What is Avascular Necrosis?
Avascular necrosis is a disease resulting from the temporary or permanent loss of the blood supply to the bones. This can ultimately cause weakening and collapse of the bone. Although it can happen in any bone, avascular necrosis most commonly affects the ends (epiphysis) of long bones such as the femur, the bone extending from the knee joint to the hip joint. Other common sites include the upper arm bone, knees, shoulders, and ankles. The condition is also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis. Avascular necrosis gets worse with time.
What Causes Avascular Necrosis?
There are various reasons for lack of blood supply to the bone. These reasons include:
- Injuries to the bone, including a broken bone or dislocated joint
- Excessive alcohol intake
- Long-term use of steroids
Other less common causes of avascular necrosis include:
- Cancer treatments like radiation and chemotherapy
- Sickle cell anemia
- Decompression disease (the bends)
What are the Symptoms of Avascular Necrosis?
The condition may cause no symptoms. However, as the disease progresses most patients experience joint pain or a loss of motion in the affected joint. If avascular necrosis affects the hip, there may be groin pain that spreads down the thigh to the knee. In the wrist, the condition may cause wrist pain and weakness in the fingers. In the shoulder, avascular necrosis can result in pain and stiffness in the upper arm. In the knee, the condition can cause pain in the lower end of the thighbone.
How is Avascular Necrosis Diagnosed?
In many cases, the condition can be diagnosed with x-rays. However, x-rays cannot always detect avascular necrosis. Earlier indications of avascular necrosis can be diagnosed with the use of magnetic resonance imaging (MRI) or a nuclear bone scan. Other means of diagnosing the condition are computerized tomography (CT scan), biopsy (removing and studying a small section of affected bone) and functional evaluation of the bone (testing that involves measuring the pressure inside a bone).
How is Avascular Necrosis Treated?
Treatments for avascular necrosis are based on various factors, including the patient’s age, the location and amount of bone that the condition affects, the underlying cause of the problem, and the stage of the disease. Avascular necrosis treatment is meant to ensure bone and joint survival, to prevent additional bone damage, and to allow the patient to better use the joint affected. Some treatments for avascular necrosis include the following:
- Reduced weight bearing—If the condition is diagnosed early, reduced weight bearing can be helpful in removing weight from the affected joint. This may involve the use of crutches or the limitation of certain activities.
- Range-of-motion exercises–may be prescribed to maintain or improve joint range of motion.
- Electrical stimulation–to induce bone growth.
- Core decompression—Core decompression is a surgery in which the inner layer of bone is removed. This surgery is most effective for people in the earliest stages of the disease.
- Osteotomy—This surgery reshapes the bone in order to lessen stress on the area affected. The surgery is most effective for patients with advanced forms of the disease and for when avascular necrosis affects a large area of bone.
- Bone graft—In this surgery, healthy bone is transplanted from one part of the patient to the area affected by avascular necrosis. This procedure is complex and its effectiveness has not yet been proven.
- Arthroplasty/total joint replacement—This treatment is used in late-stage avascular necrosis and when the joint is destroyed. The diseased joint is replaced with artificial parts.
For most people with avascular necrosis, treatment is an ongoing process. Doctors may first recommend the least complex and invasive procedure, such as protecting the joint by limiting movement, and watch the effect on the patient’s condition. Other treatments then may be used to prevent further bone destruction and reduce pain. It is important that patients carefully follow instructions about activity limitations and work closely with their doctor to ensure that appropriate treatments are used.