The significance of the cervical soft disc herniation in the ossification of the posterior longitudinal ligament.

The significance and role of cervical soft disc hernia in ossification of the posterior longitudinal ligament were investigated based on 54 surgical cases. The types of ossification of the posterior longitudinal ligament were divided into three sub-types: segmental, continuous, and mixed types. In the current series, there were 29 segmental type, 12 continuous type, and 13 mixed type. In the 29 segmental type, 23 patients had accompanying cervical disc hernias (79%). In the 12 continuous type, only 2 patients (17%), and in the 13 mixed type, 5 patients (33%), had accompanying disc hernias. According to the current study, an essential difference exists between the segmental type and the continuous or mixed types. In addition, the current result seems to indicate that, at least in the segmental type, disc herniation is not the promoting or initiating factor of ossification of the posterior longitudinal ligament, but that, in these cases, the fragility of the posterior longitudinal ligament may increase the chance of a disc hernia.