Finite element analysis of porously punched prosthetic short stem virtually designed for simulative uncemented hip arthroplasty

Background: There is no universal hip implant suitably fills all femoral types, whether prostheses of porous short-stem suitable for Hip Arthroplasty is to be measured scientifically. Methods: Ten specimens of femurs scanned by CT were input onto Mimics to rebuild 3D models; their *stl format dataset were imported into Geomagic-Studio for simulative osteotomy; the generated *.igs dataset were interacted by UG to fit solid models; the prosthesis were obtained by the same way from patients, and bored by punching bears designed by Pro-E virtually; cements between femora and prosthesis were extracted by deleting prosthesis; in HyperMesh, all compartments were assembled onto four artificial joint style as: (a) cemented long-stem prosthesis; (b) porous long-stem prosthesis; (c) cemented short-stem prosthesis; (d) porous short-stem prosthesis. Then, these numerical models of Finite Element Analysis were exported to AnSys for numerical solution. Results: Observed whatever from femur or prosthesis or combinational femora-prostheses, “Kruskal-Wallis” value p > 0.05 demonstrates that displacement of (d) ≈ (a) ≈ (b) ≈ (c) shows nothing different significantly by comparison with 600 N load. If stresses are tested upon prosthesis, (d) ≈ (a) ≈ (b) ≈ (c) is also displayed; if upon femora, (d) ≈ (a) ≈ (b) < (c) is suggested; if upon integral joint, (d) ≈ (a) < (b) < (c) is presented. Conclusions: Mechanically, these four sorts of artificial joint replacement are stabilized in quantity. Cemented short-stem prostheses present the biggest stress, while porous short-stem & cemented long-stem designs are equivalently better than porous long-stem prostheses and alternatives for femoral-head replacement. The preferred design of those two depends on clinical conditions. The cemented long-stem is favorable for inactive elders with osteoporosis, and porously punched cementless short-stem design is suitable for patients with osteoporosis, while the porously punched cementless short-stem is favorable for those with a cement allergy. Clinically, the strength of this study is to enable preoperative strategy to provide acute correction and decrease procedure time

Finite element analysis of polyethylene wear in total hip replacement: A literature review

Evaluation and prediction of wear play a key role in product design and material selection of total hip replacements, because wear debris is one of the main causes of loosening and failure. Multifactorial clinical or laboratory studies are high cost and require unfeasible timeframes for implant development. Simulation using finite element methods is an efficient and inexpensive alternative to predict wear and pre-screen various parameters. This article presents a comprehensive literature review of the state-of-the-art finite element modelling techniques that have been applied to evaluate wear in polyethylene hip replacement components. A number of knowledge gaps are identified including the need to develop appropriate wear coefficients and the analysis of daily living activities

Specimen-Specific Natural, Pathological, and Implanted Knee Mechanics Using Finite Element Modeling

There is an increasing incidence of knee pain and injury among the population, and increasing demand for higher knee function in total knee replacement designs. As a result, clinicians and implant manufacturers are interested in improving patient outcomes, and evaluation of knee mechanics is essential for better diagnosis and repair of knee pathologies. Common knee pathologies include osteoarthritis (degradation of the articulating surfaces), patellofemoral pain, and cruciate ligament injury and/or rupture. The complex behavior of knee motion presents unique challenges in the diagnosis of knee pathology and restoration of healthy knee function. Quantifying knee mechanics is essential for developing successful rehabilitation therapies and surgical treatments. Researchers have used in-vitro and in-vivo experiments to quantify joint kinematics and loading, but experiments can be costly and time-intensive, and contact and ligament mechanics can be difficult to measure directly. Computational modeling can complement experimental studies by providing cost-effective solutions for quantifying joint and soft tissue forces. Musculoskeletal models have been used to measure whole-body motion, and predict joint and muscle forces, but these models can lack detail and accuracy at the joint-level. Finite element modeling provides accurate solutions of the internal stress/strain behavior of bone and soft tissue using subject-specific geometry and complex contact and material representations. While previous FE modeling has been used to simulate injury and repair, models are commonly based on literature description or average knee behavior. The research presented in this dissertation focused on developing subject-specific representations of the TF and PF joints including calibration and validation to experimental data for healthy, pathological, and implanted knee conditions. A combination of in-vitro experiment and modeling was used to compare healthy and cruciate-deficient joint mechanics, and develop subject-specific computational representations. Insight from in-vitro testing supported in-vivo simulations of healthy and implanted subjects, in which PF mechanics were compared between two common patellar component designs and the impact of cruciate ligament variability on joint kinematics and loads was assessed. The suite of computational models developed in this dissertation can be used to investigate knee pathologies to better inform clinicians on the mechanisms surrounding injury, support the diagnosis of at-risk patients, explore rehabilitation and surgical techniques for repair, and support decision-making for new innovative implant designs

Computational Modeling of Nonlinear Behavior in Orthopaedics

Total knee replacement (TKR) is one of the most common orthopaedic procedures performed in the USA and is projected to exceed 4.3 million by 2030. Although TKR surgery has a success rate of 95% at 10 years for most TKR designs, revision surgery still occurs approximately once for every ten primary TKR surgeries. Failure modes in TKR involve the interplay between implant mechanical performance and surrounding biological tissues. The orthopaedic community has turned to computational modeling as an effective tool to analyze these complex interactions and improve patient outcomes. The objective of these studies was to utilize a combined computational and experimental approach to investigate modes of TKR failure where material nonlinearity plays a significant role in the biomechanics under investigation. A finite element (FE) model of a modular TKR taper junction was developed in order to investigate the stress environment in relation to corrosive behavior under in vivo loading conditions. Linear elastic and elastoplastic material models were defined and angular mismatch parametrically varied in order to determine the sensitivity of model predicted stresses to material model selection and taper junction geometry. It was determined that positive angle mismatches cause plastic deformation and overestimated stresses in linear elastic analyses compared to elastoplastic analyses. Calculated stresses were also strongly correlated with angle mismatch when varied ±0.25o. Model stress distributions agreed with corrosion patterns evident on retrieved modular TKR components and magnitudes corresponding with corrosive behavior in vitro. Additionally, a series of passive FE TKR models were developed in order to investigate the intrinsic relationship between TKR component alignment, ligament tensions, and knee kinematics during intraoperative assessments. A kinematically-driven model was developed and validated with an open source dataset, and was able to discriminate clinical outcomes based on calculated ligament tensions when input in vivo kinematics. Patient-specific simulations found greater tension in lateral ligaments for poor outcome patients compared to good outcome patients, and statistically significant differences in tensions for the POL, PFL, DMCL, and ALS ligaments during mid-flexion. A force-driven model was also developed and validated with in vitro cadaver testing, and found that variation in tibial component alignment of ±15o influence intraoperative ligament tensions. However, definitive trends between TKR component alignment and ligament tension were not discerned. Nonetheless, both modeling approaches were found to be sensitive to subclinical abnormalities. These findings suggest mechanical stress is a key contributor to taper junction corrosion and that ligament tensions are the mechanism leading to abnormal function in the passive TKR knee. These studies contributed innovative computational models that provide a foundation to advance the understanding of these complex relationships, and modeling frameworks that exemplify sound verification and validation practices

Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 658-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligamenttuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between FE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning

Constrained Statistical Modelling of Knee Flexion from Multi-Pose Magnetic Resonance Imaging

© 1982-2012 IEEE.Reconstruction of the anterior cruciate ligament (ACL) through arthroscopy is one of the most common procedures in orthopaedics. It requires accurate alignment and drilling of the tibial and femoral tunnels through which the ligament graft is attached. Although commercial computer-Assisted navigation systems exist to guide the placement of these tunnels, most of them are limited to a fixed pose without due consideration of dynamic factors involved in different knee flexion angles. This paper presents a new model for intraoperative guidance of arthroscopic ACL reconstruction with reduced error particularly in the ligament attachment area. The method uses 3D preoperative data at different flexion angles to build a subject-specific statistical model of knee pose. To circumvent the problem of limited training samples and ensure physically meaningful pose instantiation, homogeneous transformations between different poses and local-deformation finite element modelling are used to enlarge the training set. Subsequently, an anatomical geodesic flexion analysis is performed to extract the subject-specific flexion characteristics. The advantages of the method were also tested by detailed comparison to standard Principal Component Analysis (PCA), nonlinear PCA without training set enlargement, and other state-of-The-Art articulated joint modelling methods. The method yielded sub-millimetre accuracy, demonstrating its potential clinical value

Biomechanical Analysis of Knee Implant with and Without Bone Attachment Using Finite Element Method

Degenerative arthritis is a disease that affects the line cartilage of the knee joint.It produces various injuries in the knee joint and may need a total knee replacement surgery of the affected knee with artificial components. Geometric complexity and non-linearity of the biomaterials of the knee make the logical solutions of the mechanical conduct of the knee joint difficult. In this study,3D modeling software,SolidWorks is used for modeling of knee implant and finite element method software ANSYS 15.0 is used for numerical estimation of equivalent stress, equivalent strain and total deformation.This study explains a human knee implant model using ANSYS 15.0 which shows multiple contact pairs working together.The objective is to find out the FEM results considering various loading state of knee implant with and without bone for various biomaterials,different meshing state of knee implant without bone for various steps. Also,this study compares these results and suggests the best biomaterial,mesh quality and time step for knee implant analysis for total knee replacement cases.A knee implant without bone static structure was able to sustain a load of 1500 N for material properties of ZrO2 demonstrating a stable stress value of 736.52 MPa.However,a knee implant without bone transient structure could sustain a time step of 0.001 sec at a medium mesh demonstrating a stable stress value of 455 MPa. It is seen that a knee implant with bone static structure was able to maintain a load of 700 N for material properties of Ti6Al6V showing a stable stress value of 1036 MPa.This implant model is a geometric contact path-dependent model that includes friction between bodies, which helps in understanding it's structural,and transient mechanical behavior,thus suggesting its practical use in the field of implant replacement/ prosthesis

Recent trends, technical concepts and components of computer-assisted orthopedic surgery systems: A comprehensive review

Computer-assisted orthopedic surgery (CAOS) systems have become one of the most important and challenging types of system in clinical orthopedics, as they enable precise treatment of musculoskeletal diseases, employing modern clinical navigation systems and surgical tools. This paper brings a comprehensive review of recent trends and possibilities of CAOS systems. There are three types of the surgical planning systems, including: systems based on the volumetric images (computer tomography (CT), magnetic resonance imaging (MRI) or ultrasound images), further systems utilize either 2D or 3D fluoroscopic images, and the last one utilizes the kinetic information about the joints and morphological information about the target bones. This complex review is focused on three fundamental aspects of CAOS systems: their essential components, types of CAOS systems, and mechanical tools used in CAOS systems. In this review, we also outline the possibilities for using ultrasound computer-assisted orthopedic surgery (UCAOS) systems as an alternative to conventionally used CAOS systems.Web of Science1923art. no. 519