Thoracolumbar Spine Anatomy and Pathology - Lower Lumbar, Upper Sacrum
Lower Lumbar Spine Upper Sacrum of a Young Female
Sagittal section through a normal lower lumbar spine and upper sacrum of a young female through the lateral portion of the thecal sac. The segmental root bundles converge towards each intervertebral foramen. The L3, L4, and L5 discs all display a slight posterior convexity and the outermost layers of the annulus fibrosus attach beyond the apophyseal ring. The vertebral bodies typically have a concave posterior contour. In the midportion of the posterior vertebral wall a large venous vascular foramen (outlet foramen of the Batson plexus) at L5 through which the ventral internal venous plexus communicates with the veins traversing the vertebral bodies. The laminae have a characteristic shape: toward the spinal canal only a narrow vertical band of cortical bone is exposed, superiorly the laminae have a sharp ridge whereas the ligamentum flavum attaches to its inferior, posteriorly receding surface. At the infrajacent lamina the ligamentum flavum attaches to the sharp upper ridge and a small area behind it. Note that the ligamentum flavum at the lumbosacral level is much thinner than at the levels above.
©2000 Wolfgang Rauschning, M.D., Ph.D.
Professor of Clinical Anatomy
Academic University Hospital
Department of Orthopaedic Surgery
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