Quantification of morphological changes of the cervical spinal cord during traumatic spinal cord injury in a rodent model

Traumatic spinal cord injury initiates a complex pathophysiological process that eventually manifests as persistent tissue damage and possible permanent loss of neurologic function. Current experimental models are limited to measuring the gross mechanical response of the spinal cord during injury; thus, little is known about how the internal tissues of the spinal cord deform during injury. The general aims of this research were to develop a method to observe the internal deformations of the in vivo rat spinal cord during clinically-relevant injury models and to determine if the patterns of deformation were correlated to tissue damage manifesting after the injury. To facilitate this work, a novel apparatus and a number of novel methods were developed. First, an apparatus that was capable of inducing contusion and dislocation spinal cord injuries in an in vivo rat model, inside of an MR scanner, was developed. The reported contusion and dislocation injury speeds were comparable with existing spinal cord injury devices, and contusion injury magnitudes showed good accuracy and precision. The device facilitated direct observation and differentiation of the morphological change of the spinal cord tissues during injury. The three-dimensional tissue motion was quantified using a state-of-the-art deformable image registration algorithm that produced displacement fields throughout the volume of the spinal cord around the site of the injury. Furthermore, the image registration methods were validated against a gold-standard. The displacement fields were used to generate transverse-plane mechanical finite strain fields in the spinal cord and the contusion and dislocation injury mechanisms produced distinctly different patterns of tissue deformation in the spinal cord. Lastly, the relationship between mechanical strain and the ensuing tissue damage was investigated in the ventral horns of the gray matter of the spinal cord. This work suggests that compressive strain contributes to the tissue damage in the ventral horns of the gray matter. However, the most important conclusion from this work is that internal observation of the spinal cord tissue during injury provides an invaluable experimental data set that can be used to improve our understanding of the relationship between deformation during injury and manifestation of damage.Applied Science, Faculty ofMechanical Engineering, Department ofGraduat