What is a claw hand deformity?

Answer 1

Claw hands are a series of deformities that are the result of nerve injuries in the arm, particularly the ulnar, median and radial nerves. As a result of injury to any of the nerves a clawing of the specific fingers the nerve innervates in addition to sensory deficits in those areas. The deformities result as a result of unopposed positioning of the fingers. For example if the flexors are denervated the resultant positioning would be one that is extended because the extensors are now unopposed due to the lack of flexors.

For simplicity we observe the lumbrical muscles which are intrinsic muslces in the hand that flex the fingers at the metacarpal joints (MCP) and extend the fingers at both the distal and proximal interphalalingeal joints (DIP & PIP).

The ulnar nerve innervates the 4th and 5th lumbricals. Thus a denervation of the ulnar nerve would result in clawing in those fingers. specifically, the MCP joints of the 4th and 5th fingers would be extended and the DIP & PIP joints of the 4th and 5th would be flexed, resulting in the ulnar claw hand.

The median nerve innervates the 2nd and 3rd lumbricals. Thus the same results are observed only with the 2nd and 3rd fingers. In addition, the median also innervates a thumb muscle that is responsible for its opposable motion. Thus denervation of the median nerve may also result in the thumb loosing this ability and will instead fall into a flat plane with the other fingers and resemble that of an ape. thus the name ape's hand/claw.

The term klumpke's clawing refers to the denervation of all lumbricals in addition to the loss of radial nerve innervation. Thus in klumpke's clawing, all the fingers are extended at the MCP joint and flexed at the DIP and PIP leading to clawing of all fingers (similar to the gesture of tiger clawing motion).

Answer 2

A claw hand deformity is when a persons hand is like a claw that you'd see on a crab. It's a birth defect. On the claw there's the thumb and the rest of the finger are joined together to make it look like a claw.