What is avascular necrosis?
Avascular necrosis (AVN) is a condition that occurs when bone tissue dies because of too little blood supply. With avascular necrosis, the bone eventually collapses after tiny breaks (or microfractures) occur. Commonly, the condition affects the thigh bone (femur) in the hip area, but it can affect other bones in the body, including the jaw, hand/wrist, elbow, shoulder, knee, and foot locations. Avascular necrosis typically will progress with time, but may remain with only minimal symptoms for quite some time. The condition is also called osteonecrosis, aseptic necrosis, or ischemic bone necrosis.
What causes avascular necrosis?
There are various reasons for lack of blood supply to the bone. The most common reasons include:
Previous injuries to the bone where the blood supply to the bone is disrupted. This may occur following a broken bone or a dislocated joint
Excessive alcohol intake
Long-term use of oral steroids
Use of certain medication families, such as bisphosphonates (though very rare)
Congenital (childhood) conditions (ie, Legg-Calve Perthes Disease)
Other less common causes of avascular necrosis include:
Cancer treatments like radiation and chemotherapy
Sickle cell anemia
Decompression disease (the “bends” – commonly related to scuba diving)
What are the symptoms of avascular necrosis?
The condition may cause no symptoms; however, some people have 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. In some cases, the pain may come on suddenly and be severe, but may “burn out” with time.
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 suspicions of avascular necrosis can be most reliably diagnosed with the use of magnetic resonance imaging (MRI). Other, less reliable, means of diagnosing the condition are computerized tomography (CT scan), nuclear bone 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?
There are many treatments for avascular necrosis. Treatments are based on various factors, including the patient's age, the amount and location 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. The following are treatments for avascular necrosis:
Reduced weight bearing—If the condition is diagnosed early, reduced weight bearing can be helpful in removing weight from the affected joint, and thus greatly lessen the risk for microfractures in weight-bearing surfaces. This may involve the use of crutches or the limitation of certain activities.
Core decompression—Core decompression is a surgery in which the inner layer of bone is removed, theoretically allowing for better blood flow to the area of concern. This surgery is most effective for people in the earliest stages of the disease.
Osteotomy—This surgery reshapes either the affected bone or surrounding bones in order to decrease stress on the afflicted area. The surgery is most effective for patients with advanced forms of the disease and for when avascular necrosis affects a large area of bone. Depending on how advanced the disease state is this surgery can be very effective with the right indications.
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, to recreate the mechanics of a human joint.
Other exploratory treatments include medications, combination therapies meant to increase the growth of new bone and blood vessels, and electrical stimulation. Such treatments have been used alone and in conjunction with other treatments like core decompression. Most people find that treatment for avascular necrosis is an ongoing process. It is vital that patients carefully follow instructions about activity limitations and work with their doctors to ensure that appropriate treatments are used.
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