Clinical outcomes following mobile-bearing unicompartmental knee arthroplasty in patients with varying degrees of perioperative alignment change.

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.