Model of flexural fatigue damage accumulation for cortical bone

Area of Science:

• Biomechanics
• Materials Science
• Orthopedic Research

Background:

• Cortical bone exhibits complex modulus degradation under fatigue loading.
• Existing models often simplify damage mechanisms, limiting predictive accuracy.
• Understanding fatigue behavior is crucial for bone health and prosthetic design.

Purpose of the Study:

• To develop and validate analytical models for predicting modulus degradation in cortical bone during uniaxial and flexural fatigue.
• To differentiate damage mechanisms under tensile and compressive loading.
• To assess the models' predictive capability using literature and experimental data.

Main Methods:

• Developed mechanistic uniaxial damage models for tension (self-limiting) and compression (non-self-limiting).
• Integrated uniaxial models into a flexural fatigue model using laminated beam theory.
• Calibrated model coefficients using published human cortical bone fatigue data.
• Validated flexural model predictions against laboratory-tested human cortical bone specimens.

Main Results:

• The models accurately captured modulus degradation patterns under uniaxial fatigue.
• Flexural fatigue model predictions showed excellent agreement with experimental data for modulus degradation and fatigue life.
• The distinction between self-limiting tensile damage and non-self-limiting compressive damage was critical.

Conclusions:

• The developed analytical models provide a robust framework for predicting cortical bone fatigue behavior.
• These models enhance understanding of bone's response to cyclic loading, crucial for clinical applications.
• The findings support the use of mechanistic models for biomechanical analysis of bone.