0:01

So let's finish up in the last five minutes

0:04

or so, uh, with the discussion of the pulley system

0:08

of the flexor tendon.

0:10

So we talked about the flexor tendon system already.

0:13

We briefly introduced the idea of the pulley

0:16

as being this fibrous tissue that anchors the tendon down

0:19

to bone, and it does so through the annular

0:23

and cruciform pulley system.

0:25

The annular pulley's quite substantial.

0:28

You can see them here

0:29

and they're relatively, uh, similar to this proportion.

0:33

So a one fairly small a to the largest

0:35

and most substantial pulley.

0:38

So a one, A three, A five at the level

0:41

of the M-C-P-P-I-P and DIPA two

0:45

and a four at the level of the proximal

0:47

and middle phalanges, the cruciform pulleys,

0:51

very delicate residing between the annular pullies

0:55

and those are pretty tough to see with standard MR imaging,

0:58

at least high resolution imaging, we can sometimes see them.

1:04

I wanted to show you

1:06

this specimen photograph here.

1:09

You've got a probe that's underneath the A two pulley,

1:13

and this appearance almost doesn't appear

1:16

like a biologic tissue.

1:18

It's almost like sheet plastic.

1:20

And if you take that probe

1:21

and pull up on it, nothing will happen to the po.

1:24

These are super, super tough.

1:27

You have to actually either take a scissors and incise it

1:30

or a scalpel and cut it very tough.

1:32

So these are incredibly strong structures.

1:37

This, believe it or not, was acquired with a 1.5 Tesla

1:42

MR scanner and a small little microscopy coil placed

1:47

at the level of the PIP joint.

1:49

And so it just shows you the power of some

1:51

of these small microscopy coils

1:53

that can give you super high resolution.

1:56

So look at the palmar plates.

1:58

Here are the extensor tendon attaching to base metal balen.

2:02

Here are your flexor tendon.

2:04

Looking at the pulley system,

2:06

this big substantial a two pulley here, um,

2:09

across the board.

2:10

So a two, a three, a four,

2:13

and even the delicate little crucifer pulls you can actually

2:16

start to see with super high resolution Mr.

2:19

So remember that the function of the pulley system,

2:22

when you flex the fingers to hold that tendon down

2:25

to the bone and really allow you to have full flexion

2:29

without the pulley system,

2:31

if we forced flexion across the finger,

2:33

you would have this entity called bow stringing.

2:36

That means that the tendon would separate

2:39

from the bone like the string of a bow.

2:42

The osseous structures representing

2:44

the backbone of that bow.

2:45

And that indirect finding is how historically this

2:50

diagnosis was made with CT forced flexion, identifying

2:54

that gap that would occur, the bone string between the.