Effects of Supramalleolar Osteotomy on Abnormal Internal Rotation of the Talus in Varus Ankle Osteoarthritis

Abstract

Category: Ankle Arthritis; Basic Sciences/Biologics Introduction/Purpose: Varus ankle osteoarthritis, which is induced by asymmetric joint load in the ankle due to varus malalignment and characterized by a loss of cartilage in the medial talar dome or medial clear space in the ankle mortise, accounts for a large proportion of ankle osteoarthritis osteoarthritis. Realignment surgery, such as supramalleolar osteotomy (SMO) is an effective surgical procedure for treating varus ankle osteoarthritis. In previous study using weightbearing computed tomography (WBCT) by other group, the abnormal internal rotation of the talus was often seen in patients with varus ankle osteoarthritis. We used axial loading three-dimensional computed tomography (AL 3D CT) to evaluate preoperative and postoperative talocrural joints of patients who underwent SMO to treat varus ankle osteoarthritis. Methods: We performed retrospective analyses of 12 patients (14 feet) who underwent SMO and fibular osteotomy. Fibular osteotomy was performed by scarf osteotomy and the center of hinge was fixed with cortical screw. For SMO, distal tibial medial sharp spike of bone produced after the opening wedge osteotomy was resected and used for the autogenous strut bone graft in the osteotomy gap. Tibial-ankle surface angle (TAS), talar tilt angle (TT), Takakura stage, and tibial-lateral surface angle (TLS) was evaluated with weightbearing radiographs before operation and at 2-year follow-up. Talus rotation ration and presence of medial gutter contact was investigated with AL CT before operation and at 6-month follow-up (Figure A-D : preoperative, E-H : postoperative).Clinical outcomes were assessed based on the preoperative and 2-year follow-up American Orthopaedic Foot & Ankle Society (AOFAS) scale, visual analog scale (VAS) for pain, and Foot and Ankle Ability Measure (FAAM). Results: The mean 2-year follow-up TAS, TT, Takakura stage, and TLS were all significantly different relative to preoperative parameters (P < .05). The mean 6-month follow-up talus rotation ratio was significantly restored compared to preoperative value (P = .001). The mean 2-year follow-up clinical outcomes were all significantly improved relative to preoperative measurements (P = .001). The preoperative talus rotation ratio had moderately positive linear relationships with preoperative Takakura stage and preoperative anterior talar translation (P < .05). Among the variables of interest, preoperative anterior talar translation was most strongly related to the preoperative talus rotation ratio (r = 0.655, P < .05). The postoperative talus rotation ratio had moderately positive linear relationships with postoperative Takakura stage and preoperative talar tilt angle (P < .05). Conclusion: In summary, abnormal internal rotation of the talus in mild to moderate varus ankle osteoarthritis, as observed by AL CT, was significantly restored after SMO combined with fibular osteotomy. SMO yielded successful radiological and clinical outcomes. Based on these results, we believe that correction of abnormal internal rotation of the talus is an important prognostic factor in patients with varus ankle osteoarthritis, and we recommend that clinicians investigate such abnormality perioperatively.