Review Question - QID 210856

A 27-year-old man is brought into the emergency department after a car ran into him while he was riding his bike. The patient is conscious and alert. He states that his arm is in pain and he is requesting morphine. The patient's past medical history is non-contributory and he is not currently on any medications. His temperature is 97.5°F (36.4°C), blood pressure is 124/65 mmHg, pulse is 122/min, respirations are 15/min, and oxygen saturation is 98% on room air. An initial splint is placed. A radiograph is performed (Figure A). Physical exam is notable for the findings in Figure B when the patient is asked to extend his fingers. Which of the following nerves has mostly likely been affected by the injury?