Effect of Regional Variations in Material Properties of the Disc on the Circadian Variation in Stature

It is the unique interaction between the solid and fluid components that provide the intervertebral discs the strength and flexibility necessary to bear the physiological loading of the spine. The current research is directed towards developing a numerical model of a lumbar disc including the fluid flow into and out of the intervertebral disc. The presence of the fluid is imperative in order to study the loading and unloading of the spine. This was accomplished by including the poroelastic behavior of the disc, the effect of the change in proteoglycan content in the disc and the effect of strain dependent permeability with respect to applied loads. It was hypothesized that the inclusion of regional variations in the material properties of the disc within the numerical model (i.e. permeability, porosity and water content) would better predict the diurnal change in disc height as compared to the model, which included only tissue specific properties.