JBJS - 2026-03-24 - Journal Article
Three-Dimensional Geometry of the Normal Scapula: A Software Analysis.
Werthel JD, Walch G, Gauci MO, Bauer S, Ogor J, Morvan Y, Walch A
Topics
Key Takeaway
In 369 healthy scapulae, 6–13% exceeded published pathological morphological thresholds for posterior instability, anterior instability, and glenohumeral OA, with younger subjects (<60 years) paradoxically displaying more pathology-resembling geometry than older subjects.
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Summary
This study used CT-based 3D software analysis to characterize scapular morphology in 369 healthy adults and compared parameters between subjects <60 and ≥60 years old against published pathological thresholds. Younger subjects exhibited greater posterior acromial height, posterior acromial coverage, scapular spine angle, and coracoacromial coverage than older subjects (p<0.05 for each). Between 6.0% and 13.3% of healthy scapulae exceeded pathological thresholds across instability and OA categories, suggesting these thresholds lack specificity when applied in isolation.
Key Limitation
The cross-sectional design cannot establish whether threshold-exceeding healthy subjects will develop the predicted pathology, making causal inference between morphology and disease impossible.
Original Abstract
BACKGROUND
Recent evidence suggests that variations in overall scapular morphology may predispose individuals to specific shoulder pathologies. The purposes of this study were to provide a comprehensive 3D analysis of scapular anatomy in a healthy population and to investigate potential age-related differences and associations with pathological thresholds described in the literature.
METHODS
This study included computed tomography scan data from 369 healthy scapulae of subjects ≥18 years of age without shoulder pathology. The scapulae were analyzed to measure key morphological parameters, including glenoid version, acromial coverage, posterior acromial height, coracoid angles, and scapular spine angle. Scapulae of individuals <60 years old were compared with those of individuals ≥60 years old. Morphological thresholds described in previous studies were used to identify the percentage of healthy scapulae that demonstrated values exceeding pathological thresholds.
RESULTS
Significant differences were observed between the scapulae of patients <60 years old and those ≥60 years old, with younger patients generally exhibiting scapular morphologies more closely resembling those reported in pathological cases. Key differences included posterior acromial height, posterior acromial coverage, scapular spine angle, and coracoacromial coverage (p < 0.05 for each). Across the cohort, a small percentage of healthy scapulae exceeded pathological thresholds published in the literature for posterior instability (posterior acromial height: 12.2%; posterior acromial coverage: 12.7%), anterior instability (coracoid pillar angle 2: 9.5%; scapular spine angle 2: 13.3%; glenoid rotation: 0.5%), and primary osteoarthritis (anterior coracoid plane coverage: 6.5%; coracoacromial plane coverage: 10.8%; posterior acromial coverage: 10.3%; critical shoulder angle: 6.0%).
CONCLUSIONS
This study provides a comprehensive reference for the 3D morphology of the healthy scapula. The results reveal relatively low variability in shape among healthy scapulae; however, specific morphological variations appear to predispose individuals to certain pathologies. As degenerative conditions develop over time, younger subjects with such predispositions may gradually transition out of the healthy cohort. Conversely, individuals who remain healthy beyond 60 years of age likely possess a "healthy" anatomy that does not favor pathology, representing the true cohort of healthy subjects.
CLINICAL RELEVANCE
Understanding the 3D morphology of the healthy scapula could enhance our knowledge of the etiology of conditions such as posterior and anterior instability and primary osteoarthritis, potentially improving their surgical management.