0:01

With respect to Lumbricals, we did a detailed study,

0:05

a Don, uh, mini patria, one of our colleagues

0:08

and one of our junior faculty, Karen Chang, with uh, one

0:12

of our past visiting scholars

0:13

and now postdoctoral scholars, aria Mohan Borges,

0:16

who does these beautiful illustrations.

0:18

And so when we think about the lumbricals on the left

0:22

showing the normal anatomy,

0:24

and you can see that the attachments here

0:26

for one radial side of the extensor two

0:30

and three here, you're going to see radial

0:32

and ulnar, uh, for the attachments of the third, same

0:36

for the fourth radial

0:37

and ulnar aspects of those tendons

0:39

with distal attachment sites,

0:40

the extensor apparatus, radial side.

0:43

As we went through an anatomic dissection

0:47

and imaging of the lumbricals, we found

0:49

that there were some variations in the insertions.

0:52

And not that there incredibly common,

0:55

but for you to be aware of those just important.

0:58

And the idea that once you find your lumbrical,

1:02

follow them proximal end distal to be able

1:04

to understand whether those variations are in place

1:07

and to see then whether injuries are occurring.

1:10

Here's a dissection with that lumbrical,

1:13

the dorsal extensor, uh, expansion.

1:17

And you can see how that attachment really occurs

1:20

with the dissection.

1:21

Uh, we had one of our hand surgeons also help us

1:24

with this looking in the coronal and the axial plane.

1:28

Here you're at the level of the flexor tendons.

1:30

You can really get a nice idea of the relationship

1:34

of the lumbricals with respect to the tendons

1:36

and how they move from proximal to distal.

1:41

So here are a few of the variations

1:43

that we saw in this case.

1:45

Two and three attached in this way on the radial

1:49

and NAR aspect of that third extensor tendon.

1:53

And really the key when you're looking at the MR images is

1:56

just to cross reference the coronal

1:58

and the axial imaging plane and follow things distally.

2:02

Another variation.

2:04

We saw a lumbrical attachment that actually went

2:06

to the palmar plate.

2:08

This is nice, I think, for you to be aware of.

2:10

Just that when you see this structure that looks kind

2:13

of distorted and really big towards the hallmark plate,

2:16

you can follow it proximally to really be able to understand

2:20

that this is a variation in the anatomy

2:23

of the lumbrical attachment

2:25

and not some sort of mass that you're identifying

2:28

that's pathologic in nature.

2:31

And in this case, the lumbrical attachment went

2:33

to the radial base of the proximal phx rather

2:37

than more distal.

2:38

Again, looking in this case, in the sagal imaging plane

2:41

and following those on sequential axial images.

2:45

And that's really the key.

2:46

So follow them anatomically

2:48

and understand that those variations can occur

2:51

and we see those commonly throughout the body.

2:55

So let's look at some pathology. So if you're

2:58

Asked to do the imaging of the hand

3:00

and you start to see things in the lumbricals, don't panic.

3:04

Just go back to a few illustrations

3:06

and diagrams to remind yourself of the anatomy.

3:10

I, I like this case

3:11

because it shows not only the strain, so

3:14

that feathery high signal intensity within the lumbrical,

3:18

but it also shows focal discontinuity through this lake

3:22

or pool of high signal intensity that

3:26

representing the torn fibers.

3:28

Another example here with strain, that feathery pattern,

3:32

but we don't see a lake of high signal intensity consistent

3:35

with discontinuous or torn fibers here.

3:40

Infectious myositis in this case.

3:43

Look at the lumbricals here.

3:45

We don't see focal areas of discontinuity.

3:48

I think it's very nice

3:49

to look in the axial imaging playing the asterisk here

3:52

with the lumbricals.

3:54

And of course the arrow heads

3:56

are showing you the dorsal interosseous muscles.

4:00

So this in a person with an infectious myositis

4:03

with a 59-year-old gentleman who had five day history

4:06

of swelling, elevated inflammatory markers with all

4:09

of this high signal intensity diffusely

4:12

throughout these structures.

4:15

And in this case a post-traumatic injury.

4:19

So fifth metacarpal feal, um, pain

4:22

after injury

4:24

as you look at the T one fluid sensitive sequence,

4:27

linear low signal intensity here.

4:29

So this was a fracture line non-displaced in nature.

4:33

And as you looked at the associated muscle edema,

4:37

lumbrical palmar interosseous muscle

4:40

and opponents digit minimi all have altered signal

4:43

intensity in this case.

4:44

But no areas of confluent lakes of high signal intensity

4:48

to suggest large areas of muscle tear.

4:52

So you can be very specific with respect

4:55

to your reporting once you familiarize

4:57

yourself with this anatomy.

4:59

And that's, I think, super helpful

5:01

as you're considering your approach

5:03

to these different imaging studies.