Patient-specific design process and evaluation of a hip prosthesis femoral stem

2018 ◽  
Vol 42 (6) ◽  
pp. 271-290 ◽  
Author(s):  
Osama Abdelaal ◽  
Saied Darwish ◽  
Hassan El-Hofy ◽  
Yoshio Saito
Keyword(s):  
Load Transfer ◽  
Hip Prosthesis ◽  
Femoral Stem ◽  
Primary Stability ◽  
Patient Specific ◽  
Medical Implants ◽  
Element Analysis ◽  
Cross Sectional ◽  
Custom Implant ◽  
Metaphyseal Region

Introduction: There are several commercially available hip implant systems. However, for some cases, custom implant designed based on patient-specific anatomy can offer the patient the best available implant solution. Currently, there is a growing trend toward personalization of medical implants involving additive manufacturing into orthopedic medical implants’ manufacturing. Methods: This article introduces a systematic design methodology of femoral stem prosthesis based on patient’s computer tomography data. Finite element analysis is used to evaluate and compare the micromotion and stress distribution of the customized femoral component and a conventional stem. Results: The proposed customized femoral stem achieved close geometrical fit and fill between femoral canal and stem surfaces. The customized stem demonstrated lower micromotion (peak: 21 μm) than conventional stem (peak: 34 μm). Stress results indicate up to 89% increase in load transfer by conventional stem than custom stem because the higher stiffness of patient-specific femoral stem proximally increases the custom stem shielding in Gruen’s zone 7. Moreover, patient-specific femoral stem transfers the load widely in metaphyseal region. Conclusion: The customized femoral stem presented satisfactory results related to primary stability, but compromising proximo-medial load transfer due to increased stem cross-sectional area increased stem stiffness.

Comparison of Stress Distribution in Surrounding Bone during Insertion of Dental Implants on Four Implant Threads under the Effect of an Impact: A Finite Element Study

2022 ◽  
Vol 54 ◽  
pp. 89-101
Author(s):  
Noureddine Djebbar ◽  
Abdessamed Bachiri ◽  
Benali Boutabout
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Load Transfer ◽  
Three Dimensional ◽  
Primary Stability ◽  
Implant Design ◽  
Element Analysis ◽  
Three Dimensional Finite Element ◽  
The Impact ◽  
Surrounding Bone

The design of an implant thread plays a fundamental role in the osseointegration process, particularly in low-density bone. It has been postulated that design features that maximize the surface area available for contact may improve mechanical anchorage and stability in cancellous bone. The primary stability of a dental implant is determined by the mechanical engagement between the implant and bone at the time of implant insertion. The contact area of implant-bone interfaces and the concentrated stresses on the marginal bones are principal concerns of implant designers. Numerous factors influence load transfer at the bone-implant interface, for example, the type of loading, surface structure, amount of surrounding bone, material properties of the implant and implant design. The purpose of this study was to investigate the effects of the impact two different projectile of implant threads on stress distribution in the jawbone using three-dimensional finite element analysis.

Load transfer in the proximal femur and primary stability of a cemented and uncemented femoral stem: An experimental study on cadaver femurs

2017 ◽  
Vol 231 (12) ◽  
pp. 1195-1203 ◽  
Author(s):  
Cathrine H Enoksen ◽  
Tina S Wik ◽  
Jomar Klaksvik ◽  
Astvaldur J Arthursson ◽  
Otto S Husby ◽  
...  
Keyword(s):  
Proximal Femur ◽  
Load Transfer ◽  
Femoral Stem ◽  
Primary Stability ◽  
The Elderly ◽  
Stair Climbing ◽  
Physiological Strain ◽  
Fixation Methods ◽  
Cemented Stem ◽  
Total Point

There are principally two fixation methods in total hip arthroplasty, cemented and uncemented. Both methods have in general good long-time survival. Studies comparing cemented and uncemented femoral stems indicate that the cemented stems perform somewhat better, at least in the elderly population. The aim of this study was to compare load transfer and the initial micromotion pattern for an uncemented and a cemented stem. A total of 12 human cadavers were tested in a hip simulator during single leg and stair climbing. Strain was measured on the proximal femur before and after implantation of the prostheses, and the values were presented as percentage of physiological strain. The micromovements between the stem and bone were measured and a total point motion was calculated. The results showed small statistically significant differences between the fixation methods, the largest difference being 8.1 percentage points. The uncemented stem had somewhat higher micromotion than the cemented stem, but less than 10 µm. Both stems thus had acceptable primary stability. The main finding of this study is the strain and micromotion pattern of a cemented and an uncemented stem of similar geometry is overall equal. There were small statistical significant differences between the two fixation methods regarding strain and micromotion levels. The differences are considered too small to be clinically relevant.

Biomechanical Robustness of a Contemporary Cementless Stem to Surgical Variation in Stem Size and Position

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Rami M. A. Al-Dirini ◽  
Dermot O'Rourke ◽  
Daniel Huff ◽  
Saulo Martelli ◽  
Mark Taylor
Keyword(s):  
Fibrous Tissue ◽  
Femoral Stem ◽  
Primary Stability ◽  
Bone Adaptation ◽  
Stair Climbing ◽  
Patient Specific ◽  
Fe Model ◽  
Bone Implant ◽  
Stem Size ◽  
Automated Method

Successful designs of total hip replacement (THR) need to be robust to surgical variation in sizing and positioning of the femoral stem. This study presents an automated method for comprehensive evaluation of the potential impact of surgical variability in sizing and positioning on the primary stability of a contemporary cementless femoral stem (Corail®, DePuy Synthes). A patient-specific finite element (FE) model of a femur was generated from computed tomography (CT) images from a female donor. An automated algorithm was developed to span the plausible surgical envelope of implant positions constrained by the inner cortical boundary. The analysis was performed on four stem sizes: oversized, ideal (nominal) sized, and undersized by up to two stem sizes. For each size, Latin hypercube sampling was used to generate models for 100 unique alignment scenarios. For each scenario, peak hip contact and muscle forces published for stair climbing were scaled to the donor's body weight and applied to the model. The risk of implant loosening was assessed by comparing the bone–implant micromotion/strains to thresholds (150 μm and 7000 με) above which fibrous tissue is expected to prevail and the periprosthetic bone to yield, respectively. The risk of long-term loosening due to adverse bone resorption was assessed using bone adaptation theory. The range of implant positions generated effectively spanned the available intracortical space. The Corail stem was found stable and robust to changes in size and position, with the majority of the bone–implant interface undergoing micromotion and interfacial strains that are well below 150 μm and 7000 με, respectively. Nevertheless, the range of implant positions generated caused an increase of up to 50% in peak micromotion and up to 25% in interfacial strains, particularly for retroverted stems placed in a medial position.

scholarly journals Finite Element analysis of stress state in the cement of total hip prosthesis with elastomeric stress barrier

2021 ◽  
Vol 15 (57) ◽  
pp. 281-290
Author(s):  
Allaoua Fadela ◽  
Lebbal Habib ◽  
Belarbi Abderrahmane
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Concentration ◽  
Femoral Head ◽  
Load Transfer ◽  
Hip Prosthesis ◽  
Total Hip Prosthesis ◽  
Element Analysis ◽  
Acceptable Solution ◽  
Total Hip

In the total hip prosthesis, according to different positions of the patient, there are a variety of loads acting on femoral head which generate stress concentration in the cement called polymethylmethacrylat (PMMA) and consequently in the interfaces stem/cement/bone. This load transfer can provoke loosening of the implant from the femoral bone. This paper focused on optimal stress distribution in the total hip prosthesis and devoted to the development of a redesigned prosthesis type in order to minimize stress concentration in the cement. This study investigated the effect of elastomeric stress barrier incorporated between the stem and femoral head using 3D-finite element analysis. This proposed implant provoked lower load transfer in the cement due to the elastomeric effect as stress absorber.  However, the proposed model provided an acceptable solution for load transfer reduction to the cement. This investigation permitted to increase the service life of the total hip prosthesis avoiding the loosening.

scholarly journals Automated and Data-driven Computational Design of Patient-Specific Biomechanical Interfaces

2016 ◽  
Author(s):  
Kevin Mattheus Moerman ◽  
Dana Solav ◽  
David Sengeh ◽  
Hugh Herr
Keyword(s):  
Mechanical Properties ◽  
Load Transfer ◽  
Computational Design ◽  
Data Driven ◽  
Patient Specific ◽  
Element Analysis ◽  
Computational Framework ◽  
Quantitative Evidence ◽  
Non Invasive ◽  
Tissue Region

Biomechanical interfaces are mechanical structures that form the connection between a device and a tissue region, and, through appropriate load transfer, aim to minimize tissue discomfort and injury. A patient-specific and data-driven computational framework for the automated design of biomechanical interfaces is presented here. Optimization of the design of biomechanical interfaces is complex since it is affected by the interplay of the geometry and mechanical properties of both the tissue and the interface. The proposed framework is presented for the application of transtibial amputee prostheses where the interface is formed by a prosthetic liner and socket. Conventional socket design and manufacturing is largely artisan, non-standard, and insufficiently data-driven, leading to discrepancies between the quality of sockets produced by different prosthetists. Furthermore, current prosthetic liners are often not patient-specific. The proposed framework involves: A) non-invasive imaging to record patient geometry, B) indentation to assess tissue mechanical properties, C) data-driven and automated creation of patient-specific designs, D) patient-specific finite element analysis (FEA) and design evaluation, and finally E) computer aided manufacturing. Uniquely, the FEA procedure controls both the design and mechanical properties of the devices, and simulates, not only the loading during use, but also the pre-load induced by the donning of both the liner and the socket independently. Through FEA evaluation, detailed information on internal and external tissue loading, which are directly responsible for discomfort and injury, are available. Further, these provide quantitative evidence on the implications of design choices, e.g. : 1) alterations in the design can be used to locally enhance or reduce tissue loading, 2) compliant features can aid in relieving local surface pressure. The proposed methods form a patient-specific, data-driven and repeatable design framework for biomechanical interfaces, and by enabling FEA-based optimization reduces the requirement for repeated patient involvement in the currently manual and iterative design process.

An application of finite element method in material selection for dental implant crowns

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Abdullah T. Şensoy ◽  
Murat Çolak ◽  
Irfan Kaymaz ◽  
Fehim Findik
Keyword(s):  
Finite Element ◽  
Material Selection ◽  
Selection Process ◽  
Primary Stability ◽  
Patient Specific ◽  
Selection Strategy ◽  
Virtual Surgery ◽  
Element Analysis ◽  
Dental Crowns ◽  
Wide Range

Abstract Materials used for dental crowns show a wide range of variety, and a dentist’s choice can depend on several factors such as patient desires, esthetics, tooth factors, etc. One of the most important issues for implant surgery is the primary stability and it should be provided to minimize the risks of screw loosening, failed osseointegration, or nonunion. The current study aims to present the Finite Element Analysis (FEA)-based material selection strategy for a dental crown in terms of reducing the aforementioned risks of dental implants. A virtual surgery mandible model obtained using MIMICS software was transferred to the ANSYS and material candidates determined using CES software were compared using FEA. The results indicated that Zr02+Y2O3 (zirconia) has shown a 12.79% worse performance compared to Au83-88/Pt4-12/Pd4.5-6 alloy in terms of abutment loosening. On the other hand, zirconia is the most promising material for dental crowns in terms of the stability of the bone-implant complex. Therefore, it may show the best overall performance for clinical use. Moreover, as suggested in this study, a better outcome and more accurate predictions can be achieved using a patient-specific FEA approach for the material selection process.

Evaluation of Cement Stresses in Finite Element Analyses of Cemented Orthopaedic Implants

2001 ◽  
Vol 123 (6) ◽  
pp. 623-628 ◽  
Author(s):  
A. B. Lennon ◽  
P. J. Prendergast
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Load Transfer ◽  
Hip Prosthesis ◽  
Peak Stress ◽  
Longitudinal Direction ◽  
Orthopaedic Implants ◽  
Element Analysis ◽  
Stressed Volume ◽  
Tensile Stresses

Stress analysis of the cement fixation of orthopaedic implants to bone is frequently carried out using finite element analysis. However, the stress distribution in the cement layer is usually intricate, and it is difficult to report it in a way that facilitates comparison of implants for pre-clinical testing. To study this problem, and make recommendations for stress reporting, a finite element analysis of a hip prosthesis implanted into a synthetic composite femur is developed. Three cases are analyzed: a fully bonded implant, a debonded implant, and a debonded implant where the cement is removed distal to the stem tip. In addition to peak stresses, and contour and vector plots, a stressed volume and probability-of-failure analysis is reported. It is predicted that the peak stress is highest for the debonded stem, and that removal of the distal cement more than halves this peak stress. This would suggest that omission of the distal cement is good for polished prostheses (as practiced for the Exeter design). However, if the percentage of cement stressed above a certain threshold (say 3 MPa) is considered, then the removal of distal cement is shown to be disadvantageous because a higher volume of cement is stressed to above the threshold. Vector plots clearly demonstrate the different load transfer for bonded and debonded prostheses: A bonded stem generates maximum tensile stresses in the longitudinal direction, whereas a debonded stem generates most tensile stresses in the hoop direction, except near the tip where tensile longitudinal stresses occur due to subsidence of the stem. Removal of the cement distal to the tip allows greater subsidence but alleviates these large stresses at the tip, albeit at the expense of increased hoop stresses throughout the mantle. It is concluded that a thorough analysis of cemented implants should not report peak stress, which can be misleading, but rather stressed volume, and that vector plots should be reported if a precise analysis of the load transfer mechanism is required.

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