Sagittal section through a moderately
degenerated lower lumbar spine of a 77–year–old man who had a
history of intermittent claudication. This section is carried
through the lateral recesses of L4–L5 and L5–S1. The L4–L5 disc is
grossly disrupted and protrudes both anteriorly (underneath the
anterior longitudinal ligament) and posteriorly into the lateral
recess, abutting the markedly thickened and infolding ligamentum
flavum, thereby completely blocking the epidural veins which are
engorged both above and below this obstruction level. The L5–S1 disc
is completely resorbed with total loss of disc height. Focal
endplate sclerosis and erosions of the endplates are obvious. A
(probably still contained) disc herniation tracks inferiorly and
reaches the ligamentum flavum, again obstructing the epidural veins
at this level. This two–level spinal canal obstruction is thought to
cause a more pronounced vascular congestion because the segmental
drainage is blocked. The L4, L5 and S1 roots are not compressed.
Anteriorly, the iliac artery (red) and iliac vein (black) snugly
follow the spine, illustrating that an anterior annulus violation
during spinal instrumentation could cause severe vascular injury.
©2000 Wolfgang Rauschning, M.D., Ph.D.
Professor of Clinical Anatomy
Department of Orthopaedic Surgery
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