[Analysis of three-dimensional motion of the scapula and the glenohumeral joint]

Three dimensional motion of the scapula and the glenohumeral joint was measured and analysed during flexion, elevation in the scapular plane, and abduction using a three space tracker system. The downward tilting angle of the glenoid cavity was at an angle of -20 degrees during motion. The medially tilting angle of the glenoid cavity changed in a different manner in a different plane of elevation. The angle of elevation of the glenoid cavity changed from -12.6 degrees to 27 degrees in all planes. Elevation of the glenoid cavity and movement of the scapula in parallel were analyzed. During flexion the glenoid cavity faced the plane of flexion and stabilized the glenohumeral joint. During abduction the glenoid cavity moved as though slipping off from the glenohumeral joint. The total of the angles of elevation of the glenoid cavity and the glenohumeral joint did not always equal the angle of elevation of the arm.