What is anterolisthesis?

What is Anterolisthesis?

Anterolisthesis is the forward slippage of one vertebra over the vertebra directly below it, most commonly occurring in the lumbar spine at L4-L5 or L5-S1. 1

Anatomical Definition and Mechanism

• Anterolisthesis represents a specific type of spondylolisthesis where the vertebral body translates anteriorly (forward) relative to the adjacent inferior vertebra 1
• This condition differs from retrolisthesis, where the vertebra slips backward instead of forward 1
• The forward displacement occurs most frequently at the L4 vertebral level and is more common in women 1

Pathophysiology and Causes

• Anterolisthesis typically develops from separation of the neural arch from the vertebral body (spondylolysis), predominantly occurring at the pars interarticularis 2
• The condition is strongly correlated with activities that exert repetitive stress on the lower spine, rather than being purely congenital 2
• Degenerative changes, including increased pedicle-facet angle and W-shaped facet joints, are statistically associated with the development of anterolisthesis 1

Clinical Patterns

• Single-level anterolisthesis is more common than multilevel involvement, with 93 of 132 single-level cases showing anterior slippage 1
• When multilevel spondylolisthesis occurs, approximately 94% involve two segments, with combined anterior and posterior slippage patterns possible 1
• Traumatic anterolisthesis can occur at multiple levels simultaneously through pedicle avulsion, though this is rare and typically results from high-energy trauma such as falls from height 3

Grading and Severity

• The degree of forward slip is graded from I to IV, with higher grades indicating more severe displacement 3
• Grade I-II anterolisthesis is considered low-grade and typically managed conservatively initially 4
• Grade IV anterolisthesis represents severe displacement requiring urgent surgical intervention 3

Clinical Significance

• Anterolisthesis creates spinal instability that significantly increases the risk of clinical and radiographic failure after decompression procedures alone 5, 6
• The presence of any degree of anterolisthesis constitutes documented spinal instability and represents a Grade B indication for fusion when surgical decompression is required 7, 8
• Patients with stenosis and anterolisthesis achieve 93-96% excellent/good outcomes with decompression plus fusion, compared to only 44% with decompression alone 7, 6

Radiographic Identification

• Anterolisthesis is diagnosed on standing lateral radiographs by measuring the forward translation of the superior vertebral body 9
• Dynamic flexion-extension films may reveal instability not apparent on static imaging, with >3-4mm translation or >10 degrees angulation indicating significant instability 7
• Associated findings include disc space narrowing, facet arthropathy, and pars interarticularis defects 8

Treatment Implications

• Conservative management with physical therapy, activity modification, and pain control is first-line for low-grade anterolisthesis without neurological deficits 4
• Surgical intervention with decompression and fusion is indicated when anterolisthesis is associated with progressive neurological deficits, severe pain, or significant instability 4
• The presence of anterolisthesis changes the surgical approach from decompression alone to decompression with instrumented fusion to prevent progression of vertebral misalignment 5, 7