Describe retrolisthesis.

Retrolisthesis: Definition and Clinical Significance

Retrolisthesis is a posterior displacement of one vertebra relative to the adjacent vertebra below, defined as posterior subluxation of 8% or more on lateral radiographs. 1, 2

Anatomical and Biomechanical Characteristics

Location and Distribution:

• Retrolisthesis predominantly manifests at L3 in the lumbar spine, though the location can be affected by the presence of simultaneous anterolisthesis at other levels 1
• In patients with high pelvic incidence (PI), retrolisthesis occurs approximately two vertebrae higher with a larger backward slope compared to patients with low PI 3
• The condition is relatively rare, with a prevalence of approximately 23.2% in patients with L5-S1 disc herniation 2

Biomechanical Mechanisms:

The developmental mechanism differs fundamentally based on pelvic incidence:

• Low PI retrolisthesis: Acts as a compensatory mechanism to move the gravity axis posteriorly in response to sagittal imbalance, characterized by relatively lower pelvic incidence, pelvic tilt, and lumbar lordosis 1
• High PI retrolisthesis: Primarily associated with increased backward sliding forces at hypertilted vertebrae in large thoracolumbar kyphosis (TLK) segments, combined with lumbar instability from disc degeneration and facet arthritis 3
• Overall lordosis and endplate inclination are considerably reduced in retrolisthesis, especially compared to anterolisthesis 4

Radiographic Features

Key Imaging Findings:

• Facet joint orientation in retrolisthesis segments is not different from segments without shifts, whereas degenerative spondylolisthesis shows more sagittally oriented facets 4
• Disc height is reduced compared to normal segments but comparable to degenerative spondylolisthesis 4
• 91.4% of patients with retrolisthesis under high PI demonstrate type 4 sagittal construction per Roussouly classification, while 92.6% with low PI show type 1 construction 3
• TLK is an independent predictor of retrolisthesis development under high-grade PI 3

Clinical Associations

Degenerative Changes:

• Retrolisthesis is commonly observed in patients with degenerative spinal problems and is associated with increased back pain and impaired function 1, 2
• Patients with retrolisthesis under high PI demonstrate significantly greater TLK, PI, sacral slope, sagittal vertical axis, T1 pelvic angle, and more severe disc degeneration and facet arthritis compared to controls 3
• The presence of retrolisthesis is not associated with increased incidence of degenerative disc disease, posterior degenerative changes, or vertebral endplate changes beyond what would be expected 2

Preoperative Assessment:

• In patients with L5-S1 disc herniation, retrolisthesis alone does not correlate with worse baseline pain or physical function preoperatively 2
• The contribution of pain or dysfunction related to retrolisthesis may be overshadowed by symptoms from concomitant disc herniation 2

Postoperative Outcomes:

• Patients with retrolisthesis who undergo L5-S1 discectomy demonstrate significantly worse bodily pain and physical function scores over 4 years postoperatively, though no significant differences exist in Oswestry Disability Index or Sciatica Bothersomeness Index 5
• Retrolisthesis does not affect operative time, blood loss, length of stay, complications, rate of additional spine surgeries, or recurrent disc herniations 5
• The contribution of pain related to retrolisthesis may become more evident after removal of the disc herniation 5

Clinical Pitfalls

Critical considerations when evaluating retrolisthesis:

• Do not assume retrolisthesis has the same clinical implications as anterolisthesis—they represent distinct biomechanical entities with different developmental mechanisms 1, 4
• Assess pelvic incidence and sagittal balance parameters, as these determine the type and location of retrolisthesis 1, 3
• In patients with concomitant disc herniation, retrolisthesis may not contribute significantly to preoperative symptoms but can affect long-term postoperative outcomes 5, 2
• Evaluate for associated degenerative changes including disc degeneration, facet arthritis, and thoracolumbar kyphosis, particularly in high PI patients 3