Causes And Risk Factors Linked To Avascular Necrosis

Avascular necrosis occurs when blood flow to a bone is cut off, resulting in the death of the affected bone tissue. Also known as osteonecrosis, bone infarction, and aseptic necrosis, this condition most often affects the hips, knees, shoulders, spine, and wrists. Some patients may develop avascular necrosis on both sides of the body. Typically, the only symptom is joint pain, and this may occur even while the patient is resting. If left untreated, avascular necrosis can cause the bone to collapse, resulting in arthritis and the need for joint replacement surgeries. This ailment is most commonly diagnosed in patients between twenty and fifty years old, and an estimated twenty thousand new cases of avascular necrosis are diagnosed in the United States each year. To diagnose this condition, doctors perform a physical exam to check for pain and range of motion in the joints. MRI scans, CT scans, x-rays, and bone scans are needed to confirm the diagnosis and assess the condition's severity. Treatment focuses on preventing additional bone loss, and both medications and surgery may be necessary.

Some of the most common risk factors and causes associated with avascular necrosis are outlined below.

Gaucher's Disease

Gaucher's disease is an inherited condition that causes an enzyme deficiency. This deficiency affects the GCase enzyme and increases a patient's risk of avascular necrosis. Gaucher's disease causes diminished blood flow to the bones, and patients often experience bone pain that may be severe. In addition, patients with this disease have fragile bones that fracture much more easily than the bones of healthy individuals. There are three types of Gaucher's disease, and type one is the most prevalent form in Western countries. Patients with this form of the condition have a normal life expectancy and an excellent prognosis. Treatment includes GCase enzyme replacement therapy, which patients normally receive as an intravenous infusion once every two weeks. A newer treatment called substrate reduction therapy uses oral medicines and may be a more convenient option for some Gaucher's disease patients.

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Trauma To The Joints And Bones

Trauma to the joints and bones can interrupt blood circulation and result in bone death. For example, injuries such as fractures and dislocations may damage blood vessels close to the affected joints, which could compromise blood flow. For this reason, patients who have experienced a fall or other injury should have a prompt assessment with their clinician. To assess trauma to the joints and bones, doctors can perform x-rays, CT scans, and other imaging studies, and patients may need to be referred to an orthopedic surgeon for specialist care. To reduce the risk of avascular necrosis following trauma, doctors may recommend braces and other assistive devices that reduce the weight placed on the affected joint. Treatments to stimulate the growth of new bone may be advised, and surgical options such as bone grafts, joint replacements, core decompressions, and osteotomy might be appropriate.

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Sickle Cell Anemia

Sickle cell anemia is another genetic condition that is a major risk factor for the development of avascular necrosis. For patients with sickle cell anemia, the red blood cells are an atypical shape, and they break down faster than they should. This leads to anemia (low red blood cell count) and can cause fatigue, frequent infections, shortness of breath, and episodes of severe pain requiring hospitalization. Some patients may develop jaundice, and the condition damages the liver, spleen, and other organs. As children, sickle cell patients may have delayed growth and development. Patients with this condition are known to have a low bone density, and this in itself can elevate their risk of avascular necrosis. The sickle shape of these patient's blood cells also makes it more difficult for blood to flow to the bones effectively, further elevating the risk of avascular necrosis.

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Fatty Deposits In Blood Vessels

Fatty deposits in blood vessels can impede proper blood circulation and increase the likelihood of avascular necrosis. Typically, fatty deposits are made of cholesterol, and these deposits often lead to atherosclerosis, a hardening and stiffening of the arteries. Patients with high cholesterol, diabetes, obesity, and high blood pressure are more likely to have fatty deposits in their blood vessels. These deposits may break apart and block smaller blood vessels, and they can also form dangerous clots that cut off blood flow to major vessels. To check for the presence of these deposits, doctors can perform ultrasounds and other advanced imaging studies. If deposits are found, patients may need to take medications to lower cholesterol and blood pressure, and they may also need to make lifestyle modifications and lose weight. In particular, reducing saturated fat and trans fat in the diet can cut down on the fatty deposits present in the vessels. Occasionally, surgical intervention can be used to remove some deposits; this depends on which particular vessels are blocked.

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Radiation Therapy

Radiation therapy patients receive for cancer and other conditions has been shown to cause avascular necrosis in some cases. Avascular necrosis associated with radiation therapy is most commonly seen in the hips, specifically in the femoral head. While doctors attempt to target radiation therapy treatments and minimize side effects to healthy tissue, avascular necrosis remains a frequent side effect of pelvic radiation. In addition, patients who receive radiation may have underlying conditions like cancer, lupus, and other ailments that weaken the immune system. A weak immune system further elevates the risk of avascular necrosis, as does chemotherapy. Patients who need to have radiation therapy should discuss their individual risk of avascular necrosis and find out how the radiation and chemotherapy could affect their bones. Patients may wish to have regular bone density scans, and doctors will prescribe bone-strengthening drugs for patients at particularly high risk of avascular necrosis.