Experimental Validation of a Finite Element Model of a Human Cadaveric Tibia

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Hans A. Gray ◽  
Fulvia Taddei ◽  
Amy B. Zavatsky ◽  
Luca Cristofolini ◽  
Harinderjit S Gill
Keyword(s):  
Finite Element ◽  
Knee Replacement ◽  
Experimental Validation ◽  
Regression Line ◽  
Ct Scans ◽  
Fe Model ◽  
Loading Conditions ◽  
Test Conditions ◽  
Physical Testing ◽  
Mean Square Errors

Finite element (FE) models of long bones are widely used to analyze implant designs. Experimental validation has been used to examine the accuracy of FE models of cadaveric femurs; however, although convergence tests have been carried out, no FE models of an intact and implanted human cadaveric tibia have been validated using a range of experimental loading conditions. The aim of the current study was to create FE models of a human cadaveric tibia, both intact and implanted with a unicompartmental knee replacement, and to validate the models against results obtained from a comprehensive set of experiments. Seventeen strain rosettes were attached to a human cadaveric tibia. Surface strains and displacements were measured under 17 loading conditions, which consisted of axial, torsional, and bending loads. The tibia was tested both before and after implantation of the knee replacement. FE models were created based on computed tomography (CT) scans of the cadaveric tibia. The models consisted of ten-node tetrahedral elements and used 600 material properties derived from the CT scans. The experiments were simulated on the models and the results compared to experimental results. Experimental strain measurements were highly repeatable and the measured stiffnesses compared well to published results. For the intact tibia under axial loading, the regression line through a plot of strains predicted by the FE model versus experimentally measured strains had a slope of 1.15, an intercept of 5.5 microstrain, and an R2 value of 0.98. For the implanted tibia, the comparable regression line had a slope of 1.25, an intercept of 12.3 microstrain, and an R2 value of 0.97. The root mean square errors were 6.0% and 8.8% for the intact and implanted models under axial loads, respectively. The model produced by the current study provides a tool for simulating mechanical test conditions on a human tibia. This has considerable value in reducing the costs of physical testing by pre-selecting the most appropriate test conditions or most favorable prosthetic designs for final mechanical testing. It can also be used to gain insight into the results of physical testing, by allowing the prediction of those variables difficult or impossible to measure directly.

Development and Verification of a Dynamic TKR Model

2002 ◽  
Author(s):  
Jason P. Halloran ◽  
Anthony J. Petrella ◽  
Paul J. Rullkoetter
Keyword(s):  
Finite Element ◽  
Contact Mechanics ◽  
Dynamic Loading ◽  
Soft Tissues ◽  
Dynamic Models ◽  
Total Joint Replacement ◽  
Fe Model ◽  
Loading Conditions ◽  
Dynamic Loading Conditions

The success of current total knee replacement (TKR) devices is contingent on the kinematics and contact mechanics during in vivo activity. Indicators of potential clinical performance of total joint replacement devices include contact stress and area due to articulations, and tibio-femoral and patello-femoral kinematics. An effective way of evaluating these parameters during the design phase or before clinical use is via computationally efficient computer models. Previous finite element (FE) knee models have generally been used to determine contact stresses and/or areas during static or quasi-static loading conditions. The majority of knee models intended to predict relative kinematics have not been able to determine contact mechanics simultaneously. Recently, however, explicit dynamic finite element methods have been used to develop dynamic models of TKR able to efficiently determine joint and contact mechanics during dynamic loading conditions [1,2]. The objective of this research was to develop and validate an explicit FE model of a TKR which includes tibio-femoral and patello-femoral articulations and surrounding soft tissues. The six degree-of-freedom kinematics, kinetics and polyethylene contact mechanics during dynamic loading conditions were then predicted during gait simulation.

Dynamic Finite Element Analysis of Drum-Type Shipping Packages for Radioactive Materials

2012 ◽  
Author(s):  
Zenghu Han ◽  
Vikram N. Shah ◽  
Yung Y. Liu
Keyword(s):  
Finite Element ◽  
Structural Performance ◽  
Type B ◽  
Regulatory Requirements ◽  
Radioactive Materials ◽  
Structural Evaluation ◽  
Test Conditions ◽  
Physical Testing ◽  
Lower Temperature ◽  
The Impact

The US Department of Energy (DOE) often uses Type AF and Type B drum-type packages for shipment of radioactive materials (RAM), both of which shall be designed and certified to meet the regulatory requirements specified in 10 CFR 71, to ensure safety, public health and protection of environment. In particular for the hypothetical accident conditions (HAC) prescribed in 10 CFR 71.73, RAM packages are subjected to sequential tests of 30-ft drop, crush, puncture, engulfing fire, and water immersions. Packages shall maintain structural integrity of containment, radiation shielding, and criticality control following these HAC tests. The structural evaluation (i.e., drop, crush, and puncture) of packages should address different combinations of test conditions, such as drop orientations, sequence, temperature and payload during the drop, crush and puncture tests. The combinations to be considered are those which would produce most damage to the package, challenge the most vulnerable packaging components, and cause the most cumulative damages. The evaluation of the most damage should also consider the effects of fire and water immersions following the structural tests. In this paper, the structural evaluation details of two drum-type packages, Model 9979 Type AF and Model ES-3100 Type B(U)F, are discussed. The design and performance of these packages were evaluated by physical testing of full-size prototype units. However, it is not practical to account for the worst test conditions and sequence in physical testing. Therefore, confirmatory finite element analyses have been performed to determine whether the cumulative damage resulting from the worst test sequence and conditions is acceptable. It was found for the 9979 package, the corner drop followed by corner crush causes most damage, and most unfavorably challenges its split-ring closures; for the ES-3100 package, the containment vessel (CV) experiences maximum strain following the sequence of bottom-to-lid slapdown and side crush. Although a lower temperature does not compromise their structural performance, the ES-3100 CV does experience slightly more strain because the impact limiter imparts more impact load because of its higher stiffness at lower temperature. In summary, the confirmatory analysis results show that the structural performance of the packages meets the regulatory requirements.

scholarly journals Finite Element Model of the Knee for Investigation of Injury Mechanisms: Development and Validation

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Ali Kiapour ◽  
Ata M. Kiapour ◽  
Vikas Kaul ◽  
Carmen E. Quatman ◽  
Samuel C. Wordeman ◽  
...  
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Knee Joint ◽  
Center Of Pressure ◽  
Fe Model ◽  
Loading Conditions ◽  
Tibiofemoral Rotation ◽  
Injury Mechanisms ◽  
Model Predictions ◽  
Tibiofemoral Kinematics

Multiple computational models have been developed to study knee biomechanics. However, the majority of these models are mainly validated against a limited range of loading conditions and/or do not include sufficient details of the critical anatomical structures within the joint. Due to the multifactorial dynamic nature of knee injuries, anatomic finite element (FE) models validated against multiple factors under a broad range of loading conditions are necessary. This study presents a validated FE model of the lower extremity with an anatomically accurate representation of the knee joint. The model was validated against tibiofemoral kinematics, ligaments strain/force, and articular cartilage pressure data measured directly from static, quasi-static, and dynamic cadaveric experiments. Strong correlations were observed between model predictions and experimental data (r > 0.8 and p < 0.0005 for all comparisons). FE predictions showed low deviations (root-mean-square (RMS) error) from average experimental data under all modes of static and quasi-static loading, falling within 2.5 deg of tibiofemoral rotation, 1% of anterior cruciate ligament (ACL) and medial collateral ligament (MCL) strains, 17 N of ACL load, and 1 mm of tibiofemoral center of pressure. Similarly, the FE model was able to accurately predict tibiofemoral kinematics and ACL and MCL strains during simulated bipedal landings (dynamic loading). In addition to minimal deviation from direct cadaveric measurements, all model predictions fell within 95% confidence intervals of the average experimental data. Agreement between model predictions and experimental data demonstrates the ability of the developed model to predict the kinematics of the human knee joint as well as the complex, nonuniform stress and strain fields that occur in biological soft tissue. Such a model will facilitate the in-depth understanding of a multitude of potential knee injury mechanisms with special emphasis on ACL injury.

Improving Child Safety Seat Performance Through Finite Element Simulations

2014 ◽  
Author(s):  
Jingwen Hu ◽  
H. R. Raj Jayakar
Keyword(s):  
Finite Element ◽  
Safety Performance ◽  
Fe Model ◽  
Future Studies ◽  
Design Concepts ◽  
Test Conditions ◽  
Fe Simulations ◽  
Tube Shape ◽  
Frontal Crashes ◽  
Safety Seat

In this study, a finite element (FE) model of a child seat was developed. This model along with a HIII 6-year-old child ATD model was validated against four sled tests with different restraint conditions under FMVSS 213 test environments. The simulated results of ATD kinematics and restraint forces correlated well to the test data. In order to reduce the weight of the child seat while keeping its safety performance, different design concepts were explored by FE simulations with a mesh morphing method. It was found that lowering the height of child seat base can effectively reduce the weight and head/knee excursions in frontal crashes at the same time. Reducing the material in low stress areas would reduce the weight but slightly increase the ATD head and knee excursions in crashes. Overall, the modified design with reduced based height and reduced weight in low stress areas has a weight of 1.13 lbs less than the original seat, and the ATD head and knee excursions in FMVSS 213 test conditions with four different restraint conditions all reduced. In addition, it was found that changing the tube shape can potentially change the distribution of the head and knee excursions without much impact on weight. This study demonstrated the feasibility and usefulness for introducing FE simulations into the child seat design process. Future studies using this validated FE child seat model should focus on other crash scenarios, such as those with different impact severities and directions to improve safety performance of the child seat design.

An Integrated Musculoskeletal-Finite-Element Model to Evaluate Effects of Load Carriage on the Tibia During Walking

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Chun Xu ◽  
Amy Silder ◽  
Ju Zhang ◽  
Julie Hughes ◽  
Ginu Unnikrishnan ◽  
...  
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Injury Risk ◽  
Load Carriage ◽  
Body Motion ◽  
Bone Biomechanics ◽  
External Loading ◽  
Fe Model ◽  
Loading Conditions ◽  
Reaction Forces

Prior studies have assessed the effects of load carriage on the tibia. Here, we expand on these studies and investigate the effects of load carriage on joint reaction forces (JRFs) and the resulting spatiotemporal stress/strain distributions in the tibia. Using full-body motion and ground reaction forces from a female subject, we computed joint and muscle forces during walking for four load carriage conditions. We applied these forces as physiological loading conditions in a finite-element (FE) analysis to compute strain and stress. We derived material properties from computed tomography (CT) images of a sex-, age-, and body mass index-matched subject using a mesh morphing and mapping algorithm, and used them within the FE model. Compared to walking with no load, the knee JRFs were the most sensitive to load carriage, increasing by as much as 26.2% when carrying a 30% of body weight (BW) load (ankle: 16.4% and hip: 19.0%). Moreover, our model revealed disproportionate increases in internal JRFs with increases in load carriage, suggesting a coordinated adjustment in the musculature functions in the lower extremity. FE results reflected the complex effects of spatially varying material properties distribution and muscular engagement on tibial biomechanics during walking. We observed high stresses on the anterior crest and the medial surface of the tibia at pushoff, whereas high cumulative stress during one walking cycle was more prominent in the medioposterior aspect of the tibia. Our findings reinforce the need to include: (1) physiologically accurate loading conditions when modeling healthy subjects undergoing short-term exercise training and (2) the duration of stress exposure when evaluating stress-fracture injury risk. As a fundamental step toward understanding the instantaneous effect of external loading, our study presents a means to assess the relationship between load carriage and bone biomechanics.

scholarly journals Stress-strain distribution in intact L4-L5 vertebrae under the influence of physiological movements: A finite element (FE) investigation

2021 ◽  
Vol 1206 (1) ◽  
pp. 012024
Author(s):  
Devismita Sanjay ◽  
Neeraj Kumar ◽  
Souptick Chanda
Keyword(s):  
Finite Element ◽  
Strain Distribution ◽  
Analysis Data ◽  
Fe Model ◽  
Loading Conditions ◽  
Compression Load ◽  
Tetrahedral Elements ◽  
Functional Spinal Unit ◽  
Flexion Extension

Abstract This study is aimed at finding the stress and strain distribution in functional spinal unit of L4-L5 occurring due to physiological body movements under five loading conditions, namely compression, flexion, extension, lateral bending and torsion. To this purpose, 3D finite element (FE) model has been generated using 4-noded unstructured tetrahedral elements considered both for bones and intervertebral disc, and 1D tension-only spring elements for ligaments. The analyses were performed for a compression load of 500 N and for other load cases, a moment of 10 N-m along with a preload of 500 N was applied. The model was validated against in-vitro experimental data obtained from literature and FE analysis data for a range of motion (RoM) corresponding to various loading conditions. The highest stress was predicted in the case of torsion though the angular deformation was highest in case of flexion.

Development and Validation of Patient-Specific Finite Element Models of the Hemipelvis Generated From a Sparse CT Data Set

2008 ◽  
Vol 130 (5) ◽  
Author(s):  
Vickie B. Shim ◽  
Rocco P. Pitto ◽  
Robert M. Streicher ◽  
Peter J. Hunter ◽  
Iain A. Anderson
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Patient Data ◽  
Ct Scans ◽  
Patient Specific ◽  
Data Sets ◽  
Fe Model ◽  
Data Set ◽  
Spatially Varying ◽  
Ct Slices

To produce a patient-specific finite element (FE) model of a bone such as the pelvis, a complete computer tomographic (CT) or magnetic resonance imaging (MRI) geometric data set is desirable. However, most patient data are limited to a specific region of interest such as the acetabulum. We have overcome this problem by providing a hybrid method that is capable of generating accurate FE models from sparse patient data sets. In this paper, we have validated our technique with mechanical experiments. Three cadaveric embalmed pelves were strain gauged and used in mechanical experiments. FE models were generated from the CT scans of the pelves. Material properties for cancellous bone were obtained from the CT scans and assigned to the FE mesh using a spatially varying field embedded inside the mesh while other materials used in the model were obtained from the literature. Although our FE meshes have large elements, the spatially varying field allowed them to have location dependent inhomogeneous material properties. For each pelvis, five different FE meshes with a varying number of patient CT slices (8–12) were generated to determine how many patient CT slices are needed for good accuracy. All five mesh types showed good agreement between the model and experimental strains. Meshes generated with incomplete data sets showed very similar stress distributions to those obtained from the FE mesh generated with complete data sets. Our modeling approach provides an important step in advancing the application of FE models from the research environment to the clinical setting.

Preliminary Calibration and Validation of a Finite Element Model of THOR Mod Kit Dummy

2014 ◽  
Author(s):  
Costin D. Untaroiu ◽  
Jacob B. Putnam ◽  
Jeffrey T. Somers ◽  
Joseph A. Pellettiere
Keyword(s):  
Finite Element ◽  
Traffic Safety ◽  
Element Model ◽  
Crash Test ◽  
Fe Model ◽  
Loading Conditions ◽  
Highway Traffic ◽  
National Highway Traffic Safety ◽  
Spinal Loading ◽  
Safety Standards

New vehicles are currently being developed to transport crews to space by NASA and several commercial companies. During the takeoff and landing phase, vehicle occupants are typically exposed to spinal and frontal loading. To reduce the risk of injuries during these common impact scenarios, NASA has begun research to develop new safety standards for spaceflight. The THOR, an advanced multi-directional crash test dummy, was chosen by NASA to evaluate occupant spacecraft safety due to its improved biofidelity. Recently, a series of modifications were completed by the National Highway Traffic Safety Administration (NHTSA) to improve the bio-fidelity of the THOR dummy. The updated THOR Modification Kit (THOR-K) dummy was tested at Wright-Patterson (WP) Air Base in various impact configurations, including frontal and spinal loading. A computational finite element (FE) model of the THOR was developed in LS-DYNA software and was recently updated to match the latest dummy modifications. The main goal of this study was to calibrate and validate the FE model of the THOR-K dummy for use in future spacecraft safety studies. An optimization-based method was developed to calibrate the material properties of the pelvic flesh model under quasi-static and dynamic loading conditions. Data in a simple compression test of pelvic flesh were used for the quasi-static calibration. The whole dummy kinematic and kinetic response under spinal loading conditions was used for the dynamic calibration. The performance of the calibrated dummy model was evaluated by simulating a separate dummy test with a different crash pulse along the spinal direction. In addition, a frontal dummy test was also simulated with the calibrated model. The model response was compared with test data by calculating its correlation score using the CORA rating system. Overall, the calibrated THOR-K dummy model responded with high similarity to the physical dummy in all validation tests. Therefore, confidence is provided in the dummy model for use in predicting response in other test conditions such as those observed in the spacecraft landing.

scholarly journals Development of a Three-Dimensional Finite Element Model of Thoracolumbar Kyphotic Deformity following Vertebral Column Decancellation

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Tianhao Wang ◽  
Zhihua Cai ◽  
Yongfei Zhao ◽  
Guoquan Zheng ◽  
Wei Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Vertebral Column ◽  
Mechanical Response ◽  
Pedicle Screws ◽  
Peak Stress ◽  
Intervertebral Discs ◽  
Biomechanical Analysis ◽  
Kyphotic Deformity ◽  
Fe Model ◽  
Loading Conditions

Background. Vertebral column decancellation (VCD) is a new spinal osteotomy technique to correct thoracolumbar kyphotic deformity (TLKD). Relevant biomechanical research is needed to evaluate the safety of the technique and the fixation system. We aimed to develop an accurate finite element (FE) model of the spine with TLKD following VCD and to provide a reliable model for further biomechanical analysis. Methods. A male TLKD patient who had been treated with VCD on L2 and instrumented from T10 to L4 was a volunteer for this study. The CT scanning images of the postoperative spine were used for model development. The FE model, simulating the spine from T1 to the sacrum, includes vertebrae, intervertebral discs, spinal ligaments, pedicle screws, and rods. The model consists of 509580 nodes and 445722 hexahedrons. The ranges of motion (ROM) under different loading conditions were calculated for validation. The stresses acting on rods, screws, and vertebrae were calculated. Results. The movement trend, peak stress, and ROM calculated by the current FE model are consistent with previous studies. The FE model in this study is able to simulate the mechanical response of the spine during different motions with different loading conditions. Under axial compression, the rod was the part bearing the peak stress. During flexion, the stress was concentrated on proximal pedicle screws. Under extension and lateral bending, an osteotomized L1 vertebra bore the greatest stress on the model. During tests, ligament disruption and unit deletion were not found, indicating an absence of fracture and fixation breakage. Discussion. A subject-specific FE model of the spine following VCD is developed and validated. It can provide a reliable and accurate digital platform for biomechanical analysis and surgical planning.

Comparison of Deformable and Elastic Foundation Finite Element Simulations for Predicting Knee Replacement Mechanics

2005 ◽  
Vol 127 (5) ◽  
pp. 813-818 ◽  
Author(s):  
Jason P. Halloran ◽  
Sarah K. Easley ◽  
Anthony J. Petrella ◽  
Paul J. Rullkoetter
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Contact Pressure ◽  
Elastic Foundation ◽  
Knee Replacement ◽  
Contact Area ◽  
Contact Model ◽  
Computational Time ◽  
Loading Conditions ◽  
Pressure Surface

Rigid body total knee replacement (TKR) models with tibiofemoral contact based on elastic foundation (EF) theory utilize simple contact pressure-surface overclosure relationships to estimate joint mechanics, and require significantly less computational time than corresponding deformable finite element (FE) methods. However, potential differences in predicted kinematics between these representations are currently not well understood, and it is unclear if the estimates of contact area and pressure are acceptable. Therefore, the objectives of the current study were to develop rigid EF and deformable FE models of tibiofemoral contact, and to compare predicted kinematics and contact mechanics from both representations during gait loading conditions with three different implant designs. Linear and nonlinear contact pressure-surface overclosure relationships based on polyethylene material properties were developed using EF theory. All other variables being equal, rigid body FE models accurately estimated kinematics predicted by fully deformable FE models and required only 2% of the analysis time. As expected, the linear EF contact model sufficiently approximated trends for peak contact pressures, but overestimated the deformable results by up to 30%. The nonlinear EF contact model more accurately reproduced trends and magnitudes of the deformable analysis, with maximum differences of approximately 15% at the peak pressures during the gait cycle. All contact area predictions agreed in trend and magnitude. Using rigid models, edge-loading conditions resulted in substantial overestimation of peak pressure. Optimal nonlinear EF contact relationships were developed for specific TKR designs for use in parametric or repetitive analyses where computational time is paramount. The explicit FE analysis method utilized here provides a unique approach in that both rigid and deformable analyses can be run from the same input file, thus enabling simple selection of the most appropriate representation for the analysis of interest.

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