Glenoid cavity shoulder surgery, illustration. This procedure is one of a number of operations designed to prevent or reduce shoulder dislocations. It involves making changes to the muscles, tendons, cartilage and bones of the shoulder socket (the glenoid), where the head of the humerus articulates with the glenoid cavity of the scapula (shoulder blade). Here, in this view from the front, the covering enclosing the shoulder capsule is opened up and sutured more tightly to the scapula at right.