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Welcome to MRI Online, Coronal Anatomy,

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Triangulofibrocartilage, Peripheral Relationships.

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We'll start out with a little drawing.

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Let's draw, shall we?

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There is our triangular fibrocartilage, which when

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you're looking down at it, from the top down in

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the axial projection, looks sort of triangular.

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It has boundaries in front and in back that are

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created by the dorsal and the volar radial ulnar

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ligaments, which are attached here, volar and dorsally.

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Not going to scroll just yet because

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this gets a little complicated.

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We've already said in an earlier vignette

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that there are volar and dorsal attachments.

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Let's make those green, for instance, to the lunate.

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They're going to be volar and dorsal.

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There'll be an attachment to the lunotriquetral

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ligament, which is known as the ulnocarpal ligament.

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Let's make that purple.

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That'll be kind of more in the center.

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And then all the way out into

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the periphery, we'll choose blue.

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We've got a volar and a dorsal

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attachment to the triquetrum.

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And that gets us all the way out to the periphery

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where we have attachments to the styloid and to

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the fovea, which we see in the coronal projection.

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Remember, this is kind of an artificial,

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drawn view from the top down.

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But that gets us out to the periphery right here.

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And when we get to the periphery, to the ulnotriquetral

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area, the ulnotriquetral ligament abuts directly

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a structure whose color I'm going to change right now.

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It's kind of a filler.

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Nobody really knows what its function is and why

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it exists, but that filler, which I've made sort of

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turquoise, is known as the ulnomeniscal homologue.

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So that sits directly adjacent to and fills

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in these peripheral attachments and sits

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directly adjacent to and around the free

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edge of the volar and dorsal triquetral

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attachments of the triangular fibrocartilage.

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In fact, this filler is so funky and so weird

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that it produces little fascicles that attach

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to the extensor carpi ulnaris subsheath.

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Which I'm going to draw for you in a different color.

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Let's make it yellow.

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Here's the subsheath.

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And the subsheath sits underneath, as you might expect.

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The extensor carpi ulnaris, I got to

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find another color, will make that brown.

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Wow.

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We're not done yet.

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We've got to go back to the

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ulnomeniscal homologue in turquoise.

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So it may decide to fill in and

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keep going even more medially.

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All the way down towards the radioulnar articulation.

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It's very variable in terms

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of how much filler there is.

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But just to review one more time, the

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relationship is the ulnotriquetral ligament

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sitting directly adjacent to this filler.

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Which is around the peripheral attachments of

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the TFC, which attaches to the filler and attaches

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to the extensor carpi ulnaris subsheath here in

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yellow, which is attached to the extensor carpi ulnaris.

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Now let's scroll.

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Wow.

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So here's our triangular fibrocartilage.

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There are some failures of both the peripheral

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attachment to the styloid, which are

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slit-like and defective right there.

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But most distally are

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the ulnotriquetral ligaments.

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The ulnotriquetral ligaments are going to sit

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right next to this filler, this gray filler

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right here, which is the ulnomeniscal homologue.

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The ulnomeniscal homologue, which has a very

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variable degree of volume and area, sits

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directly adjacent to this brightish, whitish,

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ill-defined, hyperintense area, which is

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that yellow slit I drew for you, the extensor

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carpi ulnaris subsheath. The extensor carpi

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ulnaris subsheath sits directly adjacent

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to the extensor carpi ulnaris tendon.

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And that's the story of the

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peripheral TFCC relationships.