Recurrence of Syndesmotic Diastasis Following Syndesmotic Screw Removal: Does the Time Point of Screw Removal Matter?
Authors: Shoap Seth C. , Polzer Hans , Baumbach Sebastian F. , Herterich Viktoria , Freibott Christina , Vosseller J. Turner 
Published: November 2020

Category: Ankle Introduction/Purpose: Ankle fractures involving disruption to the syndesmotic complex are regularly treated with reduction and syndesmotic screw fixation. When syndesmotic screw fixation is used, it is a common to remove the screw after enough time has passed to allow for sufficient healing of the ligamentous tibiofibular syndesmosis complex. Delayed removal increases the risk of screw loosening or breakage, and more importantly prolongs the time to full weight bearing. Currently, there is little evidence supporting a definitive time point for screw removal. This multicenter study compared two different post-operative protocols following syndesmotic screw insertion. The goal was to determine an optimal time point for screw removal by assessing syndesmotic diastasis between these two institutions, each of which removed the screw at different time points. Methods: Patients from two institutions treated surgically for any type of ankle fracture between 01/2010 and 12/2016 that met the following inclusion criteria were selected: patients suffering any type of an acute, closed ankle fracture, syndesmotic disruption treated using a syndesmotic screw, removal of the syndesmotic screw in the same institution, at least one x-ray (mortise view) prior to screw removal and one following screw removal available for review. Exclusion criteria were open / pilon / tibial shaft fractures. The syndesmotic screw was removed approximately 12 weeks after insertion in the first institution, and 6 weeks after insertion in the second. Four radiographic measurements were performed and averaged by three researchers: medical clear space (oblique), tibio-fibular clear space, and tibio-fibular overlap. An independent samples t-test was conducted to analyze differences in radiographic parameters between the two cohorts. Measurements after syndesmotic screw insertion and at final follow-up after removal were compared. Results: The average time to removal of syndesmotic screw was 79.71 days in institution one (n=31) and 50.92 days in institution two (n=121) (p<0.001). For institution 1 the paired samples t-test revealed no significant differences when comparing measurements prior to syndesmotic screw removal with after screw removal for the tibio-fibular overlap (p=0.088) and tibio- fibular clear space (p=0.312) measurements. A significant difference was observed only regarding the medial clear space (p=0.008). For institution 2, significant differences were observed for all of these measurements (p<0.001). When comparing the measurements after syndesmotic screw removal between the two institutions, the independent samples t-test revealed significant differences in regard to the tibio-fibular overlap (p=0.001) and tibio-fibular clear space (p=0.004) measurements, but not in the medial clear space measurement (p=0.959). Conclusion: Removal of the syndesmotic screw after seven weeks led to a significant loss of reduction of the syndesmosis. In contrast, screw removal after 11 weeks did not lead to a significant loss of reduction. Our results suggest that it is not advisable to remove syndesmotic screws after 7 weeks. It is common to have the patient partial or non-weight bearing until screw removal to avoid screw breakage. To recommend non-weight bearing for 11 weeks will delay return to work and daily activity, and can lead to significant atrophy, however, it does allow for better maintenance of reduction.