Fig 3A–C.

(A) A large sphere encompassing any impinging portion of the rim is centered in the acetabulum. (B) The portion of the acetabulum in this sphere is disconnected from the rest of the pelvis so that only the acetabulum can be rotated. The two pieces are shown separated here for emphasis, but the acetabulum is actually still centered at the same spot of the pelvis. (C) The acetabulum then is retroverted 10°, shown here separated from the pelvis for emphasis and comparison with Illustration B.