Unilateral Cervical Facet Dislocation: Injury Mechanism and Biomechanical Consequences
Why this work is in the frame
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Bibliographic record
Abstract
STUDY DESIGN: Human cadaveric cervical spines were subjected to nondestructive repeated-measures flexibility tests before, during, and after unilateral facet dislocation. OBJECTIVES: To assess the relative stability and kinematics of the spine in the normal condition, after unilateral facet lock without bony injury and after reducing (unlocking) the facet dislocation. SUMMARY OF BACKGROUND DATA: Experimental unilateral facet dislocation has been studied only when associated with extensive damage to disc, bone, or both. The relative stability of the normal, locked, and unlocked cervical spine has not been studied. METHODS: Unilateral facet dislocation with minimal associated injury was created by slowly applying axial torque while specimens were bent laterally and flexed. Before and after injury, nondestructive torques were applied about each anatomic axis, while three-dimensional specimen motion was recorded stereophotogrammetrically. RESULTS: Unilateral facet dislocation was created with a mean axial torque of 10.2 +/- 2.7 Nm. After locking, range of motion, lax zone, and stiff zone were significantly reduced relative to normal (P < 0.05). After unlocking, the same parameters were significantly increased relative to normal. The position of the axis of rotation shifted when the facet was locked and the centrode elongated after the facet was unlocked. CONCLUSIONS: Unilateral facet dislocation without fracture can be created with moderate loads when axial torque is applied while the facet is distracted. The spine is stable while the articular masses are locked unilaterally; however, the motion segment becomes overtly unstable after the facet dislocation is reduced.
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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) | 0.001 | 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 it