Predictors of Satisfactory Outcomes With Fixed-Bearing Lateral Unicompartmental Knee Arthroplasty: Up to 7-year Follow-Up

There is little literature available examining factors that may predict functional recovery after lateral unicompartmental knee arthroplasty (UKA). The purpose of this study was to report short to mid-term effectiveness and evaluate predictors of better outcome following lateral UKA.

We retrospectively reviewed 248 patients (260 knees) who underwent lateral UKA from January 2013, with a mean 5-year follow-up. The primary outcome measures comprised the Hospital for Special Surgery (HSS) score and patient satisfaction. Multivariate regression analyses were implemented to investigate associations between these factors with a satisfactory outcome. Implant survival was estimated by Kaplan-Meier analysis.

Complete follow-up was available for 186 patients (198 knees). At last follow-up, the HSS scores were changed from 52.1 (range, 38-80) preoperatively to 85.6 (range, 61-98) ( P < .001), The OKS improved from 22.8 (range, 16-32) preoperatively to 42.7 (range, 30-47) postoperatively ( P < .01). The 5-year survival was 99.5%. The multivariate analysis showed that the following factors tended to obtain a satisfactory outcome: higher proportion of ASA class I ( P < .001), diagnosis of primary OA ( P = .007), postoperative limb alignment ( P = .007), and higher preoperative HSS score ( P = .019). Patients with valgus 9°-12° reported the highest HSS scores among different subgroups ( P < .001).

Following lateral UKA, postoperative outcomes were satisfactory in patients with lower ASA scores, diagnosis with primary OA, higher preoperative HSS scores and those with postoperative valgus alignment. It is important to understand these correlations to help appropriate patient selection to obtain optimal function after lateral UKA.