Comparison of Time-dependent Changes in Syndesmotic Reduction Between Suture-button and Screw Fixation for Ankle Malleolar Fractures with Tibiofibular Diastasis

Abstract

Category: Trauma Introduction/Purpose: Reduction of the tibiofibular syndesmosis is one of the most important factors that affect the clinical outcome after ankle malleolar fractures with syndesmotic diastasis. Recent studies have shown that suture-button fixation can yield better syndesmotic reduction than screw fixation immediately after surgery. However, the time-dependent change in the reduction for each fixation method has not been well studied. The purpose of this study was to compare the postoperative changes in the syndesmotic reduction after surgical treatment of ankle malleolar fractures between suture-button fixation and screw fixation using bilateral computed tomography. Methods: Patients who sustained ankle malleolar fractures with tibiofibular diastasis and underwent tibiofibular fixation were included. Suture-button fixation (Group B; n=14; age, 39 years) was used between 2015 and 2016, and syndesmotic screw fixation (Group S; n=20; age, 35 years) was used between 2012 and 2014. The syndesmotic screws were routinely removed. Patients underwent CT scanning of the bilateral ankles at 2 time points: at 2 weeks and 1 year after fracture fixation. Side-to-side differences in the anterior and posterior tibiofibular distances, and anteroposterior fibular translation were measured. Syndesmotic melreduction was defined as a side-to-side difference?2 mm in either of the measurements. The changes in each measurement and incidence of malreduction for each group were assessed using the Wilcoxon signed-ranks test and McNemar’s test. Differences between the two groups at each time point were also compared. Results: At 2 weeks after fracture fixation, the side-to-side difference in anterior tibiofibular distance was significantly wider in Group B (1.9 mm) than in Group S (0.7 mm) (p=0.03). Additionally, the fibulas were more translated posteriorly in Group B (1.5 mm) than in Group S (0.2 mm). At 1 year, the anterior tibiofibular distance decreased to 0.8 mm in Group B (p=0.09). On the contrary, it significantly increased to 1.9 mm in Group S (p=0.002). In Group B, the incidences of malreduction were 4/14 and 2/14 at 2 weeks and 1 year, respectively (p=0.74). Two ankles, which were malreduced at 2 weeks, changed to a reduced syndesmosis at 1 year. In Group S, the incidences were 8/20 and 9/20 at 2 weeks and 1 year, respectively (p=0.35). Conclusion: Syndesmotic alignment changed over time in both fixation methods, however, the patterns of change were different. Using suture-button fixation, the anterior tibiofibular distance decreased over time. As a result, the widened syndesmoses at 2 weeks changed to reduced syndesmoses at 1 year. On the contrary, using tibiofibular screw fixation, the anterior tibiofibular distance widened after screw removal. Our result suggests that the flexible suture-button fixation allows the fibula to move to the optimal location over time.