In spinal cord injuries,external forces from various directions occur at various velocities.Therefore,it is important to physically evaluate whether the spinal cord is susceptible to damage and an increase in internal...In spinal cord injuries,external forces from various directions occur at various velocities.Therefore,it is important to physically evaluate whether the spinal cord is susceptible to damage and an increase in internal stress for external forces.We hypothesized that the spinal cord has mechanical features that vary under stress depending on the direction and velocity of injury.However,it is difficult to perform experiment because the spinal cord is very soft.There are no reports on the effects of multiple external forces.In this study,we used bovine spinal cord white matter to test and analyze the anisotropy and velocity dependence of the spinal cord.Tensile-vertical,tensile-parallel,shear-vertical,and shear-parallel tests were performed on the white matter in the fibrous direction(cranial to caudal).Strain rate in the experiment was 0.1,1,10,and 100/s.We calculated the Young’s modulus of the spinal cord.Results of the tensile and shear tests revealed that stress tended to increase when external forces were applied parallel to the direction of axon fibers,such as in tensile-vertical and shear-vertical tests.However,external forces those tear against the fibrous direction and vertically,such as in tensile-parallel and shear-parallel tests,were less likely to increase stress even with increased velocity.We found that the spinal cord was prone to external forces,especially in the direction of the fibers,and to be under increased stress levels when the velocity of external forces increased.From these results,we confirmed that the spinal cord has velocity dependence and anisotropy.The Institutional Animal Care and Use Committee of Yamaguchi University waived the requirement for ethical approval.展开更多
The spinal cord is composed of gray matter and white matter.It is well known that the properties of these two tissues differ considerably.Spinal diseases often present with symptoms that are caused by spinal cord comp...The spinal cord is composed of gray matter and white matter.It is well known that the properties of these two tissues differ considerably.Spinal diseases often present with symptoms that are caused by spinal cord compression.Understanding the mechanical properties of gray and white matter would allow us to gain a deep understanding of the injuries caused to the spinal cord and provide information on the pathological changes to these distinct tissues in several disorders.Previous studies have reported on the physical properties of gray and white matter,however,these were focused on longitudinal tension tests.Little is known about the differences between gray and white matter in terms of their response to compression.We therefore performed mechanical compression test of the gray and white matter of spinal cords harvested from cows and analyzed the differences between them in response to compression.We conducted compression testing of gray matter and white matter to detect possible differences in the collapse rate.We found that increased compression(especially more than 50%compression)resulted in more severe injuries to both the gray and white matter.The present results on the mechanical differences between gray and white matter in response to compression will be useful when interpreting findings from medical imaging in patients with spinal conditions.展开更多
基金This work was supported by the Japan Society for the Promotion of Science(KARENHI grant number JP 15K20002)by the Yamaguchi University Hospital(a translational promotion grant).
文摘In spinal cord injuries,external forces from various directions occur at various velocities.Therefore,it is important to physically evaluate whether the spinal cord is susceptible to damage and an increase in internal stress for external forces.We hypothesized that the spinal cord has mechanical features that vary under stress depending on the direction and velocity of injury.However,it is difficult to perform experiment because the spinal cord is very soft.There are no reports on the effects of multiple external forces.In this study,we used bovine spinal cord white matter to test and analyze the anisotropy and velocity dependence of the spinal cord.Tensile-vertical,tensile-parallel,shear-vertical,and shear-parallel tests were performed on the white matter in the fibrous direction(cranial to caudal).Strain rate in the experiment was 0.1,1,10,and 100/s.We calculated the Young’s modulus of the spinal cord.Results of the tensile and shear tests revealed that stress tended to increase when external forces were applied parallel to the direction of axon fibers,such as in tensile-vertical and shear-vertical tests.However,external forces those tear against the fibrous direction and vertically,such as in tensile-parallel and shear-parallel tests,were less likely to increase stress even with increased velocity.We found that the spinal cord was prone to external forces,especially in the direction of the fibers,and to be under increased stress levels when the velocity of external forces increased.From these results,we confirmed that the spinal cord has velocity dependence and anisotropy.The Institutional Animal Care and Use Committee of Yamaguchi University waived the requirement for ethical approval.
基金supported by JSPS KAKENHI(No.JP 15K20002)Yamaguchi University School of Medicine Affiliated Hospital:Translational Promotion Grant and President of Yamaguchi University Strategic Expenses:Young Researcher Support Project(all to NN)
文摘The spinal cord is composed of gray matter and white matter.It is well known that the properties of these two tissues differ considerably.Spinal diseases often present with symptoms that are caused by spinal cord compression.Understanding the mechanical properties of gray and white matter would allow us to gain a deep understanding of the injuries caused to the spinal cord and provide information on the pathological changes to these distinct tissues in several disorders.Previous studies have reported on the physical properties of gray and white matter,however,these were focused on longitudinal tension tests.Little is known about the differences between gray and white matter in terms of their response to compression.We therefore performed mechanical compression test of the gray and white matter of spinal cords harvested from cows and analyzed the differences between them in response to compression.We conducted compression testing of gray matter and white matter to detect possible differences in the collapse rate.We found that increased compression(especially more than 50%compression)resulted in more severe injuries to both the gray and white matter.The present results on the mechanical differences between gray and white matter in response to compression will be useful when interpreting findings from medical imaging in patients with spinal conditions.
