EP5.20 CT Morphology of Femoroacetabular Impingement from a Large, Multicenter Cohort
Bibliographic record
Abstract
Abstract Introduction: Our understanding of femoroacetabular impingement (FAI) continues to improve. Low-dose computed tomography (CT) has been increasingly utilized due to its improved ability to characterize the complex and variable hip morphologies of FAI patients, compared to plain radiographs. This study defined FAI morphology in modern FAI. Methods: A multi-center, prospective cohort of FAI patients undergoing primary arthroscopy was performed. Patients 14-45 years of age with idiopathic FAI were included. Low-dose CT was used for preoperative planning. Morphological characteristics included standard femoral and acetabular parameters. From these, we calculated McKibbin Indices and cam types. Cam was classified as mild (<63°), moderate (63°-75°), and severe (>75°). Extent of cam was focal (only at 1:30) or nonfocal (if extending to 12:00 or 3:00). CT over- versus under-coverage was determined based on previously published thresholds. Results: There were 604 patients with CT data. Mean age was 24.9 years with 55.9% female predominance. Most had mild focal cam morphology (40.7%), followed by non-focal (26.7%), severe non-focal (19.8%), moderate non-focal (9.1%), and mild non-focal (3.8%). There were 32% (n=193) with high femoral version and 8.9% (n=54) with low femoral version. Stratifying cam type by femoral version, the most common combinations were mild focal cam with normal femoral version (20.3%), moderate focal cam with normal femoral version (15%), and mild focal cam with high femoral version (14%). There was lateral overcoverage in 20.6% and undercoverage in 18.0%. Stratifying cam type by coverage, the most common combinations were mild focal cam with normal coverage (23.7%), moderate focal cam with normal coverage (13.0%), and severe nonfocal cam with normal coverage (11.4%). Conclusion: Utiliizing low-dose CT in a large cohort of FAI patients, we characterized this generation of FAI patient. Stratifying cam burden by femoral version found that the most common type was mild focal cam and normal version followed by moderate focal cam and normal version and mild focal cam and high version. Stratifying cam burden by coverage, the most common type was mild focal cam and normal coverage followed by moderate focal cam with normal coverage and severe nonfocal cam with normal coverage.
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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) | 0.001 | 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".