Shoulder Replacement

Anatomy

Your shoulder is made up of three bones: your upper arm bone (humerus), your shoulder blade (scapula), and your collarbone (clavicle). The shoulder is a ball-and-socket joint: The ball, or head, of your upper arm bone fits into a shallow socket in your shoulder blade. This socket is called the glenoid.

The bones of a healthy shoulder joint.

The surfaces of the bones where they touch are covered with articular cartilage, a smooth substance that protects the bones and enables them to move easily. A thin, smooth tissue called synovial membrane covers all remaining surfaces inside the shoulder joint. In a healthy shoulder, this membrane makes a small amount of fluid that lubricates the cartilage and eliminates almost any friction in your shoulder.

The muscles and tendons that surround the shoulder provide stability and support.

All of these structures allow the shoulder to rotate through a greater range of motion than any other joint in the body.

Description

Shoulder joint replacement.

© 2011, Thinkstock

In shoulder replacement surgery, the damaged parts of the shoulder are removed and replaced with artificial components, called a prosthesis.

The treatment options are either replacement of just the head of the humerus bone (ball), or replacement of both the ball and the socket (glenoid).

Cause

Several conditions can cause shoulder pain and disability, and lead patients to consider shoulder joint replacement surgery.

Osteoarthritis (Degenerative Joint Disease)

Osteoarthritis is an age-related wear-and-tear type of arthritis. It usually occurs in people 50 years of age and older, but may occur in younger people, too. The cartilage that cushions the bones of the shoulder softens and wears away. The bones then rub against one another. Over time, the shoulder joint slowly becomes stiff and painful.

Unfortunately, there is no way to prevent the development of osteoarthritis. It is a common reason people have shoulder replacement surgery.

Osteoarthritis of the shoulder. As the cartilage that covers the ends of the bones wears away, it can result in bone rubbing on bone and produce painful bone spurs.

Rheumatoid Arthritis

This is a disease in which the synovial membrane that surrounds the joint becomes inflamed and thickened. This chronic inflammation can damage the cartilage and eventually cause cartilage loss, pain, and stiffness. Rheumatoid arthritis is the most common form of a group of disorders termed inflammatory arthritis.

Post-traumatic Arthritis

This can follow a serious shoulder injury. Fractures of the bones that make up the shoulder or tears of the shoulder tendons or ligaments may damage the articular cartilage over time. This causes shoulder pain and limits shoulder function.

Rotator Cuff Tear Arthropathy

A patient with a very large, long-standing rotator cuff tear may develop cuff tear arthropathy. In this condition, the changes in the shoulder joint due to the rotator cuff tear may lead to arthritis and destruction of the joint cartilage.

Avascular Necrosis (Osteonecrosis)

Avascular necrosis, or osteonecrosis, is a painful condition that occurs when the blood supply to the bone is disrupted. Because bone cells die without a blood supply, osteonecrosis can ultimately cause destruction of the shoulder joint and lead to arthritis. Chronic steroid use, deep sea diving, severe fracture of the shoulder, sickle cell disease, and heavy alcohol use are all risk factors for avascular necrosis.

Severe Fractures

A severe fracture of the shoulder is another common reason people have shoulder replacements. When the head of the upper arm bone is shattered, it may be very difficult for a doctor to put the pieces of bone back in place. In addition, the blood supply to the bone pieces can be interrupted. In this case, a surgeon may recommend a shoulder replacement. Older patients with osteoporosis are most at risk for severe shoulder fractures.

Failed Previous Shoulder Replacement Surgery

Although uncommon, some shoulder replacements fail, most often because of implant loosening, wear, infection, and dislocation. When this occurs, a second joint replacement surgery — called a revision surgery — may be necessary.

Is Shoulder Joint Replacement for You?

The decision to have shoulder replacement surgery should be a cooperative one between you, your family, your family physician, and your orthopaedic surgeon.

There are several reasons why your doctor may recommend shoulder replacement surgery. People who benefit from surgery often have:

• Severe shoulder pain that interferes with everyday activities, such as reaching into a cabinet, dressing, toileting, and washing.
• Moderate to severe pain while resting. This pain may be severe enough to prevent a good night's sleep.
• Loss of motion and/or weakness in the shoulder.
• Failure to substantially improve with other treatments such as anti-inflammatory medications, cortisone injections, and/or physical therapy.

Orthopaedic Evaluation

Your family physician may refer you to an orthopaedic surgeon for a thorough evaluation to determine if you can benefit from this surgery.

An evaluation with an orthopaedic surgeon consists of several components:

• A medical history. Your orthopaedic surgeon will gather information about your general health and ask you about the extent of your shoulder pain and your ability to function.
• A physical examination. This will assess shoulder motion, stability, and strength.
• X-rays. X-rays help to determine the extent of damage in your shoulder. They can show loss of the normal joint space between bones, flattening or irregularity in the shape of the bone, bone spurs, and loose pieces of cartilage or bone that may be floating inside the joint.
• Other tests. Occasionally, your doctor may order blood tests, a computed tomography (CT) scan, a magnetic resonance imaging (MRI) scan, or a bone scan to determine the condition of the bone and soft tissues of your shoulder.

Your orthopaedic surgeon will review the results of your evaluation with you and discuss whether shoulder joint replacement is the best method to relieve your pain and improve your function. Other treatment options — including medications, injections, physical therapy, or other types of surgery — will also be discussed and considered.

(Left) An X-ray of a healthy shoulder joint. (Right) Osteoarthritis of the shoulder. Note the decreased joint space (arrow).

Failed Previous Shoulder Replacement Surgery

Shoulder replacement surgery is highly technical. It should be performed by a surgical team with experience in this procedure.

There are different types of shoulder replacements. Your surgeon will evaluate your situation carefully before making any decisions. They will discuss with you which type of replacement will best meet your health needs. Do not hesitate to ask which type of implant will be used in your situation, and why that choice is right for you.

Total Shoulder Replacement

The standard total shoulder replacement involves replacing the arthritic joint surfaces with a highly polished metal ball attached to a stem, and a plastic socket.

A total shoulder joint replacement.

These components come in various sizes. They may be either cemented or press fit into the bone. If the bone is of good quality, your surgeon may choose to use a non-cemented (press-fit) humeral component. If the bone is soft, the humeral component may be implanted with bone cement. In most cases, an all-plastic glenoid (socket) component is implanted with bone cement.

Implantation of a glenoid component is not advised if:

• The glenoid has good cartilage
• The glenoid bone is severely deficient
• The rotator cuff tendons are irreparably torn

Patients with bone-on-bone osteoarthritis and intact rotator cuff tendons are generally good candidates for conventional total shoulder replacement.

These X-rays were taken before and after total shoulder replacement surgery for osteoarthritis.

Stemmed Hemiarthroplasty

Depending on the condition of your shoulder, your surgeon may replace only the ball. This procedure is called a hemiarthroplasty. In a traditional hemiarthroplasty, the surgeon replaces the head of the humerus with a metal ball and stem, similar to the component used in a total shoulder replacement. This is called a stemmed hemiarthroplasty.

Some surgeons recommend hemiarthroplasty when the humeral head is severely fractured but the socket is normal. Other indications for a hemiarthroplasty include:

• Arthritis that involves only the head of the humerus, with a glenoid that has a healthy and intact cartilage surface
• Shoulders with severely weakened bone in the glenoid
• Some shoulders with severely torn rotator cuff tendons and arthritis

Sometimes, surgeons make the decision between a total shoulder replacement and a hemiarthroplasty in the operating room at the time of the surgery.

Studies show that patients with osteoarthritis get better pain relief from total shoulder arthroplasty than from hemiarthroplasty.

Resurfacing Hemiarthroplasty