Ossification of the Posterior Longitudinal Ligament in Not Only the Cervical Spine, but Also Other Spinal Regions

Abstract

A prospective cohort study. To evaluate ossification of the posterior longitudinal ligament (OPLL) of the whole spine in patients with cervical OPLL and to analyze which types of cervical OPLL were associated with the other lesions in the thoracic and/or lumbar spine. OPLL is most frequently seen in the cervical spine. The coexisting ossified lesions are sometimes observed in other spinal regions. However, coexisting OPLL in other spinal regions have not yet been precisely evaluated in patients with cervical OPLL. One hundred seventy-eight patients with a diagnosis of cervical OPLL whose plain radiographs were obtained were included. Computed tomographic images of the whole spine were obtained. The ossification index (OS index) was newly determined according to the sum of the levels of vertebral bodies and intervertebral discs with OPLL. The patients were divided into 2 groups, the group that had OPLL only in the cervical spine (C group) and the group that had OPLL in multilevel spinal regions other than the cervical spine (M group). Ninety-five (53.4%) had OPLL not only in the cervical spine, but also in other spinal regions. The M group had more females than the C group. The incidence of bridge formation in the cervical spine was higher in M group than in C group. More females had a high OS index. A positive correlation was found between the OS index of the cervical spine and the OS index of the thoracic and lumbar spine; however, the r value was small. This study demonstrated that more than half of the patients with cervical OPLL had coexisting OPLL in the thoracic and/or lumbar spine. We strongly recommend computed tomographic analysis of the whole spine for patients with radiographical evidence of OPLL in the cervical spine for the early detection of additional sites of ossification.