Introduction: Lateral compression (LC) is the most common type of pelvic fracture, however there are no clear clinical or radiologic indications to direct conservative versus operative treatment of this pattern of injury. This study aims to determine if improved characterization of LC fracture patterns is possible through 3D radiological analysis.

Methods: CT scans of 61 patients with unilateral LC pelvic fractures were identified. The scans were segmented to generate a 3D model of the pelvis (Amira, MCS Inc). To quantify displacement of the fractured hemipelvis, the spatial orientation of three distinct anatomical landmarks (anteriof superior iliac, posterior superior iliac and ischial spines) on each side of the 3D hemipelvis were identified. Translational and rotational differences between the intact and fractured sides were compared to determine patterns of displacement with respect to a generated mid-sacral sagittal plane.

Results: 36.6% of the LC fractures were classified as non-displaced, 36.6% had an isolated single axis rotation, in another 13.3% had a pure translation with no rotation. 10% demonstrated pure rotational involvement in extension and the remaining patients, 3.3% had dual axis rotation.

Conclusion and Significance: Using 3D geometric analysis we were able to quantify patterns of LC fracture displacements not previously described. We characterized 5 subgroups of displacement patterns in LC fractures of the pelvis. Our 3D findings demonstrated a spectrum of translation and rotation motivating comparison with clinical outcome.