Technology Assistance and Fixed-Bearing Design Were Associated with Higher Revision-Free Survival at 15 Years After UKA

Background: Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty for isolated compartment osteoarthritis; however, concerns persist regarding its long-term durability. The purpose of this study was to evaluate revision-free survivorship, risk factors for revision, and clinical outcomes in a large consecutive series of contemporary UKAs. Methods: We retrospectively reviewed consecutive primary UKAs performed from 2000 to 2021 at a single tertiary academic center. Revision-free survivorship was estimated using a Kaplan-Meier analysis, and risk factors for revision were assessed using Cox proportional hazards modeling. Clinical outcomes were assessed using the Knee Society Score (KSS). Results: A total of 2,234 UKAs were included. Fixed-bearing implants were used in 78% of UKAs. Technology assistance was used in 59% of UKAs (fluoroscopy, 43%; robotic assistance, 15%; computer navigation, 1%). The mean patient age was 65 years, the mean body mass index was 31 kg/m 2 , and 49% of UKAs were performed in female patients. Patient race was White in 97% of UKAs, and patient ethnicity was not Hispanic or Latino in 94%. Revision-free survivorship was 92% at 10 years and 85% at 15 years. Overall, 118 UKAs were revised, most commonly through conversion to total knee arthroplasty (97%). The most frequent indications for revision were progression of osteoarthritis in an adjacent compartment (41%), aseptic loosening (23%), unexplained pain (9%), and hardware failure (9%). Factors associated with a lower risk of revision in the univariable analysis included technology assistance (hazard ratio [HR], 0.4; p < 0.01) and high surgeon volume (HR, 0.5; p < 0.01). Mobile-bearing design (HR, 1.9; p < 0.01) was associated with an increased risk of revision in the univariable analysis. The mean KSS improved from 47 preoperatively to 75 at 5 years postoperatively (p < 0.001). Conclusions: In this large consecutive series, UKA demonstrated excellent long-term survivorship, with an approximately 1% annual risk of revision through 15 years. Technology assistance, a fixed-bearing implant design, and high surgeon volume were each associated with a lower risk of revision, underscoring the importance of operative technique and implant selection in achieving durable outcomes. Level of Evidence: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.