Does Radiographic Beam Angle Affect the Radiocapitellar Ratio Measurement of Subluxation in the Elbow?
Bibliographic record
Abstract
BACKGROUND: Radial head alignment is the key to determine elbow reduction after treatment of subluxations or Monteggia fractures. The radiocapitellar ratio (RCR) quantifies the degree of subluxation, by evaluating radial head alignment with the capitellum of the humerus; this ratio is reproducible when measured on true lateral radiographs of nonsubluxated elbows. However, the impact of beam angulation on RCR measurement is unknown. QUESTIONS/PURPOSES: Our hypotheses were that the RCR of the nonsubluxated elbow would remain in the normal range as the beam angle changed and that the RCR variability would increase for the subluxated elbow with small deviations in the beam angle. METHODS: Radiographs were taken of six healthy cadaveric extremities using beam angles ranging from -20° to 20° along the inferosuperior axis and from -20° to 20° along the dorsoventral axis. The same views then were taken of the six arms with anterior radiocapitellum subluxation followed by posterior radiocapitellum subluxation. RCRs were measured by one observer. As a reference value, the RCR was measured in the 0° to 0° position and the difference between each RCR in a nonreference position was subtracted from each RCR reference to obtain the delta-RCR. An ANOVA was performed to assess the main and interactive effects on the RCR measured in each C-arm position compared with the RCR measured on a true lateral radiograph. RESULTS: The RCR remained in the normal range even as the beam angle of the C-arm varied between -20° and 20°. The position of the beam did not affect the RCR in anteriorly subluxated elbows (p = 0.777), whereas RCR variation increased especially in the presence of posterior radial head subluxation when the C-arm position was 10° or more out of plane (p = 0.006). The inferosuperior malposition of the C-arm had a greater impact on quantification of radial head alignment measurement. Despite that, the RCR measurement is reliable in reduced and subluxated elbows on lateral radiographs with a C-arm position deviation of as much as 20°. CONCLUSIONS: Identification of a subluxated elbow could be made on any lateral radiograph with a beam angulation deviation of as much as 20°. This suggests that the RCR is a useful diagnostic tool for clinical and research purposes, although for subluxated elbows, it is important to pay careful attention to the inferosuperior position of the C-arm.
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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 | 0.004 | 0.011 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| 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 | 0.000 | 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".