Osteochondroma is the most common benign which accounting for 35% of benign bone tumors. Most of the osteochondromas are not symptomatic but symptoms can occur due to their location and pressure effects.
Osteochondroma is also called osteocartilaginous exostosis.
Osteochondroma can occur as hey may occur as solitary lesions or can be a part of multiple hereditary exostoses, which is most often inherited as an autosomal dominant trait although it can also occur sporadically. Multiple hereditary exostosis lesions show significant variability in size, number, and distribution.
Though benign, malignant transformation to secondary chondrosarcoma has been in less than one percent patients. WHO defines osteochondroma as a cartilage-capped bony projection on the external surface of a bone. Osteochondroma is mostly occurs around the knee and proximal humerus, though it can occur in any bone.
Osteochondroma is of two types pedunculated- the one that has a stalk, or sessile- the one with broad base of attachment. Osteochondroma grows until skeletal maturity; growth generally stops once the growth plates fuse.
In true sense, osteochondromas are developmental abnormality of the cartilage which results in formation of a cartilage capped bony protrusion on the surface of a bone.
The male-to-female ratio is 3:1.
Etiopathology of Osteochondroma
Exact cause of osteochondroma is not known. It is thought to result from herniation of peripheral portion of the physis resulting in is an abnormal extension.
Genetic karyotyping has suggested that genetic abnormalities are associated with these benign growths.
With growth, osteochondroma grows away from the growth plate with time because they are essentially isolated growth plates. They are affected by, and respond to, various growth factors and hormones in the same manner as epiphyseal growth plates and the growth stops with skeletal maturity.
Clinical Presentation of Osteochondroma
Painless hard slow growing swelling is the usual complaint. Pain might occur due to pressure on adjacent tissues like tendon, muscle, or nerve or bursal inflammation or a fracture of the osteochondroma.
A palpable mass is usually the only finding on clinical examination. Long standing lesions may lead to angular deformities of the bone or limb-length discrepancies.
Lesions which occur near the joint may cause restriction of motion. In spine the osteochondroma may lead toand symptoms secondary to cord or root compression
On radiographs, osteochondromas can be sessile or pedunculated (have a stalk). The lesion typically arises from the metaphysis of a long bone, with a stalk that is continuous with the adjacent cortex and is oriented away from the epiphysis.
Sessile lesions demonstrate a flat, plateau-like protuberance.
Usually clinical examination and xay are sufficient to diagnose these lesions. In cases of doubt CT and MRI are excellent imaging modalities.
Most of the osteochodromas are left as such as they do not cause any symptoms.This lesion is almost always operated for its complications which include painful lesion, pressure effects, restriction of motion, compression on adjacent structures, deformity of the bone, fracture of osteochondroma, bursitis and malignancy.
In such cases complete removal of the lesion is sought. An incomplete removal may lead to recurrence.
Osteochondromas need not routinely be removed especially in skeletally immature individuals when the lesion is in proximity to the physis.
Malignant Changes In Osteochondroma
Malignant change in osteochondroma almost never occurs in growing age. As such malignant change is not very common but it does occur in adulthood to the incidence of 1% . An increase in size and pain in adulthood are common symptoms that should alert one to possibility of malignant change in the osteochondroma.
The malignancy associated with osteochondromas is most often chondrosarcoma, although malignant fibrous histiocytoma and osteosarcoma have been reported. osteochondrmas in pelvis, scapula, ribs, spine (Central Lesions) carry a higher risk of malignant transformation.
Treatment is wide excision of the entire lesion with a surrounding rim of normal tissue.
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