0:01

Just another example here in the Sagal imaging plane

0:04

and introducing a couple more areas of anatomy

0:07

or a couple additional areas of anatomy here at the level

0:11

of the PIP joint.

0:13

We have a thickening of the capsule

0:15

and the axial plane, very similar to the Sagal band of the

0:19

MCP joint.

0:21

This called the transverse reac ligament.

0:25

There's another structure that is, uh, very, um,

0:29

unique to this articulation at the level of the PIP and DIP

0:34

and that's the oblique reac ligament.

0:36

This is seen in about 50% of the population,

0:39

and it's shown here in this diagram

0:42

extending from the palmar aspect of the PIP joint

0:46

to the dorsal aspect of the DIP articulation.

0:50

So just so you're aware of these two structures, again,

0:54

showing those in the illustration as well

0:58

as here on axial images through the finger.

1:04

And when we look for signs

1:06

of particularly the oblique reac ligament,

1:10

we can see on plain film, uh, here as well as the mr the

1:15

enthesopathy osseous hypertrophy at the soft tissue

1:18

attachment site along the course of the phalanges

1:21

where those structures attach.

1:23

So just to be sure that you're aware of their existence

1:28

and particularly appearance here of the enthesopathy.

1:31

So let's think about the central slip injury here,

1:35

forced flexion on the extended finger.

1:38

And when that happens, you can have an acute avulsion

1:42

of the central slip.

1:44

Oh, what happened here? Sorry about that. There we go.

1:49

Um, and so when we have this central slip injury,

1:54

there can be no functional loss in this patient population.

1:58

And so often these people don't present

2:00

to the emergency room.

2:02

And if they, uh, do, we may see images

2:06

that look something like this.

2:07

And you've seen a million of these cases coming

2:09

through the urgent care that ed,

2:11

where a patient will have a plain film

2:13

and there will be focal dorsal soft tissue swelling at the

2:16

PIP and in those patients,

2:19

clearly a central slip injury can be within the spectrum

2:24

of findings that can happen.

2:25

So here as you look at,

2:27

there's your dorsal soft tissue swelling.

2:28

Here's your extensor tendon moving distally,

2:31

the disc continental slip.

2:34

Moving into the axial plane.

2:36

Here you see the discontinuity of the central slip.

2:40

No central slip visualized here, the low signal intensity,

2:44

lateral slips, green arrows pointing

2:46

through the central slip discontinuity yellow arrow heads

2:50

to the intact lateral slips.

2:53

Okay, so this is the acute central slip rupture.

2:57

Here's another example

2:59

With high resolution imaging.

3:00

As you're looking in the sagittal plane, in this case,

3:04

the central slip failure actually happened proximal to

3:09

that enal attachment, leaving a stump of the central slip.

3:13

Here they're the focal discontinuity.

3:16

Also identifying that on the T one and the T two images,

3:21

and here in this case also seeing on the post contrast

3:24

images synovitis around that articulation.

3:30

Another example here,

3:32

and when you've got underlying degenerative change,

3:34

it becomes a little bit challenging.

3:36

And as I looked at this case initially looking at the

3:39

central slip, I thought that it was intact,

3:42

but I was really fooled here by the presence

3:45

of the hypertrophic osteophyte formation.

3:47

Here you can see part of the central slip,

3:49

but no real attachment.

3:51

And this case, the lateral slips are intact,

3:54

but kind of distorted just based on the degenerative

3:57

change that's occurring here.

3:58

Some mild soft tissue swelling at the dorsal aspect

4:02

of the PIP articulation.

4:04

So if there's underlying degenerative change, you have

4:08

to be a little bit careful with respect

4:09

to the identification of that discontinuity.

4:13

And, and now, how does this re deformity occur?

4:18

Well, we said that with an acute central slip lesion

4:21

that there's no functional loss.

4:23

So if the patient doesn't self immobilize,

4:27

what can happen over the course of time is

4:30

that there would be fibrosis

4:32

and scarring around the structures of the PIP

4:35

and they would migrate to a palmar position.

4:40

And so you see with the central slip rupture over time with

4:44

that fibrosis and palmar migration of soft tissues, they

4:48

contract like a button hole.

4:50

And the PIP acts like a button popping up

4:53

through those fibrotic soft tissues

4:56

and hence the name of the type deformity.

5:00

And here is an example Sagal T one weighted image.

5:04

You're seeing the flexion at the PIP articulation,

5:07

the DIP off of our field.

5:10

In this case, as you look in the axial imaging plane

5:13

and on the sagittal plane, you see that you do not

5:17

identify the central slip attachment.

5:19

It's migrated proximally. This is a chronic binding.

5:22

And look at your two lateral slips migrating

5:25

to the more palmer aspect of the articulation.

5:28

Again, the fibrotic soft tissues

5:31

representing the button hole, the PIP, the button popping

5:35

through that button hole to be the deformity.