0:00

MRI pathology,

0:01

and a 14-year-old,

0:02

with a football injury one week ago.

0:05

I can't believe this kid has been walking around

0:08

with this for seven days.

0:10

I'm going to be focusing on the corners,

0:13

so I'm not going to take you through

0:14

my standard search pattern,

0:16

where I go from the patella to the cruciates,

0:18

to the collaterals, et cetera.

0:19

I'm going to go right to the corners

0:21

in each projection

0:22

so that I can teach you how to evaluate corner injuries

0:26

using the 3 orthogonal projections,

0:29

axial, coronal, and sagittal.

0:31

So, let's start axial.

0:33

The first thing you might notice,

0:35

and probably one of the easiest things to latch onto

0:38

is the tibial collateral ligament,

0:40

also known as the middle layer of the MCL.

0:42

It looks rather swollen and boggy and irregular.

0:46

Then we follow it back a little bit,

0:47

and we're in the POL,

0:49

the posterior oblique ligament,

0:51

and then that becomes the OPL,

0:54

or the oblique popliteal ligament,

0:56

that goes across to the lateral side.

0:58

So, not a lot of swelling here in the back

1:00

on the posteromedial side,

1:02

swelling in the MCL area,

1:04

middle layer.

1:05

But we're here to talk about the corners.

1:08

So, we're staying in the back right now.

1:09

So let's go over to the back on the lateral side.

1:12

And probably the first structure we ought to try

1:15

and latch onto is the fibular collateral ligament.

1:19

So, you find the popliteus hiatus.

1:21

Let's go to the hiatus in the coronal.

1:24

And then,

1:25

you find the fibular collateral ligament just above it.

1:28

And so here is your FCL,

1:31

and then you could follow your

1:32

FCL down and around.

1:33

It's probably not that easy because it's a T2,

1:36

so everything's kind of dark,

1:38

but there is a fair amount of swelling

1:40

in this location.

1:41

Now, how about the posterolateral tissues

1:46

behind the condyle and the tibial plateau?

1:49

They're also a little swollen.

1:51

And the crystal clear linear OPL

1:55

becomes a little hazy,

1:56

hot and humid, and difficult to pick out

1:59

as we move from medial to lateral.

2:02

So, we potentially have a problem.

2:04

While we're here,

2:06

we should analyze the cruciates,

2:08

which we can do quickly.

2:09

On the lateral side is the ACL.

2:11

It should be a very crisp,

2:13

linear structure running in this direction.

2:16

We don't have it.

2:17

All we have is some irregular mixed

2:19

signal intensity.

2:20

The ACL is gone.

2:21

How about the PCL?

2:22

It should be a round, black structure.

2:25

We'll make it a little brighter and crisper for you.

2:27

It is a round, black structure.

2:29

Let's follow it down.

2:30

Let's follow it up.

2:32

So odds are we have a PCL,

2:34

we don't have an ACL.

2:36

We have a problem with the MCL,

2:39

but perhaps not with the posteromedial corner.

2:42

And we've got some serious swelling in the

2:45

posterolateral corner, right at the joint line.

2:48

So now let's go to the coronal.

2:50

So as we scroll the coronal,

2:52

the first thing I do is I look at the bone injury pattern

2:55

to see if it was a knee dislocation

2:58

or a pivot shift, or a valgus twist,

3:01

or a varus twist,

3:03

or a varus hyperextension.

3:05

And I have an impaction injury with depression of

3:09

the lateral femoral terminal sulcus

3:11

in this 14-year-old with, by the way,

3:14

open growth plates.

3:15

You should comment on that.

3:17

The injury is depressed,

3:19

which suggests that it's a more violent

3:21

type of injury and it is non-kissing.

3:25

It is a compression or depression-type infraction

3:29

or fracture of the femoral terminal sulcus,

3:31

but it's non-kissing with this lesion in the back,

3:34

this tibial lesion.

3:36

Now, let's go over to the sagittal projection

3:38

for a minute.

3:39

Because this tells you you've had

3:41

a component of a pivot shift injury.

3:44

You've got the depressed femoral terminal

3:46

sulcus fracture, and it is non-kissing.

3:49

In other words, in the neutral position,

3:51

it is not touching the posterolateral

3:53

tibial injury.

3:55

So, what else should we check

3:56

for on injury patterns?

3:58

We should make sure there's no avulsion

4:00

of the fibular tip.

4:01

While there's no avulsion,

4:02

there is some edema there.

4:04

And what attaches to that tip?

4:06

The popliteofibular ligament and the arcuate.

4:09

So, we're going to pay close attention to those structures,

4:12

which we see right here in the sagittal projection.

4:15

We'll come back to them.

4:16

Let's go back to the coronal.

4:18

So, the bone injury pattern tells us that

4:20

we have had a pivot shift phenomenon.

4:23

Have we had any valgus or varus component?

4:27

We sure have.

4:28

Look at the medial side,

4:30

the middle layer of the tibial colla-

4:34

of the collateral ligament of the MCL,

4:36

the tibial collateral ligament,

4:38

also known as the superficial component

4:41

of the deep MCL,

4:43

is torn.

4:44

And with it,

4:46

the meniscocapsular attachment is torn,

4:48

layer number three.

4:50

So, that means layer number one has to be torn

4:53

because you can't tear layer two and three

4:56

without tearing layer one.

4:58

So while we're at it,

4:59

let's go back and look at the posteromedial corner.

5:02

Let's go forward first.

5:03

Sorry, let's go forward.

5:05

There's been a massive injury

5:08

of the proximal aspect of the MCL

5:10

and the meniscocapsular attachments.

5:12

Let's go backwards now.

5:14

Let's go posterior.

5:15

That detachment persists.

5:18

And right here,

5:19

we've got a flake of bone that has been pulled off.

5:23

This is known on either the tibial side

5:25

or less commonly, the femoral side,

5:28

as the reverse segond phenomenon.

5:30

In other words, medial capsular rupture,

5:34

which means layer three

5:36

has to be torn because the medial capsule is

5:39

contributing to layer number three of the MCL.

5:43

So, let's work our way backwards now.

5:45

And as we get to the posteromedial corner,

5:49

the MCL, or middle layer of the MCL,

5:55

the tibial collateral ligament, becomes the POL.

5:57

And the POL is uniformly and diffusely swollen

6:03

right at the posteromedial corner.

6:04

There should be a nice, crisp, black edge.

6:07

And you should see linear, clear,

6:10

dark fibers here, and you don't.

6:13

So there is a POL injury,

6:15

a posterior continuation of the

6:18

tibial collateral ligament,

6:19

which some would refer to as layer three.

6:22

Others call it layer two.

6:23

Don't worry about that.

6:25

I consider it layer number three.

6:26

The POL, the posteromedial capsule corner

6:29

has been injured.

6:31

Let's look at the lateral side.

6:34

Let's begin with the fibular collateral ligament.

6:37

There's the origin.

6:38

Let's follow it down.

6:40

We see it has an arc shaped course.

6:43

It will fuse with the biceps femoris.

6:46

Remember, there's a short and a long head,

6:48

an anterior and a posterior component

6:51

to the biceps femoris.

6:53

They fuse to form the conjoined tendon

6:55

along the lateral margin of the fibular head.

6:58

But if we go back to the apex of the fibular head,

7:01

that is where you're going to find the arcuate

7:04

and popliteofibular ligament.

7:06

And right there,

7:06

things look a little bit fuzzy.

7:08

Near the biceps femoris, posteriorly,

7:11

things look okay.

7:12

But here, fuzzy.

7:14

Here, black.

7:15

Fuzzy.

7:16

Black.

7:16

So more towards the apex,

7:18

we've got an apical arcuate

7:21

popliteofibular ligament problem, potentially.

7:26

While we're at it,

7:27

let's take a look at the popliteus.

7:30

There is the popliteus hiatus.

7:32

There's the popliteus tendon.

7:33

We can follow the tendon down, and it's intact,

7:36

although it's a little bit swollen

7:37

at the myotendinous junction,

7:39

but still intact.

7:41

When the tendon tears,

7:43

it will often tear at this myotendinous junction.

7:46

Less commonly,

7:47

will it pull out of the hiatus itself.

7:50

So so far,

7:52

we've cleared a number of structures.

7:54

While we're at it,

7:55

let's look at the oblique ligament that comes

7:57

from the fibular collateral ligament.

7:59

Some people call it the segond ligament

8:01

because it will pull off a flake of bone

8:04

in a varus injury,

8:06

and that is the lateral capsular sign.

8:08

What makes up this structure?

8:11

The oblique ligament coming from the

8:13

fibular collateral ligament.

8:14

I'm going to blow it up a little bit.

8:16

And there's also contributions that come from

8:19

anterior to posterior, from the iliotibial band.

8:23

So, the iliotibial band

8:25

and the oblique ligament coming from the FCL,

8:28

make up this attachment.

8:31

Here are some iliotibial band fibers

8:33

merging with FCL fibers, attaching to the tibia.

8:37

So even though the tibia is a little bit swollen,

8:39

these fibers did not come off.

8:41

We don't have a segond sign.

8:43

We don't have a lateral capsular sign.

8:45

Let's go a little bit more posteriorly now.

8:48

We've already confirmed the integrity of the popliteus,

8:51

but we've already said that we are concerned

8:55

about the limbs of the arcuate.

8:57

Here's the lateral limb.

8:58

It looks a little wavy and irregular.

9:01

And the medial limb blunted.

9:03

Right there.

9:04

It makes an inverted V right here

9:06

that is pulled off a little bit,

9:09

and also it goes nowhere.

9:10

It should go like this.

9:12

I'm going to draw it for you.

9:14

So, let's draw the arcuate.

9:15

You got a vertical limb,

9:17

which you remember from prior vignettes

9:20

is inversely proportional in size

9:21

to the fabellofibular ligament.

9:23

And then,

9:24

you've got an oblique limb that should

9:27

be going this way.

9:27

Now, let's take it away.

9:29

Vertical limb,

9:30

wavy and irregular.

9:33

Medial limb or oblique limb,

9:35

just blunted right there.

9:37

So, we've got an arcuate tear.

9:41

Now, there's a ligament that comes from

9:45

the popliteus tendon to the fibular head

9:48

that inserts right next to this.

9:51

In fact,

9:52

it inserts right here,

9:54

and it is not present.

9:56

You know, it's very hard to see what isn't present.

9:58

That's a piece of it right there.

10:00

So, let's look at the sagittal projection

10:03

to find this popliteofibular ligament

10:06

that sits right next to the arcuate ligament.

10:09

So, here's a sagittal.

10:11

We've got our family of bone injuries again

10:14

that reaffirm the mechanism of injury.

10:17

Here is our lateral meniscus.

10:19

And the lateral meniscus,

10:21

you may remember,

10:22

has a superior fascicle and an inferior fascicle.

10:28

And this is the hiatus.

10:29

And here's the popliteus tendon.

10:32

These fascicles are positioned both deep

10:35

and superficial or more medial and lateral.

10:39

So, you'll have a superficial-

10:41

you'll have a superior and inferior group

10:43

that's more towards the midline.

10:45

And then, they'll continue over

10:46

and you'll have a condensed superior

10:49

and inferior group

10:49

that's more towards the free edge

10:51

of the lateral meniscus.

10:53

So, we should see linear attachments

10:58

that go towards the popliteus and form the hiatus.

11:01

Let's see if we can find them.

11:04

I don't see any attachments.

11:06

I don't see any linear structures

11:08

running backwards like that.

11:10

And to make matters more intense,

11:12

the lateral meniscus is a little forward relative

11:15

to the free edge of the slightly depressed

11:18

fracture of the tibia.

11:19

In other words,

11:20

the lateral meniscus is sliding forward.

11:23

Why is it sliding forward?

11:25

Because those attachments are gone.

11:28

Okay.

11:29

We know our popliteus tendon is still here.

11:32

Here it is in the hiatus.

11:33

Here it is arching down.

11:36

It's got an oblique course into the screen.

11:38

And right here,

11:40

it gives rise to a ligament,

11:42

the popliteofibular ligament.

11:45

So, it should come off and then come right down

11:48

to the fibular head.

11:49

It's coming down.

11:51

But then, we lose it as this fuzzy structure.

11:53

I'm going to make it even bigger.

11:57

There it is.

11:58

And it looks a little bit like this.

12:00

If you have a good imagination,

12:02

you might say,

12:03

okay, then it gets kind of fuzzy in here.

12:06

It's a little squiggled up.

12:08

That's known as the mermaid sign.

12:11

Because it's no longer attached to the fibular tip.

12:15

It's retracting.

12:16

It's corrugated.

12:18

It's ill-defined because it's swollen.

12:20

So, we have a pop fib ligament tear.

12:24

There is one of our arcuate limbs right there.

12:27

That's probably the vertical limb right there.

12:31

Or the lateral limb, the up and down limb.

12:34

It comes down,

12:35

and then it squiggles and it stops.

12:38

That's the proximal component that came off.

12:41

So there is an arcuate tear,

12:42

which we already affirmed in

12:44

the coronal projection.

12:45

Let's scroll it again

12:46

so you can see the arcuate space.

12:49

It's all swollen.

12:50

Here's a little bit of the arcuate there,

12:52

shriveled up.

12:53

There's another piece of the arcuate there sitting,

12:55

hanging by itself.

12:57

And there's a little more,

12:58

then the arcuate is gone.

13:00

Now, let's continue over

13:02

and look at the posterior capsule.

13:04

This is the posterior capsule,

13:06

which also is fused with the OPL,

13:08

the oblique popliteal ligament.

13:11

And it's slightly irregular in its character.

13:13

So, it definitely has taken a hit or an injury.

13:16

But the major injuries are in the attachments

13:20

of the lateral meniscus posteriorly,

13:22

the popliteofibular ligament

13:25

and the arcuate ligaments.

13:27

So, this is a big-time posterolateral corner tear.

13:30

My conclusion would read,

13:32

complex posterolateral corner injury or tear

13:36

with A, pop fib ligament tear.

13:40

B, meniscocapsular detachment posterolaterally.

13:45

C, arcuate ligament rupture,

13:49

medial and lateral limb.

13:50

That's number one.

13:51

Number two, ACL transection.

13:54

Number three, grade three MCL

13:56

with folded corrugated MCL.

14:01

Let's take a look at that.

14:02

Folded corrugated MCL with reverse segond fracture,

14:08

rupture of the medial capsule and POL,

14:11

posteromedial corner injury.

14:14

Number four,

14:16

multiple fractures consistent with

14:18

pivot shift mechanism of injury.

14:20

One of which is depressed 3-4 mm.

14:24

End.

14:25

The rest,

14:26

I'm going to bury in the body of the report.

14:28

Yes, there are more findings in this case.

14:30

There are some other pertinent negatives

14:32

that I probably would bury in the body of the report.

14:34

I put into conclusion

14:35

what I want the clinician to see.

14:37

I put in the body of the report

14:39

what I want other radiologists to know that I saw.