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

PURPOSE: To identify age-related changes and the relationship between upper and lower cervical sagittal alignment and the range of motion (ROM). METHODS: 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. RESULTS: 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. CONCLUSION: 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.