Assessment of Bosworth-type fracture by external oblique radiographs

Abstract

Introduction : Bosworth described an unusual fracture dislocation of the ankle with fixed posterior fracture dislocation of the fibula. This ankle fracture variant is often not recognized in initial radiographs and requires a computed tomographic scan for verification. It is usually not reducible by the closed method, and repeated trials induce more damage. The purpose of this study was to verify the usefulness of simple external oblique radiographs for diagnosis of Bosworth-type fracture.

Methods : We reviewed the 327 patients who were diagnosed as unilateral malleolus ankle fracture in 2002 to 2012. Four cases of Bosworth-type fracture were identified. External oblique radiograph was taken initially, immediately after first closed reduction, and after open reduction (3 phases) was undertaken to check the position of fibula in relation with the talus. Fifty cases of bimalleolar fractures and unaffected ankle were compared. Longitudinal bisecting line along the proximal fibula was drawn, and the talus was divided in 2 parts. Anterior and posterior part of the talus was defined as part α and β. The ratio resulted from dividing α with (α + β) implies the fibula position relative to the talus.

Results : Mean α/(α + β) ratio of each phase were 0.4994, 0.4891, 0.2875, 0.2698, and 0.2709. There was significant difference in initial and first reduction phase of Bosworth-type fracture than other groups (P = < .0001). There was no significant difference in open reduced Bosworth-type fracture with bimalleolar fractures and unaffected ankles (P = .528, .602).

Conclusions : An external oblique radiograph provides useful information that can differentiate Bosworth-type fracture from other reducible bimalleolar fractures.