Retrolisthesis
Encyclopedia
A retrolisthesis is a posterior displacement of one vertebral body with respect to the adjacent vertebrae to a degree less than a luxation (dislocation). Clinically speaking, retrolisthesis is the opposite of spondylolisthesis
Spondylolisthesis
Spondylolisthesis describes the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. It was first described in 1782 by Belgian obstetrician, Dr. Herbinaux. He reported a bony prominence anterior to the sacrum that obstructed the vagina of a...

 (anterior displacement of one vertebral body on the subjacent vertebral body). In the past this clinical pathology was also called a "retrospondylolisthesis". (2) Retrolistheses are most easily diagnosed on lateral x-ray views of the spine. Views, where care has been taken to expose for a true lateral view without any rotation, offer the best diagnostic quality.

Retrolistheses are found most prominently in the cervical spine and lumbar
Lumbar
In tetrapod anatomy, lumbar is an adjective that means of or pertaining to the abdominal segment of the torso, between the diaphragm and the sacrum ...

 region but can also be seen in the thoracic area.

Classification

Complete Retrolisthesis - The body of one vertebra is posterior to both the vertebral body of the segment of the spine above as well as below.

Stairstepped Retrolisthesis - The body of one vertebra is posterior to the body of the spinal segment above, but is anterior to the one below.

Partial Retrolisthesis - The body of one vertebra is posterior to the body of the spinal segment either above or below. (3)

Grading

Since the vertebral body in a retrolisthesis moves in a posterior direction, the grading used for spondylolistheses is of little use. It is however useful to divide the anterior to posterior dimension of the intervertebral foramina
Intervertebral foramina
When the spinal vertebrae are articulated with each other the bodies form a strong pillar for the support of the head and trunk, and the vertebral foramina constitute a canal for the protection of the medulla spinalis...

 (IVF) (4) into four equal units. A posterior displacement of up to ¼ of the IVF is graded as Grade 1, ¼ to ½ as Grade 2, ½ to ¾ as Grade 3, ¾ to total occlusion of the IVF as Grade 4. Alternatively, a measurement of the amount of displacement can also made by measuring the bone displacement in millimetres.

Retrolistheses are caused by injury and resulting instability of the connecting soft tissues especially ligaments, discs, muscles, tendons and fascia. They may also involve muscles through spasm as a result of nerve malfunction due to pressure caused by the posterior displacement of the vertebra encroaching on the contents of the IVF. The IVF's contents include spinal (sensory and motor) nerves, arteries, veins and lymphatic vessels which cater to the nutritional and waste removal needs of the spinal cord.

Degenerative spinal changes are often seen at the levels where a retrolisthesis is found. These changes are more pronounced as time progresses after injury and are evidenced by end plate osteophytosis, disc damage, disc narrowing, desiccation
Desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

 and disc bulging. “A retrolisthesis hyperloads at least one disc and puts shearing forces of the anterior longtitudinal ligament, the annular rings, nucleus pulposus
Nucleus pulposus
Nucleus pulposus is the jelly-like substance in the middle of the spinal disc. It is the remnant of the notochord . It functions to distribute hydraulic pressure in all directions within each disc under compressive loads. The nucleus pulposus consists of chondrocyte-like cells, collagen fibrils,...

, cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...

 end plates and capsular ligaments. The bulging, twisting and straining tissues attached to the endplates
Endplates
In anatomy, endplates are the parts of the vertebra that come in direct contact with the intervertebral disc to form an article . Each vertebra has two endplates: a superior and an inferior....

 pull, push and stretch it. It is worsened with time, becoming irreversible.” This is the etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....

 of degenerative joint disease. (5)

Associated radiological findings include a vacuum phenomenon (in the nucleus pulposis of the adjacent intervertebral disc), reduction of disc height with corresponding loss of the disc space, marginal sclerosis of the adjacent vertebral bodies, osteophyte formation and apophyseal joint instability. With a retrolisthesis there is always a less than ideal positioning of spinal segments. There is also always a reduced anterior to posterior dimension of the spinal canal compared to the way it is supposed to be. The greater the posterior displacement, the more significant it is for producing a dysfunctional spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...

 or even a cauda equina syndrome
Cauda equina syndrome
Cauda equina syndrome ' is a serious neurologic condition in which there is acute loss of function of the lumbar plexus, neurologic elements of the spinal canal below the termination of the spinal cord.-Causes:...

.

Joint stability

Joint stability is easily evaluated by the use of flexion
Flexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...

 and extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...

 lateral x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

 views of the spine.
A summary of part of the DRE tables (6) give a guide as to the implications of the joint instability. If either translation or angular change is determined from flexion to extension to the degree shown in the table below, then Category IV instability is present. This would mean that 20% to 23% “whole person impairment” is present at each level where this if found. In calculating the total whole person impairment it is NOT merely the case of adding the percentages. This calculation is best left to your health care provider. See also Joint stability
Joint stability
Joint stability refers to the resistance offered by various musculoskeletal tissues that surround a skeletal joint. Several subsystems ensure the stability of a joint. These are the passive, active and neural subsystems. The opposite of stability is instability...

.

Translation is a gliding motion where one bone of a joint glides over its neighbour.

Symptoms

Retrolisthesis may lead to symptoms of greatly varying intensity and distribution. This is because of the variable nature of the impact on nerve tissue and of the mechanical impact on the spinal joints themselves.

Structural instability may be experienced as a local uneasiness through to a more far reaching structural compensatory distortion involving the whole spine. If the joints are stuck in a retrolisthesis configuration there may also be changes to range of motion.

Pain may be experienced as a result of irritation to the sensory nerve roots by bone depending on the degree of displacement and the presence of any rotatory positioning of the individual spinal motion segments. The soft tissue of the disc is often caused to bulge in retrolistheses. 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. Fourteen patients (47%) without retrolisthesis (control group) did not show any retrolisthesis and the CT did not show any bulge/protrusion. On categorizing x-ray and CT pathology as being present or not, the well positioned ie. true lateral plain x-ray film revealed a sensitivity and specificity of 100% ([95% Confidence Interval. = [89%–100%]) for bulge/protrusion in this preliminary study.” (7)

Spinal cord compressions are also possible with patients experiencing pain, rigidity and neurologic signs that may follow some distance along nerves to cause symptoms at some distance from the location of the retrolisthesis. PARDC
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