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Maquer G, Mueri C, Henderson A, Bischoff J, Favre P. Developing and Validating a Model of Humeral Stem Primary Stability, Intended for In Silico Clinical Trials. Ann Biomed Eng 2024; 52:1280-1296. [PMID: 38361138 DOI: 10.1007/s10439-024-03452-w] [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: 08/31/2023] [Accepted: 01/12/2024] [Indexed: 02/17/2024]
Abstract
In silico clinical trials (ISCT) can contribute to demonstrating a device's performance via credible computational models applied on virtual cohorts. Our purpose was to establish the credibility of a model for assessing the risk of humeral stem loosening in total shoulder arthroplasty, based on a twofold validation scheme involving both benchtop and clinical validation activities, for ISCT applications. A finite element model computing bone-implant micromotion (benchtop model) was quantitatively compared to a bone foam micromotion test (benchtop comparator) to ensure that the physics of the system was captured correctly. The model was expanded to a population-based approach (clinical model) and qualitatively evaluated based on its ability to replicate findings from a published clinical study (clinical comparator), namely that grit-blasted stems are at a significantly higher risk of loosening than porous-coated stems, to ensure that clinical performance of the stem can be predicted appropriately. Model form sensitivities pertaining to surgical variation and implant design were evaluated. The model replicated benchtop micromotion measurements (52.1 ± 4.3 µm), without a significant impact of the press-fit ("Press-fit": 54.0 ± 8.5 µm, "No press-fit": 56.0 ± 12.0 µm). Applied to a virtual population, the grit-blasted stems (227 ± 78µm) experienced significantly larger micromotions than porous-coated stems (162 ± 69µm), in accordance with the findings of the clinical comparator. This work provides a concrete example for evaluating the credibility of an ISCT study. By validating the modeling approach against both benchtop and clinical data, model credibility is established for an ISCT application aiming to enrich clinical data in a regulatory submission.
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Affiliation(s)
- Ghislain Maquer
- Zimmer Biomet, Sulzerallee 8, 8404, Winterthur, Switzerland.
| | | | - Adam Henderson
- Zimmer Biomet, Sulzerallee 8, 8404, Winterthur, Switzerland
| | - Jeff Bischoff
- Zimmer Biomet, 1800 West Center St., Warsaw, IN, 46580, USA
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Dagneaux L, Canovas F, Jourdan F. Finite element analysis in the optimization of posterior-stabilized total knee arthroplasty. Orthop Traumatol Surg Res 2024; 110:103765. [PMID: 37979672 DOI: 10.1016/j.otsr.2023.103765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 06/06/2023] [Indexed: 11/20/2023]
Abstract
Posterior-stabilized total knee arthroplasty (PS-TKA) is associated with high rates of satisfaction and functional recovery. This is notably attributed to implant optimization in terms of design, choice of materials, positioning and understanding of biomechanics. Finite elements analysis (FEA) is an assessment technique that contributed to this optimization by ensuring mechanical results based on numerical simulation. By close teamwork between surgeons, researchers and engineers, FEA enabled testing of certain clinical impressions. However, the methodological features of the technique led to wide variations in the presentation and interpretation of results, requiring a certain understanding of numerical and biomechanical fields by the orthopedic community. The present study provides an up-to-date review, aiming to address the following questions: what are the principles of FEA? What is the role of FEA in studying PS design in TKA? What are the key elements in the literature for understanding the role of FEA in PS-TKA? What is the contribution of FEA for understanding of tibiofemoral and patellofemoral biomechanical behavior? What are the limitations and perspectives of digital simulation and FEA in routine practice, with a particular emphasis on the "digital twin" concept? LEVEL OF EVIDENCE: V, expert opinion.
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Affiliation(s)
- Louis Dagneaux
- Service de chirurgie orthopédique et traumatologie du membre inférieur, hôpital Lapeyronie, CHU de Montpellier, 371, avenue Gaston-Giraud, 34295 Montpellier cedex 5, France; Laboratoire de mécanique et génie civil (LMGC), Montpellier University of Excellence (MUSE), université de Montpellier, 860, rue de St-Priest, 34090 Montpellier, France.
| | - François Canovas
- Service de chirurgie orthopédique et traumatologie du membre inférieur, hôpital Lapeyronie, CHU de Montpellier, 371, avenue Gaston-Giraud, 34295 Montpellier cedex 5, France
| | - Franck Jourdan
- Laboratoire de mécanique et génie civil (LMGC), Montpellier University of Excellence (MUSE), université de Montpellier, 860, rue de St-Priest, 34090 Montpellier, France
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Rooks NB, Besier TF, Schneider MTY. A Parameter Sensitivity Analysis on Multiple Finite Element Knee Joint Models. Front Bioeng Biotechnol 2022; 10:841882. [PMID: 35694233 PMCID: PMC9178290 DOI: 10.3389/fbioe.2022.841882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 04/18/2022] [Indexed: 11/28/2022] Open
Abstract
The reproducibility of computational knee joint modeling is questionable, with models varying depending on the modeling team. The influence of model variations on simulation outcomes should be investigated, since knowing the sensitivity of the model outcomes to model parameters could help determine which parameters to calibrate and which parameters could potentially be standardized, improving model reproducibility. Previous sensitivity analyses on finite element knee joint models have typically used one model, with a few parameters and ligaments represented as line segments. In this study, a parameter sensitivity analysis was performed using multiple finite element knee joint models with continuum ligament representations. Four previously developed and calibrated models of the tibiofemoral joint were used. Parameters of the ligament and meniscus material models, the cartilage contact formulation, the simulation control and the rigid cylindrical joints were studied. Varus-valgus simulations were performed, changing one parameter at a time. The sensitivity on model convergence, valgus kinematics, articulating cartilage contact pressure and contact pressure location were investigated. A scoring system was defined to categorize the parameters as having a “large,” “medium” or “small” influence on model output. Model outcomes were sensitive to the ligament prestretch factor, Young’s modulus and attachment condition parameters. Changes in the meniscus horn stiffness had a “small” influence. Of the cartilage contact parameters, the penalty factor and Augmented Lagrangian setting had a “large” influence on the cartilage contact pressure. In the rigid cylindrical joint, the largest influence on the outcome parameters was found by the moment penalty parameter, which caused convergence issues. The force penalty and gap tolerance had a “small” influence at most. For the majority of parameters, the sensitivity was model-dependent. For example, only two models showed convergence issues when changing the Quasi-Newton update method. Due to the sensitivity of the model parameters being model-specific, the sensitivity of the parameters found in one model cannot be assumed to be the same in other models. The sensitivity of the model outcomes to ligament material properties confirms that calibration of these parameters is critical and using literature values may not be appropriate.
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Affiliation(s)
- Nynke B. Rooks
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Thor F. Besier
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Department of Engineering Science, Faculty of Engineering, University of Auckland, Auckland, New Zealand
- *Correspondence: Thor F. Besier,
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Rayward L, Little JP. A subject-specific FEM to predict deep tissue mechanical stresses when supine: Development of efficient contact interfaces using Shared Topology. J Biomech 2022; 137:111085. [DOI: 10.1016/j.jbiomech.2022.111085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 03/17/2022] [Accepted: 04/05/2022] [Indexed: 10/18/2022]
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Mechanical performance comparison of two surgical constructs for wrist four-corner arthrodesis via dorsal and radial approaches. Clin Biomech (Bristol, Avon) 2021; 82:105274. [PMID: 33508561 DOI: 10.1016/j.clinbiomech.2021.105274] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Revised: 01/06/2021] [Accepted: 01/11/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Four-corner arthrodesis, which involves fusing four carpal bones while removing the scaphoid bone, is a standard surgery for the treatment of advanced stages of wrist arthritis. Nowadays, it can be performed using a dorsal approach by fixing a plate to the bones and a new radial approach is in development. To date, there is no consensus on the biomechanically optimal and most reliable surgical construct for four-corner arthrodesis. METHODS To evaluate them biomechanically and thus assist the surgeon in choosing the best implant orientation, radial or dorsal, the two different four-corner arthrodesis surgical constructs were virtually simulated on a 3D finite element model representing all major structures of the wrist. Two different realistic load sets were applied to the model, representing common tasks for the elderly. FINDINGS Results consistency was assessed by comparing with the literature the force magnitude computed on the carpal bones. The Von Mises stress distribution in the radial and dorsal plates were calculated. Stress concentration was located at the plate-screw interface for both surgical constructs, with a maximum stress value of 413 MPa for the dorsal plate compared to 326 MPa for the radial plate, meaning that the stress levels are more unfavourable in the dorsal approach. INTERPRETATION Although some bending stress was found in one load case, the radial plate was mechanically more robust in the other load case. Despite some limitations, this study provides, for the first time, quantified evidence that the newly developed radial surgical construct is mechanically as efficient as the dorsal surgical construct.
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Caprara S, Carrillo F, Snedeker JG, Farshad M, Senteler M. Automated Pipeline to Generate Anatomically Accurate Patient-Specific Biomechanical Models of Healthy and Pathological FSUs. Front Bioeng Biotechnol 2021; 9:636953. [PMID: 33585436 PMCID: PMC7876284 DOI: 10.3389/fbioe.2021.636953] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 01/11/2021] [Indexed: 12/29/2022] Open
Abstract
State-of-the-art preoperative biomechanical analysis for the planning of spinal surgery not only requires the generation of three-dimensional patient-specific models but also the accurate biomechanical representation of vertebral joints. The benefits offered by computational models suitable for such purposes are still outweighed by the time and effort required for their generation, thus compromising their applicability in a clinical environment. In this work, we aim to ease the integration of computerized methods into patient-specific planning of spinal surgery. We present the first pipeline combining deep learning and finite element methods that allows a completely automated model generation of functional spine units (FSUs) of the lumbar spine for patient-specific FE simulations (FEBio). The pipeline consists of three steps: (a) multiclass segmentation of cropped 3D CT images containing lumbar vertebrae using the DenseVNet network, (b) automatic landmark-based mesh fitting of statistical shape models onto 3D semantic segmented meshes of the vertebral models, and (c) automatic generation of patient-specific FE models of lumbar segments for the simulation of flexion-extension, lateral bending, and axial rotation movements. The automatic segmentation of FSUs was evaluated against the gold standard (manual segmentation) using 10-fold cross-validation. The obtained Dice coefficient was 93.7% on average, with a mean surface distance of 0.88 mm and a mean Hausdorff distance of 11.16 mm (N = 150). Automatic generation of finite element models to simulate the range of motion (ROM) was successfully performed for five healthy and five pathological FSUs. The results of the simulations were evaluated against the literature and showed comparable ROMs in both healthy and pathological cases, including the alteration of ROM typically observed in severely degenerated FSUs. The major intent of this work is to automate the creation of anatomically accurate patient-specific models by a single pipeline allowing functional modeling of spinal motion in healthy and pathological FSUs. Our approach reduces manual efforts to a minimum and the execution of the entire pipeline including simulations takes approximately 2 h. The automation, time-efficiency and robustness level of the pipeline represents a first step toward its clinical integration.
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Affiliation(s)
- Sebastiano Caprara
- Department of Orthopedics, University Hospital Balgrist, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Fabio Carrillo
- Institute for Biomechanics, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
- Research in Orthopedic Computer Science, University Hospital Balgrist, Zurich, Switzerland
| | - Jess G. Snedeker
- Department of Orthopedics, University Hospital Balgrist, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Mazda Farshad
- Department of Orthopedics, University Hospital Balgrist, University of Zurich, Zurich, Switzerland
| | - Marco Senteler
- Department of Orthopedics, University Hospital Balgrist, University of Zurich, Zurich, Switzerland
- Institute for Biomechanics, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
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Validated Finite Element Models of Premolars: A Scoping Review. MATERIALS 2020; 13:ma13153280. [PMID: 32717945 PMCID: PMC7436020 DOI: 10.3390/ma13153280] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 07/16/2020] [Accepted: 07/20/2020] [Indexed: 12/02/2022]
Abstract
Finite element (FE) models are widely used to investigate the biomechanics of reconstructed premolars. However, parameter identification is a complex step because experimental validation cannot always be conducted. The aim of this study was to collect the experimentally validated FE models of premolars, extract their parameters, and discuss trends. A systematic review was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Records were identified in three electronic databases (MEDLINE [PubMed], Scopus, The Cochrane Library) by two independent reviewers. Twenty-seven parameters dealing with failure criteria, model construction, material laws, boundary conditions, and model validation were extracted from the included articles. From 1306 records, 214 were selected for eligibility and entirely read. Among them, 19 studies were included. A heterogeneity was observed for several parameters associated with failure criteria and model construction. Elasticity, linearity, and isotropy were more often chosen for dental and periodontal tissues with a Young’s modulus mostly set at 18–18.6 GPa for dentine. Loading was mainly simulated by an axial force, and FE models were mostly validated by in vitro tests evaluating tooth strains, but different conditions about experiment type, sample size, and tooth status (intact or restored) were reported. In conclusion, material laws identified herein could be applied to future premolar FE models. However, further investigations such as sensitivity analysis are required for several parameters to clarify their indication.
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Abstract
Early fusion of the sagittal suture is a clinical condition called, sagittal craniosynostosis. Calvarial reconstruction is the most common treatment option for this condition with a range of techniques being developed by different groups. Computer simulations have a huge potential to predict the calvarial growth and optimise the management of this condition. However, these models need to be validated. The aim of this study was to develop a validated patient-specific finite element model of a sagittal craniosynostosis. Here, the finite element method was used to predict the calvarial morphology of a patient based on its preoperative morphology and the planned surgical techniques. A series of sensitivity tests and hypothetical models were carried out and developed to understand the effect of various input parameters on the result. Sensitivity tests highlighted that the models are sensitive to the choice of input parameter. The hypothetical models highlighted the potential of the approach in testing different reconstruction techniques. The patient-specific model highlighted that a comparable pattern of calvarial morphology to the follow up CT data could be obtained. This study forms the foundation for further studies to use the approach described here to optimise the management of sagittal craniosynostosis.
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A Systematic Review of Continuum Modeling of Skeletal Muscles: Current Trends, Limitations, and Recommendations. Appl Bionics Biomech 2018; 2018:7631818. [PMID: 30627216 PMCID: PMC6305050 DOI: 10.1155/2018/7631818] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 11/06/2018] [Accepted: 11/13/2018] [Indexed: 12/21/2022] Open
Abstract
Finite elasticity theory has been commonly used to model skeletal muscle. A very large range of heterogeneous constitutive laws has been proposed. In this review, the most widely used continuum models of skeletal muscles were synthetized and discussed. Trends and limitations of these laws were highlighted to propose new recommendations for future researches. A systematic review process was performed using two reliable search engines as PubMed and ScienceDirect. 40 representative studies (13 passive muscle materials and 27 active muscle materials) were included into this review. Note that exclusion criteria include tendon models, analytical models, 1D geometrical models, supplement papers, and indexed conference papers. Trends of current skeletal muscle modeling relate to 3D accurate muscle representation, parameter identification in passive muscle modeling, and the integration of coupled biophysical phenomena. Parameter identification for active materials, assumed fiber distribution, data assumption, and model validation are current drawbacks. New recommendations deal with the incorporation of multimodal data derived from medical imaging, the integration of more biophysical phenomena, and model reproducibility. Accounting for data uncertainty in skeletal muscle modeling will be also a challenging issue. This review provides, for the first time, a holistic view of current continuum models of skeletal muscles to identify potential gaps of current models according to the physiology of skeletal muscle. This opens new avenues for improving skeletal muscle modeling in the framework of in silico medicine.
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Development and in vitro validation of a simplified numerical model for the design of a biomimetic femoral stem. J Mech Behav Biomed Mater 2017; 77:539-550. [PMID: 29069636 DOI: 10.1016/j.jmbbm.2017.10.019] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 10/06/2017] [Accepted: 10/15/2017] [Indexed: 11/21/2022]
Abstract
BACKGROUND Dense and stiff metallic femoral stems implanted into femurs for total hip arthroplasties produce a stress shielding effect since they modify the original load sharing path in the bony structure. Consequently, in the long term, the strain adaptive nature of bones leads to bone resorption, implant loosening, and the need for arthroplasty revision. The design of new cementless femoral stems integrating open porous structures can reduce the global stiffness of the stems, allowing them a better match with that of bones and provide their firm fixation via bone ingrowth, and, thus reduce the risk of implantation failure. METHODS This paper aims to develop and validate a simplified numerical model of stress shielding, which calculates the levels of bone resorption or formation by comparing strain distributions on the surface of the intact and the implanted femurs subjected to a simulated biological loading. Two femoral stems produced by laser powder-bed fusion using Ti-6Al-4V alloy are employed: the first is fully dense, while the second features a diamond cubic lattice structure in its core. The validation consists of a comparison of the numerically calculated force-displacement diagrams, and displacement and strain fields with their experimental equivalents obtained using the digital image correlation technique. RESULTS AND CONCLUSIONS The numerical models showed reasonable agreement between the force-displacement diagrams. Also, satisfactory results for the correlation analyses of the total displacement and equivalent strain fields were obtained. The stress shielding effect of the implant was assessed by comparing the equivalent strain fields of the implanted and intact femurs. The results obtained predicted less bone resorption in the femur implanted with the porous stem than with its dense counterpart.
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Sopher RS, Amis AA, Calder JD, Jeffers JRT. Total ankle replacement design and positioning affect implant-bone micromotion and bone strains. Med Eng Phys 2017; 42:80-90. [PMID: 28233732 PMCID: PMC5360194 DOI: 10.1016/j.medengphy.2017.01.022] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 01/12/2017] [Accepted: 01/31/2017] [Indexed: 11/20/2022]
Abstract
A finite element model was developed to calculate micromotion of ankle implants. Both optimally-positioned and malpositioned cases were considered. Fixation nearer to the joint line relying on plural pegs improved implant stability. Gaps between the implant and bone greatly increased micromotion and bone strains.
Implant loosening – commonly linked with elevated initial micromotion – is the primary indication for total ankle replacement (TAR) revision. Finite element modelling has not been used to assess micromotion of TAR implants; additionally, the biomechanical consequences of TAR malpositioning – previously linked with higher failure rates – remain unexplored. The aim of this study was to estimate implant-bone micromotion and peri-implant bone strains for optimally positioned and malpositioned TAR prostheses, and thereby identify fixation features and malpositioning scenarios increasing the risk of loosening. Finite element models simulating three of the most commonly used TAR devices (BOX®, Mobility® and Salto®) implanted into the tibia/talus and subjected to physiological loads were developed. Mobility and Salto demonstrated the largest micromotion of all tibial and talar components, respectively. Any malpositioning of the implant creating a gap between it and the bone resulted in a considerable increase in micromotion and bone strains. It was concluded that better primary stability can be achieved through fixation nearer to the joint line and/or while relying on more than a single peg. Incomplete seating on the bone may result in considerably elevated implant-bone micromotion and bone strains, thereby increasing the risk for TAR failure.
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Affiliation(s)
- Ran S Sopher
- Department of Mechanical Engineering, Imperial College London, 715 City & Guilds Building, South Kensington, London SW7 2AZ, UK
| | - Andrew A Amis
- Department of Mechanical Engineering, Imperial College London, 715 City & Guilds Building, South Kensington, London SW7 2AZ, UK ; Department of Surgery & Cancer, Imperial College London, Charing Cross Hospital, London, W6 8RP, UK
| | - James D Calder
- Department of Surgery & Cancer, Imperial College London, Charing Cross Hospital, London, W6 8RP, UK; Fortius Clinic, 17 Fitzhardinge St, London, W1H 6EQ , UK
| | - Jonathan R T Jeffers
- Department of Mechanical Engineering, Imperial College London, 715 City & Guilds Building, South Kensington, London SW7 2AZ, UK .
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Haïat G, Wang HL, Brunski J. Effects of biomechanical properties of the bone-implant interface on dental implant stability: from in silico approaches to the patient's mouth. Annu Rev Biomed Eng 2014; 16:187-213. [PMID: 24905878 DOI: 10.1146/annurev-bioeng-071813-104854] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dental implants have become a routinely used technique in dentistry for replacing teeth. However, risks of failure are still experienced and remain difficult to anticipate. Multiscale phenomena occurring around the implant interface determine the implant outcome. The aim of this review is to provide an understanding of the biomechanical behavior of the interface between a dental implant and the region of bone adjacent to it (the bone-implant interface) as a function of the interface's environment. First, we describe the determinants of implant stability in relation to the different multiscale simulation approaches used to model the evolution of the bone-implant interface. Then, we review the various aspects of osseointegration in relation to implant stability. Next, we describe the different approaches used in the literature to measure implant stability in vitro and in vivo. Last, we review various factors affecting the evolution of the bone-implant interface properties.
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Affiliation(s)
- Guillaume Haïat
- CNRS, Laboratoire Modélisation et Simulation Multiéchelle, UMR CNRS 8208, 94010 Créteil, France;
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Reimeringer M, Nuño N, Desmarais-Trépanier C, Lavigne M, Vendittoli P. The influence of uncemented femoral stem length and design on its primary stability: a finite element analysis. Comput Methods Biomech Biomed Engin 2013; 16:1221-31. [DOI: 10.1080/10255842.2012.662677] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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Ghosh R, Pal B, Ghosh D, Gupta S. Finite element analysis of a hemi-pelvis: the effect of inclusion of cartilage layer on acetabular stresses and strain. Comput Methods Biomech Biomed Engin 2013; 18:697-710. [DOI: 10.1080/10255842.2013.843674] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Mathieu V, Vayron R, Richard G, Lambert G, Naili S, Meningaud JP, Haiat G. Biomechanical determinants of the stability of dental implants: influence of the bone-implant interface properties. J Biomech 2013; 47:3-13. [PMID: 24268798 DOI: 10.1016/j.jbiomech.2013.09.021] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Revised: 09/18/2013] [Accepted: 09/24/2013] [Indexed: 12/19/2022]
Abstract
Dental implants are now widely used for the replacement of missing teeth in fully or partially edentulous patients and for cranial reconstructions. However, risks of failure, which may have dramatic consequences, are still experienced and remain difficult to anticipate. The stability of biomaterials inserted in bone tissue depends on multiscale phenomena of biomechanical (bone-implant interlocking) and of biological (mechanotransduction) natures. The objective of this review is to provide an overview of the biomechanical behavior of the bone-dental implant interface as a function of its environment by considering in silico, ex vivo and in vivo studies including animal models as well as clinical studies. The biomechanical determinants of osseointegration phenomena are related to bone remodeling in the vicinity of the implants (adaptation of the bone structure to accommodate the presence of a biomaterial). Aspects related to the description of the interface and to its space-time multiscale nature will first be reviewed. Then, the various approaches used in the literature to measure implant stability and the bone-implant interface properties in vitro and in vivo will be described. Quantitative ultrasound methods are promising because they are cheap, non invasive and because of their lower spatial resolution around the implant compared to other biomechanical approaches.
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Affiliation(s)
- Vincent Mathieu
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR CNRS 8208, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France
| | - Romain Vayron
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR CNRS 8208, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France
| | - Gilles Richard
- Septodont, 58 Rue Pont de Créteil, 94100 Saint-Maur-des-Fossés, France
| | - Grégory Lambert
- Septodont, 58 Rue Pont de Créteil, 94100 Saint-Maur-des-Fossés, France
| | - Salah Naili
- Université Paris-Est, Laboratoire Modélisation et Simulation Multi Echelle, UMR CNRS 8208, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France
| | - Jean-Paul Meningaud
- Service de Chirurgie Plastique, Reconstructrice et Esthétique, CHU H. Mondor, 94017 Créteil cedex, France
| | - Guillaume Haiat
- CNRS, Laboratoire Modélisation et Simulation Multi Echelle, UMR CNRS 8208, 61 avenue du Général de Gaulle, 94010 Créteil cedex, France.
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Moazen M, Mak JH, Etchels LW, Jin Z, Wilcox RK, Jones AC, Tsiridis E. The effect of fracture stability on the performance of locking plate fixation in periprosthetic femoral fractures. J Arthroplasty 2013; 28:1589-95. [PMID: 23642449 DOI: 10.1016/j.arth.2013.03.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/21/2013] [Accepted: 03/21/2013] [Indexed: 02/01/2023] Open
Abstract
Periprosthetic femoral fracture (PFF) fixation failures are still occurring. The effect of fracture stability and loading on PFF fixation has not been investigated and this is crucial for optimum management of PFF. Models of stable and unstable PPFs were developed and used to quantify the effect of fracture stability and loading in a single locking plate fixation. Stress on the plate was higher in the unstable compared to the stable fixation. In the case of unstable fractures, it is possible for a single locking plate fixation to provide the required mechanical environment for callus formation without significant risk of plate fracture, provided partial weight bearing is followed. In cases where partial weight bearing is unlikely, additional biological fixation could be considered.
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Affiliation(s)
- Mehran Moazen
- Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds LS2 9JT, UK; Medical and Biological Engineering, School of Engineering, University of Hull, Hull HU6 7RX, UK
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Moazen M, Mak JH, Jones AC, Jin Z, Wilcox RK, Tsiridis E. Evaluation of a new approach for modelling the screw–bone interface in a locking plate fixation: A corroboration study. Proc Inst Mech Eng H 2013; 227:746-56. [DOI: 10.1177/0954411913483259] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Computational modelling of the screw–bone interface in fracture fixation constructs is challenging. While incorporating screw threads would be a more realistic representation of the physics, this approach can be computationally expensive. Several studies have instead suppressed the threads and modelled the screw shaft with fixed conditions assumed at the screw–bone interface. This study assessed the sensitivity of the computational results to modelling approaches at the screw–bone interface. A new approach for modelling this interface was proposed, and it was tested on two locking screw designs in a diaphyseal bridge plating configuration. Computational models of locked plating and far cortical locking constructs were generated and compared to in vitro models described in prior literature to corroborate the outcomes. The new approach led to closer agreement between the computational and the experimental stiffness data, while the fixed approach led to overestimation of the stiffness predictions. Using the new approach, the pattern of load distribution and the magnitude of the axial forces, experienced by each screw, were compared between the locked plating and far cortical locking constructs. The computational models suggested that under more severe loading conditions, far cortical locking screws might be under higher risk of screw pull-out than the locking screws. The proposed approach for modelling the screw–bone interface can be applied to any fixation involved application of screws.
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Affiliation(s)
- Mehran Moazen
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
- School of Engineering, University of Hull, Hull, UK
| | - Jonathan H Mak
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Alison C Jones
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Zhongmin Jin
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
- State Key Laboratory for Manufacturing System Engineering, School of Mechanical Engineering, Xi’an Jiaotong University, Xi’an, P.R. of China
| | - Ruth K Wilcox
- Institute of Medical and Biological Engineering, University of Leeds, Leeds, UK
| | - Eleftherios Tsiridis
- Academic Department of Orthopaedic and Trauma, University of Leeds, Leeds, UK
- Division of Surgery, Department of Surgery and Cancer, Imperial College London, London, UK
- Academic Orthopaedics and Trauma Unit, Aristotle University Medical School, Thessaloniki, Greece
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18
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Caouette C, Yahia L, Bureau MN. Reduced stress shielding with limited micromotions using a carbon fibre composite biomimetic hip stem: a finite element model. Proc Inst Mech Eng H 2011; 225:907-19. [DOI: 10.1177/0954411911412465] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Total hip arthroplasty (THA) enjoys excellent rates of success in older patients, but younger patients are still at risk of aseptic loosening and bone resorption from stress shielding. One solution to the stress shielding problem is to use a hip stem with mechanical properties matching those of cortical bone. The objective of the present study was to investigate numerically the biomechanical performance of such a biomimetic hip stem based on a hydroxyapatite (HA)-coated carbon fibre composite. A finite element model (FEM) of the biomimetic stem was constructed. Contact elements were studied to model the bone–implant interface in a non-osseointegrated and osseointegrated state in the best way. Three static load cases representing slow walking, stair climbing, and gait in a healthy individual were considered. Stress shielding and bone–implant interface micromotions were evaluated and compared with the results of a similar FEM based on titanium alloy (Ti–6Al–4V). The composite stems allowed for reduced stress shielding when compared with a traditional Ti–6Al–4V stem. Micromotions were slightly higher with the composite stem, but remained below 40 μm on most of the HA-coated surface. It is concluded that a biomimetic composite stem might offer a better compromise between stress shielding and micromotions than the Ti–6Al–4V stem with the same external geometry.
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Affiliation(s)
- C Caouette
- Laboratory of Innovation and Analysis of Bioperformance (LIAB), École Polytechnique de Montréal, Montréal, Quebec, Canada
| | - L’H Yahia
- Laboratory of Innovation and Analysis of Bioperformance (LIAB), École Polytechnique de Montréal, Montréal, Quebec, Canada
| | - M N Bureau
- Industrial Materials Institute, National Research Council of Canada, Boucherville, Quebec, Canada
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Pal B, Gupta S, New AM. Design considerations for ceramic resurfaced femoral head: effect of interface characteristics on failure mechanisms. Comput Methods Biomech Biomed Engin 2010; 13:143-55. [DOI: 10.1080/10255840903067064] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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The Effects of Interfacial Conditions and Stem Length on Potential Failure Mechanisms in the Uncemented Resurfaced Femur. Ann Biomed Eng 2010; 38:2107-20. [DOI: 10.1007/s10439-010-0007-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2010] [Accepted: 03/09/2010] [Indexed: 10/19/2022]
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21
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Discretization error when using finite element models: Analysis and evaluation of an underestimated problem. J Biomech 2009; 42:1926-34. [DOI: 10.1016/j.jbiomech.2009.05.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 05/07/2009] [Accepted: 05/08/2009] [Indexed: 11/22/2022]
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Pal B, Gupta S, New AM. A numerical study of failure mechanisms in the cemented resurfaced femur: effects of interface characteristics and bone remodelling. Proc Inst Mech Eng H 2009; 223:471-84. [PMID: 19499837 DOI: 10.1243/09544119jeim488] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Failure mechanisms of the resurfaced femoral head include femoral neck fracture in the short-term and stress shielding and implant loosening in the long-term. In this study, finite element simulations of the resurfaced femur considering a debonded implant-cement interface, variable stem-bone interface conditions, and bone remodelling were used to study load transfer within the resurfaced femur and to investigate its relationship with known failure mechanisms. Realistic three-dimensional finite element models of an intact and resurfaced femur were used. Various conditions at the interface between the stem of the prosthesis and the bone were considered. Loading conditions included normal walking and stair climbing. For all stem-bone contact conditions, the tensile stresses in the cement mantle varied between 1 MPa and 5.4 MPa, except near the distal rim of the resurfacing component where they reached 5.4-7MPa. In the case of full stem-bone contact, high von Mises stresses (114-121MPa) were generated in the implant at the stem-cup junction. These stresses were considerably reduced (maximum von Mises stress, 76 MPa) where a gap was present at the stem-bone interface. Resurfacing led to strain shielding of the bone of the femoral head (20-75 per cent strain reductions) and periprosthetic bone resorption (50-80 per cent bone density reductions) for all interface stem-bone contact conditions. In the lateral femoral head and the proximal femoral shaft around the trochantric region, bone density reductions varied between 10 per cent and 50 per cent. Bone apposition was observed in the inferior-medial part of the femoral head and proximal femoral neck region. For full stem-bone contact, more load was transferred through the stem to the surrounding bone, exacerbating strain shielding. Although femoral hip resurfacing conserves bone stock at the primary operation, strain shielding and periprosthetic bone resorption might lead to eventual loosening over time. Post-operatively, the resurfacing procedure generated elevated strains (0.50-0.75 per cent strain) in the proximal femoral neck-component junction irrespective of the variation in interface conditions, indicating an initial risk of femoral neck fracture. Subsequent to bone remodelling, this strain concentration was considerably reduced (0.35-0.50 per cent strain), lowering the risk of neck fracture. In order to reduce the potential risk of neck fracture, patients should avoid activities which might induce high loading of the hip during the early post-operative period to allow the bone around the proximal femoral neck to remodel and heal.
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Affiliation(s)
- B Pal
- Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur, Kharagpur, West Bengal 721302, India
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Pettersen SH, Wik TS, Skallerud B. Subject specific finite element analysis of implant stability for a cementless femoral stem. Clin Biomech (Bristol, Avon) 2009; 24:480-7. [PMID: 19368993 DOI: 10.1016/j.clinbiomech.2009.03.009] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 03/15/2009] [Accepted: 03/16/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND The primary stability of a cementless implant is crucial to ensure long term stability through osseointegration. In the present study we have examined how subject specific finite element models can be used to evaluate the stability of a cementless femoral stem. METHODS Micromotion on the bone-implant interface of a cementless stem was measured experimentally in six human cadaver femurs. Subject specific finite element models were built from computed tomography of the same femurs, and used to simulate the same load scenario used experimentally. FINDINGS Both experimental measurements and numerical analyses showed a tendency of increased rotational stability for bigger implants. Good correlation was found between measurements and calculated values of axial rotation (R(2)=0.74, P<0.001). The finite element models produced interface micromotion of the same magnitude as measured experimentally, with micromotion generally below 40 microm. Bigger femoral stems were found to decrease the micromotion in the experimental measurements. This tendency could not be recognised in the interface micromotion from the finite element models. INTERPRETATION The finite element models showed limited success in predicting interfacial micromotion, but reproduced a similar pattern of rotational stability for the implants as seen experimentally. Since rotation in retroversion is often the main concern when studying implant stability, subject specific finite element models could be employed for pre-clinical evaluation of implants.
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Affiliation(s)
- Sune H Pettersen
- Department of Structural Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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24
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Risk of failure during gait for direct skeletal attachment of a femoral prosthesis: A finite element study. Med Eng Phys 2009; 31:595-600. [DOI: 10.1016/j.medengphy.2008.11.015] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 10/10/2008] [Accepted: 11/21/2008] [Indexed: 11/18/2022]
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Subject specific finite element analysis of stress shielding around a cementless femoral stem. Clin Biomech (Bristol, Avon) 2009; 24:196-202. [PMID: 19103468 DOI: 10.1016/j.clinbiomech.2008.11.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2008] [Revised: 10/08/2008] [Accepted: 11/12/2008] [Indexed: 02/07/2023]
Abstract
BACKGROUND Stress shielding around a femoral stem is usually assessed experimentally using composite or human cadaver femurs. In the present study we have explored the feasibility of using subject specific finite element models to determine stress shielding in operated femurs. METHODS Cortical strain was measured experimentally on seven human cadaver femurs, intact and implanted with a straight cementless prosthesis. Two load configurations were considered: single leg stance and stair climbing. Subject specific finite element models derived from computed tomography of the same femurs were analysed intact and with an implant. Principal cortical strain was used to validate the finite element models. Stress shielding was defined as the change in equivalent (von Mises) strain between pre- and post-operative femurs. FINDINGS Cortical strain predicted by the finite element analyses showed to be close to unity with the experimental observations for both intact (R2=0.94, slope=0.99), operated femurs (R2=0.86, slope=0.86) and stress shielding (R2=0.70, slope=0.90). In the proximal calcar area, the region most prone to periprosthetic remodelling, the finite element models were found to successfully reproduce the stress shielding observed experimentally. INTERPRETATION The study shows that subject specific finite element models manage to describe the stress shielding pattern measured in vitro in the different femurs. Finite element models based on actual human femurs (cadaver and/or patient) could thus be a useful tool in the pre-clinical evaluation of new implants.
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26
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Helgason B, Viceconti M, Rúnarsson TP, Brynjólfsson S. On the mechanical stability of porous coated press fit titanium implants: A finite element study of a pushout test. J Biomech 2008; 41:1675-81. [DOI: 10.1016/j.jbiomech.2008.03.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2007] [Revised: 01/28/2008] [Accepted: 03/13/2008] [Indexed: 11/25/2022]
Affiliation(s)
- Benedikt Helgason
- Department of Mechanical and Industrial Engineering, Faculty of Engineering, University of Iceland, Hjardarhagi 2-6, 107 Reykjavík, Iceland.
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27
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Abdul-Kadir MR, Hansen U, Klabunde R, Lucas D, Amis A. Finite element modelling of primary hip stem stability: the effect of interference fit. J Biomech 2007; 41:587-94. [PMID: 18036531 DOI: 10.1016/j.jbiomech.2007.10.009] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 08/30/2007] [Accepted: 10/13/2007] [Indexed: 10/22/2022]
Abstract
The most commonly reported complications related to cementless hip stems are loosening and thigh pain; both of these have been attributed to high levels of relative micromotion at the bone-implant interface due to insufficient primary fixation. Primary fixation is believed by many to rely on achieving a sufficient interference fit between the implant and the bone. However, attempting to achieve a high interference fit not infrequently leads to femoral canal fracture either intra-operatively or soon after. The appropriate range of diametrical interference fit that ensures primary stability without risking femoral fracture is not well understood. In this study, a finite element model was constructed to predict micromotion and, therefore, instability of femoral stems. The model was correlated with an in vitro micromotion experiment carried out on four cadaver femurs. It was confirmed that interference fit has a very significant effect on micromotion and ignoring this parameter in an analysis of primary stability is likely to underestimate the stability of the stem. Furthermore, it was predicted that the optimal level of interference fit is around 50 microm as this is sufficient to achieve good primary fixation while having a safety factor of 2 against femoral canal fracture. This result is of clinical relevance as it indicates a recommendation for the surgeon to err on the side of a low interference fit rather than risking femoral fracture.
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28
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Anderson AE, Ellis BJ, Weiss JA. Verification, validation and sensitivity studies in computational biomechanics. Comput Methods Biomech Biomed Engin 2007; 10:171-84. [PMID: 17558646 PMCID: PMC3361760 DOI: 10.1080/10255840601160484] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Computational techniques and software for the analysis of problems in mechanics have naturally moved from their origins in the traditional engineering disciplines to the study of cell, tissue and organ biomechanics. Increasingly complex models have been developed to describe and predict the mechanical behavior of such biological systems. While the availability of advanced computational tools has led to exciting research advances in the field, the utility of these models is often the subject of criticism due to inadequate model verification and validation (V&V). The objective of this review is to present the concepts of verification, validation and sensitivity studies with regard to the construction, analysis and interpretation of models in computational biomechanics. Specific examples from the field are discussed. It is hoped that this review will serve as a guide to the use of V&V principles in the field of computational biomechanics, thereby improving the peer acceptance of studies that use computational modeling techniques.
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Affiliation(s)
| | | | - Jeffrey A. Weiss
- Corresponding Author: Jeffrey A. Weiss, Department of Bioengineering, University of Utah, 50 South Central Campus Drive, Room 2480, Salt Lake City, Utah 84112-9202, Phone: 1 801 587-7833, Fax: 1 801 585-5361,
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29
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Zhang M, Don X, Fa Y. Stress analysis of osseointegrated transfemoral prosthesis: a finite element model. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2005:4060-3. [PMID: 17281124 DOI: 10.1109/iembs.2005.1615354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In this study a three dimensional finite element model was established to analyze the interfacial stress distribution in the osseointegrated transfemoral prosthesis. The effects of implant length and screw pitch on the stress and strain distributions were analyzed in terms of bonded and contact bone-implant interfaces. The influences of the contact parameters, contact stiffness and friction coefficient, of the model were evaluated. The results show the differences on the stress distributions at the bone-implant interface in the models with different implant lengths and thread pitches. The highest stress in the model with contact interface is higher than that in the bonded model.
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Affiliation(s)
- Ming Zhang
- Jockey Club Rehabilitation Eng. Center, Hong Kong Polytech. Univ
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30
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Reggiani B, Cristofolini L, Varini E, Viceconti M. Predicting the subject-specific primary stability of cementless implants during pre-operative planning: Preliminary validation of subject-specific finite-element models. J Biomech 2007; 40:2552-8. [PMID: 17229427 DOI: 10.1016/j.jbiomech.2006.10.042] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2005] [Accepted: 10/30/2006] [Indexed: 11/18/2022]
Abstract
Pre-operative planning help the surgeon in taking the proper clinical decision. The ultimate goal of this work is to develop numerical models that allow the surgeon to estimate the primary stability during the pre-operative planning session. The present study was aimed to validate finite-element (FE) models accounting for patient and prosthetic size and position as planned by the surgeon. For this purpose, the FE model of a cadaveric femur was generated starting from the CT scan and the anatomical position of a cementless stem derived by a skilled surgeon using a pre-operative CT-based planning simulation software. In-vitro experimental measurements were used as benchmark problem to validate the bone-implant relative micromotions predicted by the patient-specific FE model. A maximum torque in internal rotation of 11.4 Nm was applied to the proximal part of the hip stem. The error on the maximum predicted micromotion was 12% of the peak micromotion measured experimentally. The average error over the entire range of applied torques was only 7% of peak measurement. Hence, the present study confirms that it is possible to accurately predict the level of primary stability achieved for cementless stems using numerical models that account for patient specificity and surgical variability.
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Affiliation(s)
- B Reggiani
- DIEM - Dipartimento di Ingegneria delle Costruzioni Meccaniche, Nucleari, Aeronautiche e di Metallurgia, Università degli Studi di Bologna, Viale Risorgimento 2, 40136, Bologna, Italy.
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31
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Viceconti M, Brusi G, Pancanti A, Cristofolini L. Primary stability of an anatomical cementless hip stem: A statistical analysis. J Biomech 2006; 39:1169-79. [PMID: 15927191 DOI: 10.1016/j.jbiomech.2005.03.024] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2004] [Accepted: 03/28/2005] [Indexed: 11/28/2022]
Abstract
The primary stability that the surgeon can achieve during surgery is a determinant of the clinical success of cementless implants. Thus, estimating what level of primary stability can be obtained with a new design is an important aspect of pre-clinical evaluation. The primary stability of a cementless hip stem is not only affected by the implant design, but also by other factors such as the mechanical quality of the host bone, the presence of gaps around the bone-implant interface, the body weight of the patient, and the size of the implant. Even the most extensive experimental study can only explore a small sub-set of all possible combinations found in vivo. To overcome this limitation, we propose a combination of experimental and numerical methods. The primary stability of a cementless anatomical stem is assessed in vitro. A finite element model is developed to accurately replicate the same experiment. The model is then parameterised over the various factors that affect the primary stability, and used in a Monte Carlo scheme to assess the primary stability over a simulated population. In this study, the method was used to investigate the mechanical stability of an anatomical cementless stem over more than 1000 simulated cases. Twenty cases were found macroscopically unstable, due to a combination of unfavourable conditions. The rest of the Monte Carlo sample showed on average a peak micromotion under stair climbing loading of 206 +/- 159 microm. The proposed method can be used to evaluate new designs in conditions more representative of the variability in clinical practice.
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Affiliation(s)
- Marco Viceconti
- Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Via di Barbiano, 1/10, 40136 Bologna, Italy.
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32
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Barker DS, Tanner KE, Ryd L. A Circumferentially Flanged Tibial Tray Minimizes Bone-Tray Shear Micromotion. Proc Inst Mech Eng H 2005; 219:449-56. [PMID: 16312104 DOI: 10.1243/095441105x34464] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Aseptic loosening of the tibial component is the major complication of total knee arthroplasty. There is an association between early excessive shear micromotion between the bone and the tray of the tibial component and late aseptic loosening. Using non-linear finite element analysis, whether a tibial tray with a circumferentially flanged rim and a mating cut in the proximal tibia could minimize bone-tray shear micromotion was considered. fifteen competing tray designs with various degrees of flange curvature were assessed with the aim of minimizing bone-tray shear micromotion. A trade-off was found between reducing micromotion and increasing peripheral cancellous bone stresses. It was found that, within the limitations of the study, there was a theoretical design that could virtually eliminate micromotion due to axial loads, with minimal bone removal and without the use of screws or pegs.
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Affiliation(s)
- D S Barker
- Department of Orthopaedics, Lund University Hospital, Lund, Sweden.
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33
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Viceconti M, Ricci S, Pancanti A, Cappello A. Numerical model to predict the longterm mechanical stability of cementless orthopaedic implants. Med Biol Eng Comput 2004; 42:747-53. [PMID: 15587465 DOI: 10.1007/bf02345207] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The objective of this research was to develop a purely biomechanical model, intended to predict the long-term secondary stability of the implant starting from the biomechanical stability immediately after the operation. A continuous rule-based adaptation scheme was formulated as a dynamic system, and the work verified if such a model produced unique and clinically meaningful solutions. It also investigated whether this continuous model provided results comparable with those of a simpler, discrete-states model used in a previous study. The proposed model showed stable convergence behaviour with all investigated initial conditions, with oscillatory behaviour limited to the first steps of the simulation. The results obtained with the wide range of initial conditions support the hypothesis of the existence and uniqueness of the solution for all initial conditions. The differences between the continuous model and the simpler and more efficient finite-states model were found to be extremely modest (less than 4% over the predicted bonded area). Because of these minimal differences, the use of the much faster finite-states model is recommended to investigate asymptotic conditions, and the continuous model described should be used to investigate the evolution over time of the adaptive process.
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Affiliation(s)
- M Viceconti
- Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, Bologna, Italy.
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34
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Fernandes PR, Folgado J, Ruben RB. Shape optimization of a cementless hip stem for a minimum of interface stress and displacement. Comput Methods Biomech Biomed Engin 2004; 7:51-61. [PMID: 14965880 DOI: 10.1080/10255840410001661637] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The primary stem stability is an essential factor for success of cementless hip stems. A correct choice of the stem geometry can improve the stem stability and, consequently, increase the life time of a hip implant. In this work, it is proposed a computational model for shape optimization of cementless hip stems. The optimization problem is formulated by the minimization of relative displacement and stress on bone/stem interface using a multi-criteria objective function. Also multiple loads are considered to incorporate several daily life activities. Design variables are parameters that characterize the geometry of selected cross sections, which are subject to geometric constraints to ensure a clinically admissible shape. The stem/bone set is considered a structure in equilibrium with contact conditions on interface. The contact formulation allows us to analyze different lengths of porous coating. The optimization problem is solved numerically by a steepest descent method. The interface stress and relative displacement are obtained solving the contact problem by the finite element method. Numerical examples are presented for a two-dimensional model of a hip stem, however, the formulation is general and can be applied to the three-dimensional case. The model gives indications about the relation between shape, porous coating and prosthesis stability.
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35
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Simon U, Augat P, Ignatius A, Claes L. Influence of the stiffness of bone defect implants on the mechanical conditions at the interface--a finite element analysis with contact. J Biomech 2003; 36:1079-86. [PMID: 12831732 DOI: 10.1016/s0021-9290(03)00114-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The study focused on the influence of the implant material stiffness on stress distribution and micromotion at the interface of bone defect implants. We hypothesized that a low-stiffness implant with a modulus closer to that of the surrounding trabecular bone would yield a more homogeneous stress distribution and less micromotion at the interface with the bony bed. To prove this hypothesis we generated a three-dimensional, non-linear, anisotropic finite element (FE) model. The FE model corresponded to a previously developed animal model in sheep. A prismatic implant filled a standardized defect in the load-bearing area of the trabecular bone beneath the tibial plateau. The interface was described by face-to-face contact elements, which allow press fits, friction, sliding, and gapping. We assumed a physiological load condition and calculated contact pressures, shear stresses, and shear movements at the interface for two implants of different stiffness (titanium: E=110GPa; composite: E=2.2GPa). The FE model showed that the stress distribution was more homogeneous for the low-stiffness implant. The maximum pressure for the composite implant (2.1 MPa) was lower than for the titanium implant (5.6 MPa). Contrary to our hypothesis, we found more micromotion for the composite (up to 6 microm) than for the titanium implant (up to 4.5 microm). However, for both implants peak stresses and micromotion were in a range that predicts adequate conditions for the osseointegration. This was confirmed by the histological results from the animal studies.
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Affiliation(s)
- U Simon
- Institute of Orthopaedic Research and Biomechanics, University of Ulm, Helmholtzstrasse 14, 89081 Ulm, Germany.
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36
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Pancanti A, Bernakiewicz M, Viceconti M. The primary stability of a cementless stem varies between subjects as much as between activities. J Biomech 2003; 36:777-85. [PMID: 12742445 DOI: 10.1016/s0021-9290(03)00011-3] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The rehabilitation program adopted immediately after a cementless total hip replacement is a very important factor, because of the known relationship between osseointegration and implant micromotion. The present study was aimed to evaluate which type of task is the most critical in terms of bone-implant relative micromotion. Both inter-task and inter-subject variability were taken into account to verify if the movement strategy could be determinant on this assessment. A previously validated finite element model was used to predict the peak total micromovements over the entire bone-implant contact surface in four different patients, performing nine different tasks, using published data on joint forces recorded by instrumented hip prostheses. The results predicted by the various simulations suggest that while stair climbing is surely a critical task for primary stability, for some subjects other tasks may be as critical as stair climbing. From a variance analysis for simple crossover design on the predicted peak micromotion, the inter-subject variability had much more influence on the primary stability of cementless implant than the inter-task variability. Even if the results of Patient IBL, who was reported to have difficulties to perform any activities in a normal way, were excluded from the statistical analysis, the inter-subject variability remained still higher than the inter-task variability. The results obtained from simulations suggest that the strategy the hip replacement patient adopts to perform a given motor task, may be, for the implant stability, equally or even more critical than the type of motor task performed.
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Affiliation(s)
- Alberto Pancanti
- Laboratorio di Tecnologia Medica, Istituti Ortopedici Rizzoli, via di Barbiano 1/10, Bologna 40136, Italy.
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