Radial nerve injury

[Wanderer HitchHiker]

While solving NBME 18 i noticed a question about radial nerve injury with weakness of elbow extension, obviously the answer was the injury at radial groove, but i think this isn't accurate at all.
As far as i know radial nerve injury at radialgroove spare triceps innervation and onnly affect wrist and fingers extension! what do you think?

Man comes to doc for cast removal. Fracture of left humerus that required open reduction, internal fixation, cast immobilization. Muscle strength is 2/5 with extension of elbow and 1/5 with extension of wrist and fingers. Patient most likely sustained a fracture at?

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[faisal 2000]

according to gray's anatomy mcqs

# Injury in the spiral grove (radial grove) : triceps will working properly because radial nerve supply it proximal to the spiral grove (radial grove of humerus). Abduction and extension of thumb, wrist drop, and Weakness of grip occur will occur. This may accompanied by bleeding from deep brachial artery.

q- A 23-year-old male medical student fell asleep in
his chair with Netter’s Atlas wedged into his axilla.
When he awoke in the morning, he was unable to extend
the forearm, wrist, or fingers. Movements of the
ipsilateral shoulder joint appear to be normal. Which of
the following nerves was most likely compressed, producing
the symptoms described?
A. Lateral cord of the brachial plexus
B. Medial cord of the brachial plexus
C. Radial nerve
D. Median nerve
E. Lateral and medial pectoral nerves

answer ; The radial nerve is the most likely nerve compressed to cause unable to extend the forearm, wrist, or fingers. This type of nerve palsy is often called “Saturday night palsy.” One reason for this nickname is that people would supposedly fall asleep after being intoxicated on a Saturday
night with their arm over the back of a chair, thereby compressing the nerve in the spiral groove. The radial
nerve innervates all of the extensors of the elbow, wrist, and fingers.

 

[Wanderer HitchHiker]

So I think it's an inaccurate question

 

[Rahas]

Its not just the radial nerve injury thats producing the weakness, but also the fact that his arm has been immobilized for a while. The clue is that the finger and wrist extension is weaker than elbow extension.

 

[Wanderer HitchHiker]

I understand your point but 2/5 is weak enough not to be considered a normal consequence of the immobilization

 

[Rahas]

I'm afraid I'm not clinically experienced enough to comment on that, although I also felt 2/5 was too weak. I also don't know how long this guy has been in the cast (was it mentioned?).

 

[Wanderer HitchHiker]

Nope, but it's the kind of question i despise because it doesn't make sense