Osteochondroma represents a benign bone tumor typically diagnosed during childhood or adolescence that may occur in a solitary form or a multifocal form. The hallmark feature of this tumor is its stalk-like growth on the surface of the bone projecting at nearly right angles to the normal alignment of the bone.
Solitary osteochondroma is considered a developmental abnormality of bone rather than a true neoplastic process. It may be better characterized as a hamartoma or normal growth of normal tissue, in an abnormal location. Thus, an osteochondroma represents a normal growth of a bony exostosis or stalk, capped by a growth of normal cartilage, however growing horizontally away from the bone. It could be described as what would occur when part of the growth plate grows at right angles to its normal expected growth. It is thought to arise during skeletal growth when bone grows away from the growth plate instead of in line with it. This bone outgrowth may or may not have a stalk. When a stalk is present, the structure is called pedunculated. When no stalk is present, it is called sessile.
Solitary osteochondromas are thought to be the most common noncancerous (benign) bone tumor. They account for 35 percent to 40 percent of all benign bone tumors.
Another feature of osteochondroma is its tendancy to grow congruent to the patient's growth. Thus, as the child grows in length, the osteochondroma will grow in its length as well, however because it projects away from the normal growth of the limb, it typically becomes more apparent. Also, as the child goes through a growth spurt, the osteochondroma itself may go through a growth spurt. When the child stops growing, so does the osteochondroma.
The most common symptom of an osteochondroma is a painless mass or bump growing near a joints. The knee and shoulder are more commonly involved however osteochondromas can occur in any bone in the body, including the pelvis and ribs. While the osteochondroma in and of itself does not produce pain, the fact that it projects outward and impinges on other structures such as ligaments, muscles, and tendons, it is not uncommon for patients to complain of pain due to the osteochondroma. Those osteochondromas that impinge on nerves or blood vessels may produce pain and tingling or even numbness that travels well down the length of the limb. Since the growth of the tumor is the same as normal bone growth, if it breaks or gets fractured from an injury, it will produce pain, swelling and possibly deformity, just as any other bone.
A plain X-ray will show the bony growth. The plain film is generally all that is needed for diagnosis however occasionally a CT scan or MRI scan may be ordered in order to study the anatomy of the osteochondroma in better detail. Additionally, the Magnetic Resonance Imaging (MRI) scan may be used to look for cartilage on the surface of the bony growth. The thickness of the cartilage cap can be used to determine the risk of malignant transformation as very infrequently an osteochondroma may transform into a low grade chondrosarcoma.
Osteochondromas are treated based on their propensity to cause symptoms such as pain or deformity. If the osteochondroma is completely asymptomatic or not causing pain, it is not necessary that it be removed. It will need to be monitored with clinical examination and x-rays to ensure that it is behaving as one would expect for an osteochondroma.
When surgery is recommended, the osteochondroma must be removed completely to prevent it from recurring. Since the tumor does lie near the growth plate, there is always a small risk to the growth plat in removing an osteochondroma. Once the child reaches skeletal maturity, the risk to the growth plate is negligible. Following surgery, the child will commonly need to use crutches for lower extremity osteochondromas for up to six weeks or more depending on the size and location of the osteochondroma.
Surgery may be considered if the osteochondroma:
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