Review Question - QID 216394

A 33-year-old man presents to the emergency department after a motor vehicle collision. The patient was an unrestrained driver in a head-on collision and sustained significant injuries to his left arm which was outside of the window of the car. The patient complains of elbow pain and pain in his arm. He has no significant past medical history and takes no medications. His temperature is 98.7°F (37.1°C), blood pressure is 123/82 mmHg, pulse is 88/min, respirations are 15/min, and oxygen saturation is 99% on room air. Physical exam reveals tenderness over the humerus and elbow with weakness of wrist extension. There is full, painless range of motion of the left upper extremity. Radiographs are performed demonstrating a mid-shaft humeral fracture and a small, non-displaced fracture of the olecranon. The patient is transferred to the medical floor after he recovers. On hospital day 14, the patient notes he has a "pins and needles" sensation in his hand. There is numbness over his ring and little finger of his left hand and minor atrophy of the interossei of his left hand. Which of the following is the most likely etiology of his current presentation?