Rotierendes oder fixiertes Tibiainlay? Randomisierter klinischer und radiologischer Vergleich rotierender und fixierter Tibiainlays bei computerassistiertem bikondylärem Kniegelenkoberflächenersatz

Background: Mobile bearing tibial platform designs are advocated to improve functional results of total knee arthroplasty (TKA), and to reduce wear in the longer term. This study investigated short-term clinical results with two patient groups who were systematically different in the fixed or mobile tibial bearing only. Methods: 100 knees in 97 patients were stratified according to age and gender and randomized into two groups, fixed-bearing (FB) with 52 knees and rotating platform (RP) with 48 knees. All received the same posterior cruciate retaining implant Columbus® (B. Braun Aesculap, Tuttlingen, Germany) in either fixed or mobile version by two experienced surgeons and followed an identical rehabilitation regime. Physical examinations were performed in a double-blinded manner before the operation and three, six and twelve months thereafter, using the Oxford and Knee Society scoring systems. Analyses were carried out using the Mann-Whitney-U-test at alpha = 0.05 and beta = 0.15 for the primary endpoint, and by ANOVA for exploratory tests concerning covariate influence of baseline scores, and significance of improvement with time. Results: The primary endpoint of the Knee Society Scores (KSS) as well as the secondary endpoints of Oxford knee score and range of motion were not statistically significantly different. Baseline demographics and radiographic alignment pre- and postoperatively were homogeneous between the groups as well. When including baseline scores as covariates into the statistical analysis the variation in scores was again not significantly dependent of the treatment groups. Conclusions: There was no difference of more than eight points KSS score value due to FB or RP design of primary TKA for osteoarthritis in the first postoperative year. The study design controlled for several relevant causes of variation external to the fact of the platform being fixed or mobile. With regard to the first year and in patients matching our inclusion criteria, there is no evidence to prefer either fixed or mobile tibial platform designs.