In-vivo MR Tractography and FEM Study of Human Lower Leg

描述（由申请人提供）：目前的肌肉-骨骼系统模型无法准确预测肌纤维缩短与肌腱-骨骼界面相对偏移之间的关系。一个简单的例子是踝关节处的肌腱-跟骨界面移动了大约30毫米，使比目鱼肌纤维缩短了15毫米。我们提出了多种机械增益系统来放大肌肉纤维偏移，本建议的基本设计是评估这些增益系统，并确定它们是否足以解释肌肉纤维长度变化和踝关节运动之间的差异。第二个目标是了解潜在的力学，特别是在收缩过程中肌肉组织的扭曲。要测试的假设包括：(1)纤维-腱膜界面在等距收缩期间的近端-远端位移部分是由于界面角度的增加以及由于插入和起始腱膜之间距离的缩短。(2)最远端比目鱼纤维-腱膜止点的近端-远端位移将小于跟骨上跟腱止点的线性位移，这是由于肌肉腱-骨骼解剖结构固有的吊索因素。先进的磁共振成像技术，如3特斯拉的扩散张量示踪技术、相对比成像技术、核磁共振兼容的动力测量技术以及有限元建模技术将被结合使用。这尤其适用于PA，它要求“综合了来自技术和生物医学领域多样性的原则”的“多学科研究”被用于“提供新的理解”和“有效地解决生物医学问题”。我们将通过实验研究三头肌表面复合体的几个设计特征，这些特征可以解释当前对肌肉性能描述中的明显矛盾，并生成一个与我们的实验观察一致的模型。我们的目标是更好地预测内在肌肉特性和关节性能。为了检验这些假设，我们将测量的基本变量包括肌肉体积、肌肉表面积、纤维方向、腱膜分离（肌肉厚度）、腱膜尺寸和腱膜的应变特性。在3Dal空间中，这些变量将在系统地改变踝关节位置和肌肉激活水平时进行量化。从NASA/NSBRI过去的资助中，我们在开发这些相对困难的技术方面取得了相当大的成功（详见附录）。开发的模型将有助于更好地了解肌肉-肌腱复合体的设计特征，更好地理解慢性肌肉适应，如废用性萎缩，更好地预测手术治疗的结果，如腱神经切开术、肌腱切除术和肌腱切开术。

DESCRIPTION (provided by applicant): Current models of the musculo-skeletal system fail to accurately predict the relationship between muscle fiber shortening and the relative excursion of the tendino-skeletal interfaces. A simple example of this would be that the tendino-calcaneal interface at the ankle moves approximately 30 mm for a 15 mm soleus muscle fiber shortening. We propose multiple mechanical gain systems to amplify the muscle fiber excursion and the basic design of this proposal is to evaluate these gain systems and determine if they are sufficient to explain the discrepancy between muscle fiber length changes and movement of the ankle. A secondary goal is to understand the underlying mechanics, particularly as it relates to the distortion of muscle tissue during a contraction. The hypotheses to be tested include (1) The proximo-distal displacement of the fiber-aponeurosis interface during an isometric contraction will be due in part to an increase in angle of the interface as well as due to a shortening of the distance between the aponeuroses of insertion and origin, and (2) The proximo-distal displacement of the most distal soleus fiber-aponeurosis of insertion will be less than the linear displacement of the Achilles' tendon insertion point on the calcaneus due to a sling factor that is intrinsic to the musculotendinous-skeletal anatomy. Advanced MR imaging techniques of fiber tracking with Diffusion Tensor Tractography at 3 Tesla, Phase Contrast Imaging, and MRI-compatible dynamometry as well as Finite Element Modeling will be used in combination. This is particularly apt for the PA which asks that a "multidisciplinary research" with an "integration of principles from a diversity of technical and biomedical field" be used to "provide new understanding" and "effectively address a biomedical problem". We will experimentally investigate several design features of the Triceps Surae Complex that could account for apparent paradoxes in current descriptions of muscle performance and generate a model consistent with our experimental observations. Our goal is better prediction of intrinsic muscle properties and joint performance. Essential variables that we will measure to test these hypotheses include muscle volume, muscle surface area, fiber orientation, aponeurosis separation (muscle thickness), aponeurosis dimension and strain properties of aponeurosis. In 3Dal space, these variables will be quantified at systematically varying ankle joint positions and muscle activation levels. From a past grant from NASA/NSBRI, we have had considerable success in developing most of these relatively difficult techniques, (as per publications in Appendix). The developed model will help to gain better insight into the design features of muscle-tendon complex, a better understanding of chronic muscle adaptations such as disuse atrophy and better prediction of outcomes of surgical treatments such as aponeurotomy, tenectomy and tenotomy.