Abstract
BACKGROUND: Although favorable survival and good outcomes have been reported with Oxford unicompartmental knee arthroplasty (UKA), the effect of perioperative alignment change on patient-reported outcome measures (PROMs) remains controversial. In this study, we investigated the impact on outcomes and survivorship of medial UKA with significant perioperative alignment changes. METHODS: We retrospectively reviewed 316 patients with anteromedial OA who underwent primary Oxford UKA. The patients were divided into three groups (A, n = 146; B, n = 98; C, n = 72), Group A: mild varus alignment change (≤ 4°), Group B: moderate varus alignment change (> 4° and < 7°) and Group C: large varus alignment change (≥ 7°). The mean follow-up period was 2.9 years (range: 1.9-4.5 years). Patient history, as well as pre- and post-operative KOOS-JR (Knee Injury and Osteoarthritis Outcome Score for Joint Replacement) scores and Kujala scores, were obtained through chart review. Continuous data were compared using analysis of variance (ANOVA). Chi-squared tests were used to compare discrete variables. Linear regression was conducted to estimate the effect of alignment change on the improvement of the KOOS-JR score. RESULTS: In all groups, the KOOS-JR and Kujala scores showed significant improvement after surgery. At the 1-month follow-up, the difference in mean KOOS-JR score between the groups was not significant (P > 0.05). The Kujala score of Group A was highest (P < 0.05), and the difference between Group B and C was not significant (P > 0.05). In the 2-year follow-up, mean KOOS-JR and Kujala outcomes were comparable among groups (P > 0.05). The KOOS-JR MCID in each group was 71% in Group A, 73% in Group B, and 85% in Group C. Linear regressions showed no statistically significant relationship between the variation of perioperative alignment and KOOS-JR scores (P > 0.05). The 2-year survival rate for the entire cohort was 100%. CONCLUSION: UKA with a low angle of perioperative varus deformity change would have a rapid improvement of functional scores, especially the relief of anterior knee pain. Severe varus deformity with large perioperative alignment change can still obtain desirable outcomes. Video Abstract.