Spondylolisthesis of the axis vertebra

Abstract

The second cervical vertebra, or axis, is readily distinguished from all others by a toothlike projection from the upper end of the body, the dens (fig. 1 ). Anteriorly the dens has a facet for articulation with the corresponding facet on the innermost surface of the anterior arch of the atlas. Posteriorly the neck of the dens is grooved by the transverse ligament of the atlas. The pedicles of the axis are broad and strong, and are partially covered by the superior articular surfaces. Strong thick laminae fuse posteriorly with a broad, short, bifid spinous process. Each transverse process ends in a single tubercle and is pierced by a transverse foramen which faces superolaterally. The large, oval, slightly convex superior anticular surfaces of the axis are directed superolaterally. Each extends laterally from the vertebral body and pedicle. The inferior articular process, which has an anticular facet, is similar to those of the “typical” cervical vertebrae. The axis does not have an articular pillar or a lateral mass 118, 191. The pars interarticulanis is defined by Hollingshead 1191 in the lumbar region as the “region between the superior articular process and the rest of the lamina ’ He defines