Mechanics of damage in biological soft tissues

膝关节韧带损伤很常见，事实上，每年每3000人中就有1人前十字韧带(ACL)受伤。韧带是一种柔软的生物组织，连接关节上的骨骼。膝关节韧带通过抵抗容易分离关节骨骼的力来指导关节运动并保持关节的稳定性。一些韧带在受伤后通过产生疤痕组织来愈合，疤痕组织重新连接撕裂的韧带末端。当韧带不能愈合并重新连接撕裂的韧带末端时，需要手术重建受伤的韧带。在一定比例的患者中，受伤和重建的韧带不能保持关节的稳定性，似乎已经“伸展”，使患者容易患上痛性骨关节炎。不幸的是，韧带愈合不良的原因尚不清楚。然而，目前的提议质疑愈合过程是否能够跟上对韧带的机械要求。如果机械需求超过了愈合的潜力，在愈合的过程中韧带可能会累积损伤。韧带的日常正常载荷包括持续载荷和重复载荷，工程术语分别为蠕变和疲劳。蠕变和疲劳负荷会导致损伤累积在愈合的韧带中。这项研究的创新之处在于将已建立的连续介质损伤力学的工程原理应用于生物和医学领域的一个新问题，即韧带愈合问题的解决不佳。实验力学测试和理论数学模型将被用来帮助工程师和骨科外科医生了解损伤是如何在愈合的韧带中累积的。这项研究计划的预期收益是改善膝关节韧带损伤患者的治疗。

Knee ligament injuries are common, in fact, 1 in 3000 people suffer an injury to their anterior cruciate ligament (ACL) every year. Ligaments are soft biological tissues that connect bones across a joint. Knee ligaments guide joint motion and maintain joint stability by resisting forces that tend to separate the bones of the joint. Some ligaments heal after injury by producing scar tissue that reconnects the torn ligament ends. When ligaments are not able to heal and reconnect the torn ligament ends, surgery is required to reconstruct the injured ligament. In some percentage of patients, injured and reconstructed ligaments do not maintain joint stability and appear to have "stretched out", leaving the patient susceptible to the development of painful osteoarthritis. Unfortunately, the reasons for poor healing of ligaments remain unclear. However, the current proposal questions whether the healing process is able to keep pace with the mechanical demands placed on the ligament. If the mechanical demands exceed the healing potential, damage may accumulate in the ligament as it heals. Normal daily loading for ligament involves sustained and repeated loading; the engineering terms for which are creep and fatigue, respectively. Creep and fatigue loading can cause damage to accumulate in a healing ligament. The exciting innovation of the proposed study is to apply the established engineering principles of continuum damage mechanics to a new problem from the field of biology and medicine, which is poor resolution of ligament healing. Experimental mechanical tests and theoretical mathematical models will be applied to help engineers and orthopaedic surgeons alike understand how damage accumulates in healing ligaments. The intended benefit of this research program is improved treatment of patients with knee ligament injuries.