Histopathologic study on enthesis. Involvement of spinal enthesis area in adjuvant rats

In adjuvant rats, the enthesoperidiscal area of spine, that is a small interspace between annular fiber of disc and spinal longitudinal ligament, is frequently involved in inflammatory changes. The initial changes are observed in this area 3 days after innoculation of adjuvant as well as synovium, subsynovial tissues, tendon sheath and intermuscular tissues. So this area seems to be reactive to inflammatory agents in the same way as the other reactive parts mentioned above. In enthesoperidiscal lesions, the vascular changes are not remarkable. They do not appear to initiate the peridiscal lesions. This circumstance is similar to the lesions of other parts mentioned above in the point that pathological changes are not evoked by initial vasculitis or perivasculitis. The authors have observed inflammatory changes not only in lumbar spine and tail with high frequency but also in cervical and dordal spine, but with low frequency. The enthesoperidiscal inflammation invades the enthesis of longitudinal ligaments and attachments of annular fiber to vertebral body in early stage (up to 17th day after innoculation). In these lesions, calcium deposits are recognized by von Kossa stain, but new bone formation is not observed by fluorescent study.