Just a silly question about the flexor carpi radialus muscle

smellycat6464

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Could this muscle be agitated by "doing the worm" (as in the dance).

If so, could its improper treatment lead to Carpal Tunnel Syndrome? If not, is there a different muscle my character should be injuring? I imagine such a maneuver, done incorrectly, would damage more than one muscle, but I'm trying to craft some biologically accurate talk for two characters in the medical profession, and I want to use the right words.

Thanks and happy writing!
 

Pyekett

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Is the anatomy of carpal tunnel syndrome familiar to you, or would getting a technical explanation of the mechanics of CTS help?
 

smellycat6464

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All I know of carpal tunnel (or what I think I know), is that it occurs when inflamed tissue presses on the median nerve. I chose that muscle because it was close to the median nerve in the diagram I googled, and it is responsible for wrist flexion to some degree.

As per the specifics of what would/could be pressing into the median nerve is unfamiliar to me, so any anatomical insights you are willing to offer is much appreciated!
 

Pyekett

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Great. This should help your scene.

"Carpal" means "of or relating to the wrist." The carpal tunnel is a tunneled opening through the cage-like structure of thick connective tissue on the inside of the wrist--palm side, where the forearm meets the hand. It's the same general area where people feel for a pulse in the wrist.

If you are looking down at your wrist (palm up), the tight cage is made of a floor of wrist bones underneath and a ceiling of tough, fibrous ligament on top. That's the transverse carpal ligament [a.k.a. flexor retinaculum or anterior annular ligament], and it extends between the hook of the hamate & the pisiform on the pinky side to the tubercles of the scaphoid and trapezium on the thumb side. These bones are part of a set called the "carpals," because they are the bones of the wrist itself.

Picture of carpal bones here: http://droualb.faculty.mjc.edu/Cour...siology 50/Lecture outlines/05_23Figure-L.jpg

The space between the transverse carpal ligament and the carpal bones is a fixed space. There is not much, if any, stretch on any side, so if things start to swell, there is nowhere for the pressure to go except compressing other structures in the tunnel.

Picture of carpal tunnel (under transverse carpal ligament) here: https://gymnasticsinjuries.files.wordpress.com/2013/09/carpaltunnel.gif

These are the primary components of the tunnel:
-Flexor Digitorum Superficialis tendons (four in total)
-Flexor Digitorum Profundus tendons (four in total)
-Flexor Pollicis Longus tendon (one tendon)
-Median nerve, both sensory and motor components (sensory is to lateral 3 1/2 digits and palm, motor is to hypothenar muscles and lateral two lumbricals)

Of note for potential dialogue purposes, the ulnar nerve (the other main nerve serving the hand) passes through Guyon's canal, which is like a side entrance to the wrist over and above the carpal tunnel. That means the ulnar nerve does not go through the carpal tunnel. Same for the ulnar artery. The ulnar nerve and artery can get compressed as well, but that is a different syndrome from CTS.

Picture of Guyon's canal here: http://www.eorthopod.com/images/ContentImages/hand/hand_guyon_canal/hand_guyon_canal_anat02.jpg
[note that "flexor retinaculum" is another term for "transverse carpal ligament"--same thing]

So, for your purposes, you probably want to describe effects on one or more of the four sets of structures that do pass through the carpal tunnel. CTS particularly is about compression of the median nerve, often secondary to inflammation/swelling of one or more tendons in the carpal tunnel. Does this make sense so far? Is it helpful, or am I just yammering to hear myself talk? I do that sometimes. I'm old enough that I can't tell anymore.
 
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Pyekett

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To follow up on the OP, you had asked about the Flexor Carpi Radialis. The tendon for this muscle isn't technically in the carpal tunnel; actually, it's embedded in a wall of the tunnel (i.e., embedded in the transverse carpal liagment itself). So it is in a separate compartment than the median or the ulnar nerve.

Hmmm. You can think of the carpal tunnel tendons as body-building gorillas and the median nerve as one of those paper-lampshade long skinny lamps from Ikea. Suppose they are all packed into a cage made of a giant hammock (the TCL) stretched across a wall of bricks (the carpals). As the gorillas work out and get pumped up inside the hammock-cage, that lamp a'gonna get squashed.

If the flexor carpi radialis tendon is included, think of it as a gorilla in a baby sling attached to the outside of the hammock. It might get affected somewhat, but not as much as the guys in the cage. Or the lamp, bless it.
 
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smellycat6464

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Thank you for the in depth illustration of CTS! You cleared many things up, and now I know the flexor carpi radialus cannot compress the median nerve.

As a quick follow-up, do you think the flexor pollicis long, flexor digitorus profundus, or flexor digitorus superficialis would be agitated in doing the worm? If not, I may need to pick a different pathology to mention in the dialogue. I just picked CTS because most people probably have heard of it to some extent already.

Thanks again!
 

Pyekett

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As a quick follow-up, do you think the flexor pollicis long, flexor digitorus profundus, or flexor digitorus superficialis would be agitated in doing the worm?

Yes, especially if rolling onto and off of the fingertips, but really any movement that puts stress on the wrist in flexion would have some effect on these muscles.

Here is a video of one movement controlled by the FDP:
https://www.youtube.com/watch?v=ahwXumsN7d4 Note also that it has some role in wrist control.

This is FDS: https://www.youtube.com/watch?v=ZIGyzZiTexE