Measuring in Vivo Internal Spinal Cord Deformations During Experimental Spinal Cord Injury Using a Rat Model, Radiography, and Fiducial Markers

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Abstract

Spinal cord injuries (SCIs) are commonly studied experimentally by causing injury to rodent spinal cords in vivo and analyzing behavioral and histological results post injury. Few researchers have directly investigated the deformation of the in vivo spinal cord during impact, which is thought to be a predictor of injury. This knowledge would help to establish correlations among impact parameters, internal structure deformation, and histological and functional outcomes. The objective of this thesis was to develop a radiographic method of tracking the realtime internal deformations of an anesthetized rat‘s spinal cord during a typical experimental SCI.

A technique was developed for injecting fiducial markers into the dorsal and ventral white and grey matter of in vivo rat spinal cords. Two radio-opaque beads were injected into C5/6 in the approximate location of the dorsal and ventral white matter. Four additional beads were glued to the surface of the cord caudal and cranial to the injection site (one dorsal, one ventral). Overall bead displacement was measured during quasi-static compression using standard medical x-ray equipment. Dynamic bead displacement was tracked during a dorsal impact (130mm/s, 1mm depth) by imaging laterally at 3,000 fps using a custom high-speed x-ray system.

The internal spinal cord beads displaced 1.02-1.7 times more than the surface beads in the cranial direction and 2.5-11 times more in the ventral direction for the dynamic impact and maximum quasi-static compressions. The dorsal spinal cord beads (internal and surface) displaced more than the ventral spinal cord beads during all compressions. Finite element modeling and experimental measurements suggested that bead migration with respect to the spinal cord tissue was small and mostly insignificant.

These results support the merit of this technique for measuring in vivo spinal cord deformation. The differences in bead displacements imply that the spinal cord undergoes complex internal and surface deformations during impact. Many applications of this technique are conceivable including validating finite element and surrogate models of the spinal cord, comparing localized grey and white matter motion during impact to histological findings, and improving SCI preventative and treatment measures.

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Cited By (2)

Year	Entry
2011	Wilson KJ. Assessing the Accuracy of Using Biplanar Radiography Combined With Computed Tomography to Estimate Cartilage Deformation in the Hip [Master's thesis]. Vancouver, BC: University of British Columbia; August 2011.
2012	Russell CM. A Nonlinear Finite Element Model of the Rat Cervical Spine: Validation and Correlation With Histological Measures of Spinal Cord Injury [Master's thesis]. Vancouver, BC: University of British Columbia; August 2012.