Risk Factors for Posttraumatic Synostosis and Outcomes Following Operative Treatment of Ankle Fractures

Abstract

Background: Distal tibiofibular synostosis is a known but poorly described complication of ankle fractures. The objective of this study was to evaluate the relationship between ankle fracture fixation method and other risk factors in the development of synostosis in posttraumatic operative ankle fractures. Outcomes of patients with no synostosis, incomplete bony bridging, or complete synostosis also were compared. Methods: All operative ankle fractures from a single surgeon’s prospectively collected clinical database were evaluated for the presence of distal tibiofibular synostosis not earlier than 3 months postoperatively. All fractures were treated in a fracture-specific and ligament-specific fashion. Syndesmotic screws, when used, were routinely removed no sooner than 4 months after operation. Patient demographic and medical history data as well as injury and fixation profile were evaluated. Incidence of complications was also reviewed. Foot and Ankle Outcome Score (FAOS) and range of motion (ROM) were compared between the groups. Results: Of the 564 ankle fractures included in the study, 91 demonstrated complete synostosis and 46 demonstrated incomplete bony bridging. Multivariate analysis revealed male sex (odds ratio [OR] = 2.82, P < .001), syndesmotic screw fixation (OR = 2.46, P < .001), and tibiotalar dislocation (OR = 1.74, P = .032) to remain significant independent risk factors for the development of incomplete bony bridging or complete synostosis while adjusting for confounding risk factors. Ankles with synostosis also demonstrated significant reduction in dorsiflexion ( P = .017), plantarflexion ( P = .024), and inversion ( P < .001), though patient-reported outcome measures were equivalent with patients without synostosis. Conclusion: Syndesmotic screw fixation, male sex, and tibiotalar dislocation were significant risk factors in the formation of postoperative distal tibiofibular synostosis, though patient-reported outcome measures seemed equivalent among patients with and without synostosis. Level of Evidence: Level III, case control study of prospectively collected registry data.