The Effect of Lumbar Flexion and Extension on Disc Contour Abnormality Measured Quantitatively on Magnetic Resonance Imaging
Bibliographic record
Abstract
In Brief Study Design. Experimental study with subjects as their own control. Objective. To determine if lumbar disc contour abnormality dimensions, measured quantitatively, differ in flexed, neutral or extended positions. Summary of Background Data. MRIs obtained lying supine are used to determine the degree of lumbar disc contour abnormality (bulging or herniation). Variations in positioning are suspected to influence this assessment. Methods. Lumbar MR images for 26 male volunteers (24–74 years of age), with or without low back pain, were obtained with the subjects lying in neutral, maximal flexion, and maximal extension positions allowable within a conventional 1.5T MR scanner. Quantitative measures of anterior and posterior disc contour abnormality were obtained for each position. Results. Statistically significant differences in disc angles were obtained between positions (2°–5°) for all levels. Posterior contour abnormality was significantly smaller in flexion and extension than in the neutral position (9.5%–30.1%). Posterior contour abnormality in extension was similar or smaller than in flexion. Anterior contour abnormality was significantly smaller in extension than flexion and smaller in the neutral position than flexion. Conclusion. Spine position should be standardized when assessing disc contour abnormality with MRI. The largest measured disc contour abnormalities when lying supine in a standard MR scanner are observed in the neutral position, as opposed to flexion or extension. Disc contour abnormality was measured quantitatively in a population-based sample to determine if dimensions differ between flexed, neutral, or extended positions. Posterior contour abnormality was largest in neutral and smaller in extension than flexion. Subjects with severe contour abnormality had the largest differences in dimensions of contour abnormality between positions.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
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".