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Well, welcome.

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I want to focus a little bit on pivot shift injuries

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and menisci again.

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We're drilling into menisci pretty,

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pretty hard,

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and I'm starting out with an axial

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T2 weighted image from a

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just a standard 1.5 Tesla machine

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using T2 fast spin echo.

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I'm sure many of you already noticed that there

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is a pretty large fluid collection here,

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and it's a blood fluid level.

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First point,

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meniscal tears don't give you blood fluid levels,

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so there has to be something else wrong,

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although that's not why we're showing the case.

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But as we scroll it,

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we see the reason for the blood fluid level.

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There's a fracture back here,

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which means something pretty violent happened,

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which leads me to the focus of this discussion,

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which is pivot shift injuries

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and meniscal pathology.

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I don't so much care about the ACL tear

0:54

I'm going to show you,

0:55

or the PCL sprain that you're going to see.

0:58

What I'm interested in is the menisci.

1:01

But before we get to the case,

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I'm going to practice my drawing skills a little further,

1:07

and I am going to make you a meniscus,

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kind of in a 3D here.

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I'm even going to try and make it have some depth.

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So, this is the height of the meniscus right here.

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And as we discussed before,

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we have an inner third, a middle third,

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and an outer third.

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Now when you have a pivot shift injury,

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and I think most of you can see me,

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what actually happens is the femur is going to go...

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the femur is going to go backwards

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and it's going to slam down on the back of the tibia.

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So when it does that,

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and sometimes there's a twist with it,

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sometimes it's just direct.

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And when it does that,

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it crunches not only the bone,

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because that's why we have the fracture here,

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but it also crunches the meniscus.

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So when that meniscus gets crunched,

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it often cracks.

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And that crack is usually a vertical crack

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in the outer third.

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It happens in almost every single person.

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Now, if we look at the meniscus from the side,

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here's our side view, or a sagittal view,

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this would be the back.

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So, we'll call this posterior with a P.

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And this is the back where the crunching

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happens, right here.

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So we get this crunch,

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and then we get our crack.

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And that crack could be a partial crack,

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which we do nothing about, by the way.

2:30

That crack could be a crack all the way through.

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Pardon my lack of steady hand here,

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a linearity.

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That is still, most often,

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not a surgical situation.

2:43

What would you call that?

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You would call that a longitudinal vertical tear,

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as opposed to another kind of vertical tear

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we're going to learn about,

2:53

which is the radial vertical tear.

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So that longitudinal vertical tear,

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even though it goes top to bottom,

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we say it's full thickness.

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The first one I showed you is partial thickness,

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is almost never operated on.

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Now, what do we mean by length?

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If that vertical tear goes from here to here

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and we're able to measure it from here to there,

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that would be its length.

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Now, how would we measure it?

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We would measure it by...

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I'm going to have to change

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colors here for a moment.

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Let's say we have a coronal.

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We'd measure on the coronal from here to here,

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because that's the part of the tear

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that would show up.

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Let's say that's 2 cm.

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And now, the tear is going forward.

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See, here's the tear right here.

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So the next slice is going to be here.

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We just start adding slices.

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So, we started out on foss

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or parallel to the tear, 2 cm.

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And now we add a 4 mm cut, 2.4.

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Another 4 mm cut, 2.8.

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And another 4 mm cut 3.2.

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So, the length of this vertical tear

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is going to be 3.2 cm.

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Would we operate on it?

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Probably not.

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If it's not gapped, if it's in the outer third,

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we're still going to leave it alone,

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which is counter to prior teaching,

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where most of these very,

4:18

very long vertical tears used to get sewn.

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Now, occasionally, if somebody's in there,

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you will see them put a stitch in it.

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But characteristically,

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this type of pivot shift tear is not surgical.

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Now, let's take that one step further.

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So, now that I've done my very manually

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dexterous erasure,

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let's go back to

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our view of the meniscus from the side

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and our three dimensional view.

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And we'll give the meniscus a little bit of depth here.

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I think I did a better job on this one.

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So, sometimes the meniscus gets crunched.

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But also remember, and I think you can see me,

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the femur is going backwards, right?

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The tibia is going forwards like this.

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So there's got to be some crunching,

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but maybe there's a little less crunching

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and a little more stretching

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because the meniscus has to be attached to something.

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Remember, from our first series,

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we said the meniscus was attached

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peripherally and at the roots,

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but its inner free tip,

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in other words, right here, is free.

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It's floating free.

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So now, we are stretching.

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Maybe we're crunching, maybe we're not.

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So maybe we have the vertical tear,

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maybe we don't.

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But we're stretching,

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and as we stretch, stretch, stretch,

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we get a strain, or a bleed, or a microbleed.

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That's really common.

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And we call that a meniscocapsular strain,

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or a meniscocapsular hemorrhagic strain.

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Occasionally, if it's really violent,

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this will break off its attachments

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and it'll flip over on itself.

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It'll tumble.

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That's a true meniscocapsular separation.

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Those are really uncommon.

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And in fact, they're rare.

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Now, on the medial side,

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it looks a lot different than the lateral side,

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because on the medial side, these attachments,

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which I'm going to make a little different color,

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they're kind of like fat's domino,

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a pool player.

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They're kind of like short,

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little stubby things.

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So, you don't really see them.

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All you see is a bucket of blood.

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We'll make that red,

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because I'm trying to be a little clever here.

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So, you'll see some kind of fuzzy stuff here.

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And if the patient's a little bit unlucky,

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then maybe we also happen to have

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a little vertical tear here as well.

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So, you might have two things.

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This is an extremely common scenario.

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It happens in almost every pivot shift.

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Now, sometimes what actually happens

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is you get this,

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and I'm going to make my line, if I can,

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through some

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limited manual dexterity,

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I'm going to make my line a little thinner,

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a lot thinner.

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And instead of having bleeding back here,

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instead of having a pretty good, obvious,

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fairly thick vertical tear, over here,

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we have something very,

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very thin right next to the capsule,

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which a lot of times,

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our friends misconstrue as the capsule itself,

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but it's not.

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It's in front of the capsule.

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And so I refer to that,

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it's my own terminology,

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I call that a sliver tear,

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because it's a tiny little thin line,

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vertical tear,

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vertical longitudinal tear

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right next to the capsule.

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And this little tear frequently coexists

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with that bleed.

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In fact, it's the majority of pivot shifts,

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and the minority of them,

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but not an insignificant minority,

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will have pretty thick vertical tears,

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but still in the outer third.

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All of these tears,

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almost uniformly, are non-surgical and heal

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because of the vascularity of the red red zone

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in the outer third.