0:01

Let's move now to a discussion of the more distal finger.

0:06

Uh, I'm just gonna introduce to you, um,

0:10

quickly in a superficial fashion

0:12

and we're gonna dive into each

0:13

of these areas in much more detail.

0:16

The extensor hood.

0:17

And I think part of the problem

0:19

as you're thinking about the extensor hood

0:21

and the next image is gonna give you an overview, um,

0:25

with a detailed illustration

0:26

of the palmar soft tissue

0:28

supporting structures of the finger.

0:30

It almost becomes overwhelming when you start

0:33

to look at these very, um, very detailed

0:38

and intricate diagrams.

0:40

But as we start to kind of delve down and,

0:42

and divide this into specific areas, you're gonna see

0:46

that this anatomy can be very approachable.

0:48

So it's complex for sure.

0:51

We're gonna be dealing with a lot

0:52

of different structures here,

0:53

but I promise you it will be easily manageable here.

0:57

Your preview of the extensor hood,

0:59

and here your preview

1:01

of palmar cited supporting soft tissue structures moving

1:05

from the metacarpal phal joint proximally

1:08

to the distal aspect of the uh, finger.

1:13

So we want this to be approachable.

1:16

So let's try maybe a more Homer Simpson style

1:20

to building this joint.

1:21

We're gonna start with lesser metacarpal phal joints.

1:25

And by a lesser, I'm saying I'm not dealing

1:27

with a thumb anymore.

1:29

I'm dealing with 2, 3, 4, 5.

1:31

And so here I'm showing you an a sagittal vantage point,

1:34

the metacarpal and the base of the proximal phalanx.

1:38

Let's build this articulation by adding a palmar

1:41

or vol plate triangular low in signal intensity,

1:46

usually fairly tightly attached to the palmar base

1:49

of the proximal phalanx.

1:51

That proximal attachment to the metacarpal,

1:54

perhaps a little bit more proximal than you may, uh,

1:58

assume it's probably three

1:59

or four millimeters proximal to the head neck junction

2:02

of the metacarpal.

2:04

Let's add in collateral ligaments, both radial and ulnar.

2:07

Let's place our extensor tendon

2:10

and our flexor tendon, those complexes in place.

2:16

Let's then add a pulley at the level

2:19

of the metacarpal phlange joint.

2:21

That's gonna be a fibrous type tissue

2:23

that holds the flexor tendon complex

2:26

to the metacarpal feal joint.

2:28

We'll talk about that as our last topic today.

2:31

And of course, we're going to have that sagittal band

2:34

that I already showed you a little bit of pathology

2:37

with in the pseudo center lesion.

2:39

And while the sagittal band suggested something

2:42

that should be in the sagittal imaging plane,

2:44

it is a thickening of the capsule in the axial plane at the

2:47

level of the metacarpal falange joint that helps stabilize

2:51

the extensor tendon as well as all of the other structures

2:55

of the metacarpal falange joint.

2:58

And so here is a much more elegance diagram

3:02

of the structures that we just talked about.

3:04

However, all the things that are here we sort

3:08

of talked about already,

3:09

and we built that from our own understanding of osseous

3:13

and soft tissue stabilizing structures.

3:18

So when we consider injuries

3:20

to the lesser metacarpal phal articulation,

3:24

simple versus complex, meaning if you have a dislocation

3:27

or severe subluxation, then the capsular insufficiency,

3:31

that results would remain in situ tube.

3:34

But with a complex subluxation

3:37

or dislocation, there could be incarceration

3:40

of those soft tissue structures.

3:42

Dislocation here is less common than at the

3:45

phalangeal joints.

3:47

Injury most often occurs at the index finger

3:50

with a dorsal displacement.

3:51

And again, that designation

3:53

of simple versus complex shown in the illustration.

3:58

Let's look at this sagal image

4:00

through a metacarpal phal joint.

4:02

And it speaks to the idea that often patients present

4:05

to us sub acutely and not acutely.

4:09

When patients present to us acutely,

4:11

we have the added benefit in some cases

4:13

of having contrast within the articulation descending

4:17

capsular structures.

4:18

We've got a lot of altered signal intensity in the bone

4:21

marrow and the soft tissues that really help us

4:24

to figure out what happened in finger injuries specifically.

4:29

Um, plain film evaluation,

4:31

even cross-sectional imaging can sometimes be very

4:34

challenging because patients will often present like this

4:37

with the finger or the injured area inflection.

4:40

And so in the sagittal imaging plane,

4:42

we have clues to what's happening.

4:44

Let's follow the puli cortex of the proximal vein length.

4:47

We can see the irregularity discontinuity remnants

4:52

of altered signal intensity.

4:53

Here at the Palmer base, you see the distortion

4:56

of the Palmer capsule.

4:57

Looking at the metacarpal head, again, the remnants

5:00

of altered signal intensity at the dorsal aspect

5:03

of the metacarpal.

5:04

So what do we think happened?

5:07

How about that dorsal dislocation with a spontaneous

5:11

or perhaps aided reduction.

5:14

When people have a dislocated finger, they don't walk around

5:16

with a dislocated, they pull on it and they reduce it.

5:19

And so this is how people present to us.

5:22

And so by being a bit of a sleuth, looking at the remnants

5:26

of this acute binding, now presenting sub acutely,

5:30

we can identify what happened with this patient.

5:35

Let's look at another example

5:36

of pathology at the metacarpal falange articulation.

5:40

Look at alignment. In this case, sometimes

5:42

with cross-sectional imaging, we forget

5:45

to think about the big picture stuff like alignment,

5:47

because here I'm showing you a single image,

5:50

but obviously when you're looking at CT

5:52

or mr, you're looking at multiple consecutive images.

5:55

And so in those cases,

5:56

sometimes the alignment doesn't pop out at you.

5:59

But clearly we've got subluxation here of the proximal phx

6:03

with respect to the metacarpal.

6:05

Look at the palmar plate. It looks irregular.

6:07

Look at the distension of the articulation.

6:09

Clearly high signal intensity.

6:12

Now I'm showing you sequential T one weighted images.

6:17

As you look at this area here

6:19

where we saw joint distention on the gradient sequence,

6:22

look at the T one, in this case slightly heterogeneous,

6:26

but the majority of this soft tissue,

6:29

I'm gonna call it soft tissue

6:30

because as I look at the signal intensity,

6:32

it's brighter than the intrinsic standard of muscle

6:36

to me on T one.

6:38

That suggests that the majority

6:40

of this is synovial hypertrophy and not simple joint fluid.

6:44

Look at this image.

6:45

Do you see the focal area of lower signal intensity?

6:48

That's the bit of fluid.

6:50

The rest of this is synovial hypertrophy.

6:53

So let's look at more sequential images to try

6:56

to figure out what's going on here.

6:58

What do you think about that? How about that?

7:01

These are clearly erosive changes.

7:04

The chronic inflammatory process here was

7:07

rheumatoid arthritis.

7:09

So in this case, erosive change led to capsular laxity,

7:13

abnormality of the palmar plate

7:15

and subluxation axial image.

7:20

Here, this is a gradient imaging sequence looking at the

7:23

level of the metacarpal phlange joints.

7:25

Here you're seeing distortion at the radial aspect

7:28

of the fifth metacarpal falange articulation.

7:32

Looking at another cut, look at the distortion

7:35

of the capsular structures.

7:36

There's your flexor tendon, there's your extensor tendon

7:40

ulnar cited capsule, linear low signal intensity.

7:43

Look at the adjacent metacarpal falange joint as a standard

7:46

for what that radial collateral capsule should look like.

7:50

Clearly distorted here moving into the

7:53

coronal imaging plane.

7:55

And sometimes this happens when you're dealing with, uh,

7:59

you know, off ISO center imaging of the hand.

8:02

You can get heterogeneous fat suppression.

8:04

In those cases, if you know that's gonna happen

8:07

is your T one for the higher resolution imaging structure

8:10

imaging sequence.

8:11

And then you can do an inversion recovery to be able

8:14

to really help you identify areas

8:17

of altered signal intensity.

8:18

No surprise. Here you're seeing altered signal intensity at

8:22

the ulnar aspect base proximal linx

8:25

altered signal intensity.

8:27

Here at the ulnar aspect of the metacarpal falange joint.

8:30

We know that there's distortion

8:32

of the radial collateral ligament.

8:34

Look at high signal intensity extending proximally.

8:37

Along that metacarpal,

8:39

what do we think the mechanism of injury was?

8:42

Severe subluxation with ulnar impaction

8:45

and tensile force at the radial aspect of

8:48

that articulation resulting in the capsular injury.

8:52

So once you know the structures that

8:54

You're dealing with, the findings

8:56

that you see in every injury all over the body,

8:59

the mechanism becomes easy for you to identify.

9:03

And then you can also try to predict those abnormalities

9:07

that you'll see in the soft tissue structures as well

9:09

as the bone.