Patient/caregiver was instructed regarding essentials of shoulder joint replacement as follows:
- The shoulder joint is mainly a ball and socket joint, in which the ball of the joint is formed by the round head of humerus. The socket is a hollow in the scapula or shoulder blade, which is called glenoid. The head of humerus sitting inside the hollow glenoid adds some stability to the shoulder joint.
- The head of humerus is covered by articular cartilage and has a soft, smooth, and rubbery consistency. The hollow of the glenoid is also lined by the same soft, smooth articular cartilage.
- The smooth and soft articular cartilage lining the glenoid and covering the head of humerus helps with easy sliding of the bones against each other and allows an easy range of motion.
- Also, the articular cartilage helps as a shock absorber and helps to prevent the friction due to rubbing of the bones against each other.
- Shoulder joint replacement is performed in individuals with history of arthritis, such as, osteoarthritis and rheumatoid arthritis. Osteoarthritis is secondary to wear and tear from excessive use. Rheumatoid arthritis is secondary to chronic inflammation and injury. Individuals with serious injuries and accidents involving the shoulder joint could also be recommended for a joint replacement.
- Individuals with arthritis have worn out cartilages due to excessive wear & tear and injury. As the cartilage at the ends of bones is worn out, the bones start rubbing against each other, resulting in friction, chronic inflammation with worsening pain & swelling, and damage to the bones.
- The rotator cuff is a group of muscles and tendons that surround the shoulder joint, keeping the head of humerus firmly in the glenoid cavity. Shoulder replacement is considered in individuals with worn out cartilages, but with intact rotator cuff. It is a surgery involving resurfacing of the ends of the bones forming the shoulder joint. The surgeon typically takes off the bony head of the humerus and the damaged articular cartilages from the shoulder joint.
- The bone ends are then resurfaced using metal and plastic prosthetics. The glenoid socket is redone with plastic prosthetic. A piece of metal with a smooth rounded metal head is fixed into the upper end of humerus.
- The smooth rounded metal head of humerus is made to sit into the plastic surface of glenoid. Now, the metallic humerus head rubs smoothly on the plastic fixed on the glenoid of scapula.
- Once the joint is aligned and the metal & plastic prosthetics are fixed, they could be held in place using a substance called bone cement. Bone cement helps adherence of prosthetics to the natural bone in the human body.
