Kinetics of the cervical spine in pediatric and adult volunteers during low speed frontal impacts

Abstract: Previous research has quantified differences in head and spinal kinematics between children and adults restrained in an automotive-like configuration subjected to low speed dynamic loading. The forces and moments that the cervical spine imposes on the head contribute directly to these age-based kinematic variations. To provide further explanation of the kinematic results, this study compared the upper neck kinetics – including the relative contribution of shear and tension as well as flexion moment – between children (n=20, 6–14yr) and adults (n=10, 18–30yr) during low-speed (<4g, 2.5m/s) frontal sled tests. The subjects were restrained by a lap and shoulder belt and photo-reflective targets were attached to skeletal landmarks on the head, spine, shoulders, sternum, and legs. A 3D infrared tracking system quantified the position of the targets. Shear force (F x ), axial force (F z ), bending moment (M y ), and head angular acceleration () were computed using inverse dynamics. The method was validated against ATD measured loads. Peak F z and significantly decreased with increasing age while M y significantly increased with increasing age. F x significantly increased with age when age was considered as a univariate variable; however when variations in head-to-neck girth ratio and change in velocity were accounted for, this difference as a function of age was not significant. These results provide insight into the relationship between age-based differences in head kinematics and the kinetics of the cervical spine. Such information is valuable for pediatric cervical spine models and when scaling adult-based upper cervical spine tolerance and injury metrics to children. [Copyright &y& Elsevier]