The effect of collagen fibril orientation on the biphasic mechanics of articular cartilage

Abstract

The highly inhomogeneous distribution of collagen fibrils may have important effects on the biphasic mechanics of articular cartilage. However, the effect of the inhomogeneity of collagen fibrils has mainly been investigated using simplified three-layered models, which may have underestimated the effect of collagen fibrils by neglecting their realistic orientation. The aim of this study was to investigate the effect of the realistic orientation of collagen fibrils on the biphasic mechanics of articular cartilage. Five biphasic material models, each of which included a different level of complexity of fibril reinforcement, were solved using two different finite element software packages (Abaqus and FEBio). Model 1 considered the realistic orientation of fibrils, which was derived from diffusion tensor magnetic resonance images. The simplified three-layered orientation was used for Model 2. Models 3-5 were three control models. The realistic collagen orientations obtained in this study were consistent with the literature. Results from the two finite element implementations were in agreement for each of the conditions modelled. The comparison between the control models confirmed some functions of collagen fibrils. The comparison between Models 1 and 2 showed that the widely-used three-layered inhomogeneous model can produce similar fluid load support to the model including the realistic fibril orientation; however, an accurate prediction of the other mechanical parameters requires the inclusion of the realistic orientation of collagen fibrils.

Numerical analysis of mineral crystals on mechanical properties of mineralized collagen fibers

“…Mineralized collagen fibers are the main bone matrix and the basis of bone hierarchical structure. 4,5 Mineralized collagen fibers consist of collagen, hydroxyapatite (HA) crystal, and other organic and inorganic components. 6 The highly anisotropic hierarchical structure of mineralized collagen fibers enables bone to adapt to a variety of external forces.…”

Cartilage Biomechanical and Mechanobiological Response to Sliding Contact

“…Hence, the cartilage was modeled as fibril reinforced biphasic material using the well-known three layers structure where the superficial zone (SZ), middle zone (MZ), and the deep zone (DZ) represented 20%, 50%, and 30% of the tissue thickness, respectively (Mow et al, 1992). This model produced fluid pressure distribution that was very close to FE model that used realistic collagen fiber orientation (Meng et al, 2017).…”

“…FEBio was validated against two well established and verified FE codes, ABAQUS (Version 6.7, Simulia, Providence, RI) andNIKE3D(Ver-sion 3.4.1, Methods Development Group, Lawrence Livermore-National Laboratory, Livermore, CA) (Maker, 1995) or compared to analytical solutions. Also, many studies in the literature have produced identical results using FEBio and another FE codes (Meng et al, 2013(Meng et al, , 2017MacLeod et al, 2016).…”

“…Articular cartilage exhibits depth-dependent structure and composition which results in depth-dependent material properties (Wilson et al, 2007;Shirazi et al, 2008). However, for simplification, this study considered only the in-homogeneity of the collagen fibers which is believed to have a great effect on the fluid pressure (Meng et al, 2017). Hence, the cartilage was modeled as fibril reinforced biphasic material using the well-known three layers structure where the superficial zone (SZ), middle zone (MZ), and the deep zone (DZ) represented 20%, 50%, and 30% of the tissue thickness, respectively (Mow et al, 1992).…”

“…The fiber modulus (ξ) in the unstrained condition was calculated from H +A = 4ξ, where H +A is the cartilage tensile stiffness. The tensile stiffness for MZ and DZ were taken to be 50% and 33%, respectively, of the SZ (Verteramo and Seedhom, 2004;Chegini and Ferguson, 2010;Meng et al, 2017). Material properties for bovine articular cartilage are given in Table 2.1.…”