0:00

The MRAP coronal projection, with a gradient

0:03

echo on the left, a T1 in the middle, and a

0:05

PD spur on the right, affords you the ability

0:09

to spot and grade various instabilities.

0:13

Let's start with SLAC wrist,

0:15

scapholunate advanced collapse.

0:18

There are three grades of SLAC wrist.

0:21

First grade, involvement of the radial styloid, or

0:25

free margin, radial margin, of the scaphoid fossa only.

0:29

That would be grade one.

0:30

This fossa is abnormal.

0:32

It's undulated, it's irregular,

0:33

it's deformed, it's fractured.

0:36

Grade 2 would involve the whole surface of the radius.

0:39

The lunate fossa and surface is

0:41

involved, so it ascends to grade 2.

0:46

Grade 3.

0:47

There is involvement of the distal pole of the

0:49

lunate, where the capitate comes in contact with it.

0:52

Oh, it's abnormal right there.

0:54

We have met and ascended to the criteria for grade 3.

0:58

That's SLAC wrist.

0:59

Ulnar translocation.

1:02

Taleisnik described two types of ulnar

1:05

translocation where the lunate and triquetrum

1:09

go east, marching on Philadelphia and

1:12

New York while the radius stays at home.

1:14

Type 1.

1:16

In such cases, the radial collateral

1:18

ligament, depicted by my arrow, is intact.

1:22

The other type, or type 2, is when all three

1:25

bones march on Philadelphia and New York.

1:28

That is not happening.

1:31

The next type of instability is

1:34

dissociative instability, or diastasis,

1:37

or failure of the scapholunate interval.

1:40

Usually when this occurs, at least the dorsal and

1:42

often all three components, dorsal, membranous, and

1:46

volar components of the SL ligament have failed.

1:51

The strongest stabilizer is the dorsal.

1:54

As soon as you see that, your next move is to

1:57

go to the region of the radioscaphocapitate

2:00

ligament, which is here, and the ligament that's

2:04

a little more proximal to it, which is laying

2:06

down right there, right there, known as the

2:10

radiolunotriquetral or long radiolunate ligament.

2:14

That one is torn.

2:17

In fact, although not shown clearly in this case,

2:20

the radioscaphocapitate ligament is torn, but

2:22

this is the location of it, and that is not the

2:25

purpose of me showing these coronals right now.

2:28

Just to tell you what maneuvers to perform.

2:31

Yes, there is first CMC arthrosis,

2:34

but that is a story for another day.

2:36

So we have hit three, and now we'll

2:38

conclude with the fourth type of

2:40

instability, lunotriquetral instability.

2:44

This often has to be inferred.

2:46

As the ligament, the lunotriquetral

2:49

ligament, is often very small.

2:52

So if you don't see it, you can use the indirect

2:55

signs of instability, such as advanced arthrosis.

2:59

Patient has mild arthrosis.

3:01

Fluid in the joint space.

3:03

Patient does not have fluid in the joint space.

3:05

Widening of more than 3 millimeters.

3:08

Does not ascend to the criteria of

3:09

widening more than 3 millimeters.

3:12

Therefore, by secondary signs,

3:14

the lunotriquetral ligament

3:17

is deemed intact.

3:19

We can usually see it directly, however.

3:21

That concludes our four basic instabilities

3:25

we can see, assess, and grade, including

3:28

slack wrist, ulnar translocation, scapholunate

3:31

failure, lunotriquetral failure.