Alpha Angle Measurements in Healthy Adult Volunteers Vary Depending on the MRI Plane Acquisition Used
Bibliographic record
Abstract
Background: It has been shown that cam deformities are located at a more anterosuperior location than was previously described. Purpose: To establish, in a large group of asymptomatic participants, the normative range of the alpha angle in the anterosuperior location in both the oblique axial and radial views of magnetic resonance imaging (MRI). Study Design: Cross-sectional study; Level of evidence, 3. Methods: In 197 asymptomatic participants (394 asymptomatic hips) with a mean age of 29.4 years (range, 21.4-50.6 years), T1-weighted MRI scans were studied. The anterosuperior alpha angle measurement was performed by 2 observers using a previously described methodology and also using the radial view. The intraclass correlation coefficient (ICC) was determined for interobserver and intraobserver reliability. Descriptive statistics, the Student t test, correlation studies, and the Bland-Altman technique were used for data analysis. Results: The ICC for interobserver and intraobserver reproducibility was 0.74 (good agreement) and 0.84 (very good agreement), respectively. Anterosuperiorly, the mean (±SD) alpha angles in the oblique axial and radial views were 45.11° ± 8.52° and 50.30° ± 7.91°, respectively ( P < .0001). The upper limits of the 95% reference interval for the oblique axial and radial views were 63° and 66°, respectively. In the oblique axial view, the mean (±SD) alpha angle for male participants was 48.3° ± 7.5° compared with 42.6° ± 6.2° for female participants ( P < .0001), and in the radial view, it was 53.0° ± 7.1° compared with 48.1° ± 5.6°, respectively ( P < .0001). Linear regression analysis demonstrated an insignificant relationship between age and alpha angle, regardless of the imaging plane ( r 2 = 0.06). Conclusion: We suggest using a higher threshold of 63° (in the oblique axial view) and 66° (in the radial view) at the 1:30 clockface position for the diagnosis of a cam-type deformity. This is significantly higher than 50° to 55° at the 3-o’clock position traditionally used based on the oblique axial view that has been initially described.
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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 | 0.002 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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 | 0.001 |
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".