They increase in sagittal width from 9 mm to up to 18 mm at L5. They increase in angulation in the axial plane from 10 degrees to 20 degrees by L5. The pedicle is sometimes used as a portal of entrance into the vertebral body for fixation with pedicle screws or for placement of bone cement as with kyphoplasty or vertebroplasty. The laminae are broad, short, and strong. They form the posterior portion of the vertebral arch. In the upper lumbar region the lamina are taller than wide but in the lower lumbar vertebra the lamina are wider than tall. The lamina connects the spinous process to the pedicles. The vertebral foramen within the arch is triangular, larger than the thoracic vertebrae, but smaller than in the cervical vertebrae. Processes
The spinous process is thick, broad, and somewhat quadrilateral; it projects backward and ends in a rough, uneven border, thickest below where it is occasionally notched.The superior and inferior articular processes are well-defined, projecting respectively upward and downward from the junctions of pedicles and laminae. The facets on the superior processes are concave, and look backward and medialward; those on the inferior are convex, and are directed forward and lateralward. The former are wider apart than the latter since in the articulated column, the inferior articular processes are embraced by the superior processes of the subjacent vertebra.The transverse processes are long and slender. They are horizontal in the upper three lumbar vertebrae and incline a little upward in the lower two.
Drug Information Portal. U.S. National Library of Medicine.