Thoracolumbar Spine Anatomy and Pathology - Root Canal

L4 L5 Neuroforamen (Root Canal)

The same specimen as in SLIDE 16, this section is through the L4–L5 neuroforamen (root canal) and illustrates the five components that contribute to the extremely severe "pin–hole stenosis" of the foramina in this specimen. The almost complete loss of intervertebral disc height causes the pedicle of L4 to "fall down" on the root like a guillotine, thereby also kinking it ("up–down–stenosis"). Normally the roots take a curved path around the pedicles above and below. The second component is a "front–back–stenosis" that is caused by the slight retrolisthesis of L4 on L5 induced by the obliquity of the facet joint in the sagittal plane. In addition, there are three components of "mass–effect":

1. The superior articular process of L5 intrudes into the neuroforamen from below like a wedge.

2. The outermost annulus fibrosus is partially ossified and extruded and completely obliterates the lower portion of the foramen.

3. The ligamentum flavum is redundant and thickened and also exerts a mass effect on the root against the unyielding pedicle. Note also the sclerosis adjacent to the endplates and the engorgement of the retrovertebral epidural veinous plexus (see also section 8 and 20).

©2000 Wolfgang Rauschning, M.D., Ph.D.
Professor of Clinical Anatomy
Academic University Hospital
Department of Orthopaedic Surgery
Uppsala, Sweden
Reproduction without permission is prohibited
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Updated on: 11/01/16