Ihashi K, Matsushita N, Yagi R, Handa Y
Department of Restorative Neuromuscular Surgery and Rehabilitation, Tohoku University Graduate School of Medicine, Sendai, Japan.
J Electromyogr Kinesiol. 1998 Oct;8(5):337-46. doi: 10.1016/s1050-6411(97)00038-2.
The shoulder joint allows three-dimensional movement. In order to analyze the function of the muscles which act on the shoulder joint, three-dimensional movements, including rotation, must be considered. Among muscles participating in the shoulder joint movement, the supraspinatus muscle is known to have abduction and stabilization effects on the shoulder joint. However, the rotational function of the supraspinatus muscle has not been identified, because few studies have been reported on it. This study investigates the rotating function of the supraspinatus muscle using electrical stimulation, magnetic resonance imaging (MRI) and anatomical examination. Electrical stimulation was applied selectively to the supraspinatus muscle of healthy subjects using percutaneous wire electrodes. The electrical stimulation was given at different positions of the shoulder joint. It was found that the electrically induced rotational movements changed their direction depending on the position of the shoulder joint. When the humerus was relatively in internal rotation, internal rotation resulted. When it was in external rotation, external rotation occurred. Regarding the abduction angle of the shoulder joint, external rotation was induced with an increase in the abduction angle, whereas internal rotation occurred when the abduction angle was decreased. By the dissection of cadavers and MRI examination, it was indicated that the relation between the running direction of the supraspinatus muscle and the center of rotation of the humeral head was dependent on the position of the shoulder joint. Those findings supported the results of electrical stimulation of the supraspinatus muscle at various shoulder positions. These results indicate that the bi-directional rotating function of the supraspinatus muscle is characterized by an anatomical relationship between the running direction of the supraspinatus muscle and the center of rotation of the humeral head.
肩关节允许三维运动。为了分析作用于肩关节的肌肉功能，必须考虑包括旋转在内的三维运动。在参与肩关节运动的肌肉中，已知冈上肌对肩关节有外展和稳定作用。然而，冈上肌的旋转功能尚未明确，因为相关研究报道较少。本研究采用电刺激、磁共振成像（MRI）和解剖学检查来探究冈上肌的旋转功能。使用经皮线电极对健康受试者的冈上肌进行选择性电刺激。电刺激在肩关节的不同位置施加。结果发现，电诱导的旋转运动方向取决于肩关节的位置。当肱骨相对处于内旋时，会导致内旋。当处于外旋时，则会发生外旋。关于肩关节的外展角度，外展角度增加时会诱导外旋，而外展角度减小时则会发生内旋。通过尸体解剖和MRI检查表明，冈上肌的走行方向与肱骨头旋转中心之间的关系取决于肩关节的位置。这些发现支持了在不同肩关节位置对冈上肌进行电刺激的结果。这些结果表明，冈上肌的双向旋转功能的特点是冈上肌走行方向与肱骨头旋转中心之间存在解剖学关系。
