Avascular Necrosis (AVN) of Hip - Definition, Diagnosis and Management.
Avascular Necrosis (AVN) of the femoral head can cause hip joint pain. It is defined as, death of the femoral head following partial or complete obliteration of its blood supply.
It can be classified into two types
1.Primary or Idiopathic: in which no cause can be established.
2.Secondary: due to some underlying cause which may include
- alcohol abuse
- injectable steroid use
- radiation therapy
- Gouchers disease
- Caisson disease
- renal osteodystrophy
- sickle cell anaemia
Primary disease is more common in men, between the age of 40 to 60 years. In up to 60% of cases both the hips may be involved.
Diagnosis can be established from the following investigations
- Magnetic Resonance Imaging (MRI) scan of the hip joints. It is the investigation of choice as it can detect the necrotic bone even where other investigations fail.
- Computed Tomography of both hips. It shows increased radio density.
- Isotope scan will show decreased uptake of the isotope in the affected hip in early stages (no symptoms present).
Prognosis of avascular necrosis of femoral head is poor. Eventually almost all patients develop subchondral collapse, following which progression to osteoarthritis is inevitable.
This means that the dead bone in the head of femur becomes weak and breaks down. This causes the the hip joint to become incongruous. This causes osteoarthritis of the hip joint.
This x ray shows necrosis in both the femur heads following steroid use. On the left side collapse has occurred and subsequent arthritis has developed. On the right head there is no collapse.
Till now, there is no effective treatment to slow down the progression to osteoarthritis. Once osteoarthritis has set in then the treatment methods for osteoarthritis hip are used.
Many operations are described in the literature for avascular necrosis of the hip. Most of these have only historical importance now. They include
1. Core decompression.
2. Core decompression with bone grafting.
3. Vascularized fibular grafting.
4. Intertrochanteric osteotomies.
I personally don't use any of the above operations. I manage the patient with analgesics and walking aids (crutches) as far as possible. When pain becomes unbearable or patient wants freedom from analgesics and walking aids, then I perform a total hip replacement.
Total hip replacement is the only permanent cure for osteoarthritis hip, which is the ultimate outcome of avascular necrosis.
Frequently Asked Questions
How long does it take for the femoral head to collapse after necrosis?
It varies from patient to patient. No criteria have been developed to predict it. Can vary from few months to more than 5 years.
Can the use of crutches for walking or bed rest prevent the collapse?
Such methods have been proved to be ineffective.
Can surface hip replacement (ASR) be done in AVN?
Yes it can, but only after subsequent x rays show no progression of collapse of the femoral head.
Can the dead bone undergo revascularization (develop blood vessels and is replaced with live and healthy bone)?
Yes it can, but this is rare.
I hope the information provided was helpful. If you have any query you can ask me at the contact me page.
This page was last updated on 2nd March 2009.
Other common causes of hip pain...
Congenital Dislocation of Hip
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