SOCIEDADE BRASILEIRA DE ORTOPEDIA E TRAUMATOLOGIA
w w w . r b o . o r g . b r
Original
Article
The
arcade
of
Struthers:
an
anatomical
study
and
clinical
implications
夽
Edie
Benedito
Caetano
a,∗,
João
José
Sabongi
Neto
b,
Luiz
Angelo
Vieira
a,
Maurício
Ferreira
Caetano
baPontifíciaUniversidadeCatólicadeSãoPaulo,FaculdadedeCiênciasMédicasedaSaúde,DepartamentodeCirurgia,Sorocaba,SP,
Brazil
bConjuntoHospitalardeSorocaba,Servic¸odeCirurgiadeMão,Sorocaba,SP,Brazil
a
r
t
i
c
l
e
i
n
f
o
Articlehistory:
Received1July2016 Accepted12July2016 Availableonline9May2017
Keywords:
Arm/anatomy&histology Cadaver
Ulnarnerve
a
b
s
t
r
a
c
t
Objective:TodeterminethefrequencyandfeaturesofthearcadeofStruthers,andtoassess itsclinicalimplicationinulnarnervecompression.
Method:Fortyarmsfrom26cadaverspecimensweredissectedintheAnatomyLaboratory ofthisinstitution.Theextensionofthearcade,distancefromthemedialepicondyle,and relationwithulnarnervewererecorded.
Results:ThearcadeofStrutherswasidentifiedin40dissectedarms(100%).In29(72.5%)the ulnarnervewascoveredbyamusculararcade,innine(22.5%)byanaponeuroticarcade, andintwo(5%)thearcadewasbeneaththeulnarnerve.Theextensionofthearcaderanged from3.0to7.5cm,andthedistancefromthemedialepicondylerangedfrom2.5to7.0cm.
Conclusion: ThearcadeofStruthersisamusculoaponeuroticcanalthatrepresentsan impor-tantsiteofentrapmentorcompressionoftheulnarnerve.Thearcade,theintermuscular septum,andtheinternalbrachialligamentshouldbereleasedinpatientssubmittedtoulnar nerveanteriortranspositionsurgery.
©2017PublishedbyElsevierEditoraLtda.onbehalfofSociedadeBrasileiradeOrtopedia eTraumatologia.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http:// creativecommons.org/licenses/by-nc-nd/4.0/).
Arcada
de
Struthers:
estudo
anatômico
e
implicac¸ões
clínicas
Palavras-chave:
Brac¸o/anatomia&histologia Cadáver
Nervoulnar
r
e
s
u
m
o
Objetivo:DeterminarafrequênciaeascaracterísticasanatômicasdaarcadadeStrutherse avaliarsuaimplicac¸ãoclínicananeuropatiacompressivadonervoulnar.
Método:Paraestetrabalhoforamdissecados40membrosde26cadáveres,pertencentesà disciplinadeanatomiadainstituic¸ão.Aextensãodaarcada,adistânciadamargeminferior daarcadaaoepicôndilomedialdoúmeroesuarelac¸ãocomonervoulnarforamregistradas.
夽
StudyconductedatthePontifíciaUniversidadeCatólicadeSãoPaulo,FaculdadedeCiênciasMédicasedaSaúde,Departamentode Cirurgia,Sorocaba,SP,Brazil.
∗ Correspondingauthor.
E-mail:[email protected](E.B.Caetano). http://dx.doi.org/10.1016/j.rboe.2016.07.006
Resultados:AarcadadeStruthersfoiidentificadanos40membrosdissecados(100%),Emdois membros(5%),onervoulnarpassavaanteriormenteàarcada.Em29(72,5%),umaporc¸ão variáveldomúsculotrícepscobriaonervoulnar.Emnovemembros(22,5%),onervoestava cobertopelaexpansãoaponeuróticadotríceps.Aextensãodaarcadavarioude3,0a7,5cm eadistânciadamargeminferiordaarcadaaoepicôndilomedialvarioude2,5a7,0cm.
Conclusão: AarcadadeStrutherséumcanalmusculoaponeuróticoquerepresenta impor-tantelocal(potencial)decompressãodonervoulnar.Aarcada,oseptointermuscularmedial eoligamentobraquialinterno devemserseccionadosnosprocedimentoscirúrgicosde transposic¸ãoanteriordonervoulnarnocotovelo.
©2017PublicadoporElsevierEditoraLtda.emnomedeSociedadeBrasileirade OrtopediaeTraumatologia.Este ´eumartigoOpenAccesssobumalicenc¸aCCBY-NC-ND (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction
TheStruthers’ligamentandthearcadeofStruthersaretwo anatomicalstructuresthatareoftenconfused.TheStruthers’ ligamentwasdescribedbyanatomistJohnStruthers1in1854; itisafibrousbandthatextendsfromabonespurlocatedon theanteromedialsurfaceofthelowerthirdofthehumerus, knownasthe supracondylarprocess,andisinsertedinthe medialhumeralepicondyle.TheStruthers’ligamentpasses over themediannerve and thebrachial artery, whichmay cause compressionofthesestructures. Itmay beobserved evenintheabsenceofthesupracondylarprocess;evenwhen present,itmaynotcausethecompressionofthesestructures. Thesupracondylarprocessofthehumerushasbeendescribed byanatomistsandanthropologists;itisphylogenetically con-sideredasavestigeofthesupracondylarforamen,foundin reptiles,marsupials,andsomemammals.2–4Itsoccurrencein humansisvery rare,beingobservedin0.7%to2.5%ofthe population.2,5 However,thereisnodispute astothe exist-enceofthisligament.Incontrast,thearcadeofStrutherswas firstdescribedin1973byKaneetal.6Itissometimesdefined asathickeningofthebrachialfascia,andsometimesasan aponeuroticormusculoaponeuroticstructureextendingfrom themedialintermuscularseptatothemedialheadofthe tri-cepsbrachiimuscleatavariabledistanceabovethemedial humeralepicondyle.
ThearcadeofStrutherscancausecompressionoftheulnar nerve.Controversyexistsintheliteratureregardingthe exist-enceofthearcadeofStruthers.Someanatomicalstudieshave foundananatomical formationconsistent withthearcade ofStruthers.Conversely,otherstudieshavereportedthatthe arcadeofStruthersdoesnotexist;rather,thatthereareonly anatomicalvariationsoftheintermuscularseptumandthe forearmfascia.7–9
Thisstudyaimedtoanalyzetheanatomicalstructuresthat relatetotheulnarnerveinthemedialaspectofthearm,such asthebrachialfascia,themedialintermuscularseptum,the internalbrachialligament,andthemedialheadofthetriceps brachiimuscle,andtoassessthe possibilityofthese struc-turesbeingresponsibleforthecompressivesyndromeofthe ulnarnerveorevenwhethertheycaninterfereaftersurgical proceduresofanteriortranspositionoftheulnarnerveatthe elbow.
Material
and
methods
40 armsof 26 adultcadavers ofthe Anatomy Department ofthisinstitutionweredissected;14bilateral(preparedwith formalinsolutionandglycerin),and12onlytherightupper limb(dissectedfromfreshcadavers).Ofthecorpses,22were maleandfourwerefemale,15werewhiteand11were non-white.Cadaverswhoseforearmsweredeformedbytraumas, malformations,andscarswereexcluded.Thedissectionwas performedthroughanincisionintheanteromedialaspectof thearm(fromtheaxillatothemiddlethirdoftheforearm.Two flapsthatincludedtheskinandthesubcutaneoustissuewere pulledaway,exposingtheentiremedialsurfaceofthearm. Thebrachialfascia,basilichiatus,basilicvein,andthemedial cutaneousnerveoftheforearmwereidentified.Thebrachial fasciawasincisedlongitudinallyinthemedialmarginofthe tricepsbrachiimuscleinthesamemannerthattheskinwas folded,oneanteriorflapandoneposteriorflap(Fig.1).The ulnarnervewasidentifiedintheaxillaryregionanddissected distallytothemedialintermuscularseptum,whichitcrosses, passingfromtheanteriortotheposteriorcompartmentofthe arm.Inthislocation,theinternalbrachialligamentcanalsobe identified.Then,theulnarnervewasidentifieddistallyinthe
Brachial fascia
Brachial fascia
Ulnar n.
Triceps m.
Arcade of struthers
Fig.1–Thebrachialfasciawasincisedlongitudinallyinthe medialmarginofthetricepsbrachiimuscleandinthe
samewayinwhichtheskinwasfolded,withananterior
Ulnar n.
Arcade of struthers
Triceps m. (long head)
Fig.2–Stillbornarmdissectedasapilot,showingthe ulnarnervesurroundedbythemedialheadofthetriceps.
epicondilar-olecranongrooveanddissectedproximallyuntil itwascoveredbythemedialheadofthetricepsbrachii mus-cleorbyitsaponeurosis(whichcorrespondstothedistaledge ofthearcadeofStruthers).Thedistancefromthearcadeto themedialepicondyleandthelengthofthearcadewere mea-sured.Fourlimbsoftwostillbornsweredissectedasapilot forfamiliarizationwiththestructuresofthemedialaspectof thearm,andwerenotincludedinthisstudy(Fig.2).AKeller brand2.5Xmagnifyingglasswasusedformagnification.This studywasapprovedbytheResearchEthicsCommitteeofthe institutionunderthenumber1.558.501.
Results
Inthisstudy,thearcadeofStrutherswasdefinedasafibrous canalonthemedialaspectofthemiddle-andlower-thirdof thearm,consistingofthemedialheadofthetricepsbrachii muscleanditsaponeuroticexpansion,whichextendsintothe intermuscularseptumandinternalbrachialligamentand cov-erspartoftheulnarnerve(Fig.3).ThearcadeofStrutherswas identifiedin40limbs(100%).Intwolimbs(5%),theulnarnerve passedanteriorlytothearcade(Fig.4).In29limbs(72.5%),a
Ulnar n.
Triceps m. Arcade of
struthers Internal
brachial ligament
Medial intermuscular septum
Fig.3–Intwolimbs(5%),thearcadeofStruthers,
consistingofthetricepsbrachiimuscle,extendedintothe intermuscularseptum.Itpassedposteriorlytotheulnar nerve.
Ulnar n.
Triceps m. Arcade of
struthers Medial intermuscular septum
Fig.4–Inninelimbs(22.5%),thenervewascoveredbya fibrouscanal(arcadeofStruthers)consistingofthe
aponeuroticexpansionofthetriceps,whichextendedinto
theintermuscularseptumandcoveredpartoftheulnar nerve.
variableportionofthetricepsmusclecoveredtheulnarnerve (Figs.1and3),andinninelimbs(22.5%)thenervewascovered bytheaponeuroticexpansionofthetricepsbrachii(Fig.5). Thelengthofthearcaderangedfrom3.0to7.5cmandthe dis-tancefromlowerlimitofthearcadetothemedialepicondyle ranged from 2.5 to 7.0cm. The internal brachial ligament (Fig.6)wasobservedin26limbs(65%),oftenoriginating prox-imallyintheintermuscularseptumandattachedtoitnearthe medialepicondyle.Theauthorsbelievethat,inmostcases,it representsanunfoldingoftheintermuscularseptum(Fig.6). Theintermuscularseptumdividesthearmintoanteriorand posterior compartments. The ulnar nerve passes from the anteriortotheposteriorcompartmentattheopeningofthe Struthers arcade.In four limbs(10%), it wasobserved that the arcade’s entrance (proximally) consistedofa V-shaped
channelbetweenthemedialintermuscularseptumandthe internal brachial ligament (Fig. 7). When tractioning the nerveproximallyanddistally,itwasobservedthatitmoved
Triceps m. Ulnar n. Internal brachial
ligament
Intermuscular septum Ulnar n.
Fig.5–Theinternalbrachialligamentrecordedin26limbs (65%),oftenoriginatingproximallyintheintermuscular
Ulnar n.
Ulnar n.
Arcade of struthers
Internal
brachial
ligament
Medial intermuscular septum
Fig.6–Theulnarnervepassesfromtheanteriortothe posteriorcompartmentattheopeningofthearcadeof Struthers.Infourlimbs(10%),itwasobservedthatthe entrance(proximal)ofthearcadeconsistedofaV-shaped
canalbetweenthemedialintermuscularseptumandthe
internalbrachialligament.
easilywithinthearch,whichwassectionedattheendofthe dissection, and it was not possible to identify any points within it that showed any signs of nerve compression. In two limbs, an additional fibrous band was identified near the medial epicondyle (Fig. 8). In one limb, an accessory portionofthemedialtricepsheadthatwasinsertedintothe intermuscularseptumwasidentified;anotherlimbpresented theanconeusepitrochlearismuscle(Fig.9).
Discussion
Theliteraturereviewindicatesthatthe arcadeofStruthers is still acontroversial structure. Some authors confirm its existence,10–13 whileotherpublications donotconsiderthe arcade to be a compression site, proposing that the term arcadeofStruthers should beabandoned.8,14 De Jesusand Dellon15statethatStruthersneverdescribedthisanatomical structure.Themainclassicaltreatisesoftheliteraturedonot considerthearcadeofStruthers.16,17
Ulnar n. Arcade of
struthers
Internal brachial
ligament Triceps fibrousband
Fig.7–Intwolimbs,anadditionalfibrousbandwas identifiednearthemedialepicondyle.
Ulnar n.
Epitroclear anconeid muscle
Arcade of struthers Intermuscular
septum
(a)
(b)
Fig.8–Inonelimb,thepresenceofepitrochlearanconeus musclewasobserved.Medialepicondyle(a).Olecranon(b).
TheconceptofarcadeofStrutherswascreated byKane et al.6in1973.Thoseauthors identifiedthearcadein14of 20 dissectedlimbs(70%). AlQattanand Murray10 observed similar results,identifying the arcadeofStruthers in17of 25freshcadavers(68%).Theseauthorsdescribedthearcade similarlytoKaneetal.,9 butreportedthatinfivelimbsthe internalbrachialligamentwasrepresentedbymultiple liga-ments.WehrliandOberlin9observedthepresenceofmultiple ligaments,which passedover the ulnarnerve, insix of30 dissected limbs. Amadio and Bekenbaugh18 confirmed the findingsofKaneetal.6;afterdissecting20limbsfromcorpses, theyfoundthearcadeofStruthersasdescribedbyKaneetal.6 inallofthem(100%;6to10cmproximaltothemedial epi-condyle,1.5to2cmwide).Gonzalezetal.12reportedthearcade ofStruthersin26outof39dissectedarms(67%),locatedon average 8.2cm proximaltothe medialepicondyle.Siqueira and Martins7 observedthe arcade in eightof 60 dissected limbs(13.5%),withamean3.75cmthickness,locatedon aver-age6.82cmproximaltothemedialepicondyle.Barteletal.8 did not identify brachial fascia thickening when assessing tenlimbs.Dellon14dissected104armsfrom64corpsesand observedthatthebandthatcouldbeidentifiedasthearcade ofStrutherswasnotfound,andthatinmorethan300
proce-Ulnar n. Ulnar n.
Medial intermuscular septum Internal brachial ligament
Fig.9–ArcadeofStruthers:afibrouscanalconsistingof themedialheadofthetricepsbrachiimuscleandits
aponeuroticexpansion,whichextendedintothe
intermuscularseptum.Theinternalbrachialligament
Ulnar n.
Ulnar n.
Arcade of
struthers
Arcade of
struthers
Septum
(a)
(a)
Intermuscular
septum
A
B
Fig.10–ThearcadeofStruthersmayberesponsibleforrecurrenceofcompressiveneuropathyoftheulnarnerveafter anteriortranspositionofthenerveattheelbow.(A)Nerveinthesulcusbetweentheolecranonandmedialepicondyle.(B) Postanteriortransposition.
duresontheulnarcanalnever,itwasnotpossibletoidentify anystructureinthisregionthatcouldcauseitscompression. However,in16limbs(25%),theulnarnervewaspartiallyor totally covered bythe medialtriceps head. Von Schroeder andScheker19reportedthatthearcadeofStruthersandthe intermuscular septum were identifiedin 11 (100%) corpses dissected.Itconsistedofaosteofibrouschannel,narrowerin itsproximalopening,whichisaclinicallyrelevantlocation thatcanbethecauseofcompressiveneuropathyoftheulnar nerve;thisisafiberchannelmeasuring5to7cm,comprising the intermuscular septum, the internal brachial ligament, andthetricepsmuscleanditsfascia.Thoseauthorsdescribed thattheproximalarcadeiscomposedofacanalbetweenthe intermuscular septum and the internal brachial ligament, whichisconsideredtobethenarrowestsiteofthearcade.
Thediscrepancyintheresultscanbeattributedtothe def-initionofarcadeofStruthers.Thedefinitionadoptedinthe presentstudyisclosetothatdescribedbyVonSchoederand Scheker.19ThearcadeofStrutherswasdefinedasafibrous canalonthemedialsideofthemiddle-andlower-thirdofthe armformedbyanexpansionofthemedialheadofthetriceps muscleanditsaponeuroticexpansion,whichextendstothe intermuscularseptumandtheinternalbrachialligamentand coverspartoftheulnarnerve.ThearcadeofStrutherswas observedin40limbs(100%);in29(72.5%),avariableportionof thetricepsmusclecoveredtheulnarnerve(Figs.1and3).In two(5%),theulnarnervewaspositionedanteriorlytothearch (Fig.4).Inninelimbs(22.5%),theulnarnervewascoveredby theaponeuroticexpansionofthetriceps(Fig.5).Thelength ofthearcaderangedfrom3to7.5cmandthedistancefrom thelowerlimitofthearcadetothemedialepicondyleranged from2.5to7cm.Thepresenceofmultipleligamentswasnot observedinthedissectedlimbs.
Wehrli and Oberlin9 report that, in 1854, Struthers described the intermuscular septum and coined the term internalbrachialligament,describedasawhitishfibrousband
positionedposteriorlytotheintermuscularseptum,merging toitnearthemedialepicondyle;thisligament was consid-eredtobeindependentoftheintermuscularseptum.Wehrli andOberlin9recordedtheexistenceofthisligamentin22of 30dissectedarms(73%),butdisagreewithStruthers,asthey considerthisligamenttobeanunfoldingoftheintermuscular septum.Inthepresentstudy,theinternalbrachialligament wasobservedin26limbs(65%);asWehrliandOberlin,9 the authorsbelievethatitrepresentsanunfoldingofthe inter-muscularseptum.Theintermuscularseptumdividesthearm into anteriorand posteriorcompartments.Theulnar nerve passesfromtheanteriortotheposteriorcompartmentatthe openingoftheStruthersarcade.Infourlimbs(10%),itwas observedthattheentrance(proximal)ofthearcadeconsisted ofaV-shapedcanalbetweenthemedialintermuscularseptum andtheinternalbrachialligament(Fig.7),aswasobservedby VonSchoererandScheker.19
When pulling the nerve proximally and distally, it was observed thatit movedeasilywithinthe arcade; thesame observationwas madebyVonSchoerer andScheker.19 The arcade was sectioned atthe end of the dissection and no points within it that showed any signs of nerve compres-sion wereobserved. However,the authors believethat this structuremayberesponsiblefornervecompressioninlimbs wherethemedialheadofthetricepswaswelldevelopedand covered a largesegment ofthe nerve, as well as inlimbs wheretheentrance(proximal)ofthearcadeconsistedofa V-shapedcanalbetweenthemedialintermuscularseptumand theinternalbrachialligament.
distally and proximally to the medial epicondyle; it must betotallyreleased,untilitcanbeensuredthatnostructure couldcauserelapseofthenervouscompression.
Conclusion
The arcade ofStruthers may be the primary cause ofthe compressive ulnar nerve syndrome, but it may be mainly responsiblefortherecurrenceofcompressiveneuropathyof theulnarnerveaftertheanteriortranspositionofthenerve intheelbow;therefore,itisrecommendedtoresectthe struc-tures(thearcade,themedialintermuscularseptum,andthe internalbrachialligament)thatmaycompressthenerveafter thisprocedure.
Conflicts
of
interest
Theauthorsdeclarenoconflictsofinterest.
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1. StruthersJ.Onsomepointsintheabnormalanatomyofthe arm.BrForeignMedChirRev.1854;14:170–9.
2. TerryRJ.Onthesupracondyloidvariationsinthenegro.AmJ PhysAnthropol.1923;6:401–3.
3. TerryRJ.Ontheracialdistributionofthesupracondyloid variation.AmJPhysAnthropol.1930;14:459–62.
4. BarnardLB,McCoySM.Thesupracondyloidprocessofthe humerus.JBoneJointSurgAm.1946;28:845–50.
5. GuntherSF,DiPasqualeD,MartinR.Internalanatomyofthe mediannerveintheregionoftheelbow.JHandSurgAm. 1992;17:648–56.
6.KaneE,KaplanEB,SpinnerM.Observationsonthecourseof theulnarnerveinthearm.AnnChir.1973;27:487–96. 7.SiqueiraMG,MartinsRS.Thecontroversialarcadeof
Struthers.SurgNeurol.2005;64:17–21.
8.BartelsRHMA,GrotenhuisJA,KaverJMG.Thearcadeof Struthers:ananatomicalstudy.ActaNeurochir(Wien). 2003;145:295–300.
9.WehrliL,OberllinC.InternalbrachialligamentofStruthers vs.theso-calledarcadeofStruthers.JReconstrMicrosurg. 2004;20:340–1.
10.Al-QattanMM,MurrayKA.ThearcadeofStruthers:an anatomicalstudy.JHandSurgBr.1991;16:311–4.
11.CaputoAE,WatsonHK.Subcutaneoustranspositionofthe ulnarnerveforfaileddecompressionofcubitaltunnel syndrome.JHandSurgAm.2000;25:544–51.
12.GonzalesMH,LoftiP,BendreA,MandelbroytY,LieskaN.The ulnarnerveattheelbowanditslocalbranching:ananatomic study.JHandSurgBr.2001;26:142–4.
13.SpinnerM,KaplanEB.Therelationshipoftheulnarnerveto themedialintermuscularseptuminthearmanditsclinical significance.Hand.1976;8:239–42.
14.DellonAL.Musculotendinousvariationsaboutthemedial humeralepicondyle.JHandSurgBr.1986;11:175–81. 15.DeJesusR,DellonAL.Historicoriginofthearcadeof
Struthers.JHandSurgAm.2003;28:528–31.
16.TestutL.Lesanomaliesmusculaireschezl’hommer.Paris: Masson;1884.p.454–89.
17.LeDoubleAF.Traitédesvariationsdusystèmemusculairede l’hommeetdeleursignificationaupointdevuede
l’anthropologiezoologique.Paris:SchleicherFrères;1897.p. 99–107.
18.AmadioPC,BekenbaughRD.Entrapmentofulnarnerveby thedeepflexorpronatoraponeurosis.JHandSurgAm. 1986;1:83–7.
