[A radiographic study of the progression of ossification of the cervical posterior longitudinal ligament: the correlation between the ossification of the posterior longitudinal ligament and that of the anterior longitudinal ligament].

Progression of ossification of the posterior longitudinal ligament (OPLL) was evaluated in relation to that of ossification of the anterior longitudinal ligament (OALL). The subjects of this study were 68 patients with OPLL in the cervical spine. 47 of them underwent conservative treatment, and the remaining 21 underwent decompression surgery of the cervical spine (involving 11 cases of laminectomy and 10 of an enlargements of the spinal canal). All 68 patients were followed up for more than 5 years. Most of the continuous and most of the mixed types of OPLL exhibited advancement of the stage at the final examination, and showed much progression of OALL during the follow-up period. The progression of OALL tended to be more advanced in those cases in which the progression of OPLL was advanced. In most of the operated cases, OPLL was highly progressed after surgery in both the longitudinal direction and in the thickness, regardless of the ossification type. There was also evidence of progression of OALL in these patients, at each level of the cervical spine, with particularly advanced progression at the lower levels with a higher rate than in the conservative cases. These results indicate that the progressions of OPLL and OALL are closely correlated, and that the same precipitating factors may therefore be involved in both OPLL and OALL. A marked progression of the ossification after surgery suggested that local factors of the cervical spine played an important role in the progression.