Comparison of Clinico-Radiographic Outcome of the 3-Component Salto Total Ankle Arthroplasty According to Degree of Ankle Varus Deformity for End-Stage Ankle Arthritis

Abstract

Category: Ankle Arthritis Introduction/ Purpose: As the popularity of total ankle arthroplasty (TAA) increases, indication of TAA also expands. Recently, the ankles more than 20º of varus or valgus deformity in the coronal plane are treated with TAA. Commonly, patients with ankle osteoarthritis have preoperative varus deformity. However, preoperative varus deformity should be corrected in the coronal plane to avoid residual mal-alignment that leads to instability, insert wear, and clinical failure. In this study, we compare the clinical and radiologic outcome of the Salto mobile bearing 3-component total ankle prosthesis for ankles according to preoperative degree of ankle varus deformity. Methods: TAA was performed in 106 ankles using 3-component Salto total ankle implant from June 2014 to October 2019. A prospectively collected database was used to identify all patients who underwent primary TAA with a minimum 1-year follow-up. All patients were followed up at postoperative three months, six months, at one year and yearly thereafter. Clinical outcome scoring was done pre-operatively and post-operatively. American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot functional score, pain VAS, satisfaction score and clinical range of motion (ROM) were collected along with weight-bearing radiographs of the ankle. Post-operative coronal alignment of the component were evaluated with radiographs. More than 10º of tibial anterior surface angle, talta tilt angle (TTA), tibial axis-talar dome angle (T-TDA), talar dome-ground surface angle (TD- GSA), or tibio-calcaneal angle (TCA) was defined as varus deformity. We classified the enrolled ankles as neutral ( < 10 º), moderate varus (10º~20º), and severe varus groups (>20º). Results: The average follow-up was 21.9 months (range, 12-72). Preoperatively, there were 37 ankles (35%) with neutral alignment, 48 ankles (45%) with moderate varus deformity, and 21 ankles (20%) with severe varus deformity. There were no significant differences in mean pain VAS, AOFAS score, and ROM among the groups (p > 0.05). Overall satisfaction rate (more than satisfied) was 87%, and no significant differences were found among the groups. As to radiographic alignment, there were no significant differences among the groups in T-TDA and TD-GSA (p > 0.05). Concomitant additional procedures such as deltoid release, calcaneal osteotomy, and first tarsometatarsal dorsiflexion arthrodesis were more significantly performed in preoperative varus groups. Conclusion: There was no significant difference in clinical and radiographic outcomes a according to degree of ankle varus deformity in the TAA series using single Salto 3-componenet implant. Postoperative neutral alignment was achieved in all ankles. For favorable long-term outcomes, coronal alignment should be corrected with proper additional procedures in TAA.