Review Question - QID 217056

A 65-year-old man presents to his primary care physician's office for a follow-up visit after a shoulder injury. The patient initially presented to the emergency department 4 weeks ago after falling from a ladder onto his outstretched hand. He was diagnosed with a right shoulder dislocation which was subsequently successfully reduced without complications. He now reports persistent right shoulder pain, swelling, and weakness. Physical exam of the right shoulder reveals mild edema, intact sensation over the deltoid muscle region, active range of motion limited to 80 degrees of abduction, full passive range of motion, and 3/5 strength with abduction. When lowering from a fully abducted position, the patient's arm suddenly drops to his side. Which of the following is the most likely diagnosis?