The shoulder joint is a ball and socket joint in which the ball portion consists of the proximal humerus in the form of a ball-shaped humeral head and the socket portion consists of the articular glenoid in the form of a depressed scapula. The humeral head (ball) and the articular pelvis (fossa) cooperate to form the joint that allows you to move the shoulder. The shoulder joint is surrounded by articular cartilage, tendons, ligaments, joint capsule, and muscles to provide support and stability, and to allow the shoulder joint to move freely. The mobility of the shoulder joint depends on the proper articulation between the humeral head and the articular glenoid. According to the American Academy of Orthopaedic Surgeons, more than 4 million people in the United States seek medical attention for shoulder problems each year. These shoulder problems range from trauma (e.g., fractures, dislocations) to chronic conditions (e.g., arthritis). Severe arthritis, fractures, and osteonecrosis of the shoulder joint require treatment with a procedure called an artificial shoulder replacement, which uses an artificial shoulder component (prosthesis) to replace the painful joint surface or severely damaged part of the joint, reduce friction in the joint, improve shoulder mobility, and eliminate pain. Prostheses used in artificial shoulder replacement can be divided into total shoulder replacement systems and inverted shoulder prostheses. In a total shoulder replacement system, the ball head of the prosthesis is placed on the stem and the plastic glenoid cup is embedded in the scapula; in a reverse shoulder joint, the ball head of the prosthesis is placed on the scapula and the plastic glenoid cup is embedded in the scapula. The reverse shoulder joint has the ball head placed on the scapula and the plastic glenoid cup embedded in the stem. Total shoulder arthroplasty is indicated for rheumatoid arthritis, osteoarthritis, ischemic necrosis, and fractures of the shoulder, while reverse shoulder arthroplasty is required for large irreparable rotator cuff injuries with loss of rotator cuff function or lack of bony stops, rotator cuff injuries with osteoarthritis, and advanced rheumatoid arthritis.