"Diagnosis is not the end, but the beginning of practice." - Martin H. Fischer.
Bone disorders can affect the quality of life. Living with a debilitating bone disorder, such as Avascular Necrosis, can be challenging. The severe pain caused by the disease can give you sleepless nights and prevent you from performing even simple tasks, such as climbing stairs and using a washroom. However, understanding the implications of diagnosis can help doctors determine the best treatment option.
Avascular necrosis (AVN) or Osteonecrosis is the death of bone tissue caused by the disrupted blood supply. It can lead to tiny cracks in the bone and eventual collapse. AVN can affect any bone but is more common in the hip joint, knee, shoulder, and ankle.
The common symptoms of AVN include pain, stiffness of joints, restricted range of motion, crackling sound, limping, and complete immobility. Certain patients may develop AVN on both sides (bilaterally), that is, in both hips or both knees.
The common causes of the disease are joint injury, excessive alcohol or smoking, long-term use of steroids, radiation and chemotherapy, high lipid content in blood, and certain diseases, such as sickle cell anemia and Gaucher's disease.
Avascular necrosis (AVN) is diagnosed by:
X-rays are usually normal in the early stages of AVN. However, it can reveal the bone changes that occur in the later stages of the disease.
MRI and CT scans can provide a detailed image of the changes in bone occurring at an early stage of the disease. However, MRI is considered the gold standard for the detection of AVN.
It involves an injection of radioactive material into the vein. The tracer then travels to the injured bone and shows up as bright spots on the imaging plate.
The stages of AVN help in determining the extent of the lesion, the presence of subchondral fracture, and the location of the lesion. Although there are many staging systems, the most commonly used system is the ARCO classification system.
The international classification of Avascular Necrosis by Association Research Circulation Osseous (ARCO) is as follows:
| ARCO Stage | Image Findings | Description |
|---|---|---|
| 1 | X-ray normal MRI abnormal |
A band lesion of low signal intensity around the necrotic area is seen on MRI. A cold spot is seen on the bone scan. No changes are seen on plain radiographs. |
| 2 | X-ray abnormal MRI abnormal |
Osteosclerosis, focal osteoporosis, or cystic changes are seen in the femoral head on plain radiographs or CT scans. There is no evidence of subchondral fracture, fracture in the necrotic portion, or flattening of the femoral head. |
| 3 | Subchondral fracture on X-ray or CT scan | Subchondral fracture, fracture in the necrotic portion, and/or flattening of the femoral head are seen on plain radiography or CT scan. |
| 3A (early) 3B (late) |
Femoral head depression ≤ 2 mm Femoral head depression > 2 mm |
|
| 4 | X-ray Osteoarthritis | Osteoarthritis of the hip joint with joint space narrowing, acetabular changes, and destructions are seen on plain radiographs. |
Your AVN stage at diagnosis provides a general overview of what to expect. Be sure to talk to your orthopedic doctor about your AVN stage and how it affects your treatment and recovery process.