Tissue-level stress-relaxation of ligaments and tendons in the toe region is characterized by fast and long-term relaxations and an increase in relaxation magnitude with strain. Characterizing the compositional and structural origins of these phenomena helps in the understanding of mechanisms of ligament and tendon function and adaptation in health and disease. A three-step tensile stress-relaxation test was conducted on dumbbell-shaped pieces of bovine knee ligaments and patellar tendon (PT) (n = 10 knees). Their mechanical behaviour was characterized by a fibril-reinforced poroviscoelastic material model, able to describe characteristic times and magnitudes of fast and long-term relaxations. The crimp angle and length of tissues were measured with polarized light microscopy, while biochemical contents were determined by colorimetric biochemical methods. The long-term relaxation time was longer in the anterior cruciate ligament (ACL) and PT compared with collateral ligaments (p < 0.05). High hydroxyproline content predicted greater magnitude and shorter time of both fast and long-term relaxation. High uronic acid content predicted longer time of long-term relaxation, whereas high crimp angle predicted higher magnitude of long-term relaxation. ACL and PT are better long-term stabilizers than collateral ligaments. The long-term relaxation behaviour is affected or implied by proteoglycans and crimp angle, possibly relating to slow structural reorganization of the tissue.

中文翻译：

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牛膝关节韧带和髌腱的结构、成分和原纤维增强的多孔粘弹性

脚趾区域韧带和肌腱的组织级应力松弛的特征是快速和长期松弛以及松弛幅度随应变增加。表征这些现象的组成和结构起源有助于理解韧带和肌腱功能以及健康和疾病适应的机制。对牛膝韧带和髌腱 (PT)（n = 10 膝）的哑铃形件进行了三步拉伸应力松弛试验。它们的机械行为以原纤维增强的多孔粘弹性材料模型为特征，能够描述快速和长期松弛的特征时间和幅度。用偏光显微镜测量组织的卷曲角度和长度，生化含量采用比色生化法测定。与侧副韧带相比，前交叉韧带 (ACL) 和 PT 的长期松弛时间更长（p < 0.05）。高羟脯氨酸含量预示着快速和长期放松的幅度更大，时间更短。高糖醛酸含量预示着长期松弛的时间更长，而高卷曲角预示着长期松弛的幅度更大。ACL 和 PT 是比侧副韧带更好的长期稳定器。长期松弛行为受蛋白多糖和卷曲角的影响或暗示，可能与组织的缓慢结构重组有关。高羟脯氨酸含量预示着快速和长期放松的幅度更大，时间更短。高糖醛酸含量预示着长期松弛的时间更长，而高卷曲角预示着长期松弛的幅度更大。ACL 和 PT 是比侧副韧带更好的长期稳定器。长期松弛行为受蛋白多糖和卷曲角的影响或暗示，可能与组织的缓慢结构重组有关。高羟脯氨酸含量预示着快速和长期放松的幅度更大，时间更短。高糖醛酸含量预示着长期松弛的时间更长，而高卷曲角预示着长期松弛的幅度更大。ACL 和 PT 是比侧副韧带更好的长期稳定器。长期松弛行为受蛋白多糖和卷曲角的影响或暗示，可能与组织的缓慢结构重组有关。