Human bones need a steady supply of blood to survive. When something blocks that flow of blood, it can severely weaken and even kill the bone if not treated, said Dr. Robert M. Peroutka, a hip and knee surgeon at MedStar Orthopaedics. But, he explains, there are treatment options to prevent this from happening.
What is avascular necrosis?
Avascular necrosis, also known as AVN or osteonecrosis, is a process that happens when there is a disruption of the blood supply to the bone. It can cause tiny fractures to occur that change the bone's structural integrity, which can result in the bone eventually dying and collapsing.
When this happens to bone adjacent to a joint, such as in the hip, the overlying cartilage of the joint can be disrupted and result in destruction of the joint. Since it tends to happen in patients between the ages of 30 and 60, the long-term consequences can be significant, and [the condition] should be addressed as early as possible.
The blood supply to an area of bone can be disrupted by trauma, such as a fracture or dislocation of a joint. There are also some other conditions sometimes associated with the onset of avascular necrosis. Some of these conditions include long-term steroid use, long-term use of bisphosphonates [medications that prevent loss of bone mass], and heavy alcohol consumption. Some medical conditions like sickle cell anemia and Gaucher's disease can also result in avascular necrosis. Sometimes its cause is unknown.
What are the symptoms?
In the early states of avascular necrosis, patients may ... have no symptoms, but as the disease process progresses, pain occurs when the person puts weight on it. Eventually the pain will become such that there is no relief, even when lying down. The pain worsens as the joint is progressively disrupted, which can lead to destruction and severe arthritic changes of the joint. Avascular necrosis may occur in the hip, knee, shoulder, hand, foot and even the jaw. If the hip is affected, it could result in groin pain. The disease is often seen in both hips or both knees when it occurs.
How is it diagnosed?
X-rays may appear normal in the early stages of avascular necrosis, but as the disease worsens, X-rays may show boney changes. An MRI scan is the best diagnostic tool to diagnose early avascular necrosis, which is sometimes seen in patients who do not have symptoms. A CT scan and bone scan may also show early changes.
Reducing weight bearing by using crutches or a walker for several months may result in decreased pain and potential healing, or it may slow the progression of the disease. Medications may be helpful in reducing pain or slowing the progress of the disease as well.
Early stages of avascular necrosis in the hip and knee may respond to some surgical procedures such as core decompression. This procedure entails drilling a tunnel to the area of diseased bone in the hope of allowing the in-growth of blood vessels to the area with the subsequent production of healthy bone.
A surgical procedure for avascular necrosis of the hip called free-vascularized fibula graft also entails drilling a tunnel to the diseased area of bone, which is then filled with a piece of fibula bone (taken from the leg). The fibular bone graft is then connected to a blood vessel, thus restoring blood supply to the bone.
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The surgical procedures described above are not as predictable or successful in their results compared to total joint replacement surgery, which often is the most effective treatment for end-stage avascular necrosis.
What happens if the disease is not treated?
If avascular necrosis is not treated, then the bone weakens and collapses. This increases the pain and can [destroy] the integrity of the adjacent joint. A total joint replacement may subsequently be the best treatment.