0:00

For our final thumb case, I am not gonna give you the finger,

0:04

I'm gonna give you the thumb.

0:07

And we start out at the first C M C or

0:11

first carpo metacarpal joint.

0:14

Now you wouldn't know that unless I cross-referenced it,

0:17

and I will cross-reference it for you in a moment.

0:20

But there is a purpose for me showing you all three sequences,

0:25

which is a rather good idea. Anytime you're looking at a tendon,

0:28

if you are looking at a tendon, it is very desirable.

0:32

Let's say the tendon is doing this, let's say it's a hand.

0:37

Then you wanna be in a position where you are perpendicular to the tendon

0:42

with a minimum of two, but preferably three sequences.

0:47

And what are those three sequences? You want them to go in this orientation?

0:52

Always perpendicular to the tendon no matter what.

0:55

And the sequences are something very heavily water weighted.

0:59

And no, that's not a T2 weighted image.

1:02

That is not a T2 weighted image with fat suppression.

1:05

That is either gonna be a PD spur like this one on the left,

1:08

also known as a PD spare or PD special. I'll mean the same thing.

1:14

Proton density with fat suppression.

1:16

Or you want a high quality gradient echo image.

1:20

Something like adage, merge medic, M F F E,

1:26

all from different vendors. You want a t2,

1:31

but the T2 is not the diagnostic sequence,

1:33

it's the refining sequence for tendons. So this is the detector,

1:38

this is the refiner to give you age and date and position of

1:43

torn ends. And the T1 is kind of like the master of ceremonies.

1:48

It gives you an idea of what's happening in the neighborhood,

1:51

what's happening in the skeleton, how much swelling is there,

1:56

is there hemorrhage?

1:57

So these two are really refiners and this is a detector.

2:03

So now I said we're starting out at the first cmc.

2:06

Let's get out of our pen for a minute and do some scrolling.

2:10

We're scrolling from proximal,

2:13

so you should know that cuz you see the tubercle of the greater angular,

2:18

greater rectangular, also known as the trapezium. And now we start to go distal.

2:22

We're at the base of the thumb and here comes our friend,

2:26

the flexor lysis lungs.

2:29

It's a very important structure because not only does it flex the IP

2:34

joint, it also flexes the MP joint.

2:40

So it has a double function.

2:42

It arises from the voler surface of the radius and the interosseous membrane,

2:46

and then courses for a very long distance.

2:49

It passes through the carpal tunnel right next to the flexo carpi radialis,

2:54

which by the way is not in the carpal uh, tunnel. And then

2:58

It, it snuggles up alongside the thumb where it is secured

3:04

by a series of annular pulleys.

3:07

Now I'm not here to talk about the pulleys today,

3:09

I've already done that in a separate vignette,

3:12

but there happened to be four pulleys.

3:14

And let me pull down something that's long axis for a moment and then I

3:19

will put, put up my short axis T1 again.

3:22

So let me pull this down and um, I'd rather have a sagittal actually,

3:27

actually, here's my sagittal.

3:29

So here's my flexor lysis and the

3:34

pulleys that secure this are the first pulley,

3:39

the second pulley, and then there is an oblique pulley and a variable pulley.

3:43

So there are actually four pulleys that keep this structure close

3:48

to the phalanx. Unfortunately, there's a space here, there's a hole here.

3:53

There's a gap here where the tendon has been cut by a

3:58

saw. So now let's scroll.

4:02

I'm gonna make them even bigger so you can see on your portable iPhone or

4:07

your portable phone or Android. And let's scroll. We're in the good tendon.

4:12

Good doggie, good doggie, good doggie, good doggie, bad doggie.

4:18

It's gone, right? There's a big hole there.

4:23

And then there's still a gap. There's still a gap. And then on the sagittal,

4:28

we see it come back again right at the insertion,

4:31

at the base of the distal pha legs where it merges with the phalanx and also

4:36

the capsule. Now lemme put the T1 back up again

4:42

and do some scrolling. I'm gonna make the T1 a little bigger so it matches up.

4:47

You might say, well, why do you need all three?

4:50

This one's easy cuz it's transected.

4:52

But what if you had an intra substance there? In an interest substance tear,

4:56

you'll see marked ality and sharp definition here.

5:00

If it's chronic, it may disappear on the t2. If it's fresh, a fresh tear,

5:05

it'll stay on the t2 and then on the T1 weighted image,

5:10

it'll help you further define the morphology and what's happening in the

5:15

surrounding bone.

5:16

So it's very nice to have all three of them lined up in a row at

5:21

each single successive short axis projection,

5:25

absolutely positively perpendicular to the axis

5:30

of the tendon. Let's go back now to something long axis.

5:36

It's what is probably a little less desirable.

5:37

I'm gonna make it a little bigger. And let's follow our tendon.

5:42

There's our tendon. Now that's volume averaging back there,

5:47

but let's keep going. There's our tendon,

5:49

and then we're never able to follow our FPL any further than this.

5:53

That is where it stops. Now you may think you're done,

5:58

yet you're not.

6:00

Let's put up something that is very generalized that any scanner can do.

6:05

In fact, let's throw up a series of long axis projections.

6:08

I've got a T2 in the middle and I've got a T1 on the

6:13

far right and maybe a PD on the left. Yeah, there's a nice pd.

6:17

This one's coronal. These are sagittal. Now,

6:21

it's no secret that like the entire world,

6:25

the first carpo metacarpal joint is arthritic.

6:29

The oblique ligaments are torn. There's a superficial at a deep one.

6:32

That's not our concern today.

6:34

These are also known as the anterior oblique or beak ligaments.

6:39

There's also a dorsal radial ligament that stabilize the first CMC talked about

6:44

in another vignette. But why aren't we done?

6:48

I'm scrolling and I'm asking you to look.

6:52

And if you're looking, no,

6:55

I'm not gonna show you arthritis of the first metacarpal phlange joint,

6:59

that would be boring.

7:01

Now I'm gonna show you where the patient stuttered with the

7:06

electrical saw and then cut the bone right there.

7:12

They cut the tendon and then they pulled back,

7:14

and then they jerked forward again, and then they cut the bone.

7:17

There is the bony fragmentation.

7:20

So it just illustrates the value of the t1.

7:23

I think you could easily blow by that abnormality on the T two weighted image,

7:28

but on the t1, you are missing a piece of bone.

7:31

It illustrates why all three C sequences are valuable. The T1 for the bone,

7:36

and for a general feel for anatomically what's happening.

7:40

The PD fat sat for detection,

7:42

the T2 for refinement of torn edges and H,

7:47

that's an FBL tear.