The Effect of Head-Forward Posture on Risk of Lower Neck Dislocation During Head-First Impacts: A Computational Investigation

Subaxial cervical facet dislocation (CFD) is a severe neck injury associated with head-first impacts (HFI), yet the effect of pre-impact head-forward posture (HFP) on injury risk remains unclear. This study examined how HFP influences cervical spine kinematics, kinetics, and CFD risk during HFI. A modified Global Human Body Models Consortium (GHBMC) detailed head-neck finite element model simulated inverted drop tests (2 m/s) with varying pre-impact HFP (0–50 mm). The simulations reproduced the characteristic "S-shaped" neck deformation observed in prior experiments, with increasing eccentricity progressively elevating lower cervical spine anterior shear forces beyond physiological thresholds for eccentricities above 15 mm. Although limitations in intervertebral soft-tissue failure criteria prevented CFD occurrence in simulations, the results informed a cadaveric head-neck component inverted drop experiment (30 mm pre-HFI eccentricity) that resulted in complete C7/T1 dislocation. These findings indicate that pre-HFI head eccentricity affects cervical spine mechanics, increasing CFD risk by amplifying intervertebral shear forces. The study suggests that maintaining a neutral head posture in HFI scenarios may mitigate neck injury, and highlights the benefits of integrating computational and experimental models to enhance understanding of injury mechanisms and inform prevention strategies.