During a study of lesions in 150 shoulder joints, observations were made with regard to the abduction phase of shoulder motion which serve to corroborate the teachings of a small group of contemporary anatomists.
1. Abduction of the arm is a complex mechanism, involving the scapulohumeral, the acromioclavicular and the sternoclavicular joint, whereby the scapula moves along the chest wall, the humeral head glides within the glenoid cavity and the clavicle rotates as its lateral end moves dorsalward, the glenoid moving forward and upward. Toward the completion of abduction there is ipsilateral curvature of the dorsolumbar portion of the spine. In the bared specimen these joints demonstrate a range of motion far in excess of that normally required to elevate the arm.
2. Complete abduction can be obtained in the coronal plane only by external rotation of the humerus (Martin1) and in the sagittal plane by internal rotation of
HORWITZ MT. LESIONS OF THE SUPRASPINATUS TENDON AND ASSOCIATED STRUCTURESINVESTIGATION OF COMPARABLE LESIONS IN THE HIP JOINT. Arch Surg. 1939;38(6):990-1003. doi:10.1001/archsurg.1939.01200120013002