Clawing of hand

[Lothric]

Yo,

FA 2017 says that with distal lesions of median or ulnar nerves comes the exaggeration of the loss of lumbricals due to the remaining extrinsic flexors of the digits --> fingers extend at MCP, flex at DIP and PIP joints.

I don't get it. What is meant with "remaining extrinsic flexors"? If the median nerve is damaged, so will (apart from the second and third lumbrical) the other flexors in the forearm affecting the digits. And even if they weren't damaged; why would they suddenly do the opposite of the lumbricals by extending at MCP and flexing at the DIP and PIP joints?

Somebody clarify this!

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[Surgeria]

As I understand this concept is that median nerve + ulnar nerve innervate lumbricals flexing mcp da extending the dip and pip. when you loose median nerve or ulnar nerve, you loose the ability to flex the mcp and extend the dip + pip = so your hand will extend at mcp and flex at dip+pip. I think no need to go beyond this as log as we are not hand surgeons ))

 

[iBS1972]

Claw hand is classically used to describe when a patient is unable to flex their 4th and 5th MCP joint and extend their 4th and 5th PIP joint, typically due to ulnar neuropathy.
Why does ulnar neuropathy cause this problem? ulnar nerve innervates the 3rd and 4th lumbricals. The lumbricals are in charge of simultaneous MCP flexion and PIP extension (lets you use puppets).

Hope this helps!