Fig. 3

Measurement of angles between the sagittal plane and the three lateral faces of the triangular prism. ① Three lateral faces of the triangular prism: A: Quadrilateral plate; B: Posterior acetabular wall; C: Acetabular dome (According to the relevant anatomical measurements [3], the minimum cross section of the acetabular posterior column is mostly located at the level of the middle part of the acetabulum; therefore, at this level, the axial CT images were chosen to be measured.); ② A: Quadrilateral plate; α: Angle between quadrilateral plate and sagittal plane; ③ B: Posterior acetabular wall; β: Angle between posterior acetabular wall and sagittal plane; ④ C: Acetabular dome; γ: Angle between acetabulum and sagittal plane