Application of linear biphasic theory to finite element analysis of head impulse loading

Abstract

A finite element model of the human head by linear biphasic theory is developed to study the dynamic response of the human head to impact. Intracranial tissues are modelled as a binary mixture, i.e. the fluid and solid phases. To validate the biphasic finite element formulation, the result of the numerical analysis of a one-dimensional wave propagation problem is compared with that of analytic solution. The permeabilities of the subarachnoid space and brain which may reproduce the same coup and contre-coup CSF (cerebral spinal fluid) pressures from the monophasic model are searched in the specified range of skull permeability. Then the intracranial pressure distributions from the biphasic model for the frontal impact are compared with those from the monophasic model. In general, the biphasic model produces a more injurious intracranial pressure distribution than the monophasic model. The pressure distribution from the biphasic model shows a little higher contre-coup pressure in the frontal lobe than in the occipital region. This finding is in agreement with those clinical findings that contre-coup injuries are more frequently found in the frontal lobe. Another numerical simulation is conducted to characterize the effect of the volume ratios between two phases in the skull and subarachnoid space. From the results, it can be seen that the variation of the volume ratio in the subarachnoid space affects the intracranial pressure distribution of the lateral part while the variation in the skull does not.