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Differences in sensitivity to microstructure between cyclic- and impact-based microindentation of human cortical
Sasidhar Uppuganti1,2, Mathilde Granke1,2, Mary Kate Manhard3,4
1Department of Orthopaedic Surgery & Rehabilitation, Vanderbilt University Medical Center, 1215 21st Ave. S. Suite 4200, Nashville, Tennessee, 37232.
Summary
Impact microindention (IMI) properties, unlike cyclic reference point microindention (cRPI), are sensitive to bone porosity. Bone material strength index (BMSi) varies across anatomical sites and correlates with porosity and peak bending stress.
Area of Science:
- Orthopaedic Research
- Biomaterials Science
- Skeletal Biology
Background:
- Traditional mechanical properties of bone are well-understood in relation to microstructural features.
- Factors influencing bone resistance to cyclic reference point microindention (cRPI) and impact microindention (IMI) remain largely unidentified.
- Understanding these factors is crucial for assessing bone health and fracture risk.
Purpose of the Study:
- To investigate whether cRPI and IMI properties are influenced by bone microstructure.
- To compare mechanical resistance across different anatomical sites (tibia, radius, humerus) in elderly donors.
- To identify microstructural correlates of IMI and cRPI properties.
Main Methods:
- Indentation testing using BioDent and OsteoProbe on tibia, radius, and humerus from 10 elderly donors.
- Measurement of bone material strength index (BMSi) as the primary IMI output.
- Analysis of pore water content using 1H nuclear magnetic resonance and intra-cortical porosity using micro-computed tomography.
- Correlation analysis between mechanical properties and microstructural parameters (porosity, tissue mineral density, peak bending stress).
Main Results:
- BMSi significantly differed across anatomical sites, being highest in the tibia and lowest in the humerus.
- Intra-cortical porosity was negatively correlated with BMSi in arm bones, and BMSi correlated positively with peak bending stress in the tibia.
- Pore water content was lowest in the tibia and highest in the humerus, potentially explaining BMSi variations.
- No significant microstructural correlations were found for cRPI properties, except for a negative correlation between dissipated energy and tissue mineral density in the tibia.
- IMI, with higher force and larger tip diameter, was sensitive to cortical bone porosity, unlike cRPI.
Conclusions:
- Impact microindention (IMI) is sensitive to bone porosity, a factor not significantly affecting cyclic reference point microindention (cRPI).
- Bone material strength index (BMSi) varies anatomically and correlates with porosity and mechanical strength.
- Microstructural features like porosity and pore water content play a role in determining IMI resistance in cortical bone.
