Acetabular version angle

The acetabular version angle or acetabular anteversion angle is a measurement used on cross-sectional imaging especially pelvic CT for the assessment of acetabular morphology.

Usage

The acetabular version angle is influenced by pelvic obliquity and pelvic tilt, which might lead to measurement errors if not considered ^1,2. It is also influenced by physeal closure and with increasing distance from the acetabular roof ³.

Measurement

Acetabular version is measured as the angle between a line connecting the anterior acetabular margin with the posterior acetabular margin and the perpendicular to a transverse reference line either through the femoral head centers, the posterior acetabular walls or the respective posterior aspect of the ischial bones ^1-3.

Interpretation

Physiologic acetabular anteversion angles in adults have been declared in the 12° to 20° range ^5-7, but seem to be more variable ^3,8 probably not least because of the dependence of the distance to the acetabular roof ³.

The following mean and standard deviations have been suggested for measurements in a pediatric population (age group 9-18) at the level of the center of the femoral head by a study group ³:

• before physeal closure: 14° ± 4°
• after physeal closure: 19° ± 4°