'Wear advantage' of mobile-bearing unicompartmental knee arthroplasty is a myth: Higher volumetric wear without reduced revision rates compared to the fixed-bearing design: A systematic review and meta-analysis.

Abstract

This systematic review and meta-analysis aims to comprehensively compare wear between mobile- and fixed-bearing unicompartmental knee arthroplasty (UKA) using clinical, in vitro and registry data. This study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered with PROSPERO. PubMed, EMBASE and Epistemonikos were searched. Clinical, registry, in vitro and in silico studies reporting wear outcomes in mobile- and fixed-bearing UKA were included. Risk of bias was assessed using the mixed methods appraisal tool (MMAT), and pooled analyses were performed using mixed-effects models. The electronic literature search identified 5688 studies, of which 64 met the inclusion criteria after screening. For UKAs implanted after 2000, there were no statistically significant differences in clinical revision rates for wear between mobile- and fixed-bearing designs, either overall (<1% vs. 1%; <i>p</i> = n.s.) or at a follow-up of >10 years (2% vs. 1%; <i>p</i> = n.s.). A statistically significant difference in in vitro volumetric wear was observed (<i>p</i> < 0.001), with mobile-bearing constructs demonstrating a higher wear rate (5.54 mm³/MC) compared to fixed-bearing constructs (1.69 mm³/MC). This comprehensive review of all available data demonstrates that fixed- and mobile-bearing medial UKAs show no difference in the clinical incidence of revision for wear but reveals a statistically significant advantage for fixed-bearing medial UKAs regarding volumetric wear, consistent with the original hypothesis of our study. Fixed-bearing implants show more uniform wear patterns, suggesting potentially more predictable long-term performance. Level IV.