Biomechanical Evaluation of a C1-C2 Posterior Arch Screw Construct
Bibliographic record
Abstract
Study Design In-vitro biomechanical study. Objectives Injuries or degenerative conditions can lead to atlantoaxial instability requiring fixation. We aim to assess and compare the biomechanics of a C1-C2 posterior arch and translaminar screw construct against the Harms procedure for posterior atlantoaxial fixation on a human cadaveric model. Methods Nine human cadaveric cervical specimens from occiput to C3 (C0-C3) were used for range of motion (ROM) testing. Each specimen was tested for 4 configurations: 1. Intact, 2. Destabilized, 3. Harms construct, 4. C1-C2 posterior arch screw (PAS) construct. A pure moment of 1.5 Nm was applied, and ROM of the C1-C2 segment was measured in flexion-extension, lateral bending, and axial rotation. Results The Harms group showed a decrease in ROM in all modes ( P < 0.021), and the PAS group showed a decrease in ROM in flexion-extension and lateral bending ( P < 0.002), but not in lateral bending ( P = 0.176). Compared to the intact condition, Harms showed increased ROM for flexion-extension ( P = 0.012), and PAS did not ( P = 0.258). In lateral bending, both constructs did not significantly reduce ROM ( P > 0.058). In axial rotation, both constructs showed a significant increase in ROM ( P < 0.002). There was no significant difference in ROM when comparing Harms with PAS in flexion-extension ( P = 1.000), lateral bending ( P = 0.163), or axial rotation ( P = 1.000). Conclusions The study demonstrates that a C1-C2 PAS construct restores or increases biomechanical stability compared to the intact condition. C1-C2 PAS offers similar biomechanical stability compared to the Harms construct.
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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 | 0.001 | 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".