Anterolisthesis Definition and Clinical Significance
Anterolisthesis is the forward displacement (slippage) of one vertebra relative to the vertebra below it, most commonly occurring at L5-S1 or L4-L5 levels. 1, 2
Anatomical Understanding
- Anterolisthesis occurs when the normal anatomical structures that resist forward vertebral displacement are compromised, including the posterior facets, neural arch, pedicle, and intervertebral disc. 1
- In your 16-year-old patient with grade 1 slip of L5 on S1, this means the L5 vertebra has slipped forward on the S1 vertebra by less than 25% of the vertebral body width. 1
- The grading system ranges from 1-4 based on severity of displacement, with grade 1 representing the mildest form (0-25% slip). 1
Types and Mechanisms
Two main types are clinically relevant:
- Isthmic spondylolisthesis results from a defect in the pars interarticularis (most common at L5-S1, particularly in younger patients like your 16-year-old). 1
- Degenerative spondylolisthesis arises from facet joint remodeling, most commonly at L4-5 in women over 40 years old. 1
Clinical Presentation
- Symptoms can include lower back pain, stiffness, muscle tightness, and neurological symptoms if nerve compression occurs. 2
- The condition may cause altered gait patterns and difficulties maintaining stable, pain-free posture. 2
- In older African American women, anterolisthesis prevalence reaches 58.3% overall (29.6% at L5-S1), though it is often asymptomatic and not associated with increased back problems. 3
Surgical Considerations
When conservative management fails and surgical intervention becomes necessary:
- Fusion is strongly supported following decompression in patients with stenosis and spondylolisthesis, particularly grade II or higher. 4
- For grade 1 anterolisthesis in a 16-year-old, conservative management should be attempted first, including physical therapy (flexion-based exercises show superior outcomes), body mechanics instruction, and activity modification for 3-4 months minimum. 1
- Surgical management typically involves transpedicular screw fixation with decompression and possible interbody fusion when conservative measures fail. 5
Important Clinical Pitfall
Retrolisthesis (posterior displacement) is distinct from anterolisthesis and carries different clinical implications - it occurs in only 4% of patients but is associated with decreased disc height and increased walking/spinal problems, unlike anterolisthesis which may be asymptomatic. 3