Segmental Malalignment With the Bryan Cervical Disc Prosthesis—Does it Occur?
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Bibliographic record
Abstract
The early clinical results with the Bryan Cervical Disc prosthesis are encouraging but 2 recent small published series have noted postoperative radiologic kyphosis of the functional spinal unit (FSU) of 4 and 6 degrees. The current study was undertaken to accurately assess the extent of any sagittal deformity after the use of this prosthesis in a substantial, multisurgeon case series. The neutral, erect x-rays of 67 consecutive patients (88 disc levels) operated by one of 3 surgeons, were examined using manual and digital image analysis techniques for FSU sagittal angulation (lordosis), prosthesis shell angulation, segmental olisthesis, and overall cervical alignment. Measurement accuracy was confirmed using interobserver and intraobserver studies. There was a median loss of 2 degrees in FSU lordosis when compared with preoperative imaging (P<0.0001, range: 8-degree loss to 5-degree gain). A median 2 degrees of prosthesis shell kyphosis also occurred (range: 15-degree kyphosis to 12-degree lordosis) but shell angulation correlated weakly with the change in FSU lordosis (rs=0.37, P=0.001). There was a significant difference in the median loss of FSU lordosis between surgeon 1 and surgeons 2 and 3 (3.5 degrees vs. 2 degrees, P=0.005). Median olisthesis of the prosthesis shells was -0.1 mm (range: +1.5 to -2.5 mm). Median postoperative overall cervical lordosis reduced by 4 degrees (P<0.004). A small loss in median FSU lordosis was observed after insertion of the Bryan disc. The observed changes were generally small but varied among both the patients and the surgeons, suggesting that variables may exist which contribute to postoperative sagittal alignment. These are the subject of an accompanying study.
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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 | 0.001 | 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 it