Description
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An osteochondroma is a common developmental abnormality of the peripheral growth plate that results in a lobulated outgrowth of cartilage and bone from the metaphysis.
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Appears as a cartilage-capped bony projection from the metaphysis of long bones
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Can occur in any bone that develops from enchondral ossification
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Most commonly occurs in:
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Long bones, usually the proximal or distal femur, proximal tibia, pelvis, or scapula
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10-25-year-old persons (stops growing at skeletal maturity)
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Growth of the lesions parallels that of the patient.
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Classification:
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Solitary osteochondroma (nonheritable)
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Multiple hereditary exostoses (autosomal dominant):
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Osteochondromatosis
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Diaphyseal aclasis
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Synonym: Osteocartilaginous exostosis
Epidemiology
Incidence
No substantial difference in frequency between males and females
Prevalence
This most common benign bone lesion comprises 40% of all benign bone tumors .
Risk Factors
Genetics
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Multiple hereditary exostoses often is inherited in an autosomal dominant manner.
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To date, 3 different genetic mutations have been isolated:
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EXT 1
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EXT 2
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EXT 3
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Etiology
The cause of an osteochondroma most likely is a detached portion of the growth plate that grows on the surface of the bone.
Diagnosis
Osteochondroma Signs and Symptoms
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Symptoms result from pressure on adjacent nerves and muscle and from local irritation.
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Hard, painless, fixed mass
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Associated symptoms of tissue or nerve irritation
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The skeletal deformity is secondary to undergrowth of the affected bones, with narrower bones being affected more seriously.
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Therefore, the tibia and radius grow longer than the ulna and fibula.
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This phenomenon produces valgus at the knee, ankle, and elbow in some patients.
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Physical Exam
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Note any hard, painless, fixed mass in the metaphyseal region of the fastest growing bones; the region around the knee is the most common.
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Height in most patients falls in the low-normal range.
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Group findings occur in 4 major categories:
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Local impingement, which may include peroneal palsy and soreness of the muscles about the knee
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Valgus at knee, ankle, elbow, and wrist (variable)
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Limb-length inequality
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ROM may be limited secondary to the presence of the osteochondroma.
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Physical examination and radiography should confirm the diagnosis.
Tests
Lab
Blood tests are not altered by this condition.
Imaging
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Radiography:
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Plain films typically depict a compact pedunculated or sessile protuberance of bone.
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The well-defined lesion projects from the metaphysis.
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CT scans are helpful in locations that are difficult to image, such as the scapula, pelvis, and proximal femur.
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MRI scans can be used when a suspicion of malignancy is present.
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The size of the cartilage cap can be measured (a cap >1 cm is worrisome for malignancy).
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Symptomatic bursae can be detected with MRI.
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MRI can detect soft-tissue masses.
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Pathological Findings
Normal hyaline cartilage undergoes normal enchondral ossification, occurring on the end of a stalk or ridge of bone.
Differential Diagnosis
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Surface chondrosarcoma
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Parosteal osteosarcoma
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Periosteal chondroma
Osteochondroma Treatment
General Measures
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Local measures or analgesics are indicated for minor aches.
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Medical treatment:
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The lesion may be left untreated unless it is symptomatic.
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It should be followed clinically, because a 1-10% risk of malignant transformation to chondrosarcoma is present in persons with multiple hereditary exostoses .
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Activity
Activity is allowed as tolerated.
Special Therapy
Physical Therapy
Not usually necessary
Medication
Tylenol or NSAIDs may be used by the patient with occasional symptoms.
Surgery
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Surgical resection of symptomatic lesions is successful with minimal morbidity.
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In patients with the multiple hereditary exostoses form of the disorder, new lesions may form in multiple areas, and they may grow.
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Osteotomies and physeal stapling may be done for angular disturbances.
Follow-up
Prognosis
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The prognosis is good.
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The chance of recurrence after excision of a solitary lesion is very small.
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The risk of malignant transformation of isolated osteochondromas is even lower.
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Patients with multiple hereditary exostoses have a 1-10% risk of malignant transformation .
Complications
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Fracture may occur during the first 3 months after removal of an osteochondroma.
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Vascular or neurologic injury during surgery may occur if the osteochondroma is associated closely with these structures.
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Occasionally, the stalk may fracture.
Patient Monitoring
Patients should be followed regularly (for 1-2 years) for angular disturbances, limb-length inequality, or serious problems from pressure of lesion so they can be treated in a timely fashion before more complex intervention is needed.
Miscellaneous
Codes
ICD9-CM
756.4 Osteochondroma
Patient Teaching
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Reassure the patient about the benign nature of the lesions.
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Teach adults to be alert for growth or new onset of pain in osteochondroma, which may be a sign of a malignant transformation.
FAQ
Q: Is it necessary to remove all osteochondromas?
A: In general, if the patient is asymptomatic, surgical removal is not necessary.
Q: What is the risk of malignant degeneration, and are the resultant cancers treatable?
A: The risk of malignancy in an isolated osteochondroma is extremely low, and the prognosis for the resulting low-grade chondrosarcomas is excellent.
Q: How are patients with multiple hereditary exostoses followed to check for malignant degeneration?
A: Patients are queried about new masses or pain. Plain radiographs, CTS, or MRIs can be used to monitor exostosis in the axial skeleton or large lesions in the extremities.