In this video we're going to discuss about the osteology of lumbar vertebrae. The lumbar vertebrae consists of the same elements as the thoracic vertebrae, but are more massive as they are weight-bearing vertebrae. And there are five lumbar vertebrae out of which the first four are typical while the fifth is atypical.
Features of the lumbar vertebrae. They have massive, reniform or kidney-shaped bodies. The absence of foramina transversaria in the transverse processes is appreciated. Absence of costal facets in the body, presence of accessory and mammillary processes, and thick quadrilateral spinous processes are appreciated. Features The body of the vertebra Transverse diameter is more than the anterior-posterior diameter.
The size of the body increases progressively from the first to the fifth lumbar vertebrae. and the body is massive and reny form. It is triangular in shape. It is larger than in the thoracic vertebrae but smaller than in the cervical vertebrae. Vertebral arch The vertebral arch is made up of pedicles, laminae, spine, transverse processes, superior and inferior articulating processes.
The pedicles are short and strong processes. They project backwards from the upper parts of the body, and as a result, the inferior vertebral notches are much deeper than the superior ones. The laminae are short, thick, and broad plates, and they are directed posterior medially. The overlapping between the laminae of the adjoining vertebrae is minimal.
The spine. The spine is quadrilateral in shape and it projects backwards. The transverse processes. The transverse processes are thin and tapering and are homologous to the ribs in the thoracic region.
The posterior inferior aspect of each transverse process presents a small, rough elevation called accessory process. This presents the true transverse process of the vertebra. Superior Articular Processes The facets on the superior articular processes are concave, which project backward and medially.
The superior articular processes lay farther apart from the inferior articular processes. Their posterior borders are marked by a rough elevation called mammillary process. Inferior Articular Process The inferior articular processes lie nearer to each other than the superior articular processes.
They bear convex articular facets which face forwards and laterally. Features of the atypical fifth lumbar vertebra. The fifth lumbar vertebra presents the following atypical features. The transverse processes are thick, short, and pyramidal in shape. Their base is attached to the whole thickness of the pedicle and encroaches on the side of the body.
They seem to be turned upwards. The spine is small, short, least substantial and rounded at the tip. The body is largest of all the lumbar vertebrae.
The vertical height of the anterior surface of the body is more than that of the posterior surface. This difference is responsible for a sharp or prominent lumbosacral angle of about 120 degrees. Superior articular facets look more backwards than medially and the inferior articular facets look more forwards than laterally as compared to the typicals.
The distance between the inferior articular processes is equal or more than that of the superior articular processes. End of the fifth lumbar vertebra. It is a fusion of the 5th lumbar vertebra with the sacrum.
The fusion may be complete or incomplete. The transverse process of L5 may articulate with the ala of the sacrum and or the ilium and compress the L5 spinal nerve. This condition occurs in about 5% of normal individuals.
Spondylolisis. In this condition, there is a separation of the body of the 5th lumbar vertebra from the vertebral arch bearing inferior articular process on one side only, normally interlocked with the articular processes of the sacrum. Spondylolistesis. It is the forward slipping of the fifth lumbar vertebra over the sacrum.
Sometimes, the inferior articular processes, laminae, and the spine of the L5 vertebra are separated from the rest of the vertebra, which slip forward on the sloping superior surface of the sacrum. This condition may clinically present as backache and pain radiating along the course of the sciatic nerve causing sciatica.