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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.
Retrolisthesis can be classified as a form of spondylolisthesis, since spondylolisthesis is often defined in the literature as displacement in any direction. [1] [2] Yet, medical dictionaries usually define spondylolisthesis specifically as the forward or anterior displacement of a vertebra over the vertebra inferior to it (or the sacrum).
The majority of disc herniations occur in the lumbar spine (95% at L4–L5 or L5–S1). [21] The second most common site is the cervical region (C5–C6, C6–C7). The thoracic region accounts for only 1–2% of cases.
The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the anatomy of humans and quadrupeds, such as horses, pigs, or cattle.
Forward displacement of a proximal vertebra in relation to its adjacent vertebra in association with an intact neural arch, and in the presence of degenerative changes, is known as degenerative spondylolisthesis, [9] [10] which narrows the spinal canal, and symptoms of spinal stenosis are common. Of these, neural claudication is most common.
In sacralization, the L5-S1 intervertebral disc may be thin and narrow. This abnormality is found by X-ray. [citation needed] Sacralization of L6 means L6 attaches to S1 via a rudimentary joint. This L6-S1 joint creates additional motion, increasing the potential for motion-related stress and lower back pain/conditions.
Injuries can be cervical 1–8 (C1–C8), thoracic 1–12 (T1–T12), lumbar 1–5 (L1–L5), [9] or sacral (S1–S5). [10] A person's level of injury is defined as the lowest level of full sensation and function. [ 11 ]
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 ...