Unicompartmental Knee Arthroplasty Achieves Greater Flexion With No Difference in Functional Outcome, Quality of Life, and Satisfaction vs Total Knee Arthroplasty in Patients Younger Than 55 Years. A Propensity Score-Matched Cohort Analysis.

BACKGROUND: Improvements in surgical techniques, implant design, and adherence to indications have resulted in favorable outcomes after unicompartmental knee arthroplasty (UKA), particularly in an older population. However, no studies have compared the performance of contemporary UKA and total knee arthroplasty (TKA) in a young population.

METHODS: Prospectively collected registry data of 160 UKAs performed in 160 patients younger than 55 years were reviewed. Propensity scores generated using logistic regression were used to adjust for confounding variables of age, gender, body mass index, preoperative range of motion, Knee Society Score, Oxford Knee Score, and Short-Form 36, allowing matching of the TKA cohort to the UKA cohort in a 1:1 ratio using the nearest-neighbor method.

RESULTS: The UKA group had significantly greater flexion at 6 months and 2 years (P < .001). There was no significant difference in Knee Society Score, Oxford Knee Score, and Short-Form 36. At 2 years, 89.4% and 88.8% of the TKA and UKA groups were satisfied (P = 1.00) while 86.9% and 86.3% had their expectations fulfilled (P = 1.00). At a mean follow-up of 7 years, there were 2 revisions in each group (2.2%).

CONCLUSION: Although native knee biomechanics are preserved, younger patients do not seem to perceive this oft-cited benefit of UKA, as this did not translate into greater health-related quality of life or patient satisfaction compared to TKA. The theoretical advantages of UKA were not borne out by our findings, other than greater flexion up to 2 years postoperatively.