Maximum Principal Strain Correlates with Spinal Cord Tissue Damage in Contusion and Dislocation Injuries in the Rat Cervical Spine

Abstract

The heterogeneity of the primary mechanical mechanism of spinal cord injury (SCI) is not currently used to tailor treatment strategies because the effects of these distinct patterns of acute mechanical damage on long-term neuropathology have not been fully investigated. A computational model of SCI enables the dynamic analysis of mechanical forces and deformations within the spinal cord tissue that would otherwise not be visible from histological tissue sections. We created a dynamic, three-dimensional finite element (FE) model of the rat cervical spine and simulated contusion and dislocation SCI mechanisms. We investigated the relationship between maximum principal strain and tissue damage, and compared primary injury patterns between mechanisms. The model incorporated the spinal cord white and gray matter, the dura mater, cerebrospinal fluid, spinal ligaments, intervertebral discs, a rigid indenter and vertebrae, and failure criteria for ligaments and vertebral endplates. High-speed (∼ 1 m/sec) contusion and dislocation injuries were simulated between vertebral levels C3 and C6 to match previous animal experiments, and average peak maximum principal strains were calculated for several regions at the injury epicenter and at 1-mm intervals from +5 mm rostral to -5 mm caudal to the lesion. Average peak principal strains were compared to tissue damage measured previously in the same regions via axonal permeability to 10-kD fluorescein-dextran. Linear regression of tissue damage against peak maximum principal strain for pooled data within all white matter regions yielded similar and significant (p<0.0001) correlations for both contusion (R(2)=0.86) and dislocation (R(2)=0.52). The model enhances our understanding of the differences in injury patterns between SCI mechanisms, and provides further evidence for the link between principal strain and tissue damage.

A novel closed-body model of spinal cord injury caused by high-pressure air blasts produces extensive axonal injury and motor impairments

“…Interestingly, for a wide variety of spinal cord injury models (i.e. compression, dislocation, distraction, and hyperextension — Choo et al, 2007, 2008; Clarke et al, 2008; Lam et al, 2014; Li and Dai, 2009; Russell et al, 2012; Seifert et al, 2011), axonal injury has been shown to be most predominant in the ventral white matter. Such injury is not, however, necessarily limited to neurofilament compaction.…”

“…Several groups of investigators have developed finite element models of the spinal cord (Lam et al, 2014; Li and Dai, 2009; Maikos et al, 2008; Russell et al, 2012; Sparrey et al, 2009) to evaluate biomechanical forces during spinal injuries. Interestingly, these models generally predict significant damage to the ventral white matter, even without necessarily positing compression of the spinal cord against the inner surface of the vertebral column.…”

Benefits of Spine Stabilization with Biodegradable Scaffolds in Spinal Cord Injured Rats

“…35 In this sense, it would be possible to study the response of the SPCL scaffolds to mechanical stresses usually found in the human body. Additionally, the spine model may be combined with an SCI mathematical model, as the one described by Russell and colleagues, 36 in order to further understand the neuroprotective effect of SPCL stabilization in an SCI situation.…”

Drug delivery, cell-based therapies, and tissue engineering approaches for spinal cord injury

“…The primary injury is considered to be disruption of neural tissue as the immediate result of the blunt, non-penetrating mechanical forces applied at high velocity to the spinal cord as the surrounding bony/ligamentous spinal column fails. Primary mechanical trauma exerts distraction, compression, and shear forces on the spinal cord (4, 5), and can cause damage not only to the central nervous system (CNS) but also the peripheral nervous system (6). Vascular, cellular and axonal damage occurs almost instantaneously and continues to spread from the injury epicenter both radially and axially.…”