Fixed versus mobile bearing medial unicompartmental knee arthroplasty with the same femoral implant design: a randomised controlled trial with a minimum of 10-year follow-up.

BACKGROUND

The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) has yet to be determined. In this randomised controlled trial from a single institution, we aimed to compare the clinical outcome, complications and joint survival of a single design femoral component medial UKA with either a fixed or mobile bearing tibial component from the same (Corin AMC, later rebranded Uniglide) implant system.

METHODS

This was a prospective randomised trial with patients randomised to either fixed or mobile tibial components with the Uniglide system between 2006 and 2014. The primary outcome was patient reported outcome measure (PROM) using the Oxford Knee Score (OKS). Secondary outcomes were the American Knee Society Score (AKSS), the Western Ontario and McMaster University (WOMAC) arthritis index and the assessment of complications/reoperation.

RESULTS

There were 163 primary UKAs. With a minimum 10-year follow-up there were 101 patients with PROM scores available (53 fixed vs 48 mobile); there was no statistically significant difference between the two groups (OKS 36.9 [11.2], n = 53 vs 36.8 [9], n = 48; p = 0.990). However, regarding the early revision by 10 years, there was a statistically significant lower chance in the fixed bearing group (risk ratio was found to be 0.42 [95 %CI 0.184 to 0.937; p = 0.030]).

CONCLUSIONS

This study shows comparable good clinical outcomes between fixed and mobile bearing UKA with a minimum of 10-year follow-up. However, higher revision rates were demonstrated in the mobile bearing group over the course of 10 years post-operatively.