Sexual dimorphism affects tibia size and shape but not tissue-level mechanical properties.

Area of Science:

• Biomechanics
• Orthopedics
• Human Anatomy

Background:

• Females exhibit a higher incidence of stress and fragility fractures compared to males.
• Understanding sex-specific growth influences on bone morphology and tissue quality is crucial for explaining fracture disparities.

Purpose of the Study:

• To determine if females achieve comparable tissue-level mechanical properties to males by skeletal maturity.
• To investigate the relationship between bone cross-sectional morphology and tissue-level mechanical properties in both sexes.

Main Methods:

• Bone beams were machined from the tibial diaphyses of adult females.
• Tissue-level mechanical properties (stiffness, strength, ductility, toughness, damageability) were measured.
• Data were compared between sexes using t-tests, with male data from a previous study.

Main Results:

• Males and females demonstrated nearly identical tissue-level mechanical properties.
• Both sexes exhibited similar age-related declines in mechanical properties.
• Female tibiae were consistently smaller relative to body size than male tibiae.

Conclusions:

• Sex-specific growth patterns influence bone size but not intrinsic tissue mechanical properties.
• Adult females possess relatively undersized long bones, potentially leading to increased damage under load.
• This size difference may contribute to the higher prevalence of stress fractures in females, particularly in physically demanding scenarios.