18 Bulletin• Hospital for Joint Diseases Volume62,Numbers1&2 2004

Abstract

Plate fixation for unstable fractures of the proximal hu-merus has seen mixed results as evidenced by the trials of new methods of fixation. The deltopectoral surgical approach is most frequently used and requires significant muscle retraction and soft tissue stripping to expose the lateral humeral neck. This may contribute to avascular necrosis and fixation failure. Lateral approaches have been limited to 5 cm distal to the acromion because of the course of the anterior branch of the axillary nerve. A recent anatomic study has demonstrated the predict-ability of the position of the axillary nerve as it crosses the anterior deltoid raphe, which allows it to be isolated and protected, and dissection can be extended distally. In addition, no accessory motor branches to the anterior head of the deltoid cross the raphe, so extending an inci-sion through the raphe after protecting the main motor branch of the axillary does not place the innervation to the anterior deltoid at risk. This surgical approach allows exposure of the proximal humerus and indirect reduction of the fracture, with subsequent locking plate fixation, adhering to the principles of biological fixation.

With the advent of locking plates for fixationofproximalhumerusfractures,modificationofpreviouslydescribed surgical approaches

isessential.The traditionaldeltopectoralapproachfortheanteriorandlateralshoulderregionrequiresexten-sivesofttissuedissectionandmuscleretractiontogainadequateexposuretothelateralaspectofthehumerus

forapplicationofaplate.Poor results followingplatefixationofproximalhumerusfracturesmayberelatedtocompleteexposureofthefracturefragmentsanddevas-cularizationduringdissectionandplating,ordisruptionofthecriticalbloodsupplytothehumeralhead.Inlightoftherecenttrendtoward“biologicalfixation,”whichfocusesonfixed-anglescrews,percutaneousbridgeplat-ingtechniques,andavoidanceofbothfractureexposureandanatomicreduction,1newsurgicaltechniquesmustbedevelopedforproperapplicationofthesedevices. For access to rotator cuff tears using a mini-openapproach, a small raphe-splitting incision from theacromionseveralcentimetersdistallyhasbeenwellde-scribed.2-5However,distalextensionthroughtherapheofmore than3or4centimetershasbeendiscouragedbecauseoftheriskofdamagingtheaxillarynerve.Re-cently,ananatomicstudywasperformedtocharacterizethe axillary nerve as it crosses the raphe between themiddleandanteriorheadsofthedeltoid.6Theanteriormotorbranchoftheaxillarynervewasfoundtocrossthesurgicalneckatapredictablelocationrelativetoboththeacromionandthegreatertuberosity,andattheleveloftheraphenoothermotorbranchescrossedtoinnervatetheanteriorheadofthedeltoid(Fig.1).Thisdatamaybeusefulinallowingamoredirectsurgicalapproachtotheproximalhumerusforplatefixationoffractures.

Surgical TechniqueAskinincisionwasmadebeginningattheanterolateraltip of the acromion. It was extended approximately 5cmdistallythroughthesubcutaneoustissuelayertothelevelofthedeltoidmuscle(Fig.2A).Theavascularrapheseparatingtheanteriorandmiddleheadsofthedeltoidwasthenidentifiedasawhitebandofconnectivetissuebetweenthetwomuscularheads.Immediatelyadjacenttotheraphe’sattachmenttotheacromion,itwasincised

A Minimally Invasive Approach for Plate Fixation of the Proximal Humerus

Michael J. Gardner, M.D., Matthew H. Griffith, M.D., Joshua S. Dines, M.D., and Dean G. Lorich, M.D.

MichaelJ.Gardner,M.D.,MatthewH.Griffith,M.D.,JoshuaS.Dines,M.D.,andDeanG.Lorich,M.D.,areintheDepartmentofOrthopaedicSurgery,HospitalforSpecialSurgery,NewYork,NewYork.Correspondence:MichaelJ.Gardner,M.D.,HospitalforSpecialSurgery,535East70thStreet,NewYork,NewYork10021.

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sharplyfor2cmalongitslengthdistally,enoughtoal-lowtheinsertionofthesurgeon’sfinger.Thesurgeon’sfingerwastheninsertedintotherentintheraphesweptposteriorly to palpate undersurface of the deltoid andraphe. The axillary nerve was readily palpable as acord-likestructurebetweenthedeltoidandhumerusasitexitsthequadrangularspacewiththeposteriorhumeralcircumflexvessels. Onceageneralideaofthenerve’slocationwasobtained,theincisionintheraphewascarefullyextendeddistallybysharpdissection.Deeptotheraphe,approximately6.5cmdistaltotheinferioredgeoftheacromionand3.5cmfromthelateralprominenceofthegreatertuberosity,theaxil-larynerveandposteriorhumeralcircumflexvesselswereidentified,isolated,andprotectedwithavesselloop(Fig.

2B).Withtheneurovascularbundleprotected,theincisionmay be extended distally to the deltoid tuberosity.Thefracturemaybe indirectlyreducedusing ligamentotaxisandKirschnerwiresintheheadandshaftasjoysticks.Afixed-angleplatecanthenbeinsertedalongthelateralneckandshaftfromproximaltodistalunderneaththenerveandvesselswithoutexcessivetension(Fig.3).

DiscussionOperativefixationofproximalhumeralfracturesisin-dicatedinapproximately20%ofcases,themajorityofwhicharethree-andfour-partfracturesaccordingtotheNeerclassification.7Treatmentoptionsvaryfromclosedreductionwithpercutaneouspinningtohemiarthroplastyandtheappropriatemethoddependsonthefracturepat-

Figure 1Examplesofexposureoftheaxillarynerveandposteriorhumeralcircumflexvesselsastheytraversetheanteriordeltoidrapheofarightcadavershoulder.Nootherbranchescrosstheraphetoinnervatetheanteriorheadofthedeltoid.

A B

Figure 2Illustrationoftheextendedanterioracromialapproach.Theincisionbeginsfromtheanterolateralcorneroftheacromionandextendsdistally.Deeptothesubcutaneouslayer,theanteriordeltoidraphe,separatingtheanteriorandmiddleheadsofthedeltoid,isidentified(A).Afterpalpatingtheundersurfaceofthedeltoidtopalpatetheneurovascularbundle,therapheissplitandthenerveisisolatedandprotected(B).

A B

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tern,surgeon’sexperience,andspecificpatientfactorssuchasageandbonequality.Keyprinciplesforobtainingasatisfactoryresultincludestablefixationtoallowearlymobilizationandminimizationofsofttissuedisruptiontopreventfurthervascularcompromise.Complicationssuchasrotatorcuffdysfunction,stiffness,avascularne-crosis,malunion,andnonunionarerelativelycommonwithproximalhumerusfracturesandcanbeasignificantsourceofmorbidity. Theanteriorandmiddleheadsofthedeltoidaresepa-ratedbyanavascularfibrousraphe.8,9Thecourseoftheaxillarynerveafter itexits thequadrilateral spacehasbeen well described,10-16 but its position in relation totheraphehasonlyrecentlybeenreported.6Theanteriormotorbranchoftheaxillarynervecrossesthehumerustransverselyatvariabledistancesasasinglenerveandpenetratesthefasciaofthedeltoidbeforeorafterdividingintoseveralsmallerbranches.8,12Duparcandcolleagues11found that in 12 of 32 shoulders (38%), the anteriortrunkbranchedintosmallermotorbranchesafterentryintotheanteriorheadofthedeltoid,andintheremain-ingspecimensthedivisionoccurredatvariabledistancepriortomuscleentry.Theseinvestigatorsdidnotfocusontheraphespecifically. Innervationofthedeltoidisfromtheaxillarynerve,whicharisesfromtheposteriorcordofthebrachialplex-usandpasses through thequadrilateralspacedividingintoanteriorandposteriorbranches.Theposteriorbranchsends several smaller branches to the teres minor, thedeltoid,andthesuperiorlateralbrachialcutaneousnerve.Theanteriormotorbranchcoursesaroundtheneckofthehumerusandpassesmediallyontheanteriorsurfaceofthesurgicalnecktosupplythemiddleandanteriordeltoidheads.Thelocationsoftheintramuscularbranchesarevariable and when the deltoid is split intramuscularly

formorethanseveralcentimetersdistally,denervationof the anterior head of the deltoid from disruption ofthese fibers invariably occurs. Division of the raphedistally may avoid these problems. It has been shownthatseveralbranchestothemiddleheadfromthemainbranchoccurapproximately9.8mmbeforecrossingtheraphe,themainanteriormotorbranchcrossestherapheasasinglenerve,andthefirstbranchesfromthemaintrunktotheanteriorheadariseapproximately8.5mmaftercrossingtheraphe.6Thus,astherapheisdivided,aslongasthemainanteriormotortrunkisprotected,nootherbranchesareatrisk. Thedeltopectoralapproachforexposureoftheante-riorandlateralshoulderregionhasbeenmostcommonlyusedforplatingoftheproximalhumerus.However,ac-cessingthelateralaspectoftheproximalhumerususingthis approach requires extensive soft tissue dissectionandretraction,asitisanindirectapproachtotheplat-ingzone.Thisislessthanidealforinternalfixationofproximalhumerusfracturesanditfurtherjeopardizesthecompromisedbloodsupplytotheheadofthehumerusandfracturefragments.Ithasbeenadvisedthatanydis-sectionlateraltothedeltoid-pectoralintervalinthedistaldirectionbelimitedtothreetofivecentimetersfromtheacromion to avoid injury to the axillary nerve.8,9,12,17,18Recent data has shown that the anterior motor branchoftheaxillarynervecrossestherapheatapredictablelocationrelativetotheacromionandgreatertuberosity,6whichallowsmoredirectaccesstotheproximalhumerusafterprotectingtheaxillarynerve. Theincidenceofavascularnecrosisafterclosedre-ductionrangesfrom3%to14%inthree-partfracturesandupto34%infour-partfractures.19Surgicalinsultofthesofttissueenvelopeanddirectmanipulationofthefracturefragmentswithdisruptionoftheconsolidatingcallousfurtherincreasethisriskandavascularnecrosismay be as high as 37% following open reduction andinternalfixation.20Theheadofthehumerusisperfusedbybranchesoftheanteriorhumeralcircumflex,posteriorhumeralcircumflex,suprascapular,thoracoacromial,andsubscapulararteries.Theanteriorandposteriorhumeralcircumflexvesselshavebranchesthatdirectlypenetratebone;otherarteriescontributethroughanastamosissys-temswiththecircumflexvessels.Gerberandassociates21reportedthattheanteriorhumeralcircumflexarterywastheonlyarterythatcouldalonesupplytheentirehumeralhead and that the posterior humeral circumflex arterymainlysuppliedthegreatertuberosityandasmallareaofthehumeralheadthroughinterosseousanastamoseswithbranchesoftheanteriorcircumflexartery.Theanteriorcircumflexhumeralarteryarisesfromtheaxillaryarteryaboutonecentimeterdistaltotheinferiorborderofthepectoralismajorandcourseslaterallyalongtheinferiorborderofthesubscapularistendon.Itscourseplacesitatriskwhenastandarddeltopectoralapproachisused,

Figure 3 Demonstration inacadavershoulderof isolating theaxillarynerveandposteriorhumeralcircumflexvessels,followedbyadvancingaplatefromproximaltodistaldeeptotheneuro-vascularbundle.

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particularlywithdistorted anatomy in the settingof afracture.Theposteriorhumeralcircumflexarterypassesthroughthequadrilateralspacewiththeaxillarynerve.

Bothofthesestructuresarereadilyvisualizedandpro-tectedusingtheanterolateralraphe-splittingapproach,andthereisnodissectionmediallynearthecourseofthe

Figure 4A64-year-oldfemalewithosteoporosisfellonherleftsideandsustainedacomminutedproximalhumeralfracture(AandB).Anextendedanterioracromialapproachwasused;theaxillarynerveandvesselswereisolatedandlength,alignmentandrotationofthefracturewereobtained.Alockingplatewasthenapplied(C),towhichthetuberositiesweresuturedanatomically.Apostoperativeradiographshowsanatomicreduction(D).

A B

C D

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criticalanteriorhumeralcircumflexartery. The recent rise in popularity of using fixed-angleplate-screwconstructs toprovidebiologicfixationhasaltered many surgeons’ approach to fracture manage-ment.1,22Theseplatingsystemsactasinternalfixatorsandhavetheadvantageofnotrequiringperiostealstrippingordirectappositionoftheplateontobone.Thefocusisshiftedfromabsolutemechanicalrigiditytobiologicalpreservation.23,24Theplatecanbeinsertedthroughasmallincisionremotetothefracturesite,preservingthesofttissuesandprecludingtheneedfordirectexposureofthefracturefragments.Becausethereisonlypointcontactwithboneandnofrictionisrequiredbetweentheplateandbone,thesedevicesactaspuresplints.Nolongerisatightinterfacebetweentheplateandbonerequiredforstability,ratherloadisdistributedevenlyamongallthebone-screwinterfaces.25Reductionoftemporarycorticalporosisbyvascularpreservationandimprovedmechani-calstabilitywithoutfragmentcompressionaretwoofthekeybenefitsoflockedplating.Thisconceptofflexiblefixationhasbeenshowntopromotecallusformation,1,26,27and animal studies have revealed stronger bone afterhardware removalaswellasdecreasedcomplications,suchasinfectionandstressshielding.27

Asinternalfixationconceptsandtechniquescontinuetoevolve,thedevelopmentofnovelminimally-invasivesurgicalapproachesiscritical.Thedegreeofsofttissuedissectioninherentinthedeltopectoralapproachiscoun-terproductivewhenattemptingtoadheretotheprinciplesofbiologicalfixation.Thisextendedanterioracromialapproachallowsalimitedsurgicalapproachtobeused,preservingtheperiosteum,andwhencoupledwithlockedplating,providesstablefixationtoinitiateindirectbonehealing.28These techniquesmaybeparticularlyusefulinosteoporoticproximalhumerusfractures,wherescrewpurchase may be suboptimal, and in unstable surgicalneck fractures,whichare inherentlyunstable (Fig.4).Thoughfurtherclinicalstudy iswarranted,useof thisapproachmaydecreasecomplicationsandimproveout-comesin theoperative treatmentofproximalhumerusfractures.

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