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

描述(申请人提供)：目前的肌肉-骨骼系统模型不能准确地预测肌肉纤维缩短和肌腱-骨骼界面的相对偏移之间的关系。一个简单的例子是，脚踝处的跟腱-跟骨界面移动约30 mm，比目鱼肌纤维缩短15 mm。我们提出了多个机械增益系统来放大肌肉纤维的漂移，该方案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脚踝运动之间的差异。第二个目标是了解潜在的机制，特别是当它与肌肉组织在收缩过程中的扭曲有关时。需要检验的假设包括：(1)在等长收缩过程中，纤维-腱膜界面的近端-远端移位部分是由于界面角度的增加，以及由于起始端和起始端之间的距离缩短，以及(2)由于肌腱-骨骼解剖固有的吊带因素，插入的比目鱼肌纤维-腱膜最远端的近端-远端移位将小于跟骨上跟腱附着点的线性移位。先进的磁共振成像技术，包括3特斯拉的扩散张量纤维束成像技术、相位对比成像技术、与MRI兼容的测力技术以及有限元建模技术将被结合使用。这尤其适用于PA，它要求使用“多学科研究”，“综合各种技术和生物医学领域的原理”，以“提供新的理解”，并“有效地解决生物医学问题”。我们将通过实验研究三头肌Surae复合体的几个设计特征，这些特征可以解释当前肌肉性能描述中的明显悖论，并生成与我们的实验观察相一致的模型。我们的目标是更好地预测内在肌肉特性和关节性能。我们将测量的基本变量包括肌肉体积、肌肉表面积、纤维取向、腱膜分离(肌肉厚度)、腱膜尺寸和腱膜的应变特性。在3Dal空间，这些变量将在系统变化的踝关节位置和肌肉激活水平下进行量化。根据NASA/NSBRI过去的一笔赠款，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(根据附录中的出版物)。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，更好地了解慢性肌肉适应，如废用性萎缩，以及更好地预测手术治疗的结果，如腱膜切断术、肌腱切断术和肌腱切断术。

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.