Mechanical behaviours of intervertebral discs: clinical implications of loading, injury and treatment

Dougill, Gary (2016) Mechanical behaviours of intervertebral discs: clinical implications of loading, injury and treatment. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Back pain is a significant public health concern with an increasing socioeconomic cost due to lost working days and direct medical expenditure. The majority of these costs can be attributed to long term pain resulting from specific physiological conditions. Acute injury and chronic degeneration of the intervertebral disc have been linked with pain and can reduce mobility, negatively impacting quality of life. Treatments using mesenchymal stem cells have been proposed as a means of repairing damaged and degenerate discs but questions remain around the effects of the invasive medical interventions required by these treatments. Understanding and categorising the changes in mechanical behaviour of the intervertebral disc when it is healthy, injured and degenerate, and having undergone treatment will provide valuable clinical evidence of the safety and efficacy of these treatments before risking human subjects in clinical trials. The following report contains a literature survey of the field of intervertebral disc biomechanics with specific emphasis on disc degeneration, injury and stem cell treatment, and investigates loading during activities of daily living (ADLs) using in vivo and in vitro testing methods. The work investigates thermal behavior from viscoelastic loading and the mechanical performance of hydrogel injection based clinical interventions. Damaged and degenerate discs displayed significantly altered material behaviours than healthy discs when subjected to loading simulating ADLs. Degenerate discs further injected with a proprietary hydrogel designed for stem cell interventions recovered healthy material behaviours but did not regain full tissue functionality. Combined, the studies presented in this work narrow the search for potential mechanisms of degeneration of the intervertebral disc and show the beneficial effects of hydrogel injections on the mechanical functionality of intervertebral discs even without the addition of mesenchymal stem cells to those injections.