Grade 1 Anterolisthesis of L3 over L5: Anatomical Impossibility
The described finding of "grade 1 anterolisthesis of L3 over L5" is anatomically impossible and represents either a reporting error or misunderstanding of spinal anatomy. This terminology suggests that the L3 vertebra has slipped forward relative to L5, but L4 sits between these two vertebrae, making direct slippage of L3 over L5 physically impossible in an intact spine.
Understanding the Anatomical Error
- Normal spinal anatomy dictates that vertebrae can only slip relative to their immediately adjacent vertebrae - L3 can only slip forward over L4, L4 over L5, and L5 over S1 1
- The lumbar spine consists of five vertebrae (L1-L5) stacked sequentially, with each vertebra articulating only with its immediate neighbors through facet joints and intervertebral discs 1
- Anterolisthesis refers to forward slippage of one vertebra relative to the vertebra immediately below it, not vertebrae separated by intervening segments 2, 1
What Was Likely Intended
The report most likely meant one of the following:
- Grade 1 anterolisthesis of L3 over L4 - forward slippage of the third lumbar vertebra relative to the fourth, representing 20-25% displacement 3
- Grade 1 anterolisthesis of L4 over L5 - forward slippage of the fourth lumbar vertebra relative to the fifth, the most common site for degenerative spondylolisthesis 4
- Grade 1 anterolisthesis of L5 over S1 - forward slippage of the fifth lumbar vertebra relative to the sacrum, another common location 5, 2, 1
Clinical Significance of Grade 1 Anterolisthesis
A solitary, asymptomatic grade 1 anterolisthesis (20-25% forward displacement) is likely of minimal to no clinical significance, as grade 1 fractures have greater overlap with non-fracture deformities compared to higher grades 3
Grading System for Anterolisthesis
- Grade 1 (mild): 20-25% forward displacement of the vertebral body 3
- Grade 2 (moderate): 26-40% forward displacement, more predictive of future complications 3
- Grade 3 (severe): >40% forward displacement, important predictor of fracture risk at vertebral and non-vertebral sites 3
- Grade 4: >75% forward displacement, often requiring surgical intervention 5, 6
Common Locations and Prevalence
- L4-L5 is the most common site for degenerative anterolisthesis, with prevalence of 36.5% in older African American women 4
- L5-S1 anterolisthesis occurs in 29.6% of older African American women, often associated with pars interarticularis defects 1, 4
- L3-L4 anterolisthesis is less common, occurring in 13.2% of older women 4
- Anterolisthesis prevalence increases with age but is not necessarily associated with increased back problems or decreased physical function 4
Recommendation for Clarification
Request clarification of the imaging report to identify the correct vertebral levels involved, as accurate anatomical localization is essential for determining clinical significance, treatment planning, and assessing whether surgical intervention might be indicated 3