A Biomechanical Evaluation of Skull–Brain Surrogates to Blunt High‐Rate Impacts to Postmortem Human Subjects

Abstract

The field of forensic injury biomechanics is an emerging field. Biomechanically validated tools may assist interdisciplinary teams of investigators in assessing mechanisms of blunt head trauma resulting in skull fractures. The objective of this study is to assess the biofidelity of spherical, frangible skull-brain (SB) surrogates. Blunt impacts were conducted at 20 m/s, using an instrumented 103 g rigid impactor, to the temporo-parietal region of four defleshed cephalic postmortem human subjects (PMHS). Force-deformation response, fracture tolerance, and fracture patterns were recorded for comparison to spherical skull-brain surrogates. Three brain substitutes were assessed: 10% gelatin, lead shot with Styrofoam and water. Force-deformation response of the skull-brain surrogates was similar to defleshed PMHS up to the point of fracture; however, none of the surrogates fractured at tolerance levels comparable to the PMHS. Fracture patterns of the skull-brain surrogates were linear and radiating, while PMHS fractures were all depressed, comminuted.

Does preliminary optimisation of an anatomically correct skull-brain model using simple simulants produce clinically realistic ballistic injury fracture patterns?

“…Raymond and Bir [8] assessed a similar model against post mortem human specimens using blunt impacts (a 103-g rigid impactor at 20 m/s) but found the fracture patterns to be different in the human bone compared to the polyurethane spheres.…”

A Review of the Compressive Stiffness of the Human Head

“…In most studies, uniaxial deformation was measured using a displacement sensor (linear variable differential transformer, string potentiometer, or laser distance sensor) fixed to the loading apparatus. For free-falling and unconstrained projectile methods, deformation was determined by double integration of an acceleration-time signal, which was recorded with an accelerometer fixed to the head or impactor, 4 , 6 , 37 , 41 or calculated by normalizing the force–time signal with the head mass. 20 , 22 …”

“…Four studies evaluated the stiffness of adult cadaveric and ATD heads in the same apparatus. 1 , 4 , 6 , 22 One study compared the stiffness of a custom surrogate head model and cadaveric heads, 37 but this study was not included in this review as the heads were impacted by a small, high velocity, ballistic.…”

“…Synthetic surrogate head models, such as anthropomorphic test devices (ATD; e.g. Hybrid III, FOCUS and NOCSAE) or custom head models, 11 , 37 , 38 are used in experimental models of head and head-neck injury events to assess the risk of skull, brain and/or cervical spine injury. 30 , 38 , 43 To enable accurate prediction of injury, these head models should possess an impact response that lies within cadaveric response corridors (mean ± standard deviation) for the relevant test configuration.…”

The use of gelatine in wound ballistics research

“…A number of polymeric bone simulants exist and have been used to represent skulls, e.g. [ 19 , 38 – 40 ], and other bones [ 41 – 43 ]; these may be anatomically accurate or a simple geometric representation.…”