In the pursuit of the mechanism of minor neck injuries, the motion of the cervical vertebrae was analyzed under different conditions such as the seating position and seat performance characteristics. At first, a new impact sled was developed which simulated actual car impact acceleration. This did not involve any risks for the subjects. Ten volunteers participated in the experiment under the supervision of the ethics committee. For test conditions we selected 2, 4, and 6 km/h speeds. Two types of seat performance were used: ordinary car seat and rigid wooden seat. The cineradiography (90 frames/second) recorded the motion of the cervical vertebrae at impact.
It was observed that a downward and rearward extension motion of the C3 compared to the C6 occurred and the cervical spine was compressed in early stage at impact. Moreover, it was found that when the seat was rigid and speeds were increased, the ramping up motion of the body of the subject and the neck compression were more typical. The vertebral motion was qualified and then compared with the differences between crash motion and normal motion. It is concluded here that the compression vertical motion plays an important role in minor neck injuries.