title: Microstructural elasticity and regional heterogeneity in human femoral bone of various ages examined by nano-indentation.
abstract: The elastic modulus and hardness of secondary osteonal and interstitial bone was examined through the thickness of the cortex of human femora of various ages by nano-indentation. There was a clear difference between the stiffness and hardness of secondary osteonal and interstitial bone, the latter being stiffer (F(1,48)=56.0, P<0.001). There were some differences between the bones of different subjects; however, there were no differences that could be reliably associated with the chronological age of the subject, or with differences in location through the thickness of the cortex (F(2,48)=0.21, P=0.810). Previous studies have been equivocal in relating changes in the macroscopic 'composite' material stiffness of bone to the age of the individual. By combining the results of the nano-tests with histological measures, we were able to produce a good relationship of the microstructural properties at the matrix level with the bending modulus of whole bone (R(2)=0.88, P<0.001) and this improved further by taking into account the age of the individual (R(2)=0.94, P<0.001). Our results suggest that using differences in the volumetric proportions of secondary osteons versus interstitial bone, and the properties of these elements/structures in isolation may be a more accurate method of determining differences in elastic modulus of whole bone between individuals of various ages.
authors.affiliation: Department of Biomedical Engineering, University of Memphis, Memphis, TN 38152, USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Rho
authors.forename: P
authors.initials: P
authors.lastname: Zioupos
authors.forename: J D
authors.initials: JD
authors.lastname: Currey
authors.forename: G M
authors.initials: GM
authors.lastname: Pharr
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D004548:Elasticity; D005269:Femur / Q000502:physiology*; D014644:Genetic Variation; D006253:Haversian System / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D036103:Nanotechnology