Clinical Outcomes Following Posterior Malleolus Fixation in Trimalleolar Ankle Fractures: A Prospective Study

Posterior malleolus (PM) fractures are frequently caused by pronation or supination injuries with an external rotation component to the ankle. Historically, fixation of the PM was not considered essential if it involved less than 25% of the tibial articular surface. However, studies have now shown that trimalleolar fractures fare worse than bimalleolar fractures. This study primarily aims to evaluate the clinical outcomes of trimalleolar fractures, focusing on posterior malleolus fixation regardless of the fragment size.

A prospective observational study was undertaken to investigate the efficacy of PM fixation at a tertiary care centre from October 2020 to December 2022. All participants underwent pre-operative radiographs and were classified according to the Lauge-Hansen system. Sixteen consecutive patients underwent the posterolateral approach to reduce and stabilise the PM, utilising either a buttress/antiglide plate or a posterior-to-anterior (PA) screw, in conjunction with fixation of the medial and lateral malleoli. Patient characteristics, injury specifics, surgical details, and complications were documented. Clinical outcomes were assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) scoring system.

The study cohort included 16 patients with an average follow-up of 18 months. The AOFAS scores indicated excellent outcomes in six cases, good outcomes in eight cases, and a fair outcome in two cases. PA lag screw fixation was used in seven patients when the fracture fragment was large enough with three excellent, three good and one fair outcome. While buttress/antiglide plate fixation was employed in nine patients when the fracture fragment was small or comminuted with three excellent, five good and one fair outcome. One patient developed a superficial infection, which was managed with debridement, and another patient experienced malunion. Both of these patients had a fair outcome.

A posterolateral approach allows fixation of the posterior malleolus and fibula through a single incision, ensuring anatomical reduction and stable fixation. This method yields excellent outcomes with minimal complications, though further research with larger studies is needed.