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Year : 2006  |  Volume : 16  |  Issue : 4  |  Page : 589-596
CT and MR images of the flat bone Osteochondromata from head to foot: A pictorial essay


Department of Radiodiagnosis & Imaging, B. J. Medical College, Civil Hospital, Ahmedabad, India

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Date of Submission31-Jul-2006
Date of Acceptance10-Oct-2006
 

Keywords: Osteochondroma, flat bone, CT, MRI

How to cite this article:
Kumar S, Shah A K, Patel A M, Shah U A. CT and MR images of the flat bone Osteochondromata from head to foot: A pictorial essay. Indian J Radiol Imaging 2006;16:589-96

How to cite this URL:
Kumar S, Shah A K, Patel A M, Shah U A. CT and MR images of the flat bone Osteochondromata from head to foot: A pictorial essay. Indian J Radiol Imaging [serial online] 2006 [cited 2020 Jan 18];16:589-96. Available from: http://www.ijri.org/text.asp?2006/16/4/589/32277
Osteochondroma is the commonest benign bone tumor and is a developmental rather than a true neoplasm [1]. It constitutes 10%-15% of all and 20%-50% of benign bone tumors [1]. It can be solitary or multiple, sporadic or hereditary, pedunculated or sessile, symptom less or cause much morbidity by the associated deformity, fractures, neurovascular compromise and malignant change [1].

The typical solitary osteochondroma presents as a slow growing cartilage capped bony excrescence from metaphysis of a long bone typically around the knee, which stops growing after fusion of the growth plate [1].

It is found generally in the long bones as it occurs in areas of endochondral bone ossification - the long tubular bones in 60% (femur 25-30%) and short tubular bones in 10% [2]. However a small percentage is also found in the axial skeleton and other flat bones including skull and facial bones. Scapular (4%), pelvic (5%), and spinal (2%) lesions form the majority of these [1].

The lesions in long bones result from the separation of a fragment of epiphyseal growth plate cartilage, which subsequently herniates through the periosteal bone cuff that normally surrounds the growth plate (encoche of Ranvier)[1].

In the flat bones, osteochondromata usually arise in the parts most recently formed from cartilage, these areas being analogous to the more distinctive metaphyses of the appendicular long bones [2] [Figure - 1]. In the scapula these areas are along the inner border while in ilium these are along the iliac crest and around the acetabulum [2].

Males are affected more than females with a ratio of 1.74:1. However in extremely young, this ratio is equal and increases with age. Females have relatively advanced bone age compared to boys, hence this feature [2]. Age of patients is between 5 -35 years; maximum occurrence is at 5 -15 years of age [2].

Radiographs are generally sufficient for diagnosis and follow up of. Higher imaging modalities are needed when complications arise or malignant change is suspected. In osteochondromas of flat bones with complex anatomy (i.e., pelvis, spine, and scapula) and sessile lesions, the continuity and thus the diagnosis may not be apparent on radiographs alone [1] hence higher imaging may be called upon.

Case 1: Intracranial Osteochondroma of the frontal bone. A 42 year old female patient presented with chronic headache and behavioral changes since last 6 months. Plain radiograph [Figure - 2] showed a lobulated radiodense lesion in the frontal region.

CT showed this lesion to be an extradural, pedunculated lobulated mass attached to the inner cortex of the frontal bone more [Figure - 3] on the left side with a significant intracranial component compressing the brain tissue. The lesion showed the typical arc and ring curvilinear as well as large solid calcified areas along with large soft tissue component [Figure - 4]. The lesion was also involving the left ethmoid sinus [Figure - 5]. There was heterogeneous mild enhancement of the central soft tissue component [Figure - 6].

Intracranial osteochondromas are uncommon, solitary, slow-growing tumors with a reported incidence of 0.1 to 0.2% of all intracranial tumors. Intracranial osteochondroma can occur at any age with a predilection for younger individuals.

Isolated cranial exostoses are very rare, mostly originating from residual rests of primordial cartilage in basilar synchondroses entrapped during endochondral ossification of the skull base hence are generally seen in middle cranial fossa especially on the clivus or in the spheno-occipital synchondrosis [3]. About 15% of intracranial osteochondromas arise supratentorially, typically attached to the falx in a frontoparietal location [4]. They have also been reported to arise from cranial nerves, walls of the ventricles and from the choroid plexus [4]. In some cases the tumors have occurred as components of disorders of generalized mesenchymal neoplasias including Maffucci's syndrome and Ollier disease. Multiple craniofacial exostoses have been found in Proteus syndrome and may produce the "Buckleschdel" or haunched skull.

Case 2: Osteochondroma of the Scapula

A 14 year old boy presented with snapping sensation in the back on internal rotation and abduction of the arm.

Radiograph [Figure - 7] and plain CT scan [Figure - 8] showed a bony outgrowth from the inner surface of the scapula with a wide area of attachment and clear visualization of continuation of cortex and medulla of the scapula in the lesion.

Osteochondroma is the most common primary benign neoplasm of the scapula with an incidence of 4.6% [5]. Usually, it is a single lesion located on the anterior surface of the scapular body. Chondrosarcoma is the commonest malignancy of the scapula hence higher imaging is frequently required for differentiating from the benign exostosis.

Case 3: Vertebral Osteochondroma

A 15 year old male patient presented with gradually increasing backache, paraparesis, sensory loss and bowel and bladder disturbances since one and a half months. Patient did not have any systemic complains and his routine investigations were normal.

Radiographs [Figure - 9],[Figure - 10] of the dorsal spine showed short length lower dorsal scoliosis towards left side with a calcified expansile paraspinal mass in the posterior mediastinum at D8-9 level on the right side. The lesion was involving the posterior elements as well as filling and widening the neural foramina and seemed to abut and scallop the vertebral bodies.

Plain MRI [Figure - 11],[Figure - 12],[Figure - 13],[Figure - 14] showed a lobulated expansile lesion arising from the posterior elements extending from D7 to D10 level. The lesion was involving D7-8 and D8-9 neural foramina and had significant intraspinal component which pushed and compressed the cord. The tumor was heterogeneous, predominantly isointense on T1WI and isointense to hyperintense on T2WI. On surgery the tumor was found to arise from the right transverse process of D8 vertebra.

About 3 per cent of solitary osteochondromas have vertebral and costal origin [6] while they have been said to occur in 7% of individuals with hereditary multiple exostoses [7].

Osteochondromas of costal origin may reach great size and cause marked vertebral erosion without producing signs of spinal cord compression. Spinal cord compression complicating osteochondromas has generally occurred in adolescents or young adults [8]. Tumors that cause spinal cord compression generally arise from posterior vertebral elements or from the heads of the ribs.

Case 4: Pedunculated Osteochondroma of the iliac blade:

A 75 year old male patient presented with a bony hard swelling in the left hip region without any associated pain, neurovascular deficits or systemic complaints.

Radiographs had showed an elongated bony outgrowth from the posterior surface of left iliac wing just below the iliac crest.

Plain CT [Figure - 15],[Figure - 16] scan showed the cortical and the medullary continuation in to the lesion. There was no soft tissue component associated with it.

Case 5: Large cauliflower Osteochondroma of the iliac blade:

A 20 year old male patient presented with a large painless swelling in the left hip region since two years.

Radiograph [Figure - 17] revealed a well defined rounded calcified mass. Bony trabeculae were visualized however no definite attachment site could be seen even on tangential films.

Plain CT scan [Figure - 18] clearly showed the mass to be an exostosis with continuation of the medulla and cortex of the ilium into the lesion. Small cap was present; however no soft tissue component was seen.

Sessile osteochondromas are not common and when present can be very difficult to distinguish from parosteal lesions like myositis ossificans, periostitis, chondrosacomas, chondromas and osteosarcomas [1].

Case 6: Malignant conversion of Osteochondroma of pubic bone

A 36 year old male who was a known case of diaphyseal aclasis presented with increasing pain and swelling in anterior aspect of upper right thigh since one and half months.

Radiograph [Figure - 19] showed a large soft tissue mass with Ill defined calcified areas, in the region of the right pubic bones. The lesion was extending into the pelvis and displacing the obturator fat plane superomedially and pressing upon the bladder. The lesion was also extending into the upper thigh. The lesion seemed to have its epicenter around the superior pubic ramus.

Plain MRI [Figure - 20],[Figure - 21],[Figure - 22] was performed which showed the predominantly soft tissue mass with internal calcifications. The lesion was lobulated with preserved adjacent soft tissue planes and without muscle and visceral invasion. The lesion was iso to hypointense on T1WI and hperintense on T2WI and not suppressed on STIR sequences.

The lesion on histopathology turned out to be low grade chondrosarcoma.

Multiple osteochondromas (osteochondromatosis) [1] generally is found in the syndrome of diaphyseal aclasis which is an autosomal dominant disorder with higher penetration found in males possibly due to altering influences by hormones or X-chromosome based genes.

Three gene loci have been described: EXT1 on chromosome 8q23-q24, EXT2 on 11p11-p12, and EXT3 on chromosome 19p, EXT 1 and EXT2 being the commonest ones involved [9].

The osteochondromas in diaphyseal aclasis are multiple, present in childhood, are commonly sessile and found in flat bones and axial skeleton as a rule rather than exception [1].

Malignant change is seen in 1% of solitary and 3-5% of multiple exostoses [1]. Malignant change rarely occurs before 20 years of age. In diaphyseal aclasis malignance develops by 30 years and is rare after 50 years of age [9]. Solitary Osteochondroma on the other hand becomes malignant at 50-55 years of age. Centrally located lesions are more prone to malignant conversion. The malignancy is generally low grade and solitary [1].

Features that suggest malignancy include: the clinical signs of growth of the mass or pain; radiographic signs of aggressiveness [1] such as (a) growth of a previously unchanged osteochondroma in a skeletally mature patient, (b) irregular or indistinct lesion surface, (c) focal regions of radiolucency in the interior of the lesion, (d) erosion or destruction of the adjacent bone, and (e) a significant soft-tissue mass particularly containing scattered or irregular calcification; a thick cartilage cap more than 1 cm in adults and 3 cm in children or bone destruction; and increased scintigraphic activity in a patient more than 30 years old [10].

CT has been effective in distinguishing benign from malignant lesion with the presence of thick cartilage cap, large soft tissue mass, irregular, central and coarse calcification indicating malignant change.

MRI is however the best imaging modality for tumor extent depiction as well as confirming malignant change and for imaging the complications.

Fast contrast enhanced MRI can reliably differentiate benign from malignant osteochondromas [11] in the mature skeleton with early enhancement and exponential enhancement growth being correlated with malignancy.

Case 7: Malignant conversion of Osteochondroma of the calcaneum

A 20 year old male patient presented with swelling over right heel since one year which had increased in size since one month.

Radiograph had showed an irregularly calcified mass with soft tissue component in the right sole posteriorly. The lesion seemed to involve the right calcaneum posteriorly.

Plain and contrast CT scan [Figure - 23],[Figure - 24],[Figure - 25] showed a large mass in the heel arising from the calcaneum. The mass had ill defined areas of calcification and had large soft tissue component. There was mild enhancement on post contrast study.

Histopathology revealed a moderately differentiated chondrosarcoma.

Osteochondromas occasionally occur in the tarsal and carpal bones; however they are often less apparent [9].

 
   References Top

1.Imaging of Osteochondroma: Variants and Complications with Radiologic-Pathologic Correlation. Mark D. Murphey, James J. Choi, Mark J. Kransdorf et al. Radiographics 2000; 20:1407-1434.  Back to cited text no. 1    
2.Primary bone forming tumours and their relationship to skeletal growth. C H G Price .The Journal of bone and joint surgery 1958: Vol. 40B, No 3: 574 -593.  Back to cited text no. 2    
3.Slepian A, Hamby W B. Neurologic complications associated with hereditary deforming chondrodysplasia: review of literature and report of two cases occurring in same family. Journal of neurosurgery. 1951; 8: 529-535.   Back to cited text no. 3    
4.Matz S, Israeli Y, Shalit MN, Cohen ML. Computed tomography in intracranial supratentorial osteochondroma. Journal of Computer Assisted Tomography. 1981; (1):109-115.  Back to cited text no. 4    
5.Neoplasms of the Scapula. Marcia F. Blacksin and Joseph Benevenia. American journal of roentgenology. June 2000; 174:1729-1735.   Back to cited text no. 5    
6.Vertebral and costal osteochondromas causing spinal cord compression. Jack Twersky, E. George Kassner, Michael S. Tenner, Anthony Camera. The American journal of roentgenology, radium therapy and nuclear medicine 1975; vol 124 no 1: 124 -128.  Back to cited text no. 6    
7.Carmel PW, and Cramer FJ. Cervical cord compression due to exostosis in patient with hereditary multiple exostoses. Neurosurgery. 1968; 28: 500-503.  Back to cited text no. 7    
8.Madigan R, Worrall T, Mc Claine EJ. Cervical cord compression in hereditary multiplc exostosis: review of literature and report of case. Bone & joint Surgery; 1974: 401- 404.  Back to cited text no. 8    
9.Hereditary Multiple Exostoses: A Current Understanding of Clinical and Genetic Advances. J. R. Stieber, B.A., K. A. Pierz and J. P. Dormans. University of Pennysylvania orthopedic journal. 2001; Vol 14: 30-48.  Back to cited text no. 9    
10.Hudson TM, Chew FS, Manaster BJ. Scintigraphy of benign exostoses and exostotic chondrosarcomas. AJR 1983; 140:581-586.  Back to cited text no. 10    
11.Cartilaginous Tumors: Fast Contrast-enhanced MR Imaging1 Maartje J. A. Geirnaerdt, MD, Pancras C. W. Hogendoorn, MD, Johan L. Bloem, MD, Antonie H. M. Taminiau, MD and Henk-Jan van der Woude, MD. Radiology. 2000; 214:539-546.   Back to cited text no. 11    

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Correspondence Address:
S Kumar
42, Nirant Park, Part-1, Opp. Sun-n-Step Club, Thaltej, Post-Ghatlodia, Ahmedabad-380061
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.32277

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    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13], [Figure - 14], [Figure - 15], [Figure - 16], [Figure - 17], [Figure - 18], [Figure - 19], [Figure - 20], [Figure - 21], [Figure - 22], [Figure - 23], [Figure - 24], [Figure - 25]

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