Pelvic Positioning in the Supine Position Leads to More Consistent Cup Orientation after Total Hip Arthroplasty
Bibliographic record
Abstract
Aims: This study aims to 1) Determine the difference in pelvic position that occurs between surgery and radiographic, supine, post-operative assessment; 2) Examine how the difference in pelvic position influences subsequent cup orientation and 3) Establish whether pelvic position, and thereafter cup orientation differences exist between THAs performed in the supine versus the lateral decubitus positions. Materials and Methods: 321 THAs who had intra-operative, post-cup impaction, AP pelvic radiograph, in the operative position were studied; 167 were performed with patient supine (anterior approach), whilst 154 were performed in lateral decubitus (posterior approach). Cup inclination/anteversion was measured from intra- and post-operative radiographs and difference (Δ) was determined. The target zone was inclination/anteversion of 40/20°±10°. Change in pelvic position (tilt, rotation, obliquity) between surgery and post-operatively was calculated from Δinclination/anteversion using the Levenberg-Marquardt algorithm. Results: The post-operative inclination/anteversion was 40°±8/23°±9. 74 had Δinclination and/or Δanteversion>±10° (21%). Intra-operatively (compared to post-operative), the pelvis was on average 4°±10 anteriorly tilted; 1°±10 internally rotated and 1°±5 adducted. Having Δinclination and/or Δanteversion >±10° was associated with a 3.5 odds ratio of having a cup outside the target. A greater proportion of hips operated in the lateral decubitus had Δinclination and/or Δanteversion >±10° (54/153), compared to supine (8/167) (p<0.001). A greater number of cups achieved the target orientation in supine (120/167;73%), compared to lateral position (67/153;44%) (p<0.001). Intra-operatively, pelvis was more anteriorly tilted (p<0.001) and hemi-pelvis was more internally rotated (p=0.04) in lateral position. Conclusion: Pelvic movement is significantly less in supine position, which leads to more consistent cup orientation. Significant differences in pelvic tilt and rotation were seen in the lateral position. Clinical Relevance: Understanding the differences in pelvic orientation and cup orientation between supine and lateral decubitus positions may facilitate better intraoperative practices for surgeons.
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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 | 0.000 | 0.002 |
| 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) | 0.002 | 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 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".