16/10/2021
OSTEOCHONDROMA
General Considerations
- Osteochondroma is the most common benign bone tumor and the most common skeletal neoplasm
+ They account for approximately 35% of all benign bone tumors and 9% of all bone tumors
- They are cartilage-capped bony projections from the external surface of a bone
- They occur only in bones which form by enchondral bone formation and most commonly found around the knee (40%) and shoulder, although they can occur in any bone
- Almost all are diagnosed in patients under the age of 20 with a marked male:female predominance (3:1)
- They grow until skeletal maturity and then stop growing when the epiphyseal plate fuses, although the cartilage cap can continue to grow slowly until about age 30
- Osteochondromas tend to occur near an epiphyseal growth plate and grow away from the physis
Clinical Findings
- Most are diagnosed incidentally
- Or, they may come to clinical attention because they produce a mass
- They are usually asymptomatic
- When painful, they should be evaluated for
+ Mechanical irritation and inflammation of the surrounding soft tissues
+ Fracture of the stalk
+ Avascular necrosis of the cartilaginous cap
+ Malignant degeneration
Imaging Findings
- Conventional radiography is the study of first choice
- CT can be used to determine if the marrow and cortices of the lesion are continuous with the parent bone
- MRI can be used to asses surrounding soft tissues and to measure the thickness of the cartilage cap, which can be important in evaluating for malignant generation
+ A thick cartilaginous cap (>1 cm) in adults should raise the possibility of malignant transformation
- They can vary is size considerably, with the average tubular bone lesion being about 4 cm
- Osteochondromas can either be sessile (flat) or pedunculated (stalk)
- Sessile lesions are more likely to be associated with abnormalities of tubulation of the underlying bone leading to metaphyseal widening or a "trumpet shaped” deformity on x-ray
Malignant Degeneration
- Fewer than 1% of solitary osteochondromas undergo malignant degeneration of the cartilage cap into secondary chondrosarcoma
- It is usually preceded by
+ New onset of growth of the lesion
+ Rapid growth of a lesion, or
+ New onset of pain
- The risk of malignant degeneration increases with an increase in the number and size of the osteochondromas
- In general, a sessile lesion is more likely to degenerate into sarcoma than a pedunculated lesion (exostosis)
Associations and Syndromes
- Hereditary multiple exostoses
+ Autosomal dominant condition
+ Short stature
+ Multiple osteochondromas
+ Asymmetric growth at the knees and ankles
+ Risk of malignant degeneration is 1-20%
- Dysplasia epiphysealis hemimelica (DEH, Trevor disease)
+ Osteochondromas arising in the epiphyses
+ Involve the joint
+ Lesions restricted to one side of the body–either left or right
. May be multiple lesions in a single limb
+ Primarily involves one side of an epiphysis
. Medial side is affected twice as often as the lateral side
+ Usually occurs in infants or young children
Treatment
- There is no treatment necessary for asymptomatic osteochondromas
- The cornerstone of treatment is observation because most lesions are asymptomatic
- If the lesion is causing pain or neurologic symptoms due to compression, it should be resected at the base
- None of the cartilage cap or perichondrium should be left in the resection bed or recurrence can occur.
+ As long as the entire cartilage cap is removed there should be no recurrence
- Patients with many large osteochondromas should have regular radiographic screening exams for the early detection of malignant transformation
