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Fyhrie DP, Christiansen BA. Bone Material Properties and Skeletal Fragility. Calcif Tissue Int 2015; 97:213-28. [PMID: 25939648 DOI: 10.1007/s00223-015-9997-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/07/2015] [Indexed: 12/27/2022]
Abstract
Deformations of vertebrae and sudden fractures of long bones caused by essentially normal loading are a characteristic problem in osteoporosis. If the loading is normal, then the explanation for and prediction of unexpected bone failure lies in understanding the mechanical properties of the whole bone-which come from its internal and external geometry, the mechanical properties of the hard tissue, and from how well the tissue repairs damage. Modern QCT and MRI imaging systems can measure the geometry of the mineralized tissue quite well in vivo-leaving the mechanical properties of the hard tissue and the ability of bone to repair damage as important unknown factors in predicting fractures. This review explains which material properties must be measured to understand why some bones fail unexpectedly despite our current ability to determine bone geometry and bone mineral content in vivo. Examples of how to measure the important mechanical properties are presented along with some analysis of potential drawbacks of each method. Particular attention is given to methods useful to characterize the loss of bone toughness caused by mechanical fatigue, drug side effects, and damage to the bone matrix.
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Affiliation(s)
- David P Fyhrie
- Department of Orthopaedic Surgery, University of California-Davis Medical Center, 4635 2nd Ave, Suite 2000, Sacramento, CA, 95817, USA,
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Hardisty MR, Kienle DF, Kuhl TL, Stover SM, Fyhrie DP. Strain-induced optical changes in demineralized bone. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:35001. [PMID: 24604533 PMCID: PMC3945466 DOI: 10.1117/1.jbo.19.3.035001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 01/07/2014] [Accepted: 02/03/2014] [Indexed: 06/03/2023]
Abstract
Bone "stress-whitens," becoming visibly white during mechanical loading, immediately prior to failure. Stress-whitening is known to make materials tougher by dissipating mechanical energy. A greater understanding of stress-whitening, both an optical and mechanical phenomenon, may help explain age-related increases in fracture risk that occur without changes in bone mineralization. In this work, we directly measure the optical properties of demineralized bone as a function of deformation and immersing fluid (with different hydrogen-bonding potentials, water, and ethanol). The change in refractive index of demineralized bone was linear: with deformation and not applied force. Changes in refractive index were likely due to pushing low-refractive-index fluid out of specimens and secondarily due to changes in the refractive index of the collagenous phase. Results were consistent with stress-whitening of demineralized bone previously observed. In ethanol, the refractive index values were lower and less sensitive to deformation compared with deionized water, corroborating the sensitivity to fluid hydration. Differences in refractive index were consistent with structural changes in the collagenous phase such as densification that may also occur under mechanical loading. Understanding bone quality, particularly stress-whitening investigated here, may lead to new therapeutic targets and noninvasive methods to assess bone quality.
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Affiliation(s)
- Michael R. Hardisty
- University of California-Davis, School of Medicine, Lawrence J. Ellison Musculoskeletal Research Laboratory, Department of Orthopaedic Surgery, Sacramento, California, 95817
- University of California-Davis, Biomedical Engineering Graduate Group, Davis, California, 95616
| | - Daniel F. Kienle
- University of California-Davis, Department of Chemical Engineering and Materials Science, Biomedical Engineering Graduate Group, Davis, California, 95616
| | - Tonya L. Kuhl
- University of California-Davis, Biomedical Engineering Graduate Group, Davis, California, 95616
- University of California-Davis, Department of Chemical Engineering and Materials Science, Biomedical Engineering Graduate Group, Davis, California, 95616
| | - Susan M. Stover
- University of California-Davis, Biomedical Engineering Graduate Group, Davis, California, 95616
- University of California-Davis, School of Veterinary Medicine, JD Wheat Veterinary Orthopedic Research Laboratory, Biomedical Engineering Graduate Group, Davis, 95616
| | - David P. Fyhrie
- University of California-Davis, Biomedical Engineering Graduate Group, Davis, California, 95616
- University of California-Davis, Department of Biomedical Engineering, Davis, California, 95616
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Do stress-whitening and optical clearing of collagenous tissue occur by the same mechanism? J Biomech 2013; 46:2411-8. [DOI: 10.1016/j.jbiomech.2013.07.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 07/12/2013] [Accepted: 07/15/2013] [Indexed: 11/17/2022]
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