A 12-month-old girl is brought to the emergency room by her father. He states that she has not been moving her arm and has been more irritable than usual. A radiograph of the elbow is depicted in Figure A. On examination of her lower extermities, she has mild tenderness and prominence over her left thigh but does not have any bony instability. A radiograph of her left thigh is shown in Figure B. In addition to a complete history and physical, management should include which of the following?