Fig. 1

Methods of measurements of spinopelvic parameters on the standard view (a, c) and the grayscale inversion view (b, d). Thoracic kyphosis was defined as the value of angle between the upper endplate of the T5 and the lower endplate of T12. Lumbar lordosis was defined as the value of angle between the superior endplate of L1 and the superior endplate of S1. Sagittal vertical axis was defined as the horizontal distance between the postero-superior corner of the sacrum and the C7 plumb line. Pelvic incidence was defined as the value of the angle between the line perpendicular to the superior plate of S1 at its midpoint and the line connecting this point to the center of the line connecting the centers of the femoral heads. Sacral slope was defined as the value of the angle between the superior plate of S1 and a horizontal line. Pelvic tilt was defined as the value of the angle between the vertical and the line connecting the midpoint of the sacral plate to the axis of the femoral heads