The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Guoyan Zheng - One of the best experts on this subject based on the ideXlab platform.
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Computer Assisted Planning of Periacetabular Osteotomy with Biomechanical Optimization: Constant Thickness Cartilage Models vs. Patient-Specific Cartilage Models
Computational Biomechanics for Medicine, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Periacetabular osteotomy (PAO) is an effective approach for surgical treatment of hip dysplasia in young adults. The aim of PAO surgery is to increase acetabular coverage of the femoral head and to reduce contact pressures by reorienting the acetabulum fragment during PAO. The success of PAO significantly depends on the surgeon’s experience. Previously, we have developed a computer assisted planning and navigation system for PAO, which allows for not only quantifying the 3D hip morphology with geometric parameters such as acetabular orientation (expressed as inclination and anteversion angles), lateral center edge (LCE) angle and femoral head coverage for a computer assisted diagnosis of hip dysplasia but also virtual PAO surgical planning and simulation. In this paper, we extend our system with a patient-specific 3D finite element (FE) model to estimate the optimal acetabulum reorientation for planning PAO. One key factor that may influence the biomechanical optimization results is the cartilage models used in the FE simulation. In the literature, both Constant Thickness cartilage models and patient-specific cartilage models have been suggested. Another contribution of our paper is the investigation of the effect of these two different cartilage models on the biomechanical optimization results. Regression analysis showed that the results obtained by the Constant Thickness cartilage models are significantly correlated with those obtained by using the patient-specific cartilage models. Furthermore, biomechanical optimization-based planning of PAO using these two different cartilage models achieved the same optimal orientations.
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Evaluation of Constant Thickness Cartilage Models vs. Patient Specific Cartilage Models for an Optimized Computer-Assisted Planning of Periacetabular Osteotomy
PloS one, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Modern computerized planning tools for periacetabular osteotomy (PAO) use either morphology-based or biomechanics-based methods. The latter relies on estimation of peak contact pressures and contact areas using either patient specific or Constant Thickness cartilage models. We performed a finite element analysis investigating the optimal reorientation of the acetabulum in PAO surgery based on simulated joint contact pressures and contact areas using patient specific cartilage model. Furthermore we investigated the influences of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results. Ten specimens with hip dysplasia were used in this study. Image data were available from CT arthrography studies. Bone models were reconstructed. Mesh models for the patient specific cartilage were defined and subsequently loaded under previously reported boundary and loading conditions. Peak contact pressures and contact areas were estimated in the original position. Afterwards we used a validated preoperative planning software to change the acetabular inclination by an increment of 5° and measured the lateral center edge angle (LCE) at each reorientation position. The position with the largest contact area and the lowest peak contact pressure was defined as the optimal position. In order to investigate the influence of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results, the same procedure was repeated with the same bone models but with a cartilage mesh of Constant Thickness. Comparison of the peak contact pressures and the contact areas between these two different cartilage models showed that good correlation between these two cartilage models for peak contact pressures (r = 0.634 ∈ [0.6, 0.8], p 0.8, p < 0.001). For both cartilage models, the largest contact areas and the lowest peak pressures were found at the same position. Our study is the first study comparing peak contact pressures and contact areas between patient specific and Constant Thickness cartilage models during PAO planning. Good correlation for these two models was detected. Computer assisted planning with FE modeling using Constant Thickness cartilage models might be a promising PAO planning tool when a conventional CT is available.
Li Liu - One of the best experts on this subject based on the ideXlab platform.
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Biomechanical Optimization-Based Planning of Periacetabular Osteotomy.
'Springer Science and Business Media LLC', 2018Co-Authors: Li Liu, Siebenrock Klaus, Nolte Lutz-p., Zheng GuoyanAbstract:Modern computerized planning tools for periacetabular osteotomy (PAO) use either morphology-based or biomechanics-based methods. The latter rely on estimation of peak contact pressures and contact areas using either patient-specific or Constant Thickness cartilage models. We performed a finite element analysis investigating the optimal reorientation of the acetabulum in PAO surgery based on simulated joint contact pressures and contact areas using patient-specific cartilage model. Furthermore we investigated the influences of using patient-specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results. Ten specimens with hip dysplasia were used in this study. Image data were available from CT arthrography studies. Bone models were reconstructed. Mesh models for the patient-specific cartilage were defined and subsequently loaded under previously reported boundary and loading conditions. Peak contact pressures and contact areas were estimated in the original position. Afterward we used validated preoperative planning software to change the acetabular inclination by an increment of 5° and measured the lateral center-edge angle (LCE) at each reorientation position. The position with the largest contact area and the lowest peak contact pressure was defined as the optimal position. In order to investigate the influence of using patient-specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results, the same procedure was repeated with the same bone models but with a cartilage mesh of Constant Thickness. Comparison of the peak contact pressures and the contact areas between these two different cartilage models showed that good correlation between these two cartilage models for peak contact pressures (r = 0.634 ∈[0.6, 0.8], p 0.8, p < 0.001). For both cartilage models, the largest contact areas and the lowest peak pressures were found at the same position. Our study is the first study comparing peak contact pressures and contact areas between patient-specific and Constant Thickness cartilage models during PAO planning. Good correlation for these two models was detected. Computer-assisted planning with FE modeling using Constant Thickness cartilage models might be a promising PAO planning tool when a conventional CT is available
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Computer Assisted Planning of Periacetabular Osteotomy with Biomechanical Optimization: Constant Thickness Cartilage Models vs. Patient-Specific Cartilage Models
Computational Biomechanics for Medicine, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Periacetabular osteotomy (PAO) is an effective approach for surgical treatment of hip dysplasia in young adults. The aim of PAO surgery is to increase acetabular coverage of the femoral head and to reduce contact pressures by reorienting the acetabulum fragment during PAO. The success of PAO significantly depends on the surgeon’s experience. Previously, we have developed a computer assisted planning and navigation system for PAO, which allows for not only quantifying the 3D hip morphology with geometric parameters such as acetabular orientation (expressed as inclination and anteversion angles), lateral center edge (LCE) angle and femoral head coverage for a computer assisted diagnosis of hip dysplasia but also virtual PAO surgical planning and simulation. In this paper, we extend our system with a patient-specific 3D finite element (FE) model to estimate the optimal acetabulum reorientation for planning PAO. One key factor that may influence the biomechanical optimization results is the cartilage models used in the FE simulation. In the literature, both Constant Thickness cartilage models and patient-specific cartilage models have been suggested. Another contribution of our paper is the investigation of the effect of these two different cartilage models on the biomechanical optimization results. Regression analysis showed that the results obtained by the Constant Thickness cartilage models are significantly correlated with those obtained by using the patient-specific cartilage models. Furthermore, biomechanical optimization-based planning of PAO using these two different cartilage models achieved the same optimal orientations.
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Evaluation of Constant Thickness Cartilage Models vs. Patient Specific Cartilage Models for an Optimized Computer-Assisted Planning of Periacetabular Osteotomy
PloS one, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Modern computerized planning tools for periacetabular osteotomy (PAO) use either morphology-based or biomechanics-based methods. The latter relies on estimation of peak contact pressures and contact areas using either patient specific or Constant Thickness cartilage models. We performed a finite element analysis investigating the optimal reorientation of the acetabulum in PAO surgery based on simulated joint contact pressures and contact areas using patient specific cartilage model. Furthermore we investigated the influences of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results. Ten specimens with hip dysplasia were used in this study. Image data were available from CT arthrography studies. Bone models were reconstructed. Mesh models for the patient specific cartilage were defined and subsequently loaded under previously reported boundary and loading conditions. Peak contact pressures and contact areas were estimated in the original position. Afterwards we used a validated preoperative planning software to change the acetabular inclination by an increment of 5° and measured the lateral center edge angle (LCE) at each reorientation position. The position with the largest contact area and the lowest peak contact pressure was defined as the optimal position. In order to investigate the influence of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results, the same procedure was repeated with the same bone models but with a cartilage mesh of Constant Thickness. Comparison of the peak contact pressures and the contact areas between these two different cartilage models showed that good correlation between these two cartilage models for peak contact pressures (r = 0.634 ∈ [0.6, 0.8], p 0.8, p < 0.001). For both cartilage models, the largest contact areas and the lowest peak pressures were found at the same position. Our study is the first study comparing peak contact pressures and contact areas between patient specific and Constant Thickness cartilage models during PAO planning. Good correlation for these two models was detected. Computer assisted planning with FE modeling using Constant Thickness cartilage models might be a promising PAO planning tool when a conventional CT is available.
M.a. Kouchakzadeh - One of the best experts on this subject based on the ideXlab platform.
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3D dynamic coupled thermoelastic solution for Constant Thickness disks using refined 1D finite element models
Applied Mathematical Modelling, 2018Co-Authors: Ayoob Entezari, Matteo Filippi, Erasmo Carrera, M.a. KouchakzadehAbstract:Abstract This paper deals with the generalized coupled thermoelastic solution for disks with Constant Thickness. It is a sequel to the authors’s previous work in which refined 1D Galerkin finite element models with 3D-like accuracies are developed for theories of coupled thermoelasticity. Use of the reduced models with low computational costs may be of interest in a laborious time history analysis of the dynamic problems. In this paper, the developed models are applied and evaluated for a 3D solution of the dynamic generalized coupled thermoelasticity problem in the disk subjected to thermal shock loads. Comparison of the obtained result with the results available in the literature verified the proposed finite element models are quite efficient with very high rate of convergence and able to provide results with analytical accuracy. In addition, propagation of the thermoelastic waves, the wave reflection from the boundaries and the Poisson effect in an axisymmetric and asymmetric disk problem are represented as contour plots to demonstrate 3D capabilities of the models.
Jaan Lellep - One of the best experts on this subject based on the ideXlab platform.
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Optimization of conical shells of piece wise Constant Thickness
WSEAS Transactions on Mathematics archive, 2012Co-Authors: Jaan Lellep, Ella PumanAbstract:Conical shells with piece wise Constant Thickness subjected to the distributed transverse pressure and loaded by a rigid central boss are studied. In the paper the both, elastic and inelastic shells are considered. In the case of inelastic shells it is assumed that the material obeys the Hill's plasticity condition and associated flow rule. The optimization problem is posed in a general form involving as particular cases several different problems. Resorting to the variational methods necessary optimality conditions are derived. The problems regarding to the maximization of the plastic limit load and to the minimum weight design are studied in a greater detail.
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Optimization of stepped shells
WSEAS Transactions on Mathematics archive, 2010Co-Authors: Jaan Lellep, Ella Puman, Larissa Roots, E. TungelAbstract:Problems of analysis and optimization of axisymmetric shells of piece wise Constant Thickness are studied. The cases of quasistatic and dynamic loading are considered separately whereas the shells may be manufactured from both, elastic and inelastic materials. Minimum weight designs of inelastic shells of piece wise Constant Thickness are established under the condition that the limit load is fixed. Also the designs of maximum load carrying capacity are determined for given weight (material volume) of the shell. Necessary optimality conditions are derived with the aid of variational methods of the theory of optimal control. Particular cases of maximization of the load carrying capacity of spherical caps and conical shells are studied in a greater detail in the cases of von Mises and Hill's materials.
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Optimization of rotationally symmetric shells
2009Co-Authors: Jaan Lellep, Ella Puman, Larissa Roots, E. TungelAbstract:Rotationally symmetric shells of piece wise Constant Thickness are studied. The cases of quasistatic and dynamic loading are considered separately whereas the shells may be manufactured from both, elastic and inelastic materials. Minimum weight designs of inelastic shells of piece wise Constant Thickness are established under the condition that the limit load is fixed. Also the designs of maximum load carrying capacity are determined for given weight (material volume) of the shell. Necessary optimality conditions are derived with the aid of variational methods of the theory of optimal control.
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Optimization of clamped rigid-plastic shallow shells of piecewise Constant Thickness
International Journal of Non-Linear Mechanics, 1994Co-Authors: Jaan Lellep, Helle HeinAbstract:Abstract The minimum weight problem is studied under the condition that the considered shell has a piecewise Constant Thickness. The shell with free internal edge and clamped outer edge is subjected to uniformly distributed internal pressure. Moderately large deflections are taken into account and a deformation-type theory of plasticity is employed. The optimization problem includes the additional restriction, which demands that the maximal deflections of the shell of piecewise Constant Thickness and of the reference shell, of Constant Thickness, coincide. Employing the variational methods of the optimal control theory, necessary optimality conditions are established. The results obtained are used to establish the optimal parameters for the shell of piecewise Constant Thickness.
Timo M. Ecker - One of the best experts on this subject based on the ideXlab platform.
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Computer Assisted Planning of Periacetabular Osteotomy with Biomechanical Optimization: Constant Thickness Cartilage Models vs. Patient-Specific Cartilage Models
Computational Biomechanics for Medicine, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Periacetabular osteotomy (PAO) is an effective approach for surgical treatment of hip dysplasia in young adults. The aim of PAO surgery is to increase acetabular coverage of the femoral head and to reduce contact pressures by reorienting the acetabulum fragment during PAO. The success of PAO significantly depends on the surgeon’s experience. Previously, we have developed a computer assisted planning and navigation system for PAO, which allows for not only quantifying the 3D hip morphology with geometric parameters such as acetabular orientation (expressed as inclination and anteversion angles), lateral center edge (LCE) angle and femoral head coverage for a computer assisted diagnosis of hip dysplasia but also virtual PAO surgical planning and simulation. In this paper, we extend our system with a patient-specific 3D finite element (FE) model to estimate the optimal acetabulum reorientation for planning PAO. One key factor that may influence the biomechanical optimization results is the cartilage models used in the FE simulation. In the literature, both Constant Thickness cartilage models and patient-specific cartilage models have been suggested. Another contribution of our paper is the investigation of the effect of these two different cartilage models on the biomechanical optimization results. Regression analysis showed that the results obtained by the Constant Thickness cartilage models are significantly correlated with those obtained by using the patient-specific cartilage models. Furthermore, biomechanical optimization-based planning of PAO using these two different cartilage models achieved the same optimal orientations.
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Evaluation of Constant Thickness Cartilage Models vs. Patient Specific Cartilage Models for an Optimized Computer-Assisted Planning of Periacetabular Osteotomy
PloS one, 2016Co-Authors: Li Liu, Timo M. Ecker, Steffen Schumann, Klaus-arno Siebenrock, Guoyan ZhengAbstract:Modern computerized planning tools for periacetabular osteotomy (PAO) use either morphology-based or biomechanics-based methods. The latter relies on estimation of peak contact pressures and contact areas using either patient specific or Constant Thickness cartilage models. We performed a finite element analysis investigating the optimal reorientation of the acetabulum in PAO surgery based on simulated joint contact pressures and contact areas using patient specific cartilage model. Furthermore we investigated the influences of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results. Ten specimens with hip dysplasia were used in this study. Image data were available from CT arthrography studies. Bone models were reconstructed. Mesh models for the patient specific cartilage were defined and subsequently loaded under previously reported boundary and loading conditions. Peak contact pressures and contact areas were estimated in the original position. Afterwards we used a validated preoperative planning software to change the acetabular inclination by an increment of 5° and measured the lateral center edge angle (LCE) at each reorientation position. The position with the largest contact area and the lowest peak contact pressure was defined as the optimal position. In order to investigate the influence of using patient specific cartilage model or Constant Thickness cartilage model on the biomechanical simulation results, the same procedure was repeated with the same bone models but with a cartilage mesh of Constant Thickness. Comparison of the peak contact pressures and the contact areas between these two different cartilage models showed that good correlation between these two cartilage models for peak contact pressures (r = 0.634 ∈ [0.6, 0.8], p 0.8, p < 0.001). For both cartilage models, the largest contact areas and the lowest peak pressures were found at the same position. Our study is the first study comparing peak contact pressures and contact areas between patient specific and Constant Thickness cartilage models during PAO planning. Good correlation for these two models was detected. Computer assisted planning with FE modeling using Constant Thickness cartilage models might be a promising PAO planning tool when a conventional CT is available.