Summary

This study revealed that patients undergoing OWHTO demonstrated significantly higher postoperative kneeling ability than those undergoing UKA.

Abstract

Objective

Medial opening wedge high tibial osteotomy (MOWHTO) and unicompartmental knee arthroplasty (UKA) have been both effective surgeries for osteoarthritis of the medial compartment of the knee (knee OA) with varus alignment. Kneeling is a critical function of the knee joints, yet the comparison of postoperative kneeling ability between unicompartmental knee arthroplasty (UKA) and open-wedge high tibial osteotomy (OWHTO) remains unclear. This study aimed to compare the postoperative kneeling abilities of patients with knee OA after UKA and OWHTO. We hypothesized that OWHTO would result in better postoperative kneeling ability compared to UKA.

Methods

This retrospective cohort study included 127 UKA knees and 100 OWHTO knees treated between 2018 and 2022. Clinical data, including Knee Injury and Osteoarthritis Outcome Scores (KOOS) and UCLA activity scores (UCLA), were collected before surgery and at least one-year post-surgery. For patients with bilateral knee procedures, data for each knee were recorded separately. Kneeling ability was assessed using the “Sp5” sub score of KOOS. Postoperative kneeling ability was compared between the UKA and OWHTO groups. Data normality was checked using the Kolmogorov–Smirnov test. Nonparametric continuous variables were presented as medians and interquartile ranges (IQR) and compared using the Mann-Whitney U test. Categorical variables were analyzed using the Fisher's exact test. Postoperative kneeling ability was compared between the UKA and OWHTO groups. Multiple linear regression analysis, with post operative kneeling ability as the response variable, was performed using age at surgery, preoperative knee flexion angle, preoperative UCLA, preoperative OA degree (K-L), preoperative alignment (femorotibial angle), preoperative kneeling ability, and surgical procedure as explanatory variables.

Results

The postoperative Sp5 score was 1 (IQR: 1, 3) in the UKA and 1 (IQR: 0, 2) in the OWHTO groups, indicating that postoperative kneeling ability was significantly better in the OWHTO group compared to the UKA group. Postoperative clinical results were good for both groups, although KOOS ADL, KOOS sports, and UCLA were significantly better in the OWHTO group. The multiple linear regression analysis showed that preoperative kneeling ability and surgical procedure were significant explanatory variables. OWHTO was significantly associated with improved postoperative Sp5 scores.

Discussion

This study revealed that patients undergoing OWHTO demonstrated significantly higher postoperative kneeling ability than those undergoing UKA. OWHTO facilitates easier kneeling in patients with varus knee osteoarthritis compared to UKA. These findings suggest that the choice of surgical procedure is crucial in predicting postoperative kneeling ability, aiding surgeons in their decision-making process.