0:00

So we're gonna switch gears now

0:02

and begin our discussion of chronic osteomyelitis.

0:06

And as you can see on the right hand image, this is a case

0:10

of a gentleman who had undergone a previous arthrodesis,

0:13

which unfortunately got infected

0:16

and had he had to have a hardware explanation.

0:20

So no questions here.

0:21

There is a ton of periosteal reaction about

0:24

the distal tibia.

0:26

There's been a fibular resection

0:27

and a lot of bony irregularity

0:29

and sclerosis involving most of the hind foot here.

0:34

And for one, for some reason on MRI,

0:37

this periosteal reaction is much more difficult to detect,

0:41

um, until it gets to, uh, when it is so severe

0:45

as it is in this case.

0:48

As we look at the axial images, you can see this extra shell

0:52

of bone that has formed along

0:54

and around the distal tibia on the stir sequences.

0:59

It doesn't have a whole lot of high signal intensity

1:02

and on pre contrast images,

1:04

it's pretty low signal intensity in this setting.

1:07

Post contrast, there is very minimal enhancement, if any,

1:11

uh, following the intra administration

1:14

of intravenous contrast.

1:15

So this is an example of, um,

1:18

just chronic periosteal reaction in the setting

1:20

of chronic osteomyelitis.

1:22

You may be wondering what this, um,

1:25

hyperintensity T one signal intensity

1:27

and hyperintensity T two signal intensity is within the

1:30

middle of the, uh, cavity here.

1:33

And this is actually, uh,

1:35

where the intramedullary rod used to be.

1:38

And this is actually now filled with granulation tissue.

1:42

And one thing to keep in mind is how do we differentiate

1:46

this granulation tissue from an intra osseous abscess,

1:51

which we'll see in a few minutes.

1:53

Is that typically the, um, there should be more

1:57

of a hyper intensity on T one weighted sequences

2:01

or that so-called penumbra, um, that we'd are going

2:05

to associate with an interosseous abscess.

2:08

In addition, after the administration

2:10

of intravenous contrast is a relative lack

2:13

of enhancement in the, uh, region of that, uh,

2:18

granulation tissue, which then su further supports

2:21

that is granulation tissue rather than an intracity abscess.

2:26

And here's a classic Brody's abscess.

2:30

This time in an older patient, he's 65, uh, with a history

2:34

of osteomyelitis that's spreading

2:36

through his patellar tendon radiographically,

2:39

we see this lucency in the center

2:41

of the proximal tibia on the T one weighted sequence hears

2:45

that slightly more hyper intense rim noted

2:49

as the penumbra sign that is associated

2:52

with intero abscesses.

2:54

And this is how this patient got to where he is today.

2:58

Today on our T one

3:00

and uh, T two weighted sequences on the coronal image,

3:03

we can see irregularity

3:05

and, um, kind

3:07

of signal alteration within the proximal patella tendon

3:10

associated with a signal alteration of the inferior aspect

3:14

of the patella as well.

3:16

One focus of osteous with additional

3:20

reactive edema within the infra patella fat pad

3:24

and then horsing down just posterior to the patella tendon

3:28

and then decompressing into this Brody abscess.

3:31

You'll notice the, uh,

3:33

hyperintensity on both your T two fat suppressed

3:37

and also proton density weighted sequences, uh, as the rim

3:42

of the abscess.

3:45

Here is another unfortunate, uh, gentleman who, uh,

3:48

was diabetic and also has HHT presenting with thigh pain.

3:53

The amount of periosteal reaction here is not subtle.

3:57

Um, and as we look at this further with the, uh,

4:01

T one fat suppressed post contrast sequences,

4:04

we see extensive signal alteration along the,

4:07

in almost the entirety of the course of the, uh, medullary,

4:11

uh, medullary portion of the femur

4:14

with associated periosteal reaction.

4:17

So when we have these cases

4:18

of acute ME osteomyelitis involving the medullary, uh,

4:22

cavity, a lot of times there is vascular engorgement edema

4:26

and cellular infiltration as the abscess starts to form

4:30

inside the medullary cavity.

4:32

This creates a lot of intramedullary pressure

4:35

that facilitates its spread through the cortical through

4:40

and to the cortical bone through the Sion

4:42

and Mann's channels.

4:44

And while it's doing this, uh, what can happen is, uh,

4:48

fat globules can be liberated from the bone marrow

4:52

and reach intra, um, osseous and extra osseous compartments.

4:58

So when we turn our attention

4:59

to this T one weighted sequence, we can actually start

5:03

to see some of those fat globules that are, uh,

5:06

have been kind of exuded out of the bone marrow as a result

5:10

of this, uh, osteomyelitis within the medullary cavity.

5:15

This is that same patient.

5:17

Now on the axial images, we can see the degree

5:21

of periosteal reaction

5:23

and also this formation of the cloaca.

5:26

And this is the accepted terminology by the SSR panel.

5:31

And we want to also prevent, uh, you know,

5:36

any ambiguity by suggesting that we

5:40

delete the following, which are, I'll go back,

5:44

cortical breakthrough

5:45

or disruption, which I, I have to say I have been guilty

5:49

of using those words in the past,

5:51

but let's call it what it is.

5:54

And this is a ko. We can see infection

5:57

In the intramedullary cavity coming out this opening

6:01

or cloaca and expanding out into the posterior soft tissues

6:06

as another peripheral multi lobulated ri enhancing

6:10

collection and resulting in extensive p myositis

6:15

of the thigh here.

6:17

The other term that needs

6:19

to be thrown out is pathologic fracture.

6:23

Um, and this is to make sure that, you know,

6:27

not this is not called a pathologic fracture.

6:30

You can still call a pathologic fracture,

6:32

but you really need to see a line going

6:34

through a fracture line

6:36

and in the setting that there is, um, normal use,

6:41

uh, nor normal stresses on this very abnormal bone, um,

6:46

to call that pathologic fracture.