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Avascular Necrosis (AVN) / Osteonecrosis

Also known as: ON, Aseptic necrosis, Ischemic bone necrosis

What Is Avascular Necrosis (AVN)?

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.

Children treated with high doses of corticosteroids (dexamethasone and prednisone) are at higher risk.

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.

A graphic explaining the term avascular necrosis. "A" means without, "vascular" means blood supply, and "necrosis" means death of cells or body tissue. Avascular necrosis / Osteonecrosis means the breakdown of bone tissue caused by poor blood supply.

AVN in Children with Cancer

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.

AVN can occurr at the ends of long bones, such as the femoral head of the femur. Here, the femure bone structure is labeled, indentifying the articular proximal epiphysis, metaphysis, diaphysis, and distal epiphysis.

In pediatric cancer patients, AVN is often seen near the ends of long bones, an area called the epiphysis.

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.

Symptoms of AVN

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:

  • What areas of the bone are affected
  • How much AVN is present
  • How quickly damage progresses
  • How well the bone can repair itself

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

  • Pain (may come and go or be constant)
  • Stiffness or “catching” in a joint
  • Limping or gait changes
  • Avoiding using a joint or doing certain activities
  • Problems walking up/down stairs

Avascular Necrosis: Who is at risk?

  • High doses of dexamethasone or prednisone during cancer treatment
  • Children older than 10 years of age
  • Sickle cell disease
  • High doses of radiation to the bone
  • Treatment with asparaginase plus dexamethasone
  • Inherited genetic changes
 

Causes of AVN

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.

Diagnosis of AVN

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.

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:

  1. Size of the lesions
  2. Whether damage is in bone that supports the joint surface

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:

  • occurs in bone that is close to the joint surface
  • is large, covering 30% or more of the surface
  • occurs in a weight-bearing joint (hips, knees)

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.

Treatment of AVN

Management of AVN is based on individual patient needs. Doctors consider:

  • Patient age
  • Patient health and stage of cancer
  • Cancer treatments and chemotherapy schedule
  • Stage of AVN
  • Bones and joints affected
  • Pain severity

The main goals of treatment are pain control, maintaining joint function, and preventing further damage. 

Treatment strategies may include:

Medications

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

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:

  • Exercises to address any limitations a patient may have such as muscle weakness, joint stiffness, or difficulty with walking.
  • Assistive devices (walkers, crutches, or canes) to help with mobility and reduce weight bearing through painful joint. A physical therapist will provide the most appropriate option and teach patients how to walk with the device.
  • Orthotics and braces (arch supports, knee sleeves, or arm slings) provide support to painful joints to help decrease pain during daily activities
  • Instructions for at-home care including exercises, guidance for physical activity, and heat and/or ice therapy

AVN and Weight bearing Activity

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.

 

Complementary or integrative therapies

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.

Adjustment of chemotherapy

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.

Surgery

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:

  • Core decompression – This procedure is used to relieve pressure inside the bone to promote healing and blood flow. In core depression, the surgeon drills small holes into the affected bone to break up the damaged tissue. Once the dead tissue is removed, a bone graft material may be added to fill the space. This surgery is minimally invasive and uses a very small incision. Recovery usually involves several weeks of no- or limited weight bearing. Patients generally recover quickly and report improved pain and function.
  • Bone graft – Surgery to treat AVN may include a bone graft to replace and rebuild damaged bone. This involves transplanting healthy bone tissue from another part of the body (autograft) or from a donor (allograft). Artificial material may also be used. If cartilage is damaged, the graft may include both bone and cartilage (osteochondral graft). In some cases, blood vessels are transplanted along with the bone tissue. This is called a vascularized bone graft and can help improve blood supply to the joint. In AVN, a bone graft is most often used along with core decompression.
  • Arthroscopy – Arthroscopy is a type of minimally invasive surgery that uses a tiny camera and thin surgical instruments inserted through small incisions. For patients with AVN, arthroscopy may be used to repair torn cartilage, smooth the surface of the bone, or remove loose pieces of tissue in the joint. This can help with symptoms such as pain, stiffness, and “catching” of the joint.
  • Osteotomy – This surgery is used to reshape or reposition the bone to reduce the amount of weight on the damaged area. In this procedure, a wedge of bone is removed so that the bone can be rotated to change the load on the bone. Plates, staples, or screws hold the bone in its new position for healing. An osteotomy may help prevent joint collapse so that joint replacement surgery can be avoided or delayed.
  • Arthroplasty (Joint Replacement) – Joint replacement surgery may be needed if damage is severe. This surgery involves removing the damaged bone and replacing it with an artificial joint. Some young patients will need joint replacement after joint collapse. However, joint replacement is also common in adult survivors who have arthritis or worsening joint function years after treatment ends. Patients who have joint replacement at a young age will likely need additional surgeries in the future. Early diagnosis and management of AVN is important to help prevent or delay joint replacement surgery.

Dealing with AVN - Tips for Patients and Families

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

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