The Clinical, Radiologic Outcomes of Indirect Anteroposterior Screw Fixation for Posterior Malleolar Fracture in Rotational Ankle Fractures: Comparison with Syndesmosis Fixation

CATEGORY: Ankle INTRODUCTION/PURPOSE: The posterior malleolus is an important soft tissue attachment for the posterior inferior syndesmosis ligament. Recent studies suggested that direct fixation of a sizable posterior malleolar (PM) fracture through posterolateral approach would act to stabilize the syndesmosis and minimize or eliminate the need for trans-syndesmotic fixation. Indirect anteroposterior (AP) screw fixation was an alternative method, which represent relatively low complication. However, there were few studies to evaluate the stability of syndesmosis after indirect anteroposterior screw. The purpose of this study was to define the rate of syndesmotic instability after anteroposterior screw fixation and to compare to the clinical and anatomical outcomes with indirect reduction without fixation. METHODS: We performed a retrospective review between 2009 and 2015 of consecutive patients who underwent surgery with sustained rotational ankle fractures including PM fractures. The exclusion criteria included age <18 years, diabetic neuropathy, tibial pilon fractures, previous ankle fracture repair and not available at minimum 1 year follow up. After the fibula and medial malleolar fracture fixation, the PM was fixed with an AP screw, leaving some of relatively smaller and indirect reduced PM fractures unfixed. Patients were sorted into 2 groups according to the presence (group F) or absence (group N) of AP screw fixation of PM. Then, both groups were divided according to the intraoperative necessity of syndesmotic fixation. The demographics, PM fragment size and syndesmosis widening comparing intact ankle on CT at 1 year postoperatively were recorded for each fracture. The functional outcomes were assessed with the Foot and Ankle Outcome Score (FAOS). RESULTS: A total 126 patients met the study inclusion criteria and underwent analysis. Syndesmotic fixation was required in 17 of 78 (21.8%) and 24 of 88 (72.7%) in group F and N, respectively (p=0.012). Postoperative and follow-up FAOS scores were similar in the four subgroups. The tibiofibular distance on CT was greater in the patients without syndesmotic screw fixation in group F and N (p=0.036 and 0.021, respectively). CONCLUSION: Indirect AP screw fixation of the PM fracture in rotational ankle fractures might be support syndesmotic stability and, thus, lower the rate of syndesmotic fixation. Also, these patients have functional outcomes at least equivalent to outcomes for patients having syndesmotic screw fixation. However, in AP screw fixation group, syndesmosis widening was evaluated without syndesmosis fixation, which could be resulted in degenerative arthritis change. Therefore, our data demonstrate that indirect AP screw fixation of PM fracture alone could not restore syndesmotic stability perfectly.