Abstract
BACKGROUND: The lumbar spine includes 5 lumbar vertebral bodies, L1, L2, L3, L4, and L5. At each level, there is a disc space defined by the two bones (vertebral bodies) in the back; for example, there is a disc space at the L5-S1 level etc. The normal front to back (anterior to posterior or AP diameter) measurement of the spinal canal is typically 18-20 mm, but some patients have narrowing called spinal stenosis. METHODS: Lumbar stenosis is defined by two major types. Central stenosis compresses the midline (in the middle) sac of nerve tissue (dural or thecal sac containing the lumbar nerve roots). Lateral recess stenosis (off to the sides) compresses the individual exiting nerve roots. RESULTS: At each lumbar level, there may be compression of the nerve tissue centrally (dura also called cauda equina) or the nerve roots (on one or both sides). Compression may occur due to soft or calcified discs in the front (anteriorly) of the spine at different levels or from behind (posteriorly) due to arthritic enlargement (hypertrophy) or calcification (ossification) of the yellow ligament, facet joints, and/or bones (laminae). Surgery to remove bone and arthritic structures from the back of the spinal canal to decompress nerve tissue is called a laminectomy. CONCLUSIONS: Patients with narrowing of the lumbar spinal canal may have central or lateral recess stenosis that compresses the thecal sac and/or exiting nerve roots at any of 5 levels. Laminectomy, performed at single or multiple levels, decompresses lumbar spinal stenosis.