Intra-articular fragment mapping in associated both-column acetabular fractures

Introduction: Associated both-column acetabular fractures (ABC-AF) are complex. A detailed description of the morphology of the articular surface of the acetabulum is not reported. This study was designed to describe the morphology of the intra-articular fragments using a fracture mapping technique to provide reference in more appropriate approach selection in surgical treatment of the fractures.

Materials and methods: Three-dimensional reconstruction CT images from 100 cases of ABC-AFs were retrospectively analyzed using Mimics and 3-matic software. The fractured as well as the reduced three-dimensional models were investigated, and the intra-articular fragments were identified. The distribution of the fracture lines of each main fragment and the overlapping lines of all the fragments were verified on the images.

Results: The articular surface of ABC-AFS consist of three types of fragments: column fragment (CF), wall fragment (WF) and isolated fragment (IF), with the total number varying from 2 to 6. CF characterized by long fracture lines exited to periphery of innominate bone while the lines of WF were confined to the walls. IF was a free fragment found in the dome and in the quadrilateral plate. The surface was composed only by CFs in 17 cases (17%), by CFs and WFs in 59 cases (59%) and by all fragments in 24 cases (24%). The distribution of the overall fracture lines was a "dumbbell shaped" pattern, starting from the infero-anterior aspect, passing through the junction of the fossa to the anterior lunate surface and extending into the posterior region of the acetabulum.

Conclusions: The articular fragments of ABC-AFs were composed of CFs, WFs and IFs. The junction of the fossa to the anterior lunate surface and the posterior region of the rim were mostly involved. The location of the articular fragments and their connections to the periphery of the innominate may be considered in selection of approaches.