Design of a Free-Floating Polycarbonate-Urethane Meniscal Implant Using Finite Element Modeling and Experimental Validation

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Jonathan J. Elsner ◽  
Sigal Portnoy ◽  
Gal Zur ◽  
Farshid Guilak ◽  
Avi Shterling ◽  
...  
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Implant Design ◽  
Polycarbonate Urethane ◽  
Joint Loads ◽  
Contact Pressures ◽  
Circumferential Reinforcement ◽  
Cadaveric Knee

The development of a synthetic meniscal implant that does not require surgical attachment but still provides the biomechanical function necessary for joint preservation would have important advantages. We present a computational-experimental approach for the design optimization of a free-floating polycarbonate-urethane (PCU) meniscal implant. Validated 3D finite element (FE) models of the knee and PCU-based implant were analyzed under physiological loads. The model was validated by comparing calculated pressures, determined from FE analysis to tibial plateau contact pressures measured in a cadaveric knee in vitro. Several models of the implant, some including embedded reinforcement fibers, were tested. An optimal implant configuration was then selected based on the ability to restore pressure distribution in the knee, manufacturability, and long-term safety. The optimal implant design entailed a PCU meniscus embedded with circumferential reinforcement made of polyethylene fibers. This selected design can be manufactured in various sizes, without risking its integrity under joint loads. Importantly, it produces an optimal pressure distribution, similar in shape and values to that of natural meniscus. We have shown that a fiber-reinforced, free-floating PCU meniscal implant can redistribute joint loads in a similar pattern to natural meniscus, without risking the integrity of the implant materials.

Design Optimization of a Polycarbonate-Urethane Meniscal Implant in the Sheep Knee: In-Vitro Study

2010 ◽  
Author(s):  
Jonathan J. Elsner ◽  
Gal Zur ◽  
Farshid Guilak ◽  
Eran Linder-Ganz ◽  
Avi Shterling
Keyword(s):  
Pressure Distribution ◽  
Design Optimization ◽  
Disease Transmission ◽  
Unsolved Problem ◽  
In Vitro Study ◽  
Uneven Distribution ◽  
Polycarbonate Urethane ◽  
Meniscal Replacement ◽  
Contact Pressures

Meniscus replacement still represents an unsolved problem in orthopedics. Allograft meniscus implantation has been suggested as a means to restore contact pressures following meniscectomy. However, issues such as graft availability, disease transmission, and size matching still limit the use of allograft menisci. Furthermore, the complexities of meniscal repairs may contribute to uneven distribution of load, instability and initiation of degenerative damage. A synthetic meniscal substitute could have significant advantages for meniscal replacement, as it could be available at the time of surgery in a substantial number of sizes and shapes to accommodate most patients. There is, however, a need to establish an optimal configuration of such an implant that would result in pressure distribution ability closest to that of the natural meniscus.

Integrity Assessment of a Free-Fall Lifeboat Launched From a FPSO

2015 ◽  
Author(s):  
Guomin Ji ◽  
Nabila Berchiche ◽  
Sébastien Fouques ◽  
Thomas Sauder ◽  
Svein-Arne Reinholdtsen
Keyword(s):  
Finite Element ◽  
Pressure Distribution ◽  
Structural Integrity ◽  
Dynamic Effect ◽  
Sensitivity Study ◽  
Computational Time ◽  
Load Factor ◽  
Time Varying ◽  
Integrity Assessment

The paper addresses the structural integrity assessment of lifeboat launched from floating production, storage and offloading (FPSO) vessels. The study is based on long-term drop lifeboat simulations accounting for more than 50 years of hindcast data of metocean conditions and corresponding FPSO motions. Selection of the load cases and strength analyses with high computational time is a challenge. The load cases analyzed are those corresponding to the 99th percentile of long term distribution of indicators for large slamming loads (CARXZ) or large submergence (Imaxsub). For six selected cases, the time-varying pressure distribution on the lifeboat hull during and after water impact is calculated by CFD simulations using StarCCM+. The finite element model (FEM) of the composite structure of the lifeboat is modelled by ABAQUS. Quasi-static finite element (FE) analyses are performed for the selected load cases. The structural integrity is assessed by the maximum stress and Tsai-Wu failure measure. In the present study, the load and resistance factors are combined and applied to the response. A sensitivity study is performed to investigate the non-linear load/response effects when the load factor is applied to the load. In addition, dynamic analysis is performed with the time-varying pressure distribution for selected case and the dynamic effect is investigated.

Determining the Fatigue Life of Dental Implants

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
Horea T. Ilieş ◽  
Dennis Flanagan ◽  
Paul T. McCullough ◽  
Scott McQuoid
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Dental Implants ◽  
Morphological Characteristics ◽  
Design Tool ◽  
Implant Design ◽  
Physical Measurements ◽  
Local Bone ◽  
Removable Dental Prostheses

Dental implants are used to retain and support fixed and removable dental prostheses. In many clinical situations, local bone morphology requires dental implants that have a diameter that is significantly smaller than the typical implant diameters. In these cases, the fatigue life of the smaller diameter implants becomes a critical therapeutic parameter. However, this fatigue life depends on the implant itself, on the physical properties of the bone, as well as on other morphological characteristics that are patient dependent. In other words, this fatigue life varies greatly with each newly placed implant, but the capability to predict the fatigue life of dental implants does not exist today. In this paper, we present the first steps towards establishing such a methodology. We develop a finite element based fatigue model for rigidly mounted dental implants, and correlate its results with both analytical predictions as well as physical measurements. This implies that such a model can be used as a valid predictor of fatigue life of dental implants themselves, and can be used as a valuable implant design tool. Furthermore, we present the design of a cost effective device to measure the fatigue life of dental implants that can be either rigidly or bone mounted (in vitro). This device was used to measure the fatigue life of an initial sample of nine dental implants, and we show that the results predicted by the finite element model correlated well with our initial experimental results.

Finite Element and Experimental Cortex Strains of the Intact and Implanted Tibia

2007 ◽  
Vol 129 (5) ◽  
pp. 791-797 ◽  
Author(s):  
A. Completo ◽  
F. Fonseca ◽  
J. A. Simões
Keyword(s):  
Finite Element ◽  
Preclinical Testing ◽  
Gauge Models ◽  
Vast Literature ◽  
Strain Data ◽  
Bone Strains ◽  
Experimental Strain ◽  
Failure Scenario

Finite Element (FE) models for the simulation of intact and implanted bone find their main purpose in accurately reproducing the associated mechanical behavior. FE models can be used for preclinical testing of joint replacement implants, where some biomechanical aspects are difficult, if not possible, to simulate and investigate in vitro. To predict mechanical failure or damage, the models should accurately predict stresses and strains. Commercially available synthetic femur models have been extensively used to validate finite element models, but despite the vast literature available on the characteristics of synthetic tibia, numerical and experimental validation of the intact and implant assemblies of tibia are very limited or lacking. In the current study, four FE models of synthetic tibia, intact and reconstructed, were compared against experimental bone strain data, and an overall agreement within 10% between experimental and FE strains was obtained. Finite element and experimental (strain gauge) models of intact and implanted synthetic tibia were validated based on the comparison of cortex bone strains. The study also includes the analysis carried out on standard tibial components with cemented and noncemented stems of the P.F.C Sigma Modular Knee System. The overall agreement within 10% previously established was achieved, indicating that FE models could be successfully validated. The obtained results include a statistical analysis where the root-mean-square-error values were always <10%. FE models can successfully reproduce bone strains under most relevant acting loads upon the condylar surface of the tibia. Moreover, FE models, once properly validated, can be used for preclinical testing of tibial knee replacement, including misalignment of the implants in the proximal tibia after surgery, simulation of long-term failure according to the damage accumulation failure scenario, and other related biomechanical aspects.

Design of a Polycarbonate-Urethane Meniscal Implant: Finite Element Approach

2009 ◽  
Author(s):  
Eran Linder-Ganz ◽  
Jonathan J. Elsner ◽  
Amir Danino ◽  
Gal Zur ◽  
Farshid Guilak ◽  
...  
Keyword(s):  
Finite Element ◽  
Knee Injury ◽  
Tibial Plateau ◽  
Medial Meniscus ◽  
Implant Design ◽  
Degenerative Arthritis ◽  
Polycarbonate Urethane ◽  
Reduction Of Pain ◽  
Element Approach ◽  
Knee Load

The medial meniscus plays an important role in the knee joint [1]. Meniscus dysfunction due to tear is a common knee injury which leads to degenerative arthritis, attributed primarily to the changes in knee load distribution [2]. Clearly, there is a substantial need to protect the articular cartilage by either repairing or replacing the menisci. A “floating” Polycarbonate-Urethane (PCU) meniscal implant (Fig. 1a) is proposed as a solution for restoring the function of the missing meniscus and for the reduction of pain, through improved tibial and femoral pressure distribution. The implant is composed of PCU embedded with polyethylene reinforcement fibers (“Dyneema®”, DSM), and its design is based on the geometry of the articulating surfaces of the femur and tibia. Our goal was to develop an optimal meniscal implant design (in terms of composition and geometry), whose contact pressure with the tibial plateau (TP) would be similar to that of the natural meniscus and be able resist mechanical failure of any of its components. We hereby present one aspect of the implant bench-tests, finite element (FE) analyses of the implant in the medial knee under physiological relevant loading conditions.

Effect of Polylactic Acid/Hydroxyapatite Coating on Dental Implant Using Finite Element Method

2020 ◽  
Vol 995 ◽  
pp. 103-108
Author(s):  
Hassan Mas Ayu ◽  
M.M. Mustaqieem ◽  
Rosdi Daud ◽  
A. Shah ◽  
Andril Arafat ◽  
...  
Keyword(s):  
Finite Element ◽  
Stress Distribution ◽  
Dental Implant ◽  
Bonding Strength ◽  
Load Condition ◽  
Implant Design ◽  
Element Analysis ◽  
Improve Design

Finite element analysis (FEA) has been proven to be a precise and applicable method for evaluating dental implant systems. This is because FEA allows for measurement of the stress distribution inside of the bone and various dental implant designs via simulation analysis during mastication where such measurements are impossible to perform in-vitro or in-vivo experiment. That is why the relationship between implant design and load distribution at the implant bone interface is a crucial issue to understand. This research study focuses on a static simulation and bonding strength for PLA/HA coating on V thread design of dental implant using three-dimensional finite element. The average masticatory muscle that involves in human biting such as X, Y and Z direction will be used to simulate force with load condition of 17.1N, 114.6N and 23.4N respectively. Based on result obtained, the coated dental implant model is more compatible than uncoated model due to lower maximum stress which is reduce about 16%. The coated model also shows lower deformation and higher bonding strength. Outcomes from this research provide a better understanding of stress distribution characteristics that would be useful in order to improve design of dental implant thread and evaluation of the PLA/HA bonding strength applied.

The Effect of Varying the Density-Modulus Relationship Used to Apply Material Properties in a Finite Element Model of the Distal Ulna

2008 ◽  
Author(s):  
Rebecca L. Austman ◽  
Jaques S. Milner ◽  
David W. Holdsworth ◽  
Cynthia A. Dunning
Keyword(s):  
Computed Tomography ◽  
Finite Element ◽  
Material Properties ◽  
Cost Effective ◽  
Element Model ◽  
Implant Design ◽  
Timely Manner ◽  
Distal Ulna ◽  
Subject Specific

In many areas of orthopaedic biomechanics, such as implant design, properly developed Finite Element (FE) models can be a great companion to in-vitro studies, as they may allow a wider range of experimental variables to be explored in a cost-effective and timely manner. One challenge in developing these models is the assignment of accurate material properties to bone. Through the use of computed tomography (CT), many recent studies have developed subject-specific FE models, where material properties of bone are assigned based on density information derived from the scans. This involves the use of an equation to relate density and elastic modulus. There are several such relationships from which to choose in the literature. Most FE studies tend to use one of these multiple equations without justification or investigation into its appropriateness for the model.

Contact mechanics of the ovine stifle during simulated early stance in gait

2007 ◽  
Vol 20 (01) ◽  
pp. 70-72 ◽  
Author(s):  
N. K. Lee-Shee ◽  
M. B. Hurtig ◽  
J. P. Dickey
Keyword(s):  
Stance Phase ◽  
Unique Contribution ◽  
Worst Case ◽  
Stifle Joint ◽  
Mean Pressure ◽  
Joint Contact ◽  
Six Degree Of Freedom ◽  
Joint Loads ◽  
Contact Pressures

SummaryOvine stifle joint contact pressures and contact areas were measured in vitro using a six degree-of-freedom (DOF) robotic system. The robot generated static joint loads of 1.875 times body weight (BW) compression, 0.15 BW medial shear and 0.625 BW cranial shear at 6.5o of flexion for four specimens, simulating the early stance phase of gait (walking). This condition represents a period of intense loading and was implemented as a worst-case loading scenario for the joint at this gait. We determined that the medial and lateral compartments bore 5.5 ± 0.9 MPa and 4.4 ± 1.1 MPa of mean pressure, respectively, on 107.7 ± 28.7 mm2 and 60.8 ± 56.3 mm2 of area, respectively. The unique contribution of this study is that stifle contact pressures and areas were determined during loading which simulated physiological levels (early stance phase of gait). This information is important to our understanding of the stresses that must be borne by repair tissues/constructs that are implanted into human and animal tibio-femoral joints.

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