Working with Dr. Jack Callaghan, the Canada Research Chair in Spine Biomechanics and Injury Prevention, Dr. Chad Gooyers conducted one of the first experiments to examine the cycle-varying changes in the mechanical properties of intervertebral disc tissue under cyclic biaxial tensile loading conditions.
Numerous in vitro studies have examined the initiation and propagation of fatigue injury pathways in the intervertebral disc using functional spinal units (see Figure 1, below); however, there have been fewer studies performed with isolated tissue samples under biaxial loading conditions. Results from this study demonstrate that with cyclic biaxial tension applied to multilayer samples of annulus fibrosus tissue, several statistical interactions emerged between the magnitude of tissue stretch, cycle rate and location on the disc where the tissue samples were harvested from.
Based on the greater magnitudes of peak stress that were observed in tissue samples obtained from the posterior-lateral region of the disc, it is hypothesized that these changes may provide a theory to explain the increased prevalence of micro-structural damage that has previously been documented in this region of the intervertebral disc. These findings are discussed in the context of the known mechanisms for structural damage that have been linked to fatigue loading in the intervertebral disc.
Gooyers, C.E. & Callaghan, J.P. (2016). Peak stress in the annulus fibrosus under cyclic biaxial tensile loading. Journal of Biomechanical Engineering, In Press.