What to know about avascular necrosis

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Living cells make up the bones in the body, requiring a steady blood supply to stay healthy. In avascular necrosis, an interruption occurs in the blood supply to a part of a bone, causing bone tissue to die. This can lead to bone breakdown and collapse.

Other names for avascular necrosis are:

• osteonecrosis
• aseptic necrosis
• ischemic necrosis of bone

While the condition may affect any bone, it most often occurs at the ends of long bones, such as the upper arm and thigh bones. Less frequently, it affects bones in the:

• hands
• wrists
• feet
• ankles
• elbows

The medical term for the thigh bone is the femur. Its upper part is the head, which has a ball-like shape that is part of the hip’s ball and socket joint. The femoral head is the most common site of avascular necrosis.

Every year in the United States, there are reports of approximately 10,000–20,000 new cases of the condition developing in the femoral head. These contribute to 10% of roughly 250,000 hip replacements per year.

Avascular necrosis of the femoral head most commonly affects males aged between 25 and 50 years old. Diagnosing the condition earlier can substantially affect a person’s outcome.

A disruption in blood supply to a part of a bone causes avascular necrosis. This is because the bone tissue is not getting the oxygen and essential nutrients it needs. If the affected part of the bone is small and does not play a major role in weight bearing, the body may be able to repair the damage.

In most cases, repairing the damage may not be possible, resulting in:

• fracture development
• bone erosion
• eventual bone collapse

When an injury is responsible for the disruption in blood flow, it is probably due to blood vessel damage. In contrast, scientists do not fully understand how factors unrelated to an injury can disrupt blood flow. However, blood clots that block circulation or increased pressure in the bone that constricts blood vessels may play a role.

It is worth noting that some medical discussions on the topic use the terms “risk factors” and “causes” interchangeably. Smoking raises the risk, while the most common risk factors include:

• Serious injury: This interrupts the blood supply to a bone.
• Excessive alcohol use: The connection between alcohol and the condition is unclear, but it may stem from effects, such as blood vessel occlusion or the enlargement of fat cells in the bone marrow.
• High dose steroids: These medications reduce inflammation. They can increase the risk of avascular necrosis, mainly when a person takes a high dose or uses them for a long period. An example drug is prednisone (Rayos).
• Systemic lupus erythematosus: This is an autoimmune condition involving widespread tissue damage from inflammation.

Less common risk factors may include:

• HIV: This is a viral infection.
• Blood disorders: These include sickle cell anemia, a condition that distorts the red blood cells.
• Radiation therapy: Includes treatments of conditions using X-rays or other forms of radiation.
• Organ transplant: This involves the replacement of a diseased organ with a donor organ.
• Bisphosphonates: These medications are for treating bone density loss.
• Decompression disease: Also known as “the bends,” the release of nitrogen gas bubbles that affect blood vessels when a diver swims to the surface of the water too quickly.

Initially, individuals may not have any symptoms of avascular necrosis. However, as the condition progresses, a person may slowly start to experience pain.

The pain may occur particularly in weight-bearing bones.

When the condition affects the hip joint, pain may occur in the groin or, less commonly, in the buttocks.

At first, most people start to feel pain when they bear weight on the affected joint, but later, the joint may feel painful during rest.

As the disease progresses, the following may occur over time:

• stiffening joints
• a loss in the range of motion
• a sudden increase in pain if the end of the bone collapses
• arthritis

Doctors may use a variety of tests to diagnose avascular necrosis, including:

• a medical history
• a physical examination
• imaging tests, including X-rays, MRIs, and CT scans

Healthcare professionals initially use X-rays to rule out any other causes of joint pain. MRIs and CT scans provide clearer images of the bone so that doctors can determine the extent of the bone damage. MRI scans are highly sensitive and are more common in their use, as they can detect signs of avascular necrosis before a person starts experiencing symptoms.

Treatment for avascular necrosis includes nonsurgical and surgical interventions.

The best treatment option for people may vary according to:

• the person’s age
• stage of disease
• what bone is affected
• the extent of the damage to the bone

Nonsurgical treatment can help if avascular necrosis only affects a small area or is in its early stages. Conversely, it is ineffective in people with advanced forms of the condition or when it affects the hip or knee.

It is best to start treatment early before the bone collapses. Some treatment options include:

• Physical therapy, or rehabilitation: This focuses on exercises that improve joint motion and strengthen the muscles around joints. An example exercise may include circular movements of the hip while holding onto something.
• Anti-inflammatory medications: These help reduce symptoms of pain and swelling.
• Using crutches or canes: These can provide support and help relieve pain when walking, particularly if the condition affects weight-bearing bones.

Although these measures can help manage the condition, they typically do not slow the disease’s progression.

Most people eventually need surgery, which involves removing some dead cores of the bone. Options include:

• Core decompression: This is the most common surgery for the condition. It involves drilling shafts into the bone to reduce pressure.
• Osteotomy: This is appropriate for treating small areas of bone damage. It involves repositioning the healthy part of the bone to support the weight-bearing joint.
• Bone graft: Doctors may reserve this procedure for advanced cases. A bone graft may come from another part of an individual’s body, another person, or a synthetic material. It transplants a healthy part of a bone with its blood supply into the part of the bone with dead cells.
• Total joint replacement: This involves replacing a damaged joint with one consisting of ceramics, metal, or plastic. This procedure aims to increase a person’s range of motion and reduce pain.

New therapies that utilize stem cells to treat avascular necrosis of the femoral head can mean that people, especially young individuals — may not require a total hip replacement.

The main methods of preventing avascular necrosis involve addressing the risk factors that are possible to change.

This may include:

• consuming alcohol in moderation
• quitting smoking, if applicable
• discussing alternatives to corticosteroids with a doctor, if a person takes these medications

The outlook is often negative for avascular necrosis, regardless of the type of early treatment someone has.

As the condition advances, an individual experiences:

• debilitation, or weakness
• persistent pain
• destruction of the joint beyond repair

Among people with avascular necrosis without symptoms, 59% later develop symptoms or experience bone collapse.

In those with avascular necrosis in the humeral head, the condition progresses to the point where a hip replacement is necessary for up to 81% of cases. The progression of avascular necrosis in this joint may take several months to 1 year.

Avascular necrosis occurs when bone tissue dies due to a disruption in its blood supply. A range of risk factors, such as a serious injury, may cause or contribute to the disruption.

Once the condition progresses, a person experiences pain, especially in weight-bearing joints.

Most people eventually need surgery, such as a bone graft or total joint replacement. However, the outlook is frequently negative.