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15-year-old gymnast with ulnar-sided wrist pain.

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Got a series of coronal images.

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Got on the left a proton density fat suppression.

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In the middle, a gradient echo.

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And on the far right, we've got a T1-weighted image.

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Let's kind of settle on the mid-region of the

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triangular fibrocartilage and the region of the

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lunate-triquetral interval as a good stopping point.

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Let you have a look for a minute.

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And now, what's going on?

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Well, look at the position of

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the ulna relative to the radius.

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It's a little distal to it.

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Especially the radial aspect of the ulnar body.

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So let's talk about variance for a moment.

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We've got the ulna.

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I'll use my rudimentary drawing skills.

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And we've got the radius.

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And we'd like to see the distal edge

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of these two surfaces be congruent.

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If the ulna juts forward a little bit

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relative to the radius, by a few millimeters,

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then we'd say there is positive ulnar

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variance or positive ulnar variance posture.

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Now, on an X-ray, that's about a two

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to three millimeter measurement, but

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it's highly dependent upon position.

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If the patient is pronated, the ulna's gonna

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jut forward more; if supinated, it's gonna go back.

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With a firm grip, it's more distal, so it's

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gonna be more positive variance in the hand grip

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position, which we normally don't do on MRI.

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What number do I use as a mentally

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significant number with regard to variance?

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I use about 6 to 8 millimeters.

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But more importantly, I will use the indirect

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signs of abnormal variance to hammer home

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the fact that the variance is positive

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and relevant to the case in question.

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And in this scenario, we have just that.

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Indirect signs that tell us that the slightly positive

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variance of the ulna, it's a little more distal.

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Than that of the radius is relevant.

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Before we do that though, let me give you one

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other measurement that I don't use, but it's

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called the Ulnar Styloid Process Index, or USPI.

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So what we do is we measure, let me change colors

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here for a moment, just to make it a little easier.

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We measure the length of the ulnar

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styloid process, and we'll call that C.

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Then we measure the width of the

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ulnar body, we'll call that D.

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So we got A and C, and then we measure this

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discrepant distance, and we'll call that B.

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So that might be something like, uh, three millimeters.

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And then we come up with a formula.

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C, the ulnar styloid, minus B, that

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discrepant distance, divided by A, is the

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USPI, or the Ulnar Styloid Process Index.

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And generally, a number of about 0.2 or 0.

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62 00:03:05,175 --> 00:03:08,115 0.21 is where you should sit.

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Okay, now let's go back to the case itself.

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And let's scroll the center image.

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It's the highest resolution image because

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it has the thinnest slice thickness

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and also has a pretty good matrix.

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So we see that the cartilage of the ulnar

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styloid and the cortical surface lie slightly

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distal to the radial styloid by a few

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millimeters in this young 15-year-old patient.

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And we're going to assess the hyaline cartilage

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itself, which at first glance looks pretty good.

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Although it's a little bit brighter

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than it is elsewhere on the image.

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I think that's a soft sign,

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a little tougher to appreciate.

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But certainly it's a little

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attenuated on the triquetral side.

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I'm gonna make it even bigger.

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There we go.

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It's a little attenuated, and it's a little gray,

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and it's also a little attenuated and a little

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gray on the triquetral margin of the lunate.

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Then let's look at the triangular fibrocartilage.

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It's kind of fat, and it should

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thin out, but not this much.

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It's a little thinner than I would otherwise expect,

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and there is a horizontal signal that is more

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conspicuous in the inner third, which, as you know from

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meniscal evaluation in the knee, shouldn't happen.

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So we have a horizontal signal that is consistent

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with a horizontal-type tear from repeated

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impaction of the ulna against these structures.

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So what happens in this positive

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ulnar variance impaction scenario?

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We've got indirect signs.

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So we know the positive ulnar variance is relevant.

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And what are those indirect signs?

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Well, we certainly have some chondromalacia

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on the lunate and triquetrum.

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So we have lunatochondromalacia,

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triquetral chondromalacia.

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Usually with impaction, the first

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thing that happens is the TFCC thins.

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It's already thin.

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We would call that a Palmer, Roman numeral

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II, impaction A, or a chronic TFCC disease 2A.

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What's a B?

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You've got triquetral chondromalacia

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and lunatochondromalacia.

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We have that.

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So we're at a B.

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What's a C?

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A C is when we would also have a

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triangular fibrocartilage tear.

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Now they're usually vertical

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in the central or inner third.

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This one happens to be a little

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bit more horizontal or oblique.

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So now we're up to a C.

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D would be interruption of the

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lunato-triquetral ligament.

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It is not interrupted.

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It's seen as an amorphous, ill-defined gray triangle.

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But the lunato-triquetral interval isn't perfect.

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It's got a little bit of swelling in its

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interval telling you that this piston effect

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is trying to spread these two structures apart

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and creating some mechanical inflammation.

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What would be a D then?

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A D would be interruption of the

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triangular lunato-triquetral ligament.

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We don't have that.

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So we don't have a 2D.

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What would be an E?

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Diffuse generalized arthrosis.

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We also have another beautiful indirect sign.

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That our impaction is relevant,

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and that is lunate edema.

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Here it is on the proton density, fat

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suppression image, and you can more

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subtly see it on the T1-weighted image.

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So there's no question that in this gymnast,

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who's gripping, who's grabbing, who's

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pushing, who's impacting on handsprings and

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other activities, is firing the ulna against

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the lunate and creating ulno-lunate

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Impaction Syndrome, Palmer, Roman numeral 2, C.