Radiographic long follow-up study of ankylosing hyperostosis in spinal cord injured patients

The purpose of this paper is to investigate radiographic development of ossigication of the anterior longitudinal ligament to clarify the new bone formation. In this report, 30 patients with spinal cord injury were studied. The mean follow-up period was 15.5 years with a range from 5.4 to 31.0 years. The results were as follows : In the cervical spine, the narrowing of the intervertebral discs was more common in ankylosing hyperostosis group when compared to the non-anlylosing hyperostosis group. On the other hand, in the thoracic and lumber spines, cise versa. There is tendency to invrease the degree of thoracic kyphosis and decrease that of lumber lordosis in the ankylosing hyperostosis group. Considering that ossification was found prediminantly in the thoracolumber spine, we think the ”relaxation” of the anterior longitudinal ligaments participate somehow in the formation of ossification of anterior longitudinal ligament. The development of ossification was classfied roughtly into two groups. In one group it progressed slowly over a long period, and in the other group after rapid progression in early stage, it did not increase or was rather reduced as time passed. Concerning a direcrion of ossigication there was a tendency that in the cervical vertebrae it developed down and in the lumber vertebare it tended to develop down. According to the result of the long term follow-uo study, we think that the inportant factor in the development of ossification of anterior longitudinal ligament is not only diffuse ossifing diathesis but local biomechanical.