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. 2024 Jun 25;11(7):650.
doi: 10.3390/bioengineering11070650.

Anatomical Features and Material Properties of Human Surrogate Head Models Affect Spatial and Temporal Brain Motion under Blunt Impact

Michael Hanna  1 , Abdus Ali  1 , Prasad Bhatambarekar  1 , Karan Modi  1 , Changhee Lee  2 , Barclay Morrison 3rd  2 , Michael Klienberger  3 , Bryan J Pfister  1
Affiliations

Anatomical Features and Material Properties of Human Surrogate Head Models Affect Spatial and Temporal Brain Motion under Blunt Impact

Michael Hanna et al. Bioengineering (Basel). .

Abstract

Traumatic brain injury (TBI) is a biomechanical problem where the initiating event is dynamic loading (blunt, inertial, blast) to the head. To understand the relationship between the mechanical parameters of the injury and the deformation patterns in the brain, we have previously developed a surrogate head (SH) model capable of measuring spatial and temporal deformation in a surrogate brain under blunt impact. The objective of this work was to examine how material properties and anatomical features affect the motion of the brain and the development of injurious deformations. The SH head model was modified to study six variables independently under blunt impact: surrogate brain stiffness, surrogate skull stiffness, inclusion of cerebrospinal fluid (CSF), head/skull size, inclusion of vasculature, and neck stiffness. Each experimental SH was either crown or frontally impacted at 1.3 m/s (3 mph) using a drop tower system. Surrogate brain material, the Hybrid III neck stiffness, and skull stiffness were measured and compared to published properties. Results show that the most significant variables affecting changes in brain deformation are skull stiffness, inclusion of CSF and surrogate brain stiffness. Interestingly, neck stiffness and SH size significantly affected the strain rate only suggesting these parameters are less important in blunt trauma. While the inclusion of vasculature locally created strain concentrations at the interface of the artery and brain, overall deformation was reduced.

Keywords: TBI; brain motion; human head surrogate; injury thresholds.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Images of the experimental setup. Exp.SBM shows the PVC skull in crown impact used to study the effect of the surrogate brain material. Exp.SSS-a shows the unstiffened ABS skull in crown impact used to study the effect of surrogate skull stiffness. Exp.SSS-b shows the stiffened ABS skull in crown impact used to study the effect of surrogate skull stiffness. Exp.CSF-a shows the VeroClear skull in frontal impact with CSF used to study the effect of CSF. Exp.CSF-b shows the VeroClear skull in frontal impact without CSF used to study the effect of CSF. Exp.SHS-a shows the 10th percentile ABS skull in frontal impact used to study the effect of SH size. Exp.SHS-b shows the 90th percentile ABS skull in frontal impact used to study the effect of SH size. Exp.VASC-a shows the VeroClear skull in frontal impact without vasculature used to study the effect of vasculature. Exp.VASC-b shows the VeroClear skull in frontal impact with vasculature used to study the effect of vasculature. Exp.VASC-b shows the VeroClear skull in frontal impact with vasculature used to study the effect of vasculature. Exp.NS shows the ABS skull in frontal impact to study the effect of neck stiffness.
Figure 2
Figure 2
(A) Unstiffened half surrogate skull (B) Stiffened surrogate skull (C) Full surrogate skull.
Figure 3
Figure 3
Hybrid III neck calibration. (A) Dial indicator being used to measure Hybrid III neck compression. (B) weights being mounted on the Hybrid III neck to measure stiffness. (C) Hybrid III neck deformation is being measured using a protractor.
Figure 4
Figure 4
(A) Measured shear modulus of ballistics gel compared with human brain. (B) Maximum shear strain heat map of 5% ballistics gel surrogate head. (C) Maximum shear strain heat map of 20% ballistics gel surrogate head.
Figure 5
Figure 5
(A) Bar graph of maximum strain gage measurements in the front, crown, and rear positions for stiffened, unstiffened, and full surrogate head. (B) Strain time course of the crown strain gage for stiffened, unstiffened, and full surrogate head.
Figure 6
Figure 6
(A) Heat map of maximum shear strain for stiffened surrogate skull head (B) Heatmap of Maximum Shear Strain for unstiffened surrogate skull head (C) Heat map of shear strain fold increase between unstiffened and stiffened surrogate skull head.
Figure 7
Figure 7
(A) Maximum shear strain heat map of SH without CSF. (B) Maximum shear strain heat map of SH with CSF. (C) Average surrogate brain shear strain over time of SH with CSF versus SH without CSF.
Figure 8
Figure 8
(A) Heat map of the shear strain rate for the 10th percentile surrogate head. (B) Heat map of the shear strain rate for the 90th percentile surrogate head. (C) Average surrogate brain shear strain over time of the 10th and 90th percentile surrogate head.
Figure 9
Figure 9
Heat map of the strain concentration factor of the surrogate head with vasculature compared with the surrogate head without vasculature.
Figure 10
Figure 10
(A) Heat map of strain rate in high stiffness neck SH. (B) Heat map of strain rate in low stiffness neck SH. (C) Average surrogate brain shear strain over time of surrogate head with low, medium and high stiffness neck.
See this image and copyright information in PMC

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