Fig. 5.

(A) A hemipelvis with a tilt within the normal range. (B) A hemipelvis with posterior tilting. The distance between the free margin of the acetabular labrum to the femoral head–neck junction (arrows) is longer than that in a normal pelvis (i.e., distance B > distance A). (C) The free margin of the acetabular labrum is more likely to be trapped by the femoral head into the intra-articular space in a posteriorly tilted pelvis than in a normal pelvis because in the tilted pelvis, the distance where the free margin of the acetabular labrum runs across the surface of the femoral head is longer when the hip joint bends. (D) Abnormal stress caused by inversion of the acetabular labrum to the superolateral portion of the femoral head and lateral part of the acetabulum.