Age-dependent fatigue behaviour of human cortical bone

Area of Science:

• Biomedical Engineering
• Orthopedics
• Gerontology

Background:

• Bone quality is crucial for skeletal integrity, but age-related changes in bone's fatigue behavior remain poorly understood.
• Skeletal fragility increases with age, necessitating research into the underlying mechanisms of bone quality degradation.

Purpose of the Study:

• To investigate the age-dependent fatigue behavior of human bone.
• To identify damage mechanisms contributing to age-related bone fragility.
• To analyze stiffness loss and local tissue properties during fatigue loading in aging bone.

Main Methods:

• Four-point bending fatigue tests were performed on aging human bone samples.
• Stiffness loss was analyzed alongside nanoindentation measurements of local tissue stiffness.
• Histological evaluation assessed tensile and compressive damage to identify failure mechanisms.

Main Results:

• Fatigue life demonstrated an exponential decrease with increasing age.
• Older bone exhibited distinct modulus degradation profiles compared to younger bone.
• Younger bone showed diffuse damage and tensile stiffness loss, while older bone displayed linear microcracks and compressive stiffness loss.

Conclusions:

• Age-related bone fragility is significantly influenced by the propensity of older bone to form linear microcracks over diffuse damage.
• Differences in damage mechanisms and stiffness loss between young and old bone contribute to age-related skeletal fragility.
• Understanding these age-dependent fatigue behaviors is critical for developing interventions against osteoporosis and fractures.