Thoracolumbar Sagittal Morphology and Segmental Inclination
Bibliographic record
Abstract
STUDY DESIGN: A cross-sectional cohort study. OBJECTIVE: To present a normative value reference of spinal segmental inclination stratified by age and pelvic incidence (PI), and to clarify the impact of segmental inclination on spinal sagittal morphology. SUMMARY OF BACKGROUND DATA: Thoracolumbar segmental inclination has been shown to correlate with the clinical outcomes of adult spinal deformity surgery. However, there currently exists no normative value reference in a large sample of asymptomatic population. MATERIALS AND METHODS: Asymptomatic adult volunteers were enrolled from the community. All volunteers underwent a standing full-spine anteroposterior and lateral radiograph. Lumbar tilt (LT) and thoracic tilt (TT) were measured to quantify the segmental inclination of the lumbar and thoracic spine. Regional curvature, global balance, and thoracolumbar apex were analyzed across different age and PI groups. The correlation between sagittal parameters and age was analyzed using Pearson correlation tests. RESULTS: A total of 618 volunteers were included with a mean age of 38.7 ± 17.1 years (range 18-82 yr). As age increased, the LT and TT significantly increased ( P <0.001). The LT was significantly correlated with PI (r=0.410, P <0.001), with the low PI group exhibiting a greater negative LT. The TT remained constant across different PI groups. Compared with the young and middle-aged groups, the thoracic apex and lumbar apex were located more caudally in the elderly group ( P <0.001). Subjects with a more caudal lumbar apex exhibited a greater negative LT, and those with a more caudal thoracic apex exhibited a greater positive TT. CONCLUSIONS: The thoracic spine naturally adapts to a relatively neutral position, yet it tends to tilt forward with aging. The physiological lumbar inclination is predominantly determined by the PI value with a slight backward tilt and tends to counteract the anterior truncal inclination with advanced age. Physiological segmental inclination should be considered in spinal surgical planning.
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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 | 0.001 | 0.001 |
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".