The gray matter of the cervical spinal cord has been thought to be equally or less rigid than the white matter. Based on this assumption, various studies have been conducted on the changes of stress distributions within the spinal cord under mechanical compression, although the mechanical properties of the white and gray matters had not been fully elucidated. The present study measured the mechanical properties of the white and gray matter of bovine spinal cords. For both the white and gray matter, the stress-strain curves had a nonlinear region, followed by a linear region, and then a region where the stresses plateaued before failure. In the nonlinear region, stress was not significantly different between the gray and white matter samples (strain approximately 0-10%), while stress and Young's modulus in the gray matter was significantly higher than the white matter in the linear part of the curve. The gray matter ruptured at lower strains than the white matter. These findings demonstrated the gray matter is more rigid and fragile than the white matter, and the conventional assumption (i.e., the white matter is more rigid than the gray matter) is not correct. We then applied our data to computer simulations using the finite element method, and confirmed that simulations agreed with actual magnetic resonance imaging findings of the spinal cord under compression. In future computer simulations, including finite element method using our data, changes in stress and strain within the cervical spinal cord under compression would be clarified in more detail, and our findings would also help to elucidate the area which can easily receive histologic damage or which could have hemodynamic disorders under mechanical compression, as well as severity and location of biochemical and molecular biological changes.
The thoracolumbar junction comprises the spinal cord, nerve roots and the cauda equina, exhibiting unique anatomical features that may give rise to a diverse array of symptoms under conditions of injury, thus complicating the diagnosis of compressive disorders. The present study aimed to examine varying degrees and forms of compression at this level of the spinal cord using a two-dimensional model to calculate the relationship of these variables to injury. The degree of compression was expressed as a percentage of the spinal canal that was occupied. Results were compared with findings from clinical observations to assess the validity of the model. Analysis revealed that higher levels of compression/spinal canal occupation are associated with the presence of neurological symptoms. This finding was consistent with clinical data. Results of the present analysis warrant further research involving evaluation of compression with respect to other parameters, such as blood flow, as well as more anatomically accurate three-dimensional analysis.
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