0:00

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

0:06

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

0:12

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

0:16

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

0:21

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

0:27

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

0:32

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,

0:40

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

0:45

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

0:53

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

0:57

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

1:04

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.

1:11

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

1:20

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

1:25

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

1:28

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

1:32

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

1:36

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

1:40

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

1:44

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

1:48

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

1:52

ulnar ligament and the slightly more irregular thickened volar radial ulnar

1:59

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

2:05

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

2:09

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.

2:21

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

2:26

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

2:31

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

2:38

What about the scapholunate and Lunotriquetral ligaments? They can often

2:42

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

2:48

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

2:54

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

3:00

here between the scaphoid and the lunate. That

3:04

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

3:12

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