[Injury tolerance of the human skull in relation to simulation of impact acceleration]

A mathematical torso-neck-head model was used to simulate frontal and lateral head impact. The model consisted of nine rigid bodies representing the torso, the seven vertebrae, and the head. The external force acting during impact was described by a triangular force-time function. The impact conditions were varied, i.e., the mass of the head (1.5 and 5.5 kg), the mass (0.1 and 1.0 kg) and velocity (10, 30, and 50 m/s) of the impacting body, and the elasticity (0.5 and 1.0) of the impact. The computer simulations produced linear and angular head accelerations, which were compared with the tolerance level for injury and used to determine the tolerance curves which discriminate between "safe" and "unsafe" acceleration. For the linear head acceleration, the tolerance level was 1000 as defined by the Head Injury Criterion, and for the angular head acceleration the tolerance level was 1800 rad/s2. Our results showed that the risk of head injury was lower for linear head acceleration than for angular head acceleration, and it was lower for frontal impact than for lateral impact.