Table 3.

Position of the posterior superior iliac spine (PSIS) related to the level of the adjacent vertebra

Level	Vertebral level of PSIS	Number of patients at the level
		AP	LAT
1	L4/L5	3	0
2	L5	112	3
3	L5/S1	59	4
4	S1	15	96
5	S1/S2	1	52
6	S2	0	35

Assessment done on the antero-posterior (AP) and lateral (LAT) spinal radiograph. The L5 is the mode value in the AP group, while the S1 is the mode value in the LAT group. The medians of the AP group (median = 2.0) and the LAT group (median = 4.0) differ significantly (Wilcoxon matched pairs test, P < 0.001). N = 190