Effect of Velocity and Contact Stress Area on the Dynamic Behavior of the Spinal Cord Under Different Testing Conditions

Abstract

Knowledge of the dynamic behavior of the spinal cord under different testing conditions is critical for our understanding of biomechanical mechanisms of spinal cord injury. Although velocity and contact stress area are known to affect external mechanical stress or energy upon sudden traumatic injury, quantitative investigation of the two clinically relevant biomechanical variables is limited. Here, freshly excised rat spinal-cord–pia-arachnoid constructs were tested through indentation using indenters of different sizes (radii: 0.25, 0.50, and 1.00 mm) at various loading rates ranging from 0.04 to 0.20 mm/s. This analysis found that the ex vivo specimen displayed significant nonlinear viscoelasticity at <10% of specimen thickness depth magnitudes. At higher velocity and larger contact stress area, the cord withstood a higher peak load and exhibited more sensitive mechanical relaxation responses (i.e., increasing amplitude and speed of the drop in peak load). Additionally, the cord became stiffer (i.e., increasing elastic modulus) and softer (i.e., decreasing elastic modulus) at a higher velocity and larger contact stress area, respectively. These findings will improve our understanding of the real-time complex biomechanics involved in traumatic spinal cord injury.

Role of durotomy on function outcome, tissue sparing, inflammation, and tissue stiffness after spinal cord injury in rats

“…The spinal cord tissue was dissected and prepared using standard procedures before indentation testing, as previously described (Method S3 ). 53 …”

“…The spinal cord tissue was dissected and prepared using standard procedures before indentation testing, as previously described (Method S3). 53 Indentation measurements were utilized to generate stiffness maps for the purpose of analyzing the spatial organization of the elastic modulus of the spinal cord. A total of 54 rats were used in the studies, with 24 rats in the SCI + laminectomy group, 24 rats in the SCI + durotomy group, and six rats in the control group.…”