We investigated the shape and development of the human shoulder from shoulder anatomy of Macaca.
We examined (1)location and shape of the acromion (2) anatomical investigation of the rotator cuff insertion to the humerus head (3) The presence of the coracoacromial ligament (4) shape of the supraglenoid tubercle, in 4 cadaveric shoulder of Macaca Mulatta.
The following results were found (1)The acromion of apes was smaller than that of humans. The acromion did not cover up most of the humerus head. (2) The humeral head had individually the rotator cuff insertion part to subscapularis, supraspinatus, the infraspinatus tendon, and the overlapped point with each other was not found. Greater and lesser tubercle size were approximately similar, and the long head of the biceps tendon was located in the center. Also, the teres minor muscle tendon was not present. (3) The acromial position is located on the back of the rib cage rather than human. The coracoacromial ligament was not present. (4) The supraglenoid tubercle was noticeably concave from cranial to the caudal,with the craninal portion jutting forward to overhang.It was suggested that an infraspinatus muscle tendon was an important muscle in a rotator cuff and the coracoacromial ligament occurred as an antero-superior supporting tissue of the shoulder.
