Q____________Upper limb==q56 - miracoli

[ArchivalUser]

__________attention NBME12___attention NBME12____________________
A 25 year old man comes to the physician after injuring his right elbow while trying to lift an 80-lb dumbell at the gym. When he attempted to lift the weight from the rack, he felt a popping sensation and pain his right elbow. He uses anabolic steroids. His pulse is 78/min, and BP is 150/95 mm Hg. Examination of the right upper extremity shows swelling of the antecubital fossa and ecchymoses from the antecubital fossa to the mid forearm on the anterior side. There is tenderness to palpation over the proximal aspect of the forearm. He is able to flex the elbow actively, but he is unable to flex the elbow or supinate the forearm against resistance. This patient has most likely injured a muscle-tendon unit that is supplied by which of the following nerves?
a) anterior interosseous
b) median
c) musculocutaneous
d) radial
e) ulnar

Please explain your answer

[ArchivalUser]

Brachioradialis muscle- radial nerve? DD

[ArchivalUser]

Pls explain why Brachioradialis muscle?

[ArchivalUser]

I was thinking that it was either the musculocutaneous nerve (biceps brachii and brachialis) which also flexes the forearm and supinate the hand, or the radial nerve which innervates the brachioradialis (flexion at elbow) and supinators of the hand. The difference between the two is that damage to the radial nerve would result in loss of sensation of the posterior arm and dorsal surface of the hand, and damage to the musculocutaneous nerve would result in loss of sensation of the lateral forearm. Since the question does not give any neurological symptoms, and the injury occured in the elbow, I chose radial nerve because i don't think the musculocutaneous extends so far distally that an elbow injury would affect it. The question states that he can actively flex and supinate, but cannot do so against resistance.

[ArchivalUser]

If you can actively flex and supinate, does that mean the musculocutaneous is intact? And unable to do so against resistance means the radial nerve is damaged?

[ArchivalUser]

In this case, is the injury to a nerve or to a muscle/s or its tendon?

[ArchivalUser]

Both bracihialis and biceps brachii muscles are innervated by the musculocutaneous nerve. However, brachialis is a pure flexor in contrast to biceps brachii which is a flexor as well as asupinator mm. If the biceps was torn one could still flex the elbow with the use of brachialis mm. Hence, my best guess is C.

[ArchivalUser]

Now that you asked about the tendon, and I look at the question again, the "popping" is probably a tear of the distal attachment of the biceps brachii, hence the answer would then be musculocutaneous

[ArchivalUser]

C is the ans
Great @dreamer2014&midnightsky