The Association Between Lateral Radiographs and Axial Computed Tomography of Posterior Malleolar Fractures as a Tool for Predicting Medial Malleolar Extension: A Multi-Center Retrospective Analysis.

Abstract

Posterior malleolar fractures are often part of complex ankle fracture patterns. Radiographs and computed tomography are often obtained in the preoperative setting. In this study, we compared measurements from lateral ankle radiographs with measurements on axial computed tomography. We hypothesize that there is an association between measurements taken on lateral XR and certain fracture morphology such as medial extension and that measurements taken on lateral XR can be used to predict likelihood of medial extension type fractures. A multi-center retrospective analysis was performed involving patients with trimalleolar ankle fractures treated at two large urban healthcare systems ranging from January 1, 2010 to November 1, 2019. A total of 279 patients met criteria including 186 females and 93 males aged 18 to 90 with an average age 55. Four reviewers measured continuous variables on lateral radiograph and axial computed tomography: posterior malleolus fracture height, articular surface length, medial-lateral width, and anterior-posterior depth and then agreement was assessed via intraclass correlation coefficient. Pearson correlations were calculated for all pairwise combinations of measurements. Two fracture classification systems were then evaluated for association with the continuous variables. Lateral height was divided into quartiles and analyzed for the degree of association. Positive correlation was found between lateral height and axial depth/axial width. Taller lateral height values were statistically associated with medial extension type fractures. Lateral height 24.5mm-29.5mm is 3.1x higher, and lateral height >29.5mm is 8.6x more likely to have medial extension when compared to shorter lateral heights(<20.5mm). Based on these findings we suggest increased usage of pre-operative CT and evaluation for the use of posteromedial approaches in the setting of taller lateral height fracture patterns(>24.5mm) as seen on lateral XR.