups (mean KA 0.4 varus SD 3.5 versus MA 0.7 varus SD 2.0), but in the KA group, the tibial component was a mean 1.9 more varus than the MA group (95% CI, 0.8 -3.0 , p ¼ 0.003) and the femoral component in 1.6 more valgus (95% CI, -2.5 to -0.7 , p ¼ 0.003). Complication rates were not different between groups. Conclusions: We found no difference in 2-year patientreported outcome scores in TKAs implanted using the KA versus an MA technique. The theoretical advantages of improved pain and function that form the basis of the design rationale of KA were not observed in this study. Currently, it is unknown if the alterations in component alignment seen with KA will compromise long-term survivorship of TKA. Category: Knee - Arthroplasty Paper #167: 30-Year Survival of the Oxford Mobile Bearing Unicompartmental Knee Arthroplasty ANDREW JAMES PRICE, DPHIL, FRCS(ORTH), UNITED KINGDOM ULF SVARD, SWEDEN Nuffield Orthopaedic Centre, Oxford, UNITED KINGDOM
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2017 ISAKOS ABSTRACTS
SUMMARY The medial Oxford mobile bearing UKA in this series has excellent 30-year survival results with approximately 80% of patients undergoing a single procedure to successfully treat their knee OA. ABSTRACT DATA Unicompartmental knee arthroplasty (UKA) has been described as a pre-total knee replacement, implying that revision within the lifetime of a patient is inevitable. However there are few studies of UKA beyond 25-years after implantation. This study presents the 30-year survival of the Phase 1 Oxford mobile bearing UKA used in the medial compartment. From a single centre in Sweden the entire series of 125 medial Phase-1 Oxford UKAs (104 patients) performed from 1983-1988 were reviewed at a minimum of 28years since implantation, for those still alive. The patients had previously been reviewed at 1, 6, 10 and 20 years. The outcome of each UKA was determined, establishing the cause of revision in all patients including those who had died. Failure was defined by revision of any component or patient reported poor clinical outcome at last follow-up for any patient (dead or alive). There was no loss to follow-up. In the entire series at 28-years 89.6% remained unrevised [13 revisions; component loosening(4), dislocation(3), bearing fracture(2), unexplained pain(2), infection(1) and lateral arthrosis(1)]. Of those still alive 4 reported a poor outcome. Four patients reported a poor outcome at final follow-up. The success rate at 28 years was 86.4% and the predicted 30-year survival was 82%. The medial Oxford mobile bearing UKA in this series has excellent 30-year survival results with approximately 80% of patients undergoing a single procedure to successfully treat their knee OA. This procedure offers definitive treatment and should not be considered a pretotal knee replacement. Category: Knee - Arthroplasty Paper #168: The Effect on Long-Term Survivorship of Surgeon Preference for Posterior Stabilized Or Minimally Stabilized Total Knee Replacement: An Analysis of 63,416 Prostheses CHRISTOPHER JOHN VERTULLO, MBBS, FRACS (ORTH), FAORTHA, AUSTRALIA PETER L. LEWIS, MBBS, FRACS (ORTH), FAORTHA, AUSTRALIA MICHELLE LORIMER, BSC (HONS), AUSTRALIA STEPHEN GRAVES, MBBS, FRACS, DPHIL, AUSTRALIA Knee Research Australia, Gold Coast, QLD, AUSTRALIA SUMMARY Is this registry analysis, there was a 45% higher risk of revision for the patients of surgeons who prefer PS TKR compared to the patients of surgeons who prefer MS TKR.
ABSTRACT DATA Background: Controversy still exists as to the optimum management of the Posterior Cruciate Ligament (PCL) in Total Knee Arthroplasty (TKR). Surgeons can choose to kinematically substitute the PCL with a Posterior Stabilized (PS) TKR, or alternatively utilize a Cruciate Retaining (CR), also known as a Minimally Stabilized (MS) TKR. Proponents of PS TKR propose that the reported lower survivorship in registries when directly compared to MS TKR, is due to confounders such as selection bias because of the preferential usage of PS TKR in more complex or severe cases. In this study, we aimed to eliminate these possible confounders by performing an intention to treat analysis based on surgeon preference to choose either PS or MS TKR, rather than the actual prosthesis received. Methods: Cumulative Percent Revision (CPR), Hazard Ratio (HR) and revision diagnosis data were obtained from a large national joint replacement registry from 1 September 1999 until 31 December 2014 for two cohorts of patients, those treated by high-volume MS preferring surgeons and those treated by high-volume PS preferring surgeons. All patients had a diagnosis of osteoarthritis and received fixed bearing TKA with patella resurfacing. Results: At 13 years, the CPR of the MS preferring surgeons was 5.0% (95% CI 4.0,6.2) compared to 6.0% (95% CI 4.2,8.5) for the PS preferring surgeons. Revision risk for the PS preferring surgeons was significantly higher for all causes (HR ¼ 1.45 (95% CI 1.30, 1.63), p< 0.001), loosening/lysis (HR ¼ 1.93 (1.58, 2.37), p<0.001) and for infection (HR ¼ 1.51 (1.25, 1.82), p<0.001). This finding was irrespective of patient age, was evident with cemented fixation and with both cross-linked and non-cross-linked polyethylene. The higher revision risk was only evident in males. Conclusions: There is a 45% higher risk of revision for the patients of surgeons who prefer PS TKR compared to the patients of surgeons who prefer MS TKR. Level of Evidence: II
Category: Knee - Arthroplasty Paper #169: Sports After Total Knee Replacement: Are Intense Contact Sports Possible? MICHEL BERCOVY, MD, FRANCE clinique ARAGO, Paris, FRANCE SUMMARY Intense physical activity is possible after this TKA and does not compromise the midterm survivorship of the implant. ABSTRACT DATA Background: Total Knee Arthroplasty (TKA) implants show durable long-term benefit in wear and loosening. However patients become demanding for more intense physical and sports activities which could decrease implant durability. The purpose of this study is to evaluate the
underwent primary TKA through the KA or MA technique were included. Results: Six studies were included in the meta-analysis. The proportion of patients who developed postoperative complications (OR 1.10, 95% CI: 0.49 to 2.46; P¼0.69) did not differ significantly between the KA and MA techniques. The two groups were also similar in terms of change in hemoglobin (95% CI: -0.38 to 0.34; P¼0.91), length of hospital stay (95% CI: -0.04 to 0.55; P¼0.10), hip-knee-ankle angle (95% CI: -1.76 to 0.75; P¼0.43), joint line orientation angle (95% CI: -4.27 to 4.23; P¼0.99), tibial component slope (95% CI: -0.53 to 3.56; P¼0.15), and femoral component flexion (95% CI: -2.61 to 7.57; P¼0.34). In contrast, operation time (95% CI: -27.16 to -3.71; P¼0.01), overall functional outcome (95% CI: 6.59 to 11.51; P<0.0001), knee anatomical axis (95% CI: -1.38 to -0.01; P¼0.05), femoral component relative to the mechanical axis (95% CI: -2.47 to -1.40; P<0.0001), and tibial component relative to the mechanical axis (95% CI: 1.56 to 2.95; P<0.0001) were significantly different between the two groups. Conclusion: There were no significant differences in postoperative complications, change in hemoglobin, length of hospital stay, hip-knee-ankle angle, joint line orientation angle, tibial component slope, or femoral component flexion between the KA and MA techniques for primary TKA. However, the KA technique resulted in a significantly shorter operation time and better overall functional outcome than the MA technique, even though the femoral component was placed slightly more valgus and the tibial component slightly more varus relative to the mechanical axis with the KA technique. Category: Knee - Arthroplasty Paper #166: No Difference in 2-Year Functional Outcomes Using Kinematic Versus Mechanical Alignment in TKA: A Randomized Controlled Clinical Trial SIMON W. YOUNG, MD, FRACS, NEW ZEALAND MATTHEW WALKER, MBCHB, FRACS, NEW ZEALAND ALI BAYAN, MBCHB, FRACS, NEW ZEALAND TOBY BRIANT-EVANS, BMED SCI (HONS), BM BS, FRCS (TR & ORTH), UNITED KINGDOM PAUL PAVLOU, FRCS, NEW ZEALAND BILL FARRINGTON, FRCS, NEW ZEALAND North Shore Hospital, Auckland, NEW ZEALAND SUMMARY In this randomized controlled trial, no difference in 2 year functional outcome was seen between kinematic versus mechanical alignment in TKA. ABSTRACT DATA Background: Neutral mechanical alignment (MA) in total knee arthroplasty (TKA) aims to position femoral and tibial components perpendicular to the mechanical axis of the limb. In contrast, kinematic alignment (KA) attempts to match implant position to the prearthritic anatomy of
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the individual patient with the aim of improving functional outcome. However, comparative data between the two techniques are lacking. Questions/purposes: In this randomized trial, we asked (1) Are 2-year patient-reported outcome scores enhanced in patients with KA compared with an MA technique? (2) How does postoperative component alignment differ between the techniques? (3) Is the proportion of patients undergoing reoperation at 2 years different between the techniques? Methods: Ninety-nine primary TKAs in 95 patients were randomized to either MA (n ¼ 50) or KA (n ¼ 49) groups. A pilot study of 20 TKAs was performed before this trial using the same patient-specific guides positioning in kinematic alignment. In the KA group, patient-specific cutting blocks were manufactured using individual preoperative MRI data. In the MA group, computer navigation was used to ensure neutral mechanical alignment accuracy. Postoperative alignment was assessed with CT scan, and functional scores (including the Oxford Knee Score, WOMAC, and the Forgotten Joint Score) were assessed preoperatively and at 6 weeks, 6 months, and 1 and 2 years postoperatively. No patients were lost to followup. We set sample size at a minimum of 45 patients per treatment arm, based on a 5-point improvement in the mean OKS (the previously reported minimum clinically significant difference for the OKS in TKA), a pooled SD of 8.3, 80% power, and a two-sided significance level of 5%. Results: We observed no difference in 2-year change scores (postoperative minus preoperative score) in KA versus MA patients for the Oxford Knee Score (mean 21.4 SD 7.9 vs 20.4 SD 8.3, least square means 1.0 95% confidence interval [CI] -1.4 - 3.4, p ¼ 0.4), WOMAC score (mean 38 SD17.8 vs 35 SD 8.3, least square means 2.8 95% CI -3.2 e 8.9 p ¼ 0.3), or Forgotten Joint score (28.4 SD 37 vs 27.6 SD 28, least square means 0.8 95%CI -9.1-10.7 p ¼ 0.8). Postoperative hip-knee-ankle axis was not different between groups (mean KA 0.4 varus SD 3.5 versus MA 0.7 varus SD 2.0), but in the KA group, the tibial component was a mean 1.9 more varus than the MA group (95% CI, 0.8 -3.0 , p ¼ 0.003) and the femoral component in 1.6 more valgus (95% CI, -2.5 to -0.7 , p ¼ 0.003). Complication rates were not different between groups. Conclusions: We found no difference in 2-year patientreported outcome scores in TKAs implanted using the KA versus an MA technique. The theoretical advantages of improved pain and function that form the basis of the design rationale of KA were not observed in this study. Currently, it is unknown if the alterations in component alignment seen with KA will compromise long-term survivorship of TKA. Category: Knee - Arthroplasty Paper #167: 30-Year Survival of the Oxford Mobile Bearing Unicompartmental Knee Arthroplasty ANDREW JAMES PRICE, DPHIL, FRCS(ORTH), UNITED KINGDOM ULF SVARD, SWEDEN Nuffield Orthopaedic Centre, Oxford, UNITED KINGDOM
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2017 ISAKOS ABSTRACTS
SUMMARY The medial Oxford mobile bearing UKA in this series has excellent 30-year survival results with approximately 80% of patients undergoing a single procedure to successfully treat their knee OA. ABSTRACT DATA Unicompartmental knee arthroplasty (UKA) has been described as a pre-total knee replacement, implying that revision within the lifetime of a patient is inevitable. However there are few studies of UKA beyond 25-years after implantation. This study presents the 30-year survival of the Phase 1 Oxford mobile bearing UKA used in the medial compartment. From a single centre in Sweden the entire series of 125 medial Phase-1 Oxford UKAs (104 patients) performed from 1983-1988 were reviewed at a minimum of 28years since implantation, for those still alive. The patients had previously been reviewed at 1, 6, 10 and 20 years. The outcome of each UKA was determined, establishing the cause of revision in all patients including those who had died. Failure was defined by revision of any component or patient reported poor clinical outcome at last follow-up for any patient (dead or alive). There was no loss to follow-up. In the entire series at 28-years 89.6% remained unrevised [13 revisions; component loosening(4), dislocation(3), bearing fracture(2), unexplained pain(2), infection(1) and lateral arthrosis(1)]. Of those still alive 4 reported a poor outcome. Four patients reported a poor outcome at final follow-up. The success rate at 28 years was 86.4% and the predicted 30-year survival was 82%. The medial Oxford mobile bearing UKA in this series has excellent 30-year survival results with approximately 80% of patients undergoing a single procedure to successfully treat their knee OA. This procedure offers definitive treatment and should not be considered a pretotal knee replacement. Category: Knee - Arthroplasty Paper #168: The Effect on Long-Term Survivorship of Surgeon Preference for Posterior Stabilized Or Minimally Stabilized Total Knee Replacement: An Analysis of 63,416 Prostheses CHRISTOPHER JOHN VERTULLO, MBBS, FRACS (ORTH), FAORTHA, AUSTRALIA PETER L. LEWIS, MBBS, FRACS (ORTH), FAORTHA, AUSTRALIA MICHELLE LORIMER, BSC (HONS), AUSTRALIA STEPHEN GRAVES, MBBS, FRACS, DPHIL, AUSTRALIA Knee Research Australia, Gold Coast, QLD, AUSTRALIA SUMMARY Is this registry analysis, there was a 45% higher risk of revision for the patients of surgeons who prefer PS TKR compared to the patients of surgeons who prefer MS TKR.
ABSTRACT DATA Background: Controversy still exists as to the optimum management of the Posterior Cruciate Ligament (PCL) in Total Knee Arthroplasty (TKR). Surgeons can choose to kinematically substitute the PCL with a Posterior Stabilized (PS) TKR, or alternatively utilize a Cruciate Retaining (CR), also known as a Minimally Stabilized (MS) TKR. Proponents of PS TKR propose that the reported lower survivorship in registries when directly compared to MS TKR, is due to confounders such as selection bias because of the preferential usage of PS TKR in more complex or severe cases. In this study, we aimed to eliminate these possible confounders by performing an intention to treat analysis based on surgeon preference to choose either PS or MS TKR, rather than the actual prosthesis received. Methods: Cumulative Percent Revision (CPR), Hazard Ratio (HR) and revision diagnosis data were obtained from a large national joint replacement registry from 1 September 1999 until 31 December 2014 for two cohorts of patients, those treated by high-volume MS preferring surgeons and those treated by high-volume PS preferring surgeons. All patients had a diagnosis of osteoarthritis and received fixed bearing TKA with patella resurfacing. Results: At 13 years, the CPR of the MS preferring surgeons was 5.0% (95% CI 4.0,6.2) compared to 6.0% (95% CI 4.2,8.5) for the PS preferring surgeons. Revision risk for the PS preferring surgeons was significantly higher for all causes (HR ¼ 1.45 (95% CI 1.30, 1.63), p< 0.001), loosening/lysis (HR ¼ 1.93 (1.58, 2.37), p<0.001) and for infection (HR ¼ 1.51 (1.25, 1.82), p<0.001). This finding was irrespective of patient age, was evident with cemented fixation and with both cross-linked and non-cross-linked polyethylene. The higher revision risk was only evident in males. Conclusions: There is a 45% higher risk of revision for the patients of surgeons who prefer PS TKR compared to the patients of surgeons who prefer MS TKR. Level of Evidence: II
Category: Knee - Arthroplasty Paper #169: Sports After Total Knee Replacement: Are Intense Contact Sports Possible? MICHEL BERCOVY, MD, FRANCE clinique ARAGO, Paris, FRANCE SUMMARY Intense physical activity is possible after this TKA and does not compromise the midterm survivorship of the implant. ABSTRACT DATA Background: Total Knee Arthroplasty (TKA) implants show durable long-term benefit in wear and loosening. However patients become demanding for more intense physical and sports activities which could decrease implant durability. The purpose of this study is to evaluate the