Abstract
PURPOSE: Evaluate the impact of patient age, body mass index (BMI), medial/central patellofemoral arthritis, and anterior cruciate ligament (ACL) deficiency on five-year patient-reported outcome measures (PROMs) of fixed-bearing medial unicompartmental knee arthroplasty (UKA). METHODS: A consecutive group of 229 patients (240 knees) received fixed-bearing medial UKA. At minimum two (n = 231 knees) and five years (n = 221 knees), patients completed the Oxford Knee Score (OKS), the EuoQol-5D (EQ-5D), Knee injury and Osteoarthritis Outcome Score Physical Function Short Form (KOOS-PS), University of California, Los Angeles (UCLA) activity score, Forgotten Joint Score (FJS), and their level of satisfaction. Sub-group analyses compared PROMs in patients based on: (i) Grade III/IV vs. Grade 0-III medial/central patellofemoral arthritis, (ii) ACL deficiency vs. intact ACL, (iii) age groups (< 50, 50-59, 60-69, 70-79, > 80), and (iv) BMI categories (< 30, 30-35, 35-40, ≥ 40). RESULTS: Satisfaction rates remained consistent at the 2- and 5-year follow-up points, with 96% being satisfied or very satisfied. The OKS, EQ-5D, KOOS PS, or FJS-12 were not statistically significantly different between 2 and 5 years. Five-year UCLA activity scores differed significantly across age groups (50-59 vs 80 + (MD = 1.5; p = 0.027), 60-69 vs 70-79 (MD = 0.9; p = 0.014), and 60-69 vs 80 + (MD = 1.7; p = 0.004)), and between patients with a BMI < 30 vs ≥ 40 (MD = 2.3; p = 0.045). These findings were supported by multivariable regression, which showed that increasing age and higher BMI were independently associated with worse UCLA activity scores. Grade III/IV patellofemoral arthritis was associated with worse EQ-5D scores but was not associated with worse OKS, UCLA, KOOS-PS, or FJS-12. ACL deficiency was associated with higher KOOS-PS scores. CONCLUSION: Five-year outcomes following fixed-bearing medial UKA demonstrated high patient satisfaction, unchanged from two years. Although older age was associated with lower activity and higher BMI (> 40) with worse function, the effect sizes were small and not clinically meaningful. Patellofemoral arthritis and ACL deficiency had no negative functional impact. Therefore, age, BMI, patellofemoral arthritis, and ACL status should not be considered contraindications; instead, broad selection criteria for fixed-bearing UKA are supported.