Abstract
Twentyβtwo women (age range 25β49 years, average 30.9 years) and twentyβtwo men (age range 23β42 years, average 31.6 years), all healthy and asymptomatic, underwent passive flexion/extension examinations of the cervical spine. Functional xβrays were taken and analyzed using a computerβassisted method that quantified intervertebral rotations, translations, and locations of the centers of rotation for each level C1βC2βC6βC7. The aim of the study was to establish values for these parameters for a normal population as related to age and gender. In the process, a statistically significant difference was found in the average value of rotation between male and female groups at the C5βC6 level. A new parameter, the ratio between translation and rotation, was also established and may prove useful for clinical diagnoses. This parameter has a smaller error associated with it than do pure translations and may aid the clinician by helping to account for the large variation in rotatory ranges of motion within the population. This translation/rotation ratio indicated highly significant differences in the lower segments of the cervical spine between gender groups.