Effect of Total Knee Arthroplasty on Coronal Alignment of the Ankle Joint

Abstract

The effect of total knee arthroplasty (TKA) on the ankle joint is not entirely clear. The purpose of this study is to assess postoperative changes in the coronal alignment of the ankle joint in patients undergoing TKA for various degrees of knee deformity. This retrospective study included 107 patients who had undergone TKA for primary osteoarthritis. In all cases, preoperative coronal alignment deformity of the knee was corrected in an attempt to restore the native mechanical axis of the knee. Patients were stratified into 3 groups according to the degree of knee coronal alignment correction achieved intraoperatively: group 1 (<10° varus/valgus correction, n= 60), group 2 (≥10° varus correction, n= 30), and group 3 (≥10° valgus correction, n= 17). Knee/ankle alignment angles were measured on full-length, standing anteroposterior imaging preoperatively and postoperatively and included the following: hip-knee-ankle angle, tibial plafond inclination (TPI), talar inclination (TI), and tibiotalar tilt angle. Significant changes in ankle alignment, specifically with regard to TPI (9.5° ± 6.9°, P < .01) and TI (8.8° ± 8.8°, P= .03) were noted in the ≥10° valgus correction group compared to the other 2 groups. Regardless of the degree of knee deformity correction, TKA did not lead to significant changes in the tibiotalar tilt angle. A correction of ≥10° in a genu valgum deformity can affect ankle joint alignment, leading to alterations in TPI and TI. These findings need to be taken into consideration in assessing candidates for TKA as a possible cause of postoperative ankle pain.