[Studies on induction mechanism of ossification of the posterior longitudinal ligament of the spine--especially on the cultured cells from the human spinal ligament].

To determine the mechanism of ossification of the posterior longitudinal ligament (OPLL) of the spine using cultured cells derived from the human spinal ligament, the ossification group and the non-ossification group were compared morphologically and biochemically. The results are as follows: 1) There is a difference in the characteristics of the two groups. The non-ossification group consists chiefly of fibroblast-like cells, while the ossification group consists chiefly of osteogenic un-differentiated mesenchymal cells. 2) In the ossification group, the posterior longitudinal ligament is composed of high osteogenic potential cells, with a resulting general tendency of systemic ossification. This systemic ligamentous ossification factor is a primary cause of OPLL. When localized anatomical stress and/or abnormalities of hormone and bone metabolism stimulate this ligament which is in a high osteogenic activity, this may result in initial ossification which may develop into the pathological OPLL.