Balasubramanian, page 1 HEAD AND SPINAL TRAJECTORIES IN CHILDREN AND ADULTS EXPOSED TO LOW SPEED FRONTAL ACCELERATION

Head injuries are the most common injuries sustained by children in motor vehicle crashes. Prevention of these injuries through advances in vehicles and restraint systems requires a biofidelic anthropomorphic test device (ATD). Pediatric ATDs are primarily developed from scaling down adult volunteer and cadaver impact test data. Limited experimental data exist on pediatric head and neck kinematics in order to evaluate the biofidelity of the ATDs. The aim of the current study was to evaluate the head and spinal kinematics of pediatric and adult volunteers in response to a dynamic low-speed frontal sled test. Low speed volunteer testing of five male subjects in each of two specific age groups (912, and 18-30 years) were performed using a pneumatically actuated – hydraulically controlled sled. Safe limits were established from measurement of bumper car accelerations at an amusement park ride (4.9 g, 55.7 msec rise time, 110 msec duration), which we believed to be sub-injurious to the adult and child amusement park population. We subsequently recreated the bumper car environment in the laboratory, by developing a low-speed hydropneumatic sled. As an added measure of safety, our average maximum cart acceleration was 3.59 g for children and 3.78 g for adults, thus producing occupant loads that are approximately 25% less than the bumper car amusement park ride. Spherical reflective markers were placed on the head, neck, torso, upper and lower extremities and tracked using a 3D motion analysis system. An angular rate sensor was mounted to a bite plate of an athletic mouth guard to measure the head rotational velocity. Electromyography sensors were attached to key muscle groups to measure the muscle response of the subjects to the loading environment. Each subject was subjected to six sled runs. Head and neck trajectories were compared between the adult and pediatric subjects. In addition, the effect of habituation on kinematic response was examined by comparing within subject changes in kinematics throughout the series of six sled runs.