A Comparison Between Porous NiTi and Ti-6Al-4V Fixation Hardware on Bone Remodeling After a Reconstruction Surgery

2016 ◽  
Author(s):  
Bahram Raad ◽  
Narges Shayesteh Moghaddam ◽  
Mohammad Elahinia
Keyword(s):  
Density Distribution ◽  
Bone Remodeling ◽  
Niti Alloy ◽  
Healing Process ◽  
Stress Shielding ◽  
Element Model ◽  
Reconstruction Surgery ◽  
Porous Niti ◽  
Surrounding Bone ◽  
The Finite Element Model

The aim of this article is to investigate the effect of two different fixation hardware materials on bone remodeling after a mandibular reconstruction surgery and to restore the mandible’s function, healthy appearance, mastication, swallowing, breathing, and speech. The hypothesis is that using fixation hardware with stiffness close to that of the surrounding bone will result in a more successful healing process in the mandible bone. The finite element model includes the material properties and forces of the cancellous bone, cortical bone, ligaments, muscles, and teeth. The reconstruction surgery is modeled by including the fixation hardware and the grafted bone. In the sectioned mandible, to best mimic the geometry of the mandible, two single barrel grafts are placed at the top of each other to form a double barrel graft set. Two different materials were used as the mandibular fixation parts, stiff Ti-6Al-4V, and porous superelastic Nickel-Titanium (NiTi) alloys. A comparison of these two alloys demonstrates that using porous NiTi alloy as the fixation part results in a faster healing pace. Furthermore, the density distribution in the mandibular bone after the healing process is more similar to the normal mandible density distribution. The simulations results indicate that the porous superelastic NiTi fixation hardware transfers and distributes the existing forces on the mandible bone more favorably. The probability of stress shielding and/or stress concentration decrease. This type of fixation hardware, therefore, is more appropriate for mandible bone reconstruction surgery.

scholarly journals Secondary Stability of a Composite Biomimetic Cementless Hip Stem

2008 ◽  
Author(s):  
Christiane Caouette ◽  
Martin N. Bureau ◽  
L’Hocine Yahia
Keyword(s):  
Aseptic Loosening ◽  
Hip Replacement ◽  
Wear Debris ◽  
Stress Shielding ◽  
Element Model ◽  
Bone Implant ◽  
The World ◽  
Hip Stems ◽  
Surrounding Bone ◽  
Secondary Stability

Total hip replacement is one of the most successful and frequent surgery in the world; over a million of these procedures are performed every year, and the numbers are growing with the ageing of the general population. The patients who receive these implants also are younger nowadays. Major problems however still subsist with traditional hip stems: aseptic loosening is a common cause of revision surgery. The main causes of aseptic loosening are both mechanical and biological in origin. Mechanical causes include stress shielding and micromotions at bone-implant interface, and biological causes are mainly osteolysis triggered by wear debris formation and bone remodeling. To remedy the mechanical issues, a biomimetic concept was developed (patent pending): an osseointegrated stem with mechanical properties close to those of the surrounding bone would avoid both stress shielding and micromotions phenomena. To evaluate this concept, a finite element model (FEM) was developed and used to simulate bone resorption, stress shielding and micromotions [1]. The preliminary results were promising as those problems were significantly reduced with the new prosthesis, but the model still remained to be proved accurate; its bone-implant interface was of particular interest because of its decisive influence on micromotions.

Evaluating a NiTi Implant Under Realistic Loads: A Simulation Study

2016 ◽  
Author(s):  
Amirhesam Amerinatanzi ◽  
Narges Shayesteh Moghaddam ◽  
Hamdy Ibrahim ◽  
Mohammad Elahinia
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Finite Element Model ◽  
Cortical Bone ◽  
Reconstructive Surgery ◽  
Stress Shielding ◽  
Element Model ◽  
Patient Specific ◽  
Porous Niti ◽  
Biocompatible Alloys

Additive manufacturing (i.e. 3D printing) has only recently be shown as a well-established technology to create complex shapes and porous structures from different biocompatible metal powder such as titanium, nitinol, and stainless steel alloys. This allows for manufacturing bone fixation hardware with patient-specific geometry and properties (e.g. density and mechanical properties) directly from CAD files. Superelastic NiTi is one of the most biocompatible alloys with high shock absorption and biomimetic hysteresis behavior. More importantly, NiTi has the lowest stiffness (36–68 GPa) among all biocompatible alloys [1]. The stiffness of NiTi can further be reduced, to the level of the cortical bone (10–31.2 GPa), by introducing engineered porosity using additive manufacturing [2–4]. The low level of fixation stiffness allows for bone to receive a stress profile close to that of healthy bone during the healing period. This enhances the bone remodeling process (Wolf’s Law) which primarily driven by the pattern of stress. Also, this match in the stiffness of bone and fixation mitigates the problem of stress shielding and detrimental stress concentrations. Stress shielding is a known problem for the currently in-use Ti-6Al-4V fixation hardware. The high stiffness of Ti-6Al-4V (112 GPa) compared to bone results in the absence of mechanical loading on the adjacent bone that causes loss of bone mass and density and subsequently bone/implant failure. We have proposed additively manufactured porous NiTi fixation hardware with a patient-specific stiffness to be used for the mandibular reconstructive surgery (MRS). In MRS, the use of metallic fixation hardware and double barrel fibula graft is the standard methodology to restore the mandible functionality and aesthetic. A validated finite element model was developed from a dried cadaveric mandible using CT scan data. The model simulated a patient’s mandible after mandibular reconstructive surgery to compare the performance of the conventional Ti-6Al-4V fixation hardware with the proposed one (porous superelastic NiTi fixation plates). An optimized level of porosity was determined to match the NiTi equivalent stiffness to that of a resected bone, then it was imposed to the simulated fixation plates. Moreover, the material property of superelastic NiTi was simulated by using a validated customized code. The code was calibrated by using DSC analysis and mechanical tests on several prepared bulk samples of Ni-rich NiTi. The model was run under common activities such as chewing by considering different levels of the applied fastening torques on screws. The results show a higher level of stress distribution on mandible cortical bone in the case of using NiTi fixation plates. Based on wolf’s law it can lead to a lower level of stress shielding on the grafted bone and over time bone can remodel itself. Moreover, the results suggest an optimum fastening torque for fastening the screws for the superelastic fixations causes more normal distribution of stress on the bone similar to that for the healthy mandible. Finally, we successfully fabricated the stiffness-matched porous NiTi fixation plates using selective laser melting technique, and they were mounted on the dried cadaveric mandible used to create the finite element model.

scholarly journals Design, Optimization, and Evaluation of Additively Manufactured Vintiles Cellular Structure for Acetabular Cup Implant

Processes ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 25 ◽  
Author(s):  
Kalayu Mekonen Abate ◽  
Aamer Nazir ◽  
Jia-En Chen ◽  
Jeng-Ywan Jeng
Keyword(s):  
Finite Element ◽  
Cellular Structure ◽  
Mechanical Performance ◽  
Stress Shielding ◽  
Element Model ◽  
Bone Cell ◽  
Acetabular Cup ◽  
Element Analysis ◽  
Internal Pore ◽  
The Finite Element Model

Cellular materials with very highly regulated micro-architectures are promising applicant materials for orthopedic medical uses while requiring implants or substituting for bone due to their ability to promote increased cell proliferation and osseointegration. This study focuses on the design of an acetabular cup (AC) cellular implant which was built using a vintiles cellular structure with an internal porosity of 56–87.9% and internal pore dimensions in the range of 600–1200 μm. The AC implant was then optimized for improving mechanical performance to reduce stress shielding by adjusting the porosity to produce stiffness (elastic modulus) to match with the bone, and allowing for bone cell ingrowth. The optimized and non-optimized AC cellular implant was fabricated using the SLM additive manufacturing process. Simulation (finite element analysis, FEA) was carried out and all cellular implants are finally tested under static loading conditions. The result showed that on the finite element model of an optimized implant, cellular has shown 69% higher stiffness than non-optimized. It has been confirmed by experimental work shown that the optimized cellular implant has a 71% higher ultimate compressive strength than the non-optimized counterpart. Finally, we developed an AC implant with mechanical performance adequately close to that of human bone.

scholarly journals Biomechanical Evaluation Of Periprosthetic Femoral Fracture Fixation

2021 ◽  
Author(s):  
Seung Y.R. Kim
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Stress Shielding ◽  
Element Model ◽  
The Other ◽  
Bone Plate ◽  
Shielding Effect ◽  
Fixation Method ◽  
Periprosthetic Femoral Fracture ◽  
The Finite Element Model

This study proposes a bone plate fixation method to reduce the stress shielding effect on the fractured periprosthetic femur fixed with a metallic bone plate. The goal of this study is to design the finite element models of 5 bone plate attachment configurations applied to the periprosthetic femur fractured at 2 different levels (one with simple transverse fracture at mid-shaft with 1mm gap, and the other with 5mm gap at the fracture site simulating bone loss), and to validate the results by comparing with the experimental study. The average stiffness of the intact femur construct was 2502 N/mm which decreased to 1803 N/mm and 801 N/mm for a 1mm and 5mm gap construct, respectively. The finite element model predicted the stiffness results of the experiments within 10% for the 1mm gap fracture case. The finite element model was less reliable when used to predict the stiffness values in the 5mm gap fracture case. The construct fixed only with cables in the proximal femur resulted in the least amount of stress shielding while maintaining a similar level of stiffness compared to the other configurations.

scholarly journals Biomechanical Evaluation Of Periprosthetic Femoral Fracture Fixation

2021 ◽  
Author(s):  
Seung Y.R. Kim
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Stress Shielding ◽  
Element Model ◽  
The Other ◽  
Bone Plate ◽  
Shielding Effect ◽  
Fixation Method ◽  
Periprosthetic Femoral Fracture ◽  
The Finite Element Model

This study proposes a bone plate fixation method to reduce the stress shielding effect on the fractured periprosthetic femur fixed with a metallic bone plate. The goal of this study is to design the finite element models of 5 bone plate attachment configurations applied to the periprosthetic femur fractured at 2 different levels (one with simple transverse fracture at mid-shaft with 1mm gap, and the other with 5mm gap at the fracture site simulating bone loss), and to validate the results by comparing with the experimental study. The average stiffness of the intact femur construct was 2502 N/mm which decreased to 1803 N/mm and 801 N/mm for a 1mm and 5mm gap construct, respectively. The finite element model predicted the stiffness results of the experiments within 10% for the 1mm gap fracture case. The finite element model was less reliable when used to predict the stiffness values in the 5mm gap fracture case. The construct fixed only with cables in the proximal femur resulted in the least amount of stress shielding while maintaining a similar level of stiffness compared to the other configurations.

Redrawing Operation a Star Shape from Cylindrical Shape Using Experimental and FE Analysis

2020 ◽  
Vol 38 (1A) ◽  
pp. 25-32
Author(s):  
Waleed Kh. Jawad ◽  
Ali T. Ikal
Keyword(s):  
Finite Element ◽  
Effective Strain ◽  
Element Model ◽  
Cylindrical Shape ◽  
Element Analysis ◽  
Punch Force ◽  
Maximum Value ◽  
Element Simulation ◽  
Blank Sheet ◽  
The Finite Element Model

The aim of this paper is to design and fabricate a star die and a cylindrical die to produce a star shape by redrawing the cylindrical shape and comparing it to the conventional method of producing a star cup drawn from the circular blank sheet using experimental (EXP) and finite element simulation (FES). The redrawing and drawing process was done to produce a star cup with the dimension of (41.5 × 34.69mm), and (30 mm). The finite element model is performed via mechanical APDL ANSYS18.0 to modulate the redrawing and drawing operation. The results of finite element analysis were compared with the experimental results and it is found that the maximum punch force (39.12KN) recorded with the production of a star shape drawn from the circular blank sheet when comparing the punch force (32.33 KN) recorded when redrawing the cylindrical shape into a star shape. This is due to the exposure of the cup produced drawn from the blank to the highest tensile stress. The highest value of the effective stress (709MPa) and effective strain (0.751) recorded with the star shape drawn from a circular blank sheet. The maximum value of lamination (8.707%) is recorded at the cup curling (the concave area) with the first method compared to the maximum value of lamination (5.822%) recorded at the cup curling (the concave area) with the second method because of this exposure to the highest concentration of stresses. The best distribution of thickness, strains, and stresses when producing a star shape by

Durability Analysis of the Reduction Gear for High Speed Train Considering Driving Histories

2012 ◽  
Vol 586 ◽  
pp. 269-273
Author(s):  
Chul Su Kim ◽  
Gil Hyun Kang
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Element Model ◽  
Rolling Stock ◽  
Reduction Gear ◽  
High Speed Train ◽  
Analysis Software ◽  
Tractive Effort ◽  
Durability Analysis ◽  
The Finite Element Model

To assure the safety of the power bogies for train, it is important to perform the durability analysis of reduction gear considering a variation of velocity and traction motor capability. In this study, two types of applied load histories were constructed from driving histories considering the tractive effort and the train running curves by using dynamic analysis software (MSC.ADAMS). Moreover, this study was performed by evaluating fatigue damage of the reduction gears for rolling stock using durability analysis software (MSC.FATIGUE). The finite element model for evaluating the carburizing effect on the gear surface was used for predicting the fatigue life of the gears. The results showed that the fatigue life of the reduction gear would decrease with an increasing numbers of stops at station.

Analysis of Hydroelectric Unit’s Upper Bracket Based on Test and FEM

2014 ◽  
Vol 721 ◽  
pp. 131-134
Author(s):  
Mi Mi Xia ◽  
Yong Gang Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Element Model ◽  
The Finite Element Method ◽  
Ansys Software ◽  
Element Analysis ◽  
Hydroelectric Unit ◽  
The Finite Element Analysis ◽  
Strain Rosette ◽  
The Finite Element Model

To research the load upper bracket of Francis hydroelectric unit, then established the finite-element model, and analyzed the structure stress of 7 operating condition points with the ANSYS software. By the strain rosette test, acquired the data of stress-strain in the area of stress concentration of the upper bracket. The inaccuracy was considered below 5% by analyzing the contradistinction between the finite-element analysis and the test, and match the engineering precision and the test was reliable. The finite-element method could be used to judge the stress of the upper bracket, and it could provide reference for the Structural optimization and improvement too.

Dynamics Analysis of Industrial Sewing Machine Frame Based on FEA and Modal Experiment

2013 ◽  
Vol 419 ◽  
pp. 122-126
Author(s):  
Li Zhang ◽  
Chen Kai ◽  
Xue Jiao Wang
Keyword(s):  
3D Model ◽  
Element Model ◽  
Impact Testing ◽  
Testing System ◽  
Dynamics Analysis ◽  
Sewing Machine ◽  
Good Consistency ◽  
The Finite Element Model ◽  
Experiment Analysis ◽  
Abaqus Software

The industrial sewing machine frame is one of the most important components of the sewing machine system, so studying its dynamic characteristics is particularly important. In this paper, based on the 3D model, the theory modal analysis of the industrial sewing machine is conducted with ABAQUS software and the modal experiment analysis is carried out through LMS(Lab Impact Testing system). The experimental results are in good consistency, which shows that the finite element model built in the paper is reasonable. This paper provides theoretical reference for vibration and noise reduction of the industrial sewing machine.

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