Sonoanatomy of the Lumbar Spine of Pregnant Women at Term
Bibliographic record
Abstract
BACKGROUND AND OBJECTIVES: Spinal ultrasound offers valuable information to facilitate the placement of lumbar neuraxial anesthesia. Lumbar spine sonograms are unique, and aspects may appear atypical at times, particularly the ligamentum flavum (LF). The objective of this study was to describe the sonoanatomy of the lumbar spine and to determine the frequency of atypical images of the LF in pregnant women at term. METHODS: Using a 2-5 MHz curvilinear transducer, we imaged all the lumbar interspaces in the left and right paramedian longitudinal and transverse planes. The images were categorized as typical, atypical or inconclusive. The primary outcome was the presence of an atypical image of the LF in the transverse plane. The distance from the skin to the epidural space, and the dural sac width, were also measured. RESULTS: One hundred subjects were studied. All the images in the longitudinal planes were conclusive and typical, whereas the number of inconclusive images in the transverse plane increased from L1-L2 to L5-S1 (1, 0, 4, 9, and 34, respectively). The incidence of atypical LF images in the transverse plane was 2.0% at L1-L2, 1.0% at L2-L3, 3.1% at L3-L4, 19.8% at L4-L5, and 28.8% at L5-S1. CONCLUSIONS: The paramedian longitudinal sonograms of the lumbar spine are of superior quality to those obtained in the transverse plane. When using the transverse approach, a high incidence of inconclusive sonograms should be expected in the lower segments. The incidence of atypical LF images, especially in the upper lumbar segments, warrants further investigation because it can have implications for the epidural technique.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".