Determination of acetabular coverage of the femoral head with use of a single anteroposterior radiograph. A new computerized technique.

We developed a method for the estimation of three-dimensional acetabular coverage of the femoral head with use of only an anteroposterior radiograph of the hip. This technique also allows recalculation of the corrected value for coverage at neutral pelvic tilt. Provided that the acetabulum and femoral head are spherical and congruent, the results are as accurate as those obtained with computerized tomographic reconstruction, the dose of radiation is much lower, and much less time is required for calculation. The hips of 286 normal subjects showed increases with age in both anterior and posterior coverage and backward tilt of the pelvis, along with a decrease in the anterior-posterior ratio of coverage. The proportion of anterior acetabular coverage in female subjects was smaller than that in male subjects. There was more backward tilt of the pelvis and the anterior-posterior ratio of coverage was smaller when the subjects were standing than when they were supine.