Correlation of Radiographic Muscle Cross-Sectional Area with Glenohumeral Deformity in Children with Brachial Plexus Birth Palsy
Bibliographic record
Abstract
BACKGROUND: Muscle imbalance about the shoulder in children with persistent brachial plexus birth palsy is thought to contribute to glenohumeral joint deformity. We quantified cross-sectional areas of the internal and external rotator muscles in the shoulder by magnetic resonance imaging in patients with chronic brachial plexopathy and the correlation between these muscle cross-sectional area ratios and glenohumeral deformity. The purposes of this investigation were to evaluate differences in the ratios between affected and unaffected shoulders in the same individual and to assess whether an increased internal to external rotator muscle cross-sectional area correlated with greater glenohumeral deformity. METHODS: This cohort study consisted of magnetic resonance imaging of seventy-four patients with chronic neuropathic changes about the shoulder from brachial plexus birth palsy. There were at least nine patients with scans available for each of the five classified subtypes of glenohumeral deformity: type I (fifteen patients), type II (seventeen), type III (seventeen), type IV (sixteen), and type V (nine). Cross-sectional areas of the pectoralis major, teres minor-infraspinatus (external rotators), and subscapularis muscles were measured. The supraspinatus muscle cross-sectional area could not be reliably measured. The ratio of subscapularis to external rotators, the ratio of pectoralis major to external rotators, and the compound ratio of subscapularis and pectoralis major to external rotators were compared with the severity of the glenohumeral deformity. Passive range of motion, Mallet and Toronto clinical scores, and Narakas type were also compared with the severity of the glenohumeral deformity and the muscle cross-sectional area measurements. RESULTS: Muscle cross-sectional area ratios were significantly correlated with glenohumeral deformity type. The mean ratio of pectoralis major to external rotators for affected shoulders over all deformity types compared with that for unaffected shoulders was significantly increased by 30% (p < 0.001); the mean ratio for subscapularis and pectoralis major to external rotators, by 19% (p = 0.015), and the mean ratio for subscapularis to external rotators, by 10% (p = 0.008). There was a significant increase in the ratio of pectoralis major to external rotators in affected shoulders within each type of deformity. Analysis of variance indicated higher ratios of pectoralis major to external rotator muscle cross-sectional areas in more severe deformity types (p < 0.001). There were significant differences in external rotation measurements with the shoulder at 90 degrees of abduction only among glenohumeral deformity types I, II, and III (p < 0.05). CONCLUSIONS: The degree of muscle imbalance between internal and external rotators about the shoulder is measurable by magnetic resonance imaging in children with persistent brachial plexopathy, and the imbalance correlates with the degree of glenohumeral deformity. Our results may provide useful information to guide the timing and the choice of operative intervention in these children.
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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 | 0.004 |
| 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 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".