44 Facet Block
Placement
Anatomy
The 33 vertebrae that make up the spinal column are linked by intervertebral disks and longitudinal ligaments anteriorly and through facet joints posteriorly. The posterior facet joints allow flexion, extension, and rotation of the vertebral column while providing a means for the axial nerves to exit the vertebral column on their way to becoming peripheral nerves. The facet joints are synovial joints formed by the inferior articular processes of one vertebra and the superior articular processes of the adjacent caudad vertebra. These articular processes are projections, two superior and two inferior, from the junction of the pedicles and the laminae. In the cervical and lumbar portions of the vertebral column, the facet joints are posterior to the transverse processes, whereas in the thoracic region the facet joints are anterior to the transverse processes (Fig. 44-1). In the cervical vertebrae, the joint surfaces are midway between a coronal and an axial plane, whereas in the lumbar region, the joints (at least the posterior portion) assume an orientation approximately 30 degrees oblique to the sagittal plane (Fig. 44-2).
