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Welcome to MRI Online, Coronal Projection,

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Triangular Fibrocartilage, an important

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structure as a cause of ulnar-sided wrist pain.

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It's a disc-shaped structure, although

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in the coronal projection it looks a

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little bit trapezoidal or rectangular.

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It attaches to the hyaline cartilage of the radius.

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This brightish area that we see right here is

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not a defect, but rather the hyaline cartilage

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of the radius where the TFC has a plug-like

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attachment to it that's a little bit fan-shaped.

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It then continues more to the ulnar side,

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becomes a little bit wider, and then has

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a complex array of additional attachments.

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Let's scroll a little bit, and we'll

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see a few of these attachments.

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One of them is to the lunate

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triquetral ligament, right there.

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And that's known as the ulnocarpal attachment.

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You're going to learn later on that there's

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a volar and a dorsal ulnocarpal attachment.

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There's also an ulnolunate attachment, and there it is.

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You're going to learn later on that there are

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a volar and a dorsal ulnolunate attachment.

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More peripherally, is an ulnotriquetral attachment.

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And yes, you're right, you're going

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to learn later on that there are both a

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volar and a dorsal ulnotriquetral attachment.

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Ulnotriquetral attachment, but the simple

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ones in the coronal projection are the ones

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directly to the ulnar styloid and fovea.

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Now this one is abnormal, and I did that

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intentionally because there's swelling and

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inflammation that highlights this region.

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So let me get out my drawing tool.

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I'm going to make myself a very pretty ulnar styloid

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with a fovea and a triangular fibrocartilage.

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With its somewhat fan-shaped attachment

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to the hyaline cartilage of the radius.

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And then I'm gonna switch colors,

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if I can do it with some skill here.

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And I'm gonna draw my attachments into the

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fovea, which plug directly into the fovea.

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And there's usually one dominant foveal attachment.

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If we look over here, our foveal

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attachment has a little defect in it.

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And there is some swelling in the

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underlying subcortical, subchondral bone.

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That's because this foveal

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attachment has a defect in it.

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It's injured.

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So this is what we would call a

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peripheral tear or peripheral sprain.

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And would be labeled a palmar.

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Uh, 1B, if it was dramatic in nature, but

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that'll be a story for another vignette.

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Then we get to the ulnar styloid.

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The styloid attachments are more fan

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shaped, and they can be innumerable,

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2, 3, or 4 in number, or 1 thin sheet.

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In this case, there's a defect again in

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the region of the styloid attachment.

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There's the high signal intensity defect, and if

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I come off my drawing tool and scroll it for you,

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you'll see that there's never really a good plug

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between these structures and the ulnar styloid.

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Let's, let's track it.

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Never really plugs in very well.

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And there's some swelling distal to the ulnar styloid.

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And that's kind of nice because that swelling

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is located in the pre-styloidal recess.

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Sometimes the recess is contained or

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confined to the tip of the ulnar styloid.

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Sometimes it's freely communicating

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distally as this one is.

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Even though it's swollen and filled

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with a little synovial fluid.

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because of an associated injury and a

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small body that resides in this region and

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highlights some of the structural anatomy

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that we'll detail a little bit later on.

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So we have some peripheral attachments here to

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the styloid and the fovea that we drew for you.

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We have volar and dorsal attachments that

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we highlighted that are pretty subtle.

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A triquetral volar and dorsal attachment.

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A ligamentous attachment

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known as the ulnocarpal ligament.

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And an attachment to the lunate, which

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we see right there, known as a volar

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and dorsal ulnolunate attachment.

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And then finally, the attachment to the radius.

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So a rather complex pattern of anatomy for

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the triangular fibrocartilage in the coronal

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projection, which sits directly adjacent to

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the capsule and the ulnar meniscus homologue,

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which will be another discussion of the ulnar

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side of the wrist coming to a theater near you.