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.

scholarly journals Long-term bone remodelling around ‘legendary’ cementless femoral stems

2018 ◽  
Vol 3 (2) ◽  
pp. 45-57 ◽  
Author(s):  
Charles Rivière ◽  
Guido Grappiolo ◽  
Charles A. Engh ◽  
Jean-Pierre Vidalain ◽  
Antonia-F. Chen ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Remodelling ◽  
Bone Ingrowth ◽  
Stress Shielding ◽  
Implant Design ◽  
Periprosthetic Bone ◽  
Femoral Stems ◽  
Periprosthetic Bone Loss ◽  
Load Pattern

Bone remodelling around a stem is an unavoidable long-term physiological process highly related to implant design. For some predisposed patients, it can lead to periprosthetic bone loss secondary to severe stress-shielding, which is thought to be detrimental by contributing to late loosening, late periprosthetic fracture, and thus rendering revision surgery more complicated. However, these concerns remain theoretical, since late loosening has yet to be documented among bone ingrowth cementless stems demonstrating periprosthetic bone loss associated with stress-shielding. Because none of the stems replicate the physiological load pattern on the proximal femur, each stem design is associated with a specific load pattern leading to specific adaptive periprosthetic bone remodelling. In their daily practice, orthopaedic surgeons need to differentiate physiological long-term bone remodelling patterns from pathological conditions such as loosening, sepsis or osteolysis. To aid in that process, we decided to clarify the behaviour of the five most used femoral stems. In order to provide translational knowledge, we decided to gather the designers’ and experts’ knowledge and experience related to the design rationale and the long-term bone remodelling of the following femoral stems we deemed ‘legendary’ and still commonly used: Corail (Depuy); Taperloc (Biomet); AML (Depuy); Alloclassic (Zimmer); and CLS-Spotorno (Zimmer).Cite this article: EFORT Open Rev 2018;3:45-57. DOI: 10.1302/2058-5241.3.170024

scholarly journals Analysis of Mechanical Properties and Permeability of Trabecular-Like Porous Scaffold by Additive Manufacturing

2021 ◽  
Vol 9 ◽  
Author(s):  
Long Chao ◽  
Chen Jiao ◽  
Huixin Liang ◽  
Deqiao Xie ◽  
Lida Shen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bone Repair ◽  
Bone Cells ◽  
Porous Scaffold ◽  
Bone Ingrowth ◽  
Voronoi Tessellation ◽  
Stress Shielding ◽  
Porous Scaffolds ◽  
Porous Structures ◽  
Element Analysis

Human bone cells live in a complex environment, and the biomimetic design of porous structures attached to implants is in high demand. Porous structures based on Voronoi tessellation with biomimetic potential are gradually used in bone repair scaffolds. In this study, the mechanical properties and permeability of trabecular-like porous scaffolds with different porosity levels and average apertures were analyzed. The mechanical properties of bone-implant scaffolds were evaluated using finite element analysis and a mechanical compression experiment, and the permeability was studied by computational fluid dynamics. Finally, the attachment of cells was observed by confocal fluorescence microscope. The results show that the performance of porous structures can be controlled by the initial design of the microstructure and tissue morphology. A good structural design can accurately match the performance of the natural bone. The study of mechanical properties and permeability of the porous structure can help address several problems, including stress shielding and bone ingrowth in existing biomimetic bone structures, and will also promotes cell adhesion, migration, and eventual new bone attachment.

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 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).

Development of a Biomimetic Metallic Femoral Stem: Methodological Approach

2016 ◽  
Vol 879 ◽  
pp. 1788-1793 ◽  
Author(s):  
Vladimir Brailovski ◽  
Patrick Terriault ◽  
Charles Simoneau ◽  
Mathieu Dumas ◽  
Bruno Jetté
Keyword(s):  
Porous Structure ◽  
Numerical Models ◽  
Methodological Approach ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Image Correlation ◽  
Implant Design ◽  
Reference Case ◽  
Outer Skin ◽  
Numerical Predictions

In this communication, a new methodological approach is proposed to develop a biomimetic metallic femoral stem. The design of this stem starts with the definition of an outer skin by reproducing the shape and overall dimensions of a Stryker® femoral stem to be implanted in an artificial femur model from Sawbones®. In-house algorithms are then used to generate two types of porous structures inside the outer skin: either a stochastic cubic-based porous structure or an ordered diamond-type porous structure. Next, a model of the femur-stem assembly is developed using the finite element method. The fully dense Stryker stem replica and two porous stems are fabricated using selective laser melting technology. Then, comparative mechanical testing is carried out using the ISO 7206-4 (2010) guidelines. These tests are conducted on an intact artificial femur (reference case) and on the identical femurs, but now implanted with the fully dense and porous stems. Using digital image correlation tools, the results of four series of tests are compared to assess which implant design leads to the lowest stress shielding in the implanted femur. Finally, the experimentally measured strain fields are compared to the numerical predictions to validate the numerical models.

scholarly journals Distal Femoral Cortical Hypertrophy after Hip Arthroplasty Using a Cementless Double-Tapered Femoral Stem

2016 ◽  
Vol 24 (3) ◽  
pp. 317-322 ◽  
Author(s):  
Yoon Je Cho ◽  
Young Soo Chun ◽  
Kee Hyung Rhyu ◽  
Jong Hun Baek ◽  
Hu Liang
Keyword(s):  
Clinical Outcome ◽  
Hip Arthroplasty ◽  
Stress Shielding ◽  
Femoral Stem ◽  
Visual Analogue Score ◽  
Thigh Pain ◽  
Harris Hip Score ◽  
Cortical Hypertrophy ◽  
Flare Index ◽  
The Mean

Purpose To review 437 hips in 404 patients who underwent total hip arthroplasty (THA) or hemiarthroplasty using the Accolade TMZF stem to determine the incidence and risk factors of distal femoral cortical hypertrophy (DFCH). Methods Records of 437 hips in 169 men and 235 women aged 26 to 100 (mean, 65.7) years who underwent THA (n=293) or hemiarthroplasty (n=144) using the Accolade TMZF femoral stem by 2 senior surgeons and were followed up for a mean of 54.7 months were reviewed. Clinical outcome was assessed using the modified Harris Hip Score and visual analogue score for pain. Proximal femoral geometry and canal flare index were assessed on preoperative radiographs, and DFCH, stem position, subsidence, loosening, and stress shielding were assessed on postoperative radiographs according to the Gruen zone. Results Of 437 hips, 27 (6.2%) developed DFCH and 410 did not. Hips with DFCH had a higher incidence of thigh pain (18.5% vs. 2.2%, p<0.001) and earlier onset of thigh pain (12.3 vs. 20.8 months, p=0.015), compared with those without. Nonetheless, all femoral stems were well-fixed, and no osteolysis or loosening was detected. The 2 groups achieved comparable clinical outcome in terms of Harris Hip Score and pain. The mean canal flare index was higher in hips with than without DFCH (3.706 vs. 3.294, p=0.002). The mean vertical subsidence of the femoral stem was lower in hips with than without DFCH (1.5 vs. 3.4 mm p<0.001). Subsidence negatively correlated with the canal flare index (correlation coefficient= −0.110, p=0.022). The incidence of the DFCH increased with each unit of increment in canal flare index (odds ratio [OR]=1.828, p=0.043) and each year younger in age (OR=0.968, p=0.015). Conclusion The incidence of DFCH in hips with the Accolade TMZF stem was 6.2%. Patients with a higher canal flare index and younger age had a higher incidence of DFCH. Nonetheless, DFCH did not affect clinical outcome or femoral stem stability.

Finite Element Assessment of a Porous Tibial Implant Design Using Rhombic Dodecahedron Structure

2021 ◽  
Vol 318 ◽  
pp. 71-81
Author(s):  
Basma Eltlhawy ◽  
Tawfik El-Midany ◽  
Noha Fouda ◽  
Ibrahim Eldesouky
Keyword(s):  
Finite Element ◽  
Clinical Performance ◽  
Bone Ingrowth ◽  
Maximum Shear Stress ◽  
Compressive Loading ◽  
Stress Shielding ◽  
Titanium Implant ◽  
Implant Design ◽  
Implant Fixation ◽  
Rhombic Dodecahedron

The current research presents a novel porous tibia implant design based on porous structure. The implant proximal portion was designed as a porous rhombic dodecahedron structure with 500 μm pore size. Finite element method (FEM) was used to assess the stem behavior under compressive loading compared to a solid stem model. CATIA V5R18 was used for modeling both rhombic dodecahedron and full solid models. Static structural analysis was carried out using ANSYS R18.1 to asses the implant designs. The results indicated enhanced clinical performance of tibial-knee implants compared to the solid titanium implant via increasing the maximum von-Mises stresses by 64% under the tibial tray in porous implant which reduce stress shielding. Also, the maximum shear stress developed in bone/implant interface was reduced by 68% combined with relieving the stress concentration under the stem tip to relieve patients' pain. Finally, porous implants provide cavities for bone ingrowth which improve implant fixation.

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