One year after navigated total knee replacement, no clinically relevant difference found between fixed bearing and mobile bearing knee replacement in a double-blind randomized controlled trial.

Background: The mobile bearing designs have not yet been shown to improve clinical outcome of total knee arthroplasty (TKA). In this prospective randomized study, we compared the short-term clinical results of a mobile bearing implant with those of the fixed bearing version of the same implant.

Methods: We randomized 100 knees into two double-blind groups who received either the fixed (FB, 52 knees) or the mobile bearing (MB, 48 knees) version of the same implant. We used navigation to standardize the surgical technique. For up to one year, we recorded the Knee Society (KSS) and Oxford (OXF) scores. We performed an exploratory analysis of variance (ANOVA) to determine the influence of baseline scores as covariate and the extent of improvement in clinical outcome over time.

Results: After one year, we did not detect any statistically significant difference between the two groups. The KSS scores differed by 2 points, the OXF scores by 1.1 points.

Conclusion: Even with identical geometry of implant surfaces and a navigated surgical technique, first-year results do not support a preference for either a fixed or a mobile design.