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What is Avascular Necrosis?
Avascular necrosis, also known as AVN, osteonecrosis, aseptic necrosis and ischemic necrosis, affects men and women of all ages. The thirties and forties are the most common ages for AVN to develop, according to Penn State Hershey Medical Center. AVN is a disease of the bone caused by a temporary or permanent loss of blood supply to the bone cells. While the hip joint is the most frequently involved joint, other locations for AVN include the shoulder, ankle, wrist, elbow and knee.
There are six stages of avascular necrosis identified by clinical and laboratory findings. Treatment options to preserve the joint as long as possible vary according to each stage, and include conservative management using medications and therapy in the early stages and surgical procedure options in advanced cases.
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Stages 0 Through II
In the beginning of AVN at stage 0, the patient has no symptoms and X-ray findings are normal. Histological studies indicate osteonecrosis. At stage I, the patient may begin to have symptoms, such as joint pain and a reduction in range of motion. X-ray and CT scan results are still unremarkable and histology results are abnormal. By stage II, X-ray results are abnormal and MRI findings are definitive for AVN.
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Stages III and IV
In the third stage of AVN, radiographic studies become more defined showing the amount of collapse of the femoral head. Flattening of the femoral head indicates stage IV AVN. The margin of the cartilage and the underlying bone are referred to as the crescent sign.
OrthoFracs Orthopaedic Surgery Resource for Doctors reports the Steinberg Classification System for staging further breaks down stages I through IV into mild (A), moderate (B) and severe (C) according to the crescent or percentage of femoral head involvement as follows:
- A: Less than 15 percent of the articular surface
- B: Between 15 and 30 percent of the articular surface
- C: More than 30 percent of the articular surface
Non-surgical treatment consisting of partial weight bearing may be ordered for mild cases of AVN. Surgical intervention will ultimately be required when the femoral head reaches more than 50 percent collapsed. Surgical options include: core decompression, which involves drilling through the dead bone tissue to remove the inner layer and allow the blood to flow to the bone; bone grafting, which is the placement of healthy bone tissue into the core; osteotomy, which relocates living cartilage around the femoral head; and arthroplasty or total hip replacement.
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Stages V and VI
In the advanced stages of avascular necrosis, there is decreased joint space and ultimately extensive joint destruction. Total hip replacement is the only option for possible successful management of symptoms. Total joint replacement requires months of recovery, which includes physical therapy and medications for pain control.
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Penn State: Avascular Necrosis http://www.hmc.psu.edu/healthinfo/a/avascularnec.htm
OrthoFracs: Osteonecrosis of the Hip http://www.orthofracs.com/adult/elective/hip/avn/classification.html