The distance from the posterior limit of the ilium to the S1 alar,pedicle,and pedicle axis; and the distance between the outer table of the ilium and anterior cortex of the sacrum were measured on axial computed tomography scans.

• 在轴位CT上测量髂骨后缘到骶翼、S1椎弓根、S1椎弓根纵轴的距离、髂骨外板与骶椎前缘皮质的距离。