PDF(Pubmed)
Abstract：
Computational models of musculoskeletal systems are essential tools for understanding how muscles, tendons, bones, and actuation signals generate motion. In particular, the OpenSim family of models has facilitated a wide range of studies on diverse human motions, clinical studies of gait, and even non-human locomotion. However, biological structures with many joints, such as fingers, necks, tails, and spines, have been a longstanding challenge to the OpenSim modeling community, especially because these structures comprise numerous bones and are frequently actuated by extrinsic muscles that span multiple joints-often more than three-and act through a complex network of branching tendons. Existing model building software, typically optimized for limb structures, makes it difficult to build OpenSim models that accurately reflect these intricacies. Here, we introduce ArborSim, customized software that efficiently creates musculoskeletal models of highly jointed structures and can build branched muscle-tendon architectures. We used ArborSim to construct toy models of articulated structures to determine which morphological features make a structure most sensitive to branching. By comparing the joint kinematics of models constructed with branched and parallel muscle-tendon units, we found that among various parameters-the number of tendon branches, the number of joints between branches, and the ratio of muscle fiber length to muscle tendon unit length-the number of tendon branches and the number of joints between branches are most sensitive to branching modeling method. Notably, the differences between these models showed no predictable pattern with increased complexity. As the proportion of muscle increased, the kinematic differences between branched and parallel models units also increased. Our findings suggest that stress and strain interactions between distal tendon branches and proximal tendon and muscle greatly affect the overall kinematics of a musculoskeletal system. By incorporating complex muscle-tendon branching into OpenSim models using ArborSim, we can gain deeper insight into the interactions between the axial and appendicular skeleton, model the evolution and function of diverse animal tails, and understand the mechanics of more complex motions and tasks.
摘要：
肌肉骨骼系统的计算模型是了解肌肉，肌腱,骨头,和驱动信号产生运动。特别是,OpenSim系列模型促进了对各种人类运动的广泛研究，步态的临床研究，甚至是非人类运动。然而,有许多关节的生物结构，比如手指,脖子,尾巴,和刺，对OpenSim建模社区来说是一个长期的挑战，特别是因为这些结构包括许多骨骼，并且经常由跨多个关节的外部肌肉驱动，通常超过三个关节，并通过复杂的分支肌腱网络起作用。现有的模型构建软件，通常针对肢体结构进行优化，使得难以构建能够准确反映这些复杂性的OpenSim模型。这里,我们介绍ArborSim,定制软件，有效地创建高度关节结构的肌肉骨骼模型，并可以建立分支的肌肉肌腱结构。我们使用ArborSim构建了铰接结构的玩具模型，以确定哪些形态特征使结构对分支最敏感。通过比较用分支和平行的肌肉肌腱单元构建的模型的关节运动学，我们发现在各种参数中——肌腱分支的数量，分支之间的关节数量，肌纤维长度与肌腱单位长度之比-肌腱分支数和分支之间的关节数对分支建模方法最敏感。值得注意的是,这些模型之间的差异表明，随着复杂性的增加，没有可预测的模式。随着肌肉比例的增加，分支和并行模型单元之间的运动学差异也增加了。我们的发现表明，远端肌腱分支与近端肌腱和肌肉之间的应力和应变相互作用极大地影响了肌肉骨骼系统的整体运动学。通过使用ArborSim将复杂的肌肉肌腱分支合并到OpenSim模型中，我们可以更深入地了解轴向和附肢骨骼之间的相互作用，模拟不同动物尾巴的进化和功能，了解更复杂的动作和任务的机制。
