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BACKGROUND: Biomechanical properties of the residual limb-socket interface not only have a direct impact on the fit of the prosthesis, but also the basis for optimal design of the socket structure. Combining digital design technology with rehabilitation medical engineering will effectively improve the efficiency and quality of the prosthesis socket. OBJECTIVE; The reverse-positive combined modeling method was used to design a custom-made socket model for patients with calf amputation to evaluate the interfaciai stress between the residual limb and the socket. The socket was iteratively designed. The optimized model was produced by three-dimensional printing to improve traditional hand-made socket methods. METHODS: Two patients with calf amputation were selected (Volunteers of the Inner Mongolia Honorary Military Rehabilitation Center). According to the CT scan image of the patient’s residual limb, Mimics was used for image processing, and then Geomagic and UG were used to obtain the geometric model of the residual limb. Through the use of the computer-aided design software Fusion360, the socket was forward modeled according to the different tolerances of the tissue structure of the various parts of the residual limb. The Mooney-Revlin superelastic model was used to define the material properties of the soft tissue, and the finite element analysis of the residual limb-socket interface stress was performed. The iterative design of the socket was carried out according to the feedback of the results, and the acceptance socket model after re-modification was evaluated. Three-dimensional printing produced a socket, which received experimental measurements. RESULTS AND CONCLUSION: (1) The stress of the interface between the socket and the residual limb after iterative design was analyzed, and the stress values of the residual limbs were lower than the pain threshold, which met the design standard and could achieve functional transferability and safety comfort. (2) Two patients wearing three-dimensional printing made the socket adaptability and stability, and the walking symmetry was significantly improved compared with the hand-made socket, meeting the biomechanical requirements of the residual limb. (3) A complete design, evaluation and manufacturing system for the prosthetic lumen was established.
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The objective of this study was to determine the visco-hyperelastic constitutive law of brain tissue under dynamic impacts. A method combined by finite element simulations and optimization algorithm was employed for the determination of material variables. Firstly, finite element simulations of brain tissue dynamic uniaxial tension, with a maximum stretch rate of 1.3 and strain rates of 30 s and 90 s , were developed referring to experimental data. Then, fitting errors between the engineering stress-strain curves predicted by simulations and experimental average curves were assigned as objective functions, and the multi-objective genetic algorithm was employed for the optimation solution. The results demonstrate that the brain tissue finite element models assigned with the novel obtained visco-hyperelastic material law could predict the brain tissue's dynamic mechanical characteristic well at different loading rates. Meanwhile, the novel material law could also be applied in the human head finite element models for the improvement of the biofidelity under dynamic impact loadings.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic parameters of shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model,so as to provide theoretical basis for clinical EOM surgery by numerical modeling.Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test,and the hyperelastic analysis was conducted using the first-order Ogden model and ABAQUS software.Results The experimental result showed that the passive behavior of fox EOMs was nonlinear.The corresponding hyperelastic parameters μ =(6.57 ± 3.76) kPa and oα =8.16 ± 1.63 were obtained.When the strain of EOMs was larger than 6％,there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P ＞ 0.05).Both the calculation result and the simulation result well fitted to the experimental result.Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To determine the hyperelastic constitutive equation of biological soft tissues and study the mechanical responses during the clamping process of biological tissues. Methods The destructive uniaxial tensile test was performed on fresh porcine liver and the uniaxial tension experiment was simulated in ABAQUS. The hyperelastic constitutive equation of porcine liver was determined by comparing the simulation results with the experimental data. Based on this equation, the sharp teeth-shaped and wave-shaped chucks were used to simulate the clamping process. Results The simulation results of the tensile experiment with the 4th-order Ogden model were in good agreement with the experimental data. The results of tissue clamping simulation showed that stress concentration was more likely to occur when the sharp teeth-shaped chuck was adopted. Conclusions The 4th-order Ogden model can be used to describe the hyperelasticity of porcine liver and determine the relevant para-meters. Using the sharp-shaped chuck is more likely to cause tissue clamping damage, and there is a linear relationship between tissue stress and clamping feed distance. These research findings provide references for the design of surgical clamp.
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Objective To determine the hyperelastic parameters shear modulus (μ) and curvature parameter (α) of extraocular muscles (EOMs) in Ogden hyperelastic model, so as to provide theoretical basis for clinical EOM surgery by numerical modeling. Methods The passive behavior of fox EOMs in vitro was determined by the uniaxial tensile test, and the hyperelastic analysis was conducted by the first-order Ogden model and ABAQUS software. Results The experimental result showed that the passive behavior of fox EOMs was nonlinear. The corresponding hyperelastic parameters μ =(6.57±3.76) kPa and α=8.16±1.63 were obtained. When the strain of EOMs was larger than 6%, there were no statistical differences between the experimental result and the calculation result of the first-order Ogden hyperelastic model (P>0.05). Both the calculation result and the simulation result well fitted to the experimental result. Conclusions The hyperelastic parameters identified in this study can be used as the input for the corresponding numerical modeling of fox EOMs.
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Objective To obtain an optimized method of providing hyperelastic parameters of soft tissue, and to promote the simulation accuracy in explicit solution of finite element analysis (FEA) on soft tissue impact test. Methods Compressive properties of soft tissue from six fresh planta were measured. The experimental data were used to calculate the FEA material properties, which were then optimized by Poisson’s ratio. With the same loading and boundary conditions as the experiment, the FEA model was conducted for simulation. The simulation results were verified by both the experimental data and literature data. Results The force-displacement curve of soft tissue presented an exponential growth trend in the in vitro biomechanical experiment. When the compression ratio was under 45%, the FEA simulation result was consistent with the experimental data. When the compression ratio was above 45%, the closer the Poisson’s ratio up to 0.5, the higher the accuracy of FEA simulation result. However, there was a strong linear correlation between the FEA simulation results and experimental data (R2=0.9923) when the Poisson’s ratio was 0.497. Conclusions The simulation result of material parameters in FEA model is preferable in this study. With a lower compression ratio, the simulation results from FEA model are in consistency with the experimental data. Increasing the Poisson’s ratio can promote the simulation accuracy of the FEA model when the compression ratio is high.
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Objective To propose an inverse method for determining nonlinear mechanical properties of the blood vessel based on the results of experimental data and numerical simulation.Methods Pressure loading was applied on the blood vessel to obtain the experimental data of in vitro holistic blood vessel by using the self-designed device. The finite element model of vessel inflation was established by supposing that material characteristics of the blood vessel were in corresponding with the hyperelastic Ogden model. Mechanical properties of the blood vessel were then computed by the reverse method based on these experimental data and simulated results .Results The first-order and second-order Ogden material parameters of the rabbit abdominal aorta were identified, in which α=10.86±1.98 for the first-order Ogden material model. The mechanical properties of the rabbit abdominal aorta could be characterized as the hyperelastic material. Conclusions The inverse method based on the experimental measurement and numerical simulation can be used to identify the nonlinear mechanical properties of the blood vessel.
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Ehlers-Danlos syndrome (EDS) is a group of related conditions that commonly share the decrease of the tensile strength and integrity of the skin, joints and other tissues. We report three cases of EDS. All patients were male, and their presenting symptoms and signs included hyperelasticity and fragility of skin and hypermobility of joints. All cases belonged to type II and classical type. Earlier classification of EDS included up to 11 disorders. Recently, however, a simple classification has been proposed in an attempt to eliminate the confusion associated with the former classification. Till now, 30 cases of EDS have been reported in Korea. The review of the Korean cases revealed that, according to Villefranch classification and Berlin classification, the most common type was type II and classical type, respectively.
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Humanos , Masculino , Berlim , Classificação , Síndrome de Ehlers-Danlos , Articulações , Coreia (Geográfico) , Pele , Resistência à TraçãoRESUMO
Ehlers-Danlos syndrome (EDS) is an inherited connective tissue disorder characterized by fragility of the skin, hyperelasticity of the skin, hyperextensible joints, vascular lesions, easy bruising, and excessive scarring after injuries. Some patients with EDS have neurological symptoms and signs, such as muscular hypotonia, muscular atrophy, spin-ocerebellar tract degeneration, cerebral atrophy, mental retardation, and epilepsy. We report a 16-year-old man who showed mental retardation, hyperelasticity of the skin, joint hypermobility, and muscular atrophy on the bilateral hand muscles. A skin biopsy revealed dermal thickening, a decrease in the density and number of collagen fibrils, distur-bances of the wickerwork pattern, and a disproportional increase in the number of elastic fibers.