Time varying modulators of spine injury mechanics and material properties of the intervertebral disc

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The World Health Organization has deemed low back pain one of the top three occupational health problems. Eighty percent of the population will suffer from low back pain at some point in their life making low back pain the most prevalent and costly musculoskeletal problem affecting the general population of Canada. Evidence suggests that the primary cause of low back pain is through mechanical exposure associated with everyday activities and industrial tasks. While tasks involving heavy lifting are often linked with low back pain, seemingly sedentary tasks such as prolonged standing or sitting have also been associated with low back pain. Sitting and standing are common activities in the workplace and the time spent in these postures is increasing due to automation and increasing computer usage. The overall objective of this research program is to assess the role of daily loading exposures in the generation of low back tissue damage and pain. The causes of injury initiation and progression in the structures of the spine (e.g. the intervertebral disc) due to chronic exposure will be investigated. Studies examining the demands on the low back of individuals when performing sedentary tasks will be combined with investigations at the tissue level to assess time-dependent responses of spinal tissues and the resulting injury potential. A solid understanding of the injury mechanisms associated with mechanical loading is critical for injury prevention, as the biological repair mechanisms in the intervertebral disc are slow due to the lack of blood supply to this structure. The ability of the spinal tissues to repair themselves can easily be outpaced by injury deterioration once the first stage of an injury to the intervertebral disc has occurred. The outcomes from this research will provide time dependent tissue material properties that are currently unavailable and are a limiting factor in the understanding and modeling of intervertebral and low back injuries. Ultimately, the linking of cumulative or chronic exposure with potential pain generation would be a powerful and novel contribution in developing methods to assess daily loading and set threshold limits or exposure standards to prevent injuries.