Bone adaptation: Safety factors and load predictability in shaping skeletal form

Area of Science:

• Biomechanics
• Evolutionary Biology
• Skeletal Physiology

Background:

• Skeletal adaptation is crucial for bone's mechanical functions across individual and evolutionary time.
• Mechanobiology studies short-term bone adaptation, while fossil and extant bone analysis reveals long-term evolutionary trends.
• John Currey's work provides foundational insights into bone adaptation mechanisms.

Purpose of the Study:

• To examine bone adaptations across both individual (ontogenetic) and evolutionary timescales.
• To analyze the role of load predictability in skeletal structural and material adaptations.
• To explore the implications of bone adaptation for clinical research and space exploration.

Main Methods:

• Review of historical perspectives on bone adaptation control mechanisms.
• Analysis of safety factors in bone structure.
• Summarization of structural and material adaptations, including mechanotransduction, under varying load predictability.

Main Results:

• Load predictability is a significant factor in bone adaptation across evolutionary and ontogenetic scales.
• Bones with predictable loads exhibit more precise design and lower safety factors.
• Bones with unpredictable loads or limited repair capacity have higher safety factors.

Conclusions:

• Bone design, including safety factors, is optimized based on load predictability.
• Rare, high-consequence loading events necessitate significantly higher safety factors.
• Understanding bone adaptation is vital for treating musculoskeletal diseases and for space exploration.