Abnormal preoperative tibiotalar tilt predicts residual ankle pain after mechanical-alignment total knee arthroplasty: A retrospective cohort study.

BACKGROUND: Although mechanical-alignment total knee arthroplasty (MA-TKA) corrects knee deformity and alters hindfoot alignment, its clinical relevance for ankle symptoms remains unclear. This study aimed to clarify the longitudinal course of ankle pain, coronal ankle-hindfoot alignment changes, and predictors of residual ankle pain following MA-TKA.

METHODS: This retrospective cohort study included 106 patients (134 knees) who underwent primary MA-TKA for knee osteoarthritis (OA). Standing whole-leg radiographs were obtained preoperatively and at 2 months postoperatively. Ankle OA was graded using the Takakura-Tanaka classification. Coronal alignment parameters included the hip-knee-ankle angle, tibiotalar tilt angle (TTA), tibial plafond inclination angle, talar inclination angle, and hindfoot alignment angle. Normal ranges were defined using healthy controls (40 subjects, 80 knees). Ankle pain was assessed preoperatively and at 6 and 12 months postoperatively using a visual analog scale. KOOS-12 and EQ-5D VAS were collected at intervals. Knee-level logistic regression with patient-clustered standard errors identified predictors of residual ankle pain at 12 months.

RESULTS: Ankle OA was present in 30% of patients. The prevalence of ankle pain decreased from 22% preoperatively to 13% at 6 months and 10% at 12 months. MA-TKA improved coronal ankle-hindfoot parameters (all P < 0.001), except for TTA (P = 0.491). Residual ankle pain was associated with lower EQ-5D VAS but not KOOS-12. Abnormal preoperative TTA independently predicted residual ankle pain (adjusted OR 4.21, P = 0.044).

CONCLUSION: MA-TKA improves coronal ankle-hindfoot alignment and ankle pain in most patients; however, abnormal preoperative TTA identifies patients at increased risk for residual ankle pain.