Stability of Distal Tibiofibular Syndesmosis With or Without Fixation of Posterior Fragments in Bimalleolar Fractures

Overview

Background and Rationale: Injury to the tibiofibular syndesmosis in ankle fractures is a major prognostic factor for the development of post-traumatic osteoarthritis. The syndesmosis is frequently involved when posterior tibial marginal fragments are fractured. Intraoperative stability testing determines whether a trans-syndesmotic device (screws, endobutton, or plate) is required. However, trans-syndesmotic devices carry risks such as malreduction, hardware removal, and infection. Anatomical fixation of posterior tibial fragments is hypothesized to restore syndesmotic stability, thereby reducing the reliance on trans-syndesmotic implants. Objective and Hypothesis: The primary objective of this randomized controlled trial is to compare the rate of trans-syndesmotic stabilization device usage between patients undergoing osteosynthesis of posterior marginal fragments and those managed without posterior fragment osteosynthesis. The hypothesis is that syndesmotic stability (defined as non-use of a trans-syndesmotic device intraoperatively) will be significantly higher in the posterior fragment fixation group. Study Design: Multicenter, open-label, randomized, two-arm parallel-group trial conducted at two orthopedic trauma centers (Groupe Hospitalier Diaconesses Croix Saint-Simon and Hôpital Lariboisière).

Study Flow and Procedures: Screening and Randomization: Eligible patients presenting with recent bimalleolar ankle fractures (\< 3 weeks) involving the posterior marginal fragment and syndesmosis (Bartoníček types 2, 3, or 4) are identified in the emergency/trauma department. Following written informed consent, participants are randomized into Group 1 (posterior marginal fragment osteosynthesis) or Group 2 (no posterior fragment osteosynthesis). Preoperative Assessment: Comparative bilateral ankle X-rays and CT scans to confirm fracture classification and baseline metrics (fragment thickness \> 2 mm, height \> 6 mm). Intraoperative Phase: Surgical management of the bimalleolar fracture according to assigned group. Intraoperative stress testing of the syndesmosis is performed to evaluate stability and record the necessity of trans-syndesmotic device placement. Postoperative Follow-up: Day 1 to Week 6: Comparative bilateral CT scan to evaluate fragment and syndesmosis reduction. 3 Months \& 12 Months: Clinical follow-up visits including comparative weight-bearing X-rays, evaluation of AOFAS score, and patient-reported questionnaires (MOXFQ, SF-12). Postoperative complications (infections, neuropathic pain, fibular pain, flexor hallucis longus tendonitis) are systematically recorded throughout the 12-month follow-up.