Fig. 27

Spinal canal. (a) Normal spinal canal. The central portion of the spinal canal is bordered laterally by a lateral recess, dorsally by a vertebral arch and ventrally by a vertebral body and discs. The lateral recess is bordered laterally by a pedicle, dorsally by a superior articular facet and ventrally by a vertebral body and discs. The foraminal space is bordered by cephalad and caudal pedicles and facet joints dorsally and a vertebral body and discs ventrally. The extraforaminal space is lateral to the neuroforamen. (b) Spinal canal stenosis. There are four major causes of degenerative spinal canal stenosis: disc herniation, hypertrophic facet joint osteoarthrosis, ligamentum flavum hypertrophy and degenerative spondylolisthesis