Wide variations in the alpha angle reporting of the hip in asymptomatic individuals—a systematic review
Bibliographic record
Abstract
The alpha angle is commonly used to quantify cam-type morphologies in hips. However, the threshold values that define a pathological alpha angle remains disputed. To identify the threshold values for the alpha angle measured on X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) in asymptomatic individuals in different radiological modalities. Using the Preferred Reporting Items for Systematic reviews and Meta-Analysis guidelines and checklist, a literature search was conducted in May 2024 by two independent reviewers. The PubMed, Embase, Cochrane, and CINAHL databases were searched using the following search terms: ('Alpha angle') AND (('FAI') OR 'femoroacetabular impingement') AND ((((Imaging) OR CT) OR MRI) OR X ray). Of the studies identified, those measuring the alpha angle using either X-ray, CT, or MRI in an asymptomatic population were included. Study population and, if stated, demographics like gender, ethnicity, and activity level were then compiled using Excel as well as number of individuals and hips, imaging modality and view, method of evaluating symptoms, mean alpha angle, and 95% reference interval. Twenty-five articles were included in the review. Threshold values varied depending on what radiological method was used, with thresholds for X-ray ranging from 61.0° to 122.9°, thresholds for CT ranging from 50.0° to 95.3°, and thresholds for MRI ranging from 52.7° to 103.5°. According to current literature, threshold values indicating increased risk of FAI syndrome vary physiologically and depend on imaging view and modality. Therefore, no single cut-off reliably defines cam morphology and measurements should be interpreted within their clinical context.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.021 | 0.107 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.008 | 0.009 |
| Bibliometrics | 0.015 | 0.016 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".