A passenger in a motor vehicle accident is brought into the emergency department by ambulance. On arrival, the only complaint she has is left shoulder pain, worse with inspiration. Exam shows a positive seat belt sign. Plain films of that extremity are negative; CXR notes rib fractures. The FAST exam and a CT scan are positive, and the patient goes to the operating room.
Challenge: Given the limited information presented here, what was the most likely injury? What is the sign described here?
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