General:
Osteoblastic tumour with central core of vascular osteiod tissue (nidus - usually 1-10mm) with peripheral sclerotic reactive bone
10–12% of benign bone tumors
First 2 decades of life in 70%, in children and young adults
Male:female = 1.6:1
50% in femur and tibia
Clinical features:
Hallmark is night pain relieved by aspirin
Plain radiograph:
Radiolucent nidus with thick sclerotic rim
CT:
Low attenuation nidus with possible internal calcification and variable surrounding sclerosis
MRI:
Low-to-intermediate signal T1WI, variable signal on T2WI
Variable enhancement on Gd
May be misleading due to marrow and soft tissue edema
Often leads to misdiagnosis of osteomyelitis, stress fracture, inflammatory arthritis, or aggressive bone tumor
Bone scan:
Bone scan shows double density sign
Oteoid osteoma and osteoblastoma:
OO - Nidus less than 15 mm ; OB - nidus more than 15 mm
Treatment:
CT guided RFA with ot without absolute alcohol
OO of rib:
Most occur posteriorly
Scloliosis
OO of foot:
4% of cases
Most common site is talus
75% juxta-articular
OO of spine:
Most common in neural arch
Most common in lumbar spine
Present with painful scoliosis
Bone scan is most sensitive and almost always positive
After bone scan, perform CT for localization of nidus
MR - not very good tool, variable signal on T1 and T2, most enhance with Gd
References:
1. Hughes et al. Benign primary tumours of the ribs. Clin rad (2006): 61:314-322
2. Lee GK et al. Osteoid Osteoma of the Tarsal Cuboid Mimicking Osteomyelitis. AJR 2004; 183:341-342
3. Rodallec MH et al. Diagnostic Imaging of Solitary Tumors of the Spine: What to Do and Say. RadioGraphics 2008;28:1019-1041
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