COMPRESSIVE MECHANICAL-PROPERTIES OF THE HUMAN ANULUS FIBROSUS AND THEIR RELATIONSHIP TO BIOCHEMICAL-COMPOSITION

To enhance understanding of the biomechanical role of the intervertebr al disc, the compressive properties and biochemical composition of non degenerate samples of anulus fibrosus were determined as a function of radial position, region, and level. Because of the large swelling pro pensity of this tissue, a method was developed to test excised specime ns while maintaining their in situ geometry and hydration. Using an an alysis based on linear biphasic theory, the compressive modulus, hydra ulic permeability, and isometric swelling pressure of the anulus fibro sus were determined and correlated with the tissue composition. The fi ndings indicate that the anulus fibrosus is inhomogeneous, with region al and radial variations in both material properties and biochemical c omposition. The results of this study suggest that both structural and compositional factors may determine the mechanical behavior.