Hierarchy of Bone Microdamage at Multiple Length Scales

Area of Science:

• Biomaterials Science
• Biomechanics
• Orthopedic Research

Background:

• Bone fracture is critically determined by microdamage formation.
• The extracellular matrix (ECM) and applied loading dictate the type of bone damage.
• Bone's hierarchical composite structure suggests potential for hierarchical damage patterns.

Purpose of the Study:

• To review and identify key length scales contributing to bone microdamage hierarchy.
• To understand the role of microstructural features and energy dissipation mechanisms in bone's resistance to loading.
• To investigate the impact of loading conditions and ECM quality on microdamage hierarchy, particularly with aging and disease.

Main Methods:

• Reanalysis of existing literature reports on in vivo and in vitro microdamage observations.
• Inclusion of new, unpublished data.
• Identification of three key length scales: mineralized collagen fibrils, lamellar, and osteonal levels.

Main Results:

• Three hierarchical length scales (mineralized collagen fibrils, lamellar, and osteonal levels) are identified as key contributors to microdamage hierarchy and energy dissipation.
• Bone's inherent ECM hierarchy provides specific microstructural features and energy dissipation mechanisms at different scales.
• These mechanisms enable bone to effectively resist various components of physiological loading.

Conclusions:

• The hierarchical nature of bone's ECM is crucial for its mechanical integrity and resistance to fracture.
• Understanding microdamage hierarchy is essential for predicting bone's response to loading, aging, and disease.
• Further investigation into how loading and ECM quality affect this hierarchy is warranted, especially concerning age-related changes.