Influence of Implant Design on Failure Rates in Medial Unicompartmental Knee Arthroplasty: A Meta-Analysis.

Abstract

Medial unicompartmental knee arthroplasty (MUKA) has become an established treatment option for medial compartment osteoarthritis. While advancements in materials and robotic-assisted surgery have improved outcomes, concerns about long-term survivorship persist. This systematic review and meta-analysis assess failure rates of MUKA based on implant design, follow-up periods, and surgical techniques. A systematic review and meta-analysis were conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered on PROSPERO (ID CRD42023479247). Literature searches in PubMed, Cochrane, MEDLINE, and EMBASE included studies from 2016 to 2024. Inclusion criteria were English-language studies reporting MUKA survivorship and failure rates, with a minimum cohort of 20 patients, specifying implant type and surgical technique. Data extraction and analysis were performed by three independent reviewers. Statistical analyses used the Mantel-Haenszel method and random-effects models. From 159 articles, failure rates across 114,088 knees were 2.7% (95% CI [confidence interval] 2.1 to 3.3). Failure rates were 6.3% for fixed bearing all-poly (FB A-P), 1.3% for fixed bearing metal-backed (FB M-B), and 3.0% for mobile bearing metal-backed (MB M-B). Significant differences were noted between FB A-P and both FB M-B (P = 0.004) and MB M-B (P = 0.007), but not between FB M-B and MB M-B (P = 0.12). By follow-up duration, failure rates were 0.4% for < five years, 4.1% for five to 10 years, and 8.3% for > 10 years. Robotic techniques had significantly lower failure rates than standard techniques (1.2 versus 2.91%, P = 0.001). This meta-analysis demonstrates that advanced implant designs improve outcomes for medial UKA, while robotic techniques further enhance results. However, variability in survivorship definition, follow-up duration, and lack of differentiation between cemented and uncemented implants remain limitations. Future studies should explore long-term outcomes, refine implant choices, and optimize surgical approaches to enhance MUKA survivorship.