Are the standard parameters of cervical spine alignment and range of motion related to age, sex, and cervical disc degeneration?

OBJECT The aims of this study were 1) to establish the standard parameters of alignment and total and segmental range of motion (ROM) of the cervical spine in the asymptomatic population, and 2) to identify factors that influence cervical ROM and alignment. METHODS The authors measured 636 standard cervical lateral, flexion, and extension plain radiographs of 212 asymptomatic volunteers. The relationship between cervical alignment and total ROM was assessed with simple linear regression. Multivariate linear regression was used to determine the effect of the influential factors on cervical alignment and total and segmental ROM. RESULTS The mean value for C2–7 cervical alignment was 21.40° ± 12.15°, and the mean value for total ROM was 63.59° ± 15.37°. Sex was a significant factor in cervical alignment, total ROM, and segmental ROM for C2–3 and C5–6 (p < 0.05). Age had a significant negative association with both the total ROM and all of the segmental ROM measurements (p < 0.05). Cervical disc degeneration at the level of interest had a significant negative association with C4–5, C5–6, and C6–7 ROM (p < 0.05). CONCLUSIONS Cervical alignment in female subjects was 2.47° lower than that in male subjects. Total ROM was 3.86° greater in female than in male subjects and decreased 6.46° for each decade of aging. Segmental ROM decreased 1.28° for each decade of aging and 2.26° for each category increase in disc degeneration at the level of interest.