Case

A 43yo is involved in a motor vehicle accident. The driver used a standard three point restraint in a sedan vehicle and was impacted in the side by a pickup truck. The patient has multiple injuries including a displaced left arm mid-humeral fracture causing considerable mid-arm pain. The patient indicates an inability to open their left hand and loss of sensation to a portion of their left hand. Their hand is warm and the patient is able to grasp your hand with theirs

Question 2/3 - Which of the following muscle(s) are most likely impaired by this injury?

Click on your selected option(s) below  (correct = 2, over-thinking = 3+)

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Incorrect. Pronator teres is a muscle of the anterior forearm compartment (innervation by the median nerve) near the elbow, one of the muscles responsible for the action of pronation.

Incorrect. This is a muscle of the anterior forearm compartment (innervation by the median nerve), one of the responsible for the action of wrist flexion.

Incorrect. The digital flexor muscles (flexor digitorum superficialis and flexor digitorum profundus) are anterior compartment muscles, which has innervation mostly from the median nerve with profundus haveing half the muscle innervated by the ulnar nerve.

Incorrect. Pronator quadratus is a muscle of the anterior forearm compartment (innervation by the median nerve) near the wrist, one of the muscles responsible for the action of pronation.

Correct! The radial nerve is the nerve of the posterior arm/forearm, which are the extensor compartments of the upper limb.  Thus, any muscle in these posterior compartments distal to the injury could be impaired.

As the patient reports inability to extend the fingers the possible dysfunction is consistent with physical examination and patient history.

Correct! While this is sometimes considered an anterior muscle, it sits 'halfway' coursing on the radius side of the forearm. Innervation is from the radial nerve, so from a neurological standpoint it is a 'posterior' muscle despite the position being a little more to the anterior side.

Incorrect. This muscle is a flexor of the thumb, all the thumb musculature is controlled by the median nerve, not the radial nerve.