What is an osteoid osteoma?

An osteoid osteoma is a type of bone tumor. It isn't cancer (benign). It remains in the same place it starts. It won't spread to other bones or parts of your body.

The center of an osteoid osteoma is the nidus. It consists of growing tumor cells, blood vessels, and cells that over time form bone. A bony shell surrounds the nidus.

Usually, osteoid osteomas are small tumors that measure less than 1 inch across. They typically form in the long bones, especially the thigh (femur) and shin (tibia) bones. They may also develop in the bones of the spine, arms, hands, fingers, ankles, or feet. They can occur in other bones. But that is much less common.

Osteoid osteomas tend to be painful. They may cause a dull, achy pain that can be moderate to severe. The pain is often worse at night.

Osteoid osteomas occur more often in men than in women. They typically occur in children and young adults up to about age 24. But they can occur at any age.

What causes an osteoid osteoma?

Researchers are still working to understand what causes osteoid osteomas to form. They seem to start with inflammation in the bone. When that occurs, blood vessels in the area start to expand and grow. Bone-producing cells called osteoblasts soon start to multiply. They lay down the building blocks for bone. Cells that break down bone, called osteoclasts, also become part of the osteoma. The growing tumor puts pressure on the surrounding bone. This hardens and forms a shell around the tumor.

Often there is no history of injury or infection at the site where the osteoid osteoma forms.

What are the symptoms of an osteoid osteoma?

The most common symptom of an osteoid osteoma is pain not caused by an injury. The pain is often achy and dull. The pain can be intense. It often tends to get worse at night. It may even wake you from sleep. Over-the-counter pain medicines, such as aspirin or ibuprofen, may help ease your pain. Depending on the location, other signs and symptoms can include:

• Curvature of the spine (scoliosis)

• Enlargement or deformity of a finger

• Joint pain and stiffness

• Limping

How is an osteoid osteoma diagnosed?

Many people with osteoid osteomas have pain for months or even years before seeing their healthcare provider. In children, people may assume the pain is from growing pains. Unlike growing pains, physical activity has no effect on the pain of osteoid osteomas.

To find the cause of the pain, your healthcare provider will ask about the nature and severity of the pain. They may also ask:

• If certain things make the pain better or worse

• How long it has been present

• If you have ever been injured in that area of the body

X-rays can help your healthcare provider diagnose the osteoid osteoma. On an X-ray, the bony shell appears white, and the nidus will appear dark.

At times, other imaging studies can help make sure that something else, such as an infection or cancer, is not causing your pain. These studies may include:

• CT scans

• MRI scans

• Bone scans

If your healthcare provider still isn't sure what is causing your pain, you may need blood tests or bone biopsies.

How is an osteoid osteoma treated?

Osteoid osteomas may shrink on their own. But that often takes years. Some people get pain relief from nonsteroidal anti-inflammatory drugs (NSAIDs). Some NSAIDs, such as aspirin, ibuprofen, and naproxen, are available without a prescription. Others are only available by prescription. NSAIDs may speed up the shrinkage of osteoid osteomas. But they can cause problems, such as stomach irritation, ulcers, bleeding, high blood pressure, rash, and ankle swelling. They can sometimes also cause kidney or heart problems.

Because osteoid osteomas can be quite painful and take a long time to go away, healthcare providers often treat them more aggressively. Treatment choices include:

• Surgery

• CT-guided drill resection

• Radiofrequency ablation

If you need surgery to remove an osteoid osteoma, an orthopedic surgeon will do the procedure. You will likely get general anesthesia so that you can sleep through the surgery without feeling any pain. Regional anesthesia, where you only have part of your body numbed, may be a choice if the tumor is in a small bone. You may need to stay in the hospital for several days. You may need to work with a physical therapist even after you go home.

CT-guided drill resections and radiofrequency ablations are less invasive choices. An interventional radiologist can do these procedures. Your care team will use a CT scan to precisely locate the osteoid osteoma. The healthcare provider will then use a special drill or heated probe to remove or destroy it. The procedure can take place under general or regional anesthesia. You may be able to go home in a couple hours afterward. You will still need to limit your activities for a while. But you may be able to return to school or work in a few days.

What are possible complications of an osteoid osteoma?

Osteoid osteomas can be quite painful. A few complications can occur because of swelling linked to the bone and the location of the osteoma. Examples include:

• Scoliosis. This can occur if the osteoid osteoma is in the spine.

• Enlargement or deformity of a bone. This can occur if the osteoid osteoma is in a small bone.

• Deformity or stiffness of a joint. This can occur if the osteoid osteoma is at the end of a bone.

When should I call my healthcare provider?

Call your healthcare provider if you are having pain in your bones that doesn’t go away. You should call right away if you have any of these symptoms:

• Fever over 100.4°F (38°C), or as directed by your provider

• Chills

• Severe pain or your pain suddenly gets worse

• Swelling that doesn't go away or gets worse

• Red, warm, sore skin overlying a bone

• Darkening of your urine after exercise

Key points about osteoid osteomas

• Osteoid osteomas are noncancer tumors of the bone. They won't spread to other bones or tissues.

• Dull, achy pain that gets worse at night is the most common symptom.

• Medical providers don’t know what causes osteoid osteomas.

• They may go away on their own over time. Sometimes they will go away after treatment with NSAIDs.

• Osteoid osteomas commonly need treatment with surgery, CT-guided drill resection, or radiofrequency ablation.

Next steps

Tips to help you get the most from a visit to your health care provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new directions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your healthcare provider if you have questions.