An 8-year-old boy falls from the playground slide on a flexed left elbow and suffers a flexion type, fully displaced closed flexion type supracondylar fracture. He complains of some finger numbness in the emergency depament, but will not let anybody close enough to examine his arm. Which of the following is most likely injured in this fracture

Although the anterior interosseous nerve is most commonly injured in extension-type supracondylar fractures (by far the most common type of supracondylar fracture), the ulnar nerve is more commonly injured in flexion -type supracondylar fractures. The brachial aery is potentially injured, albeit rarely, with flexion-type injuries. The radial aery does not branch until the brachial aery trifurcation, which occurs distal to the elbow. Radial nerve injury is the second most common form of nerve injury in extension-type fractures.