UBC Theses and Dissertations
An inverse finite element approach to modeling the rat cervical spinal cord : for use in determining the mechanical properties of the grey and white matter Sharkey, Liam Rhett
There are many cellular and therapeutic treatments for traumatic spinal cord injury (tSCI) that have shown promise in animal models, however, these treatments have been unsuccessful when applied to humans. A possible reason for this discrepancy is that animal model SCIs are well-controlled, whereas human SCIs are heterogeneous in terms of population, severity and mechanism. It is known that the mechanical injury parameters play an important role in dictating the pathophysiology of SCI. However, to fully describe the mechanics of tSCI, it is necessary to understand the mechanical properties of the spinal cord. In order to investigate the mechanical properties of the rat spinal cord, I created a finite element model to simulate experimental contusion SCIs on rats based on research by Bhatnagar et al., and evaluate morphological similarity between computationally predicted and experimentally deformed spinal cords. The model was used to determine the relative stiffnesses of the grey and white matter by iteratively assigning mechanical properties to each tissue, deforming the spinal cord to match the shape of the experimentally deformed cord, and observing the morphological similarity of the predicted and experimentally deformed grey matter shapes. Using a linear elastic, homogeneous, isotropic material model for both tissues examined, I found that for six of the seven spinal cords examined, the best model agreement occurred when the white matter was modeled as 2-3 times stiffer than the grey matter, while each tissue was held at a Poisson's ratio of 0.45. Furthermore, I found that for contusion injuries inflicted upon the mediolateral center of the spinal cord, the model predicted the deformation well, while for off-center contusions, the model was unable to capture the shape of the grey matter on the side contralateral to the contusion location. I demonstrated that the spinal cord white matter appears to be stiffer than the grey matter and that current strategies of modeling spinal cord injury do not adequately capture the complexity of the deformation of the cord as a whole. My research gives further reason to investigate the mechanical properties of the spinal cord for the purpose of computationally modeling spinal cord injury.
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