Froment's sign is due to

Ans: A Ulnar nerve injury(Ref: Maheshwari 4h/e p. 65)Ulnar nerve injury:Adductor pollicis will be paralysed.Shows 'Froment's sign'or the'book test'.Procedure:The patient is asked to grasp a book between the thumb and index finger. Normally, a person will grasps book firmly with thumb extended, taking full advantage of adductor pollicis and the first dorsal interosseous muscles.Patient will hold the book by using the flexor pollicis longus (supplied by median nerve) in place of the inter-phalangeal joint of the thumb.This becomes more pronounced if the examiner tries to pull the book out while the patient tries to hold it.