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 person is not able to extend his metacarpophalangeal joint. This is due to injury to which nerve : 
Select and explain. 
A. Ulnar nerve, B. Radial nerve injury, C. Median nerve injury, D. Posterior Introsseus nerve injury
D: Posterior Introsseus nerve injury
Answer: D: Posterior Introsseus nerve injury 
Explanation: In radial nerve head surgery, the most common nerve to get injured is posterior interosseous nerve. There is thumb and finger drop. Extension of wrist is spared.