Shape Optimization of Femoral Components of an Artificial Hip Prosthesis Using the Three-Dimensional P-Version Finite Element Study and the In Vitro Measurement of Strain in the Bone Cement

2002 ◽  
Author(s):  
Masaru Higa ◽  
Ikuya Nishimura ◽  
Kazuhiro Matsuda ◽  
Hiromasa Tanino ◽  
Yoshinori Mitamura
Keyword(s):  
Finite Element ◽  
Shape Optimization ◽  
Bone Cement ◽  
Femoral Component ◽  
Three Dimensional ◽  
Femoral Stem ◽  
Cement Mantle ◽  
Optimum Shape ◽  
Shear Stresses

Though Total Hip Arthroplasty (THA) is being performed with greater frequency every year for patients with endstage arthritis of hip, mechanical fatigue of bone cement leading to damage accumulation is implicated in the loosening of cemented hip components. This fatigue failure of bone cement has been reported to be the result of high tensile and shear stresses at the bone cement. The aim of this study is to design the optimum shape of femoral component of a THA that minimizes the peak stress value of maximum principal stress at the bone cement and to validate the FEM results by comparing numerical stress with experimental ones. The p-version three-dimensional Finite Element Method (FEM) combined with an optimization procedure was used to perform the shape optimization. Moreover the strain in the cement mantle surrounding the cemented femoral component of a THA was measured in vitro using strain gauges embedded within the cement mantle adjacent to the developed femoral stem to validate the optimization results of FEM.

scholarly journals In Vitro Fatigue Failure of Cemented Acetabular Replacements: A Hip Simulator Study

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
N. P. Zant ◽  
P. Heaton-Adegbile ◽  
J. G. Hussell ◽  
J. Tong
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Bone Cement ◽  
Cement Mantle ◽  
Stair Climbing ◽  
Normal Walking ◽  
Element Analysis ◽  
Cement Interface ◽  
Hip Simulator

Although hip simulators for in vitro wear testing of prosthetic materials used in total hip arthroplasty (THA) have been available for a number of years, similar equipment has yet to appear for endurance testing of fixation in cemented THA, despite considerable evidence of late aseptic loosening as one of the most significant failure mechanisms in this type of replacements. An in vitro study of fatigue behavior in cemented acetabular replacements has been carried out, utilizing a newly developed hip simulator. The machine was designed to simulate the direction and the magnitude of the hip contact force under typical physiological loading conditions, including normal walking and stair climbing, as reported by Bergmann et al. (2001, Hip 98, Freie Universitaet, Berlin). A 3D finite element analysis has been carried out to validate the function of the hip simulator and to evaluate the effects of boundary conditions and geometry of the specimen on the stress distribution in the cement mantle. Bovine pelvic bones were implanted with a Charnley cup, using standard manual cementing techniques. Experiments were carried out under normal walking and descending stairs loading conditions with selected load levels from a body weight of 75–125kg. Periodically, the samples were removed from the test rigs to allow CT scanning for the purpose of monitoring damage development in the cement fixation. The hip simulator was found to be satisfactory in reproducing the hip contact force during normal walking and stair climbing, as reported by Bergmann et al. Finite element analysis shows that the stress distributions in the cement mantle and at the bone-cement interface are largely unaffected by the geometry and the boundary conditions of the model. Three samples were tested up to 17×106cycles and sectioned post-testing for microscopic studies. Debonding at the bone-cement interface of various degrees in the posterior-superior quadrant was revealed in these samples, and the location of the failures corresponds to the highest stressed region from the finite-element analysis. Preliminary experimental results from a newly developed hip simulator seem to suggest that debonding at the bone-cement interface is the main failure mechanism in cemented acetabular replacements, and descending stairs seem to be more detrimental than normal walking or ascending stairs with regard to fatigue integrity of cement fixation.

THREE-DIMENSIONAL SHAPE OPTIMIZATION OF FEMORAL COMPONENT OF HIP PROSTHESES WITH NONLINEAR FRICTIONAL INTERFACE

2004 ◽  
Vol 04 (02) ◽  
pp. 161-172
Author(s):  
HAMID KATOOZIAN ◽  
DWIGHT T. DAVY
Keyword(s):  
Shape Optimization ◽  
Femoral Component ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Interface Condition ◽  
Shear Stresses ◽  
Element Analysis ◽  
Dimensional Shape ◽  
Three Dimensional Shape

A numerical procedure was implemented for the three-dimensional shape optimization of femoral component of total hip replacements. An algorithm was developed for defining the component geometry in terms of longitudinal and cross-sectional shape variables. The three-dimensional design model was combined with a non-linear 3-D finite element analysis and a numerical optimization procedure. An idealized femoral geometry and a frictional contact were used for bone-implant interfaces. The design objective was to reduce the shear stresses and the relative motion between implant and the surrounding bone along the interface region. The general trend in all design optimization was to produce a somewhat bulky implant with a more rectangular cross section. The outcome was more strongly affected by interface condition than choice of objective function.

Reduction of Free-Edge Stress Concentration

1985 ◽  
Vol 52 (4) ◽  
pp. 801-805 ◽  
Author(s):  
P. R. Heyliger ◽  
J. N. Reddy
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Free Edge ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Interlaminar Shear ◽  
Three Dimensional Elasticity

A quasi-three dimensional elasticity formulation and associated finite element model for the stress analysis of symmetric laminates with free-edge cap reinforcement are described. Numerical results are presented to show the effect of the reinforcement on the reduction of free-edge stresses. It is observed that the interlaminar normal stresses are reduced considerably more than the interlaminar shear stresses due to the free-edge reinforcement.

THE INFLUENCE OF TIBIAL PROSTHESIS DESIGN FEATURES ON STRESSES RELATED TO ASEPTIC LOOSENING AND STRESS SHIELDING

2011 ◽  
Vol 11 (01) ◽  
pp. 55-72 ◽  
Author(s):  
DESMOND Y. R. CHONG ◽  
ULRICH N. HANSEN ◽  
ANDREW A. AMIS
Keyword(s):  
Bone Resorption ◽  
Bone Cement ◽  
Aseptic Loosening ◽  
Cancellous Bone ◽  
Stress Shielding ◽  
Cement Mantle ◽  
Shear Stresses ◽  
Knee Prostheses ◽  
Design Features ◽  
Cement Interface

Aseptic loosening caused by mechanical factors is a recognized failure mode for tibial components of knee prostheses. This parametric study investigated the effects of prosthesis fixation design changes, which included the presence, length and diameter of a central stem, the use of fixation pegs beneath the tray, all-polyethylene versus metal-backed tray, prosthesis material stiffness, and cement mantle thickness. The cancellous bone compressive stresses and bone–cement interfacial shear stresses, plus the reduction of strain energy density in the epiphyseal cancellous bone, an indication of the likelihood of component loosening, and bone resorption secondary to stress shielding, were examined. Design features such as longer stems reduced bone and bone–cement interfacial stresses thus the risk of loosening is potentially minimized, but at the expense of an increased tendency for bone resorption. The conflicting trend suggested that bone quality and fixation stability have to be considered mutually for the optimization of prosthesis designs. By comparing the bone stresses and bone–cement shear stresses to reported fatigue strength, it was noted that fatigue of both the cancellous bone and bone–cement interface could be the driving factor for long-term aseptic loosening for metal-backed tibial trays.

scholarly journals Biomechanical assessment of different fixation methods in mandibular high sagittal oblique osteotomy using a three-dimensional finite element analysis model

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Charles Savoldelli ◽  
Elodie Ehrmann ◽  
Yannick Tillier
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Three Dimensional ◽  
Von Mises Stress ◽  
Analysis Model ◽  
Element Analysis ◽  
Fixation Methods ◽  
Oblique Osteotomy ◽  
Von Mises

AbstractWith modern-day technical advances, high sagittal oblique osteotomy (HSOO) of the mandible was recently described as an alternative to bilateral sagittal split osteotomy for the correction of mandibular skeletal deformities. However, neither in vitro nor numerical biomechanical assessments have evaluated the performance of fixation methods in HSOO. The aim of this study was to compare the biomechanical characteristics and stress distribution in bone and osteosynthesis fixations when using different designs and placing configurations, in order to determine a favourable plating method. We established two finite element models of HSOO with advancement (T1) and set-back (T2) movements of the mandible. Six different configurations of fixation of the ramus, progressively loaded by a constant force, were assessed for each model. The von Mises stress distribution in fixations and in bone, and bony segment displacement, were analysed. The lowest mechanical stresses and minimal gradient of displacement between the proximal and distal bony segments were detected in the combined one-third anterior- and posterior-positioned double mini-plate T1 and T2 models. This suggests that the appropriate method to correct mandibular deformities in HSOO surgery is with use of double mini-plates positioned in the anterior one-third and posterior one-third between the bony segments of the ramus.

Axisymmetric Finite Element Analysis of a Debonded Total Hip Stem With an Unsupported Distal Tip

1996 ◽  
Vol 118 (3) ◽  
pp. 399-404 ◽  
Author(s):  
T. L Norman ◽  
V. C. Saligrama ◽  
K. T. Hustosky ◽  
T. A. Gruen ◽  
J. D. Blaha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Relaxation ◽  
Bone Cement ◽  
Cement Mantle ◽  
Load Level ◽  
Interface Conditions ◽  
Element Analysis ◽  
Cement Interface ◽  
Total Hip

A tapered femoral total hip stem with a debonded stem-cement interface and an unsupported distal tip subjected to constant axial load was evaluated using two-dimensional (2D) axisymmetric finite element analysis. The analysis was performed to test if the mechanical condition suggest that a “taper-lock” with a debonded viscoelastic bone cement might be an alternative approach to cement fixation of stem type cemented hip prosthesis. Effect of stem-cement interface conditions (bonded, debonded with and without friction) and viscoelastic response (creep and relaxation) of acrylic bone cement on cement mantle stresses and axial displacement of the stem was also investigated. Stem debonding with friction increased maximum cement von Mises stress by approximately 50 percent when compared to the bonded stem. Of the stress components in the cement mantle, radial stresses were compressive and hoop stresses were tensile and were indicative of mechanical taper-lock. Cement mantle stress, creep and stress relaxation and stem displacement increased with increasing load level and with decreasing stem-cement interface friction. Stress relaxation occur predominately in tensile hoop stress and decreased from 1 to 46 percent over the conditions considered. Stem displacement due to cement mantle creep ranged from 614 μm to 1.3 μm in 24 hours depending upon interface conditions and load level.

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