An osteoid osteoma is a benign (non-cancerous) bone tumor that usually develops in the long bones of the body such as the femur (thighbone) and tibia (shinbone). Although osteoid osteomas can cause pain and discomfort, they do not spread throughout the body (metastasize).
Osteoid osteomas tend to be small—less than 1.5 cm in size—and they do not grow. They do, however, typically cause a large amount of reactive bone to form around them. They also make a new type of abnormal bone material called osteoid bone. This osteoid bone, along with the tumor cells, forms the nidus of the tumor, which is a clear spot seen on x-rays.
Osteoid osteomas may occur in any bone in the body, but are most often found in the bones of the leg. They are also found in the hands, fingers, and spine. Osteoid osteomas can affect people of all ages but they occur more frequently in children and young adults.
It is not known what causes osteoid osteoma.
Signs & Symptoms
Symptoms of osteoid osteoma include:
- Dull, aching pain that comes and goes during the day
- Sharp pain at night, when the child is at rest
- A limp
Osteoid osteoma can be confused with other diseases such as osteomyelitis, osteoblastoma, Langerhans cell histiocytosis, or a stress fracture. Specific imaging tests need to be performed to ensure an accurate diagnosis.
Diagnostic tests used to diagnose osteoid osteoma include:
- X-rays – An x-ray of the painful area may reveal thickened bone surrounding a small central core of lower density – a distinctive characteristic of the tumor.
- Computed Tomography (CT) scan – A CT scan will commonly show the nidus – or center of the tumor.
- Needle biopsy – A biopsy may be necessary to confirm the diagnosis of osteoid osteoma. In a biopsy, a tissue sample of the tumor is taken and examined under a microscope. The doctor may administer a local anesthetic to numb the area and take a sample using a needle. A biopsy can also be performed as a small operation.
- Other tests – To exclude other possible bone problems such as an infection or malignant tumor, the doctor may order additional imaging studies. Certain blood tests may also be used to rule out an infection.
There are many treatment options available for bone and soft tissue tumors, and some children will need a combination of these therapies.
Many osteoid osteomas will resolve on their own, but it may take several years. If the child is experiencing pain, he/she may benefit from nonsteroidal anti-inflammatory medications or regular analgesics such as aspirin, Tylenol® or ibuprofen.
For children with pain that cannot be relieved by over-the-counter medications, a procedure may be needed.
The gold standard for treating osteoid osteoma is CT-guided radiofrequency ablation (RFA). It is a minimally-invasive, outpatient procedure.
The child is given anesthesia, then CT-guided imaging is used to pinpoint the center of the tumor. A radiofrequency probe is then inserted into the tumor and heated to burn off the tumor. In most cases, one treatment is all that is necessary, but RFA can be repeated if needed.
The procedure takes about two hours, followed by a two-hour recovery period, then the child can return home.
In rare cases, an open surgical procedure called intralesional curettage may need to be performed, which involves scraping out the bone to completely remove the tumor, and filling the space with bone graft material.
If the child’s osteoid osteoma affected the spine, he/she may need additional treatment to reinforce the spine.