Pathology of the dorsal spine in ankylosing hyperostosis.

Abstract

While the pathological features of the spine in ankylosing spondylitis have been described in considerable detail in recent years, little published work is available on the subject of the pathology of the spine in ankylosing hyperostosis (AH).We here describe some of the pathological findings in the dorsal spines of twenty subjects with AH. Materials and methods SELECTION OF SPECIMENSDorsal spines were removed from twenty subjects at postmortem examination. They were judged to have AH on the basis of the presence of syndesmophytes in the form of bony flanges or bridges situated predominantly on the right anterolateral aspect of the bodies of two or more vertebrae, and the absence of previous clinical findings or other spinal pathology which could account for these features. Radiographs of the dorsal spines taken during life and post-mortem were examined independently by a radiologist and a rheumatologist who confirmed the diagnosis of AH in all the cases included in this study. The twenty cases of AH used in this study were selected from about 500 autopsies where one of us (B.V.-R.) was personally able to examine the spine in each case, and excluded from the study were about ten other cases of AH where removal of the spine was not possible for a variety of reasons. The overall incidence of AH in patients coming to autopsy at The London Hospital is therefore in the region of 6 %. The twenty subjects comprised eleven males of mean age 66 years (range 58-77 years) and nine females of mean age 71 years (range 53-87 years). Details of the age, sex, extent of the dorsal spine affected, and the principal cause of death in each subject are shown in Table I. EXAMINATION OF SPECIMENSAfter removal from the body, each dorsal spine was cleaned and photographed. Each specimen was then radiographed using a Faxitron 8050-010 X-ray Inspection System (Field Emission U.K. Limited). After photography and radiography, 18 of the spines were divided into longitudinal slabs 0 5 cm thick using a band-saw, and the internal features were noted. Selected portions of these slabs were then taken for histological processing for subsequent microscopical examination. They were fixed in formol-saline and embedded in methyl methacrylate; 8 um sections were made and were stained with haematoxylin and eosin, thionin, and by the von Kossa technique. One severely affected spine and one moderately affected spine were macerated for the examination of the dry specimens by being boiled in 5% sodium hydroxide to remove the soft tissues, followed by bleaching in 10 vol hydrogen peroxide. Results EXTERNAL FEATURES OF DORSAL SPINE IN AHIn 13 of the 20 specimens the condition was confined to the lower half of the dorsal spine; in the remainder, the upper half was also affected (Table I). In all cases at least 4 contiguous vertebral bodies were involved; involvement of the whole of the dorsal spine was present in only one case. The lower part of the affected portion of each spine tended to be more severely affected than the upper, though a region of larger syn...

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