Quantifying and Comparing the Intersegmental Kinematics of the Pediatric Whole Cervical Spine to Individual Motion Segment Kinematics in a Six-Year-Old Postmortem Human Surrogate

<div>Mitigating both neck and head injuries in the pediatric population relies heavily on improving our understanding of the underlying biomechanics of the pediatric cervical spine. The tensile response for individual motion segments and the whole cervical spine (WCS) has been reported, but there is no data characterizing the intersegmental kinematics of pediatric WCS under axial loading conditions. The structural response of motion segments and WCS provide valuable data for the design and validation of biofidelic physical and computational models for the pediatric population. However, the use of motion segment data to construct WCS response or the use of WCS axial response to accurately characterize intersegmental response may present limitations to accurately modeling the pediatric cervical spine response. In this secondary analysis of the work of Luck et al. (<span>2008</span>, <span>2013</span>), the fixed-fixed, low load, quasi-static tensile response of the WCS and individual motion segments (O-C2, C4-C5, and C6-C7) of a six-year-old postmortem human surrogate (PMHS) was investigated to quantify and compare the intersegmental kinematics under both conditions. In the whole spine, O-C2, C3-C4, C6-C7, and C7-T1 exhibited a tensile response, C2-C3 and C5-C6 exhibited a compressive response, and C4-C5 did not exhibit an appreciable response in the axial loading direction. Furthermore, when compared to the tensile behavior of the individual motion segment load-controlled tests, C6-C7 exhibited reduced axial displacement and an increased stiffness at higher loads (≥13.5 N), suggesting the recruitment of more superficial ligamentous layers that span multiple vertebrae in the whole spine. Regarding vertical displacement and rotation, O-C2 exhibited the largest amount of rotation of 5.57 degrees in flexion and all segments exhibited some amount of anterior–posterior (AP) displacement. The intersegmental kinematics provide biomechanical response data that may support both physical and computational surrogate design and validation as well as data for comparison to isolated FSU testing conditions.</div>