Microindentation can discriminate between damaged and intact human bone tissue.

Area of Science:

• Biomedical Engineering
• Orthopedics
• Materials Science

Background:

• Bone mineral density and microarchitecture predict bone strength but do not fully explain variations.
• Bone microdamage is a critical factor in bone quality, influencing overall bone strength.
• Understanding microdamage is essential for accurate bone strength assessment.

Purpose of the Study:

• To evaluate the efficacy of microindentation in differentiating between intact and severely damaged human vertebral bone tissue.
• To assess the mechanical properties (indentation modulus and hardness) of different bone structural units.
• To investigate the impact of microdamage on bone mechanical properties in vitro.

Main Methods:

• Human vertebral bone slices (N=35) were tested in compression and then subjected to microindentation.
• Indentation moduli and hardness (HV) were measured on trabecular, osteonal, and interstitial bone.
• Regions were microscopically classified as intact or damaged.
• A total of 1190 indentations were performed under wet conditions.

Main Results:

• Damaged bone regions exhibited 50% lower stiffness and hardness compared to undamaged regions.
• Interstitial bone was stiffer and harder than osteonal bone, which was stiffer and harder than trabecular bone (transverse direction).
• Intact trabecular bone showed comparable stiffness to intact osteonal bone and was 16% less stiff than intact interstitial bone (axial direction).
• Mechanical properties were independent of gender but significantly affected by damage and microstructure.

Conclusions:

• Microindentation is a viable technique for discriminating between highly damaged and intact human vertebral bone tissue in vitro.
• The study highlights the significant impact of microdamage on bone mechanical properties.
• Further research is needed to determine if microindentation can detect in vivo damage induced by physiological loads.