A 16 year old male patient presents with persistent left leg pain. The pain has been increasing in severity for several months, and is no longer relieved with non-steroidal anti-inflammatory medications.
A 3-phase Tc99m bone scan was performed, and the flow/blood pool phases were normal. Delayed phase images of the lower extremities:
Additional imaging included an unenhanced CT scan:
CT demonstrated cortical thickening and periosteal reaction in the posterior aspect of the mid tibial diaphysis, surrounding a lucent intracortical lesion.
An MRI of the left lower extremity was also performed:
The MRI again shows extensive sclerosis and cortical thickening around the lucent lesion, with significant bone marrow edema in the surrounding tibia on STIR images.
This case demonstrates characteristic imaging findings of an osteoid osteoma.
This benign tumor primarily occurs in children and adolescents, and is classically characterized by pain relieved by nonsteroidal anti-inflammatory medications such as aspirin.
Cross-sectional imaging demonstrates a lucent nidus (with or without central calcification) with extensive surrounding sclerosis. A ‘bone irritating’ lesion, osteoid osteoma is often surrounded by bone marrow edema. This case illustrates the “vascular groove sign” on CT images, seen as linear/serpiginous channels representing vessels supplying the highly vascular central nidus. Liu PT, et al. AJR 2011;196:168-73.
Classic appearance on delayed bone scan images is the “double density” sign, with central very intense uptake surrounded by moderately increased uptake. This sign is also well seen in our case.
Radiofrequency ablation is a preferred treatment for osteoid osteoma.
Brant WE, Helms CA, eds. Fundamentals of Diagnostic Radiology, 4th ed. Philadelphia: Lippincott Williams and Wilkins, 2012. Ziessman HA, O’Malley JP, Thrall JH, eds. Nuclear Medicine, the Requisites, 4th ed. Philadelphia: Elsevier, 2014. Helms CA, et al. Radiology 1984;151:779-84.
