Microradiographic study of the intervertebral bridges in ankylosing spondylitis and in the normal sacrum.

The present knowledge of the pathology of ankylosing spondylitis is based on clinical radiology, on the macroscopic study of macerated vertebrae, and on histological studies mainly of decalcified material (Van Swaay, 1950; Forestier, Jacqueline, and Rotes-Querol, 1951; Aufdermaur, 1954; Engfeldt, Romanus, and Yden, 1954; Cruickshank, 1956; Ott and Wurm, 1957). An important step in the development of the syndesmophyte, that is the intervertebral bridge in ankylosing spondylitis, is the calcification of the outer part of the intervertebral disk. We therefore looked for a method that would allow the study of undecalcified material and that would provide a link between the methods used up to now. Such a method is microradiography. In children the sacral vertebrae are separated bones, like the other vertebrae. Sacralization starts about the age of 15. Jacobson and Driver (1932) have published statistical and histological data on this subject. However, the most extensive study is that of Schwabe (1933). So far as the vertebral bodies and disks are concerned, fusion is first obtained by bony bridges in the outer layers of the annulus fibrosus, as is the case in ankylosing spondylitis. In order to understand the latter pathological process, it might be interesting to refer to the normal ossification of intervertebral disks in the sacrum. Material and Methods Clinical Data Tissue was obtained from one case of ankylosing