Best diagnostic modality to diagnose avascular necrosis is: March 2007
Ans. A: MRI Scan Avascular necrosis/ osteonecrosis/ aseptic (bone) necrosis/ ischemic bone necrosis is a disease resulting from the temporary or permanent loss of the blood supply to the bones. Without blood, the bone tissue dies and causes the bone to collapse. There are many causes of avascular necrosis such as: Alcoholism Excessive steroid use Post trauma Caisson disease (decompression sickness) Vascular compression Vasculitis Thrombosis Damage from radiation Bisphosphonates (paicularly the mandible) Sickle cell anaemia Gaucher's Disease Idiopathic (no cause is found). Rheumatoid ahritis and lupus are also common causes of AVN. Avascular necrosis most commonly affects the head of femur. Other common sites include the talus, scaphoid and the jaw. Avascular necrosis usually affects people between 30 and 50 years of age. When it occurs in children at the femoral head, it is known as Legg-Calve-Pehes syndrome. It is most oftenly diagnose clinically. Because early X-rays are usually normal in the early stage of the disease, bone scintigraphy and MRI are the diagnostic modality of choice since both can detect minimal changes at early stages of the disease. Late radiographic signs include a radiolucency area following the collapse of subchondral bone (crescent sign) and ringed regions of radiodensity
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