Department of Applied Physics, University of Eastern Finland, POB 1627, FI-70211 Kuopio, Finland.
J Biomech. 2012 Feb 2;45(3):579-87. doi: 10.1016/j.jbiomech.2011.11.003. Epub 2011 Nov 30.
Collagen fibrils of articular cartilage have specific depth-dependent orientations and the fibrils bend in the cartilage surface to exhibit split-lines. Fibrillation of superficial collagen takes place in osteoarthritis. We aimed to investigate the effect of superficial collagen fibril patterns and collagen fibrillation of cartilage on stresses and strains within a knee joint. A 3D finite element model of a knee joint with cartilage and menisci was constructed based on magnetic resonance imaging. The fibril-reinforced poroviscoelastic material properties with depth-dependent collagen orientations and split-line patterns were included in the model. The effects of joint loading on stresses and strains in cartilage with various split-line patterns and medial collagen fibrillation were simulated under axial impact loading of 1000 N. In the model, the collagen fibrils resisted strains along the split-line directions. This increased also stresses along the split-lines. On the contrary, contact and pore pressures were not affected by split-line patterns. Simulated medial osteoarthritis increased tissue strains in both medial and lateral femoral condyles, and contact and pore pressures in the lateral femoral condyle. This study highlights the importance of the collagen fibril organization, especially that indicated by split-line patterns, for the weight-bearing properties of articular cartilage. Osteoarthritic changes of cartilage in the medial femoral condyle created a possible failure point in the lateral femoral condyle. This study provides further evidence on the importance of the collagen fibril organization for the optimal function of articular cartilage.
关节软骨的胶原纤维具有特定的深度依赖性取向,纤维在软骨表面弯曲以呈现分裂线。在骨关节炎中,浅层胶原发生纤维化。我们旨在研究软骨内浅层胶原纤维模式和胶原纤维化对膝关节内应力和应变的影响。基于磁共振成像构建了包含软骨和半月板的膝关节的三维有限元模型。模型中包含了具有深度依赖性胶原取向和分裂线模式的纤维增强多孔粘弹性材料特性。在 1000N 的轴向冲击载荷下,模拟了具有各种分裂线模式和内侧胶原纤维化的软骨在关节载荷下的应力和应变。在该模型中,胶原纤维抵抗沿分裂线方向的应变。这也增加了沿分裂线的应力。相反,分裂线模式不会影响接触压力和孔隙压力。模拟的内侧骨关节炎增加了内侧和外侧股骨髁的组织应变,以及外侧股骨髁的接触压力和孔隙压力。本研究强调了胶原纤维组织,特别是分裂线模式所指示的胶原纤维组织,对关节软骨负重性能的重要性。内侧股骨髁的软骨骨关节炎变化在外侧股骨髁上造成了一个可能的失效点。本研究进一步证明了胶原纤维组织对关节软骨最佳功能的重要性。