Interactive Transcript
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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.
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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
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on the posteromedial side,
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swelling in the MCL area,
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middle layer.
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But we're here to talk about the corners.
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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.
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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
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FCL down and around.
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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
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in this location.
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Now, how about the posterolateral tissues
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behind the condyle and the tibial plateau?
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They're also a little swollen.
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And the crystal clear linear OPL
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becomes a little hazy,
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hot and humid, and difficult to pick out
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as we move from medial to lateral.
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So, we potentially have a problem.
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While we're here,
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we should analyze the cruciates,
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which we can do quickly.
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On the lateral side is the ACL.
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It should be a very crisp,
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linear structure running in this direction.
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We don't have it.
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All we have is some irregular mixed
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signal intensity.
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The ACL is gone.
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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.
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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
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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
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the lateral femoral terminal sulcus
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in this 14-year-old with, by the way,
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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
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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
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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
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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.
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That's a piece of it right there.
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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
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that reaffirm the mechanism of injury.
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Here is our lateral meniscus.
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And the lateral meniscus,
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you may remember,
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has a superior fascicle and an inferior fascicle.
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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-
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you'll have a superior and inferior group
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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
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and inferior group
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that's more towards the free edge
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of the lateral meniscus.
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So, we should see linear attachments
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that go towards the popliteus and form the hiatus.
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Let's see if we can find them.
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I don't see any attachments.
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I don't see any linear structures
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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
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to the free edge of the slightly depressed
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fracture of the tibia.
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In other words,
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the lateral meniscus is sliding forward.
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Why is it sliding forward?
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Because those attachments are gone.
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Okay.
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We know our popliteus tendon is still here.
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Here it is in the hiatus.
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Here it is arching down.
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It's got an oblique course into the screen.
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And right here,
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it gives rise to a ligament,
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the popliteofibular ligament.
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So, it should come off and then come right down
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to the fibular head.
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It's coming down.
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But then, we lose it as this fuzzy structure.
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I'm going to make it even bigger.
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There it is.
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And it looks a little bit like this.
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If you have a good imagination,
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you might say,
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okay, then it gets kind of fuzzy in here.
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It's a little squiggled up.
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That's known as the mermaid sign.
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Because it's no longer attached to the fibular tip.
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It's retracting.
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It's corrugated.
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It's ill-defined because it's swollen.
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So, we have a pop fib ligament tear.
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There is one of our arcuate limbs right there.
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That's probably the vertical limb right there.
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Or the lateral limb, the up and down limb.
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It comes down,
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and then it squiggles and it stops.
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That's the proximal component that came off.
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So there is an arcuate tear,
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which we already affirmed in
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the coronal projection.
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Let's scroll it again
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so you can see the arcuate space.
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It's all swollen.
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Here's a little bit of the arcuate there,
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shriveled up.
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There's another piece of the arcuate there sitting,
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hanging by itself.
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And there's a little more,
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then the arcuate is gone.
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Now, let's continue over
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and look at the posterior capsule.
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This is the posterior capsule,
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which also is fused with the OPL,
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the oblique popliteal ligament.
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And it's slightly irregular in its character.
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So, it definitely has taken a hit or an injury.
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But the major injuries are in the attachments
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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.
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My conclusion would read,
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complex posterolateral corner injury or tear
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with A, pop fib ligament tear.
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B, meniscocapsular detachment posterolaterally.
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C, arcuate ligament rupture,
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medial and lateral limb.
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That's number one.
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Number two, ACL transection.
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Number three, grade three MCL
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with folded corrugated MCL.
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Let's take a look at that.
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Folded corrugated MCL with reverse segond fracture,
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rupture of the medial capsule and POL,
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posteromedial corner injury.
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Number four,
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multiple fractures consistent with
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pivot shift mechanism of injury.
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One of which is depressed 3-4 mm.
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End.
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The rest,
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I'm going to bury in the body of the report.
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Yes, there are more findings in this case.
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There are some other pertinent negatives
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that I probably would bury in the body of the report.
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I put into conclusion
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what I want the clinician to see.
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I put in the body of the report
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what I want other radiologists to know that I saw.
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