0:00

Okay, so before we saw a great example

0:03

of a FOPE lesion, which is a normal

0:04

variant, uh, happens in teenage kids,

0:07

typically in the central portion.

0:09

Now I'm going to show you pathology

0:11

that can mimic a FOPE lesion.

0:13

So here we are looking at, again, a dual

0:16

echo steady state or a gradient sequence.

0:18

We know that because the marrow is very dark.

0:20

We can still see the prolaminar

0:22

appearance of the cartilage, and

0:23

the cartilage is uniformly bright.

0:24

So we know this is a gradient sequence.

0:26

I want to direct your attention to this area

0:28

over here, which is the proximal tibial physis.

0:33

The majority of the physis is still open, as

0:35

can be seen by the bright signal over here.

0:36

Can't appreciate the trilaminar

0:38

appearance as much, but that's

0:39

okay because this is an older kid.

0:41

This kid is, I think, uh,

0:43

13 years old at this point.

0:45

But as we go down, as we sort of follow with

0:48

our, with our marker, we get to this barrier.

0:51

And this barrier is much, much bigger

0:53

than we saw with that FOPE lesion, right?

0:55

That should be a clue that

0:56

this is not quite right.

0:58

Something has happened to this growth plate.

1:01

Something in the past, such that now there's

1:04

been what's called a bony bridge formation.

1:07

We call this a bony bridge.

1:08

Bone tissue bridges the physis.

1:12

Again now, I'm going to the

1:13

other side, it's also bright.

1:15

So that area is normal.

1:16

Normal, normal, normal.

1:18

Bad.

1:18

Normal, normal, normal.

1:19

But as you notice, the normal, as it

1:21

approaches the physis, gets a little narrow.

1:23

That's also a characteristic of this lesion.

1:25

So I'm going to scroll back and forth

1:27

to show you that really is a true thing.

1:29

And again, it's not just this area,

1:31

but it's actually a pretty wide area.

1:33

In fact, you can see that that

1:35

path of that physis, path of that

1:37

cartilage, has actually dipped down

1:40

in the area of abnormality.

1:41

So this is all part of the pathology.

1:44

Okay?

1:44

So here again, as we scroll back and

1:46

forth, now we get to the normal area.

1:48

So as we go to the more peripheral

1:50

locations, this here is normal.

1:53

This is the normal tiny bridges that form.

1:56

You notice how tiny it is, how the,

1:58

how the undulation is not a dramatic

2:00

movement one way or the other.

2:02

As you go back and forth, again,

2:04

you notice here, this is okay.

2:05

It's, it's a little bigger, but again, it's

2:08

not a big, huge, dramatic change, okay?

2:11

As we go back and forth, you can

2:12

see what's normal, what's abnormal,

2:14

and this is definitely abnormal.

2:16

Compare that to the more

2:17

distal femoral appearance.

2:19

Very, very nice.

2:21

Again, centrally, we lose it a little bit,

2:23

but, again, that's where you start to develop.

2:26

Uh, an eye for what normal is here,

2:28

that's normal, even though we don't

2:29

see that trilaminar appearance.

2:31

That's because it's central,

2:32

it's beginning to fuse.

2:33

So I think you get an idea of what

2:36

abnormal and what normal looks like.

2:38

Now the question becomes, what caused this?

2:41

So there are several things that can cause this.

2:44

It has to be remote.

2:45

It's something that happened a while ago.

2:46

This just didn't develop two days ago.

2:49

The two most common things that cause

2:51

pathology in this location are infection.

2:54

The metaphysis, as we mentioned

2:56

before, is a rich bed of vessels.

2:58

Vessels, uh, that have little

3:01

arcades, that are slow-flowing blood.

3:04

So a lot of blood-borne pathogens can embed

3:07

themselves in the metaphysis and cause you to

3:10

have infection; it can cause you to have tumors.

3:13

That can damage the physis, that can

3:15

damage the metaphysis, and when those

3:16

blood vessels are damaged, um, there's no

3:18

longer normal endochondral ossification.

3:21

So this is a disruption in endochondral

3:23

ossification such that a bony

3:26

bridge has now formed between your

3:28

epiphysis and your metaphysis.

3:31

What else can cause it?

3:32

Trauma.

3:33

Oftentimes kids have trauma and any trauma

3:35

that causes injury to the physis, like

3:38

a Salter-Harris injury, and we'll get to

3:40

Salter-Harris in later videos, but a Salter

3:42

Harris injury basically is an injury to

3:45

the physis; it can be just the physis, it

3:47

can involve epiphysis and the metaphysis.

3:51

So as long as the physeal injury has occurred,

3:54

it's a type of Salter-Harris fracture.

3:56

So that can lead, if it's severe

3:58

enough, to this type of pathology.

4:00

I'm going to show you what this looks like.

4:02

So what happened in this kid?

4:03

Fortunately, we have prior imaging.

4:06

Let's go back to the original scan.

4:09

Four years earlier, we have this MR.

4:13

This is a fluid-sensitive,

4:15

fat-suppressed sequence.

4:16

You guys are probably wondering,

4:17

why is the field of view so big?

4:20

Why is this grainy? Why does

4:22

it look like an adult MRI?

4:24

A couple of reasons.

4:25

One, the child is smaller, you know, so you

4:28

have smaller, less tissue. The signal is

4:30

not as great, so we have to give a bigger

4:32

field of view to get adequate signal.

4:34

Number two, oftentimes kids come in with

4:37

vague complaints about knee pain and

4:38

we actually don't know where exactly that

4:40

pain is, so we often have to get a bigger

4:42

field of view just to get an idea of

4:44

where the, uh, where the abnormality is.

4:46

Once we find that out, we can hone

4:48

in on the problem.

4:49

But as we look at this original scan

4:52

for this child who had knee pain, we see

4:54

this abnormal signal involving pretty

4:57

much the majority or entirety of the

4:59

epiphysis and the metaphysis, right?

5:02

Let's look at it on a T1-weighted sequence.

5:05

Uh, I'm gonna zoom this

5:06

up just a little bit more.

5:09

Look at this marrow.

5:10

This marrow is completely abnormal.

5:12

It should be white, it should be

5:14

fatty, and it's completely replaced

5:16

by this gray, dark structure, okay?

5:20

So here's a little tip for you.

5:23

Normal marrow, even if it's

5:27

hematopoietic marrow as opposed to

5:28

fatty marrow, does have 40 percent fat.

5:31

So that normal marrow, even though

5:32

it's hematopoietic, should still be a

5:35

little brighter than adjacent muscle.

5:37

This is not brighter than the adjacent muscle.

5:40

It's about the same, so we know

5:41

that this isn't normal marrow.

5:43

That's one clue.

5:45

But look at this nice clear demarcation.

5:47

Here's normal; here it's not.

5:49

I think that abnormality is really

5:52

striking on the T1-weighted sequence.

5:54

So this ended up being

5:55

lymphoma, lymphoma of the bone.

5:57

That's what happened as far as

5:59

the final pathology.

6:00

So let's now look at, in 2006, a

6:03

year later, how that's progressed.

6:06

I'm going to bring the STIR signal down again.

6:08

Here, again, we see the area of

6:10

abnormality, but look at the physis.

6:11

Look at the normal physis on the right.

6:13

Look at the abnormal physis.

6:14

A lot more undulation has

6:16

developed, a lot more blurriness.

6:18

We can't really appreciate

6:19

the trilaminar appearance.

6:20

Look at the physis above and

6:21

look at this physis over here.

6:23

I'm going to bring a T1-weighted sequence down.

6:27

Again, very, very abnormal.

6:29

Again, low signal here; almost looks

6:31

a little wider than we expect it to.

6:33

Here's the normal physis up here,

6:34

normal physis on the contralateral side.

6:36

I'm going to take you further along to 2007.

6:40

How does that look in 2007?

6:42

Here's a STIR sequence.

6:43

Aha!

6:44

Look at this.

6:45

You can already see the beginnings

6:47

of the physeal bar right over here.

6:49

It's not quite as mature as our original

6:52

image that I showed you, but look at this.

6:53

This is abnormal.

6:55

On the other side, you see these little

6:57

brushes of high signal; that's okay.

7:00

That's normal hematopoietic marrow in a child.

7:03

This is probably not normal if it's an

7:05

adult, but if it's a kid, this is okay.

7:07

This brush-like appearance in the metaphysis.

7:10

Let's look at that on T1.

7:12

See this?

7:12

This is okay.

7:13

These little areas of tongue-like tissue.

7:16

This, you can appreciate, is not

7:18

normal because look how normal it is.

7:21

The shape of the physis is completely abnormal.

7:23

Look how blurry it is over here versus

7:25

the nice sharp margins on either side.

7:28

That is abnormal.

7:29

So this child in 2007 was

7:32

beginning to form a physeal bar.

7:35

Now let's zoom over to

7:36

2008, even more progression.

7:38

That area of edema is slightly less conspicuous.

7:41

Maybe you see a little bit of the growth plate

7:43

better, but again, there's no clear path of

7:48

this bright signal from this side to this side.

7:51

It has a blockade, and that's

7:52

the physeal bar maturing.

7:55

Finally, I'm going to show you some radiographs.

7:57

Let's take a look at 2008

7:59

again, December of 2008.

8:01

You can still see the physis, but

8:03

there are portions that are sclerotic.

8:05

So we know that, remember this is

8:06

a two-dimensional representation

8:08

of a three-dimensional structure.

8:10

So here, even though we do see some areas of

8:12

clearness, we know that's maybe in front of or

8:14

behind an area of physeal bar that's forming.

8:17

So we're seeing through some of it.

8:19

Uh, that's abnormal.

8:21

And this is a leg length study.

8:22

We're trying to see if that physeal bar has

8:25

caused any problems in the patient's leg length.

8:28

And if you look at this, you can see that

8:30

the left lower extremity, if you sort of

8:32

line up the top of the plafond on the right

8:34

side versus the plafond on the left side.

8:36

Let me zoom it up; maybe you can

8:37

appreciate that a little bit more.

8:39

This is clearly higher than this side, so

8:41

it means that the left lower extremity is

8:44

shorter, likely because of that physeal bar.

8:47

Finally, we get to our original

8:48

image that shows our physeal bar.

8:51

I want to do one last thing just

8:53

to give you an idea of what the

8:55

significance of the physeal bar is.

8:57

I'm going to create a MIPS image

9:00

from this sagittal slice sequence.

9:03

Remember this is very thin slices

9:04

obtained in isovolumetric parameters so

9:07

we can create nice 3D reconstructions.

9:10

We are going to create 3D MIPS images.

9:15

Here is the original axial image.

9:16

Here is a reconstructed

9:18

sagittal image on the upper right.

9:20

And the lower right is the

9:21

reconstructed coronal image.

9:23

I'm going to move this bar over

9:25

to the area of abnormality.

9:27

I'm going to turn it so we have a

9:29

nice cross-sectional view of that.

9:31

And here I'm going to turn this a little

9:33

bit, so we're really representing that area.

9:37

So over here, if we change the slice

9:39

thickness, as we do over here with the

9:41

MIPS imaging, I'm going to make it a

9:43

little bigger for you, so you can see.

9:46

So this right here is the area of the physeal bar.

9:50

And this entire gray area is the

9:54

area of the normal physeal cartilage.

9:58

So what the surgeons want to know is what

10:00

is the area of this relative to the area

10:03

of the overall cartilaginous surface.

10:06

And we can take a measurement for you.

10:08

Come down here, go to the freehand

10:10

measurement tool, and all you have to

10:12

do is just go around with your pen, try

10:17

to get all that area as best you can.

10:19

Again, it's an estimate,

10:21

but it's a good estimate.

10:23

So on the lower right-hand screen, you

10:24

may not be able to read it, but it says 0.81

10:27

centimeters squared.

10:29

So now we compare that with the

10:32

overall cartilaginous surface.

10:34

So this one is 22 centimeters squared.

10:39

So they can compare the volumes.

10:41

And I typically report the numbers

10:43

and I don't make any judgments as far

10:45

as, you know, should they do this?

10:46

Or should they do that?

10:47

They can decide, because each surgeon is

10:49

different. Their threshold for, uh, cutting

10:52

the physeal bar or doing an epiphysiodesis, which

10:55

is basically lysing the entire physis, depends

10:58

on age, the amount of, uh, bar that's present.

11:01

So I just report the numbers

11:02

and let the surgeons decide

11:04

individually what they want to do.

11:06

And so this is an example of a physeal

11:08

bar from a previous injury to the physis.