Shaken baby syndrome: simulation via computational and physical modelling

The terms "abusive head injury" and "shaken baby syndrome" refer to a unique pattern of non-accidental traumatic injury occurring in children that many clinicians and researchers have good reason to believe is caused by violent shaking. Typical injuries include subdural haemorrhage, retinal haemorrhage as well as tears to cortical bridging veins. A major paradox is that the injuries induced by a shaking event are much more severe than those caused by even violent single - impact head trauma, despite the relatively low accelerations in shaking. Infants younger than 6 months are significantly more vulnerable to the shaken baby syndrome than older infants and children, and one possible explanation is given that the softness of the infant brain and compliant skull structure allows violent motions to be set up (Cheng et al. 2005). These new mechanisms, could have an important role in explaining the basic mechanics of shaken baby syndrome. Several models of infant head have been created with the optimized anatomical detail and accurate constitutive material properties from literature. The driving input to these models is derived from data generated in our research programme at the Transport Research Laboratory (TRL) (Brudenell 2000) with the theory of kinematics rigid body reconstruction. Numerical simulations are applied by using the finite element system LS-DYNA, and the consequences have been correlated with clinically observed damage in infant victims, and the brain skull boundary condition is investigated via the fluid structure interaction (FSI) method. A shaking testing apparatus has been custom designed with computer aided design methodology (CAD), and is manufactured and assembled in the workshop. The driving of the rig is able to apply stable, repetitive linear motion within the range of accuracy and magnitude of human shaking. An experimental model has been constructed and mounted on the rig with important structures consisting of brain, cerebrospinal fluid (CSF), skull and infantile membrane. The system validates the computational modelling by demonstrating the relative motion of the continuum system within the transparent skull replica. The research, as a first exploration in this area, contributes to the study of the infant abusive head injury, and is able to draw the data together in a discussion of the implications for the mechanics of the shaken baby syndrome.