Traumatic brain injuries (TBIs) remain a large public health concern, with an estimated 2.8 million people in the United States alone sustaining a TBI annually, of whom 56,000 die. Despite the development of finite element (FE) models of the head, the implications of skull deflection on the risk of brain injury in blunt trauma is not well understood. There is currently a lack of injury metrics which quantify skull deflection;​ therefore, the objective of this study was to replicate experimental head impacts using the head from the Global Human Body Models Consortium 50th percentile male occupant model (GHBMC M50 -O v4.5), develop a skull deflection injury metric, and evaluate the relationship between the skull deflection and tissue -based brain strain.

Three experimental test series were replicated using simulation techniques (Allsop, 1991;​ Cormier, 2011;​ Yoganandan, 1995). During each simulation, every brain element’s strain tensors were output at 0.1 ms intervals. Similarly, the inner skull surface nodal displacements with respect to the head center of gravity were output at 0.1 ms intervals.

The brain elements were then grouped based on proximity to the impact site to define coup and contre -coup regions of interest (ROIs). A maximum skull deflection metric was developed for skull deflection characterization. Correlations between the skull deflection injury metric a nd coup ROI elemental strain measures were evaluated. Differences in the distribution of coup and contre -coup strain within single impacts were evaluated.

Nine experimental tests were simulated in this study. Input kinetic energy, impactor geometry, bounda ry conditions, and impact location from the respective experimental test were replicated in each simulation. Skull deflection ranged from 1.24-4.98 mm. 95th percentile coup and contre-coup maximum principal strains ranged from 0.02-0.08 and 0.008-0.048, respectively. Coup strain was positively correlated to the skull deformation metric. There were statistically significant differences between coup and contre -coup 95th percentile maximum principal strain.

Replicating cadaveric testing of heads allows for more in depth analysis into brain injury metrics that are unable to be studied from PMHS alone. Specifically, shape profiles of inner skull deformation were able to be characterized and compared to brain tissue response. A positive linear relationship was fou nd between the skull deformation metrics and underlying brain strain, which is the likely source for focal brain injury. Thus, the skull deformation metric developed in this study will lead to a better understanding of the mechanistic relationship between skull deformation and head injury.