Anatomical head model to measure impact force transfer through the head layers and their displacement

When the human head is subjected to blunt force impact, there are several mechanical responses that may result from the forces involved, including absorption of impact forces through the various layers of the head. The purpose of this study was to develop an anatomical head model to measure force transfer through the various head layers and their displacement when subject to short-duration high-velocity impacts. An anatomical head model was constructed using previously validated simulant materials: epoxy resin (skull), polyvinyl siloxane (scalp), agar/glycerol/water (brain) and modified intravenous fluid for the cerebrospinal fluid. An array of accelerometers (4 mm × 4 mm × 1.45 mm) was incorporated into the various layers of the head to measure forces in x- (anterior/posterior), y- (left/right) and z- (up/down) axis. All sensors were connected to a signal conditioning board and USB powered data loggers. The head model was placed into a rigid metal stand with an optical sensor to trigger data capturing. A weight (750 g) was dropped from a height of 0.5 m (n= 20). Impact forces (z-axis) of 1107.05 N were recorded on top of the skin, with decreasing values through the different layers (bottom of skin 78.48 N, top of skull 319.82 N, bottom of skull 87.30 N, top and centre of brain 47.09 N and base of brain 78.41 N. Forces in the x- and y-axes were similar to those of the z-axis. With the base of the brain still receiving 78.41 N, this highlights the potential danger of repetitive impact forces to the head. Upon impact the layers of the head are displaced in the x-, y- and z-direction, with the highest values shown in the z-axis. In conclusion, this study identified the importance of considering short-duration high-intensity impacts to the head and their effect on underlying tissues. </jats:p

An Investigation on the Correlation between the Mechanical Properties of Human Skull Bone, Its Geometry, Microarchitectural Properties, and Water Content

With increasingly detailed imaging and mechanical analysis, modalities need arises to update methodology and assessment criteria for skull bone analysis to understand how bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The main aim was to analyze the effect of macroscopic and microstructural features, as well as periosteal attachment, on the mechanical properties of human skull bone. Fifty-six skull specimens from ethanol-phenoxyethanol-embalmed cadavers were prepared from two human cadavers. Assuming symmetry of the skull, all samples from one-half each were stripped of periosteum and dura mater, while the soft tissues were kept intact on the remaining samples on the contralateral side. The specimens were analyzed using microcomputed tomography to assess trabecular connectivity density, total surface area, and volume ratio. The specimens were loaded under three-point bend tests until fracture with optical co-registration. The bone fragments were then lyophilized to measure their water content. With increasingly detailed imaging and mechanical analysis modalities, there is a need to update methodology and assessment criteria for skull bone analysis to understand how the bone microarchitecture and the presence of attached tissues may affect the response to mechanical load. The mechanical properties were negatively correlated to bone thickness and water content. Conversely, most microarchitectural features did not influence either mechanical parameter. The correlation between mechanical response data and morphologic properties remains similar between the results of embalmed tissues presented here and fresh osseous tissue from literature data. The findings presented here add to the existing methodology to assess human skull for research purposes. The interaction between most microarchitectural features in ethanol-phenoxyethanol-embalmed embalmed skull samples and bending stress appear to be minute.</jats:p