THE IMPACT OF COMBINED FLEXION AND COMPRESSION ON THE MECHANICAL INTEGRITY OF THE ANNULUS FIBROSUS
Bibliographic record
Abstract
Introduction: Intervertebral disc (IVD) herniation is characterized by an expulsion of nucleus pulposus (NP) material through the annulus fibrosus (AF). The AF contains two major adhesive structures, the intralamellar matrix and the interlamellar matrix, which act to maintain the strength of the AF and prevent NP material migration. As a herniation occurs, clefts form within the intralamellar matrix, pushing the NP between adjacent collagen fibres; meanwhile, delamination of the interlamellar matrix causes the NP to pool between layers of the AF. Further, herniation more readily occurs in a combined loading scenario of both compression and flexion. Flexion, and in particular end range flexion, induces tissue creep, where the elongation of fibres within the AF reduces its capacity for tensile resistance, thereby providing a potential mechanism for why flexion is needed to induce herniation. While previous research has examined the effect of combined flexion and compression on the mechanical properties of the AF, the isolated effect of flexion has not been ascertained.\nAims: The purpose of the current work is to observe the effect of static flexion, in combination with compression, on the intralamellar and interlamellar adhesive properties of the AF.\nMethodology: For this study, the C3/C4 cervical functional spinal units (FSU) of porcine specimens were selected due to their anatomical and biomechanical similarity to human spines. All specimens were loaded under 1200N axial compression and one of the following posture conditions: neutral or static end range flexion for 2-hours. Following loading, six AF samples were dissected from each IVD: four single-layer samples and two multilayer samples. The multi-layer samples underwent peel tests to determine the mechanical properties of the interlamellar matrix while the single-layer samples underwent tensile tests to determine the mechanical properties of the intralamellar matrix. Comparisons between mechanical properties were performed to determine if there was a difference between extraction location (anterior vs posterior), extraction depth (inner vs outer AF) and postural condition. Mechanical properties obtained from these tests were statistically compared across conditions.\nResults: The results demonstrated that flexion had an influence on the mechanical properties of the adhesive matrices of the AF. Regarding the interlamellar matrix, flexion elicited a significant decrease in lamellar adhesive strength when compared to a neutral posture. In consideration to the intralamellar matrix, flexion elicited a decrease in failure point strain when compared to neutral. Furthermore, flexion resulted in a significant increase in stiffness of the inner region of the AF compared to the outer region of the AF in flexion and the inner region of the AF in a neutral posture. Flexion also resulted in a significant decrease in toe region strain for the inner region of the AF when compared to the inner region of the AF in a neutral posture. The inner region of the AF was also seen to have a significant increase in stress at 30% strain when compared to the outer region of the AF when undergoing flexion.\nDiscussion/Conclusion: The current findings suggest that the mechanical properties of the interlamellar and intralamellar matrices are sensitive to flexion, creating an environment that promotes an increased potential for herniations to occur.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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) | 0.003 | 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".