scholarly journals Minimizing Stress Shielding and Cement Damage in Cemented Femoral Component of a Hip Prosthesis through Computational Design Optimization

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Abdellah Ait Moussa ◽  
Justin Fischer ◽  
Rohan Yadav ◽  
Morshed Khandaker
Keyword(s):  
Hip Prosthesis ◽  
Numerical Technique ◽  
Stress Shielding ◽  
Computational Design ◽  
Functionally Graded ◽  
Implant Design ◽  
Homogeneous Material ◽  
Element Analysis ◽  
Term Survival

The average life expectancy of many people undergoing total hip replacement (THR) exceeds twenty-five years and the demand for implants that increase the load-bearing capability of the bone without affecting the short- or long-term stability of the prosthesis is high. Mechanical failure owing to cement damage and stress shielding of the bone are the main factors affecting the long-term survival of cemented hip prostheses and implant design must realistically adjust to balance between these two conflicting effects. In the following analysis we introduce a novel methodology to achieve this objective, the numerical technique combines automatic and realistic modeling of the implant and embedding medium, and finite element analysis to assess the levels of stress shielding and cement damage and, finally, global optimization, using orthogonal arrays and probabilistic restarts, were used. Applications to implants, fabricated using a homogeneous material and a functionally graded material, were presented.

scholarly journals Outcome after Two Sequential Revision Hip Arthroplasties for CoC Bearing Fracture with 10 Years Follow-up: A Case Report

2021 ◽  
Vol 11 (7) ◽  
Author(s):  
Matevž Topolovec ◽  
Ingrid Milošev ◽  
Andrej Cör
Keyword(s):  
Case Report ◽  
Hip Prosthesis ◽  
Full Range ◽  
Revision Operation ◽  
Term Survival ◽  
Ceramic Liner ◽  
Bearing Couple ◽  
Hip Arthroplasties

Introduction: Revisions due to the fracture of ceramic-on-ceramic (CoC) bearing are rare, however when they occur, they represent a major challenge to an orthopedic surgeon for ensuring safe and long-term survival of the replaced bearing. Case Report: We present a case of fractured ceramic liner of total hip prosthesis that underwent revision to a metal-on-polyethylene (MoP) bearing couple, with consequent huge periprosthetic metallosis. Shortly after, the second revision operation followed using the third bearing couple of ceramic-on-polyethylene (CoP). At 10 years follow-up after the operation due to ceramic fracture, the patient is now pain free with full range of motion of the revised hip. Conclusion: Establishment of diagnostic routes and recommended protocols for CoC bearing fracture would allow easier recognition of potential fracture and diminish its consequences for the patients. Keywords: Tribology, Revision Hip Arthroplasty, Ceramic Bearing Fracture.

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 Optimization of a Functionally Graded Material Stem in the Femoral Component of a Cemented Hip Arthroplasty: Influence of Dimensionality of FGM

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Abdellah Ait Moussa ◽  
Rohan Yadav
Keyword(s):  
Functionally Graded Material ◽  
Numerical Technique ◽  
Three Dimensional ◽  
Stress Shielding ◽  
Functionally Graded ◽  
Active Lifestyle ◽  
Hip Prostheses ◽  
Femur Bone ◽  
Graded Material ◽  
The Stability

The longevity of hip prostheses is contingent on the stability of the implant within the cavity of the femur bone. The cemented fixation was mostly adopted owing to offering the immediate stability from cement-stem and cement-bone bonding interfaces after implant surgery. Yet cement damage and stress shielding of the bone were proven to adversely affect the lifelong stability of the implant, especially among younger subjects who tend to have an active lifestyle. The geometry and material distribution of the implant can be optimized more efficiently with a three-dimensional realistic design of a functionally graded material (FGM). We report an efficient numerical technique for achieving this objective, for maximum performance stress shielding and the rate of early accumulation of cement damage were concurrently minimized. Results indicated less stress shielding and similar cement damage rates with a 2D-FGM implant compared to 1D-FGM and Titanium alloy implants.

Optimization of custom cementless stem using finite element analysis and elastic modulus distribution for reducing stress-shielding effect

2017 ◽  
Vol 231 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Gurunathan Saravana Kumar ◽  
Subin Philip George
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Elastic Modulus ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Implant Design ◽  
Element Analysis ◽  
Von Mises ◽  
Reducing Stress

This work proposes a methodology involving stiffness optimization for subject-specific cementless hip implant design based on finite element analysis for reducing stress-shielding effect. To assess the change in the stress–strain state of the femur and the resulting stress-shielding effect due to insertion of the implant, a finite element analysis of the resected femur with implant assembly is carried out for a clinically relevant loading condition. Selecting the von Mises stress as the criterion for discriminating regions for elastic modulus difference, a stiffness minimization method was employed by varying the elastic modulus distribution in custom implant stem. The stiffness minimization problem is formulated as material distribution problem without explicitly penalizing partial volume elements. This formulation enables designs that could be fabricated using additive manufacturing to make porous implant with varying levels of porosity. Stress-shielding effect, measured as difference between the von Mises stress in the intact and implanted femur, decreased as the elastic modulus distribution is optimized.

scholarly journals Gametic differentiation in Chlamydomonas reinhardtii. I. Production of gametes and their fine structure.

1975 ◽  
Vol 67 (3) ◽  
pp. 587-605 ◽  
Author(s):  
N C Martin ◽  
U W Goodenough
Keyword(s):  
Fine Structure ◽  
Chlamydomonas Reinhardtii ◽  
Time Course ◽  
Nitrogen Starvation ◽  
Morphological Changes ◽  
Culture Conditions ◽  
Homogeneous Material ◽  
Term Survival ◽  
Thin Sections

Gametogenesis in Chlamydomonas reinhardtii has been studied in mating-type plus cells utilizing several different culture conditions, all of which are shown to depend on the depletion of nitrogen from the medium, and the fine structure of gametes prepared under these conditions has been compared by using thin sections of fixed materials. We document alterations in ribosome levels, in chromatin morphology, in starch levels, in the organization of chloroplast membranes, and in the appearance of nuclear envelope and endoplasmic reticulum membranes during gametogenesis. We also noted the acquisition of two new organelles: a mating structure (Friedman, L., A. L. Colwin, and L. H. Colwin. 1968. j. cell Sci. 3:115-128; goodenough, U. W., and R. L. Weiss. 1975. J. Cell Biol. 67:623-637), and Golgi-derived vesicles containing a homogeneous material. We chart the time course of these morphological changes during synchronous gametogenesis. We note that many of these changes may represent adjustments to nitrogen starvation rather than direct features of gametic differentiation, and we also document that cells can differentiate so that they survive conditions of nitrogen starvation for many weeks after they become gametes. We conclude that metabolic alterations, the acquisition of mating ability, and the preparation for long-term survival are all elicited in this organism by nitrogen withdrawal, and we discuss how the various structural alterations observed in this study may relate to these three interrelated avenues of cellular differentiation.

A Finite-Element Study of Metal Backing and Tibial Resection Depth in a Composite Tibia Following Total Knee Arthroplasty

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Susumu Tokunaga ◽  
Renee D. Rogge ◽  
Scott R. Small ◽  
Michael E. Berend ◽  
Merrill A. Ritter
Keyword(s):  
Finite Element ◽  
Total Knee Arthroplasty ◽  
Knee Arthroplasty ◽  
Implant Design ◽  
Bone Resection ◽  
Element Analysis ◽  
Term Survival ◽  
Tibial Resection ◽  
Total Knee ◽  
Resection Depth

Prosthetic alignment, patient characteristics, and implant design are all factors in long-term survival of total knee arthroplasty (TKA), yet the level at which each of these factors contribute to implant loosening has not been fully described. Prior clinical and biomechanical studies have indicated tibial overload as a cause of early TKA revision. The purpose of this study was to determine the relationship between tibial component design and bone resection on tibial loading. Finite-element analysis (FEA) was performed after simulated implantation of metal backed (MB) and all-polyethylene (AP) TKA components in 5 and 15 mm of tibial resection into a validated intact tibia model. Proximal tibial strains significantly increased between 13% and 199% when implanted with AP components (p < 0.05). Strain significantly increased between 12% and 209% in the posterior tibial compartment with increased bone resection (p < 0.05). This study indicates elevated strains in AP implanted tibias across the entirety of the proximal tibial cortex, as well as a posterior shift in tibial loading in instances of increased resection depth. These results are consistent with trends observed in prior biomechanical studies and may associate the documented device history of tibial collapse in AP components with increased bone strain and overload beneath the prosthesis.

scholarly journals Fabrication and Analysis of a Ti6Al4V Implant for Cranial Restoration

2019 ◽  
Vol 9 (12) ◽  
pp. 2513 ◽  
Author(s):  
Khaja Moiduddin ◽  
Syed Hammad Mian ◽  
Usama Umer ◽  
Hisham Alkhalefah
Keyword(s):  
3D Reconstruction ◽  
Mechanical Stability ◽  
Stress Shielding ◽  
Von Mises Stress ◽  
Shielding Effect ◽  
Implant Design ◽  
Reconstruction Technique ◽  
Element Analysis ◽  
Custom Made ◽  
Cranial Implant

A custom made implant is critical in cranioplasty to cushion and restore intracranial anatomy, as well as to recover the appearance and attain cognitive stability in the patient. The utilization of customized titanium alloy implants using three-dimensional (3D) reconstruction technique and fabricated using Electron Beam Melting (EBM) has gained significant recognition in recent years, owing to their convenience and effectiveness. Besides, the conventional technique or the extant practice of transforming the standard plates is unreliable, arduous and tedious. As a result, this work aims to produce a customized cranial implant using 3D reconstruction that is reliable in terms of fitting accuracy, appearance, mechanical strength, and consistent material composition. A well-defined methodology initiating from EBM fabrication to final validation has been outlined in this work. The custom design of the implant was carried out by mirror reconstruction of the skull’s defective region, acquired through computer tomography. The design of the customized implant was then analyzed for mechanical stresses by applying finite element analysis. Consequently, the 3D model of the implant was fabricated from Ti6Al4V ELI powder with a thickness of ≃1.76–2 mm. Different tests were employed to evaluate the bio-mechanical stability and strength of the fabricated customized implant design. A 3D comparison study was performed to ensure there was anatomical accuracy, as well as to maintain gratifying aesthetics. The bio-mechanical analysis results revealed that the maximum Von Mises stress (2.5 MPa), strain distribution (1.49 × 10−4) and deformation (3.26 × 10−6 mm) were significantly low in magnitude, thus proving the implant load resistance ability. The average yield and tensile strengths for the fabricated Ti6Al4V ELI EBM specimen were found to be 825 MPa and 880 MPa, respectively, which were well over the prescribed strength for Ti6Al4V ELI implant material. The hardness study also resulted in an acceptable outcome within the acceptable range of 30–35 HRC. Certainly, the chemical composition of the fabricated EBM specimen was intact as established in EDX analysis. The weight of the cranial implant (128 grams) was also in agreement with substituted defected bone portion, ruling out any stress shielding effect. With the proposed approach, the anatomy of the cranium deformities can be retrieved effectively and efficiently. The implementation of 3D reconstruction techniques can conveniently reduce tedious alterations in the implant design and subsequent errors. It can be a valuable and reliable approach to enhance implant fitting, stability, and strength.

scholarly journals Comparison of Various Functionally Graded Femoral Prostheses by Finite Element Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-17 ◽  
Author(s):  
Azim Ataollahi Oshkour ◽  
Hossein Talebi ◽  
Seyed Farid Seyed Shirazi ◽  
Mehdi Bayat ◽  
Yat Huang Yau ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Volume Fraction ◽  
Stress Shielding ◽  
Functionally Graded ◽  
Stair Climbing ◽  
Element Analysis ◽  
Bone Interface ◽  
Cement Interface ◽  
Applied Loading

This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent.

Caspases and apoptosis

2002 ◽  
Vol 38 ◽  
pp. 9-19 ◽  
Author(s):  
Guy S Salvesen
Keyword(s):  
Cysteine Proteases ◽  
Signalling Pathways ◽  
Term Survival ◽  
Mature Adult ◽  
Intracellular Signalling Pathways ◽  
Adult Cell ◽  
Caspase Family ◽  
Cell Fragments ◽  
Pro Inflammatory Cytokines

The ability of metazoan cells to undergo programmed cell death is vital to both the precise development and long-term survival of the mature adult. Cell deaths that result from engagement of this programme end in apoptosis, the ordered dismantling of the cell that results in its 'silent' demise, in which packaged cell fragments are removed by phagocytosis. This co-ordinated demise is mediated by members of a family of cysteine proteases known as caspases, whose activation follows characteristic apoptotic stimuli, and whose substrates include many proteins, the limited cleavage of which causes the characteristic morphology of apoptosis. In vertebrates, a subset of caspases has evolved to participate in the activation of pro-inflammatory cytokines, and thus members of the caspase family participate in one of two very distinct intracellular signalling pathways.

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