0:01

All right.

0:01

Now let's see about classification.

0:04

Okay, because I think that will become important.

0:09

There are several systems that have been mentioned.

0:12

You can classify carpal instability through chronicity,

0:15

through constancy, through etiology.

0:18

I'm not gonna get into that in this lecture.

0:20

We're gonna use the Mayo classification system,

0:24

which is very, very popular with hand surgeons.

0:28

There are four categories.

0:30

I'm not gonna cover the last one, so it's kind of in gray.

0:33

But the three in white text here are the ones

0:36

that we're gonna cover Carpal instability, dissociative

0:40

a derangement within

0:42

or between bones of the same carpal row,

0:46

carpal instability, non dissociative.

0:48

And by the way, that's abbreviated Sid, the first one,

0:51

the second one, abbreviated Sid derangement

0:53

between the radius and bones of the proximal carpal row

0:57

or between the proximal and distal copper row,

1:00

but not in the rows themselves.

1:03

And then carpal instability complex has

1:06

features of both of these.

1:08

So let's go ahead

1:10

and at least mention, for example, that we have

1:13

to remember some of the arcs that were described

1:17

by my good friend, uh, l Lal Lula,

1:21

because he in fact described, uh, um, uh, many of these.

1:25

And so you need to know those gall lula's arcs.

1:29

Generally there are three.

1:31

The first is drawn, as you can see here, along the surface

1:37

of the proximal surface of the proximal carpal rope.

1:41

And typically it is a smooth curve.

1:44

The second curve line is along the distal surface

1:48

of those three bones.

1:49

And then the third line is along the proximal surface

1:52

of the handmade and the capitate.

1:56

So those are the three lines.

1:58

Here's an example of disruption of gula line one.

2:03

The scapholunate aspects looks good,

2:06

but when we look at the surface of the trium,

2:09

the disruption is right there.

2:10

And this is what you would expect to see

2:13

when the problem lies between the lunate and the trium.

2:19

The second type of lines that may be useful,

2:23

and we certainly use, I eyeball them,

2:25

but many people measure them, are drawn as follows.

2:30

The first here to establish the scap lunate angle is a line

2:35

going through the distal radius, through the short axis

2:39

of the lunate, the long axis of the capitate,

2:42

and the long axis of the third metacarpal.

2:45

And then we draw a second line by moving that down

2:49

and drawing a line tangent to the

2:52

lar surface of the skateboard.

2:54

The intersection of those two lines, in fact

2:58

Generally is 30 to 60 degree.

3:01

And this is called the scapholunate angle.

3:04

We'll be talking about DC and vc.

3:06

You're gonna, certainly, you've heard of those terms,

3:09

but let's just see what they mean.

3:12

This is the normal situation with the normal.

3:15

This was labeled navicular bone,

3:16

but it's the scaphoid, a normal scapholunate angle.

3:21

As you can see, the example on the top is in fact

3:26

DC or dorsal tilting of the lunate.

3:29

And we can see that here. And here's a radiograph.

3:32

Now, DC is not the name of an instability pattern.

3:36

It occurs with several different instability patterns,

3:40

as I will indicate.

3:42

And the same thing at the bottom where the lunate is, uh,

3:46

facing down the angle is small.

3:49

And here's what it looks like on a lateral radiograph.

3:52

So DC there is an increased angle,

3:57

scap illuminate angle vc.

3:58

There is a decreased scap illuminate angle.

4:01

And then just a couple of quick things to look at

4:05

to prove the alignment is normal.

4:08

The proximal pole of the scaphoid should line with the

4:12

distal articular surface of the radius,

4:16

and the lunate position will be influenced

4:19

by whether the wrist is dorsi flexed

4:22

or lar flexed at the time of imaging.

4:26

You can see here that the lunate is dorsally tilted,

4:29

but so is the capitate.

4:31

So this would be normal alignment.

4:34

And then the final point I will make will relate

4:37

to the shape of the distal portion of the lu.

4:44

When you look at that shape in the normal, it kind

4:48

of has a small curve to it,

4:51

and the overlap lap a little bit of the capitate.

4:55

When you're dealing with VC

4:58

and with lar tilting of the lunate, you will see

5:01

that the distal surface of the lunate is more distal

5:04

and it is pointed, looks like a V.

5:07

That's easy to remember.

5:09

And if you're dealing with DC okay,

5:13

dorsal tilting, it has again, a curved appearance,

5:17

but it is projected a little bit more distally than normal.

5:21

Now, I realize in this sample there is widening

5:24

of this caate in our space.

5:26

We we'll be dealing with that.