Fig. 2

Schematic diagram of sagittal spine parameters measurement. Thoracolumbar kyphosis (TLK) is the angle between T10 and L2. Lumbar lordosis (LL) is the angle between L1 and S1. Pelvic incidence (PI) is the angle between the vertical line at the midpoint of the upper endplate of S1 and the midpoint of the line connecting the centers of the femoral heads. Sacral slope (SS) is the angle between the upper endplate of S1 and the horizontal line. Sagittal vertical axis (SVA) is the distance from the upper posterior corner of S1 to the C7 plumb line