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AmericanAcademyofOrthotists&ProsthetistsProfessionalsAdvancingCareThroughKnowledge

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StateoftheScienceReviewofTranstibialProsthesisAlignmentPerturbation

EdwardS.Neumann,PhD,PE,CP,FAAOP

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ABSTRACT

AsystematicreviewofresearchontheeffectsoftranstibialprosthesisalignmentperturbationongaitwascarriedoutfollowingguidelinespreparedbytheAmericanAcademyofOrthotistsandProsthetists.Approximately278referencespublishedsince1973wereobtainedbysearchingkeydatabasesandthenscreenedforrelevance,resultingin34publishedresearcharticles,whichwereevaluatedforinternalandexternalvalidityusingpublishedcriteriaandassignedratingsofhigh,moderate,orlow.Amatrixwasdevelopedthatclassifiedthe34articlesbythetypeofalignmentperturbationsundertakenandtheoutcomemeasuresused.Thematrixusedeightcategoriesofperturbationsand43distinctoutcomesmeasuresrelatedtothetotalbody,gaitsymmetry,EMGandoxygenconsumption,andkinematicandkineticmeasurementsoftheprostheticandcontralaterallimb.Thesearticleswereusedtogenerate113evidencestatementspertainingtotheeffectofalignmentperturbationongait.Eachofthestatementswasassignedaconfidenceratingofhigh,moderate,low,orinsufficientevidencebasedonthevolumeandqualityofthepublishedevidence.Fortythreestatementsjudgedtohavehighormoderatelevelsofconfidenceassociatedwiththemarepresentedanddiscussed,alongwithrecommendationsconcerningfutureresearchonalignmentperturbationstudies.(JProsthetOrthot.200921:175193.)

Systematicreviewsofthequalityofthescientificliteratureinspecificdomainsofmedicalknowledgearegrowinginimportance.Themotivationforthisistoimproveclinicaldecisionmakingthroughapplicationoftheprinciplesofevidencebasedpractice,whichrequireanassessmentofavailablescientificevidence.TheAmericanAcademyofOrthotistsandProsthetistshasdevelopedguidelinesfordevelopingStateoftheScienceEvidenceReports,whichassessthevalueofthescientificliteraturefororthoticandprostheticclinicalpractice.1Themethodologyoftheassessmentinvolvesthedevelopmentofclinicallyrelevantquestions,whicharereformulatedasstatementsinastylesimilartohypotheses,followedbyasearchofliteraturedatabasesforpotentiallyrelevantarticles.Criteriaofinclusionandexclusionareusedtonarrowthepotentialarticlesdowntojustthosethatfacilitateanassessmentoftheoverallqualityoftheevidence,whichexiststosupportthestatements.Eacharticleisevaluatedindividuallywithrespecttoasetofinternalandexternalvaliditycriteria.Thestatementsarethenassignedanoverallconfidenceratingbasedonthenumberandqualityoftheindividualstudies.Thecriteriahelptominimizethesubjectivityinassessingthearticles,butthejudgmentoftheevaluatorsstillenterstheprocess,particularlyintheassignmentofconfidencelevelstothestatements.Asecondarygoaloftheguidelinesistoidentifygapsandshortcomingsinexistingresearch,sothatscientistscanimprove



thedesignoffutureexperiments.Thefirstapplicationoftheguidelineswasforpartialfootamputations.2ThestudyreportedhereappliestheguidelinestoareviewoftheresearchthathasbeenconductedonthealignmentoftranstibialprosthesesandcitedindatabasesthroughJanuaryof2008.

Benchalignmentistheinitialalignmentproducedduringprosthesisfabricationbeforeitisplacedonthepatient,andoftenfollowsguidelinesestablishedandprovidedbythemanufacturersofprostheticfeetandknees.Staticalignmentisundertakenwiththeprosthesisonthepatientandsomeweightbearing,andoccursbeforewalking.Itofteninvolvesexaminationandcorrectionofpylonheightandgeneralalignmentoftheprostheticcomponents.Dynamicalignmentfollowsandinvolveshavingthepatientwalkwiththeprosthesis.Avarietyofgaitcharacteristicsareexaminedbyobservingthepatientandaskingthepatienttoreportwhetherthealignmentproducessensationsthatmayindicatemisalignment.Thisreviewfocusesonstaticanddynamicalignment.Manufacturerrecommendationsconcerningbenchalignmentwerenotreviewed.

METHODS

INCLUSIONCRITERIATobeincluded,articleshadtobepublishedinEnglish,examinetheeffectsofperturbationsoftranstibialprosthesesasaprimaryorsecondaryresearchgoal,describetheperturbationsquantitatively,andreportresultsquantitatively.Articlesconcerninginstrumentationformeasuringalignmentoralignmentperturbationsalsowerereviewed,buttheywereexcludediftheyfailedtoincludedataonperturbationoutcomes.Becauseoftherelativescarcityofstudiesonalignmentperturbation,testsofstatisticalsignificancewerenotarequirementforinclusion.However,lackoftestsofstatisticalsignificanceloweredconfidenceinthequalityoftheevidenceirrespectiveofthemagnitudesofthedifferencesinoutcomesbetweentheacceptableandperturbedalignments.Similarly,failuretopresentdataintablesthatpermittedinspectionoftheactualreportedvaluesalsoloweredconfidenceinthequalityoftheevidence.Articlesinconferenceproceedingsandalimitednumberofabstractswereincludediftheymettheinclusioncriteria.Foranabstractorpostertobeincluded,ithadtoidentifyperturbationsandreportoutcomesinsufficientdetailtobeusefulfordevelopingevidencestatements.

EXCLUSIONCRITERIAArticlesinlanguagesotherthanEnglishwereexcluded.Articlesthatexaminedamputeegaitbutdidnotexaminetheeffectsofalignmentperturbationwereexcluded.Articlesthatexaminedjusttransfemoralprosthesisalignmentwereexcluded.Nodissertationswereincluded.Itwasassumedthattheresultsofdissertationswouldbepublishedbytheauthor.ArticlesthatcouldnotbelocatedthroughthelibraryservicesattheUniversityofNevada,LasVegas,despitefullcitationsforthem,wereexcluded.Articleswerenotexcludedbecauseofageorsmallsubjectsamplesizes.

SearcheswereundertakenusingtheRECAL,RECALLegacy,MEDLINE,WebOKnowledge,CochraneReviews(WileyInterScience),CINHAL,andScienceDirectdatabases.TheRECALdatabasewasusedtoproducetheinitiallistofpublications,andtheotherdatabaseswereusedtoaugmentthelistwitharticlesnotindexedintheRECALdatabase.Byusingthewords"prosthesisalignment,"33referenceswereobtainedfromtheRECALdatabase,butseparatingthesearchtermintothetwowords"prosthesis"and"alignment,"thenumberofreferencesincreasedto278,andthisbecametheinitiallisttowhichadditionalreferenceswereadded.TheRECALLegacydatabaseproducedonly36referencesusingthewords"prosthesisalignment,"noneofwhichwerenew.AMEDLINEsearchwasundertakenusingtheterms([topic=artificiallimborMeSHheading:exp=artificiallimbs]andtopic=alignment),whichproduced81references,severalofwhichwerenew.AsearchoftheCochraneReviewsrevealedthat



nonehadbeenconductedonthealignmentofexternallimbprostheses.CINHALproduced18resultsusingtheterms(["prosthesis"and"alignment"]andDE"LimbProsthesis"),noneofwhichwerenew.ScienceDirectproduced16referencesusingthekeywords"amputee"and"alignment,"severalofwhichwerenewbecausetheywerestillinpressorjustrecentlypublished.

TheexpandedRECALlistoftitleswasexaminedforrelevancytotranstibialprosthesisalignment,whichnarrowedthelistdownto55articles.Applicationoftheinclusionandexclusioncriteriafurthernarrowedthelistdownto34articles,whichwerereviewedindetail.Thirtyonewereclassifiedascontrolledbeforeandaftertrials,onewasconsideredtobeacrosssectionalstudy,andtwowereclassifiedascaseseries.NineofthearticleshadappearedinProstheticsandOrthoticsInternational,fourintheJournalofRehabilitationResearchandDevelopment,andthreeeachinGait&Posture,ClinicalBiomechanics,andIEEEConferenceProceedings.TwoappearedintheTransactionsoftheASMEJournalofBiomechanicalEngineering,andtheremainingarticlesweresinglepublicationsinavarietyofjournalsorconferenceproceedings.Thenumberofarticlesontranstibialalignmentincreasedineachofthedecadessince1970to1979,whenonlyonemeetingtheinclusioncriteriawaslocated.From1980through1989,sixarticleswerelocated,from1990through1999,13articleswerelocated,andfrom2000tothetimethisreviewwasbeguninJanuaryof2008,14articlesmeetingtheinclusioncriteriawerelocated.

Forthereview,eightalignmentperturbationvariablesweredefinedastypicallyusedinO&Pacademicprogramsandbypracticingclinicians.Thesevariablesincludedsocketflexionextensionwithrespecttothepylon(rotatingthebrimanteriororposterior,respectively),socketabductionadductionwithrespecttothepylon(rotatingthebrimmedialorlateral,respectively),footanteriorposteriortranslationwithrespecttothesocket,footmediallateraltranslationwithrespecttothesocket,footplantarflexiondorsiflexionwithrespecttotheankle,footinversioneversionwithrespecttheankle,footinternalexternalrotationwithrespecttothesocket,andpylonheight(length).

OUTCOMEMEASURECLASSIFICATIONAvarietyofoutcomemeasureswerereportedinthereviewedpublications.Aclassificationhierarchywasdeveloped,which,atthefirstlevel,classifiedandmadedistinctionsamongstudiesthatexaminedoutcomesrelatedtothetotalbody(I,totalbodymeasures),bothlimbs(II,bilateralcomparisons),andtheprostheticlimb(III,prostheticlimb).Totalbodymeasures(I)studiesexaminedthesubjectiveacceptabilityofalignment,oxygenuptake,totalbodyandjointworkorenergy,walkingspeed,andcadence.Bilateralcomparisons(II)studiescomparedtheprostheticandcontralaterallimbsorexaminedmeasuresofsymmetry.CategoryIIIstudiespresentedoutcomesfortheprostheticlimb.Inmanycases,studieswereassignedtomultiplecategoriesiftheevidencehadbeenexaminedfrommultipleperspectives.

Thesecondlevelofthehierarchyclassifiedstudiesbyoutcomevariable.Thebroadcategoriesofoutcomevariablesweregaittemporalspatialcharacteristics(phaseduration,steplengthorstrideduration),electromyogram(EMG)activity,groundreactionforceorpylonforce(extremespeakmagnitudes,extremestiming,impulse,centerofpressuretrajectory,orlocation),jointkinematics(rangeofmotion.ROM./peakangles,peakangletiming,andangularvelocity),jointkinetics(moment,impulse,power,andwork),andintrasocketforces(normalpressures,shearforces).Theintrasocketforcesubcategoriesofnormalpressureandshearforces,whichwereapplicableonlytotheprostheticlimb,werefurtherdividedintothefollowingcategories:extremesmagnitude,extremestiming,patterns/durations,andimpulse.A344cellmatrixwasdevelopedwiththeeightperturbationvariablesrepresentedbycolumnsandthe43outcomesmeasuresrepresentedbyrows.Thematrixwasusedtoclassifythestudies.Figure1indicatestherelationshipsamongthesevariablesandshowsthatmanyoftheoutcomesmeasureswerederivedfrommodelsandbasedondatacollectedusingcomplexinstrumentationinalaboratorysetting.



CRITERIAFORASSESSINGINTERNALANDEXTERNALVALIDITYTheAmericanAcademyofOrthotistsandProsthetistshasdevelopedalistofthreatstointernalandexternalvalidityforuseinpreparingStateoftheScienceEvidenceReports.1Thethreatsinthislistaregeneralandwereexpandedforuseinthisassessment(AppendixA).Theexpandedcriteriareflectspecificthreatstothevalidityofresearchstudiesonalignmentperturbationsandweredevelopedduringapreliminaryreviewofthe34researcharticlesselectedforpreparationoftheevidencetables.Eachofthestudieswasassignedalow,moderate,orhighlevelofconfidenceforinternalandexternalvalidityusingthesecriteria.Table1summarizesthekeycriteria.TheresultsfortheindividualarticlesareinAppendixB.

Ifastudyfailedtoreportthepresenceorabsenceofstatisticalsignificancewithrespecttoanoutcome,itwasautomaticallyassignedalowlevelofconfidenceforinternalvalidity.Toachieveamoderateratingforinternalvalidity,testsofstatisticalsignificancehadtobepresent,anddatahadtobedescribedsufficiently(i.e.,meansandvariances)topermitresultstobecomparedwithsimilarstudies.Toachieveahighratingforinternalvalidity,samplesizehadtobegreaterthan5toensurethatindividualtoindividualvariabilitywasnotinfluencingtheresults,andthatthepresenceorabsenceofcauseandeffectwasbeingdemonstrated.Threatcriteriauniquetoexternalvalidityincluded,amongotherthings,useofsolidanklecushionedheel(SACH)feetandpatellartendonbearing(PTB)sockets,lackofanadequatedescriptionoftheperturbations,failuretointerpretfindingswithrespecttoclinicalrelevance,failuretointerpretresultsinthecontextoftheexistingliterature,andtheappearanceofpotentialconflictsofinterest.ThepervasiveuseinthestudiesofSACHfeetandtraditionalPTBsocketsfeaturingPelitelinerswerenotareasonfordowngradingstudies,althoughthesemaylimittheextenttowhichgeneralizationscanbemade.Becauseevidencehasnotbeendevelopedtoeithersubstantiateorrefutetheseconcerns,studieswerenotdowngraded.

Outcomesthatweresubjectspecificalsorepresentedapotentialthreattoexternalvalidity.However,outcomeshighlydependentonuniqueaspectsoftheresearchsubjectmaybearealityforsomealignmentphenomena.Forexample,socketintrapressureperceptionsandmeasurementsmightbesubjectspecificbecauseofpotentiallylargevariationsamongamputeeswithrespecttoresiduallimbmorphology,amputeesignaldetectionsensitivities,socketdesigns,andqualityofsocketfit.Inrecognitionofthis,studiesreportingresultsforsinglesubjectsthatwereconsistentwithrecognizedbiomechanicalprinciplesandtheorywerenotautomaticallydowngraded.

Ifastudyfindingdemonstratedagreementwithbiomechanicalprinciplesandtheory,theauthordevelopedanexternalvalidityratingforitbasedonitspotentialusefulnessindevelopingevidencetables.Forexample,ifthestudylackedtestsofstatisticalsignificance,butresultsseemedtobeinagreementwithstudiesthatdidundertaketestsofstatisticalsignificance,oriftheyseemedtoagreewithanumberofotherstudiesofsimilarinternalvalidity,itmayhavereceivedahigherratingforexternalvaliditythanforinternalvalidity.Thus,studiesreceivingaratingofLowoninternalvaliditycouldreceiveratingsofmoderateonexternalvalidity.However,nostudyreceivingaratingoflowoninternalvaliditycouldbeassignedaratingofhighonexternalvalidity.Studiesreceivingaratingofhighoninternalvaliditycouldreceiveamoderateratingwithrespecttoexternalvalidityifthesubjectsseemedtohaveuniquecharacteristicsthatcouldlimitgeneralizations,orifthenumberofsubjectswassmall.

EVIDENCESTATEMENTSFortheevidencestatements,theword"Confidence"wasusedtoindicatethelevelofassuranceonecouldplaceinitstruth.ThecriteriadefiningeachoftheselevelsarepresentedinTable2.Foranevidencestatementtobeassignedahighlevelofconfidence,itwasnecessarythatatleasttwoorthreestudieswithhighexternalvalidityratingsandoutcomesagreedwiththestatements,oralargernumberofstudieswithmoderateexternalvalidityratingsandoutcomesagreedwiththestatement.Tobeassignedamoderatelevelofconfidence,itwasnecessarythatatleastonestudywithhighexternalvalidityratings



andoutcomesagreedwiththeevidencestatement,oratleasttwostudieswithmoderatelevelsofexternalvalidityagreedwiththeevidencestatement.Tobeassignedaninsufficientevidencelevelofconfidence,itwasnecessarytofindatleastonestudywithamoderatelevelofexternalvalidity,ormultiplestudieswithlowexternalvalidity,whichagreedwiththeevidencestatement,ormultiplestudieswithmoderateorlowlevelsofexternalvaliditythatcametocontradictoryconclusions.Ratinganevidencestatementashavingalowlevelofconfidenceindicatedthatevidenceexistedwhichrefutedthestatement,ortherewereobviousandseriousshortcomingsinthestudydesign,andonecouldplacenoassuranceintheresults.Inotherwords,alowlevelofconfidenceimpliedthattherecouldbeagreaterprobabilitythatthestatementisfalsethanthatitistrue.

RESULTS

Tabel4indentifiesthe34articlesreviewedindetail,indicatingthetypeofstudy,thenumberofsubjectsincludedinthestudy,whetherstatisticaltestsofsignificancewereundertaken,andtheratingsassignedforinternalandexternalvalidity.Withrespecttointernalvalidity,sevenarticleswereratedhigh,10wereratedmoderate,and17wereratedlow.Withrespecttoexternalvalidity,fivearticleswereratedhigh,26wereratedmoderate,andthreewereratedlow.

Theresulting344cellclassificationmatrixisshowninTable4.Eachofthe34articlesexaminedindetailappearatleastonceinthematrix.Manyofthecellsareempty,indicatingthatnostudiesfeaturedthatparticularcombinationofperturbationandoutcomemeasure.Afewofthecellsarerepresentedbyasmanyaseightstudies.Manyofthestudiesareenteredinmorethanonecellbecauseoftheiruseofmultipleperturbationsoroutcomesmeasures.Manyofthenonemptycellshaveonlyoneortwoentries,indicatinghowdiffusepublishedresearchonalignmenthasbeen.

Symbolsusedinthetableindicateseveralimportantcharacteristicsofeachstudy.Areferenceinboldindicatesthattestsofstatisticalsignificancewereundertakenwithrespecttothealignmentvariableandoutcomemeasure.Studiesvariedinthereportingofsignificance.Manyusedp



DISCUSSION

STUDYTYPEANDDESIGNResearchinvolvingperturbationsinthesagittalplane(socketflexionextensionorfootanteriorposteriortranslation)dominatedthestudies,andgroundreactionforceswerestudiedmorefrequentlythanjointkinematicsandkinetics.Thisisbecauseofthefactthathumanlocomotionentailsmovementprimarilyinthesagittalplane,andtheinstrumentationusedtomeasuregroundreactionforcewasrelativelycommoninthelaboratorieswheretheresearchwasconducted.Therewerefewerstudiesthatexaminedtheeffectsofperturbationsinthefrontalplane,andonlyalimitednumberthatexaminedeffectsinthetransverseplane.Aresearchdesignclassifiedas"controlledbeforeafter"representedmorethan91%ofthestudies.Therewerenorandomizedclinicaltrials.Fiftysixpercentofthestudieswerebasedonfiveorfewersubjects,andthelargestnumberofsubjectsinanystudywas18.Controlledbeforeafterdesignsandarelativelysmallnumbersofsubjectsaretypicalofresearchinorthoticsandprosthetics.Thecostsofconductinggaitstudies,thechallengesofobtainingmeasurementsinvolvingmotioncaptureorEMGdata,therelativescarcityofamputeesubjects,andthedifficultyofcontrollingforthepotentiallylargenumberofconfoundingvariablesalmostnecessitatesstudiesbasedonrelativelysmallnumbersofsubjects.

EVIDENCESTATEMENTSThelargenumberof"insufficientevidence"judgmentsresultedfromseveralfactors.First,internalandexternalvalidityissueswerecommon,withafailuretoconducttestsofstatisticalsignificancebeingdominant.Smallsamplepopulationswereasecondmajorreason.Athirdreasonwasthediversityoftheperturbationvariablesexaminedandoutcomesmeasuresused.Fewresearchersduplicatedthedesignsofotherstudies,andmanycellsoftheclassificationmatrixhadonlyalimitednumberofstudiesonwhichevidencestatementscouldbebased.

Nearlyallthestudiesbeganwithanacceptablealignment,usedexperiencedamputees,andstudiedtheeffectsofperturbationsawayfromanacceptablealignment.Forthesereasons,alltheevidencestatementsareprefacedwiththewording"Amongexperiencedunilateraltranstibialamputeeswalkingforshortperiodsoftimeonalevelsurfaceinacontrolledenvironment(e.g.,gaitlaborclinic)duringexperimentsinwhich(someaspectofprosthesisalignmentisbeingperturbed)...."Thiscautionsthereaderthattheevidencestatementscannotbeassumedtoapplytonewamputeesortononlaboratoryconditions.Noneofthestudiesrequiredindividualstogainexperiencewithorattempttoadapttotheperturbationsoverdaysorweeks,soitisnotknownifthevaluesofsomeoftheoutcomemeasuresmayhavebeendifferentifthemisalignedprostheseshadbeenusedforlongertimeperiods.

Statementscanbemadeatamoderatelevelofconfidencethatwithanacceptablealignmentanumberofsignificantkinematicandkineticdifferencesexistbetweentheprostheticlimbandthecontralaterallimbduringgait.Thesevariablesincludethemagnitudeoftheverticalpeakgroundreactionforcepeakkneeflexionanglesandtimingandkneeextensionmoment,impulseandwork(ES1,3,4).Groundreactionforceimpulseseemstoexhibitnosignificantdifferencebetweenlimbs(ES2).Significantdifferencesalsoseemtooccurduringgaitinitiationwithanacceptablealignmentbutdependonwhichlimbisinitiatingswingandwhichisinstanceinitially(ES812).

Astatementjudgedtohaveahighlevelofconfidencebecauseevidenceseemedconsistentacrossnumerousstudies,wasthatwalkingspeedexhibitednosignificantchangewithperturbationofsocketangularalignment,footlinearposition,orfootinternalexternalrotationwhensubjectswereallowedtowalkataselfselectedcomfortablespeed(ES5).Arelatedstatementjudgedtohaveamoderatelevelofconfidencewasthatcadenceexhibitednosignificantchangewithperturbationofsocketangular



alignment,footlinearposition,orfootinternalexternalrotation(ES6).Evidencealsowasfoundatamoderatelevelofconfidencetosupportthehypothesisthatperturbationsproducenosignificantchangesinthesymmetriesofgroundreactionforcepeaks(ES7).

Thesefindingsmayreflectthelaboratoryprotocolsandtheuseofexperiencedamputees.Oneofthearticles,whichwasbasedonclinicalobservationsandwasnotusedinthedevelopmentofthesestatementsbecauseofalackofmeasurementsandstatisticaltests,reportedthatwalkingspeedandcadenceseemedlowerwithanunacceptablealignment,andstepsweretakenwithmorehesitance(ER9).Theauthor'sownclinicalobservationssupportthis.Furtherresearchisneededtoverifywhetherdisparitiesexistbetweenmeasuresofwalkingspeed,cadence,andpeakgroundreactionforcesobtainedusingthelaboratorysettingsandprotocolsandthesamemeasurementsobtainedinclinicalsettings.Inclinicalpractice,thepractitionerusuallybeginswithabenchorstaticalignmentthatoftenisunacceptableandproceedstoworktowardanalignmentthatisacceptabletotheamputee.Theresearchissuesmightbe1)whethertheamputeeperceivesandrespondstotheeffectsofaspecificalignmentthesamewayirrespectiveoftheacceptabilityoftheinitialalignmentand2)whethertherearepsychologicalandmotivationalfactorsrelatedtogaitthatleadtodifferentoutcomesbetweenclinicalandlaboratorysettings.

Thesecondstatementjudgedtohaveahighlevelofconfidencewasthatarangeofsocketflexionextensionangularalignmentsinthesagittalplaneincombinationwitharangeoffootanteriorposteriortranslationsseemtoresultinacceptablealignments(ES13).Therangewillvaryfrompatienttopatient(ES15).Researchconductedontherollovershapeofprostheticfeetsupportedthisfindingandofferedapossibleexplanation:alignmentattemptstomatchtherollovershapeoftheprostheticfootwiththatoftheanatomicfoot,andacceptablealignmentscanbeachievedalonganarchavingequivalentrollovergeometries(ES14).Evidencealsosupportedastatementatthemoderatelevelofconfidencethattherangeofacceptablealignmentsdecreasesifthewalkingsurfaceisinclined(ES16).Intrasocketpeakpressuresseemtorespondtosocketflexionextensioninthemannerforecastbyalignmentparadigms(ES17).3

Withrespecttofrontalplanesocketabductionadduction,itcanbestatedatamoderatelevelofconfidencethatarangeofalignmentsincombinationwitharangeofmediallateralfoottranslationsareacceptabletotheamputee(ES18),andtherangevariesfromindividualtoindividual(ES19).Atthesamelevelofconfidence,itcanbeassertedthatpeakverticalgroundreactionforcesontheprostheticlimbshownosignificanteffectsfromalignmentperturbation(ES20).

Regardingtheeffectsofprostheticfootplantarflexionanddorsiflexion,thenumberofstudiesfoundwasinsufficienttosupportstatementshavingmoderateorhigherlevelsofconfidence.Onestudyexaminedtheeffectsofheelandforefootwedgingusingarelativelylargesampleandobtainedintrasocketpressureresultsconsistentwithbiomechanicalparadigmsforalignmenttosupportonestatementatamoderatelevelofconfidence(ES21).Dataonsignalpowereffectsontheresiduallimbsupportedstatementsatamoderatelevelofconfidencethatheelwedgingincreasestheenergyabsorbedbythedistaltibiaanddecreasestheenergyabsorbedbythesubpatellarregionandviceversa(ES23,24).

StatementsconcerninganteriorposteriortranslationofthefootcanbeincludedunderES13discussedpreviously.Therangeofacceptabletranslationsvariesfromindividualtoindividual(ES25).Atamoderatelevelofconfidence,itcanbeclaimedthatpressureonthedistaltibiaincreasesasthefootistranslatedposterioranddecreasesasthefootistranslatedanterior,whichisconsistentwithalignmentparadigms(ES26).Similarstatementscanbemadeatamoderatelevelofconfidencewithrespecttomediallateraltranslationoftheprostheticfoot(ES2729).

Evidencedevelopedthroughstudiesoftheeffectsofinternalandexternalrotationofthefootsupport,at



themoderatelevelofconfidence,claimsthattherangeofacceptablealignmentsvariesfromindividualtoindividual(ES30),andthatinternalrotationof6seemstoproducesignificanteffectsontheprostheticlimbwithrespecttosinglelimbsupporttime(ES31)andkneejointpeakkneeflexionangle(ES32),whereas6ofexternalrotationdoesnot.Sixdegreesofinternalrotationalsoproducessignificanteffectsonthecontralaterallimbwithrespecttopeakkneejointextensionmoment,impulse,andwork,whereas6ofexternalrotationdoesnot(ES36).ClaimsofnosignificanteffectonpeakgroundreactionforcesfortheprostheticlimbcanbemadeataModerateLevelofConfidenceforupto6ofinternalrotationand36ofexternalrotation(ES33).Claimsofnosignificanteffectsatthesamelevelofconfidencecanbemadeforkneejointmomentsontheprostheticlimbforupto15ofinternalandexternalrotation(ES34).Forkneejointimpulseandwork,nosignificanteffectshavebeenclaimedforupto6ofinternalandexternalrotation.Thus,theavailableevidencesuggeststhatamputeesmaybemoresensitivetointernalfootrotationthantoequalamountsofexternalfootrotation.Theevidencealsosuggestsatentativehypothesisthattheeffectsofinternalrotationmayappearmorestronglyaskneerelatedkinematicvariablesontheprostheticsideandkneerelatedkineticvariablesonthecontralateralside.

Asmallnumberofstudiesvariedpylonlength,butonlyonereportedfindingsthatfacilitatedthedevelopmentofEvidenceStatements.Thisstudyexaminedtheeffectsofpylonlengthinthecontextofgaitinitiation.Itfoundnosignificantchangesingroundreactionforcepeakmagnitudesandtiming,andprostheticfootcenterofpressurepatternsforaheightvariationof2cm(ES3739).

INTERNALVALIDITYCONCERNSOnethreattotherepeatabilityofnearlyallthestudiesreviewedwasthefailureoftheresearcherstomeasurethesubjectiveacceptabilitytotheamputeesoftheinitialalignmentsandsubsequentalignmentsresultingfromperturbations.Giventhatarangeofalignmentsseemstobeacceptable,iftwodifferentprosthetistssettheinitialacceptablealignmentatoppositeendsoftherangeofacceptablealignmentsforanamputee,thentheoutcomesforidenticalperturbationscouldbedifferent.Withoutincorporatingsomeconsistencyanduniformityintothetaskofaskingsubjectstojudgetheacceptabilityofanalignment,andunlessthetaskisdescribedinthepublicationsthatresult,anexperimentinvolvingalignmentperturbationcannotbereproducedaccurately.Researchshouldbeconductedtodevelopaconsistentmethodofmeasuringsubjectiveacceptabilityandtodeterminehowrapidlyitchangeswithalignmentperturbation.

Asecondpervasiveshortcomingofnearlyeverystudywasthelackofmeasurementoftheinitialacceptablealignmentfromwhichperturbationswereundertaken.Althoughthestudiesdescribedalignmentperturbationsquantitatively,theynearlyalwayslackedaquantitativedescriptionoftheinitialalignment,whichmakesitimpossibletoreproducethemaccurately.Thesestudiesreportedtheeffectsofperturbations,whichwererelativetoastartingpointthatlackedquantification.Oneofthemajorreasonsforthisisthelackofinstrumentationwhichcanbeusedtomeasuretherelativealignmentofthefootwithrespecttothesocket.Inexpensivebutaccurateinstrumentationthatcanbeusedtoquicklymeasureprosthesisalignmentbymeansofastandardizedreferencesystemisneededforresearchonalignment.Thiswouldbeusefulnotonlyforscientificresearchstudiesbutalsofordocumentinginterventionsandprovidingdataformedicalrecordsintheclinic.Bermeetal.4hasdescribedaconceptual3axissystemformeasuringsocketorientationSandersetal.5describedadevicetomeasuresocketangularorientationwhenaBerkeleyAdjustableLegisusedforalignmentSinetal.6describedanalignmentjigforquantificationoftranstibialprosthesisalignmentandKerretal.7designedadevicetomeasuresocketorientationwithrespecttothefoot.However,noinexpensivecommercialsystemsarecurrentlyavailableforclinicaluse.

Samplesizesinthestudieswereoftensmall,possiblyduetothecomplexityandcostofundertakingoutcomemeasurementsrelatedtothemuscleactivity,kinematic,andkineticeffects,andpossiblyalso



becauseofthelimitednumberofamputeesubjectsavailableforresearchstudies.Asthenumberofsubjectsgrows,thepowerofthestatisticaltestsalsogrows,andthestrongerandmoregeneralaretheconclusionsthatcanbedrawnfromtheresults.Thedemonstrationofgeneralcauseandeffectrelationshipsconcerningalignmentperturbationisdifficulttoestablishwithonlyonesubject.Withonlytwoorthreesubjects,datamayshoweachsubjecttobeauniquecase.Thiswasavalidityconcernaffectingsomeofthestudiesonintrasocketpressures.

EXTERNALVALIDITYCONCERNSManyofthestudiesseemedtobedesignedtostudygaitratherthantoanswerclinicalquestionsconcerningthecharacteristicsofanacceptablealignment.Onlyasmallnumberofstudiesactuallybeganwithbenchalignmentsandendedwithacceptabledynamicalignments,andonlyaverysmallnumberofstudiespresentedconclusionsthatwereusefulforalignment.Asaresult,fewofthestudiesproducedfindings,whichcouldbeapplieddirectlyintheclinic.

Clinicallyrelevantresearchshouldalsoexaminetherelationshipbetweenthesubjectiveacceptabilityofanalignmentandgaitofvaryingduration,whichmaybetterreflectrealworldconditions.Kluteetal.8measuredthecontinuousgaitdurationsof12transtibialamputeesduringdailyliving,andfoundtheyperformnumerousactivitiesthathavegaitspansof1to2minutesatcadencesoflessthan17stepsperminute,andtheyperformfewactivitiesinvolvinggaitspansofmorethan15minutes.Thenumberofstepsperminuteseemedtopeakatapproximately70andwasassociatedwithactivitieshaving10minutegaitspans.Whengaitspanincreasedbeyond10minutes,thenumberofstepsperminutedecreased.Theauthorsconcludedthatalignmentshouldbe"optimized"for1to2minuteboutsofactivityatcadencesoffewerthan17stepsperminute.

Definitionsforperturbationslackedconsistencyacrossthestudiesandrarelymatchedthoseusedbyclinicians.Tointerpretthestudiescorrectlyrequiredtransformationofthedataintoaclinicalframeofreference,whichwasbothdifficultandtimeconsuming.Aneffortshouldbemadetostandardizealignmentterminologyanddisseminatethedefinitionstoresearchers.

ManyofthestudiesusedSACHfeetandPTBsocketsfeaturingPeliteliners.SACHfeethavemechanicalcharacteristicsthatareunlikethoseofenergystorageandreturnfeet,whichmaylimitsomefindingsjusttoSACHfeet.SACHfeethaveaneffectivefootlengthratio(theproportionoftheprostheticfootlengthactuallyusedduringastep)thatisshortincomparisontoenergystorageandreturnfeetandanatomicfeet.9Theeffectivefootlengthratiodeterminesthelengthoftherollovershapeofthefoot,whichinturninfluencesgait,andlikelyexertsaninfluenceonalignment.Arelevantresearchquestioniswhethertherangeofacceptablealignmentsvariesbytypeoffoot.AlthoughPelitelinersarestillinuse,manygellinersarenowbeingprescribedbecauseoftheirabilitytoabsorbandspreadintrasocketpressureconcentrationsoveragreaterarea,therebydecreasingdiscomfortandreducingthepotentialfortissuetrauma.Althoughthereisnoevidencedirectlyindicatingthatpressureconcentrationsinfluencegait,theexistenceofarelationshipbetweenintrasocketpressureandtheacceptabilityofalignmentiswellknownamongpractitioners.Itisnotknownifgellinersincreasetherangeofacceptablealignmentsforamputees.

Allofthestudiesusedsubjectswhohadatleast1yearofexperienceasatranstibialamputee.Individualswiththismuchexperiencemayhavelearnedtocompensateforvariationsinalignment.Fromaclinicalperspective,itisthenewamputeeforwhomalignmentismostcritical.Newamputeesandexperiencedamputeeswhoarebeingfittedwithnewcomponentsmaytakeseveralweeksandseveralvisitstoachieveanacceptablealignment.Forthenewamputee,thiscouldbeacriticalperiodoftime,andthequalityofthealignmentcouldinfluencesubsequentrehabilitationprogress.However,noneofthestudiesexaminednewamputees.



OPTIMALALIGNMENTAsawhole,thereisinsufficientevidencetomakestatementsabouttheexistenceofmeasurablevariablesthatdefineanoptimalalignment.Optimizationimpliestheminimizationormaximizationofsomevariableorobjectivefunction.EvidenceStatementswithhighormoderatelevelsofconfidenceindicatethatgroundreactionforcepeaksandtiming,walkingspeed,andcadencewillnotrevealmisalignment.However,nineofthearticlesobtainedresultswhichsuggestedthatmeasurableindicatorsofoptimalalignmentmayexisteventhoughtheevidencepresentlyisinsufficient(ER2,57,14,17,24,25,30).

Asmallamountofevidencepointstowardjointkineticsandkinematicsaspossibleindicatorsofmisalignment.Beyaertetal.,op.cit.(ER2),focusedontheroleofthecontralateralkneeasamechanismforprotectingtheprostheticlimbthroughshockabsorptionatthebeginningofstanceanddevelopedevidencethatanuncomfortablemisalignmentbecauseofinternalrotationofthefootproducedmaximalcontralateralkneeflexionandwork.Mizrahietal.,op.cit.(ER14),andSeliktaretal.,op.cit.(ER25),examinedoscillationsinthetransitionofanteriorposteriorgroundreactionforcefrombrakingtopropulsiveasapotentialindicatorofinstabilityatthekneeontheprostheticlimb.Theyproposedthatanoptimumalignmentwouldcorrelatetoaminimizationoftheseoscillations.Nofurtherresearchonthisconceptwasfoundintheliterature.Reedetal.,op.cit.(ER17),describedpreliminaryattemptstousepatternrecognitionandsignalprocessingmethodstoidentifymisalignmentbasedonanumberofkineticandkinematicvariables.Theyproposedthat"gaitdistortion"(thetermwasnotdefined)increasedmonotonicallywithmisalignment,whichimpliesthataminimumof"distortion"wouldexistatanoptimalalignment.Preliminaryresultsobtainedusingdiscriminantanalysisseemedpromising.Nofurtherresearchonthisconceptwasfound.

WinarskiandPearson,op.cit.(ER30),foundtotalbodyjointworktobeminimizedforacceptablealignment.Ifthisisthecase,furtherresearchonmuscleactivity(EMG)andoxygenuptakewouldprovideadditionalevidence.Schmalzetal.,op.cit.(ER24),foundoxygenconsumptiontoincreasesignificantlywithfootplantaranddorsiflexionandanteriorposteriordisplacement.Fangetal.,op.cit.(ER7),simulatedmuscleactivityandestimatedthatjointexternalmomentswouldbeincreasedwithsocketflexionextensionfromacceptablealignment.Burnfieldetal.,op.cit.(ER5),alsofoundrelationshipsbetweenmisalignmentandmuscleactivity.Incontrast,Chowetal.,op.cit.(ER6),foundthatsteplength,stanceduration,verticalgroundreactionforce,andtimetomaximumkneeflexionexhibitedthehighestsymmetrybetweentheprostheticlimbandcontralaterallimbacrossarangeofacceptablealignmentsbutraisedthepossibilitythattheabilityofthemusculoskeletalsystemtoadapttochangesinprosthesisalignmentmaymeanthatarangeofalignmentsareequallyoptimal.Despiteallofthesefindings,thecurrentamountandqualityofevidenceisinsufficienttoplacemoderateorhighlevelsofconfidenceingeneralizedstatements.

STUDYLIMITATIONSThearticleswerereviewedandevaluatedbyonlyoneindividualratherthanseveralindividuals.ThesameindividualdevelopedtheEvidenceStatementsandassignedconfidencelevels.Anelementofsubjectivitywasnecessary,althoughtheguidelinespreparedbytheAcademywithrespecttoassessmentofvalidityminimizethis.Somestudieslackedaccurate,cleardescriptionsoftheperturbationsbeingexamined.Althoughaneffortwasmadetocorrectlyinterpretthenatureoftheperturbationsandtranslateresultsintoaconsistentsystemofclinicaldefinitions,errorsmaypossiblyhaveoccurred.Contradictionsbetweentables,graphs,andstatementsinsomearticlesposedanotherthreat.Thepowerofthestatisticalsignificancetestsusedinthestudieswasnotdetermined.Becauseofthesmallsamplesizes,itislikelythatsomeofthetestslackedahighpower.

CONCLUSIONS



TheguidelinesthathavebeendevelopedbytheAcademyareusefulforevaluatingthequalityofthescientificevidenceavailabletoassistclinicaldecisionmaking.Byusingtheguidelines,thisstudyhopefullyhascontributedtothedesignoffuturestudiesonthealignmentoftranstibialprostheses.Alignmentresearchdoesnotattractfundingtotheextentthatcomponentresearchdoes,becausealignmentisconsideredtobeanonreimbursableservicethatprosthetistsroutinelyperform,unlikecomponentsthatprosthetistscanbillinsuranceprogramsfor.

Prosthetistshavebeenabletoproduceacceptablealignmentsforyearswithminimalscientificknowledge,or"evidence,"anditisreasonabletoaskwhatcanbegainedfromfurtherresearchonalignment.Severalbenefitscanbeidentified.First,thesophisticatedandcomplexanklecomponentscomingonthemarketmayrequirehigherstandardsofalignmenttoachievetheirbiomechanicalpotential.Second,manufacturersofsuchcomponentsneedtodevelopdesignswhosealignmentrequirementsmatchthecapabilitiesofclinicians.Third,cliniciansneedtobeabletodetect,diagnose,understand,andcorrectgaitproblemscausedbyalignment.Alignmentisoneofthemajordeterminantsofdiscomfortfortheamputee.Giventheimportanceofachievingcosteffectivenessinrehabilitationprograms,itisimportanttominimizediscomfortandenergyexpendituretotheextentpossible,sothatthemosteffectiveuseofexpensiveprostheticcomponentscanbeachieved.Becauseofwhatappearstobeanincreasingrateofgrowthinthenumberofresearcharticlesonalignment,togetherwiththeimportanceofalignmenttosuccessfuloutcomesintheclinic,itisrecommendedthatsystematicreviewsoftheresearchtranstibialalignmentbeundertakenatregularintervals.

Disclosure:Theauthorsdeclarenoconflictofinterest.

Correspondenceto:EdwardS.Neumann,PhD,PE,CP,FAAOP,CenterforDisabilityandAppliedBiomechanics,UniversityofNevada,Box4015,4505SMarylandParkway,LasVegas,NV891544015email:[email protected]

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EDWARDS.NEUMANN,PhD,PE,CP,FAAOP,isaffiliatedwiththeCenterforDisabilityandAppliedBiomechanics,UniversityofNevada,LasVegas,Nevada.

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