What is Grade 1 Retrolisthesis?
Grade 1 retrolisthesis is a posterior displacement of a vertebra relative to the vertebra below it, measuring 2-3 mm of backward slippage.
Definition and Classification
Retrolisthesis represents the backward (posterior) displacement of one vertebral body relative to the adjacent inferior vertebra, as opposed to anterolisthesis where the vertebra slips forward 1.
The grading system classifies the severity based on the degree of displacement:
This classification system applies to degenerative cervical spondylolisthesis and is used similarly for lumbar spine retrolisthesis 1.
Clinical Significance
Retrolisthesis is associated with larger T1 slope measurements compared to anterolisthesis, particularly in higher grades 1. Grade 2 retrolisthesis demonstrates the largest T1 slope, followed by grade 1 retrolisthesis, indicating greater thoracic inlet angle changes and potential impact on cervical sagittal balance 1.
The presence of retrolisthesis correlates with:
- Increased cervical lordosis curvature when T1 slope is larger 1
- Changes in sagittal vertical axis (SVA C2-C7) that correlate strongly with cranial tilt 1
- Potential for segmental instability requiring assessment with dynamic imaging 1
Diagnostic Evaluation
Flexion and extension radiographs are essential to identify segmental motion in spondylolisthesis, which is critical for surgical planning 2. Upright radiographs provide functional information about axial loading that static imaging cannot capture 2.
MRI remains the initial imaging modality of choice for evaluating spinal pathology when patients have failed conservative therapy and are surgical candidates 2. Kinematic MRI in neutral, flexion, and extension positions allows comprehensive assessment of retrolisthesis and associated dynamic changes 1.