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Knee Case Review: 14Yr old with Posterolateral Corner Football Injury

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MRI pathology,

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and a 14-year-old,

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with a football injury one week ago.

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I can't believe this kid has been walking around

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with this for seven days.

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I'm going to be focusing on the corners,

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so I'm not going to take you through

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my standard search pattern,

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where I go from the patella to the cruciates,

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to the collaterals, et cetera.

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I'm going to go right to the corners

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in each projection

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so that I can teach you how to evaluate corner injuries

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using the 3 orthogonal projections,

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axial, coronal, and sagittal.

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So, let's start axial.

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The first thing you might notice,

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and probably one of the easiest things to latch onto

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is the tibial collateral ligament,

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also known as the middle layer of the MCL.

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It looks rather swollen and boggy and irregular.

0:46

Then we follow it back a little bit,

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and we're in the POL,

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the posterior oblique ligament,

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and then that becomes the OPL,

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or the oblique popliteal ligament,

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that goes across to the lateral side.

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So, not a lot of swelling here in the back

1:00

on the posteromedial side,

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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.

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

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And probably the first structure we ought to try

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and latch onto is the fibular collateral ligament.

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So, you find the popliteus hiatus.

1:21

Let's go to the hiatus in the coronal.

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And then,

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you find the fibular collateral ligament just above it.

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And so here is your FCL,

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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,

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so everything's kind of dark,

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but there is a fair amount of swelling

1:40

in this location.

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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,

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we should analyze the cruciates,

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which we can do quickly.

2:09

On the lateral side is the ACL.

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It should be a very crisp,

2:13

linear structure running in this direction.

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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?

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It should be a round, black structure.

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

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It is a round, black structure.

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Let's follow it down.

2:30

Let's follow it up.

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So odds are we have a PCL,

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we don't have an ACL.

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We have a problem with the MCL,

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but perhaps not with the posteromedial corner.

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And we've got some serious swelling in the

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posterolateral corner, right at the joint line.

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So now let's go to the coronal.

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So as we scroll the coronal,

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

2:55

to see if it was a knee dislocation

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or a pivot shift, or a valgus twist,

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or a varus twist,

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or a varus hyperextension.

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And I have an impaction injury with depression of

3:09

the lateral femoral terminal sulcus

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

3:14

open growth plates.

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You should comment on that.

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The injury is depressed,

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which suggests that it's a more violent

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type of injury and it is non-kissing.

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It is a compression or depression-type infraction

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or fracture of the femoral terminal sulcus,

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

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this tibial lesion.

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Now, let's go over to the sagittal projection

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for a minute.

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Because this tells you you've had

3:41

a component of a pivot shift injury.

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You've got the depressed femoral terminal

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sulcus fracture, and it is non-kissing.

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In other words, in the neutral position,

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it is not touching the posterolateral

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tibial injury.

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So, what else should we check

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for on injury patterns?

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We should make sure there's no avulsion

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of the fibular tip.

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While there's no avulsion,

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there is some edema there.

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And what attaches to that tip?

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The popliteofibular ligament and the arcuate.

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

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which we see right here in the sagittal projection.

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We'll come back to them.

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Let's go back to the coronal.

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So, the bone injury pattern tells us that

4:20

we have had a pivot shift phenomenon.

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Have we had any valgus or varus component?

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We sure have.

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Look at the medial side,

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the middle layer of the tibial colla-

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of the collateral ligament of the MCL,

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the tibial collateral ligament,

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also known as the superficial component

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of the deep MCL,

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is torn.

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And with it,

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the meniscocapsular attachment is torn,

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layer number three.

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So, that means layer number one has to be torn

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because you can't tear layer two and three

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without tearing layer one.

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So while we're at it,

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

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Let's go forward first.

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Sorry, let's go forward.

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There's been a massive injury

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of the proximal aspect of the MCL

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and the meniscocapsular attachments.

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Let's go backwards now.

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Let's go posterior.

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That detachment persists.

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And right here,

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

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This is known on either the tibial side

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or less commonly, the femoral side,

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as the reverse segond phenomenon.

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In other words, medial capsular rupture,

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which means layer three

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has to be torn because the medial capsule is

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contributing to layer number three of the MCL.

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So, let's work our way backwards now.

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And as we get to the posteromedial corner,

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the MCL, or middle layer of the MCL,

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the tibial collateral ligament, becomes the POL.

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And the POL is uniformly and diffusely swollen

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right at the posteromedial corner.

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There should be a nice, crisp, black edge.

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And you should see linear, clear,

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dark fibers here, and you don't.

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So there is a POL injury,

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a posterior continuation of the

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tibial collateral ligament,

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which some would refer to as layer three.

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Others call it layer two.

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Don't worry about that.

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I consider it layer number three.

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The POL, the posteromedial capsule corner

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has been injured.

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Let's look at the lateral side.

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Let's begin with the fibular collateral ligament.

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There's the origin.

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Let's follow it down.

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We see it has an arc shaped course.

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It will fuse with the biceps femoris.

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

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an anterior and a posterior component

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to the biceps femoris.

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They fuse to form the conjoined tendon

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along the lateral margin of the fibular head.

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

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that is where you're going to find the arcuate

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and popliteofibular ligament.

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And right there,

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things look a little bit fuzzy.

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Near the biceps femoris, posteriorly,

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things look okay.

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But here, fuzzy.

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Here, black.

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Fuzzy.

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Black.

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So more towards the apex,

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we've got an apical arcuate

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popliteofibular ligament problem, potentially.

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While we're at it,

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let's take a look at the popliteus.

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There is the popliteus hiatus.

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There's the popliteus tendon.

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

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although it's a little bit swollen

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at the myotendinous junction,

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but still intact.

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When the tendon tears,

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it will often tear at this myotendinous junction.

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Less commonly,

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will it pull out of the hiatus itself.

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So so far,

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we've cleared a number of structures.

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While we're at it,

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let's look at the oblique ligament that comes

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from the fibular collateral ligament.

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Some people call it the segond ligament

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because it will pull off a flake of bone

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in a varus injury,

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and that is the lateral capsular sign.

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What makes up this structure?

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The oblique ligament coming from the

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fibular collateral ligament.

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

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And there's also contributions that come from

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anterior to posterior, from the iliotibial band.

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So, the iliotibial band

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and the oblique ligament coming from the FCL,

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make up this attachment.

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Here are some iliotibial band fibers

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merging with FCL fibers, attaching to the tibia.

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So even though the tibia is a little bit swollen,

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these fibers did not come off.

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We don't have a segond sign.

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We don't have a lateral capsular sign.

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Let's go a little bit more posteriorly now.

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We've already confirmed the integrity of the popliteus,

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but we've already said that we are concerned

8:55

about the limbs of the arcuate.

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Here's the lateral limb.

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It looks a little wavy and irregular.

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And the medial limb blunted.

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Right there.

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It makes an inverted V right here

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that is pulled off a little bit,

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and also it goes nowhere.

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It should go like this.

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I'm going to draw it for you.

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So, let's draw the arcuate.

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You got a vertical limb,

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which you remember from prior vignettes

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is inversely proportional in size

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to the fabellofibular ligament.

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And then,

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you've got an oblique limb that should

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be going this way.

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Now, let's take it away.

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Vertical limb,

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wavy and irregular.

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Medial limb or oblique limb,

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just blunted right there.

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So, we've got an arcuate tear.

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Now, there's a ligament that comes from

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the popliteus tendon to the fibular head

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that inserts right next to this.

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In fact,

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it inserts right here,

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and it is not present.

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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

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to find this popliteofibular ligament

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that sits right next to the arcuate ligament.

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So, here's a sagittal.

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We've got our family of bone injuries again

10:14

that reaffirm the mechanism of injury.

10:17

Here is our lateral meniscus.

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And the lateral meniscus,

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you may remember,

10:22

has a superior fascicle and an inferior fascicle.

10:28

And this is the hiatus.

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And here's the popliteus tendon.

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These fascicles are positioned both deep

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and superficial or more medial and lateral.

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So, you'll have a superficial-

10:41

you'll have a superior and inferior group

10:43

that's more towards the midline.

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And then, they'll continue over

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and you'll have a condensed superior

10:49

and inferior group

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that's more towards the free edge

10:51

of the lateral meniscus.

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So, we should see linear attachments

10:58

that go towards the popliteus and form the hiatus.

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Let's see if we can find them.

11:04

I don't see any attachments.

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I don't see any linear structures

11:08

running backwards like that.

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And to make matters more intense,

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the lateral meniscus is a little forward relative

11:15

to the free edge of the slightly depressed

11:18

fracture of the tibia.

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In other words,

11:20

the lateral meniscus is sliding forward.

11:23

Why is it sliding forward?

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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.

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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.

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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,

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which also is fused with the OPL,

13:08

the oblique popliteal ligament.

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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,

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the popliteofibular ligament

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and the arcuate ligaments.

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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.

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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,

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posteromedial corner injury.

14:14

Number four,

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multiple fractures consistent with

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pivot shift mechanism of injury.

14:20

One of which is depressed 3-4 mm.

14:24

End.

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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.

Report

Description

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Trauma

Musculoskeletal (MSK)

MRI

Knee

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