What Is Avascular Necrosis?
- Avascular necrosis is a localized death of bone as a result of local injury (trauma), drug side effects, or disease.
- This is a serious condition because the dead areas of bone do not function normally, are weakened, and can collapse.
- Avascular necrosis ultimately leads to destruction of the joint adjacent to the involved bone.
- The hip is the most common joint affected by avascular necrosis, followed by the knee, shoulder, ankle, elbow, and wrist.
- Avascular necrosis is also referred to as aseptic necrosis and osteonecrosis.
What Causes Avascular Necrosis?
While the precise mechanism for the development of avascular necrosis is not known, it is suspected that interruption of the blood supply to the affected bone plays some role. This can occur when traumatic impact injures the blood vessels to the bone or when diseases produce areas of abnormal circulation.
There are many causes of avascular necrosis, but the vast majority of avascular necrosis is caused by either traumatic injury to the affected bone (such as fracture and dislocation), steroid medication usage (glucocorticoid medications such as prednisone and prednisolone, particularly when given in high doses), or excessive alcohol consumption.
Other risk factors for developing avascular necrosis include cigarette smoking, pregnancy, radiation and chemotherapy treatments, bone marrow and blood diseases (including sickle cell disease, leukemia, Gaucher's disease, thalassemia), and underwater diver's disease (from bone effects of Caisson disease, also known as dysbarism or "the bends"). Avascular necrosis occurs more frequently in patients with certain underlying diseases, including systemic lupus erythematosus, diabetes mellitus, vasculitis, and inflammatory bowel disease.
It is currently suspected by some researchers that intravenous bisphosphonate medications, including zoledronate (Zometa) and pamidronate (Aredia), which are used to reduce elevated calcium levels in patients with cancer and to treat osteoporosis, may increase the risk of avascular necrosis of the jaw bone. Ironically, bisphosphonates are actually used by some to treat the bone pain and decrease disability in patients with avascular necrosis.
What Are the Symptoms Avascular Necrosis?
- Aseptic necrosis begins as a painless bone abnormality. It can remain painless.
- The involved bone often later develops pain, especially with use.
- Pain in the affected joint is usually the first symptom of avascular necrosis.
- When the lower extremity is affected, this can lead to a limp during walking.
- If the hip is affected, groin pain is common, especially when walking. As the ball of the hip collapses with progression of avascular necrosis of the hip, pain can persist in the hip after rotation or weight-bearing with walking.
How Is Avascular Necrosis Diagnosed?
The diagnosis of aseptic necrosis can often, but not always, be made with X-rays. By the time changes are apparent by plain film X-ray testing, there has been substantial damage to the bone affected. Therefore, bone changes visible on plain film X-ray are considered a later-stage finding. This makes it important that you share all your medical conditions and social habits with your health-care provider so she can make a decision if you are at risk for avascular necrosis even before plain X-rays reveal this disease. Earlier signs of avascular necrosis can be detected with an MRI scan (magnetic resonance imaging) or suggested by a nuclear bone scan.
It is important to note that when avascular necrosis is not caused by trauma, it is possible to have multiple joints involved, such as the hips as well as the shoulders or knees.
What Is the Treatment for Avascular Necrosis?
The treatment for avascular necrosis includes:
- Avoiding injury to bone that is affected by avascular necrosis is the first line of treatment.
- This can include non-weight-bearing (crutches), etc. when a weight-bearing joint is involved.
- The aim is to attempt to preserve the affected joint and avoid joint replacement, when possible, especially in young individuals.
- Treating any underlying cause of avascular necrosis (stopping smoking and alcohol intake, etc.) and management of underlying diseases is essential to minimize progression of disease and to prevent involvement of other bones.
- Bisphosphonate medications, such as alendronate (Fosamax), have been shown to reduce bone pain and improve function in patients with avascular necrosis.
- Additionally, medications to lower blood fats (lipids, including cholesterol and triglycerides) and blood-thinning medications (anticoagulants) have been used effectively in certain situations.
The surgical management of avascular necrosis can be divided into joint-preserving procedures and joint-replacement (arthroplasty) procedures.
- Joint-preservation operations that delay the need for total joint replacement include measures that allow improved blood supply to the affected bone. These procedures are typically used in early avascular necrosis of the hip and include removal of a core of bone from the head of the femur bone of the hip (core decompression) as well as local bone-grafting procedures.
- Sometimes bone-resurfacing procedures are used in an attempt to further delay joint-replacement surgery.
- When avascular necrosis has progressed to a significant stage and bone has collapsed, joint-replacement surgery is ultimately required.
How Do You Prevent Avascular Necrosis?
- Avoiding injuries, such as fracture of bone and dislocation of joints, will eliminate the risk of trauma-associated avascular necrosis.
- The key to the prevention of joint destruction from avascular necrosis is early diagnosis of the underlying cause.
- Optimal treatment of underlying diseases or conditions can reduce the risk of developing avascular necrosis.
What Is the Prognosis for Avascular Necrosis?
The underlying cause as well as the amount and location of bone affected by avascular necrosis to some degree determine the outcome. Larger areas of avascular necrosis often cannot be repaired by joint-preserving methods and ultimately joint replacement is necessary.
When an underlying disease or condition is the cause, optimal treatment of that disease or condition can decrease the chances of worsening the avascular necrosis or involvement of other areas of bone.
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Matsuo, Keisuke and Tomio Hirohata, et al. "Influence of Alcohol Intake, Cigarette Smoking, and Occupational Status on Idiopathic Osteonecrosis of the Femoral Head." Current Orthopaedic Practice 234 September 1988: 115-123.