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Relating Histopathology and Mechanical Strain in Experimental Contusion Spinal Cord Injury in a Rat Model

View Article: PubMed Central - PubMed

ABSTRACT

During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n = 12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R2 = 0.19), but varied in strength between individual animals (R2 = 0.06–0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.

No MeSH data available.


Related in: MedlinePlus

Strain-type visualizations. Left: In the transverse plane, the three fundamental strain types are the normal strains in the ‘X’ and ‘Y’ directions (eXX and eYY, respectively) and the shear strains (eXY and eYX, where /eXY/ = /eYX/). Right: By rotating the coordinate system by an angle, θ, all strains can be represented by two normal strains, emax and emin, acting along the new ‘1’ and ‘2’ axes, respectively. These two normal strains, emax and emin, are referred to as principal strains.
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f2: Strain-type visualizations. Left: In the transverse plane, the three fundamental strain types are the normal strains in the ‘X’ and ‘Y’ directions (eXX and eYY, respectively) and the shear strains (eXY and eYX, where /eXY/ = /eYX/). Right: By rotating the coordinate system by an angle, θ, all strains can be represented by two normal strains, emax and emin, acting along the new ‘1’ and ‘2’ axes, respectively. These two normal strains, emax and emin, are referred to as principal strains.

Mentions: Segmented images were used as inputs for a validated deformable registration algorithm22 that produced 3D displacement fields that mapped the pre-injury image to the injury image. These displacement fields were used to determine the transverse-plane Lagrangian finite strain magnitudes (i.e., eXX [lateral normal strain]; eYY [dorsoventral normal strain]; and eXY [transverse-plane shear strain]) for each image voxel (Paraview; Kitware Inc., Clifton Park, NY).23 Derived strain values were used to calculate values of maximum and minimum principal strain fields (emax and emin, respectively; Fig. 2), according to the following basic strain analysis equation (Equation 1):\documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document}\begin{align*}e_ { max , min } = \frac { e_ { XX } + e_ { YY } }{ 2 } \pm \sqrt { \left( \frac { e_ { XX } - e_ { YY } } { 2 }\right) ^2 + \left( \frac { e_ { XY } } { 2 } \right) ^2 } \tag {1 } \end{align*}\end{document}


Relating Histopathology and Mechanical Strain in Experimental Contusion Spinal Cord Injury in a Rat Model
Strain-type visualizations. Left: In the transverse plane, the three fundamental strain types are the normal strains in the ‘X’ and ‘Y’ directions (eXX and eYY, respectively) and the shear strains (eXY and eYX, where /eXY/ = /eYX/). Right: By rotating the coordinate system by an angle, θ, all strains can be represented by two normal strains, emax and emin, acting along the new ‘1’ and ‘2’ axes, respectively. These two normal strains, emax and emin, are referred to as principal strains.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5035832&req=5

f2: Strain-type visualizations. Left: In the transverse plane, the three fundamental strain types are the normal strains in the ‘X’ and ‘Y’ directions (eXX and eYY, respectively) and the shear strains (eXY and eYX, where /eXY/ = /eYX/). Right: By rotating the coordinate system by an angle, θ, all strains can be represented by two normal strains, emax and emin, acting along the new ‘1’ and ‘2’ axes, respectively. These two normal strains, emax and emin, are referred to as principal strains.
Mentions: Segmented images were used as inputs for a validated deformable registration algorithm22 that produced 3D displacement fields that mapped the pre-injury image to the injury image. These displacement fields were used to determine the transverse-plane Lagrangian finite strain magnitudes (i.e., eXX [lateral normal strain]; eYY [dorsoventral normal strain]; and eXY [transverse-plane shear strain]) for each image voxel (Paraview; Kitware Inc., Clifton Park, NY).23 Derived strain values were used to calculate values of maximum and minimum principal strain fields (emax and emin, respectively; Fig. 2), according to the following basic strain analysis equation (Equation 1):\documentclass{aastex}\usepackage{amsbsy}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{bm}\usepackage{mathrsfs}\usepackage{pifont}\usepackage{stmaryrd}\usepackage{textcomp}\usepackage{portland, xspace}\usepackage{amsmath, amsxtra}\pagestyle{empty}\DeclareMathSizes{10}{9}{7}{6}\begin{document}\begin{align*}e_ { max , min } = \frac { e_ { XX } + e_ { YY } }{ 2 } \pm \sqrt { \left( \frac { e_ { XX } - e_ { YY } } { 2 }\right) ^2 + \left( \frac { e_ { XY } } { 2 } \right) ^2 } \tag {1 } \end{align*}\end{document}

View Article: PubMed Central - PubMed

ABSTRACT

During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n = 12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R2 = 0.19), but varied in strength between individual animals (R2 = 0.06–0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.

No MeSH data available.


Related in: MedlinePlus