The effect of impact location on brain strain.

To determine the effect of impact direction on strains within the brain. Laboratory drop tests of hybrid III head-form and finite element simulation of impacts. A head-form instrumented with accelerometers and gyroscopes was dropped from 10 different heights in four orientations: front, rear, left and right-hand side. Twelve impacts with constant impact energy were chosen to simulate, to determine the effect of the impact location. A finite element head model was used to simulate these impacts, using 6 degrees of freedom. Following this, a further set of simulations were performed, where the same acceleration profiles were applied to different head locations. The angular accelerations recorded were up to 30% higher in lateral and rear impacts when compared to frontal impacts. High strains in the midbrain (41%) were recorded from severe frontal impacts where as high strains in the corpus callosum (44%) resulted from lateral impacts with the same energy. Impact direction is very significant in determining the subsequent strains developed in the brain. Lateral impacts result in the highest strains in the corpus callosum and frontal impacts result in high strains in the mid-brain.