Geometrical variations in white and gray matter affect the biomechanics of spinal cord injuries more than the arachnoid space

Abstract

Traumatic spinal cord contusions lead to loss of quality of life, but their pathomechanisms are not fully understood. Previous studies have underlined the contribution of the cerebrospinal fluid in spinal cord protection. However, it remains unclear how important the contribution of the cerebrospinal fluid is relative to other factors such as the white/ gray matter ratio. A finite element model of the spinal cord and surrounding morphologic features was used to investigate the spinal cord contusion mechanisms, considering subarachnoid space and white/gray matter ratio. Two vertebral segments (T6 and L1) were impacted transversely at 4.5 m s 21, which demonstrated three major results:While the presence of cerebrospinal fluid plays a significant contributory role in spinal cord protection (compression percentage decreased by up to 19%), the arachnoid space variation along the spine appears to have a limited (3% compression decrease) impact. Differences in the white and gray matter geometries from lumbar to thoracic spine levels decrease spinal cord compression by up to 14% at the thoracic level. Stress distribution in the sagittal spinal cord section was consistent with central cord syndrome, and local stress concentration on the anterior part of the spinal cord being highly reduced by the presence of cerebrospinal fluid.The use of a refined spinal cord finite element method showed that all the geometrical parameters are involved in the spinal cord contusion mechanisms. Hence, spinal cord injury criteria must be considered at each vertebral level.

Mechanical properties of the spinal cord and brain: Comparison with clinical-grade biomaterials for tissue engineering and regenerative medicine

“…Mechanical anisotropy in the human spinal cord has been previously linked to the microstructural properties of anisotropy within white matter tissue [46,47]. An improved understanding of the mechanical anisotropy that exists within the spinal cord is important for generating more accurate in silico models of traumatic spinal cord injury [48].…”

Effect of experimental, morphological and mechanical factors on the murine spinal cord subjected to transverse contusion: A finite element study

“…This shows that regardless of the assumptions made on the WM and GM material properties, it is possible to simulate the global mechanical behavior of the spinal cord. The three sets were chosen in view of the available data and have all been used in spinal cord FE model investigating injury mechanisms [12,13,18,[32][33][34]. This study demonstrated the strong impact of the choice of material properties on the local mechanical behavior throughout the spinal cord.…”

“…Yet, the mouse spinal cord and its surrounding structures have distinctive morphological and structural features, including its size and its proportion of white matter (WM) and gray matter (GM) [16] or the absence of subarachnoid space [17]. These morphological features have been shown to strongly affect the biomechanics of SCI in numerical models [18]. Thus, accurate representation of the mouse spinal cord structure is required to properly correlate numerical results (local mechanical stresses and strains) with experimental results (local tissue damage).…”

Numerical investigation of the relative effect of disc bulging and ligamentum flavum hypertrophy on the mechanism of central cord syndrome

“…However, this does not challenge our conclusions since high stress and strain appeared at less than 30of extension, which is a normal range of extension for the elderly, according to Muhle et al (1998). Thirdly, the mechanical behaviour of white and grey matter was defined by isotropic strain rate-dependent tabulated laws derived from experiments reported in the literature (Fradet et al, 2016).…”