Page 260 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

BONE MECHANICS 237

TABLE 9.6 Trabecular Tissue Moduli Using a Variety of Experimental and Computational Techniques
Tissue
modulus
(GPa)
Study Testing method Anatomic site No. of specimens Mean SD
Ashman and Rho, 1988 136 Ultrasound Human femur 53 13.0 1.5
Rho et al., 1993 137 Ultrasound Human tibia 20 14.8 1.4
Microtensile 10.4 3.5
Rho et al., 1997 61 Nanoindentation Human vertebra 2 13.4 2.0
Zysset et al., 1998 152 Nanoindentation Human femoral neck 8 11.4 5.6
Hou et al., 1998 153 FEM Human vertebra 28 5.7 1.6
Ladd et al., 1998 154 FEM Human vertebra 5 6.6 1.0
Turner et al., 1999 138 Nanoindentation Human distal femur 1 18.1 1.7
Ultrasound 17.5 1.1
Niebur et al., 2000 139 FEM Bovine tibia 7 18.7 3.4

studies that the yield strains for trabecular tissue are similar to those for cortical bone, being higher
in compression than in tension. 139 Experimental studies on machined microbeams have shown that
the fatigue strength of trabecular tissue is lower than that of cortical tissue. 141

9.7 CONCLUDING REMARKS

The field of bone mechanics has evolved to a very sophisticated level where mechanical properties
of cortical and trabecular bone are available for many anatomic sites. Studies have also reported on
the effects of bone density, aging, and disease on these properties, enabling researchers to perform
highly detailed specimen-specific analyses on whole bone and bone-implant systems. We have
reviewed here much of that literature. Our focus was on data for human bone, although we reported
bovine data when no other reliable data were available. One important theme in bone mechanics is
to account for the substantial heterogeneity in bone properties that can occur for both cortical and
trabecular bone, particularly for the latter. The heterogeneity results from aging, disease, and natural
interindividual biological variation and thus occurs longitudinally and cross-sectionally in popu-
lations. The heterogeneity also exists spatially within bones. Successful structural analysis depends
on appreciation of this heterogeneity so that appropriate material properties are used for the analysis
at hand. Improved understanding of the micromechanics and damage behaviors of bone is also leading
to unique insight into mechanisms of disease and their treatment as well as biological remodeling
and tissue engineering. While a number of excellent texts are available for more detailed study of
these topics and many of those presented here, 73,142–144 it is hoped that this review will provide a
concise basis for practical engineering analysis of bone.

ACKNOWLEDGMENTS

Support is gratefully acknowledged from NIH (AR41481, AR43784), NSF (BES-9625030), and The
Miller Institute for Basic Research in Science, Berkeley, Calif.

REFERENCES

1. Burr, D. B., Forwood, M. R., Fyhrie, D. P., Martin, R. B., Schaffler, M. B., and Turner, C. H. (1997), Bone
microdamage and skeletal fragility in osteoporotic and stress fractures, J. Bone Miner. Res. 12(1):6–15.