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Jia T, Guines D, Gordin DM, Leotoing L, Gloriant T. Finite element analysis of a low modulus Ti-20Zr-3Mo-3Sn alloy designed to reduce the stress shielding effect of a hip prosthesis. J Mech Behav Biomed Mater 2024; 157:106640. [PMID: 38917558 DOI: 10.1016/j.jmbbm.2024.106640] [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: 02/28/2024] [Revised: 06/17/2024] [Accepted: 06/19/2024] [Indexed: 06/27/2024]
Abstract
After total hip arthroplasty, the stress shielding effect can occur due to the difference of stiffness between the metallic alloy of the stems and the host bone, which may cause a proximal bone loss. To overcome this problem, a low-modulus metastable β Ti-20Zr-3Mo-3Sn alloy composition has recently been designed to be potentially used for the cementless femoral hip stems. After having verified experimentally that the β alloy has a low modulus of around 50 GPa, a finite element analysis was performed on a Ti-20Zr-3Mo-3Sn alloy hip prosthesis model to evaluate the influence of a reduced modulus on stress shielding and stress fields in both stem and bone compared with the medical grade Ti-6Al-4V alloy whose elastic modulus reached 110 GPa. Our results show that the Ti-20Zr-3Mo-3Sn stem with low elastic modulus can effectively reduce the total stress shielding by 45.5% compared to the common Ti-6Al-4V prosthesis. Moreover, it is highlighted that the material elasticity affects the stress distribution in the implant, especially near the bone-stem interfaces.
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Affiliation(s)
- Tianyu Jia
- University of Rennes, INSA Rennes, CNRS UMR 6226 ISCR, 35000, Rennes, France
| | - Dominique Guines
- University of Rennes, INSA Rennes, LGCGM, EA 3913, 35000, Rennes, France
| | | | - Lionel Leotoing
- University of Rennes, INSA Rennes, LGCGM, EA 3913, 35000, Rennes, France
| | - Thierry Gloriant
- University of Rennes, INSA Rennes, CNRS UMR 6226 ISCR, 35000, Rennes, France.
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Baleani M, Erani P, Acciaioli A, Schileo E. Tensile Yield Strain of Human Cortical Bone from the Femoral Diaphysis Is Constant among Healthy Adults and across the Anatomical Quadrants. Bioengineering (Basel) 2024; 11:395. [PMID: 38671816 PMCID: PMC11048186 DOI: 10.3390/bioengineering11040395] [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: 01/09/2024] [Revised: 04/12/2024] [Accepted: 04/16/2024] [Indexed: 04/28/2024] Open
Abstract
The literature suggests that the yield strain of cortical bone is invariant to its stiffness (elastic modulus) and strength (yield stress). However, data about intra-individual variations, e.g., the influence of different collagen/mineral organisations observed in bone aspects withstanding different habitual loads, are lacking. The hypothesis that the yield strain of human cortical bone tissue, retrieved from femoral diaphyseal quadrants subjected to different habitual loads, is invariant was tested. Four flat dumbbell-shaped specimens were machined from each quadrant of the proximal femoral diaphysis of five adult donors for a total of 80 specimens. Two extensometers attached to the narrow specimen region were used to measure deformation during monotonic tensile testing. The elastic modulus (linear part of the stress-strain curve) and yield strain/stress at a 0.2% offset were obtained. Elastic modulus and yield stress values were, respectively, in the range of 12.2-20.5 GPa and 75.9-136.6 MPa and exhibited a positive linear correlation. All yield strain values were in the narrow range of 0.77-0.87%, regardless of the stiffness and strength of the tissue and the anatomical quadrant. In summary, the results corroborate the hypothesis that tensile yield strain in cortical bone is invariant, irrespective also of the anatomical quadrant. The mean yield strain value found in this study is similar to what was reported by inter-species and evolution studies but slightly higher than previous reports in humans, possibly because of the younger age of our subjects. Further investigations are needed to elucidate a possible dependence of yield strain on age.
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Affiliation(s)
- Massimiliano Baleani
- Laboratorio di Tecnologia Medica, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy; (P.E.); (A.A.)
| | - Paolo Erani
- Laboratorio di Tecnologia Medica, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy; (P.E.); (A.A.)
| | - Alice Acciaioli
- Laboratorio di Tecnologia Medica, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy; (P.E.); (A.A.)
| | - Enrico Schileo
- Laboratorio di Bioingegneria Computazionale, IRCCS Istituto Ortopedico Rizzoli, 40136 Bologna, Italy;
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Galteri G, Palanca M, Alesi D, Zaffagnini S, Morellato K, Gruppioni E, Cristofolini L. Reliable in vitro method for the evaluation of the primary stability and load transfer of transfemoral prostheses for osseointegrated implantation. Front Bioeng Biotechnol 2024; 12:1360208. [PMID: 38576443 PMCID: PMC10991734 DOI: 10.3389/fbioe.2024.1360208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Accepted: 03/08/2024] [Indexed: 04/06/2024] Open
Abstract
Osseointegrated transfemoral prostheses experience aseptic complications with an incidence between 3% and 30%. The main aseptic risks are implant loosening, adverse bone remodeling, and post-operative periprosthetic fractures. Implant loosening can either be due to a lack of initial (primary) stability of the implant, which hinders bone ingrowth and therefore prevents secondary stability, or, in the long-term, to the progressive resorption of the periprosthetic bone. Post-operative periprosthetic fractures are most often caused by stress concentrations. A method to simultaneously evaluate the primary stability and the load transfer is currently missing. Furthermore, the measurement errors are seldom reported in the literature. In this study a method to reliably quantify the bone implant interaction of osseointegrated transfemoral prostheses in terms of primary stability and load transfer was developed, and its precision was quantified. Micromotions between the prosthesis and the host bone and the strains on the cortical bone were measured on five human cadaveric femurs with a typical commercial osseointegrated implant. To detect the primary stability of the implant and the load transfer, cyclic loads were applied, simulating the peak load during gait. Digital Image Correlation was used to measure displacements and bone strains simultaneously throughout the test. Permanent migrations and inducible micromotions were measured (three translations and three rotations), while, on the same specimen, the full-field strain distribution on the bone surface was measured. The repeatability tests showed that the devised method had an intra-specimen variability smaller than 6 μm for the translation, 0.02 degrees for the rotations, and smaller than 60 microstrain for the strain distribution. The inter-specimen variability was larger than the intra-specimen variability due to the natural differences between femurs. Altogether, the measurement uncertainties (intrinsic measurement errors, intra-specimen repeatability and inter-specimen variability) were smaller than critical levels of biomarkers for adverse remodelling and aseptic loosening, thus allowing to discriminate between stable and unstable implants, and to detect critical strain magnitudes in the host bone. In conclusion, this work showed that it is possible to measure the primary stability and the load transfer of an osseointegrated transfemoral prosthesis in a reliable way using a combination of mechanical testing and DIC.
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Affiliation(s)
- Giulia Galteri
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | - Marco Palanca
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum-University of Bologna, Bologna, Italy
| | | | | | | | | | - Luca Cristofolini
- Department of Industrial Engineering, School of Engineering and Architecture, Alma Mater Studiorum-University of Bologna, Bologna, Italy
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Cen H, Gong H, Liu H, Jia S, Wu X, Fan Y. A Comparative Study on the Multiscale Mechanical Responses of Human Femoral Neck Between the Young and the Elderly Using Finite Element Method. Front Bioeng Biotechnol 2022; 10:893337. [PMID: 35600894 PMCID: PMC9117745 DOI: 10.3389/fbioe.2022.893337] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 04/14/2022] [Indexed: 11/13/2022] Open
Abstract
Background: Femoral neck fracture (FNF) is the most serious bone disease in the elderly population. The multiscale mechanical response is a key to predicting the strength of the femoral neck, assessing the risk of FNF, and exploring the role of mechanosensation and mechanotransmission in bone remodeling, especially in the context of aging bone.Methods: Multiscale finite element (FE) models of the proximal femur for both young and elderly people were developed. The models included organ scale (proximal femur), tissue scale (cortical bone), tissue element scale (osteon), and cell scale [osteocyte lacuna-canalicular network (LCN) and extracellular matrix (ECM), OLCEM]. The mechanical responses of cortical bone and osteocytes in the mid-femoral neck and the differences in mechanical responses between these two scales were investigated.Results: The mechanical responses of cortical bone and osteocyte showed significant differences between the elderly and the young. The minimum principal strains and mean SEDs of cortical bone in the elderly were 2.067–4.708 times and 3.093–14.385 times of the values in the young, respectively; the minimum principal strains and mean SEDs of osteocyte in the elderly were 1.497–3.246 times and 3.044–12 times of the values in the young, respectively; the amplification factors of minimum principal strain in the inferior (Inf), anterior (Ant), and posterior (Post) quadrants in the young were 1.241–1.804 times of the values in the elderly, but the amplification factor of minimum principal strain in the superior (Sup) quadrant was 87.4% of the value in the elderly; the amplification factors of mean SED in the young were 1.124–9.637 times of the values in the elderly.Conclusion: The mass and bone mineral density (BMD) of cortical bone in the femoral neck is closely related to the mechanical response of osteocytes, which provides a new idea for improving cortical bone quality. Perhaps cortical bone quality could be improved by stimulating osteocytes. Quadrantal differences of bone quality in the mid-femoral neck should be considered to improve fracture risk prediction in the future.
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Affiliation(s)
- Haipeng Cen
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - He Gong
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
- *Correspondence: He Gong,
| | - Haibo Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Shaowei Jia
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Xiaodan Wu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Yubo Fan
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
- School of Engineering Medicine, Beihang University, Beijing, China
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Martelli S. The effect of age and initial compression on the force relaxation response of the femur in elderly women. ROYAL SOCIETY OPEN SCIENCE 2022; 9:220301. [PMID: 35592757 PMCID: PMC9066301 DOI: 10.1098/rsos.220301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 03/29/2022] [Indexed: 06/15/2023]
Abstract
The effect of force amount, age, body weight and bone mineral density (BMD) on the femur's force relaxation response was analysed for 12 donors (age: 56-91 years). BMD and fracture load, F L, were estimated from clinical CT images. The 30 min force relaxation was obtained using a constant compression generating an initial force F 0 between 7% and 78% of F L. The stretched decay function (F(t) = A × e (-t/τ)β ) proposed earlier for bone tissue was fitted to the data and analysed using robust linear regression. The relaxation function fitted well to all the recordings (R 2 = 0.99). The relative initial force was bilinearly associated (R 2 = 0.83) to the shape factor, β, and the characteristic time, τ, when F 0/F L was less than 0.4, although β was no longer associated with F 0/F L by pooling all the data. The characteristic time τ increased with age (R 2 = 0.37, p = 0.03) explaining 35% of the variation of τ in the entire dataset. In conclusion, the relative initial force mostly determines the femur's force relaxation response, although the early relaxation response under subcritical loading is variable, possibly due to damage occurring at subcritical loading levels.
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Affiliation(s)
- Saulo Martelli
- Centre for Biomedical Technologies, School of Mechanical, Medical and Process Engineering, Queensland University of Technology (QUT), Brisbane, Australia
- Medical Device Research Institute, College of Science and Engineering, Flinders University, Tonsley SA, Australia
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Real-time replication of three-dimensional and time-varying physiological loading cycles for bone and implant testing: A novel protocol demonstrated for the proximal human femur while walking. J Mech Behav Biomed Mater 2021; 124:104817. [PMID: 34536802 DOI: 10.1016/j.jmbbm.2021.104817] [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: 03/04/2021] [Revised: 08/26/2021] [Accepted: 09/03/2021] [Indexed: 11/24/2022]
Abstract
In vitro real-time replication of three-dimensional, time-varying load profiles acting on human bones during physical activity can advance bone and implant testing protocols. This study aimed to develop a novel protocol for applying the three-dimensional, time-varying hip contact force while walking to a human femur specimen. The target force profile was obtained from the literature. A proximal femur from an elderly female donor was instrumented using ten rosette strain gages and tested using a custom-made hexapod robot. A load-control algorithm determined the robot position generating the target force at low frequency (0.0004 Hz). Five cycles of the robot position were played back at five intermediate frequencies up to real-time (0.04, 0.08, 0.16, 0.4, and 0.8 Hz). The hip reaction force, the length of the actuators (position), and cortical strains were compared. The error in the load-control force was 0.3 ± 4.2 N (mean ± SD). The last three force, position, and strain cycles varied by less than 1.1% for every frequency analyzed. Across frequencies, the force increased by 28% at 0.8 Hz as a logarithmic function of frequency (R2 = 0.98). The position and strain error linearly increased with frequency up to 0.4 Hz. The median position error and the interquartile range of the strain error reached 15% and 13% at 0.8 Hz. Changes of force and cortical strain at increasing frequencies were linearly related (R2 = 0.99). Therefore, the protocol developed can provide repeatable three-dimensional time-varying load profiles, although the comparison of the specimen deformation obtained across frequencies should be considered with care, particularly in the higher frequency range. This information supports the design of dynamic tests of bone and implants.
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Franceschini M, Barbera LL, Anticonome A, Ottardi C, Tanaka A, Villa T. Periprosthetic femoral fractures in sideways fall configuration: comparative numerical analysis of the influence of femoral stem design. Hip Int 2020; 30:86-93. [PMID: 33267694 DOI: 10.1177/1120700020971312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
INTRODUCTION The aim of this study was to investigate the mechanisms of periprosthetic fractures occurring as a result of a sideways fall in total hip arthroplasty patients, and to compare the predictions of numerical models in terms of load distribution on the implanted femur with clinical data. MATERIALS AND METHODS 3 numerical models were built: 1 for intact femur and 2 for implanted femur with a straight stem (resembling PBF, Permedica) and with an anatomical stem (resembling ABG II, Stryker). 4 loading configurations were simulated; 1 simulates a vertical load, and 3 simulate a fall with impact on the greater trochanter in different directions. Stress state calculated in the implanted femur was compared for the 2 models with reference to the intact case. These were compared with clinical data collected at a single centre (Istituto Ortopedico Gaetano Pini, Milan, Italy) where 41 patients were investigated after periprosthetic fracture: 26 patients had a straight uncemented stem and 15 an anatomical uncemented stem. RESULTS The maximum calculated strain in compression in the case of ABG II implanted femur was 2 times higher than in the presence of PBF stem in the vertical loading configuration. For configurations of sideways fall, in both models, there was a progressive increase of stress state in the bone with increasing angle. Simulations of sideways fall elicited results in accordance with clinical observations: due to the peculiar stem design and consequent state of stress in the bone, anatomical stems seem to induce trochanteric fractures more frequently, while for straight stems type B fractures are more likely to occur. CONCLUSIONS Clinical findings confirmed numerical model predictions: stem design seems to highly influence distribution of stress in the bone and consequent localisation of the fracture site.
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Affiliation(s)
| | - Luigi La Barbera
- LaBS, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic of Milan, Italy
| | - Alberto Anticonome
- LaBS, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic of Milan, Italy
| | - Claudia Ottardi
- LaBS, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic of Milan, Italy
| | - Atsuki Tanaka
- LaBS, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic of Milan, Italy
| | - Tomaso Villa
- LaBS, Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Polytechnic of Milan, Italy
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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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Schileo E, Pitocchi J, Falcinelli C, Taddei F. Cortical bone mapping improves finite element strain prediction accuracy at the proximal femur. Bone 2020; 136:115348. [PMID: 32240847 DOI: 10.1016/j.bone.2020.115348] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Revised: 03/17/2020] [Accepted: 03/27/2020] [Indexed: 11/28/2022]
Abstract
Despite evidence of the biomechanical role of cortical bone, current state of the art finite element models of the proximal femur built from clinical CT data lack a subject-specific representation of the bone cortex. Our main research hypothesis is that the subject-specific modelling of cortical bone layer from CT images, through a deconvolution procedure known as Cortical Bone Mapping (CBM, validated for cortical thickness and density estimates) can improve the accuracy of CT-based FE models of the proximal femur, currently limited by partial volume artefacts. Our secondary hypothesis is that a careful choice of cortical-specific density-elasticity relationship may improve model accuracy. We therefore: (i) implemented a procedure to include subject-specific CBM estimates of both cortical thickness and density in CT-based FE models. (ii) defined alternative models that included CBM estimates and featured a cortical-specific or an independently optimised density-elasticity relationship. (iii) tested our hypotheses in terms of elastic strain estimates and failure load and location prediction, by comparing with a published cohort of 14 femurs, where strain and strength in stance and fall loading configuration were experimentally measured, and estimated through reference FE models that did not explicitly model the cortical compartment. Our findings support the main hypothesis: an explicit modelling of the proximal femur cortical bone layer including CBM estimates of cortical bone thickness and density increased the FE strains prediction, mostly by reducing peak errors (average error reduced by 30%, maximum error and 95th percentile of error distribution halved) and especially when focusing on the femoral neck locations (all error metrics at least halved). We instead rejected the secondary hypothesis: changes in cortical density-elasticity relationship could not improve validation performances. From these improved baseline strain estimates, further work is needed to achieve accurate strength predictions, as models incorporating cortical thickness and density produced worse estimates of failure load and equivalent estimates of failure location when compared to reference models. In summary, we recommend including local estimates of cortical thickness and density in FE models to estimate bone strains in physiological conditions, and especially when designing exercise studies to promote bone strength.
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Affiliation(s)
- Enrico Schileo
- Bioengineering and Computing Laboratory, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy.
| | - Jonathan Pitocchi
- Materialise N.V., Heverlee, Belgium; Multiscale in Mechanical and Biological Engineering (M2BE), University of Zaragoza, Zaragoza, Spain; Biomechanics Section, KU Leuven, Leuven, Belgium
| | | | - Fulvia Taddei
- Bioengineering and Computing Laboratory, IRCCS Istituto Ortopedico Rizzoli, Bologna, Italy
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Floerkemeier T, Arokiasamy R, Budde S, Hurschler C, Windhagen H, von Lewinski G, Gronewold J. Is the strain pattern of conventional stems negatively affected by a previously short stem THA? An experimental study in cadavaric bone. Technol Health Care 2020; 29:323-331. [PMID: 32568130 DOI: 10.3233/thc-191940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND A short stem hip arthroplasty can be revised in many cases using a conventional stem. Furthermore, in some cases the implantation of a short stem is intended, but intraoperatively reasons may lead to the decision to implant a conventional stem after previous preparation of a short stem. OBJECTIVE In both cases it is questionable if the anchorage of a conventional stem is negatively affected by the previous preparation of a short stem. In clinical practice mid- or long-term follow up for these special cases hardly exist. METHODS The strain patterns for the conventional Bicontact stem in primary implantation and after preparation of the proximal femur for a METHA short stem were tested biomechanically in three pairs of cadaveric femora. RESULTS The strain patterns for the conventional Bicontact after preparation of the METHA short stem were similar to conditions after testing the conventional stem in primary conditions. CONCLUSIONS These data lead to the consequence that in clinical practise the implantation of a conventional stem after preparation of a short stem and even after revision of a short stem is possible without increased risk of loosening or long-term stress-shielding.
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Affiliation(s)
- Thilo Floerkemeier
- Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany.,go:h Gelenkchirurgie Orthopädie Hannover, Hannover, Germany
| | - Romy Arokiasamy
- Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany
| | - Stefan Budde
- Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany
| | - Christof Hurschler
- Biomechanics and Biomaterials Laboratory, Hannover Medical School, Hannover, Germany
| | - Henning Windhagen
- Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany
| | | | - Jens Gronewold
- Department of Orthopaedic Surgery, Hannover Medical School, Hannover, Germany
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Tang T, Cripton PA, Guy P, McKay HA, Wang R. Clinical hip fracture is accompanied by compression induced failure in the superior cortex of the femoral neck. Bone 2018; 108:121-131. [PMID: 29277713 DOI: 10.1016/j.bone.2017.12.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 11/22/2017] [Accepted: 12/20/2017] [Indexed: 10/18/2022]
Abstract
Hip fractures pose a major health problem throughout the world due to their devastating impact. Current theories for why these injuries are so prevalent in the elderly point to an increased propensity to fall and decreases in bone mass with ageing. However, the fracture mechanisms, particularly the stress and strain conditions leading to bone failure at the hip remain unclear. Here, we directly examined the cortical bone from clinical intra-capsular hip fractures at a microscopic level, and found strong evidence of compression induced failure in the superior cortex. A total of 143 sections obtained from 24 femoral neck samples that were retrieved from 24 fracturing patients at surgery were examined using laser scanning confocal microscopy (LSCM) after fluorescein staining. The stained microcracks showed significantly higher density in the superior cortex than in the inferior cortex, indicating a greater magnitude of strain in the superior femoral neck during the failure-associated deformation and fracture process. The predominant stress state for each section was reconstructed based on the unique correlation between the microcrack pattern and the stress state. Specifically, we found clear evidence of longitudinal compression and buckling as the primary failure mechanisms in the superior cortex. These findings demonstrate the importance of microcrack analysis in studying clinical hip fractures, and point to the central role of the superior cortex failure as an important aspect of the failure initiation in clinical intra-capsular hip fractures.
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Affiliation(s)
- Tengteng Tang
- Department of Materials Engineering, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility, Vancouver, BC, Canada
| | - Peter A Cripton
- Department of Mechanical Engineering, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility, Vancouver, BC, Canada; International Collaboration On Repair Discoveries, Vancouver, BC, Canada
| | - Pierre Guy
- Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility, Vancouver, BC, Canada
| | - Heather A McKay
- Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility, Vancouver, BC, Canada
| | - Rizhi Wang
- Department of Materials Engineering, University of British Columbia, Vancouver, BC, Canada; Centre for Hip Health and Mobility, Vancouver, BC, Canada.
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Full-field strain distribution in multi-vertebra spine segments: An in vitro application of digital image correlation. Med Eng Phys 2018; 52:76-83. [DOI: 10.1016/j.medengphy.2017.11.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 11/08/2017] [Accepted: 11/22/2017] [Indexed: 11/17/2022]
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Danesi V, Erani P, Brandolini N, Juszczyk MM, Cristofolini L. Effect of the In Vitro Boundary Conditions on the Surface Strain Experienced by the Vertebral Body in the Elastic Regime. J Biomech Eng 2017; 138:2543312. [PMID: 27496676 DOI: 10.1115/1.4034383] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Indexed: 11/08/2022]
Abstract
The vertebral strength and strain can be assessed in vitro by both using isolated vertebrae and sets of three adjacent vertebrae (the central one is loaded through the disks). Our goal was to elucidate if testing single-vertebra-specimens in the elastic regime provides different surface strains to three-vertebrae-segments. Twelve three-vertebrae sets were extracted from thoracolumbar human spines. To measure the principal strains, the central vertebra of each segment was prepared with eight strain-gauges. The sets were tested mechanically, allowing comparison of the surface strains between the two boundary conditions: first when the same vertebra was loaded through the disks (three-vertebrae-segment) and then with the endplates embedded in cement (single-vertebra). They were all subjected to four nondestructive tests (compression, traction, torsion clockwise, and counterclockwise). The magnitude of principal strains differed significantly between the two boundary conditions. For axial loading, the largest principal strains (along vertebral axis) were significantly higher when the same vertebra was tested isolated compared to the three-vertebrae-segment. Conversely, circumferential strains decreased significantly in the single vertebrae compared to the three-vertebrae-segment, with some variations exceeding 100% of the strain magnitude, including changes from tension to compression. For torsion, the differences between boundary conditions were smaller. This study shows that, in the elastic regime, when the vertebra is loaded through a cement pot, the surface strains differ from when it is loaded through the disks. Therefore, when single vertebrae are tested, surface strain should be taken with caution.
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Lopes VM, Neto MA, Amaro AM, Roseiro LM, Paulino M. FE and experimental study on how the cortex material properties of synthetic femurs affect strain levels. Med Eng Phys 2017. [DOI: 10.1016/j.medengphy.2017.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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15
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FALCINELLI CRISTINA, SCHILEO ENRICO, BARUFFALDI FABIO, CRISTOFOLINI LUCA, TADDEI FULVIA. THE EFFECT OF COMPUTED TOMOGRAPHY CURRENT REDUCTION ON PROXIMAL FEMUR SUBJECT-SPECIFIC FINITE ELEMENT MODELS. J MECH MED BIOL 2017. [DOI: 10.1142/s0219519417500129] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Many studies have addressed the modulation of computed tomography (CT) parameters, and particularly of tube current, to obtain a good compromise between the X-ray dose to the patient and the image quality for diagnostic applications. This study aimed at evaluating the influence of dose reduction by means of tube current reduction on the CT-based subject-specific finite element (FE) modeling. To this aim, CT scans at stepwise reduced values of tube current from 180[Formula: see text]mAs to 80[Formula: see text]mAs were performed on: (i) a densitometric phantom, to quantify the changes in the calibration equation; (ii) a fresh-frozen, water submersed, human cadaver femur, to quantify changes in geometry reconstruction and material mapping from CT, as well as strain prediction accuracy, based on the in vitro strain measurements available; (iii) a fresh-frozen human cadaver thigh with soft tissues attached, to quantify FE results changes in conditions similar to those found in vivo. The results showed that the tube current reduction does not affect the 3D modeling and the femur FE analysis. Our pilot study highlights the possibility of performing CT scans with reduced dose to generate biomechanical models, although a confirmation by performing larger studies with clinical CT data is needed.
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Affiliation(s)
- CRISTINA FALCINELLI
- Laboratorio di Bioingegneria Computazionale, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
- Dipartimento di Ingegneria Civile, Università di Roma Tor Vergata, Via del Politecnico 1, 00133 Roma, Italy
| | - ENRICO SCHILEO
- Laboratorio di Bioingegneria Computazionale, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
| | - FABIO BARUFFALDI
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
| | - LUCA CRISTOFOLINI
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
- Dipartimento di Ingegneria Industriale, Università di Bologna Viale Risorgimento 2, 40136 Bologna, Italy
| | - FULVIA TADDEI
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
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Fuchs RK, Kersh ME, Carballido-Gamio J, Thompson WR, Keyak JH, Warden SJ. Physical Activity for Strengthening Fracture Prone Regions of the Proximal Femur. Curr Osteoporos Rep 2017; 15:43-52. [PMID: 28133707 PMCID: PMC5317179 DOI: 10.1007/s11914-017-0343-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE OF REVIEW Physical activity improves proximal femoral bone health; however, it remains unclear whether changes translate into a reduction in fracture risk. To enhance any fracture-protective effects of physical activity, fracture prone regions within the proximal femur need to be targeted. RECENT FINDINGS The proximal femur is designed to withstand forces in the weight-bearing direction, but less so forces associated with falls in a sideways direction. Sideways falls heighten femoral neck fracture risk by loading the relatively weak superolateral region of femoral neck. Recent studies exploring regional adaptation of the femoral neck to physical activity have identified heterogeneous adaptation, with adaptation principally occurring within inferomedial weight-bearing regions and little to no adaptation occurring in the superolateral femoral neck. There is a need to develop novel physical activities that better target and strengthen the superolateral femoral neck within the proximal femur. Design of these activities may be guided by subject-specific musculoskeletal modeling and finite-element modeling approaches.
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Affiliation(s)
- Robyn K Fuchs
- Department of Physical Therapy and Center for Translational Musculoskeletal Research, School of Health and Rehabilitation Sciences, Indiana University, 1140 W. Michigan St, Indianapolis, IN, CF-120, USA
| | - Mariana E Kersh
- Department of Mechanical Science and Engineering, College of Engineering, University of Illinois at Urbana-Champaign, Urbana-Champaign, IL, USA
| | - Julio Carballido-Gamio
- Department of Radiology, School of Medicine, University of Colorado Denver, Denver, CO, USA
| | - William R Thompson
- Department of Physical Therapy and Center for Translational Musculoskeletal Research, School of Health and Rehabilitation Sciences, Indiana University, 1140 W. Michigan St, Indianapolis, IN, CF-120, USA
| | - Joyce H Keyak
- Departments of Radiological Sciences, Mechanical and Aerospace Engineering, and Biomedical Engineering, University of California, Irvine, CA, USA
| | - Stuart J Warden
- Department of Physical Therapy and Center for Translational Musculoskeletal Research, School of Health and Rehabilitation Sciences, Indiana University, 1140 W. Michigan St, Indianapolis, IN, CF-120, USA.
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Falcinelli C, Schileo E, Pakdel A, Whyne C, Cristofolini L, Taddei F. Can CT image deblurring improve finite element predictions at the proximal femur? J Mech Behav Biomed Mater 2016; 63:337-351. [PMID: 27450036 DOI: 10.1016/j.jmbbm.2016.07.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 05/31/2016] [Accepted: 07/04/2016] [Indexed: 11/29/2022]
Abstract
The aim of this study was to determine if a CT image deblurring algorithm can improve CT-based FE modelling accuracy at the proximal femur. Experimental data (CT scans of fourteen proximal fresh-frozen cadaveric femurs, non-destructive surface strain measurements in stance and sideways fall loading configurations on all femurs, and failure loads obtained in stance for seven specimens, in sideways fall for the other seven) were taken from a recent study (Schileo et al., 2014). An estimate of the 3D Point Spread Function for each CT scan was used within a deconvolution solver to perform the deblurring. The most proximal regions of three specimens were scanned using an HRpQCT scanner and compared to the original and deblurred CT images to quantify errors in bone contour estimates and determine correlation of intensity values within the bone contours. Subject-specific FE models of the proximal femur were generated. The accuracy of deblurred FE predictions against experimental measurements was compared to the published (non-deblurred) FE results. When compared to HRpQCT, CT deblurring led to lower mean surface distances (0.31 vs. 0.49mm) and higher CT intensity correlations with respect to the original CT. All indicators of strain prediction accuracy were significantly improved in deblurred FE models, more markedly at the femoral neck (peak error reduced by 38%). Failure load prediction, based on a simple elastic limit model, was also improved in deblurred FE models, although differently for stance and sideways fall loading conditions. In stance, correlation was unchanged, but specimen-wise errors were reduced (mean error 10% vs. 15%). In sideways fall, correlation notably increased (R(2)=0.95 vs. 0.81), despite a general overestimation of failure load. In summary, the proposed CT deblurring technique yielded moderate but significant improvements in FE predictions, and may thus be considered a first step toward the improvement of CT-based FE models of the human femur.
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Affiliation(s)
- Cristina Falcinelli
- Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy.
| | - Enrico Schileo
- Bioengineering Computing Laboratory, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy
| | - Amirreza Pakdel
- Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5
| | - Cari Whyne
- Orthopaedic Biomechanics Laboratory, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, Canada M4N 3M5
| | - Luca Cristofolini
- Department of Industrial Engineering, Alma Mater Studiorum - Universita' di Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
| | - Fulvia Taddei
- Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy
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Gustafson H, Siegmund G, Cripton P. Comparison of Strain Rosettes and Digital Image Correlation for Measuring Vertebral Body Strain. J Biomech Eng 2016; 138:054501. [DOI: 10.1115/1.4032799] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2015] [Indexed: 11/08/2022]
Abstract
Strain gages are commonly used to measure bone strain, but only provide strain at a single location. Digital image correlation (DIC) is an optical technique that provides the displacement, and therefore strain, over an entire region of interest on the bone surface. This study compares vertebral body strains measured using strain gages and DIC. The anterior surfaces of 15 cadaveric porcine vertebrae were prepared with a strain rosette and a speckled paint pattern for DIC. The vertebrae were loaded in compression with a materials testing machine, and two high-resolution cameras were used to image the anterior surface of the bones. The mean noise levels for the strain rosette and DIC were 1 με and 24 με, respectively. Bland–Altman analysis was used to compare strain from the DIC and rosette (excluding 44% of trials with some evidence of strain rosette failure or debonding); the mean difference ± 2 standard deviations (SDs) was −108 με ± 702 με for the minimum (compressive) principal strain and −53 με ± 332 με for the maximum (tensile) principal strain. Although the DIC has higher noise, it avoids the relatively high risk we observed of strain gage debonding. These results can be used to develop guidelines for selecting a method to measure strain on bone.
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Affiliation(s)
- Hannah Gustafson
- Department of Mechanical Engineering, University of British Columbia, 818 West 10th Avenue, Vancouver, BC V5Z 1M9, Canada e-mail:
| | - Gunter Siegmund
- MEA Forensic Engineers & Scientists, 11-11151 Horseshoe Way, Richmond, BC V7A 4S5, Canada
- School of Kinesiology, University of British Columbia, 210-6081 University Boulevard, Vancouver, BC V6T 1Z1, Canada e-mail:
| | - Peter Cripton
- Department of Mechanical Engineering, University of British Columbia, 818 West 10th Avenue, Vancouver, BC V5Z 1M9, Canada e-mail:
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Prophylactic augmentation of the proximal femur: an investigation of two techniques. Arch Orthop Trauma Surg 2016; 136:345-51. [PMID: 26749332 DOI: 10.1007/s00402-015-2400-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Indexed: 02/09/2023]
Abstract
INTRODUCTION Osteoporotic hip fractures are an increasing problem in an ageing population. They result in high morbidity, mortality and high socioeconomic costs. For patients with poor bone quality, prophylactic augmentation of the proximal femur might be an option for fracture prevention. METHODS In two groups of paired human femora the potential of limited polymethyl-methacrylate (PMMA) augmentation (11-15 ml) in a V-shape pattern and the insertion of a proximal femur nail antirotation (PFNA) blade were investigated. The testing was carried out pair wise simulating the single leg stand. The untreated femur in each pair served as control. An axial load was applied until failure. Load displacement parameters and temperature increase during the augmentation process were recorded. RESULTS In the PMMA group no significant difference was found between the augmented and non-augmented specimen concerning load to failure (p = 0.35) and energy to failure (p = 0.9). A median temperature increase of 9.5 °C was observed in the augmented specimen. A significant correlation was found between the amount of applied PMMA and the temperature increase (Cor. Coef. = 0.82, p = 0.042). In the PFNA group, a significant decrease of load to failure and a non-significant decrease of energy to failure were observed (p = 0.037 and p = 0.075). CONCLUSION Limited V-shaped PMMA augmentation and PFNA blade insertion did not show any improvement in failure load or energy to failure. Volumes of up to 15 ml PMMA did not cause a critical surface temperature increase.
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Wille H, Ruess M, Rank E, Yosibash Z. Uncertainty quantification for personalized analyses of human proximal femurs. J Biomech 2016; 49:520-7. [PMID: 26873282 DOI: 10.1016/j.jbiomech.2015.11.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 11/07/2015] [Accepted: 11/11/2015] [Indexed: 12/01/2022]
Abstract
Computational models for the personalized analysis of human femurs contain uncertainties in bone material properties and loads, which affect the simulation results. To quantify the influence we developed a probabilistic framework based on polynomial chaos (PC) that propagates stochastic input variables through any computational model. We considered a stochastic E-ρ relationship and a stochastic hip contact force, representing realistic variability of experimental data. Their influence on the prediction of principal strains (ϵ1 and ϵ3) was quantified for one human proximal femur, including sensitivity and reliability analysis. Large variabilities in the principal strain predictions were found in the cortical shell of the femoral neck, with coefficients of variation of ≈40%. Between 60 and 80% of the variance in ϵ1 and ϵ3 are attributable to the uncertainty in the E-ρ relationship, while ≈10% are caused by the load magnitude and 5-30% by the load direction. Principal strain directions were unaffected by material and loading uncertainties. The antero-superior and medial inferior sides of the neck exhibited the largest probabilities for tensile and compression failure, however all were very small (pf<0.001). In summary, uncertainty quantification with PC has been demonstrated to efficiently and accurately describe the influence of very different stochastic inputs, which increases the credibility and explanatory power of personalized analyses of human proximal femurs.
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Affiliation(s)
- Hagen Wille
- Chair for Computation in Engineering, Technische Universität München, Munich, Germany.
| | - Martin Ruess
- Faculty of Aerospace Engineering, Delft University of Technology, Delft, Netherlands.
| | - Ernst Rank
- Chair for Computation in Engineering, Technische Universität München, Munich, Germany; Institute for Advanced Study, Technische Universität München, Munich, Germany.
| | - Zohar Yosibash
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
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Extracting accurate strain measurements in bone mechanics: A critical review of current methods. J Mech Behav Biomed Mater 2015; 50:43-54. [DOI: 10.1016/j.jmbbm.2015.06.006] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 06/01/2015] [Accepted: 06/02/2015] [Indexed: 11/19/2022]
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22
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Affiliation(s)
- Trude Basso
- Orthopedic Research Centre St. Olavs hospital Trondheim University Hospital Postbox 3250 Sluppen NO-7006 Trondheim Norway
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23
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Strain distribution in the proximal Human femur during in vitro simulated sideways fall. J Biomech 2015; 48:2130-43. [PMID: 25843261 DOI: 10.1016/j.jbiomech.2015.02.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Revised: 02/06/2015] [Accepted: 02/15/2015] [Indexed: 11/21/2022]
Abstract
This study assessed: (i) how the magnitude and direction of principal strains vary for different sideways fall loading directions; (ii) how the principal strains for a sideways fall differ from physiological loading directions; (iii) the fracture mechanism during a sideways fall. Eleven human femurs were instrumented with 16 triaxial strain gauges each. The femurs were non-destructively subjected to: (a) six loading configurations covering the range of physiological loading directions; (b) 12 configurations simulating sideways falls. The femurs were eventually fractured in a sideways fall configuration while high-speed cameras recorded the event. When the same force magnitude was applied, strains were significantly larger in a sideways fall than for physiological loading directions (principal compressive strain was 70% larger in a sideways fall). Also the compressive-to-tensile strain ratio was different: for physiological loading the largest compressive strain was only 30% larger than the largest tensile strain; but for the sideways fall, compressive strains were twice as large as the tensile strains. Principal strains during a sideways fall were nearly perpendicular to the direction of principal strains for physiological loading. In the most critical regions (medial part of the head-neck) the direction of principal strain varied by less than 9° between the different physiological loading conditions, whereas it varied by up to 17° between the sideways fall loading conditions. This was associated with a specific fracture mechanism during sideways fall, where failure initiated on the superior-lateral side (compression) followed by later failure of the medially (tension), often exhibiting a two-peak force-displacement curve.
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24
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Cristofolini L. In vitro evidence of the structural optimization of the human skeletal bones. J Biomech 2015; 48:787-96. [DOI: 10.1016/j.jbiomech.2014.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2014] [Indexed: 11/17/2022]
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25
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Poole KES, Treece GM, Gee AH, Brown JP, McClung MR, Wang A, Libanati C. Denosumab rapidly increases cortical bone in key locations of the femur: a 3D bone mapping study in women with osteoporosis. J Bone Miner Res 2015; 30:46-54. [PMID: 25088963 DOI: 10.1002/jbmr.2325] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 07/16/2014] [Accepted: 07/30/2014] [Indexed: 11/05/2022]
Abstract
Women with osteoporosis treated for 36 months with twice-yearly injections of denosumab sustained fewer hip fractures compared with placebo. Treatment might improve femoral bone at locations where fractures typically occur. To test this hypothesis, we used 3D cortical bone mapping of postmenopausal women with osteoporosis to investigate the timing and precise location of denosumab versus placebo effects in the hips. We analyzed clinical computed tomography scans from 80 female participants in FREEDOM, a randomized trial, wherein half of the study participants received subcutaneous denosumab 60 mg twice yearly and the others received placebo. Cortical 3D bone thickness maps of both hips were created from scans at baseline, 12, 24, and 36 months. Cortical mass surface density maps were also created for each visit. After registration of each bone to an average femur shape model followed by statistical parametric mapping, we visualized and quantified statistically significant treatment effects. The technique allowed us to pinpoint systematic differences between denosumab and control and to display the results on a 3D average femur model. Denosumab treatment led to an increase in femoral cortical mass surface density and thickness, already evident by the third injection (12 months). Overall, treatment with denosumab increased femoral cortical mass surface density by 5.4% over 3 years. One-third of the increase came from increasing cortical density, and two-thirds from increasing cortical thickness, relative to placebo. After 36 months, cortical mass surface density and thickness had increased by up to 12% at key locations such as the lateral femoral trochanter versus placebo. Most of the femoral cortex displayed a statistically significant relative difference by 36 months. Osteoporotic cortical bone responds rapidly to denosumab therapy, particularly in the hip trochanteric region. This mechanism may be involved in the robust decrease in hip fractures observed in denosumab-treated women at increased risk of fracture.
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Grassi L, Väänänen SP, Amin Yavari S, Jurvelin JS, Weinans H, Ristinmaa M, Zadpoor AA, Isaksson H. Full-Field Strain Measurement During Mechanical Testing of the Human Femur at Physiologically Relevant Strain Rates. J Biomech Eng 2014; 136:1901145. [DOI: 10.1115/1.4028415] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 08/27/2014] [Indexed: 11/08/2022]
Abstract
Understanding the mechanical properties of human femora is of great importance for the development of a reliable fracture criterion aimed at assessing fracture risk. Earlier ex vivo studies have been conducted by measuring strains on a limited set of locations using strain gauges (SGs). Digital image correlation (DIC) could instead be used to reconstruct the full-field strain pattern over the surface of the femur. The objective of this study was to measure the full-field strain response of cadaver femora tested at a physiological strain rate up to fracture in a configuration resembling single stance. The three cadaver femora were cleaned from soft tissues, and a white background paint was applied with a random black speckle pattern over the anterior surface. The mechanical tests were conducted up to fracture at a constant displacement rate of 15 mm/s, and two cameras recorded the event at 3000 frames per second. DIC was performed to retrieve the full-field displacement map, from which strains were derived. A low-pass filter was applied over the measured displacements before the crack opened in order to reduce the noise level. The noise levels were assessed using a dedicated control plate. Conversely, no filtering was applied at the frames close to fracture to get the maximum resolution. The specimens showed a linear behavior of the principal strains with respect to the applied force up to fracture. The strain rate was comparable to the values available in literature from in vivo measurements during daily activities. The cracks opened and fully propagated in less than 1 ms, and small regions with high values of the major principal strains could be spotted just a few frames before the crack opened. This corroborates the hypothesis of a strain-driven fracture mechanism in human bone. The data represent a comprehensive collection of full-field strains, both at physiological load levels and up to fracture. About 10,000 points were tracked on each bone, providing superior spatial resolution compared to ∼15 measurements typically collected using SGs. These experimental data collection can be further used for validation of numerical models, and for experimental verification of bone constitutive laws and fracture criteria.
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Affiliation(s)
- Lorenzo Grassi
- Division of Solid Mechanics, Lund University, Lund 22363, Sweden
- Department of Biomedical Engineering, Lund University, BMC D13, Sölvegatan 19, Lund 22184, Sweden e-mail:
| | - Sami P. Väänänen
- Department of Applied Physics, University of Eastern Finland, Kuopio 70211, Finland
| | - Saber Amin Yavari
- Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands
| | - Jukka S. Jurvelin
- Department of Applied Physics, University of Eastern Finland, Kuopio 70211, Finland
| | - Harrie Weinans
- Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands
- Department of Orthopaedics, UMC Utrecht 3508 GA, The Netherlands
| | - Matti Ristinmaa
- Division of Solid Mechanics, Lund University, Lund 22363, Sweden
| | - Amir A. Zadpoor
- Faculty of Mechanical, Maritime, and Materials Engineering, Delft University of Technology, Delft 2628 CD, The Netherlands
| | - Hanna Isaksson
- Division of Solid Mechanics, Lund University, Lund 22363, Sweden
- Department of Biomedical Engineering, Lund University, Lund 22184, Sweden
- Department of Orthopaedics, Lund University, Lund 22184, Sweden
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27
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Gronewold J, Berner S, Olender G, Hurschler C, Windhagen H, von Lewinski G, Floerkemeier T. Changes in strain patterns after implantation of a short stem with metaphyseal anchorage compared to a standard stem: an experimental study in synthetic bone. Orthop Rev (Pavia) 2014; 6:5211. [PMID: 24744840 PMCID: PMC3980156 DOI: 10.4081/or.2014.5211] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 01/25/2014] [Accepted: 01/26/2014] [Indexed: 11/23/2022] Open
Abstract
Short stem hip arthroplasties with predominantly metaphyseal fixation, such as the METHA® stem (Aesculap, Tuttlingen, Germany), are recommended because they are presumed to allow a more physiologic load transfer and thus a reduction of stress-shielding. However, the hypothesized metaphyseal anchorage associated with the aforementioned benefits still needs to be verified. Therefore, the METHA short stem and the Bicontact® standard stem (Aesculap, Tuttlingen, Germany) were tested biomechanically in synthetic femora while strain gauges monitored their corresponding strain patterns. For the METHA stem, the strains in all tested locations including the region of the calcar (87% of the non-implanted femur) were similar to conditions of synthetic bone without implanted stem. The Bicontact stem showed approximately the level of strain of the non-implanted femur on the lateral and medial aspect in the proximal diaphysis of the femur. On the anterior and posterior aspect of the proximal metaphysis the strains reached averages of 78% and 87% of the non-implanted femur, respectively. This study revealed primary metaphyseal anchorage of the METHA short stem, as opposed to a metaphyseal-diaphyseal anchorage of the Bicontact stem.
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Affiliation(s)
- Jens Gronewold
- Department of Orthopedic Surgery, Hannover Medical School , Germany
| | - Sebastian Berner
- Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany
| | - Gavin Olender
- Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany
| | - Christof Hurschler
- Biomechanics and Biomaterials Laboratory, Hannover Medical School , Germany
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CRISTOFOLINI LUCA, BALEANI MASSIMILIANO, SCHILEO ENRICO, VAN SINT JAN SERGE, JUSZCZYK MATEUSZMARIA, ÖHMAN CAROLINE, ZWIERZAK IWONA, LEFÈVRE PHILIPPE, JUSZCZYK JANMARIA, VICECONTI MARCO. DIFFERENCES BETWEEN CONTRALATERAL BONES OF THE HUMAN LOWER LIMBS: A MULTISCALE INVESTIGATION. J MECH MED BIOL 2014. [DOI: 10.1142/s0219519414500328] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study addressed side asymmetry between human lower limb long bones. A multiscale approach was taken to investigate differences between contralateral femurs, tibias and fibulas, at body-level (total-body CT-scans, anatomical dissection), organ-level (volume and moments of areas; structural stiffness and strain distribution in bending and torsions) and tissue-level (mineral density, elastic modulus, hardness). Because of the large amount of measurements taken, the study was limited to two donors. However, high statistical power within the same donor was achieved thanks to a large number of highly-repeatable measurements. Muscle cross-sections suggested that both donors were right-legged. The right bones had higher structural stiffness (up to +115%, statistically significant, except for the tibia). The right bones also experienced generally lower strain than the contralateral ones (up to -25%, statistically significant). The right bones had larger volume (up to +16%) and moments of area (up to +116%, statistically significant in most cases) than the left ones. Difference in tissue density between contralateral bones (< 7%) was not statistically significant in most cases. Also the differences found in elastic modulus of the femur cortical tissue (2–5%) were not statistically significant. Similarly, tissue hardness in the right bones was only marginally higher than in the contralateral ones (+1% to +4%, not statistically significant). Therefore, it seems that structural differences between contralateral bones associated with laterality are mainly explained by differences in bone quantity (volume) and organization (area moments). Bone tissue quality (density, hardness) seems to give a marginal contribution to structural side asymmetry.
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Affiliation(s)
- LUCA CRISTOFOLINI
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy
- Department of Industrial Engineering, School of Engineering and Architecture, University of Bologna, Italy
| | | | - ENRICO SCHILEO
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - SERGE VAN SINT JAN
- Laboratory of Anatomy, Biomechanics and Organogenesis, Université Libre de Bruxelles, Belgium
| | - MATEUSZ MARIA JUSZCZYK
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy
- Department of Industrial Engineering, School of Engineering and Architecture, University of Bologna, Italy
| | - CAROLINE ÖHMAN
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy
- Department of Industrial Engineering, School of Engineering and Architecture, University of Bologna, Italy
| | - IWONA ZWIERZAK
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - PHILIPPE LEFÈVRE
- Laboratory of Anatomy, Biomechanics and Organogenesis, Université Libre de Bruxelles, Belgium
| | - JAN MARIA JUSZCZYK
- Institute of Electronics and Computer Science, Faculty of Automatic Control, Silesian University of Technology, Gliwice, Poland
| | - MARCO VICECONTI
- Department of Mechanical Engineering, University of Sheffield, Sheffield, UK
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ZANI LORENZO, CRISTOFOLINI LUCA, JUSZCZYK MATEUSZMARIA, GRASSI LORENZO, VICECONTI MARCO. A NEW PARADIGM FOR THE IN VITRO SIMULATION OF SIDEWAYS FALL LOADING OF THE PROXIMAL HUMAN FEMUR. J MECH MED BIOL 2014. [DOI: 10.1142/s0219519414500055] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Although the direction of loads applied to the proximal human femur is unpredictable during sideways fall, most in vitro and numerical simulations refer to a single loading condition (15° internal rotation; 10° adduction), which has been anecdotally suggested in the 1950s. The aim of the present study was to improve in vitro simulations of sideways falls on the proximal femur. An in vitro setup was developed that allowed exploring a range of loading directions +/-90° internal–external rotation; 0°–50° adduction). To enable accurate control of the loading conditions (direction and magnitude of all load components applied to the femur), the setup included a number of low-friction linear and rotary bearings. The setup was instrumented with an axial and a torsional load cell, three displacement transducers and a rotation transducer to monitor the most significant components of load/displacement during testing. The strain distribution was measured on the bone surface (16 triaxial strain gauges, 2,000 Hz). Fracture was recorded with a high-speed camera. The setup was successfully tested on a cadaveric femur non-destructively (12 loading configurations) and destructively (15° internal rotation; 10° adduction). All measurements were highly repeatable (the displacements of the femoral head varied by < 2% between repetitions; the tilt in the frontal plane by < 0.05°; and strain varied on average 0.34% between repetitions). The displacement of the femoral head varied by over 50% when the same force was applied in different directions. Principal strains at the same location varied by over 70%, depending on the direction of the applied force. The high-speed video enabled the identification of the point of fracture initiation. This study has shown that a new paradigm for testing the proximal femur (including improved testing conditions and a variety of loading configurations) can provide more accurate and more extensive information about the state of strain.
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Affiliation(s)
- LORENZO ZANI
- Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy
| | | | - MATEUSZ MARIA JUSZCZYK
- Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy
- Department of Industrial Engineering, University of Bologna, Italy
| | - LORENZO GRASSI
- Medical Technology Laboratory, Rizzoli Orthopaedic Institute, Bologna, Italy
| | - MARCO VICECONTI
- Department of Mechanical Engineering, University of Sheffield, UK
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BRANDOLINI NICOLA, CRISTOFOLINI LUCA, VICECONTI MARCO. EXPERIMENTAL METHODS FOR THE BIOMECHANICAL INVESTIGATION OF THE HUMAN SPINE: A REVIEW. J MECH MED BIOL 2014. [DOI: 10.1142/s0219519414300026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In vitro mechanical testing of spinal specimens is extremely important to better understand the biomechanics of the healthy and diseased spine, fracture, and to test/optimize surgical treatment. While spinal testing has extensively been carried out in the past four decades, testing methods are quite diverse. This paper aims to provide a critical overview of the in vitro methods for mechanical testing the human spine at different scales. Specimens of different type are used, according to the aim of the study: spine segments (two or more adjacent vertebrae) are used both to investigate the spine kinematics, and the mechanical properties of the spine components (vertebrae, ligaments, discs); single vertebrae (whole vertebra, isolated vertebral body, or vertebral body without endplates) are used to investigate the structural properties of the vertebra itself; core specimens are extracted to test the mechanical properties of the trabecular bone at the tissue-level; mechanical properties of spine soft tissue (discs, ligaments, spinal cord) are measured on isolated elements, or on tissue specimens. Identification of consistent reference frames is still a debated issue. Testing conditions feature different pre-conditioning and loading rates, depending on the simulated action. Tissue specimen preservation is a very critical issue, affecting test results. Animal models are often used as a surrogate. However, because of different structure and anatomy, extreme caution is required when extrapolating to the human spine. In vitro loading conditions should be based on reliable in vivo data. Because of the high complexity of the spine, such information (either through instrumented implants or through numerical modeling) is currently unsatisfactory. Because of the increasing ability of computational models in predicting biomechanical properties of musculoskeletal structures, a synergy is possible (and desirable) between in vitro experiments and numerical modeling. Future perspectives in spine testing include integration of mechanical and structural properties at different dimensional scales (from the whole-body-level down to the tissue-level) so that organ-level models (which are used to predict the most relevant phenomena such as fracture) include information from all dimensional scales.
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Affiliation(s)
- NICOLA BRANDOLINI
- Laboratory for Medical Technology, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy
- School of Mechanical Engineering, University of Leeds, Woodhouse Lane, LS2 9JT Leeds, UK
| | - LUCA CRISTOFOLINI
- Department of Industrial Engineering, School of Engineering and Architecture, University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
| | - MARCO VICECONTI
- Laboratory for Medical Technology, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy
- Department of Mechanical Engineering, University of Sheffield, Sheffield, UK
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Repeatability of digital image correlation for measurement of surface strains in composite long bones. J Biomech 2013; 46:1928-32. [DOI: 10.1016/j.jbiomech.2013.05.021] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 05/24/2013] [Accepted: 05/24/2013] [Indexed: 11/21/2022]
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32
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Cristofolini L, Angeli E, Juszczyk JM, Juszczyk MM. Shape and function of the diaphysis of the human tibia. J Biomech 2013; 46:1882-92. [DOI: 10.1016/j.jbiomech.2013.04.026] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 04/18/2013] [Accepted: 04/23/2013] [Indexed: 11/25/2022]
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33
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Grassi L, Väänänen SP, Amin Yavari S, Weinans H, Jurvelin JS, Zadpoor AA, Isaksson H. Experimental validation of finite element model for proximal composite femur using optical measurements. J Mech Behav Biomed Mater 2013; 21:86-94. [DOI: 10.1016/j.jmbbm.2013.02.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 01/31/2013] [Accepted: 02/04/2013] [Indexed: 10/27/2022]
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Full-field strain measurement and fracture analysis of rat femora in compression test. J Biomech 2013; 46:1282-92. [DOI: 10.1016/j.jbiomech.2013.02.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Revised: 02/12/2013] [Accepted: 02/12/2013] [Indexed: 11/16/2022]
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The influence of resection height on proximal femoral strain patterns after Metha short stem hip arthroplasty: an experimental study on composite femora. INTERNATIONAL ORTHOPAEDICS 2012; 37:369-77. [PMID: 23271689 DOI: 10.1007/s00264-012-1725-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Accepted: 11/17/2012] [Indexed: 01/30/2023]
Abstract
PURPOSE The number of candidates for a total hip arthroplasty (THA) is steadily increasing, while the average patient age is decreasing for primary THA. The rise in THA is mainly due to excellent clinical outcomes and the extended longevity of modern implants. Short stem arthroplasties with predominantly metaphyseal fixation such as the Metha® stem are suggested for young patients. It is hypothesised that the more physiological load transfer of these devices reduces stress shielding, which in turn may reduce the risk of aseptic loosening. However, patients with femoral deformities often require a deviation of the resection height. To this end, our aim was to evaluate how resection height influences strain patterns in order to characterise possible limits for short stem implantation. METHODS Biomechanical testing using ten strain gauges on synthetic bone illustrated the strain patterns of three different resection heights (0, +5 and +10 mm) for the Metha stem. RESULTS The greatest differences in strains were displayed at the "high" (most proximal) resection height (+10 mm) when compared to the non-implanted strain pattern. At the medial calcar, the strain was 143% for +10 mm, 96% for +5 mm and 94% for 0 mm. Overall, discrepancies were less for deeper resections. CONCLUSIONS The deeper the resection, the more similar the strain patterns are when compared to a non-implanted synthetic bone. Changes in strain patterns are induced by variation in the varus/valgus positioning of the implant and by different offsets.
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Juszczyk MM, Cristofolini L, Salvà M, Zani L, Schileo E, Viceconti M. Accurate in vitro identification of fracture onset in bones: failure mechanism of the proximal human femur. J Biomech 2012; 46:158-64. [PMID: 23218142 DOI: 10.1016/j.jbiomech.2012.11.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Revised: 10/05/2012] [Accepted: 11/03/2012] [Indexed: 11/27/2022]
Abstract
Bone fractures have extensively been investigated, especially for the proximal femur. While failure load can easily be recorded, and the fracture surface is readily accessible, identification of the point of fracture initiation is difficult. Accurate location of fracture initiation is extremely important to understand the multi-scale determinants of bone fracture. In this study, a recently developed technique based on electro-conductive lines was applied to the proximal femoral metaphysis to elucidate the fracture mechanism. Eight cadaveric femurs were prepared with 15-20 electro-conductive lines (crack-grid) covering the proximal region. The crack-grid was connected to a dedicated data-logger that monitored electrical continuity of each line at 700 kHz. High-speed videos (12,000 frames/s, 0.1-0.2 mm pixel size) of the destructive tests were acquired. Most crack-grid-lines failed in a time-span of 0.08-0.50 ms, which was comparable to that identified in the high-speed videos, and consistent with previous video recordings. However, on all specimens 1-3 crack-grid-lines failed significantly earlier (2-200 ms) than the majority of the crack-grid-lines. The first crack-grid-line to fail was always the closest one to the point of fracture initiation identified in the high-speed videos (superior-lateral neck region). Then the crack propagated simultaneously, at comparable velocity on the anterior and posterior sides of the neck. Such a failure pattern has never been observed before, as spatial resolution of the high-speed videos prevented from observing the initial opening of a crack. This mechanism (fracture onset, time-lag, followed by catastrophic failure) can be explained with a transfer of load to the internal trabecular structure caused by the initial fracture of the thin cortical shell. This study proves the suitability of the crack-grid method to investigate bone fractures associated to tensile stress. The crack-grid method enables significantly faster sampling than high-speed cameras. The present findings elucidate some aspects of the failure mechanism of the proximal human femoral metaphysis.
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Wik TS. Experimental evaluation of new concepts in hip arthroplasty. Acta Orthop 2012; 83:1-26. [PMID: 22489909 DOI: 10.3109/17453674.2012.678804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In this thesis we evaluated two different hip arthroplasty concepts trough in vitro studies and numerical analyses. The cortical strains in the femoral neck area were increased by 10 to 15 % after insertion of a resurfacing femoral component compared to values of the intact femur, shown in an in vitro study on human cadaver femurs. There is an increased risk of femoral neck fracture after hip resurfacing arthroplasty. An increase of 10 to 15 % in femoral neck strains is limited, and cannot alone explain these fractures. Together with patient specific and surgical factors, however, increased strain can contribute to increased risk of fracture. An in vitro study showed that increasing the neck length in combination with retroversion or reduced neck shaft angle on a standard cementless femoral stem does not compromise the stability of the stem. The strain pattern in the proximal femur increased significantly at several measuring sites when the version and length of neck were altered. However, the changes were probably too small to have clinical relevance. In a validation study we have shown that a subject specific finite element analysis is able to perform reasonable predictions of strains and stress shielding after insertion of a femoral stem in human cadaver femurs. The usage of finite element models can be a valuable supplement to in vitro tests of femoral strain pattern around hip arthroplasty. Finally, a patient case shows that bone resorption around an implant caused by stress shielding can in extreme cases lead to periprosthetic fracture.
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Affiliation(s)
- Tina Strømdal Wik
- Orthopaedic Research Centre, St Olav Hospital, Trondheim University Hospital, Postbox 3250 Sluppen, NO-7006 Trondheim, Norway.
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Shah S, Bougherara H, Schemitsch EH, Zdero R. Biomechanical stress maps of an artificial femur obtained using a new infrared thermography technique validated by strain gages. Med Eng Phys 2012; 34:1496-502. [PMID: 22430061 DOI: 10.1016/j.medengphy.2012.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 02/20/2012] [Accepted: 02/26/2012] [Indexed: 01/21/2023]
Abstract
Femurs are the heaviest, longest, and strongest long bones in the human body and are routinely subjected to cyclic forces. Strain gages are commonly employed to experimentally validate finite element models of the femur in order to generate 3D stresses, yet there is little information on a relatively new infrared (IR) thermography technique now available for biomechanics applications. In this study, IR thermography validated with strain gages was used to measure the principal stresses in the artificial femur model from Sawbones (Vashon, WA, USA) increasingly being used for biomechanical research. The femur was instrumented with rosette strain gages and mechanically tested using average axial cyclic forces of 1500 N, 1800 N, and 2100 N, representing 3 times body weight for a 50 kg, 60 kg, and 70 kg person. The femur was oriented at 7° of adduction to simulate the single-legged stance phase of walking. Stress maps were also obtained using an IR thermography camera. Results showed good agreement of IR thermography vs. strain gage data with a correlation of R(2)=0.99 and a slope=1.08 for the straight line of best fit. IR thermography detected the highest principal stresses on the superior-posterior side of the neck, which yielded compressive values of -91.2 MPa (at 1500 N), -96.0 MPa (at 1800 N), and -103.5 MPa (at 2100 N). There was excellent correlation between IR thermography principal stress vs. axial cyclic force at 6 locations on the femur on the lateral (R(2)=0.89-0.99), anterior (R(2)=0.87-0.99), and posterior (R(2)=0.81-0.99) sides. This study shows IR thermography's potential for future biomechanical applications.
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Affiliation(s)
- Suraj Shah
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
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Accuracy of finite element predictions in sideways load configurations for the proximal human femur. J Biomech 2012; 45:394-9. [DOI: 10.1016/j.jbiomech.2011.10.019] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 10/11/2011] [Accepted: 10/13/2011] [Indexed: 11/24/2022]
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Are spontaneous fractures possible? An example of clinical application for personalised, multiscale neuro-musculo-skeletal modelling. J Biomech 2011; 45:421-6. [PMID: 22204893 DOI: 10.1016/j.jbiomech.2011.11.048] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Accepted: 11/16/2011] [Indexed: 11/20/2022]
Abstract
Elderly frequently present variable degrees of osteopenia, sarcopenia, and neuromotor control degradation. Severely osteoporotic patients sometime fracture their femoral neck when falling. Is it possible that such fractures might occur without any fall, but rather spontaneously while the patient is performing normal movements such as level walking? The aim of this study was to verify if such spontaneous fractures are biomechanically possible, and in such case, which conditions of osteoporosis, sarcopenia, and neuromotor degradation could produce them. To the purpose, a probabilistic multiscale body-organ model validated against controlled experiments was used to predict the risk of spontaneous fractures in a population of 80-years old women, with normal weight and musculoskeletal anatomy, and variable degree of osteopenia, sarcopenia, and neuromotor control degradation. A multi-body inverse dynamics sub-model, coupled to a probabilistic neuromuscular sub-model, and to a femur finite element sub-model, formed the multiscale model, which was run within a Monte Carlo stochastic scheme, where the various parameters were varied randomly according to well defined distributions. The model predicted that neither extreme osteoporosis, nor extreme neuromotor degradation alone are sufficient to predict spontaneous fractures. However, when the two factors are combined an incidence of 0.4% of spontaneous fractures is predicted for the simulated population, which is consistent with clinical reports. When the model represented only severely osteoporotic patients, the incidence of spontaneous fractures increased to 29%. Thus, is biomechanically possible that spontaneous femoral neck fractures occur during level walking, due to a combination of severe osteoporosis and severe neuromotor degradation.
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Juszczyk MM, Cristofolini L, Viceconti M. The human proximal femur behaves linearly elastic up to failure under physiological loading conditions. J Biomech 2011; 44:2259-66. [DOI: 10.1016/j.jbiomech.2011.05.038] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 05/26/2011] [Accepted: 05/27/2011] [Indexed: 11/26/2022]
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Cristofolini L, Juszczyk M, Taddei F, Field RE, Rushton N, Viceconti M. Assessment of femoral neck fracture risk for a novel proximal epiphyseal hip prosthesis. Clin Biomech (Bristol, Avon) 2011; 26:585-91. [PMID: 21334123 DOI: 10.1016/j.clinbiomech.2011.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 12/16/2010] [Accepted: 01/19/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND This study addresses the risk of femoral neck fracture associated with resurfacing hip prostheses. A novel cemented Proximal Epiphyseal Replacement (PER) featuring a short curved stem was investigated. METHODS Seven pairs of femurs were in vitro tested. One femur of each pair was randomly assigned for PER implantation. The contralateral femur was tested intact. All femurs were loaded to failure in a validated, physiological configuration. High-speed videos (10,000-12,000 frames/s) were acquired to identify the location of fracture initiation. For comparison, data were included from Birmingham Hip Resurfacing previously tested in an identical fashion (N=3). FINDINGS Relative to the contralateral intact femurs, the failure load of the PER and Birmingham implants was 15.4% higher and 10.0% lower, respectively. In six of the seven PER implants, fracture initiation (neck or inter-trochanteric) was similar to the contralateral intact femurs, suggesting comparable stress distribution. Conversely, fracture initiation in the Birmingham implants occurred at the lateral prosthesis rim, which differed substantially from the intact femurs. No correlation existed between bone quality and strengthening/weakening effect of the PER (failure load of implant as a percentage of intact: R^2=0.067). Conversely, Birmingham implantation weakened the femurs with lower density (R^2=0.92). Therefore, unlike most resurfacing prostheses, the PER seems suitable also for osteoporotic subjects. INTERPRETATION This study seems to confirm that resurfacing with a Birmingham Hip tends to reduce the strength of the proximal femur. The opposite seemed to happen with the PER, which slightly reduced the risk of neck fracture, also in low-quality bones.
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Affiliation(s)
- Luca Cristofolini
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, Bologna, Italy.
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Peng Q, Wang Y, Qiu J, Zhang B, Sun J, Lv Y, Yang L. A novel mechanical loading model for studying the distributions of strain and mechano-growth factor expression. Arch Biochem Biophys 2011; 511:8-13. [DOI: 10.1016/j.abb.2011.04.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 04/19/2011] [Accepted: 04/22/2011] [Indexed: 01/06/2023]
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Trabelsi N, Yosibash Z. Patient-Specific Finite-Element Analyses of the Proximal Femur with Orthotropic Material Properties Validated by Experiments. J Biomech Eng 2011; 133:061001. [DOI: 10.1115/1.4004180] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Abstract
Patient-specific high order finite-element (FE) models of human femurs based on quantitative computer tomography (QCT) with inhomogeneous orthotropic and isotropic material properties are addressed. The point-wise orthotropic properties are determined by a micromechanics (MM) based approach in conjunction with experimental observations at the osteon level, and two methods for determining the material trajectories are proposed (along organs outer surface, or along principal strains). QCT scans on four fresh-frozen human femurs were performed and high-order FE models were generated with either inhomogeneous MM-based orthotropic or empirically determined isotropic properties. In vitro experiments were conducted on the femurs by applying a simple stance position load on their head, recording strains on femurs’ surface and head’s displacements. After verifying the FE linear elastic analyses that mimic the experimental setting for numerical accuracy, we compared the FE results to the experimental observations to identify the influence of material properties on models’ predictions. The strains and displacements computed by FE models having MM-based inhomogeneous orthotropic properties match the FE-results having empirically based isotropic properties well, and both are in close agreement with the experimental results. When only the strains in the femoral neck are being compared a more pronounced difference is noticed between the isotropic and orthotropic FE result. These results lay the foundation for applying more realistic inhomogeneous orthotropic material properties in FEA of femurs.
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Affiliation(s)
- Nir Trabelsi
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
| | - Zohar Yosibash
- Department of Mechanical Engineering, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel
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Pal B, Gupta S, New AM, Browne M. Strain and micromotion in intact and resurfaced composite femurs: Experimental and numerical investigations. J Biomech 2010; 43:1923-30. [DOI: 10.1016/j.jbiomech.2010.03.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Revised: 03/09/2010] [Accepted: 03/11/2010] [Indexed: 11/29/2022]
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Cristofolini L, Schileo E, Juszczyk M, Taddei F, Martelli S, Viceconti M. Mechanical testing of bones: the positive synergy of finite-element models and in vitro experiments. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2010; 368:2725-2763. [PMID: 20439271 DOI: 10.1098/rsta.2010.0046] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Bone biomechanics have been extensively investigated in the past both with in vitro experiments and numerical models. In most cases either approach is chosen, without exploiting synergies. Both experiments and numerical models suffer from limitations relative to their accuracy and their respective fields of application. In vitro experiments can improve numerical models by: (i) preliminarily identifying the most relevant failure scenarios; (ii) improving the model identification with experimentally measured material properties; (iii) improving the model identification with accurately measured actual boundary conditions; and (iv) providing quantitative validation based on mechanical properties (strain, displacements) directly measured from physical specimens being tested in parallel with the modelling activity. Likewise, numerical models can improve in vitro experiments by: (i) identifying the most relevant loading configurations among a number of motor tasks that cannot be replicated in vitro; (ii) identifying acceptable simplifications for the in vitro simulation; (iii) optimizing the use of transducers to minimize errors and provide measurements at the most relevant locations; and (iv) exploring a variety of different conditions (material properties, interface, etc.) that would require enormous experimental effort. By reporting an example of successful investigation of the femur, we show how a combination of numerical modelling and controlled experiments within the same research team can be designed to create a virtuous circle where models are used to improve experiments, experiments are used to improve models and their combination synergistically provides more detailed and more reliable results than can be achieved with either approach singularly.
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Taddei F, Martelli S, Gill HS, Cristofolini L, Viceconti M. Finite Element Modeling of Resurfacing Hip Prosthesis: Estimation of Accuracy Through Experimental Validation. J Biomech Eng 2010; 132:021002. [DOI: 10.1115/1.4000065] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Metal-on-metal hip resurfacing is becoming increasingly popular, and a number of new devices have been recently introduced that, in the short term, appear to have satisfactory outcome but many questions are still open on the biomechanics of the resurfaced femur. This could be investigated by means of finite element analysis, but, in order to be effective in discerning potential critical conditions, the accuracy of the models’ predictions should be assessed. The major goal of this study was to validate, through a combined experimental-numerical study, a finite element modeling procedure for the simulation of resurfaced femurs. In addition, a preliminary biomechanical analysis of the changes induced in the femoral neck biomechanics by the presence of the device was performed, under a physiologic range of hip joint reaction directions. For this purpose, in vitro tests and a finite element model based on the same specimen were developed using a cadaver femur. The study focused on the Conserve Plus, one of the most common contemporary resurfacing designs. Five loading configurations were identified to correspond to the extremes of physiological directions for the hip joint. The agreement between experimental measurements and numerical predictions was good both in the prediction of the femoral strains (R2>0.9), and in the prosthesis micromotions (error<20 μm), giving confidence in the model predictions. The preliminary biomechanical analysis indicated that the strains in the femoral neck are moderately affected by the presence of the prosthesis, apart from localized strain increments that can be considerable, always predicted near the stem. Low micromotions and contact pressure were predicted, suggesting a good stability of the prosthesis. The model accuracy was good in the prediction of the femoral strains and moderately good in the prediction of the bone-prosthesis micromovements. Although the investigated loading conditions were not completely physiological, the preliminary biomechanical analysis showed relatively small changes for the proximal femur after implantation. This validated model can support realistic simulations to examine physiological load configurations and the effects of variations in prosthesis design and implantation technique.
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Affiliation(s)
- Fulvia Taddei
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
| | - Saulo Martelli
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy; Facoltà di Ingegneria, Università degli Studi di Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
| | - Harinderjit Singh Gill
- Nuffield Department of Orthopaedic Surgery, University of Oxford, Nuffield Orthopaedic Centre, Oxford, UK
| | - Luca Cristofolini
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy; Facoltà di Ingegneria, Università degli Studi di Bologna, Viale Risorgimento 2, 40136 Bologna, Italy
| | - Marco Viceconti
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano 1/10, 40136 Bologna, Italy
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Cristofolini L, Conti G, Juszczyk M, Cremonini S, Van Sint Jan S, Viceconti M. Structural behaviour and strain distribution of the long bones of the human lower limbs. J Biomech 2009; 43:826-35. [PMID: 20031136 DOI: 10.1016/j.jbiomech.2009.11.022] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Revised: 11/02/2009] [Accepted: 11/20/2009] [Indexed: 10/20/2022]
Abstract
Although stiffness and strength of lower limb bones have been investigated in the past, information is not complete. While the femur has been extensively investigated, little information is available about the strain distribution in the tibia, and the fibula has not been tested in vitro. This study aimed at improving the understanding of the biomechanics of lower limb bones by: (i) measuring the stiffness and strain distributions of the different low limb bones; (ii) assessing the effect of viscoelasticity in whole bones within a physiological range of strain-rates; (iii) assessing the difference in the behaviour in relation to opposite directions of bending and torsion. The structural stiffness and strain distribution of paired femurs, tibias and fibulas from two donors were measured. Each region investigated of each bone was instrumented with 8-16 triaxial strain gauges (over 600 grids in total). Each bone was subjected to 6-12 different loading configurations. Tests were replicated at two different loading speeds covering the physiological range of strain-rates. Viscoelasticity did not have any pronounced effect on the structural stiffness and strain distribution, in the physiological range of loading rates explored in this study. The stiffness and strain distribution varied greatly between bone segments, but also between directions of loading. Different stiffness and strain distributions were observed when opposite directions of torque or opposite directions of bending (in the same plane) were applied. To our knowledge, this study represents the most extensive collection of whole-bone biomechanical properties of lower limb bones.
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Affiliation(s)
- Luca Cristofolini
- Laboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Via di Barbiano, 1/10, 40136 Bologna, Italy.
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Hunter PJ, Viceconti M. The VPH-Physiome Project: Standards and Tools for Multiscale Modeling in Clinical Applications. IEEE Rev Biomed Eng 2009. [DOI: 10.1109/rbme.2009.2036204] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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