Patients with varus hindfoot deformity show decreased knee and foot clinical scores after total knee arthroplasty.

Abstract

Evaluating hindfoot alignment using the tibiocalcaneal angle (TCA) is important for understanding the lower limb load axis before and after total knee arthroplasty (TKA). However, no previous studies have investigated the relationship between TCA classification and clinical outcomes after TKA in Japanese patients, including those with TCA varus and valgus deformities. This study aimed to examine the relationship between TCA and knee and foot outcomes following TKA. Patients who underwent primary TKA for osteoarthritis at our university and affiliated hospitals between October 2020 and October 2021 were prospectively evaluated. Based on preoperative TCA, patients were categorized into varus (<0°), intermediate (0-8°), and valgus (>8°) groups. Preoperative, 6-month, and 1-year postoperative clinical outcomes were assessed using the new Knee Society Scoring System (KSS, 2011), Oxford Knee Score (OKS), and the 5-item SAFE-Q (SQ). Statistical analysis was performed using the Kruskal-Wallis test, Dunn's multiple comparison test, and logistic regression analysis. Both the KSS and OKS were significantly lower in the varus group at 6 and 12 months (p < 0.05). At 6 months, the varus group had significantly lower scores on social life functions, shoe-related issues, and overall health (p < 0.05). Logistic regression analysis showed that TCA varus was an independent factor that reduced KSS, OKS, SQ, social life function, and overall health 1-year postoperatively (odds ratios: 2.73, 2.95, 1.90, 2.23; p < 0.05). Overall, our findings suggest that the patients with varus hindfoot deformity show decreases in knee and foot clinical scores following total knee arthroplasty.