Osteochondroma (dr. mahesh)

Cartilage caped Exoxtosis (Osteochondroma)

1. OSTEOCHONDROMA DR. MAHESH CHAUDHARY PHASE-A RESIDENT RADIOLOGY & IMAGING BSMMU

2. DEFINITION Other names: Cartilage caped exostosis Osteo -cartilaginous exostosis Osteochondroma is a bony exostosis projecting from the external surface of a bone It is usually has a hyaline lined cartilaginous cap The cortex and spongiosa of the lesion merge with that of the parent bone

3. GENERAL CONSIDERATIONS When the lesion is seen in a single bone , it is called solitary osteochondroma If two or three bones are involved , with no familial history , the condition is known as multiple ostechondromas Widespread ostechondromas are associated with a positive familial history, and the condition is known as Heriditary Multiple Exostosis ( diaphyseal aclasia ) Usually occurs in bones preformed in cartilage

4. INCIDENCE Most common skeletal growth tumor Approximate incidence is 50% of all benign bone tumors Male : Female ratio 1:1 (?2:1) Most are encountered in childhood and adolescence Usually follows minor trauma Many cases may not be diagnosed due to the silent nature of the disease

5. PATHOPHYSIOLOGY Osteochondromas are developmental lesions rather than true neoplasms These lesions result from the separation of a fragment of epiphyseal growth plate cartilage , which subsequently herniates through the periosteal bone cuff The mechanism likely results from the remodeling during growth of the long bone. Persistent growth of this cartilaginous fragment and its subsequent enchondral ossification (maturation) result in a subperiosteal osseous excrescence with a cartilage cap that projects from the bone surface. Osteochondromas enlarge from growth at the cartilage cap After adolescence and skeletal maturity, osteochondromas usually exhibit no further growth.

6. The development of an osteochondroma , beginning with an outgrowth from the epiphyseal cartilage Histology: Covered by thin layer of periosteum . Binucleate chondrocytes in lacunae. Contains hyaline cartilage , bony tissue & normal bone marrow particle.

7. LOCATION (common) BONE PERCENTAGE Femur 34 Humerus 18 Tibia 15 Pelvis 8 Scapula 5 Ribs 3

8. UNCOMMON SITES (17%) Metacarpals Condylar process of the mandible Base of the skull Talus Calcaneus Spine Distal end of the clavicle

9. TYPICAL INVOLVEMENT Spine lesions are typically located at the secondary ossification centres Scapular involvement is seen at Inferior angle Superior angle Coracoid process Pelvic involvement is most commonly near the Anterior superior iliac spine Ischiopubic synchondrosis Large enough lesions are termed as cauliflower exostosis Anterior aspects of the ribs are most commonly involved

10. TYPES TYPE SESSILE PEDUNCULATED Incidence Uncommon Common Location Proximal humerus and scapula Knee , hip and ankle Appearance Flat plateau like stalk producing a broad based protuberance Elongated bony stalk merging with the host bone The hyaline cap is lobulated giving its appearance

11. SESSILE VARIANT Solitary Osteochondroma Lateral radiograph of a sessile osteochondroma of the distal femur.

12. PEDUNCULATED VARIANT Solitary osteochondroma Lateral radiograph of a pedunculated osteochondroma of the distal femur.

13. CLINICAL FEATURES Most are asymptomatic Symptoms arise as a result of their Location: Tendon or nerve irritation Size Pressure effects on adjacent structures Usual complaint is hard palpable mass

14. COMPLICATIONS COMPLICATION PERCENTAGE Fracture 7 Deformity 23 Vascular injury 7 Neurological compromise 10 Adventitious bursae formation 27 Mechanical irritation 10 Malignancy ( Solitary / HME ) <1 , > 10

15. RADIOLOGICAL INVESTIGATIONS

16. X - RAY PENDUNCULATED VARIANT Knee is the most common location Metaphysis is the common site of involvement Lesion has a slender stalk with a cartilaginous dome The cartilage may show dense amorphous / spotty calcification COAT HANGER EXOSTOSIS : The lesion invariably point away from the joint due to muscle pull

17. X - RAY SESSILE VARIANT Creates a broad based exostosis lacking an elongated projection Causes a long asymmetric elongation of the bone Amorphous , spotty calcification is absent Occur at the metaphyseal – diaphyseal region

18. ULTRASONOGRAPHY Ultrasonography can be applied to analyze the cartilaginous cap of an osteochondroma. The cap appears as a hypoechoic layer covering a hyperechoic underlying bone. Ultrasonography is also valuable in the diagnosis of bursitis and other complications associated with osteochondromas , such as arterial or venous thrombosis, as well as aneurysm and pseudoaneurysm formation.

19. X-ray AP of left thigh USG of the left thigh above the lump

20. MRI MR imaging is the best radiologic imaging method evaluating hyaline cartilage cap. The high water content in non mineralized areas of the cartilage cap has intermediate to low signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Mineralized areas in the cartilage cap had low signal intensity on T1 and T2-weighted images In young patients with active growth and maturation from normal enchondral ossification in the cartilage cap may be marked heterogeneity both T1-weighted images and T2-weighted images because of the mixture of non mineralized and mineralize cartilage tissues.

21. Selected T1 and T2 weighted images shown above demonstrate a broad based exophytic lesion of bone. The marrow space of the bone and the lesion are contiguous. There are areas of T2 brightening at the periphery of the lesion, but without frank invasion of the surrounding tissues.

22. C.T. SCAN Allows optimal demonstration of the pathognomonic cortical and medullary continuity of the lesion and parent bone Mineralization in the cartilage cap allows a correct CT measurement   However, it can be very difficult to correctly measure the thickness of a totally nonmineralized cartilage cap because it cannot be easily differentiated from surrounding muscle or bursa. Cartilage cap thickness greater than 1 to 2 cm in adults and 2 to 3 cm in growing children suggests malignant transformation

23. CT through the proximal tibia showing a tibial osteochondroma (arrow) causing marked thinning of the adjacent fibula (arrowhead).

24. Multiple osteochondromatosis . Nonenhanced , axial computed tomography (CT) scan through the pelvis. Note the fragmentation of the osteochondroma and the considerable soft-tissue mass.

25. MALIGNANT TRANSFORMATION CLINICAL Growth of lesion after skeletal maturity Pelvis / shoulder (mostly sessile variety) < 1 % in solitary , > 10% in HME Increasing mass and pain at the site of lesion in absence of fracture, bursitis or nerve compression

26. MALIGNANT TRANSFORMATION RADIOLOGICAL Visualized cartilage cap measures >2 cm in adults and >3 cm in children Bone destruction Dispersed calcification in cartilaginous cap Soft tissue mass Altered appearance on sequential studies Increase uptake in bone scan ( Unrelaible )

27. Associations and Syndromes Hereditary multiple exostoses ( diaphyseal aclasis ) Autosomal dominant condition Short stature Multiple osteochondromas Asymmetric growth at the knees and ankles Risk of malignant degeneration is about 10% & often around the hip

28. Dysplasia epiphysealis hemimelica ( DEH, Trevor’s 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

29. Enchondromatosis ( ollier disease) Nonhereditary abnormality in which multiple enchondromas are present. Many lesions become stable at puberty. Risk of malignant transformation to chondrosarcoma is 25%. Radiographic Features • Multiple radiolucent expansile masses in hand and feet • Hand and foot deformities • Tendency for unilaterality

30. Imaging Differential diagnosis Hands- Bizarre parosteal osteochondromatous proliferation (BPOP) Does not have cartilaginous cap . Seen in hands and feet. Continuity between the lesion and underlying bone is not found Bony growth projecting into soft tissues .

31. Humerus - Supracondylar spur : Anatomical variant present in ~1% of the population Usually asymptomatic Considered if patients present with symptoms of median nerve compression and there is no pathology on imaging of the carpal tunnel. a bony spur projecting antero - medially from humeral metadiaphysis ( towards elbow joint )

32. Osteochondromatous Variants Dysplasia epiphysealis hemimelica Subungual exostosis Turret exostosis Traction exostosis (at tendinous attachments) Bizarre parosteal osteochondromatous proliferation = Nora lesion Florid reactive periostitis

33. Treatment No treatment necessary for asymptomatic osteochondromas (Observation) 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

34. REFRENCES BOOKS: Text book of Radiology & Imaging: David Sutton Essentials of Skeletal Radiology: Yochum and Rowe Bone and Joint Imaging : Resnick WEB: http://radiopaedia.org/articles/osteochondroma http :// www.learningradiology.com/archives2007/COW%20243-Osteochondroma/osteochondromacorrect.html

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