Avascular necrosis has also been linked to corticosteroid use and alcoholism.

Due to a loss of blood supply to the femoral head, the femoral head gradually weakens and may collapse, leading to deformation of the joint surface. This occurs because the cells that remove dead bone (osteoclasts) remove the “support structure” for the femoral head. If too much bone is removed before the cells can produce new bone (osteoblasts), the femoral head will slowly collapse and the normally sperhically-shaped femoral head will become flattened to an egg-shaped configuration.

There are approximately 20,000 new cases of avascular necrosis reported in the United States each year, and AVN accounts for 10% of total hip arthroplasties performed. It is more common in men than women and bilateral (both hip) involvement is quite common (>80% incidence). When multiple joints are affected, it is termed multifocal osteonecrosis. This, however, is quite rare (3% incidence).

In the early stages of AVN, the patient will not feel pain and will likely be unaware of the disease progression. Patients will usually present with pain, usually located in the hip, and usually during activities like climbing stairs or inclines, and high-impact activities. Pain will continue to increase as the bone collapses.

Treatment involves preserving the function of the hip joint through reconstructing and preserving the deformed femoral head and ROM treatment to maximize motion and strength of the joint.