Pressure and shear responses in brain injury models

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Bradshaw, D. R. S.^1,2; Morfey, C. L.¹

Pressure and shear responses in brain injury models

Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles (ESV)

Affiliations

¹ISVR, University of Southampton, UK

²First Technology, USA
Abstract

Finite element (FE) models of the brain are regularly used to investigate brain injury mechanisms. Validation of these models against cadaver impacts is usually restricted to intracranial pressure data. However, the low shear modulus of neural tissue means that injurious strains result from shear deformations. We show that brain injury models that are validated for pressure alone can give a wide range of shear responses to the same impact.

Holbourn’s arguments on the harmlessness of pressure are extended by introducing separate wave equations for pressure and shear, derived from the Helmholtz vector decomposition. Two idealised models of traumatic brain injury are used to show that there is no one-to-one relation between pressure and shear in head impacts lasting a few milliseconds. The first is an analytical model of wave propagation in the brain under the action of local skull bending. The second is a strain-validated FE representation of the coronal plane of the human head under rotational acceleration.

As there is no one-to-one relation between dilatation and distortion in typical head impacts, it is not acceptable to validate FE models for pressure and then use them to predict injury.
Links

URL: http://www-nrd.nhtsa.dot.gov/pdf/nrd-01/Esv/esv17/Proceed/00197.pdf

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Cited By (18)

Year	Entry
2013	Sahoo D, Deck C, Willinger R. Medical imaging data implementation into human FE head modelling and validation. In: Proceedings of the 2013 International IRCOBI Conference on the Biomechanics of Injury. September 11-13, 2013; Gothenburg, Sweden.563-575.
2014	Ren L, Baumgartner D, Davidsson J, Yang J, Willinger R. Effect of the inhomogeneous brain mechanical characteristic on dynamic responses of head under trauma. In: Proceedings of the 2014 International IRCOBI Conference on the Biomechanics of Injury. September 10-12, 2014; Berlin, Germany.93-105.
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2002	Ivarsson J. Physical Modeling of Brain and Head Kinematics [PhD thesis]. Göteburg, Sweden: Chalmers University of Technology; 2002.
2018	Tierney G. A Biomechanical Assessment of Direct and Inertial Head Loading in Rugby Union [PhD thesis]. Dublin, Ireland: Trinity College Dublin; 2018.
2014	Patton DA. The Biomechanical Determinants of Sports-Related Concussion: Finite Element Simulations of Unhelmeted Head Impacts to Evaluate Kinematic and Tissue-Level Predictors of Injury and Investigate the Design Implications for Soft-Shell Headgear [PhD thesis]. University of New South Wales; March 2014.
2013	Post A. The Influence of Dynamic Response Characteristics on Traumatic Brain Injury [PhD thesis]. Ottawa, ON: University of Ottawa; 2013.
2014	Rousseau P. Analysis of Concussion Metrics of Real-World Concussive and Non-Injurious Elbow and Shoulder to Head Collisions in Ice Hockey [PhD thesis]. Ottawa, ON: University of Ottawa; 2014.
2016	Kendall M. Comparison and Characterization of Different Concussive Brain Injury Events [PhD thesis]. University of Ottawa; 2016.
2019	Cournoyer J. Head Impact Severity Associated With Loss of Consciousness and Impact Seizures in Sport-Related Concussions [PhD thesis]. Ottawa, ON: University of Ottawa; 2019.
2022	Murphy A. Comparing Equestrian Helmets With and Without Rotational Technology Using an Equestrian Concussive Specific Helmet Test Protocol [Master's thesis]. University of Ottawa; 2022.
2023	Lyu D. Investigation of Biomechanical Thresholds of Mild to Severe Brain Injury Using an Anisotropic Visco-Hyperelastic Finite Element Head Model: Model Development and Simulation of Impact Injury and Blast Injury [PhD thesis]. Detroit, MI: Wayne State University; August 2023.