The Influence of Different Parameters of Remodeling Rule on the Resultant Density Distribution of the Proximal Femur

2007 ◽  
Author(s):  
Ali Marzban ◽  
Hamid Nayeb-Hashemi ◽  
Paul K. Canavan
Keyword(s):  
Bone Density ◽  
Boundary Conditions ◽  
Density Distribution ◽  
Proximal Femur ◽  
Gait Cycle ◽  
Initial Conditions ◽  
Femoral Shaft ◽  
Fe Model ◽  
Joint Contact Force ◽  
Joint Contact

The process of adaptive bone remodeling can be described mathematically and simulated with a self-optimizing finite element (FE) model. The aim of this study was to find the bone density distribution of the proximal femur which is affected by the muscle loadings and the hip joint contact force. The basic remodeling rule, which is an objective function for an optimization process relative to external load, was applied to predict the bone density. Its purpose is to obtain a constant value for the strain energy per unit bone mass, by adapting density. The precise solution is dependent on the loads, initial conditions and the parameters in the remodeling rule. The forces at different phases of the gait cycle (walking) were applied as boundary conditions. The density distributions from these loadings were averaged to find the density distribution in the proximal femur. Three different initial densities were considered to investigate the effect of initial conditions. The influence of different parameters and functions on the density distribution and its convergence rate was also investigated. The results were comparable with an actual bone density distribution of the femoral neck head and proximal femoral shaft. It was shown that by applying more boundary conditions through the gait cycle, the converged density distribution is smoother, and more comparable with actual proximal femur.

The Influence of Different Parameters of Remodeling Rule and Walking Speed on Resultant Density Distribution of the Proximal Femur

2007 ◽  
Author(s):  
Ali Marzban ◽  
Hamid Nayeb-Hashemi ◽  
Paul K. Canavan
Keyword(s):  
Bone Density ◽  
Density Distribution ◽  
Hip Joint ◽  
Proximal Femur ◽  
Gait Cycle ◽  
Initial Conditions ◽  
Contact Forces ◽  
Loading Conditions ◽  
Fast Speed ◽  
Joint Contact

The process of adaptive bone remodeling can be described mathematically and simulated with a self-optimizing finite element method (FEM) model. The aim of this study was to understand the effect of the basic remodeling rule on the bone density distribution of the proximal femur affected by the muscle loadings and the hip joint contact forces during normal gait (walking). The basic remodeling rule, which is an objective function for an optimization process relative to external load, was applied to predict the bone density. The purpose of the process is to obtain a constant value for the strain energy per unit bone mass, by adapting density modeling. The precise solution is dependent on the magnitude and direction of loads, loading rate, initial conditions and the parameters in the remodeling rule. In this study, we applied adaptive bone density remodeling under both static and dynamic loading conditions. In the static case, the forces at different phases in the gait cycle were statically applied as boundary conditions. The density distributions from these loadings were averaged to find the density distribution in the proximal femur. Three different initial densities were considered to investigate the effect of initial conditions. The influence of different parameters and functions on the density distribution and its convergence rate was also investigated. Furthermore, effect of changing of muscle loading and hip joint contact forces on resultant mass and density distribution of proximal femur was studied. In the dynamic approach, the forces of different phases of gait cycle were applied during different gait cycle’s times of 1.27 second (slow speed), 1.11 second (normal speed), 1.01 second (moderately fast speed), and 0.83 second (very fast speed). Although the results of bone density adaptations in both approaches were comparable with an example of an actual bone density distribution of the femoral head, neck and the proximal femoral shaft; the converged density distribution in the static approach was smoother and more realistic. It was shown that by applying more loading conditions through the gait cycle the converged density distribution is smoother. The resultant density distribution was more comparable with actual proximal femur compared to past studies.

Need for CT-based bone density modelling in finite element analysis of a shoulder arthroplasty revealed through a novel method for result analysis

2014 ◽  
Vol 0 (0) ◽  
Author(s):  
Werner Pomwenger ◽  
Karl Entacher ◽  
Herbert Resch ◽  
Peter Schuller-Götzburg
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bone Density ◽  
Boundary Conditions ◽  
Density Distribution ◽  
Shoulder Arthroplasty ◽  
Cumulative Distribution ◽  
Patient Specific ◽  
Element Analysis ◽  
Shoulder Complex

AbstractTreatment of common pathologies of the shoulder complex, such as rheumatoid arthritis and osteoporosis, is usually performed by total shoulder arthroplasty (TSA). Survival of the glenoid component is still a problem in TSA, whereas the humeral component is rarely subject to failure. To set up a finite element analysis (FEA) for simulation of a TSA in order to gain insight into the mechanical behaviour of a glenoid implant, the modelling procedure and the application of boundary conditions are of major importance because the computed result strongly depends upon the accuracy and sense of realism of the model. The goal of this study was to show the influence on glenoid stress distribution of a patient-specific bone density distribution compared with a homogenous bone density distribution for the purpose of generating a valid model in future FEA studies of the shoulder complex. Detailed information on the integration of bone density properties using existing numerical models as well as the applied boundary conditions is provided. A novel approach involving statistical analysis of values derived from an FEA is demonstrated using a cumulative distribution function. The results show well the mechanically superior behaviour of a realistic bone density distribution and therefore emphasise the necessity for patient-specific simulations in biomechanical and medical simulations.

Role of subject-specific musculoskeletal loading on the prediction of bone density distribution in the proximal femur

2014 ◽  
Vol 30 ◽  
pp. 244-252 ◽  
Author(s):  
A. Vahdati ◽  
S. Walscharts ◽  
I. Jonkers ◽  
J.M. Garcia-Aznar ◽  
J. Vander Sloten ◽  
...  
Keyword(s):  
Bone Density ◽  
Density Distribution ◽  
Proximal Femur ◽  
Subject Specific

scholarly journals Investigation of Bone Density Evolution Before and After Total Knee Arthroplasty Using a Thermodynamic-Based Framework

2021 ◽  
Author(s):  
Saeid Nazgooei
Keyword(s):  
Total Knee Arthroplasty ◽  
Bone Density ◽  
Density Distribution ◽  
Knee Arthroplasty ◽  
Fe Model ◽  
X Rays ◽  
Femoral Bone ◽  
Density Evolution ◽  
Before And After ◽  
Total Knee

In this study, a new bone remodeling model which combines mechanical loading and bone metabolism factors is used to predict the evolution of bone density after Total Knee Arthroplasty (TKA). A 3D finite element (FE) model of the distal femoral bone, coupled with a new thermodynamic-based theory (BRT), was developed in ANSYS. An axial load of 3000N was applied to the FE model, and the bone density distribution in the femoral bone was calculated. The results were then compared with those obtained from the strain energy density (SED) model and the clinical observations. This comparison showed that the bone density distribution predicted by the thermodynamic-based model before and after TKA is consistent with the structure of the distal femur obtained from X-rays. Furthermore, the predicted bone density distribution using BRT showed a gradual and uniform evolution contrary to the SED model, where there is no gradual bone density evolution.

scholarly journals Investigation of Bone Density Evolution Before and After Total Knee Arthroplasty Using a Thermodynamic-Based Framework

2021 ◽  
Author(s):  
Saeid Nazgooei
Keyword(s):  
Total Knee Arthroplasty ◽  
Bone Density ◽  
Density Distribution ◽  
Knee Arthroplasty ◽  
Fe Model ◽  
X Rays ◽  
Femoral Bone ◽  
Density Evolution ◽  
Before And After ◽  
Total Knee

In this study, a new bone remodeling model which combines mechanical loading and bone metabolism factors is used to predict the evolution of bone density after Total Knee Arthroplasty (TKA). A 3D finite element (FE) model of the distal femoral bone, coupled with a new thermodynamic-based theory (BRT), was developed in ANSYS. An axial load of 3000N was applied to the FE model, and the bone density distribution in the femoral bone was calculated. The results were then compared with those obtained from the strain energy density (SED) model and the clinical observations. This comparison showed that the bone density distribution predicted by the thermodynamic-based model before and after TKA is consistent with the structure of the distal femur obtained from X-rays. Furthermore, the predicted bone density distribution using BRT showed a gradual and uniform evolution contrary to the SED model, where there is no gradual bone density evolution.

DYNAMICS OF THERMAL LOSSES BY CONVECTION AND RADIATION OF THE SPHERICAL HEAT ACCUMULATOR OF SOLAR PLANTS

2020 ◽  
Vol 4 (41) ◽  
pp. 57-62
Author(s):  
SHAVKAT KLYCHEV ◽  
◽  
BAKHRAMOV SAGDULLA ◽  
VALERIY KHARCHENKO ◽  
VLADIMIR PANCHENKO ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Heat Loss ◽  
Initial Conditions ◽  
Water System ◽  
Heat Losses ◽  
Research Purpose ◽  
Heat Accumulator ◽  
Water Heaters ◽  
Intrinsic Radiation ◽  
Over Time

There are needed energy (heat) accumulators to increase the efficiency of solar installations, including solar collectors (water heaters, air heaters, dryers). One of the tasks of designing heat accumulators is to ensure its minimal heat loss. The article considers the problem of determining the distribution of temperatures and heat losses by convection and radiation of the heat insulation-accumulating body (water) system for a ball heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed «gap method». (Research purpose) The research purpose is in determining heat losses by convection and radiation of a two-layer ball heat accumulator with symmetric boundary conditions. (Materials and methods) Authors used the Fourier heat equation for spherical bodies. The article presents the determined boundary and initial conditions for bodies and their surfaces. (Results and discussion) The thickness of the insulation and the volume of the heat accumulator affect the dynamics and values of heat loss. The effect of increasing the thickness of the thermal insulation decreases with increasing its thickness, starting with a certain volume of the heat accumulator or with R > 0.3 meters, the heat losses change almost linearly over time. The dynamics of heat loss decreases with increasing shelf life, but the losses remain large. (Conclusions) Authors have developed a method and program for numerical calculation of heat loss and temperature over time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both falling and intrinsic radiation. The proposed method allows to unify the boundary conditions between contacting bodies.

scholarly journals Solving nonlinear third-order three-point boundary value problems by boundary shape functions methods

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Ji Lin ◽  
Yuhui Zhang ◽  
Chein-Shan Liu
Keyword(s):  
Boundary Conditions ◽  
Boundary Value Problems ◽  
Initial Conditions ◽  
Boundary Value ◽  
Accurate Solution ◽  
Point Boundary ◽  
Third Order ◽  
Boundary Shape ◽  
Free Function ◽  
New Algorithms

AbstractFor nonlinear third-order three-point boundary value problems (BVPs), we develop two algorithms to find solutions, which automatically satisfy the specified three-point boundary conditions. We construct a boundary shape function (BSF), which is designed to automatically satisfy the boundary conditions and can be employed to develop new algorithms by assigning two different roles of free function in the BSF. In the first algorithm, we let the free functions be complete functions and the BSFs be the new bases of the solution, which not only satisfy the boundary conditions automatically, but also can be used to find solution by a collocation technique. In the second algorithm, we let the BSF be the solution of the BVP and the free function be another new variable, such that we can transform the BVP to a corresponding initial value problem for the new variable, whose initial conditions are given arbitrarily and terminal values are determined by iterations; hence, we can quickly find very accurate solution of nonlinear third-order three-point BVP through a few iterations. Numerical examples confirm the performance of the new algorithms.

scholarly journals Simulation of MASPn Experiments in MISTRA Test Facility with COCOSYS Code

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
Mantas Povilaitis ◽  
Egidijus Urbonavičius
Keyword(s):  
Boundary Conditions ◽  
Nuclear Power ◽  
Power Plants ◽  
Volume Fraction ◽  
Characteristic Length ◽  
Initial Conditions ◽  
Test Facility ◽  
Work Package ◽  
Acceptable Agreement

An issue of the stratified atmospheres in the containments of nuclear power plants is still unresolved; different experiments are performed in the test facilities like TOSQAN and MISTRA. MASPn experiments belong to the spray benchmark, initiated in the containment atmosphere mixing work package of the SARNET network. The benchmark consisted of MASP0, MASP1 and MASP2 experiments. Only the measured depressurisation rates during MASPn were available for the comparison with calculations. When the analysis was performed, the boundary conditions were not clearly defined therefore most of the attention was concentrated on MASP0 simulation in order to develop the nodalisation scheme and define the initial and boundary conditions. After achieving acceptable agreement with measured depressurisation rate, simulations of MASP1 and MASP2 experiments were performed to check the influence of sprays. The paper presents developed nodalisation scheme of MISTRA for the COCOSYS code and the results of analyses. In the performed analyses, several parameters were considered: initial conditions, loss coefficient of the junctions, initial gradients of temperature and steam volume fraction, and characteristic length of structures. Parametric analysis shows that in the simulation the heat losses through the external walls behind the lower condenser installed in the MISTRA facility determine the long-term depressurisation rate.

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