Spinal injuries in belt-wearing car occupants killed by head-on collisions.

In 34 post-mortem examinations of car occupants wearing seat belts and killed in straight or oblique head-on collisions, a thorough investigation of the spine was performed. The autopsy results were correlated with the findings in the cars in order to reconstruct the events when the occupant's body struck the interior of the car. In 2 cases the victims had worn lap belts, in 15 cases shoulder belts and in 17 cases combined shoulder-lap belts (three-point belts). In victims involved in head-on collisions while wearing lap belts, fractures of the neural arch of the axis were found which were probably due to flexion of the neck pivoting round the lower part of the impacting face and simultaneous stretching of the neck. Severe injuries to the cervical spine in those victims wearing shoulder belts were mainly due to the occupant sliding under the belt which then caught the neck and mandible. Such injuries were also caused by the impact of the head against forward parts of the car. In those wearing shoulder-lap belts injuries to the upper part of the cervical spine resulted from the impact of the head against internal parts of the car. When a slight impact of the head occurred minor injuries to the lower cervical spine were seen. Injuries to the thoracolumbar spine in the cases examined were the consequence of a violent extension between the upper part of the trunk held back by the shoulder belt and the pelvis restrained by the lap belt or by the knees striking the fascia panel. In front seat occupants this extension can be increased if either rear seat occupants without belts or heavy objects on the rear seat are projected forwards against their backs.