Comparison of Syndesmotic Malreduction Rate following Trans-Syndesmotic Screw Fixation in SER versus PER Type Ankle Fracture: A Prospective Analytic Study

Abstract

Category: Ankle; Trauma Introduction/Purpose: Syndesmotic injury frequently presents in severe rotational ankle fracture and a trans-syndesmotic screws fixation is commonly used technique. Bases on previous literatures, syndesmotic malreduction rate can occur between 20- 70 percent following traditional trans-syndesmotic screw fixation in all type of ankle fracture. However, there is a little evidence regarding the malreduction rate in each type of ankle fractures. The purpose of this study is to demonstrate malreduction rate of syndesmosis using simultaneously bilateral post-operative CT measurement after trans-syndesmotic screw fixation between supination external rotation and pronation external rotation type ankle fracture. Methods: A prospective comparative study of patients who had acute ankle fracture with syndesmotic injury between January 2015 and December 2017 were enrolled. Lague-Hansen classification was used to classify all patient into 2 groups: SER and PER based on mechanism of injury. Syndesmotic injury was confirmed by ankle arthroscopic examination in all patients and they were treated with ORIF distal fibula using either 1/3 tubular plate or anatomical locking plate under direct visualization of syndesmosis. Syndesmosis was fixed by one or two of 3.5-mm cortical screw with three or four cortices. The accuracy of syndesmotic reduction was evaluated by simultaneously bilateral post-operative CT scan. Syndesmotic reduction was measured using anterior to posterior distance (AP) and medial to lateral distance (ML). A widening of distance between anterior tibia and fibula at 1-cm above the ankle joint more than 2 mm compared to uninjured sides considered a malreduction of syndesmosis. Results: There were 67 patients were enrolled in this study (SER=48 and PER=15). The syndesmotic injury was present 60% (48/70) in SER and 100% (15/15) in PER group respectively. The malreduction was significant higher in PER than SER (2.1% in SER vs 20% in PER). Operative time was 58.2 and 79.2 minutes in SER and PER. The tibiofibular clear space was 4.0mm versus 4.8mm in SER and PER. The AP distance was -0.33mm and -0.51mm and ML distance was 1.91 mm and 1.59mm for SER compared to normal side and 0.19 mm and -0.21 and ML distance was 2.59mm and 1.63mm for PER compared to normal side. There were significant improvements of functional outcomes (FAAM, SF-36, and VAS) but no significant different between the two groups. Conclusion: The incidence of concomitant syndesmotic injury and syndesmotic malreduction rate following trans-syndesmotic screw fixation was significantly higher in PER type compared SER type ankle fracture. The malposition of distal fibula was displaced anteriorly and laterally (undercompression) compared to uninjured side.