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54-year-old man,

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reported a few days ago that he had a twisting injury

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and now he can't bear weight.

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Limited range of motion and swelling.

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We're interested in the corners,

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and let's look at the axial projection first,

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which many of you might ignore

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with regard to posteromedial

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or posterolateral corner pathology.

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So, let's get you oriented.

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This would be the medial side.

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We can see the middle layer of the MCL

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standing out quite nicely.

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Behind it is the POL,

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Posterior Oblique Ligament of the knee.

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And that transitions into the OPL,

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which goes across the knee over

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to the opposite side.

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Now, let's go to the joint line on the

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opposite side on the lateral side,

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and things don't look quite right along the

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posterior bony margin on the lateral side.

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They look irregular.

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And if you're experienced,

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you would assume there's a fracture present.

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You'll be able to corroborate that on the series

0:56

of coronals I'm going to show you in a minute.

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How about on the medial side?

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There's something sitting posteriorly

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on both sides, medial and lateral.

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Those are either bone fragments

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or areas of coagulated blood.

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They happen to be bone fragments.

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And let's look at the coronal T1 for a minute,

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because that's where you're going to get

1:15

your best depiction of the fractures.

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There is a depressed fracture in

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the femoral terminal sulcus,

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and there are paired,

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posteromedial and posterolateral fractures.

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So, this patient has had a component of a pivot shift.

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But remember, he reported a twist.

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So if he had a straight valgus injury,

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you'd see rupture of the MCL.

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If he had a straight varus injury,

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you'd see rupture of the FCL,

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or fibular collateral ligament.

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And we're able to identify that structure,

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both in the coronal projection

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and in the sagittal projection.

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Here it is right here.

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That is the fibular collateral ligament.

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That's the popliteus, that's the FCL.

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The next layer out.

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And then, the next layer out is the long

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and shorthead of the biceps femoris.

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One, two, three.

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So here in the coronal projection,

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we have popliteus,

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fibular collateral ligament,

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and then biceps femoris.

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One, two, three.

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Because this patient has had a twist,

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as opposed to a varus or valgus,

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we have to be worried about the corners.

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And we are,

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that's why we're showing the case.

2:25

But that also explains why you have a

2:27

fibular head comminuted fracture.

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So that tells you a little bit more

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about the mechanism of injury.

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And your concern about the corners

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should be heightened.

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Let's briefly take a look at

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the posteromedial corner,

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which has a little bit of swelling

2:43

associated with it.

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The middle layer of the MCL,

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tibial collateral ligament, normal.

2:48

The superficial layer, normal.

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The meniscofemoral ligament, normal.

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The Meniscotibial ligament,

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there it is right there.

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It's visible.

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It's present and accounted for.

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How about the lateral side?

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I think we do ourselves justice by bringing

3:05

down our sagittal projection.

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So let's make that the highlight now,

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and let's blow it up a little bit.

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And let's go to the less affected corner first,

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the posteromedial corner.

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You can see a small fracture.

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There's some cortical disruption,

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a little bit of depression.

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And the semimembranosus is still inserting.

3:30

And I'll stop right there.

3:31

There is a little swelling at the

3:32

meniscocapsular junction.

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That's part of the corner.

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It's a little more swelling as we move

3:37

off towards the lateral side.

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Now there's a lot more swelling,

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but still I want to focus my...

3:43

and concentrate my efforts and discussion

3:45

on the lateral side.

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So, let's keep going.

3:47

There is our posterior cruciate ligament.

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Let's work our way to the lateral side.

3:52

And there is our demolished,

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pulverized anterior cruciate ligament,

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which goes along with our pivot shift injury.

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Could we see it in the axial projection?

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You bet we could.

4:03

We got a lot of information off the axial.

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We could tell we had paired

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fractures in the back,

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which should lead us to the conclusion,

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there's been a serious shift of femur

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relative to tibia

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and the ACL, which should be a linear

4:16

straight structure right here,

4:18

is just a big, gray blob.

4:22

It almost looks like a PCL.

4:24

It's so round.

4:25

So it is totally fibrillated,

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totally pulverized.

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And the patient has had a pretty violent

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pivot shift with rotation.

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So now, let's work our way over to the lateral side.

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PCL is intact.

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And the capsule,

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the posterior capsule,

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which also has fuse to it,

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the OPL is torn superiorly.

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Right there.

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That should attach to that.

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All you see is an area of fuzzy

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gray signal intensity.

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Let's keep going over to the lateral side.

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There's a little more capsule,

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certainly swollen.

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And let's get into our posterolateral meniscus.

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Our posterolateral meniscus has an upper

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attachment and a lower attachment,

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which forms its hiatus.

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These attachments go from superficial to deep.

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So here we are superficial.

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There's a lower attachment.

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There's a nice triangle here.

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Here's an upper attachment.

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Here's another fascicle of the attachment.

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Let's keep looking.

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So, the attachments are still present

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until we get in deep.

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And right there,

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the meniscus appears to float.

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So in deep towards the midline,

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the inferior attachment of the lateral meniscus

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has come undone from the fractured

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posterolateral tibia.

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That by itself is usually not problematic.

5:41

Those will usually heal,

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although occasionally,

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you'll see isolated tears up here,

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of the upper fascicle,

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that allows the meniscus to twist or twirl.

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But we've got much bigger fish

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to fry in this case.

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Let's now look at our popliteofibular ligament.

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Our popliteus tendon,

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which perhaps we see best coronally.

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There it is in the hiatus.

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Let's follow it down.

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There's its arcuate course as it plunges infero,

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anterior, and medial.

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It's intact.

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So we can clear the popliteus,

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but not the pop fib ligament.

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There's the popliteus tendon.

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There is the pop fib ligament.

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And it is swollen, ill defined,

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and demonstrates the mermaid sign.

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Here's our mermaid right here.

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I'm going to draw over our mermaid.

6:32

There's the body of the mermaid,

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and there is the mermaid's tail.

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And now, I'm going to take it away

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so you can see it.

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And now, I'm going to blow it up

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so you can see it even better.

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So, we have a popliteofibular ligament rupture.

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Certainly a high-grade tear.

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Now, what's behind here?

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What's behind the popliteus tendon?

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The arcuate.

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It is a glorious mess.

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This would be the arcuate space right here.

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Here it looks a little more linear or straight.

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But then on the very next cut,

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as we get out more peripherally,

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it turns into a bag of blood and stressed out,

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torn, coiled arcuate complex.

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Let's see if we can identify any of the arcuate

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in the coronal projection.

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Here is a blunted vertical limb,

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the lateral limb of the arcuate.

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And then, there should be an oblique limb that

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comes right from here and courses over this way.

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And now, look at that course.

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It's filled in with blood.

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So, we have an arcuate tear.

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We have a pop fib ligament tear.

7:45

We have an ACL transection.

7:47

We have multiple micro and macrotrabecular

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bone injuries, including real life,

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honest to goodness fractures,

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including the lateral femur

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and the fibular head.

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And relative sparing,

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mild injury of the posteromedial corner,

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sparing of the PCL,

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and I would weave those key points

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into my conclusion.

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The rest of the findings,

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including the soft tissue swelling, et cetera,

8:16

the more minor findings go in the body.

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The only other pertinent negative I probably

8:20

would put in my conclusion is the status

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of the menisci, which were spared.