Finite element simulation of head impacts in mixed martial arts

This study determined brain stress and strain in an unhelmeted sport and correlated this with concussive injuries. Thirteen MMA athletes were fitted with the MiG2.0 Stanford instrumented mouthguard. The mouthguard records linear acceleration and angular velocity in 6 degrees of freedom. Angular acceleration was calculated by differentiation. All events were video recorded, time stamped and reported impacts confirmed. 298 impacts above 10g were recorded during sparring sessions and 153 impacts in competitive events. The competitive events resulted in five concussions which were diagnosed by a medical doctor. The impact with the highest angular acceleration from each sparring session and competitive event was simulated using the GHBMC head and neck model. The model was run on Amazon Web Services using the LS-Dyna explicit solver. The resultant linear acceleration, strain in the corpus callosum and brain stem and shear stress in the corpus callosum were all significantly different in concussed athletes compared to uninjured. Average strain in the corpus callosum of concussed fighters was 0.27 which was 87.9% higher than uninjured fighters and was the best strain indicator of concussion. The best overall predictor of concussion found in this study was shear stress in the corpus callosum which differed by 111.4% between concussed and uninjured athletes. This study is unique in that it measured head accelerations in vivo and determined that high stress and strain in the corpus callosum correlated with the concussive injuries.