Stress Shielding in Box and Cylinder Cervical Interbody Fusion Cage Designs
Bibliographic record
Abstract
STUDY DESIGN: A numerical analysis of stress shielding of the bone graft in box and cylinder interbody fusion cages was performed. OBJECTIVES: To evaluate the stress shielding characteristics of box and cylinder interbody fusion cages for the cervical spine with regard to their rigidity and contiguous pore size. SUMMARY OF BACKGROUND DATA: Cage design has been shown to influence loading of the augmented bone graft tissue. In addition, a large contiguous pore design is believed to be important to avoid stress shielding effects. METHODS: A two-dimensional axisymmetric, biphasic finite-element model of the cage incorporating the bone graft and the adjacent vertebral bodies was developed. Analysis was performed in two parts. First, the vertebrae were loaded by an axial compressive force, and second, the effect of vertebral penetration by the interbody cage was simulated. RESULTS: Straining of bone graft in the box cage was generally lower than that of the cylinder cage. The strains in the cylinder cage were seen to be more uniformly distributed, whereas in the box cage straining was concentrated in the graft under the endplates. Vertebral penetration by the cylinder cage resulted in significant straining of the bone graft (28% strain), whereas lower strains were determined in the box cage (a maximum of 17% strain). CONCLUSIONS: The central pore in the box design does not seem as effective as the fully open cylinder cage in transferring loads to the augmented graft tissue. Early penetration of the adjacent vertebrae by the cylinder cage may provide early postoperative stability and load the graft tissue, thereby imparting the necessary signals for fusion.
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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 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".