Three-dimensional fibrilreinforced finite element model of articular cartilage

Li et al., Three-Dimensional Fibril-Reinforced Model ABSTRACT 1 Collagen fiber orientations in articular cartilage are tissue depth-dependent and joint site-specific. 2 A realistic three-dimensional (3D) fiber orientation has not been implemented in modeling fluid 3 flow-dependent response of articular cartilage, thus the detailed mechanical role of the collagen 4 network may have not been fully understood. In the present study, a previously developed fibril-5 reinforced model of articular cartilage was extended to account for the 3D fiber orientation. A 6 numerical procedure for the material model was incorporated into the finite element code 7 ABAQUS using the USER MATERIAL option. Unconfined compression and indentation testing 8 were evaluated. For indentation testing, we considered a mechanical contact between a solid 9 indenter and a medial femoral condyle, assuming fiber orientations in the surface layer to follow 10 the split-line pattern. The numerical results from the 3D modeling for unconfined compression 11 seemed reasonably to deviate from that of axisymmetric modeling. Significant fiber orientation 12 dependence was observed in the displacement, fluid pressure and velocity for the cases of 13 moderate strain-rates, or during early relaxation. The influence of fiber orientation diminished at 14 static and instantaneous compressions. 15 1