Is all cortical bone remodeling initiated by microdamage?

Area of Science:

• Biomechanical Engineering
• Skeletal Biology
• Computational Biology

Background:

• Growing interest exists in whether bone remodeling targets fatigue microdamage, especially in cortical bone.
• The hypothesis that microdamage initiates localized remodeling to repair microcracks is gaining traction.
• However, the spatial association between early remodeling (resorption spaces) and microcracks in cortical bone is not well-established, leaving room for metabolic remodeling theories.

Purpose of the Study:

• To investigate the extent to which microdamage governs bone remodeling.
• To test the unorthodox hypothesis that all cortical bone remodeling is initiated by microcracks.

Main Methods:

• A mathematical analysis was performed.
• Equations were derived based on the hypothesis that remodeling basic multicellular units (BMUs) travel beyond their initiation point.
• The model predicts the spatial association between resorption spaces and microcracks.

Main Results:

• The derived equations indicate that the observed distribution of resorption spaces and microcracks is consistent with the microdamage-initiation hypothesis.
• The model predicts the expected degree of spatial association between resorption spaces and microcracks beyond chance.
• Existing experimental data, though limited, closely matches the model's predictions.

Conclusions:

• The mathematical model supports the hypothesis that microcracks initiate cortical bone remodeling.
• The findings suggest that microdamage plays a significant role in the overall bone remodeling process.
• Further experimental validation is needed, but current data align with the proposed model.