Fig. 1.

Methods of radiographic measurement of pelvic obliquity used on anteroposterior radiographs of the spine including the pelvis: horizontal pelvic obliquity as described by Osebold et al. (angle subtended by a line drawn between the most proximal points on the iliac crest (red) and a line (light blue) drawn parallel to the lower end of the roentgenogram); lumbosacral measurement from Allen and Ferguson (angle subtended by a line drawn through the spinous process of L4 and L5 (green) and a perpendicular (orange) though the iliac crest line); spinopelvic angle as described by Maloney et al. (angle between a line drawn perpendicular (dark blue) from the middle of T1 to S1 (magenta) and the iliac crest line)