Anatomical Evaluation of the Lateral Hinge in Cervical Laminoplasty

Study Design : Observational study with retrospective computerized tomography (CT) analysis and clinical study. Objective : The purpose of this study was to examine the microanatomy of the lamina-facet junction and define the optimal position of the lateral gutter in cervical laminoplasty. Materials and Methods : Sixty patients who underwent cervical laminoplasty were retrospectively studied using CT images. To examine the anatomical features of the lamina-facet junction, the distance between pedicles, frequency of the presence of valley of lamina (VOL), and the distance between VOL were measured. In addition, to investigate the relationship between damage to the lamina and position of the lateral gutter, we set up the inner surface of pedicles with a medial pedicular line (MPL), and then measured the distance from the MPL to the lateral gutter and the frequency of damage to the inner cortex. Result : The distance between pedicles was maximal in C5. High frequencies of VOL were found in C4, 5, 6, and 7. However, differences between the width of pedicles and VOL were larger in the lower cervical spine, indicating that in the lower cervical spine, VOL might not be suitable as a surgical landmark for making the lateral gutter. It was revealed that the displacement of the lateral gutter toward the medial side increased the risk of damage to the inner cortex. Conclusion : Inadequate position of the lateral gutter causes insufficient decompression of the spinal canal in cervical laminoplasty. In this study, we revealed that the optimal position of the lateral gutter is on the MPL.