Causes of avascular necrosis

What is avascular necrosis? Though the medical term is very common, most people are unaware of what is avascular necrosis. Avascular necrosis is a disease where the bone actually dies because of an interruption of blood flow.

When this disintegration takes place in the bone of joints, especially in the hip, knee or the femoral head, it leads to a collapse of the joint in the body. Other names for avascular necrosis are osteonecrosis, aseptic necrosis, ischemic bone necrosis or bone infarction.

Usually when a bone breaks down as part of wear and tear, the body heals itself, gradually replacing new bone with old bone.
But in the case of avascular necrosis, this replacement does not happen. As the bone and joint disintegrate quickly, the body is unable to replace and repair the bone.

One of the essential avascular necrosis causes is loss of blood supply to the joint. The loss of blood can be due to any number of reasons like trauma or injury which results in a loss of blood vessels in that joint. Other causes of avascular necrosis of the knee, hip, femoral head or any bone include excessive intake of alcohol, blood disorders, pancreatitis, radiation and chemotherapy, decompression disease and the Gaucher’s disease. People who drink regularly form fatty substances that block the blood from reaching the joints. Patients who take regular corticosteroids also face reduced blood supply to the joints, causing avascular necrosis.

Corticosteroids are used to treat diseases like lupus or rheumatoid arthritis. Research is still on, on how these steroids actually cause avascular necrosis and how to reduce this risk. Sometimes a trauma like a fracture can damage the blood cells and affect the blood supply. Other risk factors include different radiation and chemotherapy as well as organ transplants like kidney transplants. Other diseases like gout, arthritis, osteoporosis, osteoarthritis, blood disorders like HIV, sickle cell disease, all can lead to avascular necrosis.

The level of disability of the joint depends on how much of the bone is affected due to the reduced blood supply. One of the major avascular necrosis symptoms related to the bone are usually pain in the affected joint. Avascular necrosis of femoral head, knee or the hip causes a lot of pain and is a symptom. The femoral head is actually a very vulnerable joint for avascular necrosis. The pain is not debilitating in the beginning but as the joint gets worse, the pain increases. As the adjoining muscle around the joint collapses, the pain can become unbearable and even limit mobility. Closer physical examination only will determine what causes this pain and whether it is avascular necrosis.

It commonly affects the joints of the hips, shoulders, ankles, upper arm bones and knees. In rare cases, the avascular necrosis can even affect the joints of the jaw. This disease largely affects men but in the case of systemic lupus erythematosus, it affects women too. Children can also get avascular necrosis. Usually adults develop this disease in the thirties to their fifties. But there are instances when even children develop avascular necrosis. Children who have Perthes disease tend to develop avascular necrosis as Perthes disease leads to degeneration of the hip joint due to lowered blood supply. In younger children, post surgery, they seem to recover completely after the treatment of avascular necrosis but in adults and adolescents, it is likely to cause lifelong problems. In case of Perthes combined with avascular necrosis, the older the child, the worse the prognosis.

Diagnosis of avascular necrosis is done with physical examination, diagnostic tests and extensive personal histories. Tests like X Ray, MRI scans, bone scans, computerized tomography or a three-dimensional picture of the bone and even biopsies, all can help determine whether you suffer from avascular necrosis. Avascular necrosis of the hip or any other joint can be treated with medication that stops degeneration of the bone and the joint, if it is treated in time. The aim of any avascular necrosis treatment here is mainly the survival of the affected joint. This is done with the help of medication. Often treatment of avascular necrosis of the knee or the hip is also done by surgically replacing the joint.

Medications are given as the first resort for avascular necrosis. If diagnosed early the doctor might suggest support to remove weight off the affected joint. There are even exercises that be given to improve the joint, postponing surgery. But most patients with avascular necrosis eventually need surgery as the joint degeneration can just be slowed, not stopped. Surgery is used as the last option. For instance, in treatment of the femoral head in avascular necrosis, sometimes a hole is drilled at the neck of the joint, to increase the blood flow to the joint. In case of the femoral joint, almost all patients eventually need a hip replacement.

Before surgically replacing the joint, the doctor might also try other surgical methods. Doctors also try to surgically correct the pressure within the joint, which has usually reduced, as a result of the reduced blood flow. This is called core decompression. This procedure reduces bone and joint disintegration. Another procedure done is osteotomy. This involves reshaping the bone to take stress of the affected joint. This treatment works well with patients who have a small part of affected bone and avascular necrosis that is caught early on. Another procedure includes a bone graft. Sometimes part of the bone is also replaced as a part of the treatment for an affected bone or a joint. Part of this procedure also ensures the increase in blood circulation to the joint, improving the joint’s longevity. Total joint replacement is used as the last surgical option. It is used only when the joint is completely destroyed.

Currently medical research is on to determine if the degeneration of joints can be stopped before the symptoms start showing up. Research in genetics is playing a big role here where clotting genes could determine whether you are susceptible to avascular necrosis. Biological treatment options are also being explored where the body will be able to generate bone and tissue, with the help of recombinant human protein. But these treatments are still in the realm of things that could happen.