Mechanical properties of bovine pia-arachnoid complex in shear.

Traumatic brain injury (TBI) has become a major public health and socioeconomic problem that affects 1.5 million Americans annually. Finite element methods have been widely used to investigate TBI mechanisms. The pia-arachnoid complex (PAC) covering the brain plays an important role in the mechanical response of the brain during impact or inertial loading. Existing finite element brain models have tended to oversimplify the response of the PAC due to a lack of accurately defined material properties of this structure, possibly resulting in a loss of accuracy in the model predictions. The objectives of this study were to experimentally determine the material properties of the PAC under shear loading. Bovine PAC was selected in the current study in view of its availability and comparability with previous studies. Tangential shear tests were conducted at 0.8, 7.3, and 72 s(-1). The mean shear moduli were 11.73, 20.04, and 22.37 kPa at the three strain rates tested. The ultimate stress, at the three strain rates, was 9.21, 17.01, and 22.26 kPa, while the ultimate strain was 1.52, 1.58, and 1.81. Results from the current study provide essential information to properly model the PAC membrane, an important component in the skull/brain interface, in a computational model of the human/animal head. Such an improved representation of the in vivo skull/brain interface will enhance future studies investigating brain injury mechanisms under various loading conditions.