Avascular Necrosis (Osteonecrosis) – Symptoms, Causes And Treatment

What is avascular necrosis? 

Avascular necrosis (AVN) is a condition in which the death of bone tissue occurs due to the loss of blood supply. It is also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis. If AVN is not treated, the bone may collapse. This condition primarily affects the hips and other areas such as the shoulder, knees, and ankles. A dislocated joint or broken bone can interrupt the flow of blood to a section of bone. Avascular necrosis is also linked to long-term use of excessive alcohol intake and high-dose steroid medications.

What are the symptoms of AVN? 

Apart from affecting the hips, AVN can also affect the knee. AVN can affect  bones in other areas such as: 

• Shoulder 
• Wrist 
• Ankle 
• Hands 
• Feet 

Though AVN does not cause any symptoms in the beginning, as the blood cells die, the effect of the disease progresses and the following symptoms occur: 

• Pain in the affected joint limiting movement 
• Groin pain can be a symptom when there is AVN of the hip 
• Putting your weight on the hip or knee can cause pain 
• As the disease worsens, you might feel the pain even when you’re lying down 

Some people develop avascular necrosis bilaterally (on both sides), such as in both hips or in both knees.

The intensity of pain increases due to the tiny breaks in the bone. This condition is called microfracture. Eventually, this eventually causes the bone to collapse and the joint to break down, which can also trigger the development of arthritis. 

What are the causes and risk factors of AVN? 

The main cause of Avascular necrosis is when the flow of blood to bone tissue is stopped or slowed down.  

Reduced blood supply can be caused by:

• Bone trauma and joint: An injury like a dislocated joint may damage near blood vessels. Cancer treatments involving radiation can also weaken the bone and harm your blood vessels
• Fatty deposits in blood vessels: The lipids (fat) can block the small blood vessels, thus reducing the blood flow that feeds your bones
• Certain diseases. Medical conditions like Gaucher’s disease and sickle cell anemia can also lead to diminished blood flow to the bone

For about 25 per cent of individuals with avascular necrosis, the cause of interrupted blood flow is unknown

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The possible risk factors for AVN are: 

• Smoking 
• Heavy alcohol consumption 
• Consuming high doses of corticosteroids 
• Childhood diseases like Legg-Calve Perthes disease 

Sometimes, the reason for the lack of blood flow to the bone is not clearly known. 

Other common causes of AVN are: 

• Decompression sickness and Caisson disease – This condition is caused by a release of nitrogen into the bloodstream. 
• Chemotherapy 
• High cholesterol and triglycerides 
• Gaucher’s disease 
• HIV infection 
• Pancreatitis 
• Organ transplants like kidney transplant 
• Sickle cell anemia 

Men are more prone to Avascular necrosis than women. It also affects more people between the age of 30 and 60, though it can occur at any age .

How can AVN be diagnosed? 

When an individual has bone pain that is localized to a small area, the surgeon suggests the following imaging tests. 

• X-ray – The early stages of AVN shows a normal X-ray image. If the individual has AVN, then the doctor suggests X-rays have a track of the progression. 
• MRI scan – This scan can help the surgeon identify AVN in the early stages even before experiencing any symptoms. MRI scan also gives a clear picture of the affected bone. 
• Nuclear bone scan – If the X-rays are normal and there are no risk factors, the surgeon may suggest a nuclear bone scan. An IV injection of a harmless radioactive substance is required before the scan. This allows the doctor to have a clear picture of the bones. This scan is also called bone scintigraphy. 

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What is the treatment for AVN? 

The treatment for AVN depends on the following factors: 

• Age 
• Cause of Avascular necrosis 
• Bones damaged 
• The amount of damage caused 

As the disease progress, the treatment changes from non-surgical to surgical care. The major goals of the treatment are: 

• Treat the cause of AVN 
• Reduce the pain 
• Making use of affected joint 

The non-surgical treatments included for AVN are as follows: 

• Pain medications like nonsteroidal anti-inflammatory drugs 
• The risk of microfractures is reduced by limiting activities like walking that exerts pressure on the affected joint. 
• Range-of-motion exercises that keep the joint in action 
• Improvement of blood flow using cholesterol-lowering medicines 

What happens when Avascular necrosis does not respond to treatment or keeps worsening? 

The patient requires surgery if the pain gets worse. Surgery also helps to prevent the bones from collapsing and preserves the joint. The surgical options are as follows: 

Surgical and other procedures

Because many people do not develop symptoms until avascular necrosis is fairly advanced, your doctor may recommend surgery. The options are:

Core decompression: The surgeon operates to remove part of the inner layer of your bone, besides reducing the pain

Bone transplant (graft): This operation can help you strengthen the area of your bone affected by avascular necrosis. A graft is a portion of healthy bone taken out from another part of the body

Bone reshaping (osteotomy): A wedge of the bone is removed below or above a weight-bearing joint, to help shift the weight off your damaged bone. Bone reshaping many enable you to postpone the joint replacement.

Core decompression: A surgeon drills one or more holes in the affected joint to remove a core of bone. The goal is to relieve joint strain and the extra space within the bone stimulates the production of new blood vessels and healthy bone tissue. This procedure may be able to prevent bone collapse and arthritis if Avascular necrosis is detected early enough. Decompression of the core can help prevent a hip replacement later on. 

A walker or crutches is needed while the bone heals and its blood supply is replenished. Although recovery can take several months, many people who undergo this operation experience total pain relief. 

Bone grafting: Bone grafting is frequently performed in conjunction with core decompression. Surgeon grafts (transplants) a small piece of healthy bone from another region of your body to replace the dead bone. The surgeon can also employ a donor or synthetic bone graft. This procedure promotes blood flow and strengthens the joint. 

Osteotomy: A surgeon removes the dead bone while simultaneously repositioning or reshaping the remaining healthy bone. This relieves tension on the joint and improves its support. The recovery from this procedure can take many months of reduced activity. 

Joint replacement: If the diseased bone has collapsed or other treatments are not helping, you may need an operation to replace the damaged portion of the joint with metal or plastic parts.

Regenerative medicine treatment: Bone marrow aspirate and concentration is a newer procedure that may be suitable for early-stage avascular necrosis of the hip. In this procedure, stem cells are harvested from your bone marrow. During surgery, a core of a dead hip bone is removed and stem cells inserted in its place, possibly allowing for the growth of new bone. 

Here are a few preventive tips to follow for AVN: 

• Avoid drinking alcohol 
• Avoid smoking 
• Keep cholesterol levels low 
• Monitor steroid use: Ensure your doctor knows about your past or present use of high-dose steroids.