Designing a 3D-printed Methodology · the forces that arise upon heel contact. Methodology Results...

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