Figure 2 Measurements of cervical sagittal radiographic parameters on lateral cervical radiographs. (A) The sagittal vertical axis (SVA) was measured as the horizontal distance from a vertical line drawn from the centroid of the C2 vertebral body to the posterosuperior corner of the C7 vertebral body, reflecting the anterior–posterior translation of the cervical spine. (B) The spino–cranial angle (SCA) was measured as the angle between a line connecting the center of the sella turcica to the center of C7 and a line along the posterior aspect of the cervical vertebral bodies, providing an index of the overall sagittal curvature relative to the cranial base. (C) Intervertebral disc height was measured as the average of the anterior and posterior disc heights at each cervical level from C2–C3 through C6–C7, with measurements taken at the midpoint of each vertebral segment.