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Spondylolisthesis is when one spinal vertebra slips out of place compared to another. [1] While some medical dictionaries define spondylolisthesis specifically as the forward or anterior displacement of a vertebra over the vertebra inferior to it (or the sacrum), [2] [3] it is often defined in medical textbooks as displacement in any direction.
The fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis. [3] Most individuals have five lumbar vertebrae, while some have four or six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals.
These cannot be determined by plain films, as the x-ray passes through the soft tissue. A study by Giles et al., stated that sixteen of the thirty patients (53%) had retrolisthesis of L5 on S1 ranging from 2–9 mm; these patients had either intervertebral disc bulging or protrusion on CT examination ranging from 3–7 mm into the spinal canal.
In most cases this occurs in the lowest of the lumbar vertebrae (L5), but may also occur in the other lumbar vertebrae, as well as in the thoracic vertebrae. Spinal disc herniation , more commonly called a slipped disc , is the result of a tear in the outer ring ( anulus fibrosus ) of the intervertebral disc , which lets some of the soft gel ...
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
On an anterior oblique radiograph of the lumbar spine, the pars is the neck of the imaginary Scottie dog; the Scottie dog's eye is the pedicle, [3] its hindlegs the spinous process, its nose the transverse process, its ear the superior articular facet and its forelegs the inferior articular facet.
Looking directly at the front or back of the body, the 33 vertebrae in the spinal column should appear completely vertical. From a side view, the cervical (neck) region of the spine (C1–C7) is bent inward, the thoracic (upper back) region (T1–T12) bends outward, and the lumbar (lower back) region (L1–L5) bends inward.
Bertolotti's syndrome is characterized by sacralization of the lowest lumbar vertebral body and lumbarization of the uppermost sacral segment. It involves a total or partial unilateral or bilateral fusion of the transverse process of the lowest lumbar vertebra to the sacrum, leading to the formation of a transitional 5th lumbar vertebra.