STUDY DESIGN: Experimental investigation to determine the effect of intervertebral @entity1797 on the kinetic behavior of fluid in @entity1 anulus fibrosus. OBJECTIVES: To measure the hydraulic permeability coefficient of anulus fibrosus specimens in the axial, circumferential, and radial directions to determine the anisotropic permeability behavior of nondegenerate and degenerate @entity1 intervertebral discs over a range of ages. SUMMARY OF BACKGROUND DATA: Fluid, a major component of normal intervertebral discs, plays a significant role in their load-supporting mechanisms. Transport of fluid through the intervertebral disc is important for cell nutrition and disc viscoelastic and swelling behaviors. The hydraulic permeability coefficient is the most important material property governing the rate of fluid transport. However, little is known about the anisotropic behavior of this kinetic property and how it is influenced by @entity1797 . METHODS: Using a permeation testing apparatus developed recently, testing was performed on 306 axial, circumferential, and radial anulus fibrosus specimens from the posterolateral region of 30 @entity1 lumbar (L2-L3) discs. A new method, flow-controlled testing protocol, was developed to measure the hydraulic permeability coefficient. RESULTS: The hydraulic permeability coefficient of anulus fibrosus depended significantly on the disc degenerative grade (P = 0.0001) and flow direction (P = 0.0001). For the nondegenerate group (Grade I), the hydraulic permeability was significantly anisotropic (P < 0.05), with the greatest value in the radial direction (1.924 x 10(-15) m4/Ns) and the lowest value in the circumferential direction (1.147 x 10(-15) m4/Ns). This anisotropic kinetic (flow) behavior of anulus fibrosus varied with @entity1797 . For the Grade III specimen group, there was no significant difference in hydraulic permeability coefficient among the three major directions (P = 0.37). With @entity1797 , the hydraulic permeability coefficient was decreased in the radial direction and increased in the axial and circumferential directions. The variations of hydraulic permeability coefficient from nondegenerate discs (Grade I) to mildly degenerate discs (Grade II) in each direction were significant (P < 0.05). However, the changes in permeability from Grade II to Grade III groups were not significant (P > 0.05) except in the circumferential direction (3.8% increase; P < 0.05). CONCLUSIONS: The hydraulic permeability of @entity1 nondegenerate anulus fibrosus is direction-dependent (i.e., anisotropic), with the greatest permeability in the radial direction. With @entity1797 , the radial permeability of anulus fibrosus decreases, mainly because of decreased water content, and the axial and circumferential permeability coefficients increase, mainly because of structural change, leading to more isotropic permeability behavior for Grade III discs.

The anisotropic hydraulic permeability of XXXX lumbar anulus fibrosus. Influence of age, degeneration, direction, and water content.

@entity1797 :: ('MESH:D055959', 'Disease') :: ['disc degeneration'] @entity1 :: ('9606', 'Species') :: ['human']
@entity1 :: (9606,Species) :: ['human']
