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Ma S, Goh EL, Tay T, Wiles CC, Boughton O, Churchwell JH, Wu Y, Karunaratne A, Bhattacharya R, Terrill N, Cobb JP, Hansen U, Abel RL. Nanoscale mechanisms in age-related hip-fractures. Sci Rep 2020; 10:14208. [PMID: 32848149 PMCID: PMC7450077 DOI: 10.1038/s41598-020-69783-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 07/13/2020] [Indexed: 01/12/2023] Open
Abstract
Nanoscale mineralized collagen fibrils may be important determinants of whole-bone mechanical properties and contribute to the risk of age-related fractures. In a cross-sectional study nano- and tissue-level mechanics were compared across trabecular sections from the proximal femora of three groups (n = 10 each): ageing non-fractured donors (Controls); untreated fracture patients (Fx-Untreated); bisphosphonate-treated fracture patients (Fx-BisTreated). Collagen fibril, mineral and tissue mechanics were measured using synchrotron X-Ray diffraction of bone sections under load. Mechanical data were compared across groups, and tissue-level data were regressed against nano. Compared to controls fracture patients exhibited significantly lower critical tissue strain, max strain and normalized strength, with lower peak fibril and mineral strain. Bisphosphonate-treated exhibited the lowest properties. In all three groups, peak mineral strain coincided with maximum tissue strength (i.e. ultimate stress), whilst peak fibril strain occurred afterwards (i.e. higher tissue strain). Tissue strain and strength were positively and strongly correlated with peak fibril and mineral strains. Age-related fractures were associated with lower peak fibril and mineral strain irrespective of treatment. Indicating earlier mineral disengagement and the subsequent onset of fibril sliding is one of the key mechanisms leading to fracture. Treatments for fragility should target collagen-mineral interactions to restore nano-scale strain to that of healthy bone.
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Affiliation(s)
- Shaocheng Ma
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ, UK.,MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - En Lin Goh
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Tabitha Tay
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Crispin C Wiles
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK.,Warwick Medical School, University of Warwick, Coventry, CV4 7AL, UK
| | - Oliver Boughton
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - John H Churchwell
- Department of Medical Physics and Biomedical Engineering, University College London, London, WCIE 6BT, UK
| | - Yong Wu
- Centre for Medicine, University of Leicester Medical School, Leicester, LE1 7HA, UK
| | - Angelo Karunaratne
- Department of Mechanical Engineering, Faculty of Engineering, University of Moratuwa, Moratuwa, 10400, Sri Lanka
| | - Rajarshi Bhattacharya
- St. Mary's Hospital, North West London Major Trauma Centre, Imperial College, London, W2 1NY, UK
| | - Nick Terrill
- Diamond Light Source, Diamond House, Harwell Science and Innovation Campus, Didcot, OX11 0DE, UK
| | - Justin P Cobb
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Ulrich Hansen
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ, UK
| | - Richard L Abel
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK.
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Gustafsson A, Mathavan N, Turunen MJ, Engqvist J, Khayyeri H, Hall SA, Isaksson H. Linking multiscale deformation to microstructure in cortical bone using in situ loading, digital image correlation and synchrotron X-ray scattering. Acta Biomater 2018; 69:323-331. [PMID: 29410089 DOI: 10.1016/j.actbio.2018.01.037] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/20/2017] [Accepted: 01/25/2018] [Indexed: 11/27/2022]
Abstract
The incidence of fragility fractures is expected to increase in the near future due to an aging population. Therefore, improved tools for fracture prediction are required to treat and prevent these injuries efficiently. For such tools to succeed, a better understanding of the deformation mechanisms in bone over different length scales is needed. In this study, an experimental setup including mechanical tensile testing in combination with digital image correlation (DIC) and small/wide angle X-ray scattering (SAXS/WAXS) was used to study deformation at multiple length scales in bovine cortical bone. Furthermore, micro-CT imaging provided detailed information about tissue microstructure. The combination of these techniques enabled measurements of local deformations at the tissue- and nanoscales. The orientation of the microstructure relative to the tensile loading was found to influence the strain magnitude on all length scales. Strains in the collagen fibers were 2-3 times as high as the strains found in the mineral crystals for samples with microstructure oriented parallel to the loading. The local tissue strain at fracture was found to be around 0.5%, independent of tissue orientation. However, the maximum force and the irregularity of the crack path were higher when the load was applied parallel to the tissue orientation. This study clearly shows the potential of combining these different experimental techniques concurrently with mechanical testing to gain a better understanding of bone damage and fracture over multiple length scales in cortical bone. STATEMENT OF SIGNIFICANCE To understand the pathophysiology of bone, it is important to improve our knowledge about the deformation and fracture mechanisms in bone. In this study, we combine several recently available experimental techniques with mechanical loading to investigate the deformation mechanisms in compact bone tissue on several length scales simultaneously. The experimental setup included mechanical tensile testing in combination with digital image correlation, microCT imaging, and small/wide angle X-ray scattering. The combination of techniques enabled measurements of local deformations at the tissue- and nanoscales. The study clearly shows the potential of combining different experimental techniques concurrently with mechanical testing to gain a better understanding of structure-property-function relationships in bone tissue.
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Affiliation(s)
- Anna Gustafsson
- Department of Biomedical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden.
| | - Neashan Mathavan
- Department of Biomedical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden.
| | - Mikael J Turunen
- Department of Biomedical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden; Department of Applied Physics, University of Eastern Finland, POB 1627, FI-702 11 Kuopio, Finland.
| | - Jonas Engqvist
- Division of Solid Mechanics, Lund University, Box 118, SE-221 00 Lund, Sweden.
| | - Hanifeh Khayyeri
- Department of Biomedical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden.
| | - Stephen A Hall
- Division of Solid Mechanics, Lund University, Box 118, SE-221 00 Lund, Sweden.
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Box 118, SE-221 00 Lund, Sweden.
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Karunaratne A, Li S, Bull AMJ. Nano-scale mechanisms explain the stiffening and strengthening of ligament tissue with increasing strain rate. Sci Rep 2018; 8:3707. [PMID: 29487334 PMCID: PMC5829138 DOI: 10.1038/s41598-018-21786-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 02/10/2018] [Indexed: 11/08/2022] Open
Abstract
Ligament failure is a major societal burden causing disability and pain. Failure is caused by trauma at high loading rates. At the macroscopic level increasing strain rates cause an increase in failure stress and modulus, but the mechanism for this strain rate dependency is not known. Here we investigate the nano scale mechanical property changes of human ligament using mechanical testing combined with synchrotron X-ray diffraction. With increasing strain rate, we observe a significant increase in fibril modulus and a reduction of fibril to tissue strain ratio, revealing that tissue-level stiffening is mainly due to the stiffening of collagen fibrils. Further, we show that the reduction in fibril deformation at higher strain rates is due to reduced molecular strain and fibrillar gaps, and is associated with rapid disruption of matrix-fibril bonding. This reduction in number of interfibrillar cross-links explains the changes in fibril strain; this is verified through computational modelling.
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Affiliation(s)
- Angelo Karunaratne
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK
- Department of Mechanical Engineering, University of Moratuwa, Moratuwa, Sri Lanka
| | - Simin Li
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK
- Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, UK
| | - Anthony M J Bull
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
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Georgiadis M, Müller R, Schneider P. Techniques to assess bone ultrastructure organization: orientation and arrangement of mineralized collagen fibrils. J R Soc Interface 2017; 13:rsif.2016.0088. [PMID: 27335222 DOI: 10.1098/rsif.2016.0088] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 05/18/2016] [Indexed: 12/13/2022] Open
Abstract
Bone's remarkable mechanical properties are a result of its hierarchical structure. The mineralized collagen fibrils, made up of collagen fibrils and crystal platelets, are bone's building blocks at an ultrastructural level. The organization of bone's ultrastructure with respect to the orientation and arrangement of mineralized collagen fibrils has been the matter of numerous studies based on a variety of imaging techniques in the past decades. These techniques either exploit physical principles, such as polarization, diffraction or scattering to examine bone ultrastructure orientation and arrangement, or directly image the fibrils at the sub-micrometre scale. They make use of diverse probes such as visible light, X-rays and electrons at different scales, from centimetres down to nanometres. They allow imaging of bone sections or surfaces in two dimensions or investigating bone tissue truly in three dimensions, in vivo or ex vivo, and sometimes in combination with in situ mechanical experiments. The purpose of this review is to summarize and discuss this broad range of imaging techniques and the different modalities of their use, in order to discuss their advantages and limitations for the assessment of bone ultrastructure organization with respect to the orientation and arrangement of mineralized collagen fibrils.
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Affiliation(s)
| | - Ralph Müller
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland
| | - Philipp Schneider
- Institute for Biomechanics, ETH Zurich, Zurich, Switzerland Bioengineering Science Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
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Abstract
Bone is a complex hierarchical structure, and its principal function is to resist mechanical forces and fracture. Bone strength depends not only on the quantity of bone tissue but also on the shape and hierarchical structure. The hierarchical levels are interrelated, especially the micro-architecture, collagen and mineral components; hence, analysis of their specific roles in bone strength and stiffness is difficult. Synchrotron imaging technologies including micro-CT and small/wide angle X-ray scattering/diffraction are becoming increasingly popular for studying bone because the images can resolve deformations in the micro-architecture and collagen-mineral matrix under in situ mechanical loading. Synchrotron cannot be directly applied in vivo due to the high radiation dose but will allow researchers to carry out systematic multifaceted studies of bone ex vivo. Identifying characteristics of aging and disease will underpin future efforts to generate novel devices and interventional therapies for assessing and promoting healthy aging. With our own research work as examples, this paper introduces how synchrotron imaging technology can be used with in situ testing in bone research.
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Affiliation(s)
- Shaocheng Ma
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ UK
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR UK
| | - Oliver Boughton
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR UK
| | - Angelo Karunaratne
- Department of Mechanical Engineering, Faculty of Engineering, University of Moratuwa, Moratuwa, 10400 Sri Lanka
| | - Andi Jin
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ UK
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR UK
| | - Justin Cobb
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR UK
| | - Ulrich Hansen
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ UK
| | - Richard Abel
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR UK
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Spiesz EM, Zysset PK. Structure–mechanics relationships in mineralized tendons. J Mech Behav Biomed Mater 2015; 52:72-84. [DOI: 10.1016/j.jmbbm.2015.03.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Revised: 03/19/2015] [Accepted: 03/23/2015] [Indexed: 01/07/2023]
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Bonner TJ, Newell N, Karunaratne A, Pullen AD, Amis AA, M J Bull A, Masouros SD. Strain-rate sensitivity of the lateral collateral ligament of the knee. J Mech Behav Biomed Mater 2014; 41:261-70. [PMID: 25086777 DOI: 10.1016/j.jmbbm.2014.07.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 06/28/2014] [Accepted: 07/01/2014] [Indexed: 02/04/2023]
Abstract
The material properties of ligaments are not well characterized at rates of deformation that occur during high-speed injuries. The aim of this study was to measure the material properties of lateral collateral ligament of the porcine stifle joint in a uniaxial tension model through strain rates in the range from 0.01 to 100/s. Failure strain, tensile modulus and failure stress were calculated. Across the range of strain rates, tensile modulus increased from 288 to 905 MPa and failure stress increased from 39.9 to 77.3 MPa. The strain-rate sensitivity of the material properties decreased as deformation rates increased, and reached a limit at approximately 1/s, beyond which there was no further significant change. In addition, time resolved microfocus small angle X-ray scattering was used to measure the effective fibril modulus (stress/fibril strain) and fibril to tissue strain ratio. The nanoscale data suggest that the contribution of the collagen fibrils towards the observed tissue-level deformation of ligaments diminishes as the loading rate increases. These findings help to predict the patterns of limb injuries that occur at different speeds and improve computational models used to assess and develop mitigation technology.
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Affiliation(s)
- Timothy J Bonner
- The Academic Department of Military Surgery and Trauma, The Royal Centre for Defence Medicine, Birmingham B15 2SQ, UK; Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Nicolas Newell
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Angelo Karunaratne
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Andy D Pullen
- Department of Civil and Environmental Engineering, Imperial College London, London SW7 2AZ, UK
| | - Andrew A Amis
- Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK; Department of Musculoskeletal Surgery, Imperial College London, London W6 8RF, UK
| | - Anthony M J Bull
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK
| | - Spyros D Masouros
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK.
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