Vertebral Bone Density—A Critical Element in the Performance of Spinal Implants
Bibliographic record
Abstract
The effectiveness of spinal implants in fixation is dependent upon the bone-implant interface, and thus on vertebral bone density. Current ASTM assessment methods use synthetic elements as vertebral surrogates and therefore, by definition, do not address important in vivo performance and failure characteristics. The purpose of this study is to contrast the mechanical behaviour of pedicle screws in cadaveric vertebrae versus synthetic surrogates. Short-term physiologic axial compression and bending moment were cyclically applied to pedicle screws inserted in lumbar vertebrae and UHMWPE. Kinematics of the pedicle screws in bone and in UHMWPE were significantly different in terms of the range of motion and pivoting and bending points on the screws. For the vertebral fixation, there was a trend towards a more rigid screw-bone interface with increasing bone mineral density. Devices tested using ASTM and ISO test standards may give clinicians and regulatory bodies a false sense of security with respect to implant performance due to their limited scope.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.007 | 0.003 |
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".