Post on 12-Jun-2020
Uponini'alheelcontact,theICRofthekneeislocatedwellbehindtheloadline.Stabilityduringheelcontactiscri'caltomaintainingnormalwalkingkinema'cs.AsthekneeflexesaBerini'alheelcontact,theloadlineislocatedslightlyanteriortotheloadline,butwithinareasonablerangetos'llofferstability.Followingthis,theICRislocatedwell
behindtheloadline,thereforecon'nuingtoprovidestabilitytotheuser.Finally,shortlybeforetoe-off,itisfoundthattheICRisnotlocatedinaposi'onthatwouldoffertheuserstability,yetthisframeistheleastimportantastheuser’s
weightwillalreadyhavestartedtransferringtotheotherlimbbythis'me.
Thefiniteelementanalysisoftheprosthe'ckneeshowsthattheconnec'onsbetweencomponentswouldfailfirstgivenanexcessiveload.Whensubjectedtotheforcesthatariseduringnormalgaitcondi'ons,however,thissimula'onshowsthatthemaximumstressinthiskneemechanismis9.983MPa.SincetheyieldstrengthofABS,acommonly-used3D-printablematerial,is34MPa[3],itisreasonabletoconcludethatthekneeiscapableofsuppor'ngitsuser’sweight.
Thedesignofhigh-qualityprosthesesisbothcostlyand'meconsuming.Duetothelackofaccesstoprosthe'cclinicsforlower-limbamputeesindeveloping
countries,itisdesirabletoformulateamethodofdesigningfunc'onalprosthe'ckneesatarela'velylowcost.
Whilemanyfactorsmustbeconsideredtoaccuratelyanalyzetheperformanceofaprosthe'cknee,thisprojectexaminesthefeasibilityofa3D-printedkneewithrespecttoitsstability.Afiniteelementanalysisofthe3D-printedkneeisalso
usedtoiden'fytheregionsofthekneemostsuscep'bletofailure.
Designaprosthe'ckneethat:- Canberapidlyproducedatalow-cost
- Canbeeasilycustomized- Isrela'velystable(asamechanically-
passiveknee)- Providesitsuserwithanacceptablerangeofmo'on(seeimageonright)
Introduc'on
MainGoals
Thefunc'onalityofthekneeisdirectlyrelatedtothelengthsofthelinksthatmakeupthefour-barkneemechanism.Using
SolidWorksandMATLABinconjunc'onwithexperimentalgaitdata,thelinklengthsofthiskneemechanismwereop'mizedinordertoprovidekneestability,par'cularlyduringini'alheel
contact.
Unlikeasimplehingejoint,thepointaboutwhichakneejointrotateschangesasanindividualambulates.Thischangingcenterofrota'on,orInstantaneousCenterofRota.on(ICR),isoneoftheprimarydeterminantsofkneestability.Whendesigningafour-barmechanismknee,itisimportantthattheICRofeachkneeremainsposteriortotheloadlineasitsrespec'velimb
contactstheground(seeaboveimage).
TheimagetotheleBshowsthefour-barkneemechanismanditsICR(outlinedbyacircle)infourdifferentposi'ons.IftheICRislocatedposteriorto(inthisimage,totheleBof)theloadline(in
red),thekneecanbeconsideredstable.
FiniteElementAnalysis(FEA)isapopulartoolusedtovisualizethedifferentstressesthatwillariseinanobjectuponbeingsubjectedto
appliedforces.Ifthiskneeprosthesisistobemanufacturedusing3Dprinters,itisnecessarytoensureitcanwithstandtheforcesthatwill
beappliedtoitduringnormalwalkingcondi'ons.Totherightisavisual
representa'onofthestressesthatarepresentinthiskneeprosthesiswhenitissubjectedto
theforcesthatariseuponheelcontact.
Methodology
Results-ICR
Results(FEA)
Conclusion
Designinga3D-printedprosthe'cknee
I’dliketothankDr.MarcDoumitforallofhisguidance,encouragement,andinspira'on.Addi'onally,I’dliketothankDr.AhsanAhmedandSco^Pardoelfortakingthe'metomeetwithme.Thehelpthatallofyouofferedwasincredibly
usefulandverymuchappreciated.- KieranEveleigh,KEVEL040@uo^awa.ca
-UsetheresultsoftheFEAtominimizetheoverallsizeoftheprosthesiswithouthinderingitsfunc'onality.-Adjustthelinklengthsoffour-barkneemechanismtocreateadesignthatoffersmoresupport.
-Mechanicallytesttheperformanceofthekneeprosthesis.
FutureWork
[1]Rose,Jessica,andJamesG.Gamble.HumanWalking.Philadelphia:Lippinco^Williams&Wilkins,2006.Print.[2]Radcliffe,CW.Four-barlinkageprosthe.ckneemechanisms:kinema.cs,alignmentandprescrip.oncriteria.Prosthe'csandOrtho'csInt.1994;18:168.
[3]“AcrylonitrileButadieneStyrene(ABS)TypicalProper'es.”Prospector.UL,2017.Web.07Mar.2017.
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KieranEveleigh,Dr.MarcDoumitDepartmentofMechanicalEngineering,UniversityofO^awa