Diagnosing childhood acetabular dysplasia using the lateral margin of the sourcil.

The purpose of this study was to evaluate the lateral edge of the acetabulum and locate the most accurate marking point on a plain radiograph when measuring the acetabular index (AI) and the center-edge (CE) angle. We studied the radiographs of 53 patients with unilateral developmental dysplasia of the hip (DDH), all of whom were treated by closed reduction. In addition to plain radiographs, eight patients had magnetic resonance imaging (MRI) studies, 16 had three-dimensional computed tomography (3-DCT) studies, and six underwent arthrographic studies. We found that the most lateral bony margin of the acetabular roof on plain radiograph represents the anterolateral portion of the acetabulum. The lateral end of the sourcil indicates the lateral margin of the mid-superior portion of the acetabulum. To reduce intra- and interobserver errors, we suggest that when measuring the AI and the CE angle, physicians clearly indicate in the medical records which of the two marking points was used.