Measures

Lateral cervical X-ray examination: the patients maintain horizontal gaze with their neck in the center. Measurement parameters include C2–7 Cobb angle, C2–7 sagittal vertical axial (SVA), thoracic 1 slope (T1S), thoracic 1 slope minus cervical lordosis (TS-CL), thoracic inlet angle (TIA), neck tilt (NT), and spine-cranial angle (SCA). The measurement method of cervical parameters is shown in Figs. ​Figs.1,1, ​,22 and ​and33 and Table ​Table2.2. All parameters were measured twice independently by two surgeons. The two measurements are averaged and recorded. Imaging data collection was divided into three stages: preoperative (on admission), postoperative, and follow-up (last outpatient visit).

Method for measuring C2-C7 lordosis, Spine-cranial angle

Method for measuring C2-7 SVA, C1-7 SVA and CG-C7 SVA

Method for measuring T1S, NT and TIA

measurement methods of each parameter

Gender, age, fusion segments, BMI, and symptom duration were collected through the hospital record system. NDI scores were collected at preoperative and the last follow-up. The patient voluntarily filled in the NDI scores scale, and the total score was calculated by researchers. The NDI score was used to evaluate neck function and surgical outcome