AO type C ankle fractures with additional posterior malleolus fragment: radiological and functional results of osseous reconstruction of the tibiofibular syndesmosis

Abstract Purpose This study compares the syndesmosis congruity and functional outcomes after syndesmotic reconstruction by open reduction and internal fixation (ORIF) of posterior malleolar fractures (PMFs) sized > 5% versus no fixation in type C ankle fractures. Methods This multicenter prospective cohort study compared ORIF of PMFs (FIX) with no fixation (NO-FIX). Both groups underwent fibular and medial malleolus fixation according to AO principles, with trans-syndesmotic stabilization screws in case of instability. The primary outcome was syndesmotic alignment assessed on post-operative bilateral CT scans. The main secondary outcome measures were patient-reported functional outcome up to 1 year assessed with AAOS and OMAS questionnaires, and complications. Results 26 patients (17 FIX, 9 NO-FIX) were included, with a median PMF size of 20%. Syndesmotic stabilization with fib-tib screws was used in 6% of FIX vs 44% of NO-FIX ( p = 0.03). Anatomical reduction (primary outcome) was achieved in 85% (FIX) versus 29% (NO-FIX, p = 0.02). AAOS and OMAS scores during follow-up were superior in FIX (linear mixed models, p < 0.01). The complication rate was higher in NO-FIX (55% vs. 0%, p < 0.001). Conclusion in this study, ORIF of the PMF resulted in a higher rate of anatomically reduced syndesmosis, lesser need for syndesmotic stabilization screws, better functional outcome and fewer complications compared to no fixation. Fixation of PMFs in suprasyndesmotic fibula fractures with PMFs > 5% may be valuable, but more studies are needed to confirm this hypothesis due to study limitations.