Osteoarthritis, or degenerative arthritis, is typically inherited and is the most common reason people need shoulder replacement surgery. Sports specialist Dr. Peter Theut uses a tire and tread analogy to explain how osteoarthritis affects the shoulder. “Tire is the bone; tread is the cartilage. Some people are born with steel-belted radials; some people are born with retread. When you look at them at a young age, they look the same, but they wear quite differently,” he says. “Some people wear down their cartilage prematurely. Eventually, they wear down to bone-on-bone.” Put simply, osteoarthritis is the breakdown of a bone surface. When cartilage is worn away, the joint is no longer cushioned. The bones rub together and eventually spurs, or overgrowth of the joint forms. That is when pain and limitation of motion set in. Osteoarthritis of the shoulder is not as common as it is in the hip or knee, but it might affect more people than we think. “Arthritis pain in the shoulder is typically tolerated better than in the hip or knee. There are probably a fair number of people who just deal with it. We never see them, they never get an x-ray and they’re able to do okay,” says Dr. Theut. But for others, the pain can be severe. According to Dr. Theut, patients who are considered for shoulder replacement surgery typically have debilitating arthritis, and are unresponsive to conservative treatments such as anti-inflammatory medications, steroid injections and physical therapy. “Like most joint replacements, the shoulder replacement is designed to improve function and motion. If conservative treatment options are no longer giving the patient any benefit, then they may be considered for surgery.”

Types of shoulder replacement surgery Depending on the state of the arthritic, or in some cases injured, joint, there are three types of shoulder replacement surgery, also called shoulder arthroplasty.

Total shoulder – As the most common type of shoulder replacement surgery, the total shoulder involves replacing the arthritic humeral head (a.k.a. the ball) and also replacing the glenoid side of the joint (a.k.a. the socket). Joint specialist Dr. Robert DeMaagd explains, “We take off the arthritic ball and put in a steel ball. On the socket side, we resurface and replace with a polyethylene or plastic socket.” As a general rule, the total shoulder addresses “normal wear and tear of the ball and socket,” he says.

Hemiarthroplasty – As the name implies, a hemiarthroplasty is half of a total shoulder where only the ball is replaced, not the socket. This type of surgery, says Dr. DeMaagd, is not as common. “About the only two circumstances for a hemiarthroplasty are if there’s a fracture or if there’s a disease present, called avascular necrosis. This is where the bone essentially dies, the ball collapses and the socket was uninvolved,” he says. “Hemiarthroplasties are performed much less frequently today because of the better results of the total shoulder.”

Reverse total shoulder – In a reverse total, or reverse shoulder, the components are switched: The ball prosthetic goes on the glenoid side and the socket goes on the humeral side. Developed in the last five years, the reverse shoulder replacement is most commonly performed on patients with rotator cuff arthropathy — a problem that was untreatable before this procedure was developed. Rotator cuff arthropathy is when “there’s arthritis in the shoulder and there’s also a non-repairable rotator cuff tear,” says Dr. DeMaagd. “The tear comes first and the arthritis develops later because of the altered mechanics of the shoulder.” With a chronically injured rotator cuff, a total shoulder surgery could potentially lead to instability problems. Dr. Theut explains, “The reverse provides a more constrained prothesis that allows the deltoid muscle to substitute for place of the deficient rotator cuff.” After each of these procedures, patients stay a couple of days in the hospital and a few weeks in a sling. Then, as is common after any joint surgery, physical therapy plays a huge role in the recovery process. After about eight weeks most people are moving again, with much less pain. With continued therapy, “the patient will continue to get better and stronger over the next six months,” says Dr. DeMaagd.