Fifth Lumbar Vertebra

Description

Dominating the lumbosacral junction, the fifth lumbar vertebra (L5) sits inferior to L4 and immediately superior to the sacral base, with the L5–S1 intervertebral disc interposed anteriorly. From the stout vertebral body, the pedicles and laminae form a posterior arch that encloses the vertebral foramen, while the spinous process projects posteriorly and the transverse processes extend laterally with a characteristically broad span. Superior and inferior articular processes frame the pars interarticularis on each side, and the inferior facets angle to meet the superior articular facets of S1, locking the segment against shear. L5 matters because it is the transition point where lumbar lordosis meets the fixed sacrum, so loads and motion concentrate at the L5–S1 level. This view clarifies why spondylolysis of the pars interarticularis commonly occurs here and how anterior translation in isthmic spondylolisthesis can narrow the neural foramina, irritating the exiting L5 nerve root. The wide transverse processes also orient you to regional landmarks used in posterior approaches and in interpreting oblique radiographs when assessing the classic “Scotty dog” sign. Faculty can drop this plate into gross anatomy and musculoskeletal teaching modules when introducing lumbar vertebral morphology, facet orientation, and the anatomy of the lumbosacral angle. It also suits spine surgery and radiology publications discussing L5–S1 degenerative disc disease, pars defects, and preoperative planning around the sacral promontory and foraminal exit zones. Anatomical accuracy verified by SciePro's Medical Advisory Board.