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

Background:
The effect of total knee arthroplasty (TKA) on the ankle joint is not entirely clear. To date, only a few studies have been conducted on this topic, with conflicting outcomes. The purpose of this study was to assess postoperative changes in the coronal alignment of the ankle joint in patients undergoing TKA for various degrees of knee deformity.

Methods:
This 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 one of three groups according to the degree of knee coronal alignment correction that was 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 hip-knee-ankle (HKA) angle, tibial plafond inclination (TPI), talar inclination (TI), and tibiotalar tilt (TTT) angle.

Results:
Satisfactory correction of the knee deformity and restoration of the mechanical axis were achieved in all three groups (p<0.01). Significant changes in ankle alignment, specifically with regard to TPI (9.5°±6.9, p<0.01) and TI (8.8° ±8.8, p=0.03) were noted in Group 3 patients (≥ 10° valgus correction) compared to the other two groups. Regardless of the degree of knee deformity correction, TKA did not lead to significant changes in the TTT angle.

Conclusion:
A correction of ≥10 degrees in a genu valgum deformity can affect ankle joint alignment, leading to alterations in the tibial plafond (TPI) and the talar inclination (TI). These findings need to be taken into consideration in assessing candidates for TKA, especially for patients with concomitant deformities of the ankle and/or hindfoot joints.