Selection Methodology of Femoral Stems According to the Cross Section and the Maximum Stresses

2021 ◽  
Author(s):  
Ivan Camilo Lopez Galiano ◽  
Mario Juha ◽  
Juan Guillermo Ortiz Martínez ◽  
Julian Mauricio Echeverry Mejia
Keyword(s):  
Cross Section ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Theoretical Development ◽  
Shielding Effect ◽  
Average Error ◽  
Femoral Stems ◽  
The Cross ◽  
Selection Methodology ◽  
Maximum Stresses

Abstract The maximum stresses on a femoral stem must be known for selecting the right size and shape of the shaft cross-sectional area for reducing the stress shielding effect generated after the total hip arthroplasty (THA) surgical procedure. The methodology proposed in this study provides the tools to the designers of femoral stems and orthopedic surgeons to select the adequate femoral stem cross section, decreasing the stiffness of the stem, thus reducing the stress shielding effect in the patient bones. The first contribution is the theoretical development of the maximum static stress calculation for 12 different femoral stem models with the beam theory, followed by the comparison with the static finite element analysis (FEA) simulations and finally the experimental corroboration of one femoral stem model measuring the strain with linear strain gages and transform it to stresses, the three different approaches provide comparable results, with a maximum average error of less than 8.5%. The second contribution is the formulation of a new selection methodology based on maximum stresses in the femoral stem and the cross-section area for decreasing the stress shielding effect, optimizing the area needed for withstand the loads and decreasing the overall stiffens of the stem.

scholarly journals A novel design, analysis and 3D printing of Ti-6Al-4V alloy bio-inspired porous femoral stem

2020 ◽  
Vol 31 (9) ◽  
Author(s):  
Hassan Mehboob ◽  
Faris Tarlochan ◽  
Ali Mehboob ◽  
Seung-Hwan Chang ◽  
S. Ramesh ◽  
...  
Keyword(s):  
Stress Shielding ◽  
Femoral Stem ◽  
Fatigue Load ◽  
Porous Ti ◽  
Femoral Stems ◽  
Dense Part ◽  
Bcc Structure ◽  
Dense Shell ◽  
Porous Part ◽  
Novel Design

Abstract The current study is proposing a design envelope for porous Ti-6Al-4V alloy femoral stems to survive under fatigue loads. Numerical computational analysis of these stems with a body-centered-cube (BCC) structure is conducted in ABAQUS. Femoral stems without shell and with various outer dense shell thicknesses (0.5, 1.0, 1.5, and 2 mm) and inner cores (porosities of 90, 77, 63, 47, 30, and 18%) are analyzed. A design space (envelope) is derived by using stem stiffnesses close to that of the femur bone, maximum fatigue stresses of 0.3σys in the porous part, and endurance limits of the dense part of the stems. The Soderberg approach is successfully employed to compute the factor of safety Nf > 1.1. Fully porous stems without dense shells are concluded to fail under fatigue load. It is thus safe to use the porous stems with a shell thickness of 1.5 and 2 mm for all porosities (18–90%), 1 mm shell with 18 and 30% porosities, and 0.5 mm shell with 18% porosity. The reduction in stress shielding was achieved by 28%. Porous stems incorporated BCC structures with dense shells and beads were successfully printed.

scholarly journals Optimal design and biomechanical simulation analysis of femoral stem based on trabecular bone structure

2020 ◽  
Author(s):  
Junjun Bai ◽  
Yi Feng ◽  
Jia Lv ◽  
Zhi Lv ◽  
Chaojian Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Trabecular Bone ◽  
Bone Growth ◽  
Bone Structure ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Trabecular Bone Structure ◽  
Shielding Effect ◽  
Round Hole ◽  
Secondary Fracture

Abstract Background:In orthopaedic clinical treatment, the rigidity mismatch between prosthesis and bone will cause stress shielding phenomenon, affecting bone growth and leading to aseptic loosening and prosthesis failure, and thus a more serious secondary fracture.Purpose:In this paper, the femur stem finite element model of human body standing on one foot and two feet was established, and the biomechanical properties of femur stems with three different structural designs were compared and analyzed, so as to provide theoretical guidance for the structural design and finite element simulation of femur stem.Method: Round-hole femoral stem model and trabecular structural model were established via 3-matic software based on solid femoral stem model. Meshing work was performed by the finite element pre-processing software Hypermesh. The finite element analysis software Abaqus is introduced to analyze the mechanical characteristics of the models for simulating the two different motion conditions of human standing on one foot and on two feet. Results and discussion: The results showed that stress concentration occurred in the femoral neck of all the prostheses with different motion conditions. The stress and displacement values of the three prosthesis models are about twice as much as those of the two-feet models when standing on one foot. The stress and displacement values of the trabecular femoral stem prosthesis were. The stress distribution of femoral stem prosthesis with trabecular bone structure was more uniform, and the force conduction was more obvious, which can effectively reduce the stress shielding effect and was beneficial to the patients’ rehabilitation.

scholarly journals Femoral Stems With Porous Lattice Structures: A Review

2021 ◽  
Vol 9 ◽  
Author(s):  
Bolun Liu ◽  
Huizhi Wang ◽  
Ningze Zhang ◽  
Min Zhang ◽  
Cheng-Kung Cheng
Keyword(s):  
Porous Structure ◽  
Bone Ingrowth ◽  
Evaluation Research ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Geometric Design ◽  
Porous Structures ◽  
Femoral Stems ◽  
Manufacturing Techniques ◽  
Secondary Function

Cementless femoral stems are prone to stress shielding of the femoral bone, which is caused by a mismatch in stiffness between the femoral stem and femur. This can cause bone resorption and resultant loosening of the implant. It is possible to reduce the stress shielding by using a femoral stem with porous structures and lower stiffness. A porous structure also provides a secondary function of allowing bone ingrowth, thus improving the long-term stability of the prosthesis. Furthermore, due to the advent of additive manufacturing (AM) technology, it is possible to fabricate femoral stems with internal porous lattices. Several review articles have discussed porous structures, mainly focusing on the geometric design, mechanical properties and influence on bone ingrowth. However, the safety and effectiveness of porous femoral stems depend not only on the characteristic of porous structure but also on the macro design of the femoral stem; for example, the distribution of the porous structure, the stem geometric shape, the material, and the manufacturing process. This review focuses on porous femoral stems, including the porous structure, macro geometric design of the stem, performance evaluation, research methods used for designing and evaluating the femoral stems, materials and manufacturing techniques. In addition, this review will evaluate whether porous femoral stems can reduce stress shielding and increase bone ingrowth, in addition to analyzing their shortcomings and related risks and providing ideas for potential design improvements.

Minimizing Stress Shielding Effect of Femoral Stem—A Review

2013 ◽  
Vol 3 (2) ◽  
pp. 171-178
Author(s):  
Palash Kumar Maji ◽  
Amit Roychowdhury ◽  
Debasis Datta
Keyword(s):  
Stress Shielding ◽  
Femoral Stem ◽  
Shielding Effect

scholarly journals Risk-Based Analysis of Femoral Stem Considering Uncertainty in its Design Parameters

2019 ◽  
Author(s):  
Godlove Wanki ◽  
Stephen Ekwaro-Osire ◽  
João Paulo Dias ◽  
Americo Cunha
Keyword(s):  
Stress Shielding ◽  
Femoral Stem ◽  
Element Model ◽  
Design Parameters ◽  
Analysis Method ◽  
Femoral Stems ◽  
Femoral Implants ◽  
Simplified Finite Element Model ◽  
Uncertainty In Design ◽  
Arthroplasty Surgery

The number of young people getting total hip arthroplasty surgery is on the rise and studies have shown that the average number of perfect health years after such surgery is being reduced to about 9 years; this is because of complications which can lead to the failure of such implants. Consequently, such failures cause the implant not to last as long as required. The uncertainty in design parameters, loading, and even the manufacturing process of femoral stems, makes it important to consider uncertainty quantification and probabilistic modeling approaches instead of the traditional deterministic approach when designing femoral stems. This paper proposes a probabilistic analysis method which considers uncertainties in the design parameters of femoral implants to determine its effect on the implant stiffness. Accordingly, this method can be used to improve the design reliability of femoral stems. A simplified finite element model of a femoral stem was considered and analyzed both deterministically and probabilistically using Monte Carlo simulation. The results showed that uncertainties in design parameters can significantly affect the resulting stiffness of the stem. This paper proposes an approach that can be considered a potential solution for improving, in general, the reliability of hip implants and the predicted stiffness values for the femoral stems so as to better mitigate the stress shielding phenomenon.

scholarly journals Long-Term Results of Hip Arthroplasty Using Extensive Porous-Coated Stem—A Minimum Follow-Up of 15 Years

2019 ◽  
Vol 10 ◽  
pp. 215145931989278
Author(s):  
Myung Hoon Park ◽  
Yung Hun Youn ◽  
Joon Soon Kang ◽  
Kyoung Ho Moon
Keyword(s):  
Heterotopic Ossification ◽  
Hip Arthroplasty ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Long Term Results ◽  
Harris Hip Score ◽  
Radiographic Findings ◽  
Femoral Stems

Introduction: We report the clinical and radiographic results of hip arthroplasty using extensive porous-coated stems over 15 years in Korea. Methods: This retrospective study included 210 patients (268 hips) who underwent total hip arthroplasties (232 hips) and bipolar hemiarthroplasties (36 hips) between June 1996 and December 2002 for avascular necrosis of the femoral head, hip fracture, or osteoarthritis, after excluding those who died or were lost to follow-up. One senior author (K.H.M.) evaluated Harris Hip Score (HHS); limping gait; and leg length discrepancy, and 3 independent reviewers assessed the radiographic findings, including the level of stress shielding, Dorr classification, subsidence and loosening of femoral stem, heterotopic ossification (Brooker classification), osteolysis of acetabulum, wear rate of the polyethylene liner, component loosening, and revision rate. Results: The mean follow-up duration was 16.9 years and average age at operation was 50.9 years. The HHS improved at the last follow-up. Stress shielding was grade 1 in 185 hips, grade 2 in 35 hips, grade 3 in 37 hips, and grade 4 in 11 hips. Femoral stem subsidence was <3 mm in 4 hips and >3 mm in 6 hips. Femoral stems with stable bony ingrowth were observed in 258 hips, fibrous stable femoral stems in 4 hips, and unstable femoral stems in 6 hips. Heterotopic ossification was class 1 in12 and class 2 in 4 hips. Revision surgery was performed for periprosthetic osteolysis of cup (45 hips), recurrent dislocation (1), unstable femoral stem (1), and infection (1). The Kaplan-Meier survivorship at the 15-year follow-up was 86.2%. The survivorship of femoral stem at 15 years was 99.3%, and if including impending revision due to unstable femoral stem was 97.1%. Disscussion: This study has all the limitations inherent with a retrospective design. However, a large number of patients in this cohort operated on by a single surgeon and a long-term follow-up are some of the potential advantages of the current study. Conclusions: At the 15-year follow-up, extensive porous-coated stem showed relatively good survivorship even in geriatric patients (Dorr type C).

An operational approach to real-time dynamic measurement of discharge

2013 ◽  
Vol 44 (6) ◽  
pp. 953-964 ◽  
Author(s):  
V. Alessandrini ◽  
G. Bernardi ◽  
E. Todini
Keyword(s):  
Cross Section ◽  
Maximum Velocity ◽  
Theoretical Development ◽  
Surface Velocity ◽  
Time Dynamic ◽  
Microwave Sensor ◽  
The Cross ◽  
Point Velocity ◽  
Two Parameters ◽  
Microwave Sensors

Based on the maximization of entropy, microwave sensors are becoming standard approaches for converting point surface velocity measurements into discharge. Unfortunately, this conversion is conditioned by cross-section regularity and by the need to take the surface measures above the vertical where the maximum velocity occurs. Cross-section irregularities and the presence of floodplains, vegetation and/or local bed depressions can change the theoretical applicability conditions of the proposed methods and, due to the wandering of the current, the microwave sensor must be continuously moved to track the maximum velocity. We describe the theoretical development and practical application of a new approach to operationally convert surface velocity and water level, measured using a fixed installation, into discharge. The resulting equation that links the surface point velocity measurement to the discharge is a function of two parameters describing the velocity distribution within the cross-section plus an additional correction factor which describes the non-homogeneity of the different vertical slices into which the cross-section is divided. Interesting results of the approach are shown for the gauging section of Tavagnasco on the Dora Baltea River in Italy with high performances both in terms of calibration and validation.

A New Approach to the Demonstration of Oxidase-Localization Using Tannic Acid Or Catechin

1973 ◽  
Vol 31 ◽  
pp. 698-699
Author(s):  
V. Mizuhira ◽  
Y. Futaesaku
Keyword(s):  
Cross Section ◽  
Tannic Acid ◽  
Elastic Fiber ◽  
The Other ◽  
New Approach ◽  
Tissue Block ◽  
Active Reaction ◽  
The Cross

Previously we reported that tannic acid is a very effective fixative for proteins including polypeptides. Especially, in the cross section of microtubules, thirteen submits in A-tubule and eleven in B-tubule could be observed very clearly. An elastic fiber could be demonstrated very clearly, as an electron opaque, homogeneous fiber. However, tannic acid did not penetrate into the deep portion of the tissue-block. So we tried Catechin. This shows almost the same chemical natures as that of proteins, as tannic acid. Moreover, we thought that catechin should have two active-reaction sites, one is phenol,and the other is catechole. Catechole site should react with osmium, to make Os- black. Phenol-site should react with peroxidase existing perhydroxide.

Energy Distribution in Electron Beams

1972 ◽  
Vol 30 ◽  
pp. 568-569
Author(s):  
Tamotsu Ohno
Keyword(s):  
Electron Beam ◽  
Energy Distribution ◽  
Cross Section ◽  
Integral Curve ◽  
Electron Beams ◽  
Electron Gun ◽  
Angular Divergence ◽  
Apparent Increase ◽  
Integral Width ◽  
The Cross

The energy distribution in an electron; beam from an electron gun provided with a biased Wehnelt cylinder was measured by a retarding potential analyser. All the measurements were carried out with a beam of small angular divergence (<3xl0-4 rad) to eliminate the apparent increase of energy width as pointed out by Ichinokawa.The cross section of the beam from a gun with a tungsten hairpin cathode varies as shown in Fig.1a with the bias voltage Vg. The central part of the beam was analysed. An example of the integral curve as well as the energy spectrum is shown in Fig.2. The integral width of the spectrum ΔEi varies with Vg as shown in Fig.1b The width ΔEi is smaller than the Maxwellian width near the cut-off. As |Vg| is decreased, ΔEi increases beyond the Maxwellian width, reaches a maximum and then decreases. Note that the cross section of the beam enlarges with decreasing |Vg|.

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