This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anatomy
A 37-year-old patient presented to you with hyper-extension of 4th and 5th metacarpophalangeal joint with flexion at proximal interphalangeal joint. This deformity is due to injury to: 
Select and explain. 
A. Deep branch of ulnar nerve, B. Median nerve, C. Radial nerve, D. Superficial branch of median nerve
A: Deep branch of ulnar nerve
Answer: A: Deep branch of ulnar nerve 
Explanation: Ans: A. Deep branch of ulnar nerve(Ref: Gray's 41/C p784, 866, 40/e p888)Deformity = Claw hand.Due to injury of deep branch of ulnar nerve.