Fig. 3A–B.

The acetabular sector angle (ASA) is formed by the intersection of a line connecting the femoral head center and the acetabular edge with a horizontal line. (A) The anterior and posterior ASA were determined in the acetabular sector angle was measured in axial plane passing through the femoral head center, and the sum of the anterior and posterior ASA was defined as the axial ASA. (B) Superior ASA was measured in the coronal plane passing through the femoral head center.