Bilateral femoral AVN

Both femoral heads show the crescent sign with altered signals in the left femoral neck and free fluid in the joints (left > right)
Pathologic changes leading to AVN are initiated in two broad categories of anatomic regions, intravascular(arterial and venous)and extravascular factors (intraosseous and capsular). Diseases or conditions associated with or leading to AVN are Truama, Hemoglobinopathies, Polycythemia, Caisson disease - Dysbaric osteonecrosis and Gaucher's disease, Infection, Neoplasms, Hypercortisolism - Corticosteroid medications and Cushing's disease, Alcohol consumption, Pancreatitis, Chronic renal failure, Cigarette smoking, Collagen vascular diseases, Congenital and developmental, Organ transplantation.
MRI is the most sensitive means of diagnosing AVN. MRI provides the criterion standard of noninvasive diagnostic evaluation. It is more sensitive than CT scanning or planar scintigraphy, and is much more sensitive than plain film radiography for detecting AVN.A staging system using radiographic findings has been developed by Ficat and Arlet and has been used widely for treating AVN. This has been supplanted by the classification system of Steinberg et al, which incorporates MRI and scintigraphic findings.

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