What are the advantages to the coracoacromial arch? What are the disadvantages?

What will be an ideal response?

ANS:
The advantage of the coracoacromial arch is that the arch checks upward dislocation of the humeral head. The arch also prevents forces from above from traumatizing the soft tissue structures lying between the acromion and the humeral head (primarily the supraspinatus tendon and the subacromial/subdeltoid bursae). The disadvantage of the coracoacromial arch is that the structures that lie in the limited suprahumeral space are likely to be impinged between the humeral head and the osseoligamentous arch. The risk of impingement is increased by sustained elevation of the humerus (e.g., overhead work), by failure of the infraspinatus, teres minor and subscapularis muscles to prevent upward migration of the humeral head during elevation, or by inflammation of the supraspinatus from overuse. Chronic impingement can lead to diminished nutrition and eventual necrosis of the tissues in the suprahumeral space. The supraspinatus and other rotator cuff muscle tendons are particularly vulnerable to such degenerative changes.