Re: A plain radiograph in back pain
The AP radiograph provided shows apparently complete spinal ankylosis from at least the thoracic-lumbar region down to the sacrum. I would not therefore expect this man to have severe low back pain, worse at night unless there were a complication of his ankylosing spondylitis. A remaining mobile segment, which commonly shows marked degenerative changes or a transverse fracture (which can be extremely subtle in this condition) should therefore be suspected and further investigation undertaken.
Royal College of Radiologists guidelines indicate that back pain unrelieved by rest is a "red flag" and that MR is the investigation of choice, with plain radiographs restricted to specific circumstances.
Competing interests: No competing interests