Shoulder replacement surgery may be indicated for debilitating pain associated with arthritis of the shoulder. In a shoulder replacement, the arthritic ball and socket are removed and resurfaced with a new metal ball and plastic liner.
In patients with severe rotator cuff tears associated with shoulder arthritis, a "Reverse Shoulder Replacement" may be indicated. In order to improve the biomechanics of the shoulder, the ball and socket get reversed. A new ball is placed where the socket is and a new socket is placed where the worn out hip ball is. This allows other shoulder muscles to control the shoulder movement instead of the torn rotator cuff muscles.
Click link below for shoulder replacement animation:
http://spsdoc.understandsurgery.com/ext/aid_101/animation_tj_all.asp