Dynamic cervical vertebral motion of female and male volunteers and analysis of its interaction with head/neck/torso behavior during low-speed rear impact

The purpose of this study was to clarify the characteristics of dynamic head/neck/torso and cervical vertebral motion for females and males in a rear impact by reanalyzing two series of rear impact sled tests. One was a test series with 12 males and 8 females, the latter not previously published. Whole body visual motion was measured by a high speed video camera. The second series was conducted with 4 males and 2 females. Cervical vertebral motion was measured by cineradiography, as well as visual motion through a highspeed video camera. The general characteristics of female visual motions were derived from the two test series. Cervical vertebral motion was then investigated. The females had a peak flexion of the head relative to neck link, defined as a line between T1 and the occipital condyle, while the neck link was extension at the time of peak head flexion. On the other hand, the males had flexion in both the head relative to neck link and neck link relative to T1 up to 100ms. Likewise, the females had larger flexion in the upper vertebral segments and larger extension in lower vertebral segments, when analysing the cervical spine motion. The cineradiography data showed the same tendency as that of the overall neck motion and supported that the head relative to neck link and neck link relative to T1 indicated S-shape deformation of the neck.