Review Question - QID 210285

A 36-year-old man presents with acute onset of pain in his left shoulder and arm. The pain began after a pick-up football game 10 days ago. He localizes the pain to the lateral and posterior aspect of his arm and describes it as an aching sensation. He also reports numbness over the dorsal forearm and long finger. On physical exam, his pain is alleviated when abducting and elevating his arm. He also has weakness with long finger extension. Radiographs are shown in Figures A-D. Which of the following is the most likely diagnosis and finding that would be seen on a magnetic resonance imaging study?