This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Upper Extremity, Subject name: Anatomy
Hyperextension at the metacarpophalangeal joints and flexion at the interphalangeal joints is caused by injury in the 
Select and explain. 
A. Ulnar nerve, B. Radial nerve, C. Median nerve, D. Musculocutaneous nerve
A: Ulnar nerve
Answer: A: Ulnar nerve 
Explanation: i.e. (Ulnar nerve): (59, 134-BDC-l 5th)An ulnar nerve lesion at the writ produces ulnar claw hand'CLAW HAND - due to the un opposed action of the long flexors and extension of the fingers, there is hyperextension at the metacarpo phalangeal joint and flexion at the interphalangeal joints involving the ring and little fingers - more than the index and middle fingers* If both median and ulnar nerves are paralysed the result is complete claw hand* Ulnar injury at the wrist can be tested by froment's sign