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ABSTRACT
Reviewing the literature on the vascular anatomy of the
spinal epidural space, it appeared that the knowledge of the internal
vertebral venous plexus is limited. Injection studies of the entire internal
vertebral venous plexus after application of modern techniques, to the
best of our knowledge, have never been performed. Based on the clinical
importance of these structures, it was decided to study the human
vertebral venous system after Araldite CY 221 injection, in order to update
the morphological characteristics of the internal vertebral venous system.
The vertebral venous systems of ten fresh human cadavers, between 64
and 93 years of age, were injected with Araldite CY 221 mixture. All
cadavers were dissected and the posterior and anterior internal vertebral
venous plexuses were studied in detail.

The anterior part of the internal vertebral venous plexus is fairly
constant. On the contrary, the posterior internal vertebral venous plexus
showed a striking segmental and interindividual variability. In the thoracic
area, two types of traversing veins are observed. Both types show a
somewhat symmetrical ‘‘inversed V’’ configuration. No anatomical valves
were observed. Nevertheless, anterograde flushing (via the femoral veins)
of the vertebral venous system appeared to proceed much faster than
retrograde flushing (via the superior vena cava).

The classical picture of the internal vertebral venous plexus appears a
simplification of the actual situation. Especially in the posterior part,
segmental and interindividual differences are prominent. The preferential
direction of the flow during flushing suggests the presence of functional
valves, which are probably located in the thoracic part of the
posterior internal vertebral venous plexus, resulting from the typical
shape of the veins in this area. This might explain the difficulties with
imaging of the posterior part of the internal vertebral venous plexus in
vitro as well as in vivo. Further study is needed to determine whether the
configuration of the posterior internal vertebral venous plexus in younger
individuals is different, compared with the presently studied aged subjects.

We did not
find anatomical valves in the vertebral venous system,
except the tricuspic valves encountered in both vertebral
veins of cadaver no. 554.