Transitional transverse acetabular fractures: Differences between fractures with a large posterio-superior fragment and the inverse T-fracture-a report of 10 unusual cases

Background Classification of fractures is crucial in decision making and planning of acetabular surgery. Transverse fractures with secondary vertical fracture lines-which constitute either a large posterio-superior fragment (floating dome) or an inverse T with the posterior ileum attached to the axial skeleton-have not been described in detail in the literature. Methods All acetabular fractures at Ullevål University Hospital have been recorded prospectively since 1993 and classified according to Judet Letournel. Results In 10 449 fractures (2%) there was a transverse fracture line through the acetabulum, with an additional vertical fracture line ascending either to the iliac crest or the SI-joint. In 6 of these fractures the vertical line started within the acetabulum, and the posterior part of the ileum with part of the articular surface was attached to the axial skeleton. In 4 fractures the vertical fracture line started posterior to the joint, constituting a very large posterio-superior fragment without any articular surface (a floating dome). Interpretation Open reduction and internal fixation of inverse T-fractures and transverse fractures with a floating dome require different surgical approaches. The latter can be treated through a single approach alone, while the inverse T-fracture may require extensile or combined approaches for adequate reduction and fixation.