Brain Injury and Impact Characteristics

Almost all studies of traumatic brain injuries have only focused on the maximum acceleration associated with the impact. However, it has been noted that other impact characteristics should also be considered. This study has examined the effect on brain deformation [maximum principal strain (MPS)] associated with changing three characteristics of an isosceles trapezoid acceleration profile: initial slope (jerk), maximum acceleration, and impact energy (maximum velocity squared). This involved using a preexisting finite element model of the brain and applying the trapezoidal acceleration impact to the center of the forehead. The results showed the largest values of MPS were found along a line between the coup and contrecoup positions, and that a strong direct relationship existed between maximum acceleration and brain deformation as measured using MPS. In addition, a strong direct relationship was found to exist between impact energy and brain deformation as measured using MPS. However, it was found that there was almost no observable change in MPS with respect to different jerk values, and in fact there was a slight decrease in MPS as jerk values increased. This comported with a shock spectrum analysis of a simple one dimensional multiple degree of freedom system exposed to similar trapezoidal impulses.