Pre-operative radiographic findings predicting concomitant posterior malleolar fractures in tibial shaft fractures: a comparative retrospective study

BACKGROUND A concomitant tibial shaft and posterior malleolar fracture is a type of regular compound fracture. The associated posterior malleolar fractures are mostly occult fractures, which often do not show a fracture line on ordinary films, and thus lead to a high rate of misdiagnosis. The aim of the present study was to investigate factors helpful for the pre-operative detection of concomitant posterior ankle fractures using the ipsilateral radiographic tibia and fibula shaft fracture characteristics. METHODS One hundred eleven adult patients with tibial shaft fractures were selected using inclusion and exclusion criteria. Pre-operative ankle radiographs and computed tomography (CT) scans were obtained for all patients, and clinical data, including age and gender, were collected. Patients were divided into two groups (posterior malleolar fracture and no posterior malleolar fracture groups). Fracture height, fracture length, fracture shape, and Haraguchi type of posterior malleolar fracture were measured on radiographs and CT images, and were compared between the two groups. Multiple logistic regression analysis was performed to identify the factors that significantly contributed to concomitant posterior malleolar fractures. Receiver operating characteristic curves were calculated, and cut-off values were used to predict posterior malleolar fractures on pre-operative imaging measurements. RESULTS Of the 111 patients with tibial shaft fractures, 42 (37.8%) had a concurrent posterior malleolar fracture. Age, gender and affected side were not significantly different, but tibial fracture location, fracture length, and fibular and tibial fracture shape were significantly different between the two groups. In the multiple logistic analysis, tibial fracture location, fracture length, and tibial fracture shape were shown to be significant factors contributing to posterior malleolar fractures. Receiver operating characteristic curves showed that the status of tibial shaft fractures is closely related to the associated posterior malleolar fracture. CONCLUSION Ipsilateral posterior ankle fractures are commonly associated with tibial shaft fractures, especially spiral-type injuries. An analysis of the imaging features of such fractures and evaluation of the diagnostic value of various methods can provide imaging basics for the development of accurate and appropriate treatment options.