Pseudoarthrosis in ankylosing spondylitis mimicking infectious diskitis: MR appearance.

A 73-year-old woman with suspected infectious diskitis was transferred to our institution. She had a 1 0-year history of ankylosing spondylitis and had had progressive kyphosis with intermittent pain in the thoracolumbar region for almost a year. She had no history of trauma, and her spine was nontender. She was afebrile, and her WBC count was normal. Plain films and tomograms of the thoracolumbar spine (Fig . 1A) showed a large zone of destruction involving the T11-T12 disk and adjacent vertebral bodies contiguous with a fracture through the posterior elements of T1 1. CT (Fig. 1 B) confirmed these findings and , in addition, showed paraspinal soft-tissue swelling. MR (Figs. 1 C and 1 D) showed the signal characteristics of the involved region . Cultures of material obtained percutaneously and intraoperatively from the fibrous disk space were negative for bacteria, fungi, and mycobacteria. The destructive changes have not progressed during the 2 years since posterior spinal fusion , and the patient remains asymptomatic.