Anterior Occiput-to-Axis Screw Fixation
Bibliographic record
Abstract
STUDY DESIGN: A case report of anterior screw fixation from the axis to the occiput is described, as is the surgical technique. The pertinent anatomy is described with a radiographic assessment of the feasibility, safety, and general applicability of this technique. OBJECTIVES: To describe a novel technique of anterior occipitocervical fixation and the pertinent anatomy. SUMMARY OF BACKGROUND DATA: In unique clinical situations where posterior fixation techniques may not be possible or may have already failed, an anterior screw fixation technique may add stability to further attempts at obtaining a posterior arthrodesis. METHODS: A case report is presented, followed by a detailed description of the surgical technique. Ten normal cervical spines had radiographs and computed tomography scans with reformats reviewed to determine screw entry points, target points, and proposed screw trajectories. Following screw insertion in eight fresh frozen human cadaver spine specimens, dissection verified screw location relative to structures at risk. RESULTS: The ideal entry point is located caudal to the C2 superior facet joint in line with the medial third of the C2 superior facet. The screw is directed 25 degrees posteriorly in the sagittal plane and 15 degrees laterally in the coronal plane. The screw tip is located in the posterolateral third of the occipital condyle. Anatomic variation is considerable and makes this technique inadvisable in up to 20% of cases. Structures at risk include the vertebral artery and the hypoglossal nerve. CONCLUSIONS: This new technique of anterior fixation of the atlas to the occiput is feasible and safe if meticulous surgical planning is performed.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.003 | 0.002 |
| Insufficient payload (model declined to judge) | 0.006 | 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".