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This next case is a 39 year old man with a right hand strain

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of the long finger of the M C P joint. Now,

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most of you know I'm an ex boxer, an ex fighter. And, um,

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when you, when you strike someone,

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which is a heck of a lot of fun when you have gloves on,

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it's kind of fun when you don't have gloves on too. But when you,

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when you deliver a blow,

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you're supposed to deliver a blow with your hand so that you lead with

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these two knuckles together. They must strike simultaneously.

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And if you're in a bar fight and you hit somebody and your hand is,

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is angled like this, and you lead with the middle knuckle,

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you are gonna fracture that knuckle. Um,

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and that is known as boxer's knuckle. When you, when you injure that,

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that knuckle in a certain way, that middle knuckle,

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because you don't have the hand correctly aligned. And of course, you know,

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I'm just, I'm kidding, partially kidding. And, um,

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but all the things I told you are true and, and accurate.

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So let's take a look at our potential boxers knuckle.

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The hand strain is not a very helpful history.

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This time we're dealing with a one Tesla open.

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So we're coming up in field strength a little bit,

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and we've got all the metacarpal knuckles facing us.

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And let's go to the, let's go to the index finger. And on the index finger,

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we're really gonna blow it up. This is pretty good for one Tesla, right?

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It's an open, and there is our common extensor.

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And when it gets very distal out, out towards the, the tip of the finger,

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it's known as the terminal tendon. And it has,

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it has these stabilizers on either side. There's a superficial layer stabilizer,

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which you can see right there. I'm gonna try and put an arrow on it.

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It's very difficult to see, admittedly right here.

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And then, then we've got this component, which is a little bit deeper.

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So we have a superficial and deep component to this structure,

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which is known as the sagittal or oblique band. And it,

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it, it stabilizes the, the, uh,

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the common extensor tendon, so-called conjoint,

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common extensor. Now, on the other side, on the,

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on the ulnar side, uh, you can see the thumb is over here.

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You can also see at least the superficial component.

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It may not be quite as easy to see, but if I scroll, you can see it.

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There it is right there. Let's scroll the other way. Little harder to see.

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Uh, if we go to the T two, I think it's easier to see. Blow it up a little bit.

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There it is right there.

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Now it's very hard to see the two layers unless you use a finger coil.

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We just happen to catch it over over here.

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Now that you've seen that one. And maybe let's look at one other one.

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Here's another one right there. There's a, there's an oblique sagittal band.

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There's another oblique sagittal band, and there's the tendon,

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also known as the central tendon, the common central tendon,

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the conjoin tendon. It's right smack dab in the middle here,

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not so much. Where is the tendon?

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The tendon has gone over to the ulnar side. It's,

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it's ruptured and completely subluxed and displaced.

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How can that happen? Well, you've,

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you've ruptured the radial sagittal band. Now,

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when it gets this far out,

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usually both bands are gone 'cause it completely has escaped.

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Usually if this band is attached, what you'll see is this,

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you'll see the tendon kind of sitting right here attached to that band that's

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tugging on it. And this one has ruptured, allows for the release.

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But when it comes all the way out,

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and now it's superficial to the,

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the, uh, the band that, that sits right underneath it,

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which normally would attach to it,

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then you've lost the attachment to either band and it's basically free to move

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wherever it wants to.

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So even though this was read as a radial band rupture,

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it's a radial band rupture and an ulnar band tear that's allowed

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the central tendon to escape. And, um, you know,

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this is one of the phenomenon known as boxers knuckle.

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So let's keep looking around now. And then you see, as we get a bit more, uh,

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a bit more distal, it comes back into place.

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And then as we go more proximal, it's completely out of place and,

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and doesn't get back to where it should be for a long ways.

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Let's see what else we've got here. Let's see how the, uh,

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T two looks.

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Not a lot of additional information on the T two other than the fact that it has

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completely escaped and now lies superficial to that sagittal band.

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So that tells you it's completely,

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both bands are torn and this thing has ruptured and

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migrated over to the ulnar side of the hand, towards the pinky.

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Let's see if there's anything else in the corona long axis projection that's of

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any value. Perhaps the anatomy is of value.

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We can see the collateral ligaments of the middle

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knuckle, the middle finger. And what's this, um,

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that is part of the capsule right there. Collateral ligament,

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part of the capsule. Let's keep looking. And there's our,

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as we go dorsal, there is our displaced extensor tendon.

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Now let's go to the flexors. The flexors look fine,

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so all good there. Let's look at the sagittal. Now

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we're on the pinky. And you can see the extensor tendon,

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which inserts at the base of the middle phalanx and then sends a continued

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terminal tendon to the tip of the base, uh, of the finger.

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So the distal phalanx right there is where the terminal tendon inserts the,

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the central conjoint tendon inserts right here.

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So base of the middle phalanx,

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base of the distal phalanx is where you're going to see that. And, um,

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what other anatomy do we have here? We have the,

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the flexor digitorum profundus,

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which goes out to the distal aspect of the digit.

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And if you look really carefully,

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you'll see the proximal insertion of the flexor digitorum,

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uh, superficialis,

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which inserts on the proximal aspect of the middle phalanx.

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And there are actually two bundles. There's a medial and lateral bundle.

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Let's see if we can see them as we go out. Distally,

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kind of difficult to separate them out. Let's see if we can,

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on the T one weighted image,

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No, not so much. Not, not ea, not easy to separate them out.

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You are able to see the pulleys though. And, uh, here's the pulley mechanism,

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which keeps the, keeps the flexor tendons nice and tight to the finger.

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When you flex and extend, you know,

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you've got an A two pulley and the proximal phalanx, you got, um,

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an a four pulley over here. And then you've got pullies one, three,

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and five at the articulations. And you also have cruciform pulley,

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which we don't easily resolve without the finger coil.

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So that's a little bit of anatomy. And, um,

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wish I had a better shot to show you the flexor digitorum,

7:59

sublimes and profundus, or superficialis and profundus.

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But I think you have seen the crux of the case,

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which is a sagittal band rupture. Started on the radi,

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started on the radial side, finished on the ulnar side,

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allowed the extensor tendon to escape and sublux and completely

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displace.

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Does the term extensor hood include the sagittal oblique?

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Yes, the extensor hood includes the sagittal oblique,

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but the hood is a more broad, uh, term because it includes oblique attachments,

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uh, that are not the sagittal band itself.

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So the sagittal obliques are a subset of the extensor hood.

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Hopefully that answers your question.