Screw Versus Suture Button in Treatment of Syndesmosis Instability: Clinical and Radiographic Outcomes Using PROMIS and Weight Bearing CT Scan

Abstract

Category: Trauma; Ankle; Sports Introduction/Purpose: Traumatic injuries to the distal tibiofibular syndesmosis are relatively common and can be associated with ankle fractures or occur as purely ligamentous injuries. Unstable syndesmotic injuries require surgical repair, generally performed using either screw or suture button fixation. The superiority of either fixation method remains a subject of ongoing debate. The aim of this study is to compare both clinical and radiographic outcomes of screw and suture button fixation of syndesmosis instability using Patient-Reported Outcomes Measurement Information System (PROMIS) and weight bearing CT scan (WBCT). Methods: Medical records were reviewed to identify patients who had a unilateral syndesmotic injury requiring surgical stabilization and who were at least one year out from injury. Exclusion criteria included patients less than 18 years old, ipsilateral pilon fracture, history of contralateral ankle or pilon fracture or syndesmosis injury, BMI >40, and any neurological impairment. Twenty eligible patients were recruited to complete PROMIS questionnaires and undergo bilateral WBCT scan of both ankles, divided into two groups. In the first group (n=10) the patients had undergone screw fixation of the syndesmosis, while in the second group (n=10) the syndesmosis was fixed using a suture button construct. All patients completed PROMIS questionnaires for pain intensity, pain interference, physical function and depression. Radiographic assessment was performed using axial images of WBCT scan of both the injured ankle and the contralateral normal side at a level one cm proximal to the tibial plafond ( Figure 1 ). Results: At an average follow up of three years, none of the recruited patients required a revision surgery. There was no significant difference between the two groups in terms of the four PROMIS questionnaires (P values ranged from 0.17 to 0.43). In the suture button group, the measurements of the injured side were significantly different from the normal side for the syndesmotic area (P=0.003), fibular rotation (P=0.004), anterior difference (P=0.025) and direct anterior difference (P=0.035). Other measurements of posterior difference, middle difference, direct posterior difference and fibular translation were not significantly different (P values ranged from 0.36 to 0.99). In the screw fixation group, the syndesmotic area was the only significantly different measurement in the injured side as compared to the normal side (P=0.006). Conclusion: Screw and suture button fixation for syndesmotic instability have similar clinical outcomes at average three years follow up as measured by PROMIS scores. Both screw and suture button did not entirely restore the syndesmotic area as compared to the contralateral normal ankle, suggesting some residual diastasis on weight bearing CT. In addition, as compared to screw fixation, the suture button did not seem to restore the normal fibular rotation, with residual external rotation of the fibula noted. Longer clinical follow up is necessary to understand the clinical implication of such malreduction.