Figure 1

Spinal parameters on standing radiograph. Thoracic kyphosis (TK) and lumbar lordosis (LL) are defined as the angle between the cranial endplate of Th1 and the caudal endplate of Th12, the cranial endplate of L1 and the caudal endplate of L5, respectively. Sacral slope is defined as the angle between the sacral endplate and the horizontal plane. Sagittal vertical axis (SVA) is distance from C7 plumb line from the center of the C7 to the posterior edge of the upper sacral endplate. Pelvic tilt (PT) is defined as the angle is between the line connecting the midpoint of S1 endplate to the center of the femoral head and the vertical line of S1 endplate. Pelvic incidence (PI) is defined as the angle between the line perpendicular to the middle of the cranial sacral endplate and the line joining the middle of the cranial sacral endplate to the center of the femoral head axis.