Abstract

A computational head-neck model was developed to better understand the influence of head motion and cervical spine buckling on dynamic responses to near-vertex head impact. The model consisted of rigid vertebrae interconnected by assemblies of nonlinear springs and dashpots, and a finite element shell model of the skull. Model parameters were based upon quasi-static pure moment testing of cadaveric cervical spine motion segments and existing data reported in the literature. Geometric and inertial characteristics were derived from three-dimensional reconstructions of skull and vertebral CT images. The model correctly reproduced the complex cervical spine buckling deformations observed in high speed video of near-vertex impacts to cadaveric head-neck specimens, including a buckle at 6 msec and subsequent local post-buckled regions of both flexion and extension. Head and neck load histories agreed with those reported in the cadaveric studies. Sensitivity analyses of the cervical spine modeling parameters revealed that head and neck responses were most sensitive to changes in flexion-extension properties, consistent with structural stability theory for a slender column buckling under compressive loads. A sensitivity analysis of head mass demonstrated that even in the absence of a pocketing impact surface, the head inertia can oppose translational motion of the upper cervical spine during impact, resulting in increased neck loads.

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