Pedicle Screw Motion in the Osteoporotic Spine After Augmentation With Laminar Hooks, Sublaminar Wires, or Calcium Phosphate Cement: A Comparative Analysis
Bibliographic record
Abstract
STUDY DESIGN: A biomechanical study addressing the motion of pedicle screws in a human cadaveric, osteoporotic spine model. OBJECTIVES: To compare the fixation of pedicle screws in an osteoporotic spine model after augmentation with laminar hooks, sublaminar wires, or calcium phosphate cement and to determine the kinematic patterns of these screws. SUMMARY OF BACKGROUND DATA: Numerous techniques exist for improving the quality of fixation within the osteoporotic spine, including supplementing the construct with laminar hooks, sublaminar wires, or calcium phosphate cement. Direct comparisons of these practices, however, are lacking. METHODS.: Twenty-four cadaveric lumbar vertebrae were instrumented with a pedicle screw and rod construct augmented with laminar hooks, sublaminar wires, or calcium phosphate cement. The screws were tested cyclically with physiologic loads. Rigid body motions of the screws were measured using an optoelectronic camera system, and the motion at the screw tip and at the screw head were calculated. Screw motions were compared using nonparametric paired statistical analysis. RESULTS: Between augmentation groups, there were no significant differences in the magnitude of motion at the screw head and at the screw tip. After calcium phosphate cement supplementation, screw motion was predominantly rotational in nature, whereas rigid body translation of the screw was more common with sublaminar wires or laminar hooks. CONCLUSIONS: The three augmentation techniques were similar in their ability to enhance the rigidity of fixation of the pedicle screws. Differences did exist, however, in the patterns of pedicle screw motion, with the calcium phosphate cement augmentation resulting in less rigid body translation than the other two techniques.
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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) | 0.001 | 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".