Fig. 1.

Parameters measured before (A) and after surgery (B). The slope angle was measured with a horizontal line and a specific reference line at each cervical level : McGregor line (occipital slope), lower endplate of C2 body (C2 slope), lower endplate of C7 body (C7 slope), upper endplate of T1 body (T1 slope), upper segmental slope (USS), lower segmental slope (LSS). C2-7SVA (distance between the C2 plumb line and the superior posterior corner of C7 body), cranio-vertebral angle (CVA; the angle between the connecting line from the EAC to the distal tip of the spinous process of C7 and the horizontal line.