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Nonossifying fibromas (NOFs) are the most common benign bone tumor in children. They occur twice more often in males than in females.
It is estimated that 30% to 40% of people under the age of 20 have NOFs, although few will have any symptoms. NOFs are often discovered by chance when a patient requires x-rays for another reason, such as a sports injury.
NOFs do not become cancerous and they do not spread (metastasize). In most cases, no treatment is necessary because these tumors typically go away on their own when a child is fully grown.
Nonossifying fibromas are made of fibrous tissue and are typically yellow or brown in color. They most commonly occur in the flared end of the lower thighbone (femur) and in the flared upper or lower ends of the shinbone (tibia). NOFs sometimes occur in the smaller bone in the lower leg (fibula), and in the upper arm bone (humerus).
Approximately 8% of people with NOF will have more than one tumor. It is uncommon, however, to have more than two or three tumors except in certain very rare conditions (such as neurofibromatosis or Jaffe-Campanacci syndrome).
Nonossifying fibromas are also known as metaphyseal fibrous defects, fibrous cortical defects, nonosteogenic fibromas, or cortical desmoids.
The cause of NOF is unknown. There are also no known factors that put you at greater risk for the disease, such as genetics, the environment, or traumatic injury.
Most children with an NOF will have no symptoms at all. In many people, the NOF is only discovered because x-rays are taken for some other reason, such as an unrelated injury.
Some patients will have mild swelling and tenderness to the touch over the NOF. A small percentage will report a constant dull ache that is not associated with activity. The pain may be due to the tumor itself, or even due to a crack in the bone (pathologic fracture). These minor fractures can occur because the softer NOFs weaken the overall strength of the bone. A fracture is more likely to occur when the NOF is large.
To diagnose nonossifying fibroma, your doctor will need a complete medical history and will conduct a physical examination. He or she will also order imaging tests, most importantly x-rays.
In an x-ray image, the tumor appears dark with a thin surrounding white rim. Other imaging tests your doctor may order include computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, and bones scans.
Although not always necessary, a CT scan or MRI can show the exact size of the tumor, as well as any change in its appearance over time. These images can also show cortical integrity (how thin the strong outer portion of the bone is in the region of the NOF), or pathologic fracture. A bone scan is sometimes helpful to see if there is more than one tumor.
In most cases of NOF, treatment is not required. If left alone, NOFs stop growing when the adolescent finishes growing. Over time, the NOF will fill in with bone. Most NOFs disappear by the time a person reaches the early 20s.
There are times, however, when treatment should be considered. These include instances of large NOF, particularly in a young child who has a lot of growth left, or when symptoms are present. Large size and symptoms can indicate that the bone is weak and is likely to fracture, even with very little force.
The most common method of treating NOFs is with curettage. In this procedure, the tumor is scraped out of the bone.
After curettage, your doctor will fill the hole with a bone graft - this is bone taken from a donor (allograft) or from another bone in your body (autograft). Your doctor may also use a bone cement mixture to fill the hole.
Most patients return to full activity, even sports, within 3 to 6 months of surgery, depending on the size of the NOF, type of bone graft used, and how quickly the bone heals.
Whether or not treatment is performed, most patients with NOF should return to their doctors regularly for x-rays to make sure the tumor is not coming back or growing.
The long-term outlook for patients with NOF is very good because these tumors resolve with skeletal maturity, do not become cancerous, and rarely recur if treated surgically.
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