Biomechanics of a sheep model of axonal injury

Abstract

The aim of this project was to investigate the feasibility of using an animal model of axonal injury to study the biomechanics of the injury. The model utilises anaesthetised sheep that are mechanically ventilated and stabilised before being subjected to a single lateral impact from a captive bolt gun. The impact force was measured using a load cell mounted in the striker, and the resulting head acceleration was measured by means of a 9-accelerometer array which was rigidly mounted to the head of the sheep. Head kinematics were transformed to anatomical coordinates using stereo-radiography. High speed cine film (1000 fps) was used for the visualisation of gross head motion. After impact, each animal was allowed to survive for a predetermined period during which anaesthesia was maintained. A complement of physiological monitors was used to measure the physiological state of the animal at all times during the experiment. In one experiment, hypqxia was induced after the physical insult. After the survival period, the animal was sacrificed and the brain removed for histological processing. The brain was sectioned, processed and examined for axonal injury using the presence of amyloid precursor protein (APP) as an indicator of injury. The distribution of axonal injury in serial sections of the brain was mapped and quantified. Five experiments, displaying a range of injury responses, are reported on in this paper. In the future, the model will be used to study the biomechanics of axonal injury.