Upload
colin-mckinney
View
221
Download
0
Tags:
Embed Size (px)
Citation preview
Finite Element Analysis of Composite Hip Prosthesis
M. Sivasankar, D.Chakraborty, S.K.Dwivedy M. Sivasankar, D.Chakraborty, S.K.Dwivedy
Department of Mechanical EngineeringDepartment of Mechanical Engineering
Indian Institute of Technology, GuwahatiIndian Institute of Technology, Guwahati
2
Scope of the Present Work
An overview of hip replacementReferences on total hip replacement (THR)ObjectiveMaterial selection Finite element modelComparison of results
3
An Overview of Hip Replacement
Anatomy of hip joint
Hip prosthesis
Types of prosthesis fixation
Reasons for hip failure
A Typical Hip Prosthesis
A Typical Hip Prosthesis
4
Anatomy of Hip Joint
Largest weight bearing joint
Composed of rounded head of the femur joining the acetabulum of pelvis in a ball and socket arrangement
5
Reasons for Hip Failure
Long-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
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.
Reasons for Hip Failure Cont..
7
Reasons for Hip Failure Cont..
Hip failure due to bone loss is caused by the production of wear particles associated with the deterioration of the prosthesis
For an average hip patient, the prosthesis have to resist thirty-four million blows
8
Damaged Femoral Head
Femoral head cartilage
The neck is cut-off as in figure
Marrow cavity is made inside the femur
Hip prosthesis is fitted either by PMMA cement or press fitted
9
References on Total Hip Replacement
Many 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:
Cemented Joint
Cement less Joint
Finite Element Analysis
Experimental with design models
11
Researches Carried Out
S.No. Experiment Based FEM based Cemented Joint Cementless Joint
1 G.Bergmann(2001) C.F.Scifert (1999) S.K.Senapathi (2002) P.Kowalczyk (2001)2 G.Selvaduray(2002) A.Philips (2001) P.Colombi (2002) 3 H.Katoozian (2001) P.Kovalczyk(2001) A.B.Lennon (2003) 4 J.A.Simoes (2000) P.B.Chang (2001) Sheryl Zimmarman (2002)
5 M.Baleani(2000) R.Huiskes (1992) V.Waide (2004) 6 C.Kaddick (1997) C.Li (2002) P.J.Prendergast (1997) 7 N.H.Tai (1995) W.Van Papegem (2001) A.Philips (2001)
8 G.Dillon (1995) S.Srinivasan (2000) C.Li (2002) 9 X.Diao (1997) H.F.El.Sheikh (2003) 10 B.W.Stansfield (2003) S.Gross (2001) 11 M.Pawlikowwski S.H.Teoh (2002) 12 S.L.Evans (1998) Bernard Weisse (2003) 13 R.P.Morris H.Katoozian (2001) 14 M.T.Raimondi (1999) 15 C.M.Styles (1998) 16 I.Hilal (1999) 17 Darryl.D 18 S.Srinivasan (2000) 19 L.J.Lee (1996) 20 W.Vanpaepegem (2002) 21 S.Ramakrishna (2001) 22 K.L.Reifs nider (1991) 23 S.K.Roy Choudhury (2004)
24 A.Rajadurai (2002) 25 R.De.Santis (2004) 26 Vesa Saikko (2002) 27 Debera.E Hurwitz (2003) 28 B.Mavcic (2002)
12
Recent Work
Few researchers like A.Phillips[1], P.J.Prendergast [2] ,H.Katoozian [6], C.Li [9] etc., work in the area of cemented prosthesis.
13
Biomaterials
Stainless Steel Alloys
Cobalt-Chrome alloys (Vitallium)
Titanium alloys
Composites
14
Comparison of Characteristics
Characteristic S-Steel Co-Cr alloy Titanium Alloy
Stiffness High Medium Low
Strength Medium Medium High
Corrosion -resistance Low Medium High
Biocompatibility Low Medium High
15
Need of Composites
The 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 bone
The 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
Low stiffness of composite stems can enhance proximal bone ingrowths
Tailorability property in strength and stiffness.
Excellent biocompatibility
A controlled stiffness prosthesis can reduce stress shielding and bone resorption
Less weight of the prosthesis
17
Composite Prosthesis
Clinical 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.
18
SOLID 92 Element
19
Composite Model
Basic Composite Model With Elements
20
Conical Stem
Cemented prosthesis model contains three main parts:
Conical Stem with head
Cement layer
Cortical bone
Basic Model
21
Chopped Fiber Core
Model With Chopped Fiber Core
22
Material Properties
Material Properties Used for Analysis of Total Hip Prosthesis
Parts Material Young’s Modulus (MPa)
Poisson's Ratio
Geometrical Parameter (All dimensions are in mm)
Head and Stem
Ti6Al4V 110x103 0.33 Sphere radius 25Stem radius 10Stem outer radius 10Stem inner radius 7.5
Cement Layer
UHMWPE-AL2O3
1x103 0.39 Inner radius 10.5Outer radius 12.2182Length 100
Cortical Bone
AS4/PEEK 3x103 0.30 Inner radius 20.5Outer radius 30
23
Maximum Shear Stress Region
Enlarged 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 Stress With System Parameters
Stem Length (in mm)
Maximum Shear Stress(in MPa)
145 17.314
145.5 15.522
147.5 21.033
150 20.919
152.5 17.144
155 20.262
Neck Inclination (in degree)
Maximum Shear Stress(in MPa)
45 17.314
47.5 20.383
50 22.964
Neck Length (in mm)
Maximum Shear Stress(in MPa)
45 13.337
47.5 17.376
50 17.314
52.5 25.363
Stem Inner Radius (in mm)
Maximum Shear Stress(in MPa)
7.5 17.314
8 20.655
8.5 19.443
25
The variation in the above parameters do not show a particular trend
Hence the design optimization has been carried out to minimize the magnitude of maximum shear stress
Continued...
26
Hip Prosthesis
Parts State Variables Design Variables
Femur
Sphere Radius 25 mm
Stem Outer Radius
10 mm
Stem Inner Radius
7.5 mm
Neck Inclination
450
Stem Length 145.5 mm
Neck length 50 mm
Dimensions of Hip Prosthesis Before Optimization
27
Femoral Components
Design Variables of Femoral ComponentsAfter Optimisation
Design Variables Dimension (mm)
Stem outer radius 9.9301
Stem inner radius 8.0405
Stem length 153.22
Neck length 50.975
28
Shear Stresses
SXY
x-y component
SYZ
y-z component
SXZ
z-x component
Shear Stresses in the Interface of Stem and Cortical Bone
29
Shear Stresses - Continued…
SXY
x-y component
SYZ
y-z component
SXZ
z-x component
Shear Stresses in the Interface of Stem and Cortical Bone
30
Conclusion
A 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 stress
The optimum dimensions obtained from the present analysis show considerable reduction in shear stress
32
References
[1] A. Phillips, 2001, Finite element analysis of the acetabulum after impaction grafting, The University of Edinburgh.[2] P.J.Prendergast, 1997, Review paper – Finite element models in tissue mechanics and orthopaedic implant design, Clinical Biomechanics, Vol. 12, No. 6, 343-366.[3] 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, 697-703.[4] M.Baleani, M.Viceconti, R. Muccini, M. Ansaloni, 2000, Endurance verification of custom-made hip prostheses, International journal of fatigue 22, 865-871. [5] 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, 239-246.[6] 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, 503-509.[7] 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.[8] 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, 499-510.[9] 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.
33
Questions?
34
Thank You for Attending…
A copy of my slides will be available on my website www.biosankar.4t.com
My email address is: [email protected]
IITG Biomechanics center: www.iitg.ernet.in
Work supported by Department of Mechanical Engineering,
contact +91 (361) 2582697