Biomechanical Analysis of Corrective Forces in Spinal Instrumentation for Scoliosis Treatment
Bibliographic record
Abstract
In Brief Study Design. Computer modeling and simulations to analyze correction forces at the bone-screw interface in scoliosis instrumentation. Objective. To derive the minimum corrective forces applied on vertebrae through pedicle screws to achieve desired scoliosis corrections and evaluate the actual bone-screw forces associated with 3 types of pedicle screws (monoaxial, polyaxial, and dorsoaxial). Summary of Background Data. The optimum screw pattern has not been established in the literature. The final bone-screw forces in scoliosis instrumentation consist of “true corrective forces” (i.e., the minimum forces required to achieve the desired corrections without considering adequate rod seating at all pedicle screws) and “extra forces” (EF) (i.e., supplementary forces applied to ensure proper rod seating when the attachment of some screws is not in compliance with the attachment of their neighboring screws; they have no benefit to overall corrections). Methods. Using patient-specific computer models, true corrective forces were estimated for 10 spinal instrumentation cases. EF were computed by simulating the instrumentations of the 10 cases using respectively monoaxial, polyaxial, and dorsoaxial screws. Results. The average true corrective forces were 50 ± 30 N. The average bone-screw forces were 229 ± 140 N, 141 ± 99 N, and 103 ± 42 N, respectively, for monoaxial, polyaxial, and dorsoaxial screws; the averages of the EF magnitudes were 205 ± 136 N, 125 ± 93 N, and 65 ± 39 N, respectively. Conclusion. Bone-screw forces to achieve desired corrections can be minimized. However, EF are inevitable to secure the locking of all screws. Higher EF were associated with pedicle screws, with less degrees of freedom for connecting screw body to rod, that is, monoaxial followed by polyaxial and then by dorsoaxial screws. Simulations of 10 scoliosis instrumentations were performed to analyze bone-screw forces. The minimum corrective and the adverse extra forces on bone-screw interface were derived for instrumentations using, respectively, monoaxial, polyaxial, and dorsoaxial screws. The adverse extra bone-screw forces were higher for screws, with less flexibility in connecting vertebra to rod.
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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) | 0.001 | 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) | 0.002 | 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".