Orientation-Dependent Neuronal Degradation Resulting from Axonal Stain Experienced in Football-Realistic Acceleration

Traumatic brain injury (TBI) is a common occurrence that results in neuronal death with hazardous long-term effects. Modeling TBI computationally is necessary in order to gain a better understanding of mechanical effects on neurobiological injury cascades and injury thresholds. A model of a single axon was submitted to accelerations observed in the sport of American Football to test for axonal membrane strains necessary to induce an apoptosis pathway. A neuronal membrane strain of 0.20 [1] has been found to cause a Ca2+ influx necessary to initiate a neuronal degradation pathway. The proposed model sought to identify if accelerations in American Football could cause such detrimental strains. To test this, forces were applied in three directions: parallel to the axon, normal to the axon, and rotational about the axon to account for the multiple orientations forces can act upon to cause neuronal strain. Results from the different orientations with varying force magnitudes made it clear that stresses applied rotationally are the most detrimental and can cause a strain of 0.200 at an acceleration as low as 45g. Accelerations of 45g or greater are found in approximately 10% of the impacts observed in college football [2]. The resulting data from this model can be extrapolated to a larger scale to benefit the design of better head protection to include protection from shear forces.