Also known as AVN or osteonecrosis (bone death), this is a condition with many underlying causes. Common causes of AVN include excessive alcohol consumption, high dose or prolonged oral steroids, and trauma. Other causes can include certain cancer treatments, organ transplantation, sickle cell anemia and other rate genetic disease. It has also been associated with HIV/AIDS, diabetes and lupus.
AVN is caused by reduced or absent blood flow to the femoral head. This results in bone death much like occurs to heart muscle in a heart attack. As the bone dies, its ability to tolerate loads and stress that occur with everyday activities is compromised and this may eventually lead to collapse of the femoral head. In the early stages of AVN, x-rays may be normal but the condition can be detect by MRI. As larger areas of the femoral head become involved, the conditions becomes apparent on x-rays. By this point, the condition may be terminal in the sense that blood flow cannot be restored to the bone.
The treatment of AVN involves unloading the bone to reduce stress and prevent collapse, Some cases may revascularize through a process of sequential healing. Procedures such as core decompression aim to stimulate a healing response by reducing pressure inside the bone creating a fracture healing response. These procedures may be successful earlier in the course of the disease but in some cases, progression will occur despite early intervention. Once collapse of the femoral head occurs, total hip replacement is the only procedure that can eliminate pain and restore joint mobility to the hip.
There is some evidence that bisphosphonate medications (alendronate) may limit the progression of avascular necrosis though other studies have documented an association between certain bisphosphonates and osteonecrosis of the jaw.