Quantitative three-dimensional anatomy of the subaxial cervical spine: implication for anterior spinal surgery

Knowledge of the quantitative anatomy of the subaxial cervical vertebrae is essential to safely perform anterior cervical surgery and to ensure adequate decompression of neural structures. In spite of this, little has been published in the neurosurgical literature regarding the spatial relationship of the lower cervical vertebrae and the implications of this anatomy for anterior cervical surgery. We report the three-dimensional analysis of the mid- and lower cervical spine in 10 cadaver specimens for 50 disarticulated vertebrae and discuss the relevance of this analysis to surgery in this region. Measurements were made using real-time video analysis of images transferred from a Zeiss microscope equipped with an image splitter and a Sony charge-coupled device camera. Images were then transferred to an IBM personal computer-based image analysis system. Analysis of variance was used to test for significant differences among the C3-C7 vertebral measurements. Important relationships of the vertebral artery to the anteroposterior diameter of the vertebral bodies and its variations from C3 to C7 are discussed. The vertebral artery migrates posteriorly to anteriorly from C3 to C6 and posteriorly again at C7; the implications of these variations are discussed for decompression of the neural foramen. Another finding showing that the inter-Luschka distance increases from C3 to C7 is important for adequate lateral decompression in anterior cervical spinal surgery. The pedicle to the Luschka joint was measured at the different levels; the pedicle is lateral to the Luschka joint from C3 to C6 and medial to the joint at C7. This variation explains the lack of root decompression at some cervical levels, even when decompression extends to the Luschka joint bilaterally. We also report the measurements of the vertebral bodies and the spinal canal and compare the results with other published data. We think these measurements provide guidelines for operating on the anterior cervical spine, facilitate adequate decompression of the spinal cord and neural foramen, and increase the margin of safety of the surgeon.