Radiographic measurements of the cervical spine: C2–C7 lordosis angle, C2–C7 sagittal vertical axis (C2–C7 SVA), C0–C7 lordosis angle, and T1 slope. The percentage of anterior resorption of vertebral body was obtained by ratio of the narrowest anteroposterior distance of scaffolding vertebra to the mean anteroposterior distance of the two adjacent cervical vertebral bodies.