Tensile Failure of C2 Pedicles and of Subsequent Direct Repair in a Porcine Model
Bibliographic record
Abstract
STUDY DESIGN: This repeated-measures biomechanical study evaluated the tensile force required to cause bipedicular (hangman's) fractures in isolated porcine C2 specimens, and the subsequent force to failure after direct fracture repair with bipedicular lag screws. OBJECTIVES: To assess the pullout strength of direct lag screw fixation of hangman's fracture, relative to the strength of the intact specimens. SUMMARY OF BACKGROUND DATA: Clinical studies have reported successful treatment of hangman's fractures by direct screw repair followed by a collar after surgery. However, to the authors' best knowledge, there has not yet been a biomechanical analysis of the force required for screw pullout after direct repair. METHODS: Of 60 mounted porcine C2 specimens subjected to tensile anteroposterior force, hangman's fracture occurred in 15 cases, 12 of which were fixed with bipedicular 4.0-mm lag screws. These fixed specimens were retested to failure in the same manner. RESULTS: Most specimens had laminar fractures after the application of tensile force, with 15 of 60 (25%) showing bipedicular fractures. The force to bipedicular failure was 3259.1 +/- 148.5 N (mean +/- standard error of the mean). After screw fixation, the force to failure of the same specimens was 882.0 +/- 108.5 N (mean +/- standard error of the mean), or 27.3% of the intact bone. CONCLUSIONS: The pullout strength was substantial (882 N), although the relative strength of fixation was only 27.3% of the fracture strength shown by the intact specimens. The findings are discussed in relation to previous studies. To the authors' best knowledge, this is the first study to examine screw pullout forces after direct repair of hangman's fracture.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".