ANISOTROPIC VISCOELASTIC SHEAR PROPERTIES OF BOVINE MENISCUS

The objectives of this study were to determine the viscoelastic shear properties of bovine menisci and to examine those variations with resp ect to the structural organization of the tissue. Disc shaped meniscal specimens were subjected to: (1) oscillatory shear deformation over a physiological range of frequencies (1-100 rads per second), and (2) s hear deformation in the range of infinitesimal strains (0.005-0.05 rad ). The dynamic shear modulus and the transient shear stress relaxation function were determined from the experiments. The dynamic shear modu lus was measured at 3 levels of compressive strain (7%, 10%, 13%). Dir ectional variations in shear properties were examined by testing axial ly, radially, and circumferentially oriented specimens. The experiment showed that meniscal tissue exhibits intrinsic viscoelastic behavior in shear that depends on frequency, shear strain, and compressive stra in. Shear anisotropy is evident and is dependent upon compression. At low compressive strains (less than or equal to 10%), the circumferenti ally oriented specimens were found to be stiffer in shear than the axi ally and radially oriented specimens. At high compressive strains (> 1 0%), no statistically significant difference was found between the cir cumferentially and axially oriented specimens. These results suggest t hat the anisotropic shear properties of the meniscus are related to th e collagen fiber orientation within the meniscus.