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Triangular fibrocartilage wrist (TFC) boundaries.

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The TFC is triangular when you look at it

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in three dimensions in the axial projection.

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It's a disc-like structure.

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The radial boundary, which is not really an

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attachment to the radial bone itself, but rather an

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attachment to hyaline cartilage, which is usually a

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thin slit right here, and I'll draw it in for you.

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We don't want to confuse that with a defect or tear.

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There's also going to be a little bit of hyaline

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cartilage along the base of the lunate,

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and some hyaline cartilage in the foveal region.

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We have the hyaline cartilage drawn in, in a portion

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of the body of the ulna, and on top of it is a

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thin slit, which may sometimes have a little bit

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of fluid in it, the capsuloligamentous reflection.

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Now along the tip of the triangular

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fibrocartilage are some folds.

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Thanks.

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Well, let's make those folds green.

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And they, they are folded.

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They're kind of crinkled looking.

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And they kind of come down into the foveal

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region along the axis of forearm rotation,

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a specific area that is described in the fovea.

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Now within this crinkling, which you will see on

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MRI with high resolution, is some vascularity.

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Let's put the vascularity in there, and the

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vascularity will make appropriately red.

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The combination of this vascularity,

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which may sometimes bleed into the outer tip of the

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TFC, just like you have a little vascularity

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in the meniscus of the outer third of the

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knee, this whole complex going towards the

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fovea is known as the ligamentum subcruentum.

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This is the deep layer of the peripheral

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aspect of the TFCC ulnar attachment.

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If there is a deep layer, that means there

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must be a superficial layer to this peripheral,

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as well as anterior and posterior boundary.

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Let's have a look at the peripheral layer.

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The peripheral layer is composed of the

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dorsal and the volar radial ulnar ligaments.

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These attach a little more distally

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than the ligamentum subcruentum.

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And they're superficial to it.

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They are condensations of the

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capsule and the TFC cartilage.

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They make a V shape along with the

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V shape of the triangular fibrocartilage.

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And now you know deep to them will be

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the ligamentum subcruentum that inserts a

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little more proximal into the foveal region.

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The next layer we'll add

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is the lunotriquetral ligament.

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It is part of the TFCC complex, because there

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will be ligaments that run from these structures,

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the dorsal and volar radial ulnar ligaments,

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to the carpus, and to this carpal ligament.

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These are known as ulnocarpal ligaments,

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and sometimes they get individual names.

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Like this one, the ulnolunate ligament coming from the

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palmar or volar radial ulnar ligament to the carpus.

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There's going to be a volar

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one and not shown a dorsal one.

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There's also an ulnotriquetral ligament.

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There's going to be a volar

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one and not drawn a dorsal one.

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Now let's skip out to the periphery of

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the TFCC, just outside the ulnar styloid.

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We've got a wonderful landmark,

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the extensor carpi ulnaris.

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Surrounded by its subsheath.

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The subsheath is part of the TFCC.

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The subsheath is in direct communication and in some

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respects anchored by this filler substance known as

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the ulnomeniscus homolog, which may even bleed into

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these more proximal areas and is very variable in size.

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Mixed in, mushed in, mashed in with the

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ulnomeniscus homolog is the ulnar capsule.

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So we'll make the ulnar capsule some different color.

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Oh, let's pick blue.

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The ulnar capsule is going

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to kind of be buried in here.

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They're mashed together, and you'll often see

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a condensation of the capsule that looks like

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little lines running from distal to proximal.

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I'm showing its origin off the ulnar styloid.

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And this may be referred to as the ulnar

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collateral ligament, even though it is not a well

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defined important diagnostic structure on MRI.

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But you may see these wiggly lines going from

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proximal to distal within the ulnomeniscus homolog.

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So you've got ligaments, homolog, capsule, subsheath

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helping to anchor the distal aspect of the TFCC.

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You've got ligaments that run from proximal

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to distal, known as ulnocarpal ligaments.

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The most notable being the ulnotriquetral ligament.

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These ligaments are paired.

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A group in the front and not drawn a group in the back.

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These ligaments attach to the lunotriquetral

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ligament, which is therefore considered part

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of the boundary attachments of the TFCC.

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We've got a superficial layer surrounding the

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TFC, the Volar, and Dorsal. The Volar and Dorsal

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radial ulnar ligaments, and then deep to it,

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you've already seen the ligamentum submentum

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along the peripheral aspect of the TFC

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attaching in the foveal region.

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I know that's complex, but that's the TFC.