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Avascular necrosis AVN of the ShoulderAnatomy of the shoulderAnatomy of the shoulder

The shoulder is the second most common joint site for AVN. The Femoral head (hip) is the most common site.

Anatomy of the shoulder

The shoulder is one of the most diverse joints in the human body. It permits the arm to be rotated, elevated, and extended both forward and backward.

A non weight bearing joint, consists of three bones: upper arm bone (humerus), shoulder blade (scapula), and the collarbone (clavicle). The shoulder is a ball-and-socket joint: The ball (or head) of the upper arm bone fits into a shallow socket in the shoulder blade. This socket is called the glenoid.

The surfaces of the bones where they join 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 the remaining surfaces inside the shoulder joint. In a healthy shoulder, this membrane makes a small amount of synovial fluid that lubricates the cartilage and almost eliminates any friction in the 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.

What happens when AVN strikes

All of the blood supply comes into the ball that forms the shoulder joint with the shoulder blade. If this blood supply is damaged, there is no backup. Damage to the blood supply can cause death of the bone that makes up the ball portion of the humerus. Once this occurs, the bone is no longer able to maintain itself.

Living bone is always changing. To maintain a bone's strength, bone cells are constantly repairing the wear and tear that affects the bone tissue. If this process stops the bone can begin to weaken, just like rust can affect the metal structure of a bridge. Eventually, just like a rusty bridge, the bone structure begins to collapse.

When AVN occurs in the shoulder joint, the top of the humerus head (the ball portion) collapses and begins to flatten. This occurs because this is where most of the weight is concentrated. The flattening creates a situation where the ball no longer fits perfectly inside the socket.

Shoulder AVN can also present itself with painful clicks in the joint.

Treatments

Goals

Preserve shoulder function, including strength.

Relieve symptoms.

Halt the progression of the disease.

Decrease symptoms.

Decision for surgical intervention using x-rays, MRI scans, clinical and physical symptoms.

Treatments

Medication to reduce pain.

Reduction of risk factors including avoiding overhead activities.

Core decompressions, for stages 1, 2 and 3. Varying success rates, between 40 and 90%.

Re-surfacing.

Arthroplasty - Prosthetic replacement of affected joint., for stages 3, 4 and 5.