Confined compression of canine annulus fibrosus under chemical and mechanical loading.

Uniaxial confined compression and swelling experiments on cylindrical specimens taken either in an axial or in a radial direction from a canine lumbar annulus fibrosus are presented. The loading protocol consisted of a combination of stepwise mechanical and chemical loading. Swelling and consolidation curves of normalized displacement versus square root of normalized time did not show a dependence on site or orientation of the specimen. All stages in which height increases, namely, conditioning, swelling, and desolidation show only slight differences in these normalized curves. Consolidation is initially faster, and later slower. The transport coefficient for axial specimens is higher than for radial specimens, for consolidation e.g., 3.14 +/- 1.56 10(-10) m2s(-1) and 1.11 +/- 0.33 10(-10) m2s(-1) respectively, the biphasic aggregate moduli are 1.01 +/- 0.31 MPa and 0.66 +/- 0.30 MPa, respectively.