Bone is a living tissue that requires blood supply, any interruptions in the supply of blood to a bone tissue leads to the death of the bone. This condition / state of the bone is termed as 'Avascular Necrosis' (AVN). It is otherwise called as Osteonecrosis, aseptic necrosis or ischemic bone necrosis. The blood supply or flow to a bone tissue is stopped or interrupted if the bone is fractured or the joint is dislocated. Avascular necrosis mostly occurs in the hip, shoulder, knee and ankle joints.
Causes of Avascular Necrosis:
- • Dislocation or fracture of the bone:This type of injury leads to stoppage of blood supply to bone causing trauma related avascular necrosis. The most common site of AVN is hip joint which involves the femur (thigh bone) which is the longest bone in the human body.
- • Excess intake of alcohol:may cause fatty substances to build in the blood vessels and reduce the blood supply to the bone. This makes the bone weak and in long run leads to collapse of the bone.
- • Chronic usage of corticosteroid:Long term usage of these drugs may interfere with body's ability to break down fats and fatty substances which get collected in the blood vessels. This makes them narrower and reduce the amount of blood supply to the bone.
- • Blood clotting, damage to arteries
- • Chemotherapy or Radiation therapy
- • Sickle cell disease
- • Autoimmune diseases
- • Metabolic disorder
- • HIV infection
Symptoms of Avascular Necrosis:
In the early stages of the AVN, we cannot find noticeable symptoms, but when it progresses it becomes painful. When the patient puts pressure on the affected joint or bone, he/she may experience the pain. The patient may experience severe pain that interferes with his ability to use his joint, if the disease progresses and the bone and the surrounding joint collapse. The time gap between the first symptoms and bone collapse would be several months to more than a year.
In this disease the patient often complains of pain in the groin or in front of the thigh. Pain is present at all times, but increases on pressure or exertion.
X-Rays may be normal in early stages but, if suspicion is strong, a Bone Scan may be done. In later stages, there may be diffuse Osteosclerosis (abnormal hardening of the bone and elevation of bone density) of the head of femur (common site), but the shape of the head may be maintained.
In advanced stages, the head collapses. Eventually changes of secondary osteoarthritis become apparent. MRI Scan is the best modality for early diagnosis of Avascular Necrosis.
Treatment for Avascular Necrosis
In early stages, diagnosis is often missed as there are no X-Ray findings. The treatment for AVN includes improving the function of the affected joint, stopping the progression of bone damage and reducing the pain. The best treatment for AVN would depend on the following factors: