ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

1. ABSTRACT
DYNAMIC PRESSURE RESPONSE IN HEAD INJURY
C. Pearce 1 , P.G. Young 2 , L. Cowlam 3 and B. Walker 3
The mechanics of head impact injury are investigated using the finite-element method.
Three computational models of the head were constructed; these range from low to high
bio-fidelity. The finite-element models were obtained from MRI image data, using a
technique adapted from the marching cubes approach which automates the generation of
meshes and allows for a number of different structures (e.g. skull, scalp, brain) to be
meshed simultaneously. The highly biofidelic head model was validated against
cadaveric impact data. A range of impact simulations were carried out using the finiteelement
models to validate an analytical representation of head impact based on full 3D
elasticity equations developed by one the authors. These analytical and numerical
models were used in parallel to explore the phenomenon of large transient pressure
amplification in the brain. This behaviour occurs during low duration low velocity
impacts. The implications of these high pressure transients are also discussed.
Besides its significance in the study of head injury biomechanics, this research
demonstrates that numerical models generated from 3D scan data can be used
effectively to represent physical processes. This is useful given the ethical issues and
confounding factors associated with cadaveric testing.
2. INTRODUCTION
Traumatic Brain Injury (TBI) has significant economic and personal impact. Roughly
1.7 million people sustain TBI per year in the US, and of these 52,000 die. In the US in
2000 it was estimated that the direct medical costs of TBI, and indirect costs through
loss of productivity, totaled $60 billon. [1]
TBI can be categorised as being either blunt or penetrating, depending on whether the
cranial vault remains intact or is breached. Contrary to injuries resulting from
penetrating impact, the trauma locations and mechanisms resulting from blunt impact
are not well understood and cannot be well predicted. [2]
The current research builds upon work by Young and Morfey. In their paper [3] a range
of parametric studies were performed on a 2-phase finite-element model of the human
head in order to explore the sensitivity of the brain’s pressure response to changes in
material, geometric and loading parameters. The model used was a simple fluid-filled
sphere representation of the head: an outer shell which was based on approximate
geometric values of the human skull (radius, thickness), containing a fluid sphere
representing the brain. Relevant linear elastic material properties were applied to these
structures. This simplified model was used to reduce the complexities of the system so
that critical parameters which have a large effect become more evident.
The finite-element mesh was in the form of a 30º wedge, which had symmetry
conditions applied such that it behaves as a full sphere. The exterior shell was composed
1
PhD student, School of Engineering, Mathematics and Physical Sciences, University of Exeter, UK,
contact: cwp201@exeter.ac.uk
2
Professor, School of Engineering, Mathematics and Physical Sciences, University of Exeter, UK
3
ARUP, Solihull, West Midlands, UK, contact: Liliana.Cowlam@arup.com and Brain.Walker@arup.com