Anterior stability of the glenohumeral joint

Abstract

This study defines the interaction of the rotator cuff musculature and the glenohumeral ligaments in provid ing anterior stability to the glenohumeral joint. Eight cadaveric shoulders were studied using a testing frame that individually simulated the forces of the subscapu laris, the supraspinatus, and the infraspinatus/teres minor musculature. The application of these forces abducted the humerus to approximately 90°. The cock ing phase of throwing was then simulated through the use of an Instron. With random variation of the rotator cuff forces, we investigated the effects that each force had on the rotation of the humerus and the strain of the inferior glenohumeral ligament. Our results demon strate that the infraspinatus/teres minor muscle group was the most effective in controlling external rotation of the humerus and in reducing ligamentous strain. These observations are pertinent in the treatment of anterior instability syndromes of the shoulder.