Evaluation of ankle fracture classification systems in 193 trimalleolar ankle fractures

PURPOSE: Different classification systems have been developed for ankle fractures. In recent years, the posterior malleolus has gained in importance and led to computed tomography (CT)-based classification systems. The aim of the study was to analyse their reliability, fracture patterns and influence on treatment strategy. METHODS: Patients with a trimalleolar ankle fracture treated between 2011 and 2020 with preoperative radiographs and CT images were included. The blinded images were independently classified by three reviewers according to the AO/OTA, Herscovici, Bartoníček, Mason and Haraguchi classifications. The interobserver reliability was calculated by Fleiss' kappa (κ). CT images were analysed to determine the dimensions of the posterior malleolus fragments. Patient registries were reviewed regarding the treatment data. RESULTS: A total of 193 patients were included. The AO/OTA classification showed almost perfect inter- and intraobserver reliability (Fleiss’ κ = 0.86, 95% CI 0.82–0.90). Regarding the posterior malleolus, the Bartoníček classification demonstrated the highest reliability (Fleiss’ κ = 0.78, 95% CI 0.73–0.83). The Herscovici classification only reached moderate reliability for medial malleolus fractures (Fleiss' κ = 0.59, 95% CI 0.54–0.65). There was a trend towards direct fixation of the posterior malleolus in the last 3 years of the observation period (OR: 2.49, 95% CI 1.03–5.99). CONCLUSION: In trimalleolar ankle fractures, the AO/OTA classification is a reliable system to characterize the type of fracture, but it fails to provide solid information about the posterior malleolus. Nowadays, treatment recommendations for trimalleolar ankle fractures focus on the configuration of the posterior malleolus; therefore, the results of this study advocate the use of the Bartoníček classification as a reliable tool to guide treatment.