Biomechanical study of the shoulder complex

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The shoulder complex is composed of the scapula, clavicle and humerus. shoulder motion is attained by cooperation of these elements. In order to analyse the shoulder complex mechanism, we carried out following experiments.1)Measurement of motion of the scapula and humerus and EMGUsing a magnetic sensor system(3 SPACE). we measured three dimensional motion of the scapula and humerus in elevation in the sagittal, scapular and frontal plane.We measured Euler angles of the scapula(scapulothoracic angle)and humerus and excursion of the scapula with respect to the reference coordinte attached to the trunk. And we calculated relative Euler angles between the scapula and humerus(gleno humeral angle).The ratio of glenohumeral to scapulothoracic angle during elevation was not constant as reported so far. Instead this ratio varied considerably. Motion pattern of abduction was different from that of other elevation. The abduction proved to be difficult motion from a viewpoint of biomechanics. In accordance with this, ranges of abduction of abnormal shoulders were considerably small.2)Experiment of pitchingUsing 3-D angles of the humerus with respect to the trunk, it was possible to discriminate four phases of pitching. Motion pattern of skilled pitching was markedly different from that of unskilled pitching, especially in the rotation of the humerus and electromyographies.3)Experiment with the shoulders of cadaversFrom experiments of maximum circumduction of cadaver specimens, it was found that there exists linear relationship between the range of motion and the rotation of the humerus. This means restriction of rotation of the humerus causes decrease of the range of motion.