Review Question - QID 216279

A 6-year-old boy is brought to the emergency department by his father for elbow pain. He was riding his bicycle when he fell onto his outstretched right hand. He immediately clutched his right elbow in pain and began crying. He refuses to move his elbow. He has no medical problems and takes no medications. His temperature is 98.4°F (36.9°C), blood pressure is 108/64 mmHg, pulse is 100/min, and respirations are 20/min. On exam, the boy is holding his right wrist with his left hand and cries upon palpation of a region that is 2 cm proximal to his elbow. The radial head is palpated just distal to the lateral epicondyle. He is unable to make a pincer with his right thumb and index finger. When asked to hold a pen between his right thumb and index fingers, he drops it. The radial pulse is diminished on the right. Which of the following is the most likely diagnosis?