Figure 1

Illustration of radiographic parameters measurement. Thoracic kyphosis (TK): the Cobb angle from the T4 upper endplate to the T12 lower endplate; lumbar lordosis (LL): the Cobb angle from the L1 upper endplate to the S1 upper endplate; T1 pelvic angle (TPA): the angle between a line joining the center of T1 and the femoral head axis and a line from the center of the femoral head axis to the midpoint of the S1 upper endplate; sagittal vertical axis (SVA): the distance between the C7 plumb line and the posterosuperior corner of S1; osteotomized vertical angle (OVA): the angle between the lower endplate of the osteotomized vertebra and the upper endplate of the cranial adjacent vertebra; pelvic incidence (PI) : the angle between the line perpendicular to the S1 upper endplate and the line from the center of the S1 upper endplate to the center of the femoral head axis; pelvic tilt (PT): the angle between the vertical line and the line from the center of the S1 upper endplate to the center of the femoral head axis; sacral slope (SS): the angle between the S1 upper endplate and the horizontal line; PI and LL mismatch (PI-LL): the pelvic incidence value minus the lumbar lordosis value.