Age Influences Mid-term Survivorship in Unicompartmental Knee Arthroplasty: A 20-Year Single-Surgeon Cohort Analysis of 599 Patients

Introduction Unicompartmental knee arthroplasty (UKA) is a well-established surgical option for isolated compartment osteoarthritis. Medial UKA is more common due to the higher prevalence of medial compartment disease. However, lateral UKA has shown promising results, although it is less frequently performed. This study evaluates mid-term outcomes in a large, single-surgeon cohort, comparing survivorship and revision rates across age, sex, and laterality. Methods Data were retrospectively collected from 599 patients undergoing primary UKA between 2004 and 2024 from the National Joint Registry (NJR). Patients were stratified by age, sex, and compartment (medial vs. lateral). Kaplan-Meier survival curves and Cox proportional hazards models were used to analyze predictors of revision. Revision, viability, and patient death were endpoints. Modern fixed-bearing prostheses were used in all cases. Results Among the 599 patients, 572 underwent medial UKA and 27 underwent lateral UKA. Mean follow-up was 5.6 years. The overall revision rate was 2.8%, all of which occurred in the medial group. No revisions were observed in lateral UKAs. Patients over 70 years experienced no revisions. Younger age was significantly associated with increased revision risk (hazard ratio (HR)=0.95, p=0.039). Conclusion With over 20 years of data, results demonstrate excellent survivorship, especially in patients over 70 years of age and in lateral UKAs, which showed no revisions. Age was a significant predictor of revision, whereas gender and surgical side were not. The study supports lateral UKA as a viable option when appropriately selected.