Age-related Differences in Volumetric Bone Mineral Density, Structure, and Bone Strength of Surgical Neck of Humerus in Postmenopausal Women.

Objective: Postmenopausal changes in bone mass and structure compromise the mechanical properties of proximal humerus, predisposing it to low-energy fractures with complex morphology. The aim of the study is to investigate associations of bone quality and estimated bone strength of the surgical neck with age after menopause.

Methods: A total of 122 healthy postmenopausal women were recruited from December 2016 to December 2022 and assigned to three groups: the 50-59 years group, the 60-69 years group, and the older than 70 years group. Bone properties of the surgical neck, including volumetric bone mineral density (vBMD), cortical thickness (CTh), the periosteal and medullary size, and estimated indices of bone strength were evaluated by quantitative computed tomography.

Results: Compared to the 50-59 years group, postmenopausal women aged over 70 years were characterized by lower cortical thickness (13.9%) and vBMD (6.65%), as well as reduced strength indices including the minimum and maximum section modulus (Z 18.11%, Z 21.71%), polar section modulus (Z 20.21%), and the minimum and maximum second moments of area (I 21.01%, I 21.43%). Meanwhile, the difference in periosteal diameter and perimeter, total area in three groups did not reach statistical significance. Both cortical thickness and vBMD value were inversely associated with age, showing 10.56% and 23.92% decline. I showed the greatest age-related decrease between age of 54 and 86 years (39.08%), followed by Z (-35.77%), I (-35.73%), Z (-34.90%) and I (-23.92%).The strength indices had stronger correlations with cortical thickness than with bone size or density.

Conclusion: In postmenopausal women, aging is associated with a significant decline in cortical bone thickness and mechanical strength of the proximal humerus, especially over the age of 70 years.