0:01

Here we have a child who presented

0:03

with left hip pain, uh, and fever.

0:07

So I have three images here

0:09

for you, or three sequences.

0:10

The image on the left is a

0:13

coronal T1 fat sat post-contrast.

0:16

That image in the middle is actually the same.

0:18

Let me bring up this one, which is an STIR.

0:20

Let me zoom up a little.

0:21

So this STIR is a fat-suppressed fluid

0:23

sensitive sequence, which demonstrates

0:25

again in the area of abnormal

0:27

enhancement, there is a lot of edema.

0:29

So this extends to the acetabular tectum.

0:32

Not really a lot of joint effusion

0:34

associated, and it sort of stops in

0:36

the region of the triradiate cartilage.

0:39

Here are the axial post-contrast images.

0:41

Going through the similar area shows

0:43

that, indeed, there is quite a bit of

0:45

enhancement, and even a little bit of

0:47

periosteal reaction here at the periphery.

0:50

You have the normal side on the right for

0:51

comparison, showing that, really, there

0:53

should be nothing here at the periphery.

0:55

Inflammation happening here.

0:57

So, the first thought when you

0:58

see this, especially with that

1:00

history, should be infection.

1:03

Indeed, this is what this ended up

1:04

being; this ended up being osteomyelitis.

1:06

And the reason I'm showing this case is

1:08

because it proves, or it suggests, one of

1:11

the key teaching points in the pediatric

1:13

population is that stuff around cartilaginous

1:16

margins, such as the triradiate cartilage,

1:19

should be treated as a metaphyseal equivalent.

1:21

So this area really is a metaphyseal equivalent.

1:24

And why is that important?

1:26

It's because the metaphysis is

1:27

a very richly vascular area.

1:30

There's an area where the flow is very, very

1:32

slow, and if there is an infection that's

1:36

hematogenously being spread, the metaphysis

1:39

is a great location for it, and because

1:41

this portion of the pelvic bone is a

1:44

metaphyseal equivalent, this is also a

1:46

great place for infection to embed itself.

1:49

So, I want to leave you with one other thought.

1:53

Anytime I see inflammation in the pelvic

1:57

area, around the sacroiliac joints, around

2:00

the pelvis, I also think of another diagnosis,

2:03

which is coming up more and more now, and

2:05

that's called chronic recurrent multifocal

2:07

osteomyelitis, or CRMO.

2:13

The name says osteomyelitis, but it

2:15

really isn't a bacterial infection per se.

2:19

It's more of a chronic,

2:20

uh, inflammatory process.

2:22

Some people think it's

2:23

autoimmune, not really sure.

2:25

But when I see a lesion like this, I say,

2:28

probably osteomyelitis, but in the back of

2:30

your mind, consider, could this be CRMO?

2:33

If you think it's CRMO,

2:35

look for other lesions.

2:36

Oftentimes, these CRMO lesions will

2:38

have lesions in the contralateral side,

2:41

uh, around the sacroiliac joints, around

2:44

the hips, and in the vertebral bodies.

2:47

But just because you don't see

2:48

it doesn't mean it's not true.

2:51

If CRMO is suspected,

2:53

oftentimes you'll need to get a whole

2:54

body MRI to look for other lesions.

2:56

And the treatment is completely

2:58

different for those two entities.

3:00

Oftentimes, CRMO needs a biopsy to

3:02

diagnose. Infection may

3:06

need a biopsy also if it's not being, if

3:08

it's not being treated well or it's not

3:10

responding properly to antibiotic therapy.

3:13

But this ended up being osteomyelitis,

3:15

but it easily could have been a

3:17

condition called CRMO.