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Avascular necrosis (AVN), also known as osteonecrosis, is a disease entity which commonly involves the hip joint. The end result of this disease can lead to collapse and complete deterioration of the head of the femur, commonly referred to as the "ball" of the hip joint.
The process which results in the development of AVN, is a decrease or complete cessation of blood flow to a part or all of the head of the femur bone. As the blood ceases to flow to the bone, the bone dies and a series of physiologic and chemical processes
then occur in the bone. These processes result in the body attempting to reabsorb and digest the dead bone. As this process progresses, the bone weakens and ultimately can collapse. During this process, and especially when collapse occurs, severe pain and limited motion in the hip debilitates the patient.
The exact reason why AVN occurs is unknown. We do know, however, that certain conditions can lead to a higher incidence of AVN in some individuals. Patients with Liver diseases, excessive alcohol intake, use of steroid drugs, and patients subjected to decompression disease (deep-sea divers) have a high incidence of developing this disease. Recently, with the advent of numerous chemotherapeutic drugs for the treatment of a variety of cancers, a higher incidence of AVN has been noted in patients using these drugs for prolonged periods.
Diagnosis can be made by routine x-ray of the hip in some cases, while in others it is necessary to obtain magnetic resonance imaging (MRI) scans of the hip. The MRI scan is capable of not only diagnosis, but also of providing a good picture of the amount of involvement of the femoral head. In some cases only a small portion of the femoral head is involved and with time the area of dead bone may be replaced with new live bone. In these cases the hip function is only mildly affected and no further treatment is required. If larger areas are involved, and the disease is diagnosed early bone-sparing operations such as core decompression and bone grafting are available. These involve surgical procedures where the avascular necrotic bone is drilled to enhance the development of new blood circulation and formation of new bone. After these types of procedures and extended period of time of non-weight bearing on the affected leg may be necessary to allow complete bone regeneration and prevention of femoral head collapse.
When severe end-stage AVN occurs in the hip and collapse of the femoral head has occurred, the only reasonable consideration for pain relief and return to function is to perform a hip replacement procedure. There are several types of hip replacement, with the specific type used dependent upon the patients age, bone quality, other diseases, and anticipated level of functional activity. Hemiarthroplasty, Total hip Resurfacing, total hip arthroplasty with or without cement, as well as devices with alternative bearing surfaces are available to the patient with end-stage avascular necrosis of the hip. Consultation with your orthopaedic surgeon as to the specific type of hip replacement is necessary before any decision for surgery is made.
The Ostenecrosis Support Group International
Excellent website for those who suffer from Osteonecrosis/Avascular Necrosis. The Only Support group in the world endorsed by the National Osteonecrosis Foundation
Website devoted to Osteonecrosis / Avascular Necrosis. In Depth information about ON/AVN.