Can the Alpha Angle Assessment of Cam Impingement Predict Acetabular Cartilage Delamination?
Bibliographic record
Abstract
BACKGROUND: Substantial acetabular cartilage damage is commonly present in patients suffering from femoral acetabular impingement (FAI). A better understanding of which patient is at risk of developing substantial cartilage damage is critical for establishing appropriate treatment guidelines. QUESTIONS/PURPOSES: We asked: (1) Does the cam deformity severity in FAI as assessed by alpha angle predict acetabular cartilage delamination? And (2) what are the clinical and radiographic findings in patients with acetabular cartilage delamination? METHODS: One hundred sixty-seven patients (129 males, 38 females) with a mean age of 38 years (range, 17-59 years) underwent joint preservation surgery for cam-type FAI. All data were collected prospectively. We assessed center-edge angle and Tönnis grade on AP radiographs and alpha angle on specialized lateral radiographs. Acetabular cartilage damage was assessed intraoperatively using the classification of Beck et al., with Type 3 and greater qualifying as delamination. RESULTS: For all hips, mean alpha angle was 65.5° (range, 41°-90°), and mean center-edge angle was 33.3° (range, 21°-52.5°). Patients with an alpha angle of 65° or greater had an odds ratio (OR) of 4.00 (95% CI, 1.26-12.71) of having Type 3 or greater damage. Increased age (OR, 1.04; 95% CI, 1.01-1.07) and male sex (OR, 2.24; 95% CI, 1.09-4.62) were associated with Type 3 or greater damage, while this was the opposite for acetabular coverage as assessed by center-edge angle (OR, 0.94; 95% CI, 0.89-0.99). CONCLUSIONS: Patients with cam-type FAI and an alpha angle of 65° or more are at increased risk of substantial cartilage damage while increasing acetabular coverage appears to have a protective effect. LEVEL OF EVIDENCE: Level III, prognostic study. See the Instructions for Authors for a complete description of levels of evidence.
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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 | 0.009 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".