Mechanical age-related differences in the human cadaveric annulus fibrosus
Bibliographic record
Abstract
PURPOSE: As humans age, the intervertebral disc begins to deteriorate and lose structural integrity. The purpose of this study was to examine age-related mechanical differences of the annulus fibrosus in a human cadaveric model. METHODS: Twenty-two discs were removed from eight soft fixed human cadaveric spine segments (T10-S1) ranging from 53 to 90 years of age; 5 male, 3 female. All discs were a degenerative grade of 3 or higher. Single layer (n = 22), bilayer (n = 22), and multilayer annulus samples (n = 37) were mechanically tested from of the excised discs. Single layer and bilayer samples were mechanically tested in tension; single layer testing isolated the intralamellar matrix while bilayer testing provided a more holistic measure of the annular mechanical properties. The multilayer samples were tested via a 180° peel test to investigate the interlamellar matrix. From these tests, numerous mechanical properties were quantified. RESULTS: Age was found to significantly affect single and bilayer stiffness and numerous stress properties including single layer failure stress, bilayer end of toe-region stress, and bilayer stress at 15 % strain such that as age increased, the magnitude of these mechanical properties decreased. In contrast, age did not affect any peel test mechanical property (p > 0.05). CONCLUSION: This study demonstrated that, with increasing age, the annulus fibrosus becomes more compliant and weaker. However, the adhesive matrix found between the lamellae of the annulus does not appear to be impacted by age.
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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) | 0.003 | 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".