[Development of spondylodiscopathies in ankylosing spondylitis].

This multicentric study concerns 43 cases of spondylodiscopathies considered, as far as evolution is concerned, according to their radiological aspect. Late erosive forms (33 cases) occur on a rigid spine, sometimes after a trauma (6 cases). The initial radiological sign may be the fracture of a syndesmophyte or of the posterior arch. The evolution of the signs (pinching, erosions, density) is variable: slow or rapid aggravation leading sometimes to an osteosynthesis, extended stabilization over several years, cure by presence of a syndesmophyte or a bony block which, beside an obvious mechanical etiology in most cases, predicts the intervention of an inflammatory factor, isolated or concomitant. Early erosive forms (3 cases) occur in a context of inflammation, on a healthy spine, and sometimes are multifocal and lead rapidly to the formation of bony blocks: they join directly in the evolution of ankylosing spondylarthritis. Pseudo-Pott and pseudo-dystrophic forms (7 cases) present a variable evolution and their interpretation remains debatable.