Costovertebral joint changes in ankylosing spondylitis with thoracic pain.

CAT scan of the costovertebral joints has been performed in 17 patients with ankylosing spondylitis, all suffering from lower thoracic pain. Fourteen of them (82%) showed abnormal findings, including erosions and sclerosis, more pronounced in the vertebral side of the joint, and joint widening. Bony proliferation arising from the vertebral side in the anterior margin of the joint was also seen. One patient showed at the D12 level anterior bony bridges, similar to the vertebral syndesmophytes. Fusion was noted in five patients (including the three with longest disease duration) and represents the end result of the inflammatory process. These changes provide an anatomical basis for the understanding of the thoracic pain in AS patients.