Finite Element Assessment of a Porous Tibial Implant Design Using Rhombic Dodecahedron Structure

2021 ◽  
Vol 318 ◽  
pp. 71-81
Author(s):  
Basma Eltlhawy ◽  
Tawfik El-Midany ◽  
Noha Fouda ◽  
Ibrahim Eldesouky
Keyword(s):  
Finite Element ◽  
Clinical Performance ◽  
Bone Ingrowth ◽  
Maximum Shear Stress ◽  
Compressive Loading ◽  
Stress Shielding ◽  
Titanium Implant ◽  
Implant Design ◽  
Implant Fixation ◽  
Rhombic Dodecahedron

The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve implant fixation.

scholarly journals Finite-element analysis of the influence of tibial implant fixation design of total ankle replacement on bone–implant interfacial biomechanical performance

2020 ◽  
Vol 28 (3) ◽  
pp. 230949902096612
Author(s):  
Jian Yu ◽  
Chao Zhang ◽  
Wen-Ming Chen ◽  
Dahang Zhao ◽  
Pengfei chu ◽  
...  
Keyword(s):  
Finite Element ◽  
Total Ankle Replacement ◽  
Implant Design ◽  
Fixation Method ◽  
Implant Loosening ◽  
Implant Fixation ◽  
Bone Resection ◽  
Bone Implant ◽  
Initial Stability ◽  
Ankle Replacement

Purpose: Implant loosening in tibia after primary total ankle replacement (TAR) is one of the common postoperative problems in TAR. Innovations in implant structure design may ideally reduce micromotion at the bone–implant interface and enhance the bone-implant fixation and initial stability, thus eventually prevents long-term implant loosening. This study aimed to investigate (1) biomechanical characteristics at the bone–implant interface and (2) the influence of design features, such as radius, height, and length. Methods: A total of 101 finite-element models were created based on four commercially available implants. The models predicted micromotion at the bone–implant interface, and we investigated the impact of structural parameters, such as radius, length, and height. Results: Our results suggested that stem-type implants generally required the highest volume of bone resection before implantation, while peg-type implants required the lowest. Compared with central fixation features (stem and keel), peripherally distributed geometries (bar and peg) were associated with lower initial micromotions. The initial stability of all types of implant design can be optimized by decreasing fixation size, such as reducing the radius of the bars and pegs and lowering the height. Conclusion: Peg-type tibial implant design may be a promising fixation method, which is required with a minimum bone resection volume and yielded minimum micromotion under an extreme axial loading scenario. Present models can serve as a useful platform to build upon to help physicians or engineers when making incremental improvements related to implant design.

scholarly journals Long-term bone remodelling around ‘legendary’ cementless femoral stems

2018 ◽  
Vol 3 (2) ◽  
pp. 45-57 ◽  
Author(s):  
Charles Rivière ◽  
Guido Grappiolo ◽  
Charles A. Engh ◽  
Jean-Pierre Vidalain ◽  
Antonia-F. Chen ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Remodelling ◽  
Bone Ingrowth ◽  
Stress Shielding ◽  
Implant Design ◽  
Periprosthetic Bone ◽  
Femoral Stems ◽  
Periprosthetic Bone Loss ◽  
Load Pattern

Bone remodelling around a stem is an unavoidable long-term physiological process highly related to implant design. For some predisposed patients, it can lead to periprosthetic bone loss secondary to severe stress-shielding, which is thought to be detrimental by contributing to late loosening, late periprosthetic fracture, and thus rendering revision surgery more complicated. However, these concerns remain theoretical, since late loosening has yet to be documented among bone ingrowth cementless stems demonstrating periprosthetic bone loss associated with stress-shielding. Because none of the stems replicate the physiological load pattern on the proximal femur, each stem design is associated with a specific load pattern leading to specific adaptive periprosthetic bone remodelling. In their daily practice, orthopaedic surgeons need to differentiate physiological long-term bone remodelling patterns from pathological conditions such as loosening, sepsis or osteolysis. To aid in that process, we decided to clarify the behaviour of the five most used femoral stems. In order to provide translational knowledge, we decided to gather the designers’ and experts’ knowledge and experience related to the design rationale and the long-term bone remodelling of the following femoral stems we deemed ‘legendary’ and still commonly used: Corail (Depuy); Taperloc (Biomet); AML (Depuy); Alloclassic (Zimmer); and CLS-Spotorno (Zimmer).Cite this article: EFORT Open Rev 2018;3:45-57. DOI: 10.1302/2058-5241.3.170024

scholarly journals A validated finite element study of stress shielding in a novel hybrid knee implant

2021 ◽  
Author(s):  
Ziauddin Mahboob
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Finite Element Model ◽  
Bone Tissue ◽  
Stress Shielding ◽  
Stress Transfer ◽  
Element Model ◽  
Implant Design ◽  
Polyamide 12 ◽  
Compressive Loads

This study (1) proposes a hybrid knee implant design to improve stress transfer to bone tissue in the distal femur by modifying a conventional femoral implant to include a layer of carbon fibre reinforced polyamide 12, and (2) develops a finite element model of the prosthetic knee joint, validated by comparison with a parallel experimental study. The Duracon knee system was used in the experimental study, and its geometry was modelled using CAD software. Synthetic bone replicas were used instead of cadaveric specimens in the experiments. The strains generated on the femur and implant surfaces were measured under axial compressive loads of 2000 N and 3000 N. A mesh of 105795 nodes was needed to obtain sufficient accuracy in the finite element model, which reproduced the experimental reading within 10-23% in six of the eight test locations. The model of the proposed hybrid design showed considerable improvements in stress transfer to the bone tissue at three test flexion angles of 0°, 20°, and 60°.

scholarly journals Finite Element Analysis of Porous Ti-6Al-4V Alloy Structures for Biomedical Applications

2021 ◽  
Vol 2070 (1) ◽  
pp. 012224
Author(s):  
N Ganesh ◽  
S Rambabu
Keyword(s):  
Finite Element ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Bone Ingrowth ◽  
Stress Shielding ◽  
Shielding Effect ◽  
Element Analysis ◽  
Human Cortical Bone ◽  
Porous Ti ◽  
Manufacturing Technologies

Abstract In this article, design and finite element simulation of porous Ti-6Al-4V alloy structures was presented. Typically, titanium and titanium alloy implants can be manufactured with required pore size and porosity volume by using powder bed fusion techniques due to advancement in additive manufacturing technologies. However, the mismatch of elastic modulus between human cortical bone and the dense Ti-6Al-4V alloy implant resulted in stress shielding which accelerate the implant failure. The porous implant structures help in reduce the mismatch of elastic modulus between the cortical bone and implant structure and also improve the bone ingrowth. Hence, the present work focuses on design of Ti-6Al-4V alloy porous structures with various porosities ranging from 10% to 70% and simulated to determine the elastic modulus suitable for human cortical bone. The sample with 45% porosity is found to be best suited for replacement of cortical bone with elastic modulus of 74Gpa, preventing stress shielding effect and enhanced chances of bone ingrowth.

Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect

2017 ◽  
Vol 231 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Gurunathan Saravana Kumar ◽  
Subin Philip George
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Elastic Modulus ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Implant Design ◽  
Element Analysis ◽  
Von Mises ◽  
Reducing Stress

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress–strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

scholarly journals A validated finite element study of stress shielding in a novel hybrid knee implant

2021 ◽  
Author(s):  
Ziauddin Mahboob
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Finite Element Model ◽  
Bone Tissue ◽  
Stress Shielding ◽  
Stress Transfer ◽  
Element Model ◽  
Implant Design ◽  
Polyamide 12 ◽  
Compressive Loads

This study (1) proposes a hybrid knee implant design to improve stress transfer to bone tissue in the distal femur by modifying a conventional femoral implant to include a layer of carbon fibre reinforced polyamide 12, and (2) develops a finite element model of the prosthetic knee joint, validated by comparison with a parallel experimental study. The Duracon knee system was used in the experimental study, and its geometry was modelled using CAD software. Synthetic bone replicas were used instead of cadaveric specimens in the experiments. The strains generated on the femur and implant surfaces were measured under axial compressive loads of 2000 N and 3000 N. A mesh of 105795 nodes was needed to obtain sufficient accuracy in the finite element model, which reproduced the experimental reading within 10-23% in six of the eight test locations. The model of the proposed hybrid design showed considerable improvements in stress transfer to the bone tissue at three test flexion angles of 0°, 20°, and 60°.

scholarly journals Patient Specific Finite Element Modeling of Shoulder Implant Based on CT scan: The Concept of Modelling Explained

2021 ◽  
Author(s):  
Kocsis György ◽  
Gabor Henap
Keyword(s):  
Finite Element ◽  
Ct Scan ◽  
Mass Density ◽  
Continuous Distribution ◽  
Stress Shielding ◽  
Material Model ◽  
Implant Design ◽  
Patient Specific ◽  
Finite Element Procedure ◽  
Continuous Mass

Abstract The following work introduces a method to carry out patient specific implant design based on computer tomography (CT) imaging technique. Point cloud bone model and the solid model creation process is described in detail. Using the radiodensity level of the CT-scan the continuous distribution of the elastic properties of the bone is also been recorded and used for the material model of the finite element procedure. For this purpose, a continuous mass density – elastic modulus curve is suggested, based on previous results in the literature. Stress shielding poses a serious issue regarding the survival of an implant. Strain energy density (SED) is a good indicator of the effects that drive the remodeling. Based on local SED difference caused by the implant this phenomenon can be quantified and visualized. This makes it possible to classify or redesign the implant in order to minimize the potential bone loss caused by the altered stress state.

scholarly journals Biomechanical Behavior of Bioactive Material in Dental Implant: A Three-Dimensional Finite Element Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Vathsala Patil ◽  
Nithesh Naik ◽  
Srikanth Gadicherla ◽  
Komal Smriti ◽  
Adithya Raju ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Graphene Oxide ◽  
Titanium Implant ◽  
Von Mises Stress ◽  
Implant Design ◽  
Element Analysis ◽  
Von Mises ◽  
Implant System ◽  
The Impact

Dental implants are widely accepted for the rehabilitation of missing teeth due to their aesthetic compliance, functional ability, and great survival rate. The various components in implant design like thread design, thread angle, pitch, and material used for manufacturing play a critical role in its success. Understanding these influencing factors and implementing them properly in implant design can reduce cases of potential implant failure. Recently, finite element analysis (FEA) is being widely used in the field of health sciences to solve problems in designing medical devices. It provides valid and accurate assessment in the clinical and in vitro analysis. Hence, this study was conducted to evaluate the impact of thread design of the implant and 3 different bioactive materials, titanium alloy, graphene, and reduced graphene oxide (rGO) on stress, strain, and deformation in the implant system using FEA. In this study, the FEA model of the bones and the tissues are modeled as homogeneous, isotropic, and linearly elastic material with a titanium implant system with an assumption of it 100% osseointegrated into the bone. The titanium was functionalized with graphene and graphene oxide. A modeling software tool Catia® and Ansys Workbench® is used to perform the analysis and evaluate the von Mises stress distribution, strain, and deformation at the implant and implant-cortical bone interface. The results showed that the titanium implant with a surface coating of graphene oxide exhibited better mechanical behavior than graphene, with mean von Mises stress of 39.64 MPa in pitch 1, 23.65 MPa in pitch 2, and 37.23 MPa in pitch 3. It also revealed that functionalizing the titanium implant will help in reducing the stress at the implant system. Overall, the study emphasizes the use of FEA analysis methods in solving various biomechanical issues about medical and dental devices, which can further open up for invivo study and their practical uses.

scholarly journals Experimental & FEM Analysis of Orthodontic Mini-Implant Design on Primary Stability

2021 ◽  
Vol 11 (12) ◽  
pp. 5461
Author(s):  
Elmedin Mešić ◽  
Enis Muratović ◽  
Lejla Redžepagić-Vražalica ◽  
Nedim Pervan ◽  
Adis J. Muminović ◽  
...  
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Primary Stability ◽  
Fem Analysis ◽  
Implant Design ◽  
Special Focus ◽  
Engineering System ◽  
Mini Implants ◽  
Pull Out ◽  
Computer Aided

The main objective of this research is to establish a connection between orthodontic mini-implant design, pull-out force and primary stability by comparing two commercial mini-implants or temporary anchorage devices, Tomas®-pin and Perfect Anchor. Mini-implant geometric analysis and quantification of bone characteristics are performed, whereupon experimental in vitro pull-out test is conducted. With the use of the CATIA (Computer Aided Three-dimensional Interactive Application) CAD (Computer Aided Design)/CAM (Computer Aided Manufacturing)/CAE (Computer Aided Engineering) system, 3D (Three-dimensional) geometric models of mini-implants and bone segments are created. Afterwards, those same models are imported into Abaqus software, where finite element models are generated with a special focus on material properties, boundary conditions and interactions. FEM (Finite Element Method) analysis is used to simulate the pull-out test. Then, the results of the structural analysis are compared with the experimental results. The FEM analysis results contain information about maximum stresses on implant–bone system caused due to the pull-out force. It is determined that the core diameter of a screw thread and conicity are the main factors of the mini-implant design that have a direct impact on primary stability. Additionally, stresses generated on the Tomas®-pin model are lower than stresses on Perfect Anchor, even though Tomas®-pin endures greater pull-out forces, the implant system with implemented Tomas®-pin still represents a more stressed system due to the uniform distribution of stresses with bigger values.

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