Osteoid osteoma of the distal tibia

Case contributed by Dr Francis Fortin

Presentation

Pain in the distal tibia

Patient Data

Age: 25 years
Gender: Female
X-ray

Initial foot and ankle radiographs

Initial radiograph shows well-defined subcentimeter lytic bone lesion in the distal tibia metaphysis (see annotated images below). Though subtle and initially uncommented upon, there is smooth periosteal and cortical thickening of the posterior tibial metaphysis noted on the lateral images.

Annotated image

Annotated radiographs

On the zoomed frontal images, the lytic lesion is highlighted in green. On the zoomed lateral images, the periosteal and cortical thickening are highlighted in green (compare with the normal cortex in blue which tapers in thickness from diaphysis to epiphysis.)

MRI

MRI obtained about 3 months later

Selected images from an ankle MRI show a heterogenous, enhancing, cortically-based lesion in the posterolateral distal tibial metaphysis. There is adjacent bony sclerosis as suggested by hyposignal in the medullary cavity on T1WI pre-contrast images.  There is enhancement in the adjacent bone, periosteum (which is smoothly thickened) and even soft tissues. Osteoid osteoma is the most likely diagnosis, but CT can help better delineate a nidus.

CT

CT roughly 9 months after initial radiographs

CT confirms an approximately 5 mm lytic nidus with central punctate calcification surrounded by sclerotic trabecular, cortical and periosteal reaction. 3D reconstructions depict the undulated, smooth periosteal thickening.

Incidentally, posteromedially to this lesion, there is a sclerotic focus of bone most likely representing an enostosis (bone island).

Case Discussion

The differential diagnosis for a lytic bone lesion is very large. However, when associated with the adjacent inflammatory changes and bony sclerosis, osteoid osteoma becomes the most probable diagnosis in a young patient. Chronic osteomyelitis with a central sequestrum is a very important differential diagnosis consideration.

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Case information

rID: 57933
Published: 22nd Jan 2018
Last edited: 16th Jul 2018
Inclusion in quiz mode: Included

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