A Cohort Study of Patients Undergoing Distal Tibial Osteotomy without Fibular Osteotomy for Medial Ankle Arthritis with Mortise Widening

Background: Although the supramalleolar osteotomy can shift the weight-bearing axis laterally, it cannot reconstruct a widened ankle mortise caused by progression of medial ankle osteoarthritis. The aim of this study was to evaluate radiographic and clinical outcomes of distal tibial osteotomy without fibular osteotomy in patients with medial ankle osteoarthritis and mortise widening. Methods: Distal tibial osteotomy without fibular osteotomy was performed in eighteen patients to treat medial ankle osteoarthritis with mortise widening. Fifteen women and three men with a mean age of fifty-seven years (range, forty-nine to sixty-four years) were followed for a mean of thirty-four months (range, twenty-four to sixty-six months). Mortise widening was diagnosed using valgus stress radiographs and intraoperative examination. The clinical outcome was assessed with the American Orthopaedic Foot & Ankle Society (AOFAS) score, visual analog scale (VAS) score for pain, and the ankle osteoarthritis scale (AOS) score. The translation of the talus within the ankle mortise, talar tilt, medial distal tibial angle, and anterior distal tibial angle were evaluated on weight-bearing radiographs made preoperatively and postoperatively. Results: The AOFAS score improved significantly from 78.4 points (95% confidence interval [CI], 74.6 to 80.5 points) to 89 points (95% CI, 86.5 to 90.5 points) (p < 0.001). The VAS score for pain also decreased significantly from 6.7 points (95% CI, 6 to 7.5 points) to 2.7 points (95% CI, 2.3 to 3.3 points) (p < 0.001). The mean AOS score was 29.8 points (95% CI, 22 to 38.2 points) at the latest follow-up. The center of the talus moved laterally within the ankle mortise after the distal tibial osteotomy. The mean medial distal tibial angle changed from 86.6 degrees (95% CI, 85.7 degrees to 87.6 degrees) to 92.9 degrees (95% CI, 91.6 degrees to 94.3 degrees) (p < 0.001), and the mean anterior distal tibial angle changed from 81.1 degrees (95% CI, 78.6 degrees to 83.6 degrees) to 84.3 degrees (95% CI, 81.9 degrees to 86.4 degrees) (p < 0.001). However, talar tilt was not corrected significantly (p = 0.916). Conclusions: Distal tibial osteotomy without fibular osteotomy reduces pain in the short term in patients with ankle arthritis, a widened mortise, and minimal talar tilt.