Experimental and Finite Element Comparaison of Various Joint Fixation Designs

1999 ◽  
Author(s):  
O. Patenaude ◽  
A. Shirazi-Adl ◽  
M. Dammak
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Bone Ingrowth ◽  
Element Model ◽  
Bone Implant ◽  
Combined Loads ◽  
Pull Out ◽  
Initial Fixation ◽  
Fixation Stability ◽  
Friction Models

Abstract The short- and long-term success of tibial cementless implants depends on the initial fixation stability provided primarily by posts and screws. Excessive relative motions at the bone-implant interface are known to inhibit bone ingrowth and, hence, biologic fixation. In this work, the performance of a number of fixation configurations under static and fatigue combined loads (i.e., compression plus shear) is investigated both experimentally and numerically. These results will permit both to compare different fixation types and to serve to validate a 3D finite element model that incorporates the measured nonlinear bone-implant friction and posts/screws pull-out tests. Once validated, the finite element model is also used to study the effect of different bone-implant friction models for porous coated posts and plate and of loading order of application on predictions.

Comparison of femur strain under different loading scenarios: Experimental testing

2020 ◽  
Vol 235 (1) ◽  
pp. 17-27
Author(s):  
Ievgen Levadnyi ◽  
Jan Awrejcewicz ◽  
Yan Zhang ◽  
Yaodong Gu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Strain Distribution ◽  
Element Model ◽  
Surface Strain ◽  
Image Correlation ◽  
Loading Conditions ◽  
Bone Implant ◽  
Bone Stiffness

Bone fracture, formation and adaptation are related to mechanical strains in bone. Assessing bone stiffness and strain distribution under different loading conditions may help predict diseases and improve surgical results by determining the best conditions for long-term functioning of bone-implant systems. In this study, an experimentally wide range of loading conditions (56) was used to cover the directional range spanned by the hip joint force. Loads for different stance configurations were applied to composite femurs and assessed in a material testing machine. The experimental analysis provides a better understanding of the influence of the bone inclination angle in the frontal and sagittal planes on strain distribution and stiffness. The results show that the surface strain magnitude and stiffness vary significantly under different loading conditions. For the axial compression, maximal bending is observed at the mid-shaft, and bone stiffness is also maximal. The increased inclination leads to decreased stiffness and increased magnitude of maximum strain at the distal end of the femur. For comparative analysis of results, a three-dimensional, finite element model of the femur was used. To validate the finite element model, strain gauges and digital image correlation system were employed. During validation of the model, regression analysis indicated robust agreement between the measured and predicted strains, with high correlation coefficient and low root-mean-square error of the estimate. The results of stiffnesses obtained from multi-loading conditions experiments were qualitatively compared with results obtained from a finite element analysis of the validated model of femur with the same multi-loading conditions. When the obtained numerical results are qualitatively compared with experimental ones, similarities can be noted. The developed finite element model of femur may be used as a promising tool to estimate proximal femur strength and identify the best conditions for long-term functioning of the bone-implant system in future study.

Axial Strength of Tube-to-Tubesheet Joints: Finite Element and Experimental Evaluations

2001 ◽  
Vol 124 (1) ◽  
pp. 22-31 ◽  
Author(s):  
M. Allam ◽  
A. Bazergui
Keyword(s):  
Finite Element ◽  
Analytical Solution ◽  
Finite Element Model ◽  
Experimental Testing ◽  
Element Model ◽  
Axial Strength ◽  
Pull Out ◽  
Push Out ◽  
Pull Out Strength ◽  
The Finite Element Model

Because of their importance for the integrity of heat exchangers, the strength of tube-to-tubesheet joints, and particularly their axial strength, is of special interest. A finite element model of an expanded tube-to-tubesheet joint is proposed and examined experimentally with the objective of determining numerically its axial strength. Simplified analytical methods that were previously proposed by many authors to predict the joint axial strength are also used in this investigation. Experimental testing shows that the finite element model is highly accurate for calculating the joint axial strength. The experimental investigation also proves that the pull-out strength is overestimated when calculated using a simple analytical solution. A parametric analysis using the finite element results indicates that the pull-out force is normally lower than the push-out load and that both are lower than the estimations of the analytical solution. The results indicate that the pull-out force as given by the finite element model is generally 35 percent lower than that evaluated by the analytical solution. A difference of as much as 10 percent is also found between the push-out and pull-out loads.

Cortical Bone Viscoelasticity and Fixation Strength of Press-Fit Femoral Stems: A Finite Element Model

2005 ◽  
Vol 128 (1) ◽  
pp. 7-12 ◽  
Author(s):  
T. R. Shultz ◽  
J. D. Blaha ◽  
T. A. Gruen ◽  
T. L. Norman
Keyword(s):  
Finite Element ◽  
Stress Relaxation ◽  
Finite Element Model ◽  
Cortical Bone ◽  
Coefficient Of Friction ◽  
Viscoelastic Behavior ◽  
Element Model ◽  
Press Fit ◽  
Initial Fixation ◽  
Push Out

Many cementless implant designs rely upon a diaphyseal press-fit in conjunction with a porous coated implant surface to achieve primary or short term fixation, thereby constraining interface micromotion to such a level that bone ingrowth and consequent secondary or long-term fixation, i.e., osseointegration, can occur. Bone viscoelasticity, however, has been found to affect stem primary stability by reducing push-out load. In this investigation, an axisymmetric finite element model of a cylindrical stem and diaphyseal cortical bone section was created in order to parametrically evaluate the effect of bone viscoelasticity on stem push-out while controlling coefficient of friction (μ=0.15, 0.40, and 1.00) and stem-bone diametral interference (δ=0.01, 0.05, 0.10, and 0.50mm). Based on results from a previous study, it was hypothesized that stem-bone interference (i.e., press-fit) would elicit a bone viscoelastic response which would reduce the initial fixation of the stem as measured by push-out load. Results indicate that for all examined combinations of μ and δ, bone viscoelastic behavior reduced the push-out load by a range of 2.6–82.6% due to stress relaxation of the bone. It was found that the push-out load increased with μ for each value of δ, but minimal increases in the push-out load (2.9–4.9%) were observed as δ was increased beyond 0.10mm. Within the range of variables reported for this study, it was concluded that bone viscoelastic behavior, namely stress relaxation, has an asymptotic affect on stem contact pressure, which reduces stem push-out load. It was also found that higher levels of coefficient of friction are beneficial to primary fixation, and that an interference “threshold” exists beyond which no additional gains in push-out load are achieved.

A Finite Element Model for Bone Ingrowth into a Prosthesis

2008 ◽  
pp. 99-106
Author(s):  
F. J. Vermolen ◽  
E. M. van Aken ◽  
J. C. van der Linden ◽  
A. Andreykiv
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Bone Ingrowth ◽  
Element Model
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