Finite Element Analysis of the Injury Biomechanics of Soccer TBI

The game of soccer is a sport that that is enjoyed worldwide by an estimated 265 million participants of all ages. Several types of injuries pose a risk for these athletes, with head injuries being the most common. Twenty two percent of all soccer injuries are diagnosed as a concussion. Head impacts during a soccer game are commonplace, due, in large part to the athletes repeatedly heading the ball. This technique is used often throughout the duration of a game, raising concerns that head impact exposure may have cumulative sub acute and acute adverse sequelae. Soccer ball heading has been shown to produce varying effects on an athlete’s cognitive function, yet an in-depth mechanistic representation of head exposure has not been fully demonstrated.

This study advances the biomechanical understanding of injury risks associated with soccer ball heading using in silico finite element (FE) models of human head-soccer ball impacts. Three input variables were considered for the FE simulations, ball velocity, location of impact and the active or passive head and neck conditions, that influence the motion of the head and neck during impact. The active and passive neck conditions were considered in the experimental design to simulate the athlete anticipating or not, contact with the incoming ball. In these FE models, the soccer ball’s casing is defined using a hyperelastic-viscoelastic material model calibrated to experimental data. It was also validated with previously published experimental data of soccer ball impact and rebound off a rigid wall. The human head model is a previously validated head model where the brain’s mechanical behavior is defined using an internal state variable model, calibrated to dynamic strain rate experiments, and validated with published experimental data. The FE study was designed through the implementation of the Latin Hypercube Sampling (LHS) model, considering the three variables, leading to a total number of 66 FE simulations being considered for this study.

The results of the FE simulations provide insight into the mechanisms of injury and the regions of the brain that are affected due to the soccer ball impacting the head. Results further indicate that the location of impact as well as the ball velocity are factors that affect the response throughout the brain. Higher soccer ball velocities produced more detrimental brain responses, when compared with lower soccer ball velocities. Additionally, the active neck condition reduced the impact response of the brain from the soccer ball impacts as compared to the results of the passive head and neck condition.