Apparent acetabular retroversion occurs when there is pelvic tilt. AP pelvic film should be taken with a film-tube distance of 1.2 m. Distance between the tip of the coccyx and symphysis pubis should be between 1 and 3 cm. I this case it is greater than 3 cm indicating pelvic tilt. This causes apparent cross over between the anterior and posterior margins of the acetabulum.

In this case the medial margin of the acetabulum passes medial to the ilio-ischial line although the center edge angle is normal indicating mild protrusio.