8 research outputs found
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Analysis of engineering structures and components created using the generative design
Generative design is an AI-driven process to explore all the possible design variants, it mimics nature’s evolutionary approach to create an optimised final design. Generative design and additive manufacturing are interlinked because additive manufacturing is able to fabricate complex geometries. Generative algorithms have demonstrated their effectiveness in reducing costs, weight and development time across various industries including automotive and aerospace. This paper analysed components and structures to show the advantages of using the generative design method, problems encountered and issues that could be addressed to improve the final designs. Loading conditions, stress concentrations and manufacturability of the generative-designed components were discussed in the paper.</p
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A numerical investigation into the application of an orthotropic porous structure for a femoral stem manufactured using laser melting technology
This work compares the stress distribution in the periprosthetic cortical bone when implanted with Cobalt Chrome Molybdenum (CoCrMo) stems of varying stiffness configurations. A fully dense CoCrMo stem and a stem with cortical bone properties have been modelled to form a basis for comparison. The effect of orthotropic material behaviour has been investigated using a fully porous orthotropic stem and a graded stem comprising of a 1 mm fully dense CoCrMo outer skin with a porous orthotropic core. The graded orthotropic stem has also been compared with a graded implant with an isotropic core
An approach to developing customized total knee replacement implants
Total knee replacement (TKR) has been performed for patients with end-stage knee joint arthritis to relieve pain and gain functions. Most knee replacement patients can gain satisfactory knee functions; however, the range of motion of the implanted knee is variable. There are many designs of TKR implants; it has been suggested by some researchers that customized implants could offer a better option for patients. Currently, the 3-dimensional knee model of a patient can be created from magnetic resonance imaging (MRI) or computed tomography (CT) data using image processing techniques. The knee models can be used for patient-specific implant design, biomechanical analysis, and creating bone cutting guide blocks. Researchers have developed patient-specific musculoskeletal lower limb model with total knee replacement, and the models can be used to predict muscle forces, joint forces on knee condyles, and wear of tibial polyethylene insert. These available techniques make it feasible to create customized implants for individual patients. Methods and a workflow of creating a customized total knee replacement implant for improving TKR kinematics and functions are discussed and presented in this paper
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The effect of polyethylene thickness in fixed- and mobile-bearing total knee replacements
In this paper fixed- and mobile-bearing implants were simulated using a multibody dynamic model and a finite element model to investigate the contact pressure distribution in the ultra high molecular weight polyethylene tibial bearing component. The thickness of polyethylene varied from 6.8 to 12.3 mm and the polyethylene was modelled as a non-linear material. It was found that the contact pressure on the polyethylene decreased in the fixed-bearing implant when the thickness of polyethylene increased from 6.8 to 8 and 9.6 mm, but there was little further decrease in pressure with the increase of polyethylene thickness from 9.6 to 11.0 and 12.3 mm. In the mobile-bearing implant, no increase in contact pressure on the superior surface was found with the increase in the thickness of the polyethylene; however, the contact pressures on the inferior contact surface of the thicker designs were higher than those in the 6.8 mm design. The numerical results obtained in this paper are in good agreement with published experimental test results. Moreover, the paper presents a detailed pressure distribution on the tibial bearing component during a full gait cycle
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Finite element analysis of sagittal angles of unicompartmental knee arthroplasty
BackgroundUnicompartmental knee arthroplasty is an effective treatment for knee osteoarthritis, but it has the risk of failure, and the installation position of the prosthesis is one of the factors affecting the failure. There are few biomechanical studies on the installation angle of unicompartmental knee prosthesis.MethodsConstructed a finite element model of a normal human knee joint, and the validity of the model was verified by stress and front anterior methods. The mobile-bearing unicompartmental knee arthroplasty femoral prosthesis was placed at 3° intervals from 0° sagittal plane to 15° flexion, and − 2° and 17°were established, and observing the biomechanical changes of components.FindingsMaximum peak stresses occurred at a sagittal mounting angle of −2° for the insert and the contralateral meniscus, with the tibia showing a maximum at 17° sagittal and the tibial prosthesis stress maximum occurring at 6° sagittal. As the sagittal plane angle of the femoral prosthesis increases and the osteotomy distance extends posteriorly, more bone is amputated during the osteotomy. The ratio of the distance from the tip of the anterior intramedullary nail to the anterior end of the osteotomy to the total anteroposterior length of the sagittal osteotomy ranged from 43.2% to 44.6%.InterpretationIn this paper, the more appropriate sagittal mounting position for the femoral prosthesis is between 9 and 12°, based on the amount of osteotomy and the peak stress of each component in a standing position.</p
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A tailored hydroxyapatite/magnesium silicate 3D composite scaffold: mechanical, degradation, and bioactivity properties
Today, hydroxyapatite (HA)-based composite scaffolds are widely studied, but there is a lack of a doping method that can simultaneously improve the mechanical strength, degradation rate, and bioactivity of HA scaffolds. In this paper, the amorphous magnesium silicate (MS) with a low melting point is selected as the doping phase of HA. The hydroxyapatite/magnesium silicate composite was fabricated using photocuring technology. In addition, at high temperatures, ionic substitution can occur between the magnesium silicate glass phase and the HA lattice. Therefore, a new phase with a pinning effect can be obtained at the grain boundary and the magnesium silicate can further improve the biocompatibility of HA scaffolds. In the sintering process, the magnesium silicate was melted to a liquid state, and then the sintering temperature of the scaffold was reduced for grain refinement. The morphological analysis shows that MS doping is an important factor for grain refinement, which has been reduced from 12 μm to 6 μm. Furthermore, the formation of new diopside and whitlockite phases with a pinning effect has been observed at the grain boundaries. Specifically, the compressive stress of the composite scaffold is increased by 59.15% compared to the pure HA scaffold. However, the soaking and cell experimental findings show that the composite scaffold has a better degradation rate, cell activity, and bone induction. Finally, this study found that a composite scaffold with improved mechanical strength, degradation performance, and biocompatibility can be obtained with the addition of magnesium silicate as the doping phase of HA with 30 wt.% of
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Dual output feature fusion networks for femoral segmentation and quantitative analysis of the knee joint
BackgroundMagnetic resonance imaging (MRI) is the preferred imaging modality for diagnosing knee disease. Segmentation of the knee MRI images is essential for subsequent quantification of clinical parameters and treatment planning for knee prosthesis replacement. However, the segmentation remains difficult due to individual differences in anatomy, the difficulty of obtaining accurate edges at lower resolutions, and the presence of speckle noise and artifacts in the images. In addition, radiologists must manually measure the knee's parameters which is a laborious and time-consuming process.PurposeAutomatic quantification of femoral morphological parameters can be of fundamental help in the design of prosthetic implants for the repair of the knee and the femur. Knowledge of knee femoral parameters can provide a basis for femoral repair of the knee, the design of fixation materials for femoral prostheses, and the replacement of prostheses.MethodsThis paper proposes a new deep network architecture to comprehensively address these challenges. A dual output model structure is proposed, with a high and low layer fusion extraction feature module designed to extract rich features through the cross-fusion mechanism. A multi-scale edge information extraction spatial feature module is also developed to address the boundary-blurring problem.ResultsBased on the precise automated segmentation results, 10 key clinical parameters were automatically measured for a knee femoral prosthesis replacement program. The correlation coefficients of the quantitative results of these parameters compared to manual results all achieved at least 0.92. The proposed method was extensively evaluated with MRIs of 78 patients’ knees, and it consistently outperformed other methods used for segmentation.ConclusionsThe automated quantization process produced comparable measurements to those manually obtained by radiologists. This paper demonstrates the viability of automatic knee MRI image segmentation and quantitative analysis with the proposed method. This provides data to support the accuracy of assessing the progression and biomechanical changes of osteoarthritis of the knee using an automated process, thus saving valuable time for the radiologists and surgeons.</p
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Sub-regional design of the bionic bone scaffolds using macrostructural topology
With the increasing demand for bone repair, the bionic bone scaffolds have become a research hotspot. A sub-regional design method of the bionic bone scaffolds, using macrostructural topology, is proposed in this paper, aiming to provide a functionally enhanced region division method for the gradient design. The macrostructural topology was carried out by the bi-directional evolutionary structural optimization (BESO), dividing the predefined design domain into sub-region A and sub-region B. Subsequently, a combined probability sphere model and a distance-to-scale coefficient mapping model are established to implement the graded porosification based on the Voronoi tessellation. This approach takes geometric and mechanical continuity into fully account and assures a reasonable distribution of characteristic parameters, yielding to improve the mechanical strength under specific stress conditions. Finally, the scaffolds were fabricated by the laser powder bed fusion (LPBF) process using the Ti-6Al-4V powder. The results of compression tests are satisfactory, showing that the as-built specimens implement sub-regional functionality. The apparent elastic modulus and the ultimate strength range, respectively, between 1.50 GPa and 7.12 GPa (for the first module) and between 38.55 MPa and 268.03 MPa (for the second module), which conform to the required level of natural bone, providing a possibility for clinical application