CAN YOU PREDICT WHICH ‘ROUTINE’ CLOSED ANKLE FRACTURES REQUIRE EXTERNAL FIXATION RATHER THAN CAST IMMOBILIZATION? A RETROSPECTIVE MATCHED COHORT STUDY

Abstract

IntroductionA subset of patients in cast awaiting fixation of ankle fractures require conversion to delayed external fixation (dEF). We aimed to evaluate the effect of delayed versus planned external fixation (pEF), then identify objective characteristics contributing to need for conversion.MethodWe extracted data from our booking system to identify all ankle external fixation procedures between 2010 to 2022. Exclusions included open fractures, the skeletally immature, and pilon or talus fractures. Fractures were classified using the AO/OTA classification, then a matched cohort was identified based on fracture classification. We compared the planned, delayed and matched cohorts for demographics, posterior malleolar fragment (PMF) ratio, and degree of displacement at presentation.ResultsWe identified 25 pEF, 42 dEF, and 67 matched patients. Ankles with dEF had a 3.8 day longer time to ORIF from presentation than those who had pEF, and had an infection rate of 9.5%, compared to 4% in the pEF group. Two patients in the dEF group required further operative intervention. There were no infections or reoperations required in the pEF or matched groups. The dEF group were more likely to have ≥2 reductions (OR 4.13), a PMF ratio of >0.23 (OR 5.07), and have increased displacement at time of injury on lateral (32% vs 19%) and AP (62% vs 36%) radiographs.DiscussionOur retrospective study highlights the longer time to operation and increased infection rates of patients who do not get timely external fixation. We propose a series of objective parameters that predict failure of cast treatment and guide the surgeon to consider planned external fixation in some ankle