High-speed photography of the development of microdamage in trabecular bone during compression
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John Langan, Jeff Scott, and Maria Zhao Computational Sensors Corp., Santa Barbara, California 93103
James C. Weaver Department of Molecular, Cellular and Developmental Biology, University of California–Santa Barbara, Santa Barbara, California 93106
Georg E. Fantner, Patricia Turner, Johannes H. Kindt, and Georg Schitter Physics Department, University of California–Santa Barbara, Santa Barbara, California 93106
Daniel E. Morse Department of Molecular, Cellular and Developmental Biology, University of California–Santa Barbara, Santa Barbara, California 93106
Paul K. Hansma Physics Department, University of California–Santa Barbara, Santa Barbara, California 93106 (Received 4 October 2005; accepted 31 January 2006)
The mechanical properties of healthy and diseased bone tissue were extensively studied in mechanical tests. Most of this research was motivated by the immense costs of health care and social impacts due to osteoporosis in post-menopausal women and the aged. Osteoporosis results in bone loss and change of trabecular architecture, causing a decrease in bone strength. To address the problem of assessing local failure behavior of bone, we combined mechanical compression testing of trabecular bone samples with high-speed photography. In this exploratory study, we investigated healthy, osteoarthritic, and osteoporotic human vertebral trabecular bone compressed at high strain rates. Apparent strains were found to transfer into to a broad range of local strains. Strained trabeculae were seen to whiten with increasing strain. Comparison of whitened regions seen in high-speed photography sequences with scanning electron micrographs showed that the observed whitening was due to the formation of microcracks. From the results of a motion energy filter applied to the recorded movies, we saw that the whitened areas are, presumably, also areas of high deformation. In summary, high-speed photography allows the detection of microdamage in real time, leading toward a better understanding of the local processes involved in bone failure.
I. INTRODUCTION
Mechanical testing of trabecular bone is a vast experimental field,1 mainly motivated by the cost and social impact of osteoporosis, a systemic, skeletal disease,2,3 which leads to a reduction of bone strength and a concomitant increase of fracture risk. Trabecular bone is situated at the end of the long bones and in the spinal column, where it fills all of the inner vertebral space. In the long bones, it transfers loads from joint faces onto the a)
Address all correspondence to this author. e-mail: [email protected] This paper was selected as the Outstanding Meeting Paper for the 2005 MRS Spring Meeting Symposium L Proceedings, Vol. 874. DOI: 10.1557/JMR.2006.0139 J. Mater. Res., Vol. 21, No. 5, May 2006
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midshaft of the bone; in lumbar vertebrae, trabecular bone carries and transfers up to 90% of the applied load.4,5 Thus, a change in trabecular bone quality can have a huge impact on strength and on fracture
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