Review Question - QID 108520

A 25-year-old man presents to his primary care physician with lower back pain for the past 2 years. The patient works as a butcher and recently was moving heavy objects at work. His pain is worse in the morning and nothing improves it aside from swimming. The patient has a medical history of anabolic steroid use, acne, hypertension, and obesity. His current medications are hydrochlorothiazide, ibuprofen, topical benzoyl peroxide, and acetaminophen. On physical exam, there is no tenderness upon palpation of the spine. There is limited range of motion of the spine in all directions. His temperature is 98.6°F (37°C), blood pressure is 118/73 mmHg, pulse is 81/min, and respirations are 11/min. Which of the following is most likely to confirm the most likely diagnosis in this patient?