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Osteoid Osteoma in the Foot

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In a prior vignette, I showed you a case

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of osteoblastoma that involved the patella.

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So this case is the younger cousin of

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osteoblastoma, which is an osteoid osteoma.

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It's in a somewhat unusual location because

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if you do have osteoid osteomas in the

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foot, it typically involves your talus,

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and typically near the head-neck junction.

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That's a very, very common

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location for an osteoid osteoma.

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But this one has occurred right here.

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So this is your calcaneus,

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that makes this your cuboid.

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It has a very characteristic appearance.

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There is a central area of low

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density, which is the nidus.

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Surrounded by an area of calcification,

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which is a reaction, sclerosis,

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to the act of inflammation.

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You can see that those signal, or, excuse

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me, the low-density nidus here, again,

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with some, with some calcification.

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And there's also sclerosis

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in the surrounding bone.

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That sclerosis, if you notice, is a little

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brighter, or a little denser, than the rest of

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the trabecular pattern that you see in the bone.

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So that is going to correspond

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to an area of intense edema.

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Here is the coronal view of the same area.

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This is our nidus with an area of

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calcification and surrounding sclerosis.

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Typically, this is where it occurs.

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It occurs at the very edge of the bone.

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Some people think it's a process

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that happens just under the periosteum,

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and I think that's probably true because

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the majority of these lesions, in fact, are

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located very close to the periphery of bones.

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Now if we look at the MRI, I'm going

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to blow this up for you a little bit.

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Look at the entire bone of your cuboid.

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The whole thing is bright, so there's a lot of

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intense inflammatory reaction that this elicits.

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Again, you can see that there is that

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nidus up here at the very periphery.

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The nidus is often much better seen on a CT scan.

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And that's why when we see something that

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may be an osteoid osteoma on MRI, and we're

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unconvinced that we actually see a nidus or

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there's something else that's obscuring the

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nidus, we will recommend the CT scan because

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that is a much better modality to look at

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the bony architecture and the nidus itself.

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MRI is helpful to look at the edema.

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The CT is great to look at the

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bony nidus, and for radiofrequency

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ablation or surgical planning.

Report

Faculty

Mahesh Thapa, MD, MEd, FAAP

Division Chief of Musculoskeletal Imaging, and Director of Diagnostic Imaging Professor

Seattle Children's & University of Washington

Tags

Pediatrics

Non-infectious Inflammatory

Musculoskeletal (MSK)

MRI

Idiopathic

CT

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