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Year : 2004  |  Volume : 14  |  Issue : 3  |  Page : 335-337
Role of CT and other imaging modalities in osteoid osteoma


Department of Radiodiagnosis and Imaging, and Orthopaedics Surgery, Vardhman Mahavir Medical College and Safdarjang Hospital, New Delhi-110029, India

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How to cite this article:
Grover S B, Jain M, Bansal M. Role of CT and other imaging modalities in osteoid osteoma. Indian J Radiol Imaging 2004;14:335-7

How to cite this URL:
Grover S B, Jain M, Bansal M. Role of CT and other imaging modalities in osteoid osteoma. Indian J Radiol Imaging [serial online] 2004 [cited 2019 Nov 12];14:335-7. Available from: http://www.ijri.org/text.asp?2004/14/3/335/28613
Sir,

We would like to share our experience on the role of CT in the diagnosis of osteoid osteoma and its differentiation from radiologically similar lesions. We encountered a 6-year-old male child, who presented with pain and restricted mobility in the left arm and shoulder. The pain was more intense at night and responded to salicylate therapy. Radiographs of the left arm showed a centrally located, oval, radiolucent area in the proximal end of the left humeral diaphysis with a large central density and surrounding sclerosis [Figure - 1].

Although radiographs were characteristic of an osteoid osteoma, CT was done for further evaluation. CT scans with appropriate reconstruction showed similar features of a well-circumscribed, centrally located lesion, of low attenuation that had smooth, sharp margins and central calcification [Figure - 2] a and b. Furthermore, absence of both periosteal reaction and soft tissue inflammation, ruled out the possibility of infection and supported the imaging diagnosis of osteoid osteoma. Incidental observation of an old fracture was also made.

Treatment by surgical curettage and pathological examination of the resected specimen confirmed osteoid osteoma. Post-operatively, limb mobility recovered satisfactorily and radiographic examination documented adequate resection with healing [Figure - 3].

Osteoid osteoma is an osteoblastic tumor, which was originally described by Jaffe and is known to have distinct histological features, consisting of a central core of vascular osteoid tissue and a peripheral zone of sclerotic bone [1]. The tumor may occur at any age between 7 to 25 years and has a three fold male preponderance. Pain subsiding with salicylates is the hallmark of this entity. The pathogenesis of this pain is believed to be the local stimulation of sensory nerve endings, induced by changes in vascular pressure, which in turn is mediated through the production of prostaglandins by the tumor tissue [1].

The tumor commonly occurs in long tubular bones, followed in frequency by short tubular bones and the spine. Radiographically, the lesion consists of a lucent area representing the nidus, usually measuring less than 1 cm, which is surrounded by bone sclerosis. The nidus may be uniformly radiolucent or contain variable amounts of calcification [1],[2]. CT shows a well-circumscribed small area of low attenuation, representing the nidus, surrounded by a larger area of higher attenuation representing the reactive bone formation [2]. CT has a significant role in confirming the presence of a nidus, in cases where the nidus is not easily demonstrable by conventional radiographs, especially for osteoid osteoma occurring in the spine, osseous pelvis, femoral neck, intra-articular location and bones of hand and feet [1].

The differential diagnoses to be considered in a lucent bone lesion with a central density includes stress fracture, bone island and osteomyelitis. Radiographically, a linear lucent shadow without calcification is characteristic of a stress facture. Enostoses or a bone island, appears radiographically as an ovoid intraosseous sclerotic area with discrete margins, which has radiating spicules continuous with the adjacent trabeculae and is not associated with surrounding lucency [1]. On the other hand, a circular or elliptical radiolucent lesion without calcification that is larger than 2cm is suggestive of a osteomyelitis. [1]. CT can adequately differentiate sequestration in osteomyelitis from nidus in an osteoid osteoma by the following features: the nidus of an osteoid osteoma is centrally located in the lesion and has smooth round margins. On the contrary, the sequestration in osteomyelitis is eccentrically located and the surrounding lucency has irregular inner borders. Adjoining soft tissue inflammation is usually present in osteomyelitis [3].

In the pre-imaging era, angiography had a role to play in confirming the diagnosis of osteoid osteoma [1],[2]. The role of MRI is as yet controversial and continues to be a topic for ongoing debate in the literature [1],[4]. However, in the recent years, Nuclear Medicine has emerged as a powerful modality that plays a specific role in the pre-operative differential diagnosis of osteoid osteoma and cortical abscess. The commonly employed radionuclide techniques include those utilizing Technetium99m and those using Indium111 chloride. During Technetium radionuclide studies, "Double Density Sign" has been observed in patients with osteoid osteoma because of intense technetium scintigraphic activity centrally in the region of the nidus and less intense accumulation of the radionuclide peripherally in the sclerotic bone. In osteomyelitis, uniformly decreased radionuclide uptake is seen on the technetium scintigraphy. Indium111 chloride radionuclide imaging differentiates cortical osteoid osteoma and a cortical abscess by the detection of increased accumulation of the radionuclide in cortical abscess. An osteoid osteoma, on the other hand has not been found to be associated with increased Indium111 chloride accumulation [1].

The treatment of osteoid osteoma is resection of the affected area of the bone. If the intra-operative localization of the nidus prevents limited excision, localization with a CT-guided needle or radioisotope labeling, can facilitate limited resection of the nidus [4]. Recently, percutaneous resection of an osteoid osteoma has been suggested as an alternative to open surgery. The method usually involves drilling the bone under CT guidance. Percutaneously placed electrodes or interstitial laser photocoagulation may also be used for the ablation of osteoid osteoma [1]. Some centres are experimenting with CT-guided radiofrequency ablation [2]

In conclusion, CT has a role in confirming osteoid osteoma by demonstration of the nidus especially in areas difficult to delineate by radiography such as intra-articular regions, small tubular bones and in the spine. The recommended imaging algorithm in a suspected osteoid osteoma therefore is, radiography, followed by CT and radionuclide imaging. CT has a role not only in the differential diagnosis between radiologically similar lesions, but CT can also aid in guiding surgical intervention and facilitating minimal invasion.

 
   References Top

1.Resnick. D. Diagnosis of Bone and Joint Disorders, 4th ed. Philadelphia: WB Saunders Company 2002.   Back to cited text no. 1    
2.Frassica FA, Waltrip RL, Sponseller PD, Ma LD, McCarthy EF. Clinicopathologic Features and Treatment of Osteoid Osteoma and Osteoblastoma in Children and Adolescents. Orthop Clin North Am1996; 27(3): 559-574.  Back to cited text no. 2    
3.Mahboubi S. CT Appearance of Nidus in Osteoid Osteoma Versus Sequestration in Osteomyelitis. J Comput Assist Tomogr 1986; 10(3): 457-459.  Back to cited text no. 3    
4.Bednar MS, Weilnad AJ, Light TR. Osteoid Osteoma of the Upper Extremity. Hand Clin 1995; 11(2): 211-221.  Back to cited text no. 4    

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Correspondence Address:
S B Grover
Department of Radiodiagnosis and Imaging, and Orthopaedics Surgery, Vardhman Mahavir Medical College and Safdarjang Hospital, New Delhi-110029
India
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Source of Support: None, Conflict of Interest: None


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[Figure - 1], [Figure - 2], [Figure - 3]

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