A method for calculating acetabular anteversion in children

A method of calculating the degree of anteversion of the acetabular fossa is described. A posterior-anterior projection of the prone pelvis with a long focus film and focus object distance is used. The distance between the anterior and posterior rims of the fossa as projected on the films is measured and then divided by a distance equivalent to the diameter: this yields the sin of the anteversion angle. The angle is rapidly calculated with a pocket calculator.