An In Vivo Biomechanical Analysis of Syndesmotic Surgical Repair in Elite Athletes: Screw versus Suture Button Fixation

CATEGORY: Trauma; Basic Sciences/Biologics INTRODUCTION/PURPOSE: Syndesmotic injuries account for 1-11% of all ankle sprains and are the most predictive factor of chronic ankle dysfunction 6 months after injury. Common surgical techniques include screw fixation (the ‘gold standard’) and dynamic fixation with a suture button device, which may lead to better clinical outcomes than rigid screw. To date, there are no studies comparing the in vivo biomechanics of suture button and rigid screw syndesmotic fixation, and no report of the correlations between biomechanics and patient outcomes. The goal of this study is to characterize the biomechanics of the native ankle syndesmosis, rigid screw fixation, suture button fixation, along with associated patient-reported outcomes. This study will elucidate mechanisms for improved patient-reported outcomes based on the fixation method. METHODS: 6 patients (average age:23.6, 4M/1F, 2 suture button, 2 screw fixation and 1 hybrid) consented to participate in this IRB-approved study. After being medically cleared to return to full athletic participation, each participant performed seven movements (two single leg hops (straight and lateral), two alternating single-leg push-offs (front-to-back and side-to-side), vertical jumping, running, and walking within a biplane radiographic system (Figure 1). A validated volumetric model-based tracking system matched patient-specific 3D bone models (obtained from CT) to the synchronized biplane radiographs (Figure 1). Six degree of freedom ankle kinematics were determined for each movement and for the repaired and contralateral ankle of each participant. Patient reported outcomes were also measured using the Foot and Ankle Ability Measure (FAAM) and a Visual Analogue Scale (VAS). RESULTS: The results show that the screw fixation (-0.99 mm) has greater tibiotalar lateral-medial translation of the injured side relative contralateral healthy side compared to the tightrope fixation (-0.73 mm) and hybrid (.05 mm). For the syndesmosis translation, the screw fixation (2.00 mm) also exhibits greater total magnitude of translation compared to the tightrope ((-0.44 mm) and hybrid fixation (1.02 mm). CONCLUSION: This study shows that the screw fixation exhibits greater translation of the syndemosis and lateral/medial translation of the Talus. This may suggest that this method is inferior to the tight-rope and hybrtid. Future studies will include all the motions and more subjects.