A 24-year-old man is brought to the emergency department due to right arm pain after a fall. While rock climbing at a nearby national park, the patient lost his grip and fell approximately 3 m (10 ft) onto the boulders below. He says, "I landed on my right arm and heard something snap." The patient did not strike his head or lose consciousness. He has no chronic medical conditions and takes no daily medications. Vital signs are within normal limits. Physical examination shows extensive bruising over the lateral right arm and a total inability to extend the right wrist. X-ray reveals a midshaft fracture of the right humerus. Which of the following arteries is most likely to be injured in this patient?
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This patient has a humerus fracture associated with wrist drop, suggesting a radial nerve injury. The radial nerve is a terminal branch of the brachial plexus that carries fibers originating in the C5-T1 nerve roots. It innervates most of the forearm extensors at the elbow (eg, triceps) and most of the hand extensors at the wrist. It also innervates the extrinsic extensors of the digits and the brachioradialis and supinator muscles. In addition, the radial nerve provides cutaneous sensory innervation to the dorsal hand, forearm, and upper arm.
Radial nerve deficits due to a midshaft humeral fracture raise concern for an associated injury to the deep brachial artery. The deep brachial (profunda brachii) artery branches off the brachial artery high in the arm, passes inferior to the teres major muscle, and courses posteriorly along the humerus in close association with the radial nerve.
(Choice A) After giving off the deep brachial artery, the brachial artery continues anteromedially until it branches to form the radial and ulnar arteries in the forearm. Supracondylar fractures of the humerus may injure the distal portion of the brachial artery but are unlikely to injure the radial nerve or cause wrist drop.
(Choice B) The common interosseous artery is a short branch of the ulnar artery that gives rise to anterior, posterior, and recurrent branches within the proximal forearm.
(Choice D) The anterior and posterior circumflex humeral arteries are branches of the axillary artery that form an anastomosis encircling the surgical neck of the humerus in the quadrangular space. The axillary nerve travels in close association with the posterior circumflex artery, and a fracture to the surgical neck of the humerus may damage them.
(Choice E) The deep brachial artery divides into the radial and middle collateral arteries. The radial collateral artery also courses with the radial nerve, but injury to this artery from a midshaft fracture is less likely because it originates at the lower end of the spiral groove.
Educational objective:
The deep brachial (profunda brachii) artery and radial nerve run together along the posterior aspect of the humerus. Midshaft fractures of the humerus risk injury to these structures.