Characteristics of dynamic cervical vertebral kinematics for female and male volunteers in low-speed rear impact, based on quasi-static neck kinematics

The purpose of this study is to clarify the dynamic characteristics of inertia-induced cervical vertebral kinematics for both female and male volunteers in low-speed rear impact conditions by comparing quasi-static muscle-induced neck kinematics. Two series of volunteer tests were used. One is data from a rear impact sled test series with 2 females and 4 males. The second set of data is from a voluntary neck bending test series with 4 females and 9 males. Cervical vertebral motions were measured by a cineradiography system. The same volunteers in the first test series also participated in the second test series. C4/C5 through C6/C7 showed larger extension angle in the peak S shape than maximum voluntary retraction for females. In contrast, the peak S shape was in the maximum voluntary retraction for males. The rearward displacements at C6/C7 in the peak S shape exceeded the maximum voluntary extension for females. The vertebral angular displacement at C5/C6 was greatest in the peak extension and exceeded the voluntary extension, especially for females. The vertebral normalised displacements in X-direction at C5/C6 and C6/C7 showed larger rearward displacements in the peak extension than the voluntary extension, and exceeded the maximum voluntary extension for both genders.