Background and Objective

Cartilage cracks and fissures may occur due to certain daily life activities such as sports practice, blunt trauma, and matrix fibrillation during early osteoarthritis. These cracks could further grow at the macroscopic level, alter the load distribution pattern in the matrix, limit the joint range of motion, and disturb chondrocytes synthesis. Cracks' shape and deformations in the loaded cartilage may affect the subsequent mechanobiological processes in the long term, likely because of the altered fluid exchange and excessive local deformations in the vicinity of the damage site. The fibrillar structure of the cartilage matrix appeared to have a protective effect against excessive deformations and tissue failure. Hence, in the present study, a fibril reinforced biphasic cartilage model was used to assess the potential role of different fibril orientations on the profile of a vertical crack in cartilage after applying a compressive load.

Methods

A 20 × 20 × 1.5 mm³ cartilage model was developed with a 0.7 mm length V-shape cut at the center. Using an impermeable indenter, a 27% compression was applied to immature, mature, and isotropic cartilage models. Each of immature and mature groups had 4 different split line directions with respect to the cut edges, including 90°, 45°, 0°, and random orientation. The latter represented the disrupted collagen fibril orientations in early osteoarthritis. The model was verified with the experimental results in the literature.

Results

In the superficial zones, the larger angle between the split lines and cut edges resulted in a wider cut opening. In the absence of collagen fibrils, the isotropic model resulted in a closed edge profile. Also, under a consistently applied compression, the OA model, with random collagen fibril distribution on its surface, had the smallest load-bearing capacity compared to the other models.

Conclusions

Findings highlighted a primary role of collagen fibrils on the cut profile, which was more pronounced at dynamic rather than static conditions. Split lines perpendicular to the cut edges had some protective effects against the large dislocation of cut edges. These findings could be utilized to develop engineered tissues less susceptible to rupture. Moreover, the outcome of the present study can explain the potential causes of the crack propagation path reported in the literature.

中文翻译：

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胶原纤维分布对关节软骨裂纹的影响。

背景与目的

由于某些日常活动，例如体育锻炼，钝伤和早期骨关节炎期间的基质纤颤，可能会发生软骨裂痕。这些裂纹可能会在宏观水平上进一步增长，改变基质中的载荷分布模式，限制关节运动范围，并干扰软骨细胞的合成。从长远来看，裂纹的形状和变形可能会影响随后的力学过程，这很可能是由于流体交换改变和损伤部位附近的局部过度变形所致。软骨基质的原纤维结构似乎具有防止过度变形和组织衰竭的保护作用。因此，在本研究中，

方法

开发了一个20×20×1.5 mm ^3的软骨模型，其中心切割了一个0.7 mm长的V形。使用不渗透压头，将27％的压缩力应用于未成熟，成熟和各向同性的软骨模型。未成熟和成熟组的每个相对于切割边缘具有4个不同的分割线方向，包括90°，45°，0°和随机方向。后者代表早期骨关节炎中胶原纤维原位的破坏。用文献中的实验结果验证了该模型。

结果

在表层区域，分割线和切割边缘之间的较大角度导致切割开口变宽。在没有胶原纤维的情况下，各向同性模型导致封闭的边缘轮廓。同样，在持续施加压缩的情况下，与其他模型相比，OA模型在其表面具有随机的胶原纤维分布，具有最小的承载能力。

结论

研究结果强调了胶原纤维在切割轮廓上的主要作用，在动态而不是静态条件下更为明显。垂直于切割边缘的分割线对切割边缘的大错位具有一定的保护作用。这些发现可用于发展不太容易破裂的工程组织。此外，本研究的结果可以解释文献中报道的裂纹扩展路径的潜在原因。