scholarly journals Optimization of a novel external fixator for orthopaedic applications

2020 ◽  
Vol 318 ◽  
pp. 01025
Author(s):  
Mohammed S. Alqahtani
Keyword(s):  
Topology Optimization ◽  
External Fixator ◽  
Mechanical Performance ◽  
Bone Fractures ◽  
Significant Risk ◽  
Polymeric Materials ◽  
Acrylonitrile Butadiene Styrene ◽  
Patient Specific ◽  
Element Analysis ◽  
Fixation Devices

The use of external fixation devices is a very common method for the treatment of bone fractures. However, these fixators present some limitations in terms of mobility, significant risk of infection, and induce pain and discomfort. Moreover, they are also not fully customized to suit individual patients. To avoid these limitations, this paper presents a novel patient-specific external fixator developed using reverse engineering, finite element analysis and additive manufacturing. The fixator was designed based on a set of computer tomography (CT) scan images of a patient and optimized considering different thickness values and materials. New lightweight designs were produced through a manual process (regular distribution of circular and hexagonal voids) and topology optimization. Different polymeric materials (Polylactic acid (PLA); Acrylonitrile butadiene styrene (ABS) and Polyamide (PA)) were also considered for the fabrication of these designs. It was found that although both PLA and ABS allow to meet the design requirements, and that the best mechanical properties were obtained with fixators made of PLA. Results also showed that the best results in terms of mechanical performance and weight reduction was obtained with topology optimization.

scholarly journals Optimization of a Patient-Specific External Fixation Device for Lower Limb Injuries

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2661
Author(s):  
Mohammed S. Alqahtani ◽  
Abdulsalam Abdulaziz Al-Tamimi ◽  
Mohamed H. Hassan ◽  
Fengyuan Liu ◽  
Paulo Bartolo
Keyword(s):  
Topology Optimization ◽  
External Fixation ◽  
Polylactic Acid ◽  
External Fixator ◽  
Bone Fractures ◽  
Healing Process ◽  
Patient Specific ◽  
External Fixators ◽  
Fixation Devices ◽  
Limb Injuries

The use of external fixation devices is considered a valuable approach for the treatment of bone fractures, providing proper alignment to fractured fragments and maintaining fracture stability during the healing process. The need for external fixation devices has increased due to an aging population and increased trauma incidents. The design and fabrication of external fixations are major challenges since the shape and size of the defect vary, as well as the geometry of the human limb. This requires fully personalized external fixators to improve its fit and functionality. This paper presents a methodology to design personalized lightweight external fixator devices for additive manufacturing. This methodology comprises data acquisition, Computer tomography (CT) imaging analysis and processing, Computer Aided Design (CAD) modelling and two methods (imposed predefined patterns and topology optimization) to reduce the weight of the device. Finite element analysis with full factorial design of experiments were used to determine the optimal combination of designs (topology optimization and predefined patterns), materials (polylactic acid, acrylonitrile butadiene styrene, and polyamide) and thickness (3, 4, 5 and 6 mm) to maximize the strength and stiffness of the fixator, while minimizing its weight. The optimal parameters were found to correspond to an external fixator device optimized by topology optimization, made in polylactic acid with 4 mm thickness.

scholarly journals Computational and experimental mechanical performance of a new everolimus-eluting stent purpose-built for left main interventions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Saurabhi Samant ◽  
Wei Wu ◽  
Shijia Zhao ◽  
Behram Khan ◽  
Mohammadali Sharzehee ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Mechanical Performance ◽  
Experimental Studies ◽  
Patient Specific ◽  
Wall Structure ◽  
Left Main ◽  
Element Analysis ◽  
Stent Expansion ◽  
Radial Strength ◽  
Different Diameters

AbstractLeft main (LM) coronary artery bifurcation stenting is a challenging topic due to the distinct anatomy and wall structure of LM. In this work, we investigated computationally and experimentally the mechanical performance of a novel everolimus-eluting stent (SYNERGY MEGATRON) purpose-built for interventions to large proximal coronary segments, including LM. MEGATRON stent has been purposefully designed to sustain its structural integrity at higher expansion diameters and to provide optimal lumen coverage. Four patient-specific LM geometries were 3D reconstructed and stented computationally with finite element analysis in a well-validated computational stent simulation platform under different homogeneous and heterogeneous plaque conditions. Four different everolimus-eluting stent designs (9-peak prototype MEGATRON, 10-peak prototype MEGATRON, 12-peak MEGATRON, and SYNERGY) were deployed computationally in all bifurcation geometries at three different diameters (i.e., 3.5, 4.5, and 5.0 mm). The stent designs were also expanded experimentally from 3.5 to 5.0 mm (blind analysis). Stent morphometric and biomechanical indices were calculated in the computational and experimental studies. In the computational studies the 12-peak MEGATRON exhibited significantly greater expansion, better scaffolding, smaller vessel prolapse, and greater radial strength (expressed as normalized hoop force) than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY (p < 0.05). Larger stent expansion diameters had significantly better radial strength and worse scaffolding than smaller stent diameters (p < 0.001). Computational stenting showed comparable scaffolding and radial strength with experimental stenting. 12-peak MEGATRON exhibited better mechanical performance than the 9-peak MEGATRON, 10-peak MEGATRON, or SYNERGY. Patient-specific computational LM stenting simulations can accurately reproduce experimental stent testing, providing an attractive framework for cost- and time-effective stent research and development.

scholarly journals Pre-drilling and self-drilling pins screw-bone fixation stress interaction analysis induced by uniaxial compression loading

2019 ◽  
Vol 15 (1) ◽  
pp. 99-108
Author(s):  
Lim Pei Chee ◽  
Ruslizam Daud ◽  
Shah Fenner Khan Mohamad Khan ◽  
Nurul Alia Md Zain ◽  
Yazid Bajuri
Keyword(s):  
Uniaxial Compression ◽  
External Fixator ◽  
Bone Fractures ◽  
Interaction Analysis ◽  
Compressive Loading ◽  
Three Dimensional ◽  
Maximum Magnitude ◽  
Element Analysis ◽  
Compression Load ◽  
Von Mises

A newly designed Uniaxial external fixator which functions as a universal fixator in the application of all types of bone fractures is recently introduced by both Hospital Universiti Kebangsaan Malaysia (HUKM) and Universiti Malaysia Perlis (UniMAP). The Investigation is focused on identifying and measuring the performance in terms of strength or weakness of the fixator that is needed before the application to the human body. Hence, this research was conducted to determine the performance of Uniaxial external fixator which was based on geometry using different screw drilling techniques applied during an angled uniaxial compression load.  A three-dimensional fixator-bone was constructed using different screw inserting techniques which was then converted into ANSYS v14.5 for the purposes of conducting a finite element analysis (FEA).  Axial compressive loading with various degrees from 60 to 6300 N were applied to bone models to stimulate patient’s daily activities while 10 to 100 N were applied to fixator models for the purposes of reviewing environmental loading to fixator-bone models. Findings revealed that maximum magnitude which caused deformation for predrilling and self-drilling models were located at the highest pin-bone interaction. Conversely, the maximum magnitude of the von Mises strain and stress was located at the lowest pin-bone interaction by omitting the existence of fixator for both Case 1 and 2. There was no obvious difference in the comparison of both models in terms of deformation. However, predrilling models have higher strain and stress than self-drilling models. In sum, findings indicated that self-drilling models have better performance compared to the predrilling models.

scholarly journals Design of a Metal 3D Printing Patient-Specific Repairing Thin Implant for Zygomaticomaxillary Complex Bone Fracture Based on Buttress Theory Using Finite Element Analysis

2020 ◽  
Vol 10 (14) ◽  
pp. 4738
Author(s):  
Yu-Tzu Wang ◽  
Chih-Hao Chen ◽  
Po-Fang Wang ◽  
Chien-Tzung Chen ◽  
Chun-Li Lin
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Biomechanical Analysis ◽  
Patient Specific ◽  
Element Analysis ◽  
Posterior Teeth ◽  
Frontal Process ◽  
Metal 3D Printing ◽  
Stress Variations ◽  
Zygomaticomaxillary Complex

This study developed a zygomaticomaxillary complex (ZMC) patient-specific repairing thin (PSRT) implant based on the buttress theory by integrating topology optimization and finite element (FE) analysis. An intact facial skeletal (IFS) model was constructed to perform topology optimization to obtain a hollow skeleton (HS) model with the structure and volume optimized. The PSRT implant was designed based on the HS contour which represented similar trends as vertical buttress pillars. A biomechanical analysis was performed on a ZMC fracture fixation with the PSRT implant and two traditional mini-plates under uniform axial loads applied on posterior teeth with 250 N. Results indicated that the variation in maximum bone stress and model volume between the IFS and HS models was 15.4% and 75.1%, respectively. Small stress variations between the IFS model and repairing with a PSRT implant (2.75–26.78%) were found for compressive stress at frontal process and tensile stress at the zygomatic process. Comparatively, large stress variations (30.67–96.26%) with different distributions between the IFS model and mini-plate models were found at the corresponding areas. This study concluded that the main structure/contour design of the ZMC repair implant according to the buttress position and orientation can obtain a favorable mechanical behavior.

Finite Element Analysis of Magnesium Alloy Based Bone Fixation Devices

2013 ◽  
Author(s):  
Siladitya Pal ◽  
Amy Chaya ◽  
Sayuri Yoshizawa ◽  
Da-Tren Chou ◽  
Daeho Hong ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Magnesium Alloy ◽  
Gold Standard ◽  
Bone Fractures ◽  
Element Analysis ◽  
Bone Fixation ◽  
Fixation Devices ◽  
Bone Fragments ◽  
The U.S

Each year, there are over six million bone fractures in the U.S., over 30% of which require internal fixation devices to stabilize bone fragments during healing [1–2]. Currently, the gold standard materials for these devices are non-degradable titanium alloys. Unfortunately, these devices cause numerous complications and often require a secondary invasive removal surgery [3–4]. To circumvent these issues, resorbable polymeric devices have been developed, but their mechanical limitations render them inadequate for most load bearing applications [5–7].

scholarly journals Finite Element Analysis of Patient-Specific Condyle Fracture Plates: A Preliminary Study

2015 ◽  
Vol 8 (2) ◽  
pp. 111-116 ◽  
Author(s):  
Peter Aquilina ◽  
William C. H. Parr ◽  
Uphar Chamoli ◽  
Stephen Wroe
Keyword(s):  
Finite Element ◽  
Internal Fixation ◽  
Material Properties ◽  
Mechanical Performance ◽  
Mandibular Condyle ◽  
Patient Specific ◽  
Element Analysis ◽  
Subcondylar Fracture ◽  
The Stability ◽  
Condyle Fracture

Various patterns of internal fixation of mandibular condyle fractures have been proposed in the literature. This study investigates the stability of two patient-specific implants (PSIs) for the open reduction and internal fixation of a subcondylar fracture of the mandible. A subcondylar fracture of a mandible was simulated by a series of finite element models. These models contained approximately 1.2 million elements, were heterogeneous in bone material properties, and also modeled the muscles of mastication. Models were run assuming linear elasticity and isotropic material properties for bone. The stability and von Mises stresses of the simulated condylar fracture reduced with each of the PSIs were compared. The most stable of the plate configurations examined was PSI 1, which had comparable mechanical performance to a single 2.0 mm straight four-hole plate.

scholarly journals 3D Printed Hierarchical Honeycombs with Carbon Fiber and Carbon Nanotube Reinforced Acrylonitrile Butadiene Styrene

2021 ◽  
Vol 5 (2) ◽  
pp. 62
Author(s):  
Michel Theodor Mansour ◽  
Konstantinos Tsongas ◽  
Dimitrios Tzetzis
Keyword(s):  
Carbon Fibers ◽  
Mechanical Performance ◽  
Acrylonitrile Butadiene Styrene ◽  
Experimental Tests ◽  
Fused Filament Fabrication ◽  
Element Analysis ◽  
Compression Performance ◽  
Honeycomb Structures ◽  
3D Printed ◽  
Butadiene Styrene

The mechanical properties of Fused Filament Fabrication (FFF) 3D printed specimens of acrylonitrile butadiene styrene (ABS), ABS reinforced with carbon fibers (ABS/CFs) and ABS reinforced with carbon nanotubes (ABS/CNTs) are investigated in this paper using various experimental tests. In particular, the mechanical performance of the fabricated specimens was determined by conducting compression and cyclic compression testing, as well as nanoindentation tests. In addition, the design and the manufacturing of hierarchical honeycomb structures are presented using the materials under study. The 3D printed honeycomb structures were examined by uniaxial compressive tests to review the mechanical behavior of such cellular structures. The compressive performance of the hierarchical honeycomb structures was also evaluated with finite element analysis (FEA) in order to extract the stress-strain response of these structures. The results revealed that the 2nd order hierarchy displayed increased stiffness and strength as compared with the 0th and the 1st hierarchies. Furthermore, the addition of carbon fibers in the ABS matrix improved the stiffness, the strength and the hardness of the FFF printed specimens as well as the compression performance of the honeycomb structures.

Design and optimization of nonuniform cellular structures

2017 ◽  
Vol 232 (7) ◽  
pp. 1280-1293 ◽  
Author(s):  
Xin Jin ◽  
Guo-Xi Li ◽  
Meng Zhang
Keyword(s):  
Topology Optimization ◽  
Cellular Structure ◽  
Mechanical Performance ◽  
Design Method ◽  
Lightweight Design ◽  
Structure Design ◽  
Cellular Structures ◽  
Manufacturing Constraints ◽  
Element Analysis ◽  
Design And Optimization

Topology optimization and cellular structure infilling are two important approaches to achieve a lightweight design while meeting the relevant mechanical property requirements. In this work, we present a density-variable cellular structure design method combined with topology optimization while ensuring the manufacturability. The effective mechanical properties are reported as functions of the relative density to combine cellular structures with the topology optimization model. The manufacturing constraints are analyzed and expressed in topology optimization. In addition, density-variable cellular structures are rapidly modeled by mapping the topology optimization results to the relative densities of cells and via the use of user-defined features. It is shown by means of finite element analysis that the proposed design approach can improve the mechanical performance compared to the uniform cellular structure under the same weight reduction. And the choice of cell size for higher stiffness of the designed structure varies with different values of manufacturing constraints.

Finite Element Analysis of Stress and Strain Distribution in Gold Thin Film Deposited on Polycarbonate Substrate Subjected to Tension and Cooling

2015 ◽  
Vol 752-753 ◽  
pp. 55-61
Author(s):  
Naoya Tada ◽  
Ya Fei Hu
Keyword(s):  
Thin Film ◽  
Finite Element ◽  
Strain Distribution ◽  
Mechanical Performance ◽  
Polymeric Materials ◽  
Stress And Strain ◽  
Element Analysis ◽  
Gold Thin Film ◽  
Stress And Strain Distribution ◽  
Polycarbonate Substrate

Thin metal films on polymeric materials have been widely used in electronic devices. Their total mechanical performance is determined by the mechanical property of each material, the thickness and size of film and substrate, their interface properties in addition to the temperature change during production and use. In this paper, stress and strain distribution of gold thin film on polycarbonate substrate subjected to tension and cooling was analyzed using the finite element method. The effect of cracking in thin film on the stress and strain distribution was also discussed.

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