Froment's sign

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Froment's sign tests for palsy of the ulnar nerve, specifically, the action of adductor pollicis. To perform the test, a patient is asked to hold an object, usually a piece of paper, between the thumb and a flat palm. The object is then is pulled away. A normal individual will be able to maintain a hold the object without difficulty. However, with ulnar nerve palsy, the patient will experience difficultly maintaining a hold and will compensate by flexing the FPL (flexor pollicus longus) of the thumb. Clinically, this compensation manifests as flexion of the DIP joint of the thumb (rather than extension, as would occur with correct use of the adductor pollicus). Note that the FPL is normally innervated by the anterior interosseus branche of the median nerve.