STATIC & DYNAMIC BEHAVIOUR OF ACETABULAR CUP USING FINITE ELEMENT ANALYSIS

SCOPE

A Total Hip Replacement (THR) system is designed to restore the functionality and improve the long term performance of the hip implant, thus reduce pain.Forces applied to the prosthesis due to human activity generate dynamic stresses varying in time and resulting in the mechanical fatigue failure of implant material. Therefore it is important to ensure the hip prostheses against fatigue failure

* A TOTAL HIP REPLACEMENT (THR) - ALSO CALLED A HIP ARTHROPLASTY- IS A SURGICAL PROCEDURE THAT RE-FORMS THE HIP JOINT.

* THR SYSTEM USED TODAY HAS THREE COMPONENTS – THE FEMORAL STEM, THE FEMORAL HEAD, AND THE ACETABULUM.  EACH COMPONENT HAS MULTIPLE SIZES WHICH ALLOW FOR A CUSTOM FIT.

* IT IS DONE FOR DISORDERS LIKE OSTEOARTHRITIS, RHEUMATOID ARTHRITIS, TRAUMATIC ARTHRITIS, AVASCULAR NECROSIS AND OTHER REASONS AS MALIGNANT BONE AND PAGET’S DISEASE.

WHAT IS THR?

Why THR?

Normal Hip Smooth weight bearing surfaces Smooth cartilage Arthritic Hip Rough bone Bone spurs Irregular weight-bearing surfaces Worn cartiliage Narrow joint space An Xray report of the pateint for

diagnosis.

Basic Biomaterials used in Designing Acetabular cup Polyethylene articulation: eg

UHMWPE Metal articulation: The metal alloy

which has the successful clinical history in the world of prosthesis is cobalt chrome. It minimizes the wear debris regeneration and provides high strength.

Alumina ceramic

BASIC STRUCTURE OF THE CUP

Materials and methods

ALLOY MODULOUS OF ELASTICITY

POISSION RATIO

DENSITY

COBALT CHROMIUM ALLOY

240GPa o.32 8800 kg/m^3

* For FEA analysis in ANSYS we have taken solid45

Steps Performed in the Analysis of Acetabular cup using ANSYS

FILEIMPORTIGES Main MenuPreprocessorElement

typeAdd/edit/delete Main MenuPreprocessorMeshingMesh

tools Main menusolutiondefine

loadsapplystructuraldisplacement Main menusolutionsolvecurrent LS General postprocessorRead resultslast

set Main menugeneral postprocessorPlot

resultscontour plotnodal solution

ELEMENT TYPE: SOLID45 MESH: Volume mesh with the smart

size 7 BOUNDARY CONDITIONS: applied on

the upper surface of the cup LOADING : Calculated pressure on

the inner surface of the cup

THE ACETABULAR CUP DESIGNED USING PROE5.0

STRESS INTENSITY

VECTOR SUM OF DISPLACEMENT

VON MISES STRESS

Harmonic analysis:

It determines the maximum natural frequency at the particular node

 

***** ANSYS POST26 VARIABLE LISTING *****     TIME 108 UY UY_3 AMPLITUDE PHASE 100.00 0.163917E-06 0.00000 200.00 0.164086E-06 0.00000 300.00 0.164371E-06 0.00000 400.00 0.164771E-06 0.00000 500.00 0.165289E-06 0.00000 600.00 0.165928E-06 0.00000 700.00 0.166692E-06 0.00000 800.00 0.167585E-06 0.00000 900.00 0.168612E-06 0.00000 1000.0 0.169780E-06 0.00000 1100.0 0.171096E-06 0.00000 1200.0 0.172568E-06 0.00000 1300.0 0.174207E-06 0.00000 1400.0 0.176024E-06 0.00000 1500.0 0.178033E-06 0.00000 1600.0 0.180249E-06 0.00000 1700.0 0.182691E-06 0.00000 1800.0 0.185380E-06 0.00000 1900.0 0.188342E-06 0.00000

CONVERGENCE GRAPH

STRESS INTENSITY SMART SIZE19.6e4 820.1e4 621.50e4 4

PARAMATERS ANSYS Values Theoretical values

STRESS INTENSITY 19.65e4 19.7e4

VON-MISES STRESS 18.5e4 21.53e4

Conclusion:

In this project we have identified loosening as the most common failure aspect of acetabular cups and high stiffness figured out as the most contributed aspect to it, so by FEA we can finally figure out which material would be better to design our prosthesis so that it wont fail to withstand higher stresses.

THANK YOU