scholarly journals Effect of Ring Material and Diameter on Orthopedic Implant Stability: External Fixation in Femur Bone

2018 ◽  
Vol 7 (4.26) ◽  
pp. 190 ◽  
Author(s):  
Nur Fatin Izzati Ibrahim ◽  
Ruslizam Daud ◽  
Muhammad Khairul Ali Hassan ◽  
Noor Ali Hassan ◽  
Noor Alia Md Zain ◽  
...  
Keyword(s):  
External Fixation ◽  
Von Mises Stress ◽  
Axial Stiffness ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Ring Diameter ◽  
The Stability ◽  
Von Mises ◽  
Fixation Frame ◽  
Ring Material

Axial stiffness is the most important factor in stability. It is known that any changes in the diameter of any components of the frame will either increase or decrease the axial stiffness of the fixation. The model of implant and bone will be variety as the variables changes. Current studies states that ring stability are one of the most important factors in ensuring fractured bones to have a successful re-union. In circular external fixation, the stability of the pin-bone interaction is influenced by the stability of the fixation frame where the major component is the rings. The objective is to study the finite element analysis (FEA) of the external fixator assembled in human diaphysis under compression force with different materials of the exoskeleton which are stainless steel, titanium alloy, magnesium alloy and carbon fiber. The results obtained show the mechanical strength of each material where it will be used to compare the value of von-Mises stress, stiffness and total deformation to acquire the best suitable ring diameter and material. Based on the result, as the diameter of the ring increases, the stiffness of the ring will be decreased. 

scholarly journals Effects of placement angle and direction of orthopedic force application on the stability of orthodontic miniscrews

2012 ◽  
Vol 83 (4) ◽  
pp. 667-673 ◽  
Author(s):  
Jihye Lee ◽  
Ji Young Kim ◽  
Yoon Jeong Choi ◽  
Kyung-Ho Kim ◽  
Chooryung J. Chung
Keyword(s):  
Cortical Bone ◽  
Lateral Force ◽  
Von Mises Stress ◽  
Biomechanical Stability ◽  
Element Analysis ◽  
Force Application ◽  
Pull Out ◽  
The Stability ◽  
Von Mises ◽  
Pull Out Strength

ABSTRACT Objectives: To evaluate the influence of placement angle and direction of orthopedic force application on the stability of miniscrews. Materials and Methods: Finite element analysis was performed using miniscrews inserted into supporting bone at angles of 90°, 60°, and 30° (P90°, P60°, and P30°). An orthopedic heavy force of 800 gf was applied to the heads of the miniscrews in four upward (U0°, U30°, U60°, U90°) or lateral (L0°, L30°, L60°, L90°) directions. In addition, pull-out strength of the miniscrews was measured with various force directions and cortical bone thicknesses. Results: Miniscrews with a placement angle of 30° (P30°) and 60° (P60°) showed a significant increase in maximum von Mises stress following the increase in lateral force vectors (U30°, U60°, U90°) compared to those with a placement angle of 90° (P90°). In accordance, the pull-out strength was higher with the axial upward force when compared to the upward force with lateral vectors. Maximum von Mises stress and displacement of the miniscrew increased as the angle of lateral force increased (L30°, L60°, L90°). However, a more dramatic increase in maximum von Mises stress was noted in P30° than in P60° and P90°. Conclusion: Placement of the miniscrew perpendicular to the cortical bone is advantageous in terms of biomechanical stability. Placement angles of less than 60° can reduce the stability of miniscrews when orthopedic forces are applied in various directions.

scholarly journals Effects of Attraction of Vacuum Extractors of Different Materials and Pressures on the Fetal Head During Delivery

2021 ◽  
Author(s):  
Yu-Hsuan Chen ◽  
Kuo-Min Su ◽  
Ming-Tzu Tsai ◽  
Chi-Kung Lin ◽  
Cheng-Chang Chang ◽  
...  
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Von Mises Stress ◽  
Reactive Force ◽  
Fetal Head ◽  
Element Analysis ◽  
Vacuum Extractor ◽  
The Finite Element Analysis ◽  
Von Mises ◽  
Analysis Models

Abstract PurposeIn some cases where operative deliveries are required with vacuum extractor, and obstetricians could choose the vacuum extractor to facilitate the process smoother and safer. However, there is no related biomechanical literature about the influences of vacuum extractors fabricated from different materials and pressures of vacuum on the fetal head. Hence, we utilized the finite element method to investigate the influences of vacuum extractors manufactured from different materials on the fetal head under various extractive pressures.MethodsFirst, the finite element analysis models of vacuum extractor and fetal head were established. The vacuum extractor model was designed as a hemispherical shape and we compared silicone rubber and stainless steel for the materials of vacuum extractor. Subsequently, four different vacuum pressures were applied as the factors for investigation—500-cm H2O, 600-cm H2O, 700-cm H2O, and 800-cm H2O. Finally, we observed and analyzed the reactive force on the fetal head, von Mises stress of vacuum extractor, and von Mises stress on the skull of fetal head to evaluate the influences of vacuum extractors of different materials under different pressures. ResultsThe results demonstrated that different vacuum pressures had only a slight difference of influences on the fetal head. The use of stainless-steel vacuum extractors caused a relatively larger reactive force (358.04–361.37 N) and stress (13.547–13.675 MPa) on the fetal head. ConclusionsNon-metallic or relatively softer materials could be selected when using a vacuum extractor for operative delivery to avoid complications such as scalp scratch, and even cephalohematoma and intracerebral hemorrhage.

scholarly journals Risk of Proximal Femoral Nail Antirotation Implant Failure Upon Different Lateral Femoral Wall Thickness in Intertrochanteric Fracture :A Finite Element Analysis.

2020 ◽  
Author(s):  
Liqin Zheng ◽  
Duo Wai-Chi Wong ◽  
Xinming Chen ◽  
Yuanzhuang Chen ◽  
Pengfei Li
Keyword(s):  
Wall Thickness ◽  
Intertrochanteric Fracture ◽  
Element Model ◽  
Implant Failure ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Fracture Models ◽  
The Stability ◽  
Von Mises ◽  
Stability Type

Abstract PurposePFNA has been commonly used to treat intertrochanteric fractures, despite the risk of implant failure. The integrity of the femur could influence the risk of implant failure. This study aims to evaluate the influence of lateral femoral wall thickness on potential implant failure using a computational modeling approach. MethodsFinite element model of the hip was reconstructed from the Computed Tomography of a female patient. Five intertrochanteric fracture models at different lateral femoral wall thickness (T1 = 27.6 mm, T2 = 25.4 mm, T3 = 23.4 mm, T4 = 21.4 mm, and T5 = 19.3 mm) were created and fixed with PFNA. A critical loading condition was simulated that mimicked a high loading scenario during walking. The implant failure condition, stress and displacement of the PFNA implant and fracture femur were predicted for analysis. ResultsImplant failure of PNFA occurred at the sides of the proximal nail canal especially for the thinner wall models (T4 and T5).The maximum von Mises stress of the nail for T4 changed abruptly to 298.1 MPa. However, thinner wall decreased the displacement of the PFNA implant. There was approximately opponent trend of stress and displacement on proximal and distal fragments with decreasing thickness possibly due to the adaptation after failure.ConclusionA thinner wall increased the risk of PFNA implant failure. Our prediction showed that complete failure occurred when the thickness was 21.4 mm which was close to the value suggested to determine the stability type.

Analysis of the Effect of Ring Stiffness on the Mechanical Performance of a Two-Ring Ilizarov Fixator

2013 ◽  
Vol 8 (1) ◽  
Author(s):  
Yi Zhang ◽  
S. Olutunde Oyadiji
Keyword(s):  
Mechanical Performance ◽  
Vertical Displacement ◽  
Radial Deformation ◽  
Corrective Surgery ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Ring Diameter ◽  
Ilizarov Fixator ◽  
The Wire ◽  
Ring Material

The two-ring Ilizarov fixator is superior, in terms of space and weight savings, to the traditional four-ring Ilizarov fixator. But the stiffness of the two-ring Ilizarov fixator is low. This weakness causes the two-ring Ilizarov fixator to be hardly used in corrective surgery. It has been shown that the configurations of the fixator, such as ring diameter and cross angle of the wires, can affect the stiffness of the fixator. In this study, the focus was on the effects of the properties of the ring, such as ring diameter, ring deformation, and ring material, on the stiffness of the two-ring Ilizarov fixator. The finite element analysis (FEA) technique was employed to model all the two-ring Ilizarov fixators using the ABAQUS FEA software. The following findings were achieved: (1) the radial deformation of the ring has an almost linear relationship with the vertical displacement of the bone especially when the radial deformation is larger, (2) the change in the stiffness of the two-ring Ilizarov fixator caused by the variation of the wire angle is due to the deformation of the ring, (3) the pretension on the wire is greatly reduced after it is attached to the ring, and (4) the influence of ring material on the stiffness of the two-ring Ilizarov fixator is less when the fixator wire angles are 90 deg-90 deg rather than 0 deg-0 deg. Based on these findings, in a real clinical application, the stiffness acting in a fixator-bone system during the course of a treatment and the stiffness of the growing bone can be deduced in a nonintrusive way.

Three-Dimensional Modeling and Finite Element Analysis of an Ankle External Fixator

2020 ◽  
Vol 899 ◽  
pp. 94-102
Author(s):  
Nur Faiqa Ismail ◽  
Muhammmad Aiman Firdaus Bin Adnan ◽  
Solehuddin Shuib ◽  
Nik Ahmad Hambali Nik Abd Rashid
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
External Fixator ◽  
Three Dimensional ◽  
Von Mises Stress ◽  
External Fixators ◽  
Element Analysis ◽  
Stress And Deformation ◽  
The Stability ◽  
Von Mises

External fixator has played an important role in repairing fractured ankle bone. This surgery is done due to the several factors which are the bone is not normal position or has broken into several pieces. The external fixator will help the broken bone to grow and remodel back to the original appearance. However, there are some issues regarding to the stability of this fixation. Improper design and material are the major factor that decreased the stability since it is related to the deformation of the external fixator to hold the bone fracture area. This study aims to design a stable structure for constructing delta frame ankle external fixator to increase the stability of the fixation. There are two designs of external fixator with two types of material used in this present study. Both external fixators with different materials are analyzed in terms of von Mises stress and deformation by using a conventional Finite Element Analysis software; ANSYS Workbench V15. The result obtained shows the Model 1 with stainless steel has less stress and deformation distributions compared to the Model 2. Hence, by using Model 1 as the external fixator, the stability of the fixation can be increased.

scholarly journals Effect of the screw tightening sequence on the stress distribution of a dynamic compression plate: A pilot finite element study

2019 ◽  
Vol 27 (3) ◽  
pp. 230949901987607
Author(s):  
Xiaoreng Feng ◽  
Weichen Qi ◽  
Chengyong Wang ◽  
Frankie Leung ◽  
Bin Chen
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Dynamic Compression ◽  
Von Mises Stress ◽  
Femoral Diaphysis ◽  
Element Analysis ◽  
Dynamic Compression Plate ◽  
Compression Plate ◽  
The Stability ◽  
Von Mises

Objective: Although the optimal screw tightening sequence is a common question orthopaedists encounter during fractures fixation with a dynamic compression plate (DCP), the effect of the screw tightening sequence on the stability of the plate has never been explored. This study explores the effect of the screw tightening sequence on the stress distribution of a DCP using a finite element method. Methods: Idealized finite element analysis models of the femoral diaphysis with six-hole or eight-hole DCPs were constructed. The screw tightening preload was simulated using ‘bolt load’ in ABAQUS. Two screw tightening sequences were studied for the six-hole plate and six sequences were studied for the eight-hole plate. U magnitude and Von Mises stress were used to evaluate the deformation and stress distribution of the plate, respectively. Deformation and stress distribution plots from different sequences were compared. Results: The different screw tightening sequences showed different deformation processes, while all had the same final deformation after all the screws were tightened. Each screw tightening step of different tightening sequences showed different stress distributions in the plate, while all had the same stress distribution after all the screws were tightened. Conclusion: Using different screw tightening sequences to fix the same DCP can produce the same stability, which means in terms of fixation stability, after the two screws nearest to the fracture line are tightened, surgeons do not need to hesitate about the order in which the rest screws should be inserted during the surgery.

scholarly journals Stress Distribution Analysis of the Rectangular and Star-Blade for Plastic Crusher Machine Using Finite Element Analysis

2021 ◽  
Vol 2111 (1) ◽  
pp. 012015
Author(s):  
Nalendro Mataram ◽  
Sigiet Haryo Pranoto ◽  
Rizqi Ilmal Yaqin ◽  
Anis Siti Nurrohkayati ◽  
Noer Aden Bahry ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Plastic Waste ◽  
Von Mises Stress ◽  
Distribution Analysis ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Stress Result ◽  
Von Mises ◽  
Better Than

Abstract Recycling plastic waste can help reduce plastic waste, which is the world’s largest problem. The first solution is a plastic crusher machine, which converts plastic packaging into pellets, especially for plastics made from polyester, which is often used in bottle packaging. An integral part of the crushing machine is the crushing blade, which determines the design and analysis of the blade. The finite element analysis method is widely used in engineering analysis. Its results can provide useful information for the analysis of manufacturing processes. A rectangular blade and a star-shaped blade are the two types to consider. The analytical results obtained on the blade of the crusher machine in the rectangular shape that was given loads by 200 N, 400 N, and 600 N are 1.285 × 103 N/m2, 2.570 × 103 N/m2, and 3.855 × 103 N/m2, respectively. We obtained the displacements are 1.080 × 10-6 mm, 2.160 × 10-6 mm, and 3.241 × 10-6 mm, respectively. The maximum von mises stress result on consecutive star-shaped blades are 8.890 × 102 N/m2, 1.778 × 103 N/m2, and 2.667 × 103 N/m2. The displacement obtained are 1.211 × 10-6 mm, 2.422 × 10-6 mm, and 3.633 × 10-6 mm. The results of this analysis indicate that for the star blade, the shape is better than for the rectangular blade at the same time, and for the star blade, the stress is smaller than for the rectangular blade. Based on this simulation, the safety factor is 15, which means that it is more than 1, which means that it is safe.

On the Effect of Screw Preload on the Stress Distribution of Mandibles During Segmental Defect Treatment Using an Additively Manufactured Hardware

2016 ◽  
Author(s):  
Amirhesam Amerinatanzi ◽  
Narges Shayesteh Moghaddam ◽  
Ahmadreza Jahadakbar ◽  
David Dean ◽  
Mohammad Elahinia
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Von Mises Stress ◽  
Patient Specific ◽  
Fixation Device ◽  
Element Analysis ◽  
Porous Niti ◽  
The Finite Element Analysis ◽  
Low Stiffness ◽  
Von Mises

The most common method for mandibular reconstructive surgery is the use of a Ti-6Al-4V fixation device and a fibular double barrel graft. This highly stiff fixation hardware (E = 112 GPa) often shields the bone graft (E = 20 GPa) from carrying the load, which may result in bone resorption. Highly stiff Ti-6Al-4V fixation hardware is also likely to concentrate stress in the fixation plate or at screw threads, possibly leading to hardware cracking or screw pull-out. As a solution for that, we have proposed and studied the effect of using a low stiffness, porous NiTi fixation device [1–4]. Although the stress in the fixation device is increased, using such low stiffness fixation hardware, is preferable to have an even higher stress on the graft in order to minimize the risk of resorption or hardware failure. We assume that preloading screws allows them to better engage the fixation hardware with the plate and the surrounding bone and causes an increased von Mises stress. The fixation device can be patient-specific and additively manufactured, such that the shape would match the outer surface of the cortical bone. In this study, we modeled a healthy cadaver mandible via CT-derived 3D surface data. The mandible was virtually resected in the molar region (M1−3). The model simulated the result of reconstructive surgery under the highest chewing loading regime (i.e., 526 N on first right molar tooth [5, 6]) where reconstruction was done with either Ti-6Al-4V fixation hardware or patient specific, stiffness-matched, porous NiTi fixation hardware. The calibration of the material properties for this simulation was done using experimentally obtained data (DSC and compression tests) of Ni-rich NiTi bulk samples. The analyzed term in the finite element analysis was stress distribution in the cortical and cancellous bone. Porous NiTi fixation devices were also produced using Selective Laser Melting (SLM) using the geometry of the aforementioned cadaver mandible. In this paper we have studied the effect of additional torque or preload on the performance of the fixation plates. The finite element analysis demonstrated that applying a preload to the screws increased the stress on the bone. Under similar levels of applied preload, the porous NiTi fixation device showed an increased level of von Mises stress in the bone, particularly in the graft. Additionally, the analysis indicated the higher level of stress on the bone surrounding the screws for the case of using NiTi, which could contribute to increasing screw stability. The fabricated patient-specific fixation hardware not only matched the shape of cortical bone but also contained the level of porosity that defines the appropriate modulus of elasticity.

The Structure Design of the Mechanical Clamping Claw of the Automatic Arranging Drill Pipe System

2012 ◽  
Vol 510 ◽  
pp. 165-169
Author(s):  
Yong Bai Sha ◽  
Xiao Peng Wan ◽  
Xiao Ying Zhao
Keyword(s):  
Finite Element Analysis ◽  
Drill Pipe ◽  
Structure Design ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Pipe System ◽  
The Finite Element Analysis ◽  
Working Principle ◽  
Relevant Calculation ◽  
Von Mises

This paper presents the structure design, the working principle and the relevant calculation of the mechanical clamping claw of the land rigs automatic arranging drill pipe system. Applying the Generative Structural Analysis module of the CATIA, we can get the Von Mises stress image to show the stress distribution. The finite element analysis provides a simple effective method for the design of the structure of the mechanical clamping claw. Through this device the drill pipe can be transferred automatically and circularly from the rat hole to the pipe racking system and from pipe racking system to the mouth of the well.

scholarly journals Similar stress repartition for a standard uncemented collared femoral stem versus a shortened collared femoral stem

SICOT-J ◽  
2021 ◽  
Vol 7 ◽  
pp. 58
Author(s):  
Cécile Batailler ◽  
Jobe Shatrov ◽  
Axel Schmidt ◽  
Elvire Servien ◽  
Jean Marc Puch ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Femoral Stem ◽  
Short Stem ◽  
Von Mises Stress ◽  
Element Analysis ◽  
Significant Difference ◽  
The Finite Element Analysis ◽  
Von Mises ◽  
Short Stems

Introduction: The design of uncemented femoral stems for use in total hip arthroplasty has evolved. Several uncemented short stems have been developed with different bone fixations, shapes, or stem lengths. The literature analyzing the biomechanical performance of short to standard stem lengths is limited. The aim was to compare the stress repartition on a standard uncemented stem and a shortened uncemented femoral stem with the same design features. Material and methods: This finite element analysis assessed the stress repartition on two femoral components with the same design (uncemented, collared, proximal trapezoidal cross-section, and a tapered quadrangular distal stem) but with two different lengths. The shortened stem was shorter by 40 mm compared to the standard stem. The stress repartition was analysed according to the Von Mises criterion. Results: The stress repartition was similar for the standard and shorter stem without significant difference (p = 0.94). The mean Von Mises stress was 58.1 MPa [0.2; 154.1] for the standard stem and 57.2 MPa [0.03; 160.2] for the short stem. The distal part of the standard stem, which was removed in the short stem, had mean stress of 3.7 MPa [0.2; 7.0]. Conclusion: The finite element analysis found similar stress repartitions between a standard uncemented collared stem and a short, collared stem with the same design. A clinical study assessing the clinical outcomes and the bone remodelling with a collared short stem would be interesting to confirm these first promising results.

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