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Case Review: 56 Year Old Male – Classifying Instability in the Short Axis

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Instability in the short axis projection. Basic, basic. You are looking

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at the congruence, or shall I say, collinearity between the center of the

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ulna and the center of the radius. In other words, they should balance.

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One should not be more dorsal than the other or more palmer than

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the other. They're lined up almost perfectly. You might say the ulna might

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be floating a little bit dorsally on this T1 weighted image compared to

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the radius. The ligaments that we're assessing in this projection, let's

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scroll a little bit, are the dorsal radial ulnar ligament,

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which is seen right here, is smooth and black and arcuate, and the

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more irregular, jagged looking, fibrotic, volar radial ulnar ligament. Now

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it's not ruptured, but it is diseased. And that is what has allowed

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the ulna to produce a slight dorsal posture or lack of collinearity between

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the center of the ulna and the center of the radius in this

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case. Let's do it again. I can do better.

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Ready? The short axis view for instability. The short axis view for instability.

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Basic, basic. We are looking for congruence between the position of the

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ulna. In other words, the center of the ulna should line up about

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with the center of the radius. You probably get the impression that the

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ulna is floating just a little bit dorsal. In other words,

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the middle of it is just a little bit dorsal to the middle

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of the radius. And if you thought that, you would be correct.

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What are the structures we're interested in as we scroll?

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Well, specifically in this projection, I'm interested in the dorsal radial

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ulnar ligament and the slightly more irregular thickened volar radial ulnar

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ligament. It is to these ligaments, dorsal and volar, that the ulnar carpal

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ligaments attach, but that's a story for another day.

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So I'm interested particularly in whether the ulna is floating dorsally,

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so called radial ulnar instability. There is a little bit of dorsal subluxation.

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There's also a little bit of dorsal spurring of the radius from this subluxation.

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And the reason for the subluxation is partial chronic tearing and scarring

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of the volar radial ulnar ligament. Oh, but I'm not done yet.

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What about the scapholunate and Lunotriquetral ligaments? They can often

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be inspected in this projection. But in this case, there's such a large

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gap between the scaphoid and the lunate that the capitate has interposed

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itself between the two. That being said, look at this dorsal space right

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here between the scaphoid and the lunate. That

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is a sick, irregular, jagged, fibrotic, no longer present dorsal band of

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the scapholunate ligament. Let's move to the sagittals, shall we?

Report

Faculty

Stephen J Pomeranz, MD

Chief Medical Officer, ProScan Imaging. Founder, MRI Online

ProScan Imaging

Tags

Trauma

Non-infectious Inflammatory

Musculoskeletal (MSK)

MRI

Hand & Wrist

Acquired/Developmental

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