Dynamic changes in the spinal cord cross-sectional area in patients with myelopathy due to cervical ossification of posterior longitudinal ligament

Background contextDynamic changes in the spinal cord cross-sectional area due to cervical ossification of the posterior longitudinal ligament (C-OPLL) are unknown, but dynamic multidetector-row computed tomography (MDCT) may be a useful tool.PurposeThe purpose of this study was to evaluate the influence of dynamic factors on the spinal cord in patients with C-OPLL using MDCT during flexion and extension after myelography.Study design/settingThis was a prospective cohort study.Patient sampleParticipants included 107 prospectively enrolled consecutive patients with C-OPLL and myelopathy.Outcome measureThe outcome measure was the extension/flexion ratio at the spinal cord cross-sectional area at the most stenotic cervical level (SCASL).MethodsDynamic MDCT was performed, and the SCASL was measured. Patients were divided into the kyphosis group or lordosis group according to C2–C7 alignment. They were divided further into the K-line (−) group or K-line (+) group. The Japanese Orthopedic Association (JOA) score was used to determine myelopathy severity.ResultsAll patients with C-OPLL had myelopathy, with a mean JOA score of 10.7 and mean disease duration of 16.7 months. The average extension/flexion ratio at all disc levels was less than 100%, suggesting that the spinal cord was compressed more during extension. In the kyphosis group, the spinal cord was compressed slightly more during flexion than during extension. In the K-line (−) group, the spinal cord was compressed more during flexion, although C2–C7 alignment was slightly lordotic on average. Large changes in the spinal cord cross-sectional area during extension-flexion and disease duration significantly influenced the severity of myelopathy.ConclusionsDynamic MDCT was useful for evaluating dynamic changes in the spinal cord. At the most stenotic level, the spinal cord became narrower during extension at all disc levels. In the kyphosis group and K-line (−) group, it became narrower during flexion. Cervical flexion may induce greater spinal cord compression in patients with kyphosis and K-line (−).