Rev. bras. ortop. vol.51 número2

w w w . r b o . o r g . b r

Original

Article

Clinical

repercussions

of

Martin-Gruber

anastomosis:

anatomical

study

夽

Cristina

Schmitt

Cavalheiro

,

Mauro

Razuk

Filho

,

Gabriel

Pedro

,

Maurício

Ferreira

Caetano

_,

_Luiz

_Angelo

_Vieira

_,

_Edie

_Benedito

_Caetano

a_{SchoolofMedicalandHealthSciences,PontifíciaUniversidadeCatólicadeSãoPaulo,Sorocaba,SP,Brazil} b_{HandSurgeryService,ConjuntoHospitalardeSorocaba,Sorocaba,SP,Brazil}

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r

t

i

c

l

e

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n

f

o

Articlehistory: Received4May2015 Accepted11June2015

Availableonline23February2016

Keywords: Arteriovenous

anastomosis/anatomy&histology Mediannerve

Ulnarnerve

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b

s

t

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t

Objective:The mainobjective ofthis study wastodescribe Martin-Gruberanastomosis anatomicallyandtorecognizeitsclinicalrepercussions.

Method:100forearmsof50adultcadaversweredissectedinananatomylaboratory.The dissectionwasperformedbymeansofamidlineincisionalongtheentireforearmandthe lowerthirdoftheupperarm.Twoflapsincludingskinandsubcutaneoustissuewerefolded backontheradialandulnarsides,respectively.

Results:Nervecommunicationbetweenthemedianandulnarnervesintheforearm (Martin-Gruberanastomosis)wasfoundin27forearms.Theanastomosiswasclassifiedintosix types:typeI:anastomosisbetweentheanteriorinterosseousnerveandtheulnarnerve (n=9);typeII:anastomosisbetweentheanteriorinterosseousnerveandtheulnarnerve attwopoints(doubleanastomosis)(n=2);typeIII:anastomosisbetweenthemediannerve andtheulnarnerve(n=4);typeIV:anastomosisbetweenbranchesofthemediannerveand ulnarnerveheadingtowardtheflexordigitorumprofundusmuscleofthefingers;these fasciclesformaloopwithdistalconvexity(n=5);typeV:intramuscularanastomosis(n=5); andtypeVI:anastomosisbetweenabranchofthemediannervetotheflexordigitorum superficialismuscleandtheulnarnerve(n=2).

Conclusion:Knowledgeoftheanatomicalvariationsrelatingtotheinnervationofthehand hasgreatimportance,especiallywithregardtophysicalexamination,diagnosis, progno-sisandsurgicaltreatment.Ifthesevariationsarenotgivendueregard,errorsandother consequenceswillbeinevitable.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

夽

WorkdevelopedintheDepartmentofSurgery,SchoolofMedicalandHealthSciences,SorocabaCampus,PontifíciaUniversidade CatólicadeSãoPaulo,Sorocaba,SP,Brazil.

∗ _{Correspondingauthor.}

E-mail:cristinaschmitt@hotmail.com(C.S.Cavalheiro). http://dx.doi.org/10.1016/j.rboe.2016.02.003

anatômico

Palavras-chave: Anastomose

arteriovenosa/anatomiae histologia

Nervomediano Nervoulnar

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e

s

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o

Objetivos: DescreveranatomicamenteaanastomosedeMartin-Gruberereconhecersuas repercussõesclínicas.

Método: Foramdissecados100antebrac¸osde50cadáveresadultosnolaboratóriode anato-mia.Adissecc¸ãofoifeitaatravésumaincisãomedianaemtodooantebrac¸oeterc¸oinferior dobrac¸o,doisretalhosincluindoapeleesubcutâneoforamrebatidos,paraoladoradiale ulnarrespectivamente.

Resultados: Acomunicac¸ãonervosaentreosnervosmedianoseulnarnoantebrac¸o (anas-tomosedeMartin-Gruber)foiregistradaem27antebrac¸os.Classificamosaanastomoseem seistipos.TipoI:anastomoseentreonervointerósseoanterioreonervoulnar(nove mem-bros);TipoII:anastomoseentreonervointerósseoanterioreonervoulnaremdoispontos (duplaanastomose-doismembros);TipoIII:anastomoseentreomedianoeonervoulnar (quatromembros);TipoIV:anastomoseentreramosdosnervosmedianoeulnardestinada aomúsculoflexorprofundoosdedos,essesfascículosformamumaalc¸adeconvexidade distal(cincomembros);TipoV:anastomoseintramuscular(cincomembros);TipoVI: anas-tomoseentreramodonervomedianoparaomúsculoflexorsuperficialenervoulnar(dois membros).

Conclusão: Oconhecimentodasvariac¸õesanatômicasemrelac¸ãoàinervac¸ãodamãotem importânciarelevante,principalmentequandoseconsideraoexamefísico,diagnóstico, prognósticoetratamentocirúrgico.Seessasvariac¸õesnãoforemvalorizadas,errose con-sequênciasserãoinevitáveis.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Todososdireitosreservados.

Introduction

Theanatomyoftheupperlimbsisextremelycomplex.In addi-tiontothe complexityoftheformatofthebrachial plexus andtheexistenceofstrategicanatomicalzonessuchasthe epitrochlear-olecranongroove(ulnarcanal),carpalcanaland Guyoncanal,anomalousnervebranchescanbefound.These mayformanastomosesinparticularsitesthathaveclinical andfunctionalimportance.

Theinnervationpatternthatismostacceptedinrelation totheintrinsicmusclesthatactinrelationtofinemovements ofthehandisthattheopposingshortabductormuscle,the superficial portion ofthe short flexormuscle and the first andsecondlumbricalmusclesreceiveinnervationfromthe mediannerve.Thedeepportionoftheshortflexormuscle,the adductormuscleofthethumb,themusclesofthehypothenar region,thedorsalandpalmarinterosseousmusclesandthe fourthandfifthlumbricalmusclesareinnervatedbytheulnar nerve. The great varietyof clinical conditions observed in casesofisolatedlesionsofthemedianorulnarnerveledus toinvestigatethis.

Clinically,variationsoftheinnervationofthesesmall mus-clesareveryimportant,inthatevenifthemedianorulnar nerveiscompletelytorn,someofthesemusclesmaynot nec-essarilybeparalyzed.Thiscouldleadtothewrongconclusion thatthenervehadnotbecomecompletelytorn.

The studies that we consulted showed many diver-gences,andthesebecame moremarkedwhenthe authors

used different investigative methods. The methods used includedelectroneuromyography,selectiveanesthetic block-ageofnervesandanatomicaldissection.Clinicalreportsand electroneuromyographic studies have suggested that these musclesmayreceivedoubleinnervationfromthemedianand ulnar nerves.Highet1_{analyzed45patientswithcompletely} tornmedianorulnarnervesandfoundthattheshortflexor muscleofthethumbwastotallyparalyzedinonlyfiveofthem. Forrest2_{drewattentiontothisandstatedthatcommunication} betweenthemedianandulnarnervesinthehandmightbe morefrequentthanisimaginedandthatthemuscleslocated closeto thiscommunication (nerveanastomosis) mightbe receivinginnervationfrombothnerves(doubleinnervation).

Fig.1–Medianincisioninthevolarfacealongtheentire forearm.

Nerve communication between the median and ulnar nervesintheforearm,whichisknownasMartin-Gruber anas-tomosis,causestransferofnervefasciclesfromthemedian nervetotheulnarnerve.Thisgivesrisetoalterationofthe nor-malanatomicalpatternofthemotorandsensoryinnervation ofthehand.ItwasfirstdescribedbyMartin,3_{whoconsidered} thepossibilityofcommunicationbetweenthesenervesinthe forearm.Around100 yearslater,in1870,Gruber4 _dissected 250forearmsandfoundcommunicationbetweenthesetwo nervesin38ofthem.

It has been demonstrated in the literature that the incidenceofthis nervecommunication varieswhen differ-ent investigative methods are compared, i.e. according to whetherelectroneuromyography,selectiveanesthetic block-ageofnervesoranatomicaldissectionisused.Accordingto Sunderland,5_{severalfactorscausedifficultyinevaluatingthe} motorfunctionofthehand.Themostimportantoftheseare anatomicalvariationsorfailuretoevaluatetheroleof decep-tivemovements,giventhatthesemayimitateandcoverup forlossofthe originalmovements.If thesefactorsare not properlyvalued,errorsinmakingdiagnosesandassessingthe resultswillbeinevitable.

Methods

Dissectionswereperformedon100forearmsof50adult cadav-ersbelongingtoourAnatomy Laboratory,amongwhich46 weremaleandfourwerefemale.Theiragesrangedfrom28to 77years;27werewhiteand23werenonwhite.Forearmsthat hadbeendeformedthroughinjury,malformationorscarring wereexcluded.

Thedissectionwasperformedbymeansofamedian inci-sion along the entire forearm and the lower third of the upperarm.Twoflapsthatincludedtheskinandsubcutaneous tissuewere pulled backtoward the radialand ulnar sides, respectively.Thesamewasdoneinrelationtothefasciaof theforearm, andthus theentiremusculaturewasexposed (Figs.1and2).

All ofthemuscles ofthe forearmwere dissected. Their innervation and the presence of nerve communication betweentheforearmnerveswereanalyzed.Alltheanatomical variationsencounteredwererecorded,annotatedand photo-graphed.AKeelermagnifyingglassof2.5×wasused.A1cm

segmentoftheanastomoticramuswasremovedandtaken toasurgicalmicroscope.Withtheaidofmicrosurgical twee-zers,thefascicleswereseparated,countedandphotographed.

Fig.2–Twoflapsthatincludedtheskinandsubcutaneous tissuewerepulledbacktoexposethefasciaandthenthe musculatureoftheforearm.

Infourlimbs,werecordedonlyonefascicle;ineight,two;in nine,three;infour,four;inone,five;andinone,seven.

InadditiontoinvestigatingMartin-Grubernerve commu-nication,therelationshipbetweentheGantzermuscleandthe anteriorinterosseousandmediannervesandtheanatomical variationsoftheforearmmuscleswereanalyzed.Thisstudy wasapprovedbytheResearchEthicsCommittee.

Results

Werecordedthe presenceofMartin-Gruberanastomosisin 27ofthe100forearmsdissected.Bilateralitywasobservedin threecadavers.In13cases,nervecommunicationoccurredin theleftforearmandin14casesintherightforearm.Regarding thetopographiclocation,mostofthenervecommunications occurredintheproximalthirdoftheforearm.

Inthemostfrequentlyencounteredformof communica-tion, whichwas seeninnine forearms, the nervefascicles originatedfromtheanteriorinterosseousnerve,atavarietyof sites,andheadeddistallyatwidelyvaryingdegreesof obliq-uity. They were locatedposteriorly tothe ulnar artery and weresupportedonthedeepflexorsofthefingers,anteriorly tothem.Theyheadedtowardtheulnarnerveandjoinedtoit closetothejunctionbetweentheproximalthirdandmiddle thirdoftheforearm.Inallofthesecases,thefascicles origi-nateddistallytotheelbowjoint.Weconsideredthistobetype I(Fig.3).

TypeIIwasrecordedintwolimbs.Thenervefascicles orig-inatedfromtheanteriorinterosseousnerve,justlikeintype I,withbifurcationofthefascicles,whichcommunicatedwith theulnarnerveattwodifferentpoints(Fig.4).

Median nerve

Ulnar nerve

Anterior interosseous nerve

Fig.3–TypeI.Thiswasthemostfrequentformof communication(seeninninelimbs).Thenervefascicles originatedfromtheanteriorinterosseousnerveand headedtowardtheulnarnerve.

Type V, which was also observed in five forearms, dif-fered from the preceding type in that the communication between the fascicles coming from the median and ulnar nervesoccurred insidethemusclemassofthedeepflexors ofthefingers.ThiswascalledintramuscularMartin-Gruber communication(Fig.7).

IntypeVI,whichwasrecordedintwoforearms,the fasci-clesoriginatedfromthebranchofthemediannervetoward thesuperficialflexormuscleandheadedobliquelyanddistally tocommunicatewiththeulnarnerve(Fig.8).

Segmentsoftheanastomoticramusoflength0.5–1.0cm wereremoved.Thenumberoffascicleswascountedundera surgicalmicroscope,atmagnificationsrangingfrom10to16×.

Withtheaidofmicrosurgicaltweezers,the fasciclesofthe anastomoticramuswereseparated.Infourlimbs,werecorded onlyonefascicle;ineight,two;innine,three;infour,four;in one,five;andinone,seven(Fig.9).

Discussion

Theincidenceofnervecommunicationbetweenthemedian andulnarnervesintheforearmisvariableandthisbecomes more marked when the results obtained through elec-troneuromyographicstudies arecomparedwiththose from anatomicaldissections.Table1showstheauthors,thenature ofthestudy,thenumberofcasesandthepercentageofnerve communication.

Ulnar nerve

Median nerve

Anterior interosseous nerve

Fig.4–IntypeII,whichwasrecordedintwolimbs,the nervefasciclesoriginatedfromtheanteriorinterosseous nerve,withbifurcation,andcommunicatedwiththeulnar limbattwodifferentpoints.

To the best of our knowledge, no anatomical studies regarding the innervation of the opposing muscle of the thumbthroughtheulnarnervehavebeenconducted. How-ever,throughelectromyographicstudies,itwasrecordedby Sala6_{in32%ofthecases,byForrest}2_{in20%,byHarnessand} Sequeles7_{in77%,byHighet}1_{in20%andbyRosen}8_in16.7%.In comparingthestudiesofSala6_andForrest,2_{inwhichexactly} thesametechniquewasusedyetcompletelydifferentresults wereachieved(Sala6_{77%andForrest}2_{20%),itcanbeseenthat} intheopinionofForrest,2_{thisoccurredbecausetheauthors} placedelectrodesatdifferentdepthsandbecauseSala6_placed electrodesincontactwiththemusclefibersoftheshortflexor muscle, thereby obtaininga higherpercentage. This differ-encedemonstratesthatstudiesconductedthroughelectrical stimulation are notasprecise asthose conductedthrough anatomicaldissection.

Median nerve

Anterior interosseous nerve

Ulnar nerve

Fig.5–IntypeIII,whichwasrecordedinfourlimbs,the fasciclesoriginatedfromthemediannerve,proximaltothe emergenceoftheanteriorinterosseousnerve,andheaded towardtheulnarnerve.

themediannerveclosetotheulnarnerve,inthedistalthird oftheforearm.Thisanatomicalformathassofarnotbeen recorded in the literature.It isprobably anextremely rare anatomicalvariation,oravariationofgroupIIofourfindings,

Median nerve

Ulnar nerve

Anterior interosseous nerve

Deep flexor muscle of the fingers

Fig.6–IngroupIV,whichwasrecordedinfivelimbs,

communicationoccurredbetweennervefasciclesthatwere

headingforthedeepflexormuscleofthefingers,andthe fasciclesformedaloopwithdistalconvexity.

inwhichunionwiththeulnarnervewouldoccurinthedistal thirdoftheforearm.

Theclassificationdrawn upbySrinivasan andRhodes12 is theone thatcomes closestto ourobservations. We dis-agreewith itonlyin relationtotwopoints. These authors consideredtypeItobecommunicationsthatoriginatedinthe proximalportionoftheanteriorinterosseousnerveandgroup

Table1–Summaryoftheliteratureinvolvingtheincidenceofanastomosisbetweenthemedianandulnarnerves (Martin-Gruberanastomosis),accordingtoauthor.

Year Authors Study Casesstudied Casesthatpresented Martin-Gruber anastomosis(%)

1870 Gruber4 _{Anatomical 250 15.2}

1893 Thomson9 _{Anatomical 406 15.5}

1931 Hirasawa10 _{Anatomical Nodata 10.5}

1976 Kimuraetal.11 _{Electrophysiological 328 17}

1981 SrinivasanandRhodes12 _{Anatomical,genetic 200 15}

1992 UchidaandSugioka13 _{Electrophysiological 47(cubitalsyndrome) 17}

87(normal) 16

1992 Amoiridis26 _{Electrophysiological 100 32}

1993 Nakashima14 _{Anatomical 108 21.3}

1999 Shuetal.16 _{Anatomical,histological 72 23.6}

2002 Rodriguez-Niedenfuhretal.17 _{Anatomical 140 13.6}

236 13.1

2005 Leeetal.18 _{Anatomical,electrophysiological 102(anatomical) 39.2}

224(electrophysiological) 23.2

Median nerve

Ulnar nerve

Anterior interosseous nerve

Intramuscular anastomosis

Fig.7–IntypeV,whichwasrecordedinfivelimbs,nerve

communicationoccurredinsidethemusclemassofthe

deepflexorsofthefingers(intramuscularanastomosis).

IItobethoseoriginatinginthedistalportionofthisnerve.We observedthatnervecommunicationcouldoriginateat differ-entlevelsoftheanteriorinterosseousnerve,butwedidnot seeanyreasontoconsiderthemtobedifferentgroups,since theyoriginatedinthesamenerveandhadthesameformat. Theotherpointofdisagreementisthattheseauthorsdidnot describeanyoccurrenceofintramuscularanastomosis.

It is still not possible to identify the origin and desti-nationofeachnerve fascicle,eitherbyelectrophysiological or by anatomical means. Anatomical studies are based on the apparent path the fascicles are following, from one nerve to another. In agreement with the majority of authors,4,5,9,10,12,14–17 _{wecanaffirmthatwedidnotobserve} anypassageofmotorfasciclesfromthe ulnarnervetothe median nerve, in any of the limbs. We recorded that the communicationsweredirectedfromthemediannervetothe ulnar.However,nervesarecomposedofmotorfascicles (effer-ent)andsensory fascicles(afferent).Itisthereforepossible thatsensoryfascicles(afferent)aredirectedfrom theulnar tothemediannerve.IngroupIII,itislikelythatin commu-nicationsoriginatinginthemediannerve(whichisamixed nerve),therearebothefferent(motor)andafferent(sensory) fascicles.Intheotherlimbs,communicationwasbymeansof amotornerve:anteriorinterosseousintypesI,II,IVorV;or bymeansofabranchofthemediannervetothesuperficial flexormuscleintypeVI.Inthissituation,itisunlikelythat sensoryfascicleswillexist.

Shaficetal.19_{reportedthecaseofapatientwhopresented} allofthesymptomsofcarpaltunnelsyndrome,buthad neg-ativeresultsfromprovocativetestssuchasTinel’ssignand

Median nerve

Ulnar nerve Superficial

flexor muscle

Anastomose

Fig.8–IntypeVI,whichwasrecordedintwolimbs, fasciclescomingfromthebranchofthemediannerveto thesuperficialflexormuscleheadedtoward

communicationwiththeulnarnerve.

Phalen’s test.Thispatient presentedevidentsigns ofulnar nerve compression in the elbow. Nerve stimulation in the epitrochlear-olecranongroovetriggeredthetypicalsymptoms ofcarpaltunnelsyndrome,whichdemonstratedthattransfer ofsensorynervefascicles(afferent)fromtheulnarnerveto themediannerveexisted.

Marinacci20_{describedthecaseofapatientwhosuffered} traumatic sectioningof the median nerve in the proximal forearm.Anelectromyographicevaluationshowed denerva-tion ofthelong flexormusclesofthethumb andthe deep flexoroftheindexandmiddlefingers,whichareusually inner-vatedbythemediannerve.However,thehanddidnotpresent motoralterationsseeneitherclinicallyor electromyographi-cally.Fromapplyingelectromyographicstimuliandfromthe velocityofmotorconductionofthemediannervesinthewrist andelbow,itwasconcludedthatthisalterationoccurredasa consequenceofpassageofnervefibersfromtheulnarnerve tothemediannerveintheforearm,distallytotheinnervation ofthelongflexorofthethumbandthedeepflexoroftheindex andmiddlefingers.Theauthornamedthistypeofinnervation ofalloftheintrinsicmusclesbytheulnarnerve“totalulnar hand”.Amongourresults,werecordedonelimbwithfiveand anotherwithsevenfascicles,butwecannotaffirmthatthese fascicleswouldbesufficienttoinnervatealloftheintrinsic musclesofthehand.

Fig.9–Distributionofthenumberoffasciclesinthe27recordsofMartin-Gruberanastomosis.Infourlimbs,weonly recordedonefascicle;ineight,two;innine,three;infour,four;inone,five;andinone,seven.

werefoundtobeinnervatedandsensitivitywaspreserved, despitecompleteruptureoftheulnarnerve.Thisauthoralso describedanothercaseinwhichtherewascompleterupture ofthemediannerveandalltheintrinsicmuscleswerefound tobefunctioning,despitetheabsenceofsensitivityinthearea ofinnervationofthemediannerve.Inthefirstsituation,all theintrinsicmusclesreceivedinnervationfromthemedian nerveandinthesecond,fromtheulnarnerve.These varia-tionswereattributedtoMartin-Gruberanastomosis.Basedon ourstudies,22_{itismorelikelythatthesevariationsoccurred} becauseofCannieu-Richéanastomosis(communicationfrom motorbranchesofthemediannervetothemuscles ofthe

thenarregionandthedeepbranchoftheulnarnerve,inthe palmofthehand),becausethiscommunicationisthreetimes morefrequentthanMartin-Gruberanastomosis.

nerves.

Year Authors Classificationproposed;anastomosisbetweenthemedianandulnarnerves

1893 Thomson9 _{ClassI:anteriorinterosseousnerveandulnarnerve}

ClassII:mediannerveandulnarnerve

ClassIII:musclebranchtodeepflexormuscleofthefingers

1931 Hirasawa10 _{Obliqueanastomosis:anteriorinterosseousnerveandulnarnerve}

mediannerveandulnarnerve

Loopanastomosis:musclebranchtodeepflexormuscleofthefingers Combinedanastomosis:combinationsbetweenothers

1976 Kimuraetal.11 _{TypeI:mediannerveandulnarnerveinnervatingthehypothenarmuscle}

TypeII:mediannerveandulnarnerveinnervatingthedeepflexormuscleofthefingers TypeIII:mediannerveandulnarnerveinnervatingthethenarmuscle

1981 SrinivasanandRhodes12 _{TypesI,II,VI:anteriorinterosseousnerveandulnarnerveorother}

TypeIII:mediannerveandulnarnerve TypesIV,V:combinationsofothers

1992 UchidaandSugioka13 _{TypeI:mediannerveandulnarnerveinnervatingthehypothenarmuscle}

TypeII:mediannerveandulnarnerveinnervatingthethenarmuscle

TypeIII:mediannerveandulnarnerveinnervatingthedeepflexormuscleofthefingers

1993 Nakashima14 _{TypeIa:anteriorinterosseousnerveandulnarnerve}

TypeIb:mediannerveandulnarnerve TypeIII:combinationoftypesIa,IbandII

1995 Ohetal.15 _{TypeI:mediannerveandulnarnerveinnervatingthehypothenarmuscle}

TypeII:mediannerveandulnarnerveinnervatingthedeepflexormuscleofthefingers TypeIII:mediannerveandulnarnerveinnervatingthethenarmuscle

1999 Shuetal.16 _{TypeI:anteriorinterosseousnerveandulnarnerve}

TypeII:mediannerveandulnarnerve

TypeIII:musclebranchtodeepflexormuscleofthefingers

TypeIV:anteriorinterosseousnerveandulnarnerve,musclebranchtodeepflexor muscleofthefingersoriginatingfromtheconnection

TypeV:twoanastomoticbranches

2002 Rodriguez-Niedenfuhr

etal.17

PatternI:oneanastomoticramus PatternII:twoanastomoticrami

TypeA:anastomoticramusoriginatingfromabranchofthemediannervetothenerve ofthesuperficialflexormuscleoftheforearm

TypeB:anastomoticramusoriginatingfromthemediannerve

TypeC:anastomoticramusoriginatingfromtheanteriorinterosseousnerve

2005 Leeetal.18 _{TypeI:anteriorinterosseousnerveandulnarnerve}

TypeII:mediannerveandulnarnerve

TypeIII:musclebranchtodeepflexormuscleofthefingers

TypeIV:twoanastomoticramifromtheulnarnerveoranteriorinterosseousnerveand ulnarnerve

2015 Ourclassification TypeI:anteriorinterosseousnerveandulnarnerve

TypeII:anteriorinterosseousnerveandulnarnerve(doubleanastomosis) TypeIII:mediannerveandulnarnerve

TypeIV:loopbetweenanteriorinterosseousnerveandulnarnervewithbranchesto deepflexormuscleofthefingers

TypeV:intramuscularanastomosis

TypeVI:branchfromthemediannervetothesuperficialflexormuscleandulnarnerve

forearmorinthepalmofthehand.Itismorelikelythatthis wasCannieu-Richéanastomosis,becausethisisthreetimes morefrequentthanMartin-Gruberanastomosis.

Brandsmaetal.24_{describedtwoclinicalcasesofpatients} withcomplete ruptureoftheulnarnerveintheelbowand injurytothemediannerveinthe wrist,secondaryto neu-ropathyduetoleprosy,whichmaintainedgoodfunctioningof thefirstdorsalinterosseousmusclesandtheshortflexorof thethumb.Theyattributedthesefindingstothepresenceof Martin-Gruberanastomosis.Ourresultscontributesupportto

thisclinicalobservationthatthisoccurrencecouldonlyhave beenduetoMartin-Gruberanastomosis.

notrecordanynervecommunicationfromthemediantothe ulnarnerve.Theseresultsaresurprising,becausethey com-pletelydisagreewiththoseintheliterature,consideringthat theyshowulnar–mediananastomosisasbeingmorefrequent thanmedian–ulnar.

Amoiridis26 _{reported being surprised about the results} publishedbyGolovchinsky,27_{whofoundthatnerve} communi-cationfromtheulnarnervetothemediannervewaspresent in16.7%.ThisauthorstatedthatGolovchinsky27_hadnottaken intoconsiderationsomebasicprinciplesof electrophysiologi-calstudiesandthatthiswaswhythepercentageofthistype ofnervecommunicationwassohigh.Inaddition,thisauthor statedthatGolovchinsky27_{hadnottakenintoconsideration} thataresponsefromtheelbowtothewristdiminishedbyup to15%couldbefoundeveninnormalindividuals.

Komaret al.28 _{reportedthe caseofapatientwith} com-pleterupture ofthemediannerve abovetheelbow, witha conditionofincompleteparalysisofthemediannerveinthe handandlossofsensitivityintheareaofsensoryinnervation bythemedian nerve.They reportedthat their electromyo-graphicevaluationsuggestedthatnervefibertransferfromthe ulnarnervetothemediannerveintheforearmwaspresent. AmoiridisstatedthatthiscasedescribedbyKomarwasnot oneofnervecommunicationintheforearm,since stimula-tioninthewristdidnotshowaresponsefromthemusclesin thethenarregion.WeagreewithAmoiridis,sinceitislikely thattransferoffasciclesfromtheulnartothemediannerve occurreddistallytothewrist(Cannieu-Richéanastomosis).

Streib29_{reportedthecaseofa77-year-oldpatientwitha} complaintofweakness inthehands.Electricalstimulation demonstrated thatthe response ofthemusculature ofthe thenarregionhadanamplitudegreaterthan50%whenthe mediannervewasstimulatedinthewrist,inrelationtothe elbow.Theoppositeoccurredinrelationtotheulnarnerve, i.e.theamplitudewas50%greaterintheelbow.Thereisno doubtthatinthiscase,nervecommunicationoccurredinthe forearm(Martin-Gruberanastomosis).

Doganetal.30_{describedthecaseofapatientwitha} con-dition of compressive neuropathy ofthe ulnar nerve who presentedalteredsensitivityintheringfingerandlittlefinger, butwithatrophyoftheshortabductormuscleofthethumb. Theyattributedthisfindingtoananomalyofinnervationof theshortabductor.

ThemainclassicaltreatisesdescribeMartin-Gruber anas-tomosisasnervecommunicationintheforearmbetweenthe medianandulnarnerves,butdonotmentioneithertheorigin orthedestinationofthenervefibers.

Conclusion

Knowledge of the anatomical variations relating to inner-vationofthehand isparticularlyimportantwithregard to performingphysicalexaminations,makingdiagnoses, deter-miningtheprognosisandimplementingsurgicaltreatment. Ifthesevariationsarenotgiventheirpropervalue,errorsand consequenceswillbeinevitable.

Nerve communications between the median and ulnar nerves may cause alterations to clinical symptoms, espe-ciallyinpatientswithcarpal tunnelsyndrome,sincethese

variations mayexacerbate orattenuatethe symptoms and cause motor and sensory alterations that differ from the usualpattern.Clinically,variationsinmotorinnervationare very important, inthat evenwithcomplete rupture ofthe medianorulnarnerve,someofthesemusclesmaynot nec-essarilybecomeparalyzed.Suchsituationscouldleadtothe wrongconclusionthatthenervehadnotbecomecompletely severed. Itis essentialto differentiatebetween partialand totalrupture.However,correctidentificationofthesevariables is notalways easy, sincerigorous clinical and electromyo-graphicexaminationisneeded. Alterationsrecorded inthe electroneuromyographicexaminationwithoutclinical proof areinsufficientforindicatingasurgicalprocedure.Careful dis-sectionduringthesurgicalproceduremaypreventinjurytoan anastomoticramus.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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