Fig. 3

Relation between acetabular dysplasia and retroversion in all subjects with focal concavity of posterior superior acetabulum. Focal concavity of posterior superior acetabulum was evaluated by three-dimensional CT image. Acetabular dysplasia was determined by lateral center edge angle <25°, Tönnis angle >10°, or anterior center edge angle <25° on standing pelvic radiographs. Acetabular retroversion was judged by version angle <0° at the one-fourth cranial level of axial CT image