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: Surgery
Which of the following nerve is damaged in the fracture of the shaft of the humerus:March, September 2005 
Select and explain. 
A. Musculocutaneous nerve, B. Radial nerve, C. Ulnar nerve, D. Median nerve
B: Radial nerve
Answer: B: Radial nerve 
Explanation: Ans. B: Radial NerveRadial nerve injury occurs in up to 18% of cases of fracture shaft humerus.It is most common with middle third fractures, although best known for its association with Holstein-Lewis type distal third fracture, which may entrap or lacerate the nerve as it passes through the intermuscular septum.Most injuries are neurapraxias or axonotmesis; function will return within 3 to 4 months; laceration is more common in open fractures or gunshot injuries.Delayed surgical exploration should be done after 3 to 4 months if there is no evidence of recovery by electromyography or nerve conduction velocity studies.