Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Osteochondroma

Basics
Description
  • 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.
    • Appears as a cartilage-capped bony projection from the metaphysis of long bones
    • Can occur in any bone that develops from enchondral ossification
    • Most commonly occurs in:
      • Long bones, usually the proximal or distal femur, proximal tibia, pelvis, or scapula
      • 10-25-year-old persons (stops growing at skeletal maturity)
  • Growth of the lesions parallels that of the patient.
  • Classification:
    • Solitary osteochondroma (nonheritable)
    • Multiple hereditary exostoses (autosomal dominant):
      • Osteochondromatosis
      • Diaphyseal aclasis
  • 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
  • Multiple hereditary exostoses often is inherited in an autosomal dominant manner.
  • To date, 3 different genetic mutations have been isolated:
    • EXT 1
    • EXT 2
    • EXT 3
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
Signs and Symptoms
  • Symptoms result from pressure on adjacent nerves and muscle and from local irritation.
    • Hard, painless, fixed mass
    • Associated symptoms of tissue or nerve irritation
  • The skeletal deformity is secondary to undergrowth of the affected bones, with narrower bones being affected more seriously.
    • Therefore, the tibia and radius grow longer than the ulna and fibula.
    • This phenomenon produces valgus at the knee, ankle, and elbow in some patients.
Physical Exam
  • Note any hard, painless, fixed mass in the metaphyseal region of the fastest growing bones; the region around the knee is the most common.
  • Height in most patients falls in the low-normal range.
  • Group findings occur in 4 major categories:
    • Local impingement, which may include peroneal palsy and soreness of the muscles about the knee
    • Valgus at knee, ankle, elbow, and wrist (variable)
    • Limb-length inequality
    • ROM may be limited secondary to the presence of the osteochondroma.
  • Physical examination and radiography should confirm the diagnosis.
Tests
Lab
Blood tests are not altered by this condition.
 
Imaging
  • Radiography:
    • Plain films typically depict a compact pedunculated or sessile protuberance of bone.
    • The well-defined lesion projects from the metaphysis.
  • CT scans are helpful in locations that are difficult to image, such as the scapula, pelvis, and proximal femur.
  • MRI scans can be used when a suspicion of malignancy is present.
    • The size of the cartilage cap can be measured (a cap >1 cm is worrisome for malignancy).
    • Symptomatic bursae can be detected with MRI.
    • MRI can detect soft-tissue masses.
Pathological Findings
Normal hyaline cartilage undergoes normal enchondral ossification, occurring on the end of a stalk or ridge of bone.

Differential Diagnosis
  • Surface chondrosarcoma
  • Parosteal osteosarcoma
  • Periosteal chondroma
Treatment
General Measures
  • Local measures or analgesics are indicated for minor aches.
  • Medical treatment:
    • The lesion may be left untreated unless it is symptomatic.
    • It should be followed clinically, because a 1-10% risk of malignant transformation to chondrosarcoma is present in persons with multiple hereditary exostoses  .
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
  • Surgical resection of symptomatic lesions is successful with minimal morbidity.
  • In patients with the multiple hereditary exostoses form of the disorder, new lesions may form in multiple areas, and they may grow.
  • Osteotomies and physeal stapling may be done for angular disturbances.
Follow-up
Prognosis
  • The prognosis is good.
  • The chance of recurrence after excision of a solitary lesion is very small.
  • The risk of malignant transformation of isolated osteochondromas is even lower.
  • Patients with multiple hereditary exostoses have a 1-10% risk of malignant transformation  .
Complications
  • Fracture may occur during the first 3 months after removal of an osteochondroma.
  • Vascular or neurologic injury during surgery may occur if the osteochondroma is associated closely with these structures.
  • 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
  • Reassure the patient about the benign nature of the lesions.
  • 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.

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