68 patients with an unstable syndesmosis injury following an external rotation ankle fracture with posterior malleolus involvement were randomized to the management of the syndesmotic injury with either anterior-inferior tibiofibular ligament repair and augmentation with anchor-anchor rope construct, or standard trans-syndesmosis screw fixation. The fracture in both groups was fixed with plates and screws. Patients were followed up at 3, 6 and 12 months postoperatively. Radiographic imaging demonstrated no significant differences in the quality of reduction, loss of reduction, and the incidence of complications between groups. Pain scores did not significantly differ between groups at any time point. Olerud-Molander scores were significantly higher in the anterior-inferior tibiofibular ligament repair and augmentation group compared to the trans-syndesmosis screw group at 3 and 6 months, as well as the range of motion from 6-12 months postoperatively.