Analysis of the cervical spine alignment following laminoplasty and laminectomy.

Very little detailed biomechanical examination of the alignment of the cervical spine following laminoplasty has been reported. We performed a comparative study regarding the buckling-type alignment that follows laminoplasty and laminectomy to know the mechanical changes in the alignment of the cervical spine. Lateral images of plain roentgenograms of the cervical spine were put into a computer and examined using a program we developed for analysis of the buckling-type alignment. Sixty-four patients who underwent laminoplasty and 37 patients who underwent laminectomy were reviewed retrospectively. The subjects comprised patients with cervical spondylotic myelopathy (CSM) and those with ossification of the posterior longitudinal ligament (OPLL). The postoperative observation period was 6 years and 7 months on average after laminectomy, and 5 years and 6 months on average following laminoplasty. Development of the buckling-type alignment was found in 33% of patients following laminectomy and only 6% after laminoplasty. Development of buckling-type alignment following laminoplasty appeared markedly less than following laminectomy in both CSM and OPLL patients. These results favor laminoplasty over laminectomy from the aspect of mechanics.