Anatomy of the lumbar radicular canal.

The radicular canal is defined as the lateral part of the spinal canal containing the spinal nerve root from its point of emergence through the dural envelope up to and including the intervertebral foramen. The radicular canal, resembling a hollow hemicylinder opened towards the midline, can be divided into three parts, i.e. retrodiscal, parapedicular (the lateral recess per se) and foraminal. The different walls of the canal (notably those of the lateral recess) are described. A review of the main types of roentgenographic exploration of the radicular canal are presented based on these anatomical findings. Finally, this static description of the typical lumbar radicular canal and its variations according to the lumbar or sacral level under consideration is followed by a presentation of the modifications which arise in the upright position and during extension and flexion of the lumbar spine.