Revision from unicompartmental knee arthroplasty to total knee arthroplasty: An analysis of 118 cases at midterm follow-up.

Abstract

Aseptic failure of unicompartmental knee arthroplasty (UKA) often requires revision to a total knee arthroplasty (TKA). However, outcomes following revision from UKA to TKA remain controversial. The purpose of this study was to analyze a large cohort of revisions from UKA to TKA, with emphasis on implant survivorship, clinical outcomes and radiographic results. We retrospectively reviewed 118 aseptic revisions from UKA to TKA performed at a single surgical center between 2016 and 2022. Of these, 50 were required due to progression of osteoarthritis (42%), and 44 for aseptic loosening (37%). The mean age was 67 years, 65% were female, and the mean body mass index was 31 kg/m². Tibial stem extensions were used in 30% of cases, augments in 9%, and a constrained implant in a single patient. The mean follow-up was 6 years (range, 2.7-10.9). The 8-year survivorship free of any re-revision and reoperation was 94% and 92%, respectively. Progression of osteoarthritis was associated with reduced odds of re-revision (odds ratio [OR]: 0.09; p = 0.025) and reoperation (OR: 0.20; p = 0.04). Knee Society Function Scores (KSS-F) improved from 53 to 82 (p < 0.001), with no correlation to implant type, demographics or radiographic patella height. At final follow-up, the mean Oxford Knee and Forgotten Joint Scores were 33 and 54, respectively. The mean modified Insall-Salvati Ratio was 1.56 preoperatively compared to 1.52 at last follow-up (p = 0.07). Aseptic revision from UKA to TKA provides excellent midterm implant survivorship, clinical outcomes, and radiographic results, particularly when performed for the progression of osteoarthritis. Level IV.