Study of mild traumatic brain injuries using experiments and finite element modeling.

The objective of the study was to better understand the biomechanics of mild traumatic brain injuries (TBI) using a hybrid approach: experiments and computational modeling. A three-dimensional finite element model of the rat skull and brain was used to understand the anatomical region-dependent stress response under mild TBI conditions. Anesthetized rats were exposed to varying coronal plane angular acceleration pulses without direct head contact. Experimental outcomes included unconscious time and histological evidence of brain pathology using GFAP and MAP2. The finite element model was exercised using the five experimental and four supplemental pulses to simulate nine independent combinations of peak acceleration and pulse duration (290 to 542 krad/s(2) and 1 to 3 ms). Stress response metrics were correlated to histological and behavioral (e.g., loss of consciousness) evidence of injury in rats subjected to pure coronal plane angular acceleration of the head. Injury severity was modulated by independently controlling peak magnitude and duration of the angular acceleration. While peak Von Mises stresses correlated well with changes in injury severity associated with peak angular acceleration, this metric did not demonstrate sensitivity to changes in acceleration duration. However, an integrated stress-time metric was able to predict changes in injury severity associated with increasing angular acceleration magnitude and duration in both the hippocampal and parietal cortex anatomical regions. Results of this unique hybrid analysis indicate that the combined stress-time variable may be more suited to explain variation of mild TBI severity, rather than pure peak metrics.