0:00

So getting to the meat of things here,

0:02

we're gonna start talking about the MRI of osteomyelitis.

0:06

As you can hear, see here in the slam dunk case of MRI, uh,

0:11

osteomyelitis of the calcaneus.

0:13

Not only do we have the superficial ulcer along the plantar

0:17

aspect of the foot, but we have that, uh,

0:20

ulcer tracking in the sinus track all the way

0:23

to the calcaneus

0:24

with this homogeneous geographic low signal intensity

0:29

abnormality on T one weighted sequences, uh, corresponding

0:33

with high signal intensity on all her stir sequences.

0:37

Um, here showing that osteomyelitis of the calcaneus,

0:41

the advantage of giving intravenous, uh,

0:44

contrast material is shown here.

0:47

And, uh, as this, uh, elucidates much more

0:51

of the associated soft tissue infection here we can see the

0:55

borders of the sinus tract as it extends to the ulcer

0:59

and also to the bone surface.

1:00

But not only do we see that, we see these areas

1:03

of peripheral rim enhancement around non enhancement,

1:07

along the plantar soft tissues, uh, corresponding

1:10

with tracks of infectious involvement

1:13

and even in abscess formation containing several foci

1:16

of air along the medial aspect of the foot.

1:21

So our patients are often not going to be able

1:25

to get intravenous contrast,

1:27

but if they can, the soft tissue involvement of, uh, uh,

1:32

on MRI can be further elucidated.

1:34

Um, so these are just some additional tools that we can,

1:38

if we don't have that, uh, in our armamentarium

1:42

or a patient cannot have intravenous contrast,

1:45

we can use some other tools like diffusion weighted imaging

1:48

to further evaluate this.

1:50

So moving to this case a little bit more, uh,

1:53

difficult to assess.

1:55

When we look at the stir sequence on the, uh,

1:58

short axis view, we can see some more homogeneous signal

2:02

alteration of the toe as all, as well

2:06

as on the sagittal image here.

2:08

However, when we look at the T one weighted sequence, that

2:12

doesn't necessarily look like homogeneous fat replacement

2:16

or marrow replacement in the TT of that great toe.

2:20

And when we look at the axial image here,

2:24

it almost looks like we have intervening areas

2:27

of fat signal intensity in between some areas

2:30

of lower signal intensity.

2:33

So we used to call this reactive osteitis,

2:35

and the panel recommendation is to actually remove

2:39

that from our, uh, lexicon

2:42

because it can be ambiguous

2:44

as we can see osteo in the setting

2:46

of inflammatory conditions such as psoriatic arthropathy,

2:50

as well as um, as well as sapo

2:54

and other inflammatory bone conditions.

2:57

So in its place we are, um, trying to get

3:01

to a different place and determine whether

3:05

or not these are high likelihood

3:08

or low likelihood of osteomyelitis.

3:11

So we may be asking, well,

3:13

how the heck are we gonna do that?

3:15

So let's turn our attention to the soft tissues.

3:18

So always go back to the soft tissues.

3:21

And on our T one weighted sequence here,

3:23

we can see relative maintenance

3:25

of the subcutaneous fat along the plantar surface.

3:28

There is a little bit of skin thickening here,

3:31

but overall there is no convincing skin breakdown in this

3:35

particular case.

3:36

So in this patient,

3:38

I would put this person in the low likelihood

3:42

of osteomyelitis,

3:43

even though there is marrow edema involving

3:46

that distal phalanx of the, uh, grade toe.

3:50

Here's another case. The radiograph already shows the

3:53

ulceration along the plantar aspect of the foot similar

3:57

to our previous case.

3:59

However, when we turn our attention to the MRI,

4:03

we can see the soft tissue irregularity,

4:06

but the T one weighted sequence shows just minimal hypo

4:11

intensity along the most plantar surface

4:15

of the calcaneus.

4:17

This corresponds with some higher signal intensity on our T

4:20

two weighted sequence,

4:22

but again, looking at the soft tissues,

4:24

we still see this abnormal signal alteration in the

4:27

plantar fat pad.

4:28

So that fat pad is now obliterated

4:30

because there is a soft tissue ulceration

4:34

and fibrotic tissue in its place.

4:37

So in this particular case,

4:38

we would put it at a high likelihood

4:41

of osteomyelitis given the adjacent

4:45

soft tissue abnormalities.

4:48

So now that we know, um, the sensitivity

4:51

and specificity of MRI for the detection

4:54

of osteomyelitis is pretty good between 77 to 100%

4:58

for sensitivity and 79 to 100% for specificity

5:03

characteristics that were already mentioned,

5:06

low T one signal intensity, geographic, uh, in appearance

5:10

and emus on T two weighted sequences and stir.

5:14

We also look for that cortical disruption

5:17

and also per sitis.

5:19

But not only can we look at the bones,

5:21

but we can pay attention to the soft tissue changes as well.

5:25

As I already alluded to in this particular example

5:29

of a patient with glenohumeral septic arthritis, we can see

5:34

that there is a large joint effusion with enhancement

5:38

following intravenous contrast material.

5:41

But not only do we have this large joint effusion,

5:43

we have this massive rotator cuff tear, which has allowed

5:47

that communication of the septic arthritis

5:50

into this very large septic bursitis on our T one

5:55

weighted sequences. If we

5:56

Pay attention, we start to see some patchy areas

5:59

of low signal intensity on the, uh, humeral epiphysis,

6:03

along the sup lateral aspect, which is corresponding

6:06

with these areas of slightly higher signal intensity

6:10

on our fluid sensitive sequences compatible with a

6:14

small focus of associated osteomyelitis.