Surface friction in near-vertex head and neck impact increases risk of injury

A computational head-neck model was developed to test the hypothesis that i ncreases in friction between the head and impact surface will increase head and neck injury risk during near-axial impact. The model consisted of rigi d vertebrae interconnected by assemblies of nonlinear springs and dashpots, and a finite element shell model of the skull. For frictionless impact sur faces, the model reproduced the kinematics and kinetics observed in near-ax ial impacts to cadaveric head-neck specimens. Increases in the coefficient of friction between the head and impact surface over a range from 0.0 to 1. 0 resulted in increases of up to 40, 113, 9.8, and 43% in peak post-buckled resultant neck forces, peak moment at the occiput-C1 joint, peak resultant head accelerations, and HIC values, respectively. The most dramatic increa ses in injury-predicting quantities occurred for COF increases from 0.0 to 0.2, while further COF increases above 0.5 generally produced only nominal changes. These data suggest that safety equipment and impact environments w hich minimize the friction between the head and impact surface may reduce t he risk of head and neck injury in near-vertex head impact. (C) 1999 Elsevi er Science Ltd. All rights reserved.