2.782J/3.961J/BEH.451J/HST524J2.782J/3.961J/BEH.451J/HST524JWEAR AND CORROSIONWEAR AND CORROSIONM. Spector, Ph.D.M. Spector, Ph.D.Massachusetts Institute of TechnologyMassachusetts Institute of TechnologyHarvard Medical SchoolHarvard Medical SchoolBrigham and Women’s HospitalBrigham and Women’s HospitalVA Boston Healthcare SystemVA Boston Healthcare SystemWEAR PROCESSESWEAR PROCESSESTotal Joint Replacement ProsthesesTotal Joint Replacement ProsthesesAdhesiveAdhesivewearwearparticle transferredparticle transferredto metal (THA)to metal (THA)AbrasiveAbrasivewear (THAwear (THA and TKA)and TKA)Crack propagated by cyclicCrack propagated by cyclic loading results inloading results in fatiguefatigue(delamination) wear (TKA)(delamination) wear (TKA)PE Component MetalMetalAsperityAsperityPage 1WEAR PROCESSESWEAR PROCESSESTYPETYPEMECHANISMMECHANISMPART. SIZEPART. SIZEAdhesiveAdhesiveChemical adhesion of PEChemical adhesion of PEnm tonm to mmmmmmTHA and TKATHA and TKAto asperity on metalto asperity on metalAbrasive (2Abrasive (2--body)body)Plowing of metal asperityPlowing of metal asperitymmmmmmTHA AND TKATHA AND TKAthrough PEthrough PEAbrasive (3Abrasive (3--body)body)Entrapment and plowing ofEntrapment and plowing ofmmmmmmTHA AND TKATHA AND TKAparticle ( bone, PMMA, coating)particle ( bone, PMMA, coating)Fatigue/Fatigue/Propagation of subsurfacePropagation of subsurface mmmmm to mmm to mmDelaminationDelaminationcracks to the surface by cycliccracks to the surface by cyclicTKATKAcompression, tension, shearcompression, tension, shearPage 2 Adhesive WearAdhesive WearAdhesive WearAdhesive WearText removed due to copyright restrictions.Definition of adhesive wear.WEAR PROCESSESWEAR PROCESSESAdhesiveAdhesivewearwearparticle adherentparticle adherentto metal (THA andto metal (THA and TKA)TKA)Abrasive,Abrasive, plowingplowing wear (THA andwear (THA and TKA)TKA)Crack propagated by cyclicCrack propagated by cyclic loading results inloading results in fatiguefatigue(delamination) wear (TKA)(delamination) wear (TKA)PE Component MetalMetalAsperityAsperityPage 3 Abrasive WearAbrasive WearAbrasive WearAbrasive WearText removed due to copyright restrictions.Definition of abrasive wear.-WEAR PROCESSESWEAR PROCESSESAbrasiveAbrasivewear (THAwear (THA and TKA)and TKA)PE MetalMetalAsperityAsperitySolutions are a scratch-resistant metal/ceramic counterface (and abrasion-resistant PE – x-linked PE?) WEAR PROCESSESWEAR PROCESSESAdhesiveAdhesivewearwearPE Component MetalMetalSolution: X linked PE appears to resist adhesive wear Page 4WEAR PROCESSESWEAR PROCESSESAdhesiveAdhesivewearwearparticle transferredparticle transferredto metal (THA)to metal (THA)PE Component MetalMetalProblem relates to lubrication WEAR PROCESSESWEAR PROCESSESCracks are due to oxidation and pre-existing fusion defects PE Component MetalMetalPage 5Page 6 WEAR PROCESSESWEAR PROCESSESCrack propagated byCrack propagated byfatiguefatigue(delamination) wear(delamination) wearPE Component MetalMetalSolution: do not sterilize with gg-radiation in air and start with better consolidated PE γγ-Radiation-InducedOxidationFusion DefectsRadiationRadiation--induced xinduced x--linkinglinkingSutulaSutula, , et alet alPhotos removed due to copyright restrictions.GAMMAGAMMA--RADIATION INDUCEDRADIATION INDUCED MODIFICATION OF POLYETHYLENEMODIFICATION OF POLYETHYLENECCCCCCCCCCCCCrossCross--linkinglinkingCCCCOOOxidationOxidationCrossCross--linkinglinkingincreases the size ofincreases the size of the molecule and thus increasethe molecule and thus increase strength, but this reduces ability ofstrength, but this reduces ability of the PE tothe PE to elongatateelongatate( reduces( reduces toughness).toughness).OxidationOxidationshortens PE chainsshortens PE chains and thus reduces strength.and thus reduces strength.Page 7 EFFECT OF GAMMA RADIATION ON EFFECT OF GAMMA RADIATION ON PE: OXIDATIONPE: OXIDATIONDiagram of PE crystallite structure removed due to copyright restrictions.WEAR PROCESSESWEAR PROCESSESAdhesiveAdhesiveAbrasiveAbrasivePE MetalMetalFatigue (delamination) wearFatigue (delamination) wearWhat is missing from this picture?What is missing from this picture?WEAR PROCESSESWEAR PROCESSESAdhesiveAdhesiveAbrasiveAbrasive PE MetalMetalJoint Fluid*Joint Fluid*Fatigue (delamination) wearFatigue (delamination) wear* What role does the joint fluid play in the wear of TKA?* What role does the joint fluid play in the wear of TKA?Page 8zz COMPOSITION OF JOINT FLUIDCOMPOSITION OF JOINT FLUIDMetalMetalJoint FluidJoint FluidHyaluronic Acid Protein (Lubricin) Phospholipid PE Two types of Lubrication:Two types of Lubrication:••Fluid FilmFluid Film••Boundary LayerBoundary LayerTRIBOLOGYTRIBOLOGYLubricationLubricationFrictionFrictionWearWearWhat are the interrelationships?What are the interrelationships?Does reduced friction correlate withDoes reduced friction correlate with reduced wear?reduced wear?How does lubrication affect friction andHow does lubrication affect friction and wear?wear?Page 9WEAR IN TKRWEAR IN TKRTribologyTribology••LubricationLubrication––Depends on amount, composition andDepends on amount, composition and mechanical properties of joint fluidmechanical properties of joint fluid ••FrictionFriction––Better the lubrication lower the frictionBetter the lubrication lower the friction••WearWear––Lower the friction, less wearLower the friction, less wearROLE OF SYNOVIAL FLUID IN THEROLE OF SYNOVIAL FLUID IN THE LUBRICATION OF ARTIFICIAL JOINTSLUBRICATION OF ARTIFICIAL JOINTS••How do the amount, composition andHow do the amount, composition and mechanical properties of synovial fluidmechanical properties of synovial fluid affect the performance of total jointaffect the performance of total joint replacements?replacements?••What is the mechanism of lubrication ofWhat is the mechanism of lubrication of artificial joints?artificial joints?••If injection of hyaluronic acid helps theIf injection of hyaluronic acid helps the patient with osteoarthritis would it helppatient with osteoarthritis would it help the total joint replacement patient?the total joint replacement patient?Page 10Image removed due to copyright restrictions. Diagram explaining coefficient of friction in artifical ball/socket joint. Example Coefficients of Friction Cartilage - Cartilage: 0.002 - 0.004 Metal - Metal (dry): 0.4 Metal - Metal (saline): 0.15-0.35 Metal - UHMWPE (serum): 0.05-0.15 Page 11 Mechanism of lubrication?Image