Axial section through a vertebra at the
mid–pedicle level. The cancellous bone is coarse and strong. Venous
vascular channels traverse the vertebral body and transgress the
cortical bone posteriorly in the midline and anterolaterally on the
right side. At their anterior aspect the vertebra is braced by the
thick and wide anterior longitudinal ligament. By contrast, the
posterior longitudinal ligament is narrow and thin and always
attached to the dura. Behind the base of the transverse processes a
pointed bony spike, the accessory process, lies in the trajectory
along which screws typically are inserted into the pedicle. This may
explain difficulties during percutaneous insertion of pedicle screws
which tend to slide out of the "bulls–eye" image of the pedicle.
Posteriorly, the upper sharp margin of the lamina and of the spinous
process are visualized. The thecal sac is displayed at the level of
the axillary outpouchings of the dura which constitute the steeply
inferiorly directed offset of the root sleeves. Posteriorly the
thecal sac is bounded by the sublaminar veins. These dorsal internal
veins are far less voluminous than the ventral internal veins.
©2000 Wolfgang Rauschning, M.D., Ph.D.
Professor of Clinical Anatomy
Department of Orthopaedic Surgery
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