Quinn Kyle P, Winkelstein Beth A
Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA.
J Biomech Eng. 2011 Jun;133(6):064506. doi: 10.1115/1.4004205.
Although the mechanical phenomena associated with preconditioning are well-established, the underlying mechanisms responsible for this behavior are still not fully understood. Using quantitative polarized light imaging, this study assessed whether preconditioning alters the collagen fiber alignment of ligament tissue, and determined whether changes in fiber organization are associated with the reduced force and stiffness observed during loading. Collagen fiber alignment maps of facet capsular ligaments (n = 8) were generated before and after 30 cycles of cyclic tensile loading, and alignment vectors were correlated between the maps to identify altered fiber organization. The change in peak force and tangent stiffness between the 1st and 30th cycle were determined from the force-displacement response, and the principal strain field of the capsular ligament after preconditioning was calculated from the fiber alignment images. The decreases in peak ligament force and tangent stiffness between the 1st and 30th cycles of preconditioning were significantly correlated (R ≥ 0.976, p < 0.0001) with the change in correlation of fiber alignment vectors between maps. Furthermore, the decrease in ligament force was correlated with a rotation of the average fiber direction toward the direction of loading (R = -0.730; p = 0.0396). Decreases in peak force during loading and changes in fiber alignment after loading were correlated (p ≤ 0.0157) with the average principal strain of the unloaded ligament after preconditioning. Through the use of a vector correlation algorithm, this study quantifies detectable changes to the internal microstructure of soft tissue produced by preconditioning and demonstrates that the reorganization of the capsular ligament's collagen fiber network, in addition to the viscoelasticity of its components, contribute to how the mechanical properties of the tissue change during its preconditioning.
尽管与预处理相关的力学现象已得到充分证实，但其背后的作用机制仍未完全明确。本研究采用定量偏振光成像技术，评估预处理是否会改变韧带组织中胶原纤维的排列方向，并确定纤维组织的变化是否与加载过程中观察到的力和刚度降低有关。在进行30次循环拉伸加载前后，生成了小关节囊韧带（n = 8）的胶原纤维排列图，并对这些图之间的排列向量进行相关性分析，以识别纤维组织的改变。根据力-位移响应确定第1次和第30次循环之间峰值力和切线刚度的变化，并根据纤维排列图像计算预处理后囊韧带的主应变场。预处理第1次和第30次循环之间韧带峰值力和切线刚度的降低与各图之间纤维排列向量相关性的变化显著相关（R≥0.976，p＜0.0001）。此外，韧带力的降低与平均纤维方向朝着加载方向的旋转相关（R = -0.730；p = 0.0396）。加载过程中峰值力的降低与加载后纤维排列的变化与预处理后未加载韧带的平均主应变相关（p≤0.0157）。通过使用向量相关算法，本研究量化了预处理对软组织内部微观结构产生的可检测变化，并证明囊韧带胶原纤维网络的重组及其成分的粘弹性共同影响了组织在预处理过程中力学性能的变化方式。
