Technical aspects of the syndesmotic screw and their effect on functional outcome following acute distal tibiofibular syndesmosis injury.

INTRODUCTION Much of the currently available data on the technical aspects of syndesmotic screw placement are based upon biomechanical studies, using cadaveric legs with different testing protocols, and on surgeon preference. The primary aim of this study was to investigate the effect of the level of syndesmotic screw insertion on functional outcome. Further, the effects of number of cortices engaged, the diameter of the screw, use of a second syndesmotic screw and the timing of removal on functional outcome were tested. MATERIAL AND METHOD All consecutive patients treated for an ankle fracture with concomitant acute distal tibiofibular syndesmotic injury that had a metallic syndesmotic screw placed, between 1 January 2004 and 31 December 2010, were included. Patient characteristics (i.e., age at injury and gender), fracture characteristics (i.e., affected side, trauma mechanism, Weber fracture type and number of fractured malleoli), and surgical characteristics (i.e., level of screw placement, screw diameter, tri- or quadricortical placement, number of syndesmotic screws used and the timing of screw removal) were recorded. Outcome was measured using validated questionnaires, which were sent by post, and consisted of the American Orthopaedic Foot and Ankle Society ankle-hindfoot score (AOFAS), the Olerud-Molander Ankle Score (OMAS) and a single question Visual Analog Scale (VAS) for patient satisfaction with outcome. RESULTS During the 7-year study period, 122 patients were treated for syndesmotic injury. A total of 93 patients (76%) returned the questionnaire. The median follow-up was 51 months. The outcome scoring systems showed an overall score for the entire group of 92 points for the AOFAS, 77 for the OMAS and 8.2 for the VAS. Outcome was statistically significantly influenced by the number of fractured malleoli, age, trauma mechanism and the level of screw insertion. CONCLUSION Overall, the functional outcome of acute syndesmotic injuries treated with a syndesmotic screw was good and mainly influenced by patient and fracture characteristics. Most different technical aspects of placement appeared not to influence these results. Only screw placement above 41 mm negatively influenced outcome.