What causes a clawed hand appearance in patients with ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

In addition to assessing sensation and testing individual muscle strength, inspection of the hand may reveal a clawed posture (main en griffe in French).

Several factors contribute to the clawed appearance. Wasting of the intrinsic muscles of the hand makes it look bonier. The fourth and fifth digits extend at the metacarpal phalangeal joint because the extensors at that joint are radially innervated, whereas the flexors are innervated by the ulnar nerve. Also, the fifth digit deviates slightly in the medial direction because the muscle that extends the fifth digit at the metacarpophalangeal joint is radially innervated and inserts on the ulnar side of the joint.

The fourth and fifth interphalangeal joints flex because the extensor muscles for these joints are also ulnar and because the natural tension of the muscles and tendons, in the absence of strong muscle activity in either direction, leads to flexion. The first three digits are extended at both the metacarpophalangeal joints and the interphalangeal joints because of the unopposed radial nerve innervation. All these factors make the hand look somewhat like a claw.

A different interpretation of the posture is that it looks like the hand gesture that a priest makes in the process of conferring a blessing. For this reason, it is sometimes called the benediction sign or the benediction hand.


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