A biomechanical model of traumatic contusional injury produced by controlled cerebrocortical indentation in sheep

Abstract

A biomechanical model of traumatic contusional injury was used to map axonal damage and neuronal reaction proximal and distal from the contusion. The model uses a precisely controlled and characterised dynamic indentation of the cerebral cortex of anaesthetised sheep. The indentation (16.15-16.50 mm deep; contact speed 1.2-1.24 m/s) is made through a 20 mm craniotomy in the frontal bone. The brain is then perfused-fixed after 6 hours and sectioned at 5 mm intervals. Immunohistochemistry was used to detect axonal injury and neuronal reaction. Quantitation of injury was by an automatic counting algorithm applied to micrographs of each entire section. These maps were cross-checked with manual counts. The injury was characterised by well-defined zones radiating from the impact point; these were a region of haemorrhagic and necrotic tissue, subadjacent penumbra of axonal injury, and distal multi-focal and diffuse areas of neuronal positivity. The model includes precise characterisation of the contact load and the pattern of injury. This will allow future finite element modelling to be used to explore quantitative relationships between several forms of neural damage and the dynamics of the tissue deformation in a finite element model of the insult.