PATHOMECHANISM OF SPONTANEOUS REGRESSION OF THE HERNIATED LUMBAR DISC- HISTOLOGIC AND IMMUNOHISTOCHEMICAL STUDY

To ascertain the pathomechanism of spontaneous regression of lumbar di sc herniation, histological and immunohistochemical studies on 100 her niated discs were performed. Inflammatory findings such as cell infilt ration, neovascularization, and granulation were observed in 16.9% of the protruded discs, 81.8% of the subligamentously extruded discs, 100 % of the transligamentously extruded disks, and 80% of the sequestrate d discs. The infiltrated cells were composed mainly of macrophages and a small number of T lymphocytes. Furthermore, the cell infiltration w as more prominent in the nucleus pulposus (NP) than in the annulus fib rosus (AF). There was no correlation between the occurrence rate of in flammatory response and the length of the period from onset to operati on. Based on these findings, it is considered that an extruded or sequ estrated disc has a potential to be resorbed by phagocytes.