Preoperative Incongruent Subtalar Joint Predicts Less Favorable Clinical Outcome in Total Ankle Arthroplasty

Abstract

Category: Ankle Arthritis; Hindfoot Introduction/Purpose: The clinical role of incongruent subtalar joints on ankle arthritis as well as that on the clinical outcome of surgical treatment such as total ankle arthroplasty (TAA) has not yet been fully understood. The mobile subtalar joint may compensate for malalignment of the arthritic ankle as well as counteract the effect of realigning surgeries. We aimed to determine the clinical effect of incongruent subtalar joint space on TAA. Methods: We retrospectively reviewed 34 patients who underwent TAA, which were grouped according to the status of subtalar joint incongruency. For clinical parameters, American Orthopaedic Foot & Ankle Society (AOFAS) score and pain visual analog scale (VAS) were collected. For radiographic parameters, preoperative talar tilt angle, medial distal tibial angle, and anterior distal tibial angle were measured. A comparison of clinical and radiographic parameters between groups as well as multiple regression analysis was performed to identify contributing factors to the final functional outcome. Results: Interobserver and intraobserver reliabilities of subtalar joint congruency demonstrated substantial agreement. At the final follow-up, the AOFAS score was significantly higher in the congruent group (n=13) compared to that of the incongruent group (n=21), (90.38 vs. 79.57, p=0.007). However, there was no significant difference in pain VAS between the groups at the final follow-up (p=0.181). For measured radiographic parameters, there were no significant differences between the two groups in talar tilt angle, medial distal tibial angle, and anterior distal tibial angle. In multiple regression analysis, the female sex (p=0.006) and incongruency of the subtalar joint (p=0.013) were found to be significant contributing factors to the final AOFAS score. Conclusion: Patients in which the preoperative subtalar joint is incongruent showed less favorable AOFAS scores after undergoing TAA. A thorough preoperative investigation should be taken into the state of the subtalar joint for TAA.