The Heterogeneous Dynamic Shear Properties of Adult Human Articular Cartilage

Due to its complicated architecture, the mechanical properties of articular cartilage (AC) are highly nonlinear and exhibit clear spatial variations that may be critical to proper function. In a previous study, we characterized the depth-dependent, steady-state shear properties of neonatal bovine tissue using a Harrick Scientific tissue deformation imaging stage (TDIS) mounted on a confocal microscope. We found that the shear modulus exhibits a global minimum at a depth of roughly 100 μm and is largest deep in the tissue [1]. However, the structure of this tissue exhibits marked differences from adult human tissue, which is more highly organized and more sparsely populated with cells. Furthermore, a recent study using a different experimental protocol showed that the spatially-dependent shear modulus of human osteochondral blocks increases monatonically with depth [2]. As a result, questions regarding the applicability of the depth-dependent shear properties of neonatal bovine tissue to healthy adult human tissue remain. The objective of this study was to compare the depth-dependent shear modulus profile of neonatal bovine AC with that of adult human AC measured using an identical methodology.