0:01

In a prior vignette, I showed you a case

0:03

of osteoblastoma that involved the patella.

0:07

So this case is the younger cousin of

0:10

osteoblastoma, which is an osteoid osteoma.

0:14

It's in a somewhat unusual location because

0:17

if you do have osteoid osteomas in the

0:20

foot, it typically involves your talus,

0:23

and typically near the head-neck junction.

0:25

That's a very, very common

0:27

location for an osteoid osteoma.

0:29

But this one has occurred right here.

0:32

So this is your calcaneus,

0:35

that makes this your cuboid.

0:37

It has a very characteristic appearance.

0:39

There is a central area of low

0:42

density, which is the nidus.

0:44

Surrounded by an area of calcification,

0:48

which is a reaction, sclerosis,

0:50

to the act of inflammation.

0:52

You can see that those signal, or, excuse

0:54

me, the low-density nidus here, again,

0:56

with some, with some calcification.

0:58

And there's also sclerosis

1:00

in the surrounding bone.

1:02

That sclerosis, if you notice, is a little

1:04

brighter, or a little denser, than the rest of

1:07

the trabecular pattern that you see in the bone.

1:09

So that is going to correspond

1:11

to an area of intense edema.

1:13

Here is the coronal view of the same area.

1:17

This is our nidus with an area of

1:21

calcification and surrounding sclerosis.

1:24

Typically, this is where it occurs.

1:26

It occurs at the very edge of the bone.

1:28

Some people think it's a process

1:31

that happens just under the periosteum,

1:34

and I think that's probably true because

1:36

the majority of these lesions, in fact, are

1:38

located very close to the periphery of bones.

1:42

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

1:44

to blow this up for you a little bit.

1:46

Look at the entire bone of your cuboid.

1:51

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

1:53

intense inflammatory reaction that this elicits.

1:57

Again, you can see that there is that

1:59

nidus up here at the very periphery.

2:02

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

2:05

And that's why when we see something that

2:07

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

2:12

unconvinced that we actually see a nidus or

2:14

there's something else that's obscuring the

2:15

nidus, we will recommend the CT scan because

2:18

that is a much better modality to look at

2:22

the bony architecture and the nidus itself.

2:25

MRI is helpful to look at the edema.

2:27

The CT is great to look at the

2:29

bony nidus, and for radiofrequency

2:32

ablation or surgical planning.