A retrolisthesis is a posterior displacement of one vertebral body with respect to the adjacent vertebrae to a degree less than a luxation (dislocation). Retrolisthesis is relatively rare but when present has been associated with increased back pain and impaired back function. Clinically speaking, retrolisthesis is the opposite of spondylolisthesis (anterior displacement of one vertebral body on the subjacent vertebral body). 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.
Retrolisthesis may occur more commonly than initially believed. However retrolisthesis (backwards slippage of one vertebral body on another) has historically been regarded as an incidental finding, one which doesn’t cause any symptoms, and is considered to be of little or no clinical significance. But there is a possible association between retrolisthesis and increased back pain and impaired back function.
Retrolisthesis may be present in up to 30% of extension radiographs of patients complaining of chronic low back pain. Retrolisthesis has been found to be associated with disc degeneration, decrease in lumbar lordosis, and decrease in vertebral endplate angle.
According to Shen et al (Shen M et al; Spine J. 2007; 7(4): 406–413) it is possible that the contribution of pain or dysfunction related to retrolisthesis was far overshadowed by the presence of symptoms due to the concomitant disc herniation.
Crucial questions in musculoskeletal medicine in retrolysthesis:
1. Do individuals with lumbar disc herniations have increased levels of back pain, back dysfunction, and decreased quality of life pre-operatively if they have concomitant retrolisthesis at the involved herniated disc level?
2. Does the presence of degenerative changes (disc degeneration, degenerative endplate changes, posterior element degenerative changes) along with retrolisthesis worsen the symptoms and / or possibly the prognosis in these operative cases?
Grading & 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.
Since the vertebral body in a retrolisthesis moves in a posterior direction, the grading used for spondylolistheses is of little use. Clinicians & researchers use the following grading systems after following X ray reading:
There are always 2 vertebrae involved in measuring the magnitude of a retrolisthesis for translation (slippage). The lower segment is considered the position of stability. The upper segment rests on it. The upper segment is considered the segment of mobility and is the one being determined for retrolisthesis.
1) A line is drawn along the top of the vertebral body of the lower spinal segment.
2) Then at the top-back most portion of the lower vertebral body, draw line at 90 degrees to line, till it projects well into the body of the vertebra above.
3) Then draw another line parallel to the line just drawn this time at the posterior most lower portion of the upper vertebral body.
4) The distance between the upright lines and is measured. Any distance of 3mm or greater is a retrolisthesis. This measurement represents the degree of translation (slippage) of the upper of the two segments.
1. Few clinicians follow the following criteria:
Percent subluxation can be calculated for any individual with greater than or equal to 3 mm of posterior displacement. A cut-off point of 3 mm has been used previously both in orthopaedic research and clinical practice. This 3mm cut-off corresponds to a slip of 8% which is used as the lower limit to define retrolisthesis.
2. Other few follow the following criteria:
In this grading system anterior to posterior dimension of the intervertebral foramina (IVF) is divided 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.
Joint stability & retrolisthesis:
Joint stability is easily evaluated by the use of flexion and extension lateral x-ray views of the spine. If vertebral translation present on standing (stressed by gravity) lateral view x-rays then it indicates that the spinal joints at those levels are already in a "significantly stressed" state. It further means that if this is the condition then there may be degree of soft tissue looseness at best and soft tissue tearing at worst otherwise a positional translation of this magnitude could not be present.
Implications of joint instability are derived from DRE (Diagnosis related estimates) tables. If translation of 4.5mm & angular change of 15 degree or more at L1, L2 or L 3, 20 degree or more at L4 and 25 degree or more at L5 is found 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.
Pathology & structures involved:
Retrolysthesis is caused in lumbar by flexion injury or by prolonged & continual use of lumber spine flexion over a period of time.
Spine instability causes damage to of the connecting soft tissues especially juxtaposed ligaments, discs, muscles, tendons and fascia. Muscle spasm may also be present. Nerve compression may be present at intervertebral foramen (IVF). The compression of 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 evidenced by end plate osteophytosis, disc damage, disc narrowing, tearing failure and eventually results in disc bulging.
“A retrolisthesis hyper loads at least one disc and puts shearing forces on the anterior longitudinal ligament, the annular rings, nucleus pulposis, cartilage end plates and capsular ligaments. The bulging, twisting and straining tissues attached to the endplates pull, push and stretch it. It is worsened with time, gradually
becoming irreversible. This is the aetiology of degenerative joint disease in retrolysthesis.
X-ray & radiological findings:
• Vacuum phenomenon (in the nucleus pulposis of the intervertebral disc below the retrolisthesis),
• Reduction of disc height with corresponding loss of the disc space,
• Marginal sclerosis (more dense due to stress) of the adjacent vertebral bodies,
• Osteophyte (spur) formation and
• Apophyseal (guiding) joint instability.
• With a retrolisthesis there is always a less than ideal positioning of spinal segments. (subluxation)
• There is also always a reduced anterior to posterior dimension of the spinal canal compared to the way it is supposed to be. This leads to nerve signal alteration.
• The greater the posterior displacement, the more significant it is for producing nerve root impingement and irritation, a dysfunctional spinal cord even to the point of a cauda equina compression syndrome if present in the lower lumbar spine.
Patient clinical presentation:
Patients present with varied S/S with retrolysthesis from little pain to severe disabling pain. Patient may also present with sciatica with or without neurological deficits. In patients with neural claudication lumbar canal stenosis due to lysthesis is also seen.
Both IV joints & facet joints may produce pain & radiation.
Maitland transverse glides/ lateral PA glides on to the side of pain can be administered in cases associated mostly with facet restrictions. Central PA is also administered in appropriate cases with mutifidus & other spinal exercises. LS belt in majority cases may aid relief from pain.
McKenzie’s exercises to stretch the anterior spinal structures both with mobilization & manipulation in McKenzie style along with home exercises in McKenzie is highly advisable.
Spine muscle atrophy is seen in many cases of long standing retrolythesis. Spine stabilization exercises are sought in most cases and appropriate home exercises must be advised with follow ups with the physiotherapist.
Electrotherapy is directed to reduce pain. Few clinicians also believe that modalities like SWD or MWD can reduce the rate of degeneration hence also used in degenerative retrolysthesis.