The contribution of anterior deltoid ligament to ankle stability in isolated lateral malleolar fractures

The treatment of isolated lateral malleolar fractures with deltoid ligament rupture remains controversial. We prospectively analysed 35 patients with isolated lateral malleolar fractures during 2006-2013. Radiography and magnetic resonance imaging (MRI) were performed to assess the degree of reduction, ligament damage, and stability. Internal fixation was performed for all unstable valgus fractures with unacceptable fracture parameters. Fractures with residual valgus instability after fixation underwent anterior deltoid repair. The mean anterior deltoid ligament grade based on MRI was significantly different between the high-grade unstable group and the stable and low-grade unstable groups (p = 0.037 and 0.004, respectively). Postoperative medial clear space measurements were not significantly different between groups. MRI was shown to be a useful tool in the preoperative identification of isolated lateral malleolus fractures prone to valgus instability. In the case of high-grade unstable fractures of the lateral malleolus, repair of the anterior deltoid ligament is adequate for restoring medial stability.