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Avascular necrosis (AVN): Bone Disease

What is avascular necrosis?

Avascular necrosis (AVN) is a bone disease that occurs by temporary or permanent loss of blood supply to one or more bones. Blood nourishes the bone tissue with minerals and oxygen. In the absence of adequate supply of blood, the bone tissue will die and bone will collapse. It is also known as osteonecrosis, aseptic necrosis and ischemic necrosis. The extent of disability is determined by what part of the bone is affected; the amount of area involved and how well the old bone is replaced. If the affected bone is close to the joint, the entire joint surface may disintegrate, making movement impossible. In patients of avascular necrosis, the usual bone healing process becomes ineffective and the bone tissues break down faster than the body can repair them.

Which areas are affected?

Thigh bone is the most commonly affected apart from other areas like upper arm bone, knees, shoulders and ankles.

What are the causes and risk factors of avascular necrosis?

It is still not clear what exactly impairs the blood supply to the bone but following are considered to be some of the potential causes of Avascular necrosis:

  1. Injury like fracture, dislocation or some other joint injury. Studies suggest hip dislocation and hip fractures are major risk factors for avascular necrosis.
  2. Excessive and long-term intake of corticosteroid medications which are generally used to treat inflammatory diseases like lupus, rheumatoid arthritis, severe asthma and inflammatory bowel disease.
  3. Excessive drinking of alcohol which develops fatty substances on the walls of blood vessels, thus decreasing the blood supply to the bones.
  4. Other risk factors include radiation therapy, chemotherapy, kidney transplantation and other medical conditions like cancer, systemic lupus erythematosus (SLE), HIV infection, osteoporosis and osteoarthritis.

Who is likely to develop avascular necrosis?

Avascular necrosis can affect people of any age, from children to elderly but it is more common in those between the ages of 20 and 50.

What are the symptoms of avascular necrosis?

No noticeable symptoms in the initial stages. As the disease progresses, most people experience joint pain, especially when they put weight on the affected joint. Slowly the pain becomes permanent and occurs also when one is resting. It could be a mild or severe pain. Mobility becomes restricted. The disease progresses slowly typically the period between the appearance of first symptom to loss of joint function ranges from several months to more than a year.

How is avascular necrosis diagnosed?

Early diagnosis is the key. Doctor will first perform physical examination and then inquire about the patient’s medical history. Doctors may ask for one or more of the following bone imaging tests like x-ray, MRI and CT scan or biopsy to diagnose how far the avascular necrosis has progressed.

How is avascular necrosis treated?

The treatment of avascular necrosis is aimed at reducing pain, improving function of the affected joint and controlling the progression of bone damage. The treatment of avascular necrosis is chosen depending on the age of the patient, location and extent of bone damage, and causes of the disease. Treatment options include

Non-surgical methods like medications, crutches, electrical stimulation (to induce bone growth) and range-of-motion exercises

Surgical options include:

  1. Bone grafts which involve replacing the damaged bone with a piece of healthy bone from another part of body.
  2. Osteotomy in which the damaged bone is cut and realigned to reduce the stress on the joint.
  3. Total joint replacement involves replacing the damaged joint with a synthetic one.
  4. Core decompression, a procedure in which the insides of the bone is removed to relieve pressure.
  5. Vascularised bone graft involves using the patient’s own tissue to rebuild damaged hip joints.