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Also known as: ON, Aseptic necrosis, Ischemic bone necrosis
Avascular necrosis or AVN, also called osteonecrosis, is a condition that occurs when areas of bone die because of poor blood supply. AVN can occur as a side effect of some cancers or cancer treatments.
Avascular necrosis may be mild and get better on its own after cancer treatment ends, or the condition may be severe, causing pain and long-term disability.
Avascular necrosis (AVN) is a common side effect of leukemia and lymphoma therapies. Up to half of children treated for acute lymphoblastic leukemia (ALL) have some degree of AVN. Children who have received a bone marrow transplantation are also at high risk of developing AVN.
The condition can occur in any bone. However, in pediatric cancer patients, AVN is often seen near the ends of long bones, an area called the epiphysis.
AVN can cause pain and affect joint function, especially in the knees, hips, shoulders, and ankles. Damage to bones and joints can lead to long-term problems including joint collapse and arthritis.
Older children and teens are more likely to develop AVN during cancer treatment compared to young children and adults. It is less common in children under 10 years of age.
Early stages of AVN can be hard to detect. Patients may not have pain or other symptoms until bone damage is severe. Children at high risk for AVN should be monitored during treatment.
Management of AVN depends on pain and the degree of bone damage. Pain management and physical therapy can help patients with symptoms. Some patients may need surgery to improve blood flow and relieve pressure within the bone. If damage is severe or joint collapse occurs, patients may eventually need joint replacement surgery.
Some patients may not have any symptoms, especially in the early stages. As the condition worsens, joint and bone pain may occur. Families may notice that a child limps, avoids using the affected joint, or has stiffness or reduced range of motion. AVN can sometimes result in collapse of bone, and pain may worsen suddenly.
AVN may be limited to one location or may affect multiple bones (multifocal). Because chemotherapy works throughout the body, AVN typically occurs in multiple joints in pediatric cancer patients, often the knees and/or hips. Other joints that might be affected include the shoulder and ankle.
Pain and disability usually depend on:
However, pain is not a reliable indicator of the severity of AVN. Small areas of AVN can be very painful. Other patients may not have pain, even when areas of AVN are very large.
Symptoms of Avascular Necrosis
Avascular Necrosis: Who is at risk?
Avascular necrosis (AVN) is a complex process. The main cause of AVN is a loss of blood supply to the bone. When blood vessels are too small or become damaged or clogged, nutrients and oxygen cannot get to the bone, and bone cells begin to die.
Cancer treatments, including chemotherapy and radiation, may cause bone cells to die and/or interfere with healing. Thus, bone may break down faster than it can repair itself. Treatment may also affect the blood supply to the bone, resulting in AVN.
Many children receive corticosteroid medicines (e.g. prednisone, dexamethasone) as part of chemotherapy. These medicines may also be used to help manage side effects such as nausea and swelling. However, corticosteroids can increase fatty substances (lipids) in the blood. A buildup of fat can cause blood vessels to become blocked. These medicines may also change the cells that line blood vessels, causing blood vessels to become thin or weak.
High-dose, continuous dexamethasone is associated with the highest risk for AVN compared to prednisone or an alternating dexamethasone schedule. Certain medicines, such as asparaginase, can also affect the action of dexamethasone and increase risk for AVN because of how the medicines work together. Other medicines including methotrexate (MTX) can cause bone damage and may increase AVN risk, especially when used with corticosteroids.
Medical centers differ in how they identify and monitor at-risk patients. Imaging tests are used to identify areas of AVN, sometimes called lesions. Magnetic resonance imaging (MR) is the most sensitive imaging test for diagnosis of AVN. X-rays are less sensitive but may be helpful for monitoring progression and for following patients after surgery. Less often, other types of tests including bone scans and computerized tomography (CT) may also be used.
Some clinics may screen pediatric cancer patients at high-risk for AVN before they have symptoms. This type of screening is usually part of a clinical trial or research study and mainly focuses on the knees and hips. When high-risk patients are screened before having symptoms, the knee is the most common joint to show signs of AVN on imaging tests. AVN usually occurs on both sides of the knee joint (femur and tibia); the knee may be the only joint involved. However, if AVN is seen in the hip, then the knees are usually affected as well.
AVN associated with corticosteroids can usually be seen on MRI within the first year of high-dose steroid treatment. Patients who do not have evidence of AVN on MRI after 12 months are not likely to develop AVN, even with continued steroid treatment.
Doctors are looking for ways to improve diagnosis using more sensitive imaging tests. Research is also being done to learn how to better predict progression of AVN.
The course of AVN is hard to predict. The lesions may go away, stay stable, or get worse. Progression may be slow or quick.
The severity, or stage, of AVN is important to plan treatments. Doctors consider two main factors:
If the damaged bone cannot support the joint surface, the bone under the cartilage will start to collapse. The normally smooth layer of cartilage that lines the joints starts to peel away. This results in joint problems like arthritis, causing pain and limiting movement of the joint.
Joint collapse is more likely if the lesion:
Because the knees and hips are weight-bearing joints, joint collapse is common when AVN is severe. In the hips, when AVN affects greater than 30% of the joint surface, joint collapse usually occurs within 2 years.
Management of AVN is based on individual patient needs. Doctors consider:
The main goals of treatment are pain control, maintaining joint function, and preventing further damage.
Treatment strategies may include:
A doctor may prescribe pain medicines such as an NSAID (meloxicam, celecoxib) or acetaminophen. However, some pain medicines may also put a patient at risk for bleeding, liver or kidney problems, and increased side effects from chemotherapy. Families should check with their doctor before taking any medicine, including over-the-counter medicines, to make sure that it doesn’t interact with other medications or make side effects worse.
Researchers are studying how medicines that influence blood flow, blood clotting, inflammation, lipid metabolism, and/or bone cells could be used to prevent or treat AVN. However, results have not shown a consistent benefit.
Physical therapy is important for patients with AVN. A physical therapist can recommend ways for patients to reduce weight bearing and avoid painful activities. They can prescribe specific therapies such as:
Reduced weight bearing may be recommended to prevent joint damage, control pain, and allow healing after surgical procedures. However, many doctors and physical therapists recommend the patient engage in low-impact activity as pain allows. Physical activity is important to increase circulation, promote bone repair, and strengthen muscles that support joints.
Patients with AVN should avoid high-impact activities such as running, jumping, and contact sports. This is especially important for patients with more severe AVN to prevent joint injury and collapse.
Patients may find help from mind-body therapies such as massage, acupuncture, biofeedback, and relaxation techniques. Specific techniques can help patients manage pain, reduce stress, decrease muscle tension, and improve blood flow. Families should talk to their care team before trying any new therapy to make sure it is safe and fits individual patient needs.
In the case of severe AVN, the care team may recommend changes to the chemotherapy plan to reduce exposure to corticosteroids. These decisions must be balanced against risks to overall patient health.
Some patients may need surgery to manage AVN. Surgery may be used to help promote bone healing and prevent further bone damage. Surgery may also be needed to replace a joint. Types of procedures include:
Know your risk. Talk to your care team about cancer treatments (including dose received) and other risk factors.
Watch for symptoms and get recommended screenings. Tell your care team about pain or joint problems, especially new or worsening symptoms. After treatment, make sure bone health is part of your survivorship care plan.
Be physically active. Modify physical activities to reduce weight bearing, and let pain be your guide. Avoid high-impact activities and contact sports to protect your bones and joints. If you are not sure about an activity, ask your doctor or physical therapist.
Wear supportive shoes and use orthotics and assistive devices as prescribed. This is important to help with joint alignment and function. Appropriate footwear can also help prevent falls and joint injury.
For bone health and overall well-being, a healthy lifestyle is important:
eat a healthy diet, be physically active, maintain a healthy weight, and do not smoke.
Reviewed: January 2019