Can you recognise this sign on X-ray?
Mark is a 62-year-old mechanic who presents with several months of worsening mid-thoracic back pain.
Test your clinical know-how by taking the quiz below. If you select the wrong answer, have another go — you can try as many times as you like!
Dr Kate Kelso is a GP and medical editor at Australian Doctor.
Photo: BMJ; 2016