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The wrist, anatomy, MR, the short axis view,

0:07

and the proximal aspect of the axial projection in the

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region of the radial ulnar joint is our focus today.

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I'm going to approach this not simply by naming

0:19

structures, which you can get out of a textbook.

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I'm going to give you the practical

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approach to analyzing these structures,

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and I begin by with a distal radial ulnar

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articulation which is often overlooked.

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Examine the congruence or the relationship anterior

0:35

to posterior between the ulna and the radius.

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Now that may vary depending upon whether

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the patient is in pronation or supination.

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If the patient is in pronation, you're going to see

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If the patient is in supination, the groove will rotate

0:55

down, and if the patient is in the neutral position

0:59

with the thumb up, then it'll be somewhere in between.

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That will affect the relationship between

1:06

the radius and ulna, but there will be times.

1:09

When you have to examine both wrists to see

1:12

whether one ulna floats in a dorsal position

1:16

in extremes of supination or pronation,

1:20

suggesting radial ulnar instability.

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So a comparison between the two sides and the short

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axis view on MR or even CT is not out of the question.

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Some other basic structures.

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We've got a group of muscles that

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consist of, as you might expect, flexors.

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We'll discuss them individually a little bit later on.

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We've also got a fatty space here,

1:46

which is a pathway of spread for various

1:49

inflammatory processes called Parona's space.

1:53

And we've got the Pronator Quadratus, which

1:56

is involved in pronation, a pretty big muscle.

1:59

When we look at the radioulnar articulation,

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it not only consists of two bones, but within it.

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It is a capsule, some synovium, and some cartilage.

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Then on the dorsal surface, we've got a group

2:13

of six compartments, which we will subsequently

2:17

name for you, but not right this minute.

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They're involved in, as you might expect, extension.

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But let's take a few simple, bony landmarks.

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For instance, Lister's tubercle.

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This is a wonderful landmark to

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isolate the extensor pollicis.

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Brevis, which may be affected in crossover

2:42

syndrome, to be discussed a little bit later

2:44

on, but it's one of the hardest extensors

2:47

to identify because of its oblique course.

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So, find Lister's tubercle, go one over to the ulnar

2:54

side, and you have found the extensor pollicis brevis.

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Another variation that you might

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encounter in the short axis view, is the

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position of the extensor carpi ulnaris.

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Now it's secured by this superficial retinaculum,

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but underneath it, and not particularly well

3:15

seen in these short axis views, and I'll scroll

3:18

a little bit for you, you can see it right

3:20

there, is the extensor carpi ulnaris subsheath.

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Here's part of the subsheath right here.

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That helps attach the ECU, or extensor carpi

3:31

ulnaris, to the rest of the TFCC, as you can see,

3:35

via the subsheath, the area of the

3:38

meniscus homologue, and the capsule.

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More on that in further detail in another vignette.

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Introduction to the short axis projection.