0:01

The wrist, short axis, focus on tendons,

0:05

mostly proximal, although the anatomy is

0:08

consistent as you move from proximal to distal.

0:12

A few important bony landmarks, the groove of

0:15

the extensor carpi ulnaris and Lister's tubercle.

0:18

Let's play.

0:20

The first group to come in, extensor group

0:23

number one, known as the abductor brevis.

0:28

Notice longus brevis.

0:30

There'll be a theme.

0:31

Longus brevis, longus brevis,

0:33

longus, makes it easy to memorize.

0:37

These two are responsible for pain at the base of

0:40

the thumb in adults, which every adult has.

0:44

Everybody's got arthritis at the base of the thumb.

0:46

Everybody has some degree of

0:48

inflammation of this thumb.

0:50

First compartment, which is known as De Quervain's

0:54

disease, or stenosing fibrotic tenosynovitis.

1:00

These tendons are unique because they have

1:02

innumerable slips drawn in by these little dots.

1:06

And when these tendons are inflamed, for they rarely,

1:09

uncommonly, rupture, then the slips may be highlighted.

1:14

And may incorrectly be diagnosed

1:17

as multiple longitudinal tears.

1:20

This is a terrible mistake.

1:23

Then we get into our next group.

1:24

Again, longus and brevis.

1:26

Extensor carpi radialis longus and brevis.

1:29

And these are uncommonly injured, but not

1:32

uncommonly involved in some peritendinitis.

1:35

Extensor, compartment number two.

1:39

Then compartment number three.

1:42

Just medial to Lister's tubercle.

1:44

This one has a very oblique course.

1:47

Making tracking it a little bit challenging.

1:50

Find Lister's tubercle, find the EPL, and

1:55

then go distal and proximal from this point.

1:59

The extensor pollicis longus, its muscle

2:03

and tendon may be implemented, or implicated

2:06

actually, in conditions where the extensor

2:11

retinaculum is thickened, inflamed, or scarred,

2:14

and presses it against other structures,

2:16

known as the crossover syndrome.

2:19

Then we get into the group known as the extensor

2:21

digitorum communis and indices to the index finger.

2:26

Sometimes you'll get tears in this

2:28

region, and it's difficult to sort out

2:31

which or all of the tendons are involved.

2:34

Extensor compartment number four.

2:38

Then the little teeny weeny itty bitty compartment,

2:41

the extensor digiti minimi, compartment number five.

2:45

And finally, in young people, the most important

2:48

compartment, the extensor carpi ulnaris, which

2:52

sits in the ulnar groove some of the time,

2:54

but in extremes of supination and pronation,

2:58

even in the normal individual, it may perch

3:01

on top of the protrusion of the ulnar bone,

3:07

and therefore look like it's subluxing or dislocating.

3:11

The tip-off that this is simply a positional

3:14

phenomenon due to extremes of rotation

3:17

is the fact that nothing is swollen.

3:19

There's no high signal intensity present.

3:22

So anytime it looks malpositioned, without

3:24

the accouterments of inflammatory reaction,

3:28

it's probably a normal positional variation.