Comparison of postoperative knee flexion and patient satisfaction between newly and conventionally designed medial pivot total knee arthroplasty: a 5-year follow-up matched cohort study.

ABSTRACT

INTRODUCTION: The medial pivot total knee arthroplasty (TKA) has good patients' satisfaction; however, there is likely the restriction of postoperative knee flexion. The 2nd generation medial pivot TKA prosthesis was designed to improve postoperative knee flexion. This study aimed to compare the clinical outcomes and patient satisfaction between the 2nd generation and 1st generation medial pivot TKA prostheses. MATERIALS AND METHODS: We conducted a retrospective study of 472 consecutive TKAs, performed using either the 2nd generation (EVOLUTION™), having smaller posterior femoral condyle and asymmetrical tibial tray, or 1st generation (ADVANCE™) prosthesis. The use of each system was historically determined. Patient age, sex and body mass index were matched between the two groups, with 157 cases ultimately included in each group. Measured clinical outcomes included knee range of motion, the Knee Society Score, the rate of re-operation, and radiological parameters. Patient satisfaction was evaluated using the 12-item Forgotten Joint Score (FJS-12). RESULTS: The average follow-up period was 5.0 (3.7-6.3) years for the 2nd generation group and 8.7 (6.1-12.8) years for the 1st generation group (p < 0.01). The postoperative knee flexion range was 127° (80°-140°) for the 2nd generation and 118° (90°-135°) for the 1st generation at final follow-up (p < 0.01). On multivariate regression analysis, use of the 2nd generation prosthesis predicted greater postoperative knee flexion. The average FJS-12 score was 64 (0-100) for the 2nd generation and mean 57 (0-100) for the 1st generation (p < 0.01). Other clinical outcomes were similar between the two groups. CONCLUSIONS: Compared to the 1st generation, the 2nd generation medial pivot prosthesis provides greater postoperative knee flexion and patient satisfaction.