Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland; Human Performance Laboratory, University of Calgary, 2500, University Drive NW, Calgary, Alberta T2N1N4, Canada.
Department of Applied Physics, University of Eastern Finland, POB 1627, Kuopio 70211, Finland.
Acta Biomater. 2021 May;126:301-314. doi: 10.1016/j.actbio.2021.03.031. Epub 2021 Mar 20.
Cracks in articular cartilage compromise tissue integrity and mechanical properties and lead to chondral lesions if untreated. An understanding of the mechanics of cracked cartilage may help in the prevention of cartilage deterioration and the development of tissue-engineered substitutes. The degeneration of cartilage in the presence of cracks may depend on the ultrastructure and composition of the tissue, which changes with aging, disease and habitual loading. It is unknown if the structural and compositional differences between immature and mature cartilage affect the mechanics of cartilage cracks, possibly predisposing one to a greater risk of degeneration than the other. We used a fibre-reinforced poro-viscoelastic swelling material model that accounts for large deformations and tension-compression non-linearity, and the finite element method to investigate the role of cartilage structure and composition on crack morphology and tissue mechanics. We demonstrate that the crack morphology predicted by our theoretical model agrees well with the histo-morphometric images of young and mature cracked cartilages under indentation loading. We also determined that the crack morphology was primarily dependent on collagen fibre orientation which differs as a function of cartilage depth and tissue maturity. The arcade-like collagen fibre orientation, first discussed by Benninghoff in his classical 1925 paper, appears to be beneficial for slowing the progression of tissue cracks by 'sealing' the crack and partially preserving fluid pressure during loading. Preservation of the natural load distribution between solid and fluid constituents of cartilage may be a key factor in slowing or preventing the propagation of tissue cracks and associated tissue matrix damage. STATEMENT OF SIGNIFICANCE: Cracks in articular cartilage can be detrimental to joint health if not treated, but it is not clear how they propagate and lead to tissue degradation. We used an advanced numerical model to determine the role of cartilage structure and composition on crack morphology under loading. Based on the structure and composition found in immature and mature cartilages, our model successfully predicts the crack morphology in these cartilages and determines that collagen fibre as the major determinant of crack morphology. The arcade-like Benninghoff collagen fibre orientation appears to be crucial in 'sealing' the tissue crack and preserves normal fluid-solid load distribution in cartilage. Inclusion of the arcade-like fibre orientation in tissue-engineered construct may help improve its integration within the host tissue.
关节软骨的裂缝会损害组织完整性和机械性能，如果不加以治疗，还会导致软骨损伤。了解裂缝软骨的力学特性可能有助于预防软骨恶化和开发组织工程替代品。软骨在裂缝存在的情况下发生退变可能取决于组织的超微结构和组成，这些结构和组成会随着年龄、疾病和习惯性负荷而变化。目前尚不清楚未成熟和成熟软骨之间的结构和组成差异是否会影响软骨裂缝的力学特性，从而使一种软骨比另一种软骨更容易发生退变。我们使用纤维增强的多孔粘弹性肿胀材料模型来考虑大变形和拉压非线性，并用有限元法来研究软骨结构和组成对裂缝形态和组织力学的影响。我们的研究结果表明，我们的理论模型预测的裂缝形态与压痕加载下年轻和成熟软骨的组织学形态学图像吻合良好。我们还确定，裂缝形态主要取决于胶原纤维的取向，而胶原纤维的取向随软骨深度和组织成熟度的不同而不同。Benninghoff 在他 1925 年的经典论文中首次讨论的弧形胶原纤维取向似乎有利于通过“密封”裂缝并在加载过程中部分保持流体压力来减缓组织裂缝的进展。在软骨的固体和流体成分之间保持自然的负载分布可能是减缓或防止组织裂缝及其相关组织基质损伤传播的关键因素。
关节软骨中的裂缝如果不加以治疗，可能会对关节健康造成损害，但目前尚不清楚它们是如何传播并导致组织退化的。我们使用先进的数值模型来确定加载下软骨结构和组成对裂缝形态的影响。根据在未成熟和成熟软骨中发现的结构和组成，我们的模型成功预测了这些软骨中的裂缝形态，并确定胶原纤维是裂缝形态的主要决定因素。Benninghoff 胶原纤维的弧形取向似乎对“密封”组织裂缝至关重要，并在软骨中保持正常的流体-固体负载分布。在组织工程构建体中包含弧形纤维取向可能有助于提高其与宿主组织的整合。
