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Year : 2005  |  Volume : 15  |  Issue : 4  |  Page : 469-472
Cortical sclerosis with central nidus - report of two cases.


Indraprastha Apollo Hospitals, Sarita Vihar, New Delhi, India

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Keywords: Sclerosis, Osteoma, Neoplasm

How to cite this article:
Pendse N A, Rastogi H, Bera M L, Agarwal G, Gulati Y. Cortical sclerosis with central nidus - report of two cases. Indian J Radiol Imaging 2005;15:469-72

How to cite this URL:
Pendse N A, Rastogi H, Bera M L, Agarwal G, Gulati Y. Cortical sclerosis with central nidus - report of two cases. Indian J Radiol Imaging [serial online] 2005 [cited 2020 Feb 25];15:469-72. Available from: http://www.ijri.org/text.asp?2005/15/4/469/28776

   Introduction Top


Cortical thickening in long bones with central nidus is not infrequently encountered in radiology practice. Radiological features are fairly characteristic for specific cause, though confusion may arise in few cases.

CASE 1

X, a 17 year old male presented with history of pain in the right gluteal region and hip since last one year. Pain was moderate to severe and mostly responded to NSAIDs. There was no history of fever, weight loss or any other constitutional symptoms. MRI of Lumbar spine and SI joints done earlier was normal. X ray of the right Hip joint [Figure - 1] revealed an area of cortical thickening on the medial aspect of superior Femoral diaphysis. Hip joint was normal.

A CT scan [Figure - 2] was preformed and showed the cortical thickening along with a small well defined rounded isodense area within. Subsequent MRI [Figure - 3],[Figure - 4] also demonstrated the cortical thickening and the nidus was clearly visualized.

A diagnosis of Osteoid Osteoma was made on the basis of imaging and patient underwent surgery. Diagnosis was confirmed on histopathology.

CASE 2

Y, a 27 year old male presented with history of moderate left hip pain since 11 months. There was no history of fever or weight loss. On examination restriction of movements of left hip was observed. Rest of the examination was unremarkable.

A plain radiograph of left hip [Figure - 5] revealed mild cortical thickening in the medial aspect of the Femoral neck along with a small radiodense nidus surrounded by radiolucency.

CT scan [Figure - 6],[Figure7] also demonstrated the nidus clearly along with the associated cortical thickening. Bone scan [Figure - 8] showed increased uptake in the region.

An MRI [Figure - 9],[Figure - 10] was performed which demonstrated the nidus and cortical thickening and also showed soft tissue intensity adjacent to the cortex, likely representing synovial thickening and inflammation. Minimal joint effusion was also seen.

A diagnosis of intracapsular Osteoid Osteoma was made on basis of imaging and patient underwent surgery. However histopathological diagnosis was a chronic infective lesion.


   Discussion Top


Osteoid Osteoma accounts for 12% of primary benign skeletal neoplasms (1). Jaffe coined this term in 1935 when he described five cases of benign osteoblastic tumors in which surgery was performed assuming an inflammatory etiology(2).

Osteoid Osteomas typically manifests in young patients ( second decade ) with a striking male predominance. Pain is the usual presenting complaint, classically being worse at night. Nearly 75 % cases respond to salicylates. (3)

Though any bone may be involved in Osteoid Osteoma, more than half of the cases are found in the lower limb ( Femur and Tibia ) with intraarticular lesions being encountered in the Hip. Lumbar spine ( posterior elements ), hand and foot bones follow in frequency.

Edeiken and co workers categorized Osteoid Osteomas into three distinct subtypes : Cortical, Cancellous and Subperiosteal (4).

Cortical Osteoid osteomas are the commonest type with the radiolucent tumor lying in the center of fusiform cortical thickening and sclerosis. The "nidus " may be mineralized and actually be radiodense. The sclerosis is reactive and usually regresses following tumor ablation.

In Cancellous or Medullary osteoid osteomas, the associated cortical sclerosis is less marked and the nidus may not lie necessarily in it's center. Adjoining joint may show changes of synovitis and joint effusion.

The rarest type is Subperiosteal Osteoid Osteoma which is situated adjacent to the affected bone ( typically medial aspect of Femur, hands and feet, especially talus ) and typically produce NO reactive sclerosis.

Cancellous and subperiosteal Osteoid Osteomas arise typically in juxtaarticular or intraarticular location.

Kattapuram et al considered all Osteoid Osteomas occurring at ends of long bones, in or around joints or in bone situated close to capsule or synovium as Intraarticular Osteoid Osteomas (5).

The typical conventional radiographic appearance of a cortical osteoid osteoma is as a characteristic lucent nidus with surrounding florid perifocal reactive sclerosis (1). The sclerosis may be marked enough to obscure the nidus on a single radiographic projection. On maturity the nidus may also be mineralized and appear radiodense. Intramedullary or Intracapsular types provoke much less reactive sclerosis and may be difficult to detect.

Bone scan typically follows plain X rays and demonstrates increased uptake. CT scan findings are similar though the nidus is much better demonstrated. On MRI, apart from the nidus and cortical changes, the associated marrow edema is exquisitely demonstrated ( especially with fat suppression technique ). Also MRI is invaluable in Intracapsular and Subperiosteal lesions as it shows the associated synovial and soft tissue changes and also in Medullary cases where the nidus may be situated

considerably farther than the area of cortical sclerosis. Also in vertebral osteoid osteomas, status of the underlying cord is seen only on MRI.

Angiography has a limited role but can help differentiate osteoid osteomas ( blush ) from Brodie's abscess ( no blush ).

Main differential diagnoses are infection and stress fracture. Sequestered bone fragment in osteomyelitis may be indistinguishable from a nidus. Some studies have stated that the sequestrum in osteomyelitis is off center and inner margin of the lucency is irregular (7). In stress fracture, the lucent line runs either perpendicular or at an angle to long axis of the bone.

In case 2, despite all radiological features ( central nidus, regular inner margin ) favouring Osteoid Osteoma, final diagnosis turned out to be chronic infection.[7]

 
   References Top

1.Greenspan A. Benign bone forming lesions: osteoma, osteoid osteoma, osteoblastoma. Skeletal Radiology 1993 ; 22 : 485-500  Back to cited text no. 1  [PUBMED]  
2.Jaffe HL. Osteoid Osteoma a benign osteoblastic tumor composed of osteoid and atypical bone . Arch Surg 1942 ; 44 : 1004-1025.  Back to cited text no. 2    
3.Healey JH, Ghelman B. Osteoid Osteoma and osteoblastoma. Current concepts and recent advances. Clinical Orthopaedics 1986 ; 207 : 76-85.  Back to cited text no. 3    
4.Edeiken J, DePalma AF, Hodes PJ. Osteoid Osteoma (roentgenographic emphasis ). Clinical Orthopaedics 1966 ; 49 : 201-206.  Back to cited text no. 4  [PUBMED]  
5.Kattapuram SV, Kushner DC, Phillips WC, Rosenthal DI. Osteoid Osteoma : an unusual cause of articular pain. Radiology 1983; 147: 383-387.  Back to cited text no. 5  [PUBMED]  
6.Kransdorf MJ and Berquist TH. Musculoskeletal neoplasms. In Berquist TH (Ed) MRI of the Musculoskeletal System. Third edition. Lippincott-Raven1997. Philadelphia.816-822.  Back to cited text no. 6    
7.Mahboubi S. CT appearance of nidus in osteoid osteoma versus sequestration in osteomyelitis. Journal of Computer Assisted Tomography 1986 ; 10(3) : 457-459.  Back to cited text no. 7    

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Correspondence Address:
N A Pendse
C3/59, First Floor, Sector 31, Noida - 201301
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.28776

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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]

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