A numerical model for fibril remodeling in articular cartilage

Background: Collagen fibrils of articular cartilage have a distinct organization in mature human knee joints. It seems that a mechanobiological process drives the remodeling of newborn collagen fibrils with maturation. Therefore, the goal of the present study was to develop a collagen fibril remodeling algorithm that describes the unique collagen fibril organization in a 3D knee model.Method: A fibril-reinforced, biphasic cartilage model was used with a cuboid and a 3D human knee joint geometries. An isotropic collagen fibril distribution was assigned to the cartilage at the start of the analysis. Each fibril was rotated towards the direction that resulted in a maximum stretch at each time increment of the loading cycle.Results: The resulting pattern for the collagen fibrils was compared with split line patterns of porcine knee joint cartilage and also data published in the literature. Fibrils on the artic-ular surface had a radial pattern towards the geometrical centroid of the tibial and femoral cartilage. In the tibiofemoral contact regions of superficial zone, fibrils were oriented cir-cumferentially and randomly. In the porcine samples, the split-line patterns were similar to those obtained theoretically. Depth-wise organization of fibril network was character-ized by fibrils perpendicular to the subchondral bone in the deeper layers, and fibrils par-allel to the surface of cartilage in the superficial zone.Conclusions: The maximum stretch criterion, coupled with a biphasic constitutive model, successfully predicted the collagen fibril organization observed in the articular cartilage throughout the depth and on the articular surface.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study developed a collagen fibril remodeling algorithm to describe the unique organization of collagen fibrils in a 3D knee model. The findings revealed that collagen fibrils in articular cartilage exhibit distinct orientation patterns, indicating the involvement of mechanobiological processes in the maturation of newborn collagen fibrils.