Osteochondroma or Exostosis
Osteochondroma is cartilage capped bony projection on the external surface of a bone, containing a marrow cavity that is continuous with that of the underlying bone.
There are two types of Osteochondroma –
The exact cause of solitary osteochondroma is not known.
The proposed theory is the misdirected growth of a portion of the physeal plate, with lateral protrusion causing the development of the eccentric cartilage capped bony prominence.
Multiple osteochondromas is an autosomal dominant condition and numerous areas of the skeleton are affected. Chromosomal anomalies on 8, 11, and 19 are documented.
Solitary osteochondroma commonly presents between the age of 10 and 20 years, and slight male preponderance is seen.
More than 50% of cases will have a lesion in the metaphyseal region of the distal femur, proximal tibia, and proximal humerus.
Many cases are asymptomatic and are frequently discovered as an incidental radiographic finding.
Other factors that draw attention are localized pain, growth disturbance of an extremity, compromised joint motion, or secondary impingement of the soft tissue.
On examination, there is a bony swelling fixed to the underlying bone.
Multiple osteochondromas are diagnosed at the mean age of 3 years with multiple bony projections.
Many children present with genu valgum deformity, progressive hip dysplasia, and forearm deformity.
Solitary osteochondroma is diagnosed on the plain radiographs of the affected bone.
The lesions are protruding from the host bone on either a sessile or pedunculated bony stalk.
Radiographic is diagnostic of multiple osteochondromas, however, magnetic resonance imaging is indicated in cases suspicious of malignant transformation.
Asymptomatic solitary osteochondroma doesn’t need any active intervention. It needs observation and regular follow up.
Symptomatic lesion either due to pain or impingement on surrounding neurovascular bundles needs excision of the lesion.
In multiple osteochondromas, all symptomatic lesions and lesion producing extremity deformity need surgical intervention.
Solitary osteochondroma is has a very good prognosis with < 0.25% of chances of conversion to the sarcomatous lesion.
In multiple osteochondromas, the chance of malignant transformation is 0.9 to 5% of cases, so long term follow up is indicated.