Age-related changes in upper and lower cervical alignment and range of motion: normative data of 600 asymptomatic individuals

To identify age-related changes and the relationship between upper and lower cervical sagittal alignment and the range of motion (ROM). A total of 600 asymptomatic volunteers were enrolled. There were 50 males and 50 females in each decade of life between the third and the eighth. The O–C2 angle and the C2–7 angle were measured using the neutral radiographs of the cervical spine. ROM was assessed by measuring the difference in alignment in the neutral, flexion, and extension positions. The mean O–C2 angle in the neutral position was 14.0° lordotic. The mean ROM of the O–C2 angle was 23.1°. The mean C2–7 angle in the neutral position was 14.3° lordotic. The mean ROM of the C2–7 angle was 56.0°. The O–C2 angle was 16.1° in the third decade and gradually decreased to 11.4° in the eighth decade. There were no significant age-related changes in the ROM of the O–C2 angle. The C2–7 angle was 7.2° in the third decade and gradually increased to 20.8° in the eighth decade, and the ROM gradually decreased with increasing age. Significant negative correlation was observed between O–C2 angle and C2–7 angle. The O–C2 angle gradually decreased and the C2–7 angle increased with age. The ROM of the O–C2 angle did not change, but the ROM of the C2–7 angle decreased with age. The upper and lower cervical spine showed different age-related changes.