Dynamic Tensile Behavior of Fiber Bundles Isolated From Spinal Neve Roots: Effects of Anatomical Site and Loading Rate on Mechanical Strength

Abstract

We found a significant difference (P < 0.05) between the linear portion of the elastic modulus (∼20 MPa) and tensile strength (∼2 MPa) at the 0.2 mm/s (low: 0.01 s−1), 2 mm/s (medium: 0.11 s−1), and 20 mm/s (high: 1.11 s−1) loading rates by performing a series of uniaxial stretching tests. However, the mechanical properties of the neural fiber bundles were resultantly of the same magnitude, indicating that their mechanical responses were relatively insensitive to a given strain rate regardless of a 100-fold increase in the applied stretching velocities. We also confirmed that a “spinal level effect” exists in the nerve roots, i.e., a fiber bundle isolated from the lumbar spinal level is weaker in mechanical strength compared to that from the cervical and thoracic spinal levels (P < 0.05), suggesting that closer attention should be paid to an anatomical site from which test samples are excised.