Webb Joshua D, Blemker Silvia S, Delp Scott L
a Department of Mechanical Engineering , Stanford University , Stanford , CA 94305 , USA.
Comput Methods Biomech Biomed Engin. 2014;17(8):829-37. doi: 10.1080/10255842.2012.719605. Epub 2012 Sep 20.
Accurate representation of musculoskeletal geometry is needed to characterise the function of shoulder muscles. Previous models of shoulder muscles have represented muscle geometry as a collection of line segments, making it difficult to account for the large attachment areas, muscle-muscle interactions and complex muscle fibre trajectories typical of shoulder muscles. To better represent shoulder muscle geometry, we developed 3D finite element models of the deltoid and rotator cuff muscles and used the models to examine muscle function. Muscle fibre paths within the muscles were approximated, and moment arms were calculated for two motions: thoracohumeral abduction and internal/external rotation. We found that muscle fibre moment arms varied substantially across each muscle. For example, supraspinatus is considered a weak external rotator, but the 3D model of supraspinatus showed that the anterior fibres provide substantial internal rotation while the posterior fibres act as external rotators. Including the effects of large attachment regions and 3D mechanical interactions of muscle fibres constrains muscle motion, generates more realistic muscle paths and allows deeper analysis of shoulder muscle function.
为了描述肩部肌肉的功能，需要准确呈现肌肉骨骼的几何结构。先前的肩部肌肉模型将肌肉几何结构表示为线段的集合，这使得难以考虑肩部肌肉典型的大附着区域、肌肉与肌肉之间的相互作用以及复杂的肌纤维轨迹。为了更好地呈现肩部肌肉几何结构，我们开发了三角肌和肩袖肌群的三维有限元模型，并使用这些模型来研究肌肉功能。对肌肉内的肌纤维路径进行了近似处理，并针对两种运动计算了力臂：胸肱外展和内/外旋转。我们发现，每条肌肉内的肌纤维力臂差异很大。例如，冈上肌被认为是较弱的外旋肌，但冈上肌的三维模型显示，前部纤维提供大量内旋，而后部纤维则起到外旋肌的作用。纳入大附着区域的影响以及肌纤维的三维力学相互作用会限制肌肉运动，生成更逼真的肌肉路径，并能更深入地分析肩部肌肉功能。
