Biorheological responses of the intact and nucleotomized intervertebral discs to compressive, tensile, and vibratory stresses.

Using intact and nucleotomized discs obtained from porcine coccyges, the biorheological responses to compressive, tensile, and vibratory stresses were investigated; in particular the creep characteristic change in compressive and tensile stresses, and the dynamic elastic modulus and dissipated energy under vibratory stress were analysed. In the nucleotomized disc the viscosity coefficient and the dissipated energy were decreased. However, the elastic modulus and the dynamic elastic modulus were increased compared to the intact disc under compressive and vibratory stresses, but there was no difference between intact and nucleotomized discs in the creep response to tensile stress. After nucleotomy the disc and surrounding structures of the disc are likely to be exposed to severe mechanical stresses. These mechanical stresses on the nucleotomized disc might accelerate degeneration of the disc due to the biorheological, nutritional, and biological alterations.