靱帯モデルの有限要素解析(機械力学,計測,自動制御)  [in Japanese] Finite Element Analysis for the Ligament Model(Mechanical Systems)  [in Japanese]

Knee ligaments, especially the cruciate ligaments, are the most commonly injured in accidents or during sports activities. Therefore to measure mechanical property of ligaments can yield significant information not only for preventing its damages but also for repairing or reconstructing it. Previously we performed tensile test on bone-ligament-bone complex and fascicle, then comparing experimental tangent moduli between fascicles and ligaments showed unexpected resultant. Although ligaments are basically composed of collagen fascicles with a tangent modulus is almost negligible, the tangent modulus of ligaments is higher than that of fascicles. To investigate the reason for this, we paid special attention to its hierarchical structure and existence of ground substance between fascicles. To consider this structure, we introduced hypothesis that the fascicles have non-uniformity, and strong and weak portions are reinforced by adjoining fascicles. Furthermore ground substance contributes the interaction between fascicles to increase stiffness of tissues. As a result, tangent modulus of ligaments is higher than fascicles'. To clarify the difference of the tissue's tangent moduli, we developed a two dimensional continuous model of the ligaments composed of fascicles bundle by taking its hierarchical structure into account. We incorporated a fascicle's transverse anisotropy, kinematic non-uniformity along a fascicle and mechanical interaction between fascicles due to ground substance into the model. Simulation was performed by using Finite Element Method. The results and subsequent stress-strain curves reproduced the above mentioned characteristic and therefore we might clarify the micro failure mechanism of the ligament.