Presentation on theme: "Finite Element Analysis of Composite Hip Prosthesis"— Presentation transcript:
1 Finite Element Analysis of Composite Hip Prosthesis SIVA FROM IITGFinite Element Analysis of Composite Hip ProsthesisM. Sivasankar, D.Chakraborty, S.K.DwivedyDepartment of Mechanical EngineeringIndian Institute of Technology, Guwahati
2 Scope of the Present Work SIVA FROM IITGScope of the Present WorkAn overview of hip replacementReferences on total hip replacement (THR)ObjectiveMaterial selectionFinite element modelComparison of results
3 An Overview of Hip Replacement SIVA FROM IITGAn Overview of Hip ReplacementAnatomy of hip jointHip prosthesisTypes of prosthesis fixationReasons for hip failureA Typical HipProsthesisA Typical Hip Prosthesis
4 Anatomy of Hip Joint Largest weight bearing joint SIVA FROM IITGAnatomy of Hip JointLargest weight bearing jointComposed of rounded head of the femur joining the acetabulum of pelvis in a ball and socket arrangement
5 Reasons for Hip Failure SIVA FROM IITGReasons for Hip FailureLong-term aseptic loosening.Primary hip arthoplasties are subjected to failure due to bone resorption i.e. bone loss.Failure due to fatigue loading of hip joint.Relative micro motions resulting from improper implant fitting in the bone cavity.
6 Reasons for Hip Failure Cont.. SIVA FROM IITGReasons for Hip Failure Cont..In cementless implants load transfer between a stiff implant and relatively flexible bone results in extremely unnatural stress distribution in bone, i.e. excessive stress concentrations near to the implant ends.Stress shielding followed by bone resorption in the other areas of bone-implant interface.
7 Reasons for Hip Failure Cont.. SIVA FROM IITGReasons for Hip Failure Cont..Hip failure due to bone loss is caused by the production of wear particles associated with the deterioration of the prosthesisFor an average hip patient, the prosthesis have to resist thirty-four million blows
8 Damaged Femoral Head Femoral head cartilage SIVA FROM IITGDamaged Femoral HeadFemoral head cartilageThe neck is cut-off as in figureMarrow cavity is made inside the femurHip prosthesis is fitted either by PMMA cement or press fitted
9 References on Total Hip Replacement SIVA FROM IITGReferences on Total Hip ReplacementMany researchers carried out advanced researches in the field of THR using Finite Element Method and other methods
10 Literature Review Researches in this area has been carried out in: SIVA FROM IITGLiterature ReviewResearches in this area has been carried out in:Cemented JointCement less JointFinite Element AnalysisExperimental with design models
14 Comparison of Characteristics SIVA FROM IITGComparison of CharacteristicsCharacteristicS-SteelCo-Cr alloyTitanium AlloyStiffnessHighMediumLowStrengthCorrosion -resistanceBiocompatibility
15 SIVA FROM IITGNeed of CompositesThe isotropic alloys used for stem have much higher stiffness than that of the boneAlmost all monoclinic implants have 5 to 20 times more stiffness than the boneA stiff shaft of a total hip prosthesis stress shields the upper part of the thigh boneThe shielded bone does not thrive, loses its substance and becomes weakThe total hip joint has weak anchorage in a weak skeleton and may failThe remedy is a prosthetic shaft manufactured from metal alloys with stiffness similar to bone
16 Advantages of Composites SIVA FROM IITGAdvantages of CompositesLow stiffness of composite stems can enhance proximal bone ingrowthsTailorability property in strength and stiffness.Excellent biocompatibilityA controlled stiffness prosthesis can reduce stress shielding and bone resorptionLess weight of the prosthesis
17 SIVA FROM IITGComposite ProsthesisClinical studies reported early fatigue fracture of a femoral component made from laminated fiber reinforced composites.The new designs are Constructed of short glass fibers/epoxy resin and CF/PEEK composites.
19 SIVA FROM IITGComposite ModelBasic Composite Model With Elements
20 Conical Stem Cemented prosthesis model contains three main parts: SIVA FROM IITGConical StemCemented prosthesis model contains three main parts:Conical Stem with headCement layerCortical boneBasic Model
21 Model With Chopped Fiber Core SIVA FROM IITGChopped Fiber CoreModel With Chopped Fiber Core
22 Material Properties Used for Analysis of Total Hip Prosthesis PartsMaterialYoung’s Modulus (MPa)Poisson's RatioGeometrical Parameter (All dimensions are in mm)Head and Stem Ti6Al4V110x1030.33Sphere radius 25Stem radius 10Stem outer radius 10Stem inner radius 7.5Cement LayerUHMWPE-AL2O31x1030.39Inner radius 10.5Outer radiusLength 100Cortical BoneAS4/PEEK3x1030.30Inner radius 20.5Outer radius 30
23 Maximum Shear Stress Region SIVA FROM IITGMaximum Shear Stress RegionEnlarged View of the Deformed Stem and Cortical Bone Showing the Maximum Shear Stress Region (Path Aa)
24 Variation of Shear Stresses Variation of Maximum Shear StressWith System ParametersStem Length(in mm)Maximum Shear Stress(in MPa)14517.314145.515.522147.521.03315020.919152.517.14415520.262Neck Length(in mm)Maximum Shear Stress(in MPa)4513.33747.517.3765017.31452.525.363Neck Inclination(in degree)Maximum Shear Stress(in MPa)4517.31447.520.3835022.964Stem Inner Radius(in mm)Maximum Shear Stress(in MPa)7.517.314820.6558.519.443
25 Continued...The variation in the above parameters do not show a particular trendHence the design optimization has been carried out to minimize the magnitude of maximum shear stress
26 Dimensions of Hip Prosthesis Before Optimization Dimensions of Hip Prosthesis Before OptimizationPartsState VariablesDesign VariablesFemurSphere Radius25 mmStem Outer Radius10 mmStem Inner Radius7.5 mmNeck Inclination450Stem Length145.5 mmNeck length50 mm
27 Design Variables of Femoral Components After OptimisationDesign VariablesDimension (mm)Stem outer radius9.9301Stem inner radius8.0405Stem length153.22Neck length50.975
28 SIVA FROM IITGShear StressesSXYx-y componentSYZy-z componentSXZz-x componentShear Stresses in the Interface of Stem and Cortical Bone
29 Shear Stresses - Continued… SIVA FROM IITGShear Stresses - Continued…SXYx-y componentSYZy-z componentSXZz-x componentShear Stresses in the Interface of Stem and Cortical Bone
30 ConclusionA 3D finite element analysis has been done for analysis of composite hip prosthesis which consists of a conical stem with a cement layer.Location and magnitude of shear stresses show the region of failure which is in agreement with the earlier published results.
31 Continued…As the variation of the parameters do not show a particular trend, design optimization has been carried out to minimize the magnitude of maximum shear stressThe optimum dimensions obtained from the present analysis show considerable reduction in shear stress
32 References A. Phillips, 2001, Finite element analysis of the acetabulum after impaction grafting, The University of Edinburgh. P.J.Prendergast, 1997, Review paper – Finite element models in tissue mechanics and orthopaedic implant design, Clinical Biomechanics, Vol. 12, No. 6, C. F. Scifert, T. D.Brown, J. D.Lipman, 1999, Finite element analysis of a novel design approach to resisting total hip dislocation, Clinical Biomechanics, 14, M.Baleani, M.Viceconti, R. Muccini, M. Ansaloni, 2000, Endurance verification of custom-made hip prostheses, International journal of fatigue 22, P. B. Chang, B. J. Williams, K.S. B.Bhalla, T. W. Belknap, T. J. Santner, W. I. Notz, D. L. Bartel, 2001, Design and analysis of robust total joints replacements: Finite element model experiments with environmental variables, ASME, Journal of Biomechanical .Engineering, 123, H. Katoozian, D. T. Davy, A. Arshi, U. Saadati, 2001, Material Optimization of femoral component of total hip prosthesis using fiber reinforced polymeric composites, Medical Engineering and Physics, 23, S. K. Senapati, S. Pal, 2002, UHMWPE-ALUMINA ceramic composite, an improved prosthesis material for an artificial cemented hip joint, Trends in Biomaterials Artificial. Organs, 16(1), 5-7. J.Stolk, N. Verdonschot, L. Cristofolini, A. Toni, R. Huiskes, 2002, Finite element and experimental models of cemented hip joint reconstructions can produce similar bone and cement strains in pre-clinical tests, ASME, Journal of Biomechanics 35, C. Li, C. Granger, H. D. Schutte Jr, S. B. Biggers Jr, J. M. Kennedy, R. A. Latour Jr, 2003, Failure analysis of composite femoral components for hip arthroplasty, Journal of Rehabilitation Research and Development, 40(2), 131–146.