A large proportion of overexertion injuries in sport and work related activities occur during high strain rate loading. The disc is known to have time dependent material properties (1). The joint load and stiffness may increase and the mode of failure may change from a location to another when higher loading rates are sustained (2). In order to quantify the response of the spine to dynamic loads, we need to account for the rate dependencies of the intervertebral disc in tension as well as other loading conditions. Bending tasks stretch the annulus fibrosus in the vertical direction and render the disc vulnerable to prolapse if the hydrostatic pressure in the nucleus pulposus is raised at the same time. Thus, the ability of the annulus to resist repeated vertical stretching may have a decisive influence on a disc’s susceptibility to prolapse. Tensile properties of the annulus fibrosus have been reported in the literature (3). However, to what extent loading rate can affect annulus tensile properties still needs to be clarified. The objective of this study was to investigate the loading rate sensitivity and regional variations in tensile mechanical properties of the annulus fibrosus, using disc annulus specimens from sheep.

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