Leveraging ultrashort echo time magnetic resonance imaging to quantify sex-specific adaptations to the glenoid labrum across the lifespan

Abstract The glenoid labrum is a collagen‑rich fibrocartilage structure critical to shoulder stability yet susceptible to age‑related degeneration. Quantitative, in‑vivo assessment of its composition remains limited. Ultrashort echo time MRI with magnetization transfer (UTE‑MT) enables estimation of macromolecular fraction (MMF), a biomarker sensitive to the collagen‑rich matrix content of the glenoid labrum. This study investigated the effect of age, sex, menopause status, and arm dominance on the glenoid labrum MMF. Forty‑two healthy adults (25 females, mean age: 47 ± 15 years; 17 males, mean age: 38 ± 15 years) underwent bilateral shoulder MRI on a 3T system using a double echo steady state sequence (DESS) for segmentation and a custom UTE‑MT protocol to quantify MMF. Labra were segmented from DESS images, and voxel‑wise MMF was computed. Mean MMF was calculated for each arm. A linear mixed-effects model with a random intercept for subject to account for within-subject dependence tested the effects of age, sex, arm dominance, and their respective interactions. A linear mixed effect model with a random intercept for subject tested the effect of menopause status among females on mean MMF. Males exhibited higher mean labral MMF than females (male: 40.4 ± 7.3%, female: 39.6 ± 7.2%; p = 0.016). Age showed no main effect on mean MMF. However, a significant sex‑by‑age interaction indicated a steeper age‑related decline in males ( p = 0.0113). There was no significant effect of arm dominance on mean MMF (dominant: 41.1 ± 7.6%, non-dominant: 38.8 ± 6.9%; p = 0.412), and there was no significance found for the interactions of dominance and sex, dominance and age, or dominance, sex, and age. Among females, mean MMF did not differ by menopause status (premenopausal 39.4 ± 7.4% vs. postmenopausal 39.7 ± 7.1%; p = 0.761). UTE‑MT MRI detects sex‑specific differences in glenoid labrum MMF, with a significant sex‑by‑age interaction despite no main effect of age. These findings support MMF’s potential as a non‑invasive quantitative marker of labral composition and motivates longitudinal studies to define clinically meaningful thresholds and regional variation.