Risk Factors for Recurrent Syndesmotic instability after Syndesmotic Screw Fixation in Rotational Ankle Fractures

CATEGORY: Ankle INTRODUCTION/PURPOSE: Rotational ankle fractures often have unstable syndesmotic injuries the require reduction and stabilization. Though multiple studies have focused on methods to assess accurate syndesmotic reduction, fairly high rates of recurrent syndesmosis diastasis were reported. However, there was no study to investigate possible risk factors for syndesmosis widening after surgical fixation. The purpose of this study was to identify the risk factors for recurrent syndesmosis widening after screw fixation. We hypothesized that risk factors for recurrence syndesmosis widening could be identified from patient demographic, intraoperative variables and the extent of the pathologic condition associated with fractures. METHODS: We performed a retrospective review between 2009 and 2015 of consecutive patients who had sustained rotational ankle fractures with intraoperative evidence of syndesmotic instability requiring syndesmotic reduction and stabilization. The exclusion criteria included syndesmosis screws placed for diabetic neuropathy, skeletal immaturity, tibial pilon fractures, polytrauma, open fracture. Patients were sorted into 2 groups according to the presence of recurrent syndesmosis instability which was defined as a difference in the tibiofibular distance of =2 mm between the injured and uninjured ankles on CT at postoperative 1 year and a positive external rotation test. Furthermore, the statistical analysis by binary logistic regression analysis included the significance of various risk factors including age at surgery, sex, diabetes, smoking, body mass index (BMI), dominant side, type of fracture, associated fracture, initial tibiofibular distance on CT, number and size of screws, cortices. 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. The overall postoperative recurrent instability rate was 25.4% (without recurrence group: 94 patients, recurrence group: 32). It was significantly affected by the BMI (p=0.018; adjusted odds ratio, OR, = 30, 6.21) and concomitant posterior malleolar fracture (p=0.040, adjusted OR 3.31). The other variables were not found to be significant risk factors. There was a significant improvement in the mean clinical scores at one years postoperatively (both p < 0.001), but the mean scores in the group with recurrence were significantly lower than those in the group without recurrence (p=0.021) CONCLUSION: Among the risk factors, obesity and concomitant posterior malleolar fracture were significant risk factors for the recurrent syndesmotic instability after syndesmotic screw fixation. The overall results suggest meticulous attention to concomitant posterior malleolar fracture, especially in obese patients.