The interface between the Achilles Tendon (AT) and calcaneus comprises soft and hard connective tissues. Such interfaces are vulnerable to mechanical damage. Tendon to Bone Insertion Region (TBIR) has unique microstructural characteristics for reinforcement. This region constitutes almost 10% of the AT's distal end. The rest of the tendon (tendon proper) has longitudinal fiber orientation with no mineral content. Although, the TBIR lacks longitudinally organized fibers and at the same time, incorporates mineral molecules. In this study, a 3D computational model of the TBIR proposed to underline several reinforcement mechanisms. The obtained results showed that off-axis alignment of fibers, when coupled with the mineral deposition, shifts the stress concentration region to the tendon proper. In the case of altering each parameter individually, probable failure observed in the bone interface, which causes complications in surgical procedure or during healing. A gradual increase of mineral compensates for the stiffness mismatch between the AT and calcaneus. The proposed computational framework illustrated the complementary roles of fiber orientation and mineral molecules: nearly transverse orientation of fibers alleviated the stress concentration locally, while mineral deposition directly enhanced the TBIR stiffness.

中文翻译：

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阿基里斯腱生物力学的微观结构建模，重点是骨骼插入部位。

跟腱（AT）和跟骨之间的界面包括软性和硬性结缔组织。这样的接口容易受到机械损坏。肌腱到骨的插入区域（TBIR）具有独特的增强微结构特征。该区域几乎构成了AT远端的10％。其余的腱（固有肌腱）具有纵向纤维取向，无矿物质含量。虽然，TBIR缺乏纵向组织的纤维，但同时掺入了矿物分子。在这项研究中，提出了TBIR的3D计算模型来强调几种加固机制。所得结果表明，当纤维与矿物沉积结合时，纤维的偏心排列将应力集中区域转移到了适当的腱上。在单独更改每个参数的情况下，在骨骼界面中观察到可能的故障，这会导致外科手术或愈合过程中的并发症。矿物质的逐渐增加补偿了AT和跟骨之间的刚度不匹配。拟议的计算框架说明了纤维取向和矿物分子的互补作用：纤维的近乎横向取向减轻了局部应力集中，而矿物沉积直接提高了TBIR刚度。