SURVIVORSHIP AND QUALITY OF OUTCOME AFTER UNI-COMPARTMENTAL AND TOTAL KNEE REPLACEMENT IN COMPARABLE PATIENTS: FIVE-YEAR RESULTS

Abstract

Introduction and Aims: Several non-comparative studies for uni-compartmental knee replacement (UKR) and total knee replacement (TKR) have been published, but few provide a direct comparison in well-matched patients. The aim of this study was to assess five-year survivorship and the quality of outcome following UKR and TKR in pre-operatively matched patient groups.

Method: From a prospective database of over 600 patients undergoing knee replacement for osteoarthritis, 70 primary medial Oxford UKRs (62 patients) were matched pre-operatively with 70 primary Kinematic TKRs (68 patients) for age, sex, body mass index, active range of movement (ROM) and Knee Society Score (KSS). The two groups were assessed at six, 18, 36 and 60 months following knee replacement and compared for survivorship of the prosthesis (with failure defined as revision for any reason or ‘worst-case’ assuming all patients lost to follow-up are revised), quality of outcome based on the KSS (reported as separate knee and function score) and the ROM achieved.

Results: Three (4%) patients in the UKR group and two (3%) in the TKR group were unavailable for follow-up at five years. Five-year survivorship (Kaplan-Meier methodology) was significantly different for the two groups using revision for any reason as an endpoint – 90% for UKR, 100% for TKR (log-rank test, p=0.01). Assuming all patients lost to follow-up were revised, the ‘worst-case’ five-year survivorship was also significantly different for the two groups – 85% for UKR, 97% for TKR (log-rank test, p=0.02). Analysis of the KSS at six, 18, 36 and 60 months showed no significant difference between the two groups for the knee score (p=0.48) and the function score (p=0.1). The ROM achieved at five years was greater for the UKR group and the difference was statistically significant (UKR: Least square mean 105 degrees, standard error 1.2; TKR: Least square mean 98 degrees, standard error 1.2, p< 0.001).

Conclusion: In comparable patients with osteoarthritis of the knee, survivorship remains superior for TKR at five years. The ROM achieved is greater for UKR, but there is no difference in the overall quality of outcome following UKR or TKR. We believe that UKR should only be performed in carefully selected cases because mid-term functional outcome is similar following UKR or TKR and the complication rate may be higher for UKR.