Age and Sex Differences in Load-Induced Tibial Cortical Bone Surface Strain Maps

Area of Science:

• Biomechanics
• Skeletal Biology
• Musculoskeletal Research

Background:

• Bone's ability to adapt its structure to mechanical load (mechano-adaptation) is crucial for skeletal health.
• The precise mechanical stimuli and how they change with age and sex remain incompletely understood.
• Previous studies in animal models suggest mechanical strain as a key stimulus for bone adaptation.

Purpose of the Study:

• To investigate age- and sex-dependent variations in mouse cortical bone load-related strains.
• To provide detailed strain maps for in vivo loading experiments in mice.
• To explore differences in bone mechano-adaptation across the lifespan and between sexes.

Main Methods:

• Full-field surface strain mapping was performed on C57BL/6J mouse tibias across a range of applied loads (1-12 N).
• Measurements were taken in young (10 weeks), adult (22 weeks), and old (20 months) male and female mice.
• A non-invasive murine tibial loading model was utilized to apply axial compressive loads.

Main Results:

• Nonuniform strain fields were observed across the tibial surface, with axial loading inducing tension medially.
• Load-induced surface strain patterns and magnitudes exhibited sexually dimorphic changes with aging.
• Strain magnitude generally increased during maturation, with female mice showing higher strains than males; postmaturation aging also revealed sexually dimorphic strain changes.

Conclusions:

• The study provides detailed strain maps of mouse tibias, crucial for future in vivo mechano-adaptation studies.
• Understanding these age- and sex-specific strain patterns is essential for investigating bone adaptation.
• The findings facilitate the design of experiments to precisely control mechanical stimuli and explore bone mechano-adaptation differences in aging and sex.