Figure 6.

Pre-operative radiological parameters in lordosis groups. Cervical spine lateral X-ray of neutral (A), flexion (B), and extension (C), and whole-spine lateral X-ray (D). C0-2; C0-2 Cobb angle, the occipito-cervical angle, which is the intersection angle between the McGregor line and the line parallel to the C2 lower endplate. C2-7; C2-7 Cobb angle, the intersection angle between the line perpendicular to the line parallel to the C2 lower endplate and the line perpendicular to the line parallel to the C7 lower endplate. C0-7; C0-7 Cobb angle, the intersection angle between the McGregor line and the line parallel to the C7 lower endplate. TK; thoracic kyphosis, intersection angle between the line perpendicular to the line parallel to the T1 upper endplate and the line perpendicular to the line parallel to the T12 lower endplate. LL; lumbar lordosis, intersection angle between the line perpendicular to the line parallel to the L1 upper endplate and the line perpendicular to the line parallel to the L5 lower endplate. SS; sacral slope, the angle formed by a line drawn along the endplate of the sacrum and a horizontal reference line. PT; pelvic tilt, the angle formed by a line drawn from the midpoint of the sacral endplate to the center of the bicoxofemoral axis and a vertical and a vertical plumb line. PI; pelvic incidence, the angle formed by two vectors: the line joining the bicoxo-femoral axis to the center of the sacral end plate and the line perpendicular to the sacral endplate.