Validation of three classification systems for posterior malleolus fractures of the ankle

Purpose A number of classification systems exist for posterior malleolar ankle fractures. The user reliability of these classification systems remains unclear. The primary aim of this study was to evaluate the reliability of three commonly utilised classification systems for fractures of the posterior malleolus. Methods Imaging of 60 patients across 2 hospitals with ankle fractures including a posterior malleolar fragment was identified. All patients had undergone plain radiographs and computed tomography of their injured ankle as part of their normal standard of care. 9 surgeons including pre-resident/registrar level, resident/registrar level, and attending/consultant level applied the Haraguchi, Bartoníček, and Mason classifications to these fractures, at two timepoints, at least 4 weeks apart. The order was randomised between assessments. Inter-rater reliability was assessed using Fleiss’ κ and standard error (SE). Intra-rater reliability was assessed using Cohen’s κ and standard error (SE). Results Inter-rater reliability (Fleiss’ κ ) was calculated for the Haraguchi classification as 0.588 (SE 0.023), for the Bartoníček classification as 0.626 (SE 0.019), and the Mason classification as 0.541 (SE 0.098). Intra-rater reliability (Cohen’s κ ) was 0.761 (SE 0.098) for the Haraguchi classification, 0.761 (SE 0.091) for the Bartoníček, classification, and 0.724 (SE 0.096) for the Mason classification. Conclusions This study reports the inter-rater and intra-rater reliability for three classification systems for posterior malleolus fractures. Based on definitions by Landis and Koch (Biometrics 33:159-174, 1977), inter-rater reliability was rated as ‘moderate’ for the Haraguchi and Mason classifications and ‘substantial’ for the Bartoníček classification. Similarly, the intra-rater reliability was rated as ‘substantial’ for all three classifications.