Mechanical Competence and Bone Quality Develop During Skeletal Growth.

Area of Science:

• Orthopedics
• Biomaterials Science
• Developmental Biology

Background:

• Bone quality, encompassing composition and structure, dictates fracture risk.
• Aging and disease negatively impact bone quality and mechanical properties.
• Longitudinal bone growth's effect on bone quality and mechanical competence is largely unexplored.

Purpose of the Study:

• To investigate how bone quality and mechanical properties change during longitudinal bone growth in human femoral cortical bone.
• To compare bone quality and mechanical competence between fetal/infantile and pediatric bone samples.

Main Methods:

• Acquired human femoral cortical bone from fetal, infantile, and pediatric (2-14 years) cases.
• Assessed bone quality (structure, osteocytes, mineralization, collagen orientation).
• Measured tensile deformation using synchrotron X-ray diffraction to evaluate mechanical properties.

Main Results:

• Cortical bone from 2- to 14-year-old cases was 160% stiffer and 83% stronger than fetal/infantile bone.
• Improved mechanical resistance correlated with higher bone volume fraction, better micronscale organization (lamellar vs. woven bone), and higher mineralization.
• Microstructural differences were evident as early as 1-2 years of age.

Conclusions:

• Bone quality and mechanical competence significantly increase during longitudinal bone growth, transitioning from woven to lamellar bone.
• Superior bone quality in older children is attributed to better structural organization and composition.
• Findings highlight inherent weaknesses in fetal/infantile bone, with implications for pediatric fracture risk.