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  • Author: Andrew S. McIntosh x
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Declan A. Patton, Andrew S. McIntosh and Svein Kleiven

Biomechanical studies of concussions have progressed from qualitative observations of head impacts to physical and numerical reconstructions, direct impact measurements, and finite element analyses. Supplementary to a previous study, which investigated maximum principal strain, the current study used a detailed finite element head model to simulate unhelmeted concussion and no-injury head impacts and evaluate the effectiveness of various tissue-level brain injury predictors: strain rate, product of strain and strain rate, cumulative strain damage measure, von Mises stress, and intracranial pressure. Von Mises stress was found to be the most effective predictor of concussion. It was also found that the thalamus and corpus callosum were brain regions with strong associations with concussion. Tentative tolerance limits for tissue-level predictors were proposed in an attempt to broaden the understanding of unhelmeted concussions. For the thalamus, tolerance limits were proposed for a 50% likelihood of concussion: 2.24 kPa, 24.0 s−1, and 2.49 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively. For the corpus callosum, tolerance limits were proposed for a 50% likelihood of concussion: 3.51 kPa, 25.1 s−1, and 2.76 s−1 for von Mises stress, strain rate, and the product of strain and strain rate, respectively.

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Declan A. Patton, Andrew S. McIntosh and Svein Kleiven

Concussion is an injury of specific interest in collision and contact sports, resulting in a need to develop effective preventive strategies. A detailed finite element model of the human head was used to approximate the regional distribution of tissue deformations in the brain by simulating reconstructions of unhelmeted concussion and no-injury head impacts. The results were evaluated using logistic regression analysis and it was found that angular kinematics, in the coronal plane, and maximum principal strains, in all regions of the brain, were significantly associated with concussion. The results suggested that impacts to the temporal region of the head cause coronal rotations, which render injurious strain levels in the brain. Tentative strain tolerance levels of 0.13, 0.15, and 0.26 in the thalamus, corpus callosum, and white matter, respectively, for a 50% likelihood of concussion were determined by logistic regression. The tentative strain tolerance levels compared well with previously reported results from reconstruction studies of American football and single axon, optic nerve, and brain slice culture model studies. The methods used in the current study provide an opportunity to collect unique kinematic data of sporting impacts to the unprotected head, which can be employed in various ways to broaden the understanding of concussion.

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Peter L. Davidson, Suzanne J. Wilson, David J. Chalmers, Barry D. Wilson, David Eager and Andrew S. McIntosh

The amount of energy dissipated away from or returned to a child falling onto a surface will influence fracture risk but is not considered in current standards for playground impact-attenuating surfaces. A two-mass rheological computer simulation was used to model energy flow within the wrist and surface during hand impact with playground surfaces, and the potential of this approach to provide insights into such impacts and predict injury risk examined. Acceleration data collected on-site from typical playground surfaces and previously obtained data from children performing an exercise involving freefalling with a fully extended arm provided input. The model identified differences in energy flow properties between playground surfaces and two potentially harmful surface characteristics: more energy was absorbed by (work done on) the wrist during both impact and rebound on rubber surfaces than on bark, and rubber surfaces started to rebound (return energy to the wrist) while the upper limb was still moving downward. Energy flow analysis thus provides information on playground surface characteristics and the impact process, and has the potential to identify fracture risks, inform the development of safer impact-attenuating surfaces, and contribute to development of new energy-based arm fracture injury criteria and tests for use in conjunction with current methods.