Age- and sex-related differences in rotator cuff and deltoid muscle: A 3D segmentation analysis in healthy shoulders

INTRODUCTION: Muscle volume and fatty infiltration of the rotator cuff and deltoid may influence shoulder function and affect outcomes following rotator cuff repair and shoulder arthroplasty. However, age- and sex-specific changes and reference values for these parameters in healthy individuals remain limited. Establishing such benchmarks may help differentiate physiological muscle changes from pathological degeneration and improve surgical decision-making and outcome predictions. This study aimed to quantify age- and sex-related differences in rotator cuff and deltoid muscle characteristics using quantitative 3D CT-based muscle segmentation in healthy shoulders. METHODS: , respectively). Sex- and age-related comparisons, correlations, and combined effects of age and sex using two-way ANOVA were evaluated. RESULTS: appeared more pronounced in males, whereas age-related differences in females were primarily observed in fat-related parameters. CONCLUSION: Significant age- and sex-related differences exist in rotator cuff and deltoid muscle volume and fatty infiltration in healthy shoulders. The presented sex- and age-specific reference values may help contextualize and distinguish physiological from pathological muscle changes. LEVEL OF EVIDENCE: Study; Imaging.