Patient/caregiver was instructed regarding essentials of reverse 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 any damage to the bones due to friction from chronic use.
- 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.
- Reverse shoulder replacement, as it sounds, is a surgery involving reverse resurfacing of the ends of the bones forming the shoulder joint. In a normal shoulder replacement, you have the ball on the humerus and the socket on the scapula. In a reverse shoulder replacement, you have the ball on the scapula and the socket on the humerus.
- Reverse shoulder replacement is considered in individuals with worn out cartilages at the ends of bones forming the shoulder joint along with a torn and damaged rotator cuff. 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. In a normal shoulder replacement, an intact rotator cuff is needed for longevity of the replaced shoulder. Reverse shoulder replacement surgery is designed for individuals with damaged rotator cuff and the surgery allows the joint to function normally despite the damaged rotator cuff. Reverse shoulder replacement is also considered in individuals with excessive loss of bone on the scapula side, which can make fixing of socket difficult.
- 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 by fixing a piece of metal with a smooth rounder head. A plastic hollow prosthetic is fixed to the upper end of humerus.
- The smooth rounded metal head from scapula is made to sit into the hollow of the plastic prosthetic fixed to the upper end of humerus. Now, the metallic head rubs smoothly on the hollow plastic fixed on the upper end of humerus.
- 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.
