Radiography

Accurate diagnosis of acetabular fractures requires four views of the pelvis:

• standard anteroposterior
• two 45 degree oblique views to show the anterior and posterior columns distinctly

The advent of CT scans has made the diagnosis and classification of acetabulum fractures much easier. CT axial images are superior to plain radiographs in evaluating the following in acetabulum fractures: (1)

Extent and location of acetabular wall fractures

Presence of intra-articular fragments

The orientation of fracture lines

The identification of additional fracture lines

Rotation of fracture fragments

The status of posterior pelvic ring

Marginal impaction.

2D images are better used for evaluation of the fracture patterns, while 3D imaging may help less experienced surgeons.(1)

Note - dynamic stress X-rays can also be obtained to evaluate for hip stability, usually when there is a fracture-dislocation involving the posterior wall. The patient is supine with the hip extended and in neutral rotation, then the hip is flexed to 90 degrees, and a manual force is applied while taking plain films. Any evidence of hip subluxation means hip instability. (2)

Reference

1. O'Toole RV et al. Evaluation of computed tomography for determining the diagnosis of acetabular fractures. J Orthop Trauma. 2010 May;24(5):284-90.
2. Moed BR, Ajibade DA, Israel H. Computed tomography as a predictor of hip stability status in posterior wall fractures of the acetabulum. J Orthop Trauma. 2009 Jan;23(1):7-15.