What is grade 1 retrolisthesis?

What is Grade 1 Retrolisthesis?

Grade 1 retrolisthesis is a mild backward displacement of one vertebra relative to the vertebra below it, defined as 20–25% posterior subluxation (or ≥8% in some classification systems), representing the mildest form of vertebral slippage that often overlaps with normal anatomical variation and typically carries minimal clinical significance when occurring as an isolated finding. 1

Definition and Classification

• Grade 1 retrolisthesis represents 20–25% reduction in vertebral alignment, which is the mildest category in the semiquantitative grading system used for vertebral body deformities 1
• Some classification systems define retrolisthesis as posterior subluxation of ≥8% of the vertebral body width 2
• Grade 1 fractures have greater overlap with nonfracture deformities compared to higher grades, making isolated grade 1 findings less clinically predictive 1

Clinical Significance

• A solitary, asymptomatic grade 1 retrolisthesis is likely to be of minimal to no clinical significance, whereas grade 2 (26–40% reduction) and grade 3 (>40% reduction) are more predictive of future complications 1
• The presence of retrolisthesis at L5-S1 in patients with disc herniation has a prevalence of 23.2% but was not associated with increased preoperative low back pain or physical dysfunction in surgical candidates 2
• Retrolisthesis can serve as a compensatory mechanism for sagittal balance, particularly in patients with low pelvic incidence and thoracolumbar kyphosis 3

Associated Radiographic Features

• Retrolisthesis under low pelvic incidence typically shows type 1 sagittal construction (92.6% of cases), while retrolisthesis under high pelvic incidence shows type 4 construction (91.4% of cases) 4
• Patients with retrolisthesis demonstrate significantly lower sagittal vertical axis, pelvic incidence, sacral slope, and lumbar lordosis compared to those with anterolisthesis 3
• The average Pfirrmann disc degeneration score at levels with retrolisthesis is 2.11, indicating discs are not severely degenerated and suggesting instability rather than advanced degeneration as the primary mechanism 3

Management Approach for Mild Retrolisthesis

Conservative management with flexion-based exercises is the primary treatment approach for mild retrolisthesis without significant instability or neurological symptoms, with surgical intervention reserved only for cases with documented instability on dynamic imaging or failed comprehensive conservative therapy lasting at least 3–6 months. 5

Initial Conservative Treatment

• Formal physical therapy for at least 6 weeks is required before escalating treatment, with multimodal chiropractic care including cervical manipulation, axial distraction, and isometric stretching showing effectiveness in case reports 5, 6
• Conservative therapy should be attempted for a minimum of 3–6 months before considering any surgical options 5
• Evaluate response at 6 weeks to determine if escalation to interventional procedures is needed 5

Surgical Indications (Rarely Applicable to Grade 1)

• Documented instability on flexion-extension radiographs with movement at the affected level is a requirement for surgical consideration, as movement on dynamic films changes management from conservative to surgical 5
• Decompression with fusion is superior to decompression alone when retrolisthesis is associated with documented instability, with 96% reporting excellent/good results versus 44% with decompression alone 5

Critical Management Pitfalls

• Do not perform fusion for mild retrolisthesis without documented instability on dynamic imaging, as this represents overtreatment with increased complications and costs without proven benefit 5
• Failure to complete formal physical therapy for at least 6 weeks is a critical deficiency that precludes surgical consideration 5
• Not correlating imaging findings with clinical symptoms represents a common diagnostic error, as disc abnormalities are common in asymptomatic patients 7

Adjacent Level Considerations

• 29% of patients with L5-S1 spondylolytic spondylolisthesis develop retrolisthesis at L4-5, with slip angle and L4-5 disc degeneration being consistent findings in these cases 8
• Progressive nerve root compression is the most clinically significant complication when retrolisthesis advances, manifesting as radiculopathy with dermatomal pain distribution 7