Syndesmosis and Syndesmotic Equivalent Injuries in Tibial Plafond Fractures.

To identify the incidence and fracture characteristics associated with syndesmotic injury in tibial plafond fractures and report the incidence of posttraumatic osteoarthrosis (PTOA). Retrospective comparative study. Two level-1 academic trauma centers. Of the 735 tibial plafond fractures (OTA/AO 43-B3 and 43-C) treated from January 2006 through December 2015, 108 patients (108/735, 15%) were identified with syndesmosis injury. Either acute or missed syndesmotic injury. PTOA. Fourteen fractures (14/735, 2%) had missed syndesmotic injury. Volkmann fragment of ≤10 mm (P = 0.04) and fibular avulsion fracture (P = 0.05) were significantly more common in missed syndesmosis. Ninety fractures (14/14 missed, 76/94 acute) had greater than 12-month follow-up (mean, 26 months; range, 12-102 months). Nearly all patients with missed syndesmosis injury developed arthrosis (13/14, 93%), and 45% (34/76 fractures) of plafond fractures with acute syndesmosis injury developed arthrosis (P < 0.001). Although controlling for malreduction, patients with missed syndesmosis had significantly more PTOA development (P = 0.018). Controlling for malreduction, patients with syndesmotic fixation and a ≤10-mm Chaput or Volkmann fragment or fibular avulsion fracture (8/31, 26%) were less likely to develop PTOA than if they had a similar fracture pattern without syndesmotic fixation (9/10, 90%) (P = 0.011). Fifteen percent of tibia plafond fractures have a syndesmosis or syndesmotic equivalent injury. Missed syndesmosis injury has a high rate of PTOA development. Patients with a ≤10-mm Chaput or Volkmann fragment and/or fibular avulsion fracture benefit from syndesmotic fixation. Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.