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Demirtas A, Taylor EA, Gludovatz B, Ritchie RO, Donnelly E, Ural A. An integrated experimental-computational framework to assess the influence of microstructure and material properties on fracture toughness in clinical specimens of human femoral cortical bone. J Mech Behav Biomed Mater 2023; 145:106034. [PMID: 37494816 DOI: 10.1016/j.jmbbm.2023.106034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 06/08/2023] [Accepted: 07/16/2023] [Indexed: 07/28/2023]
Abstract
Microstructural and compositional changes that occur due to aging, pathological conditions, or pharmacological treatments alter cortical bone fracture resistance. However, the relative importance of these changes to the fracture resistance of cortical bone has not been quantified in detail. In this technical note, we developed an integrated experimental-computational framework utilizing human femoral cortical bone biopsies to advance the understanding of how fracture resistance of cortical bone is modulated due to modifications in its microstructure and material properties. Four human biopsy samples from individuals with varying fragility fracture history and osteoporosis treatment status were converted to finite element models incorporating specimen-specific material properties and were analyzed using fracture mechanics-based modeling. The results showed that cement line density and osteonal volume had a significant effect on crack volume. The removal of cement lines substantially increased the crack volume in the osteons and interstitial bone, representing straight crack growth, compared to models with cement lines due to the lack of crack deflection in the models without cement lines. Crack volume in the osteons and interstitial bone increased when mean elastic modulus and ultimate strength increased and mean fracture toughness decreased. Crack volume in the osteons and interstitial bone was reduced when material property heterogeneity was incorporated in the models. Although both the microstructure and the heterogeneity of the material properties of the cortical bone independently increased the fracture toughness, the relative contribution of the microstructure was more significant. The integrated experimental-computational framework developed here can identify the most critical microscale features of cortical bone modulated by pathological processes or pharmacological treatments that drive changes in fracture resistance and improve our understanding of the relative influence of microstructure and material properties on fracture resistance of cortical bone.
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Affiliation(s)
- Ahmet Demirtas
- Department of Mechanical Engineering, Villanova University, Villanova, PA, USA
| | - Erik A Taylor
- Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA
| | - Bernd Gludovatz
- School of Mechanical and Manufacturing Engineering, University of New South Wales (UNSW Sydney), Sydney, NSW, 2052, Australia
| | - Robert O Ritchie
- Department of Materials Science and Engineering, University of California, Berkeley, CA, 94720, USA
| | - Eve Donnelly
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA; Musculoskeletal Integrity Program, Weill Cornell Medicine, Research Institute, Hospital for Special Surgery, New York City, NY, USA
| | - Ani Ural
- Department of Mechanical Engineering, Villanova University, Villanova, PA, USA.
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Stavri R, Tay T, Wiles CC, Di Federico E, Boughton O, Ma S, Karunaratne A, Churchwell JH, Bhattacharya R, Terrill NJ, Cobb JP, Hansen U, Abel RL. A Cross-Sectional Study of Bone Nanomechanics in Hip Fracture and Aging. Life (Basel) 2023; 13:1378. [PMID: 37374160 DOI: 10.3390/life13061378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 05/07/2023] [Accepted: 05/23/2023] [Indexed: 06/29/2023] Open
Abstract
Bone mechanics is well understood at every length scale except the nano-level. We aimed to investigate the relationship between bone nanoscale and tissue-level mechanics experimentally. We tested two hypotheses: (1) nanoscale strains were lower in hip fracture patients versus controls, and (2) nanoscale mineral and fibril strains were inversely correlated with aging and fracture. A cross-sectional sample of trabecular bone sections was prepared from the proximal femora of two human donor groups (aged 44-94 years): an aging non-fracture control group (n = 17) and a hip-fracture group (n = 20). Tissue, fibril, and mineral strain were measured simultaneously using synchrotron X-ray diffraction during tensile load to failure, then compared between groups using unpaired t-tests and correlated with age using Pearson's correlation. Controls exhibited significantly greater peak tissue, mineral, and fibril strains than the hip fracture (all p < 0.05). Age was associated with a decrease in peak tissue (p = 0.099) and mineral (p = 0.004) strain, but not fibril strain (p = 0.260). Overall, hip fracture and aging were associated with changes in the nanoscale strain that are reflected at the tissue level. Data must be interpreted within the limitations of the observational cross-sectional study design, so we propose two new hypotheses on the importance of nanomechanics. (1) Hip fracture risk is increased by low tissue strain, which can be caused by low collagen or mineral strain. (2) Age-related loss of tissue strain is dependent on the loss of mineral but not fibril strain. Novel insights into bone nano- and tissue-level mechanics could provide a platform for the development of bone health diagnostics and interventions based on failure mechanisms from the nanoscale up.
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Affiliation(s)
- Richard Stavri
- 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
- Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Erica Di Federico
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London SW7 2AZ, UK
| | - Oliver Boughton
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London W6 8PR, UK
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London SW7 2AZ, UK
| | - Shaocheng Ma
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London SW7 2AZ, UK
| | - Angelo Karunaratne
- Department of Mechanical Engineering, Faculty of Engineering, University of Moratuwa, Moratuwa 10400, Sri Lanka
| | - John H Churchwell
- Department of Medical Physics and Biomedical Engineering, University College London, London WCIE 6BT, UK
| | - Rajarshi Bhattacharya
- St. Mary's Hospital, Northwest London Major Trauma Centre, Imperial College London, London W2 1NY, UK
| | - Nicholas J Terrill
- Diamond Light Source Ltd., 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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Bonicelli A, Tay T, Cobb JP, Boughton OR, Hansen U, Abel RL, Zioupos P. Association between nanoscale strains and tissue level nanoindentation properties in age-related hip-fractures. J Mech Behav Biomed Mater 2023; 138:105573. [PMID: 36525874 DOI: 10.1016/j.jmbbm.2022.105573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/21/2022] [Accepted: 11/15/2022] [Indexed: 11/24/2022]
Abstract
Measurement of the properties of bone as a material can happen in various length scales in its hierarchical and composite structure. The aim of this study was to test the tissue level properties of clinically-relevant human bone samples which were collected from donors belonging to three groups: ageing donors who suffered no fractures (Control); untreated fracture patients (Fx-Untreated) and patient who experienced hip fracture despite being treated with bisphosphonates (Fx-BisTreated). Tissue level properties were assessed by (a) nanoindentation and (b) synchrotron tensile tests (STT) where strains were measured at the 'tissue', 'fibril' and 'mineral' levels by using simultaneous Wide-angle - (WAXD) and Small angle- X-ray diffraction (SAXD). The composition was analysed by thermogravimetric analysis and material level endo- and exo-thermic reactions by differential scanning calorimetry (TGA/DSC3+). Irrespective of treatment fracture donors exhibited significantly lower tissue, fibril and mineral strain at the micro and nanoscale respectively and had a higher mineral content than controls. In nanoindentation only nanohardness was significantly greater for Controls and Fx-BisTreated versus Fx-Untreated. The other nanoindentation parameters did not vary significantly across the three groups. There was a highly significant positive correlation (p < 0.001) between organic content and tissue level strain behaviour. Overall hip-fractures were associated with lower STT nanostrains and it was behaviour measured by STT which proved to be a more effective approach for predicting fracture risk because evidently it was able to demonstrate the mechanical deficit for the bone tissue of the donors who had experienced fractures.
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Affiliation(s)
- Andrea Bonicelli
- School of Natural Sciences, University of Central Lancashire, Preston, PR1 2HE, UK; Musculoskeletal & Medicolegal Research Group, Cranfield Forensic Institute, Defence Academy of the UK, Shrivenham, Swindon, SN6 8LA, UK
| | - Tabitha Tay
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Justin P Cobb
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Oliver R Boughton
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Ulrich Hansen
- The Biomechanics Group, Department of Mechanical Engineering, Faculty of Engineering, London, SW7 2AZ, Imperial College London, London, UK
| | - Richard L Abel
- MSk Laboratory, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W6 8PR, UK
| | - Peter Zioupos
- Musculoskeletal & Medicolegal Research Group, Cranfield Forensic Institute, Defence Academy of the UK, Shrivenham, Swindon, SN6 8LA, UK.
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Bonicelli A, Kranioti EF, Xhemali B, Arnold E, Zioupos P. Assessing bone maturity: Compositional and mechanical properties of rib cortical bone at different ages. Bone 2022; 155:116265. [PMID: 34844026 DOI: 10.1016/j.bone.2021.116265] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Revised: 11/19/2021] [Accepted: 11/20/2021] [Indexed: 11/19/2022]
Abstract
Understanding what maturity entails for bone, when it arrives, and its pre- and post-maturity traits and properties are very important for understanding its evolution and physiology. There is a clear but fine distinction between the chronological age of bone (the age of its donor) and the tissue age of the bone packets it comprises at the microscopic level. Whole bone fragility changes with age due to mass and architecture effects, but so do the properties of bone at the tissue level. Tissue age and tissue-level properties are therefore increasingly attracting a great deal of attention recently. The present study investigated compositional and material changes in the hydroxyapatite crystals, the collagenous phase, changes in bone matrix composition and its nanoindentation properties and their decline with chronological age in later life. The aim was to track the age threshold at which cortical bone arrives at maturity and what happens following that threshold. To do so FTIR, DSC/TGA, XRD, nanoindentation and microindentation were used to investigate rib cortical bone material across a cohort of 86 individuals from one ethnic group with age spanning between 17 and 82 years. Results of this cross-sectional study showed a clear increase in mineral content relative to the organic and water contents across all ages. Furthermore, an increase in crystal size and consequent decrease in strain (coherence length) was detected associated with secondary mineralisation and an increase in carbonate substitution. Overall, we observe a number of modifications which contribute to a typical functional behaviour of bone showing an increase in both indentation modulus and hardness until the age of about 35 after which both of these properties decline gradually and concomitantly to other physicochemical changes and seemingly until the end of one's life.
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Affiliation(s)
- Andrea Bonicelli
- Faculty of Health and Life Sciences, Northumbria University, Newcastle Upon Tyne, UK; Musculoskeletal & Medicolegal Research Group, Cranfield University, Defence Academy of the UK, Shrivenham, UK
| | - Elena F Kranioti
- Department of Forensic Sciences, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece
| | | | - Emily Arnold
- Musculoskeletal & Medicolegal Research Group, Cranfield University, Defence Academy of the UK, Shrivenham, UK
| | - Peter Zioupos
- Musculoskeletal & Medicolegal Research Group, Cranfield University, Defence Academy of the UK, Shrivenham, UK.
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Ural A. Biomechanical mechanisms of atypical femoral fracture. J Mech Behav Biomed Mater 2021; 124:104803. [PMID: 34479108 DOI: 10.1016/j.jmbbm.2021.104803] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/12/2021] [Accepted: 08/26/2021] [Indexed: 11/26/2022]
Abstract
Antiresorptives such as bisphosphonates (BP) and denosumab are commonly used osteoporosis treatments that are effective in preventing osteoporotic fractures by suppressing bone turnover. Although these treatments reduce fracture risk, their long-term use has been associated with atypical femoral fracture (AFF), a rare potential side effect. Despite its rare occurrence, AFF has had a disproportionately significant adverse impact on society due to its severe outcomes such as loss of function and delayed healing. These severe outcomes have led to the decrease in the use and prescription of osteoporosis treatment drugs due to patient anxiety and clinician reluctance. This creates the risk for increasing osteoporotic fracture rates in the population. The existing information on the pathogenesis of AFF primarily relies on retrospective observational studies. However, these studies do not explain the underlying mechanisms that contribute to AFF, and therefore the mechanistic origins of AFF are still poorly understood. The purpose of this review is to outline the current state of knowledge of the mechanical mechanisms of AFF. The review focuses on three major potential mechanical mechanisms of AFF based on the current literature which are (1) macroscale femoral geometry which influences the stress/strain distribution in the femur under loading; (2) bone matrix composition, potentially altered by long-term remodeling suppression by BPs, which directly influences the material properties of bone and its mechanical behavior; and (3) microstructure, potentially altered by long-term remodeling suppression by BPs, which impacts fracture resistance through interaction with crack propagation. In addition, this review presents the critical knowledge gaps in understanding AFF and also discusses approaches to closing the knowledge gap in understanding the underlying mechanisms of AFF.
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Affiliation(s)
- Ani Ural
- Department of Mechanical Engineering, Villanova University, 800 Lancaster Avenue, Villanova, PA, 19085, USA.
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Abel RL, Stavri R, Gray M, Hansen U. Clinical Importance of Bone Matrix Damage Mechanisms for Fracture Prevention. Curr Osteoporos Rep 2021; 19:318-326. [PMID: 33876386 PMCID: PMC8310512 DOI: 10.1007/s11914-021-00678-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/17/2021] [Indexed: 01/23/2023]
Abstract
PURPOSE OF REVIEW Bone matrix exhibits great complexity in its composition, structure and mechanics. Here, we provide a review of recent research articles and appraise the evidence that bone matrix quality is clinically important and possibly targetable for fracture prevention. RECENT FINDINGS Deformation of mineralised collagen fibrils determines bone fracture mechanics. Slipping and separation at the mineral-fibril and fibril-fibril interfaces, respectively, are the structural mechanisms for plastic deformation and microcrack nucleation. Existing technologies for assessing bone tissue in vivo cannot measure matrix structure or fracture mechanics but have shown limited use in clinical settings for identifying fragility or following treatment outcomes based on composition. Matrix is biomechanically and clinically important, but the knowledge has not translated into clinical practice. The structural mechanisms by which a load is transferred from mineralised collagen fibrils to the whole bone via microcracking have been proven too complex to measure in vivo. The mineral-fibril or fibril-fibril interfaces might be suitable targets for diagnosing fragility or delivering molecules that reduce fracture risk by strengthening the mineral bonds while maintaining flexibility in the fibrils.
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Affiliation(s)
- Richard L Abel
- MSk Laboratory, Sir Michael Uren Hub, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W12 0BZ, UK.
| | - Richard Stavri
- MSk Laboratory, Sir Michael Uren Hub, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W12 0BZ, UK
| | - Marena Gray
- MSk Laboratory, Sir Michael Uren Hub, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, W12 0BZ, UK
| | - Ulrich Hansen
- Department of Mechanical Engineering, Faculty of Engineering, Imperial College London, London, SW7 2AZ, UK
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Tavana S, Clark JN, Newell N, Calder JD, Hansen U. In Vivo Deformation and Strain Measurements in Human Bone Using Digital Volume Correlation (DVC) and 3T Clinical MRI. MATERIALS 2020; 13:ma13235354. [PMID: 33255848 PMCID: PMC7728341 DOI: 10.3390/ma13235354] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 11/20/2020] [Accepted: 11/23/2020] [Indexed: 12/15/2022]
Abstract
Strains within bone play an important role in the remodelling process and the mechanisms of fracture. The ability to assess these strains in vivo can provide clinically relevant information regarding bone health, injury risk, and can also be used to optimise treatments. In vivo bone strains have been investigated using multiple experimental techniques, but none have quantified 3D strains using non-invasive techniques. Digital volume correlation based on clinical MRI (DVC-MRI) is a non-invasive technique that has the potential to achieve this. However, before it can be implemented, uncertainties associated with the measurements must be quantified. Here, DVC-MRI was evaluated to assess its potential to measure in vivo strains in the talus. A zero-strain test (two repeated unloaded scans) was conducted using three MRI sequences, and three DVC approaches to quantify errors and to establish optimal settings. With optimal settings, strains could be measured with a precision of 200 με and accuracy of 480 με for a spatial resolution of 7.5 mm, and a precision of 133 με and accuracy of 251 με for a spatial resolution of 10 mm. These results demonstrate that this technique has the potential to measure relevant levels of in vivo bone strain and to be used for a range of clinical applications.
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Affiliation(s)
- Saman Tavana
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; (J.N.C.); (N.N.)
- Correspondence: (S.T.); (U.H.); Tel.: +44-(0)20-7594-7061 (U.H.)
| | - Jeffrey N. Clark
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; (J.N.C.); (N.N.)
| | - Nicolas Newell
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; (J.N.C.); (N.N.)
| | - James D. Calder
- Department of Bioengineering, Imperial College London, London SW7 2AZ, UK;
- Fortius Clinic, 17 Fitzhardinge St, London W1H 6EQ, UK
| | - Ulrich Hansen
- Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK; (J.N.C.); (N.N.)
- Correspondence: (S.T.); (U.H.); Tel.: +44-(0)20-7594-7061 (U.H.)
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