Rev. bras. ortop. vol.52 número4

SOCIEDADE BRASILEIRA DE ORTOPEDIA E TRAUMATOLOGIA

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

Review

Article

Lateral

patellar

retinacular

release:

changes

over

the

last

ten

years

夽

Leonardo

Pini

Rosalem

Marciano

da

Fonseca

,

Ednei

Haruo

Kawatake

,

Alberto

de

Castro

Pochini

a_{HospitalNovoAtibaia,Atibaia,SP,Brazil}

b_{UniversidadeFederaldeSãoPaulo,EscolaPaulistadeMedicina,DepartamentodeOrtopediaeTraumatologia,SãoPaulo,SP,Brazil}

a

r

t

i

c

l

e

i

n

f

o

Articlehistory:

Received18May2016 Accepted30June2016 Availableonline15June2017

Keywords:

Patellofemoraljoint Jointinstability

Patellofemoralpainsyndrome Kneeosteoarthritis

Kneearthroplasty

a

b

s

t

r

a

c

t

Lateralretinacularreleaseisausefulresourceinkneesurgerythatcanbeusedfordisorders oftheextensormechanism.Formanyyears,itwasindiscriminatelyusedinthetreatment ofthevariouspatellofemoraljointalterations,withconflictingfunctionalresults.Thisstudy aimedtoanalyzethechangesthathaveoccurredintheindicationsandclinical effective-nessoflateralretinacularreleasebyreviewingtherelevantliteratureofthepasttenyears, comparingittotheclassicliteratureonthesubject.Itwasfoundthatlessextensivereleases decompressthelateralpatellarfacet,helpingwithpaincontrol,whiledecreasingtherisks ofmedialsubluxation.Nowadays,thereisclearevidenceforitsindicationinthelateral patellarhypercompressionsyndromeassociatedwithanteriorkneepain,aslongasthereis norelatedinstability;furthermore,itwillnormallyplayanadjuvantroleinextensor mech-anismalignmentsurgeriesforcasesofrecurrentpatellarinstability.Theinitialresultsfor symptomaticpatellofemoralosteoarthritisarepromisingwhenlateralreleaseiscombined withcartilagedebridement;intotalkneereplacement,itismorecommonlyusedforthe correctionofvalgusdeformityinordertoimprovethecomponents’congruency.Finally, distinguishingthedifferentpatellofemoraljointpathologiesisseenascrucialinorderto indicatethisprocedure.Furtherrandomizedcontroltrialsthatcomparesurgicaltechniques withlong-termresultsarestillneeded.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.ThisisanopenaccessarticleundertheCCBY-NC-NDlicense(http:// creativecommons.org/licenses/by-nc-nd/4.0/).

夽

StudyconductedattheHospitalNovoAtibaia,InstitutodeCirurgiadoJoelhoDr.KenjiKawakami,Atibaia,SP,Brazil,andatthe UniversidadeFederaldeSãoPaulo,EscolaPaulistadeMedicina,DepartamentodeOrtopediaeTraumatologia,Centrode Traumato-OrtopediadoEsporte,SãoPaulo,SP,Brazil.

∗ _{Correspondingauthor.}

E-mail:[email protected](L.P.Fonseca). http://dx.doi.org/10.1016/j.rboe.2017.06.003

Liberac¸ão

retinacular

lateral

da

patela:

o

que

mudou

nos

últimos

dez

anos

Palavras-chave:

Articulac¸ãopatelofemoral Instabilidadearticular Síndromedadorpatelofemoral Osteoartritedojoelho

Artroplastiadojoelho

r

e

s

u

m

o

Aliberac¸ãoretinacularlateraldapatelaéumrecursoútilnascirurgiasdojoelhoepode serfeitanasdesordensdomecanismoextensor.Durantemuitosanos,foiusadadeforma indiscriminadaparaotratamentodasdiversasalterac¸õesdaarticulac¸ãopatelofemoral,com resultadosfuncionaisconflitantes.Oobjetivodesteartigoéanalisarasmudanc¸asocorridas nasindicac¸õesenaeficáciaclínicadaliberac¸ãoretinacularlateraldapatelaaorevisara lit-eraturapertinentedosúltimosdezanosecontrapô-lacomaliteraturaclássicasobreotema. Encontrou-sequeliberac¸õesmenosextensasdescomprimemafacetalateraldapatela, aux-iliamnocontroledador,enquantodiminuemosriscosdesubluxac¸ãomedial.Atualmente, existemclarasevidênciasparasuaindicac¸ãonasíndromedahiperpressãolateraldapatela associadaadoranteriordojoelho,desdequenãohajainstabilidadeconcomitante;além disso,oprocedimentogeralmenteatuarádeformaadjuvanteemcirurgiasderealinhamento domecanismoextensornoscasosdeinstabilidadepatelarrecorrente.Osresultadosiniciais paraoscasosdeosteoartrosepatelofemoralsintomáticasãoanimadoresquandose com-binaaliberac¸ãolateralcomodesbridamentocartilaginoso;naartroplastiatotaldojoelho, émaiscomumentefeitanascorrec¸õesdasdeformidadesemvalgoparamelhorara con-gruênciadoscomponentes.Finalmente,percebe-secomocrucialadistinc¸ãodasdiferentes patologiasdaarticulac¸ãopatelofemoralparaquesepossaindicaresseprocedimento.Ainda hánecessidadedemaisensaiosclínicosrandomizadoscomvistasàcomparac¸ãodetécnicas cirúrgicascomresultadosemlongoprazo.

©2016SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevier EditoraLtda.Este ´eumartigoOpenAccesssobumalicenc¸aCCBY-NC-ND(http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Introduction

Lateralretinacularreleaseofthepatellaisausefulresource for knee surgeries and may be performed in disorders of the extensor apparatus, whether or not associated with otherprocedures.Thetheoreticbasisofthistechniqueisthe imbalanceoftheextensionmechanismcausedbyexcessive tension of the lateral retinaculum, which contributes to patellofemoraldisorders,suchasanteriorkneepain,acuteor chronicinstability,patellarchondropathy,andpatellofemoral osteoarthrosis(OA).1–3

Formanyyears,lateralretinacular releaseofthepatella hasbeenusedindiscriminatelyforthetreatmentofvarious extensor mechanism abnormalities, presenting conflicting functionalresults.4_{Overtheyears,ithasbeennotedthatin}

ordertoeffectively treatpatellofemoraljointdisorders,it is importanttobetterunderstandtheanatomical and biome-chanicalissuesinvolvedinthisjoint.2

Thisarticleaimedtoanalyzethechangesinindications and clinical efficacy of lateral patellar retinacular release by reviewing the relevant literature of the last ten years, comparing it with the classic literature on the subject. To conclude, the authors suggest a possible role that lateral retinacularrelease playstodayinthesurgical treatmentof majorpatellofemoraldisorders.

Anatomy

of

the

patellofemoral

joint

Thepatellofemoraljointisintrinsicallyunstableanddepends on bone morphology and musculotendinous structures to maintainitsstability.3_{Thisstabilityisinfluencedbythe}

geom-etryofthetrochleargroove,bothindepthandtilt,sincethe lateralsurfaceofthetrochleargrooveishigheronthe ante-riorsurfaceofthefemurand decreasesinmoredistaland posteriorpositions,animportantbonescaffoldforthe patel-larexcursioninextensionandinitialflexion.AstheQangle increasesfromflexiontoextension,thetensioninthe quadri-cepsandpatellartendonsdecreases.Thisoccursbecausethe tibiarotatesexternally,thusmovingthetibialtubercle later-ally,inamechanismknownasscrew-home.Thisrelationship contributestogreaterpatellarinstabilityinextensionandin smalldegreesofflexion,causingpatellardislocation.Inturn, duringflexion,thequadricepsand patellartendonsforma posteriorforcevector,providinggreaterpatellarstability.4,5

Thevastusmedialisoblique(VMO)muscleactivelyactsas astabilizer,whilethemedialpatellofemoralligament(MPFL) andthelateralretinaculumarepassivestabilizers.Imbalances mayoccurduetoVMOmuscleweakeningorincreasedtension inthelateralretinaculum.3,4

ligament;increasedtensionintheiliotibialtractmaycause patellarlateralization.Inturn,theMPFLisaprimary restric-toroflateralpatellardislocationbetween0◦_and30◦_offlexion,

actingasanimportantmedialkneestabilizer.4,5

The imbalance of these forces generally represents an increasedtensioninthelateralretinaculumandaweakening in the VMO muscle. This can be improved with rehabili-tation focused on muscle strengthening; however, the use of tight lateral retinaculum release has been a subject of debate.3,6

Biomechanical

effects

of

lateral

patellar

retinacular

release

Themainbiomechanicalfunctionofthepatellaistoincrease themomentumoftheextensormechanism.Theloadonthe joint increases with increasing flexion.7 _{In their cadaveric}

studies,Ostermeieretal.8_{concludedthatlateralreleasedid}

notincreasemedialpatellarinstabilitythroughoutitsrangeof motion;nonetheless,thecontactpressurewasmoremedial, between60◦ _and120◦ _{offlexion,whichreducespressureon}

thelateralsurfaceduringflexion.Conversely,ifanextended releaseismade,itcanresultinasignificantincreaseinmedial patellarinstability,increasingtheriskofmedialdislocationof iatrogeniccause.3

Lateral

retinacular

release

in

patellofemoral

instability

The stability of the patellofemoral joint depends on the alignment ofthe lower limb,on the patellarand trochlear osteocartilaginous architecture, on the integrity of the lig-ament structures, and on the function of the dynamic stabilizers.4,9,10_{Therefore,patellofemoralinstabilityisa}

mul-tifactorial problem, and proper treatment depends on an accurateunderstanding oftheexisting biomechanical rela-tionships between the structures.4 _{An accurate diagnosis}

thatdifferentiatesprimarytraumaticpatellardislocationfrom chronic instabilityand subluxation, and these from lateral patellarhyperpressuresyndrome,11_{isparamountforthe}

indi-cationoflateralretinacularrelease.

Althoughthelateralretinaculumcontributestoonly10% ofthelateralstabilityofthepatella,12_{whenunderexcessive}

stressit oftenleadstoabnormalcontactofthe lateral sur-faceagainstthetrochlea,increasedlateralinclinationofthe patella(tilt),andpathologicalchangesofthepatellar track-ing (maltracking).In turn,patellarhypermobilityrelated to anincreasedligamentlassitude,withorwithoutahigh rid-ing patella, or related toVMO muscle dystrophy may lead topatellofemoralinstability, commonlyobservedinfemale adolescents.2,10

Over 100 different types of surgery have already been describedforthetreatmentofpatellofemoralinstability, gen-erallyinvolvingacombinationofproceduressuchaslateral retinacularreleasewithmedialplication,proximalordistal re-alignment,andMPFLreconstruction.13–22 _Todate,a

gold-standardcorrectivesurgeryforthedisorderhasnotyetbeen

defined,3,4 _{and the proportion of satisfactory results after}

isolated lateral retinacular release reported inthe classical literaturerangesfrom30%to100%.14,23,24

Inaseriesof41casesofrecurrentpatellardislocationthat underwent lateralretinacularrelease,DandyandGriffiths25

observedthattheresultsconsideredgood(51%)orexcellent (39%)afterameanfollow-upoffouryearspresenteda sig-nificantdecreaseinthefollowingfouryears,atasecondary assessment.26_{Theseauthorsalsodemonstratedthatpatellar}

subluxationinextension,globalligamenthyperlaxity,andthe degreeofosteochondrallesionsofthepatellaatthetimeofthe procedureweretheworstprognosticfactors.25,26_In1992,

Agli-ettietal.23_{demonstratedthatthetreatmentofpatellofemoral}

instabilityonlybyisolatedlateral retinacular releaseledto arecurrencerateof35%.Daineretal.27_{concludedthatthis}

typeoftreatmentwasineffectiveincasesofrecurrentpatellar dislocation.

These concepts remained consolidated in the opinion of expertsover the years until 2004, when Fithian et al.28

conducted asurvey of27 of the 45 members ofthe Inter-national Patellofemoral Study Group about their views on the indications ofretinacular lateral release and observed thatalthoughmostexpertsperformedtheprocedureinless than 2%oftheirsurgicalcases,therewasno consensusas tothe bestclinicalor radiologicalevidenceavailableforits indication.Theauthorsconcludedthattheprocedureshould notbeperformedwithoutobjectiveevidenceofatensioned lateral retinaculum and that it shouldrarely beperformed alone.

By analyzingthe long-term results of100 patients who underwentlateralretinacularreleasebetween1986and1994, Pannietal.29_{notedadeteriorationofthesatisfactoryresults}

in the group with patellofemoral instability when com-paredwiththegroupthathadonlyanteriorkneepainafter a minimum follow-up of five years. Satisfaction rates fell from 72%to50%over timeinthat group;theauthors con-cludedthatthisreductionwasprobablyduetothefactthat other factors contributed topatellar instability, whose cor-rectionwouldnotbepossiblewithlateralretinacularrelease alone.

Similarly,inaliteraturereview,Lattermannet al.30

ana-lyzedtheresultsof14studiesontheroleoflateralretinacular release in the treatment of patellofemoral instability and observedameansatisfactionrateof80%inthosestudieswith afollow-uptimeoflessthanfouryears;thisratedecreasedto 63.5% instudieswherepatientswereassessedforalonger period. Theauthors concluded that the isolated procedure had little orno utility,and shouldbe reservedforthe rare casesinwhichthe lateralpatellarhyperpressuresyndrome isclearlyidentifiedinthepresenceofatensionedlateral reti-naculum.Theysuggestthattheprocedurecanbeusedasan adjunctinextensormechanism realignmentsurgeries,and thatitshouldbeperformedwithgreatcautiontoavoid exces-siverelease,whichmaycauseiatrogenicmedialsubluxation ofthepatella.Thisfearedcomplication9,30,31_{usuallyoccurs}

In order to try to understand the limits of the lateral retinacular release, recent studies on the subject appear to focus more on the surgical techniques used, analyzing themprospectively,associatedornotwithotherprocedures, andsometimesinthelaboratory,incadavericbiomechanical studies.6,8,12,19,21,22,32,33

Inaseriesof20caseswithhistoryofrecurrentpatellar dislocationwho underwentarthroscopicreleaseoftheVLO muscletendon,Woodsetal.22_{aimedtoassesswhetherthere}

wasasignificantlossofquadricepstorqueforce, with con-sequentfunctionalimpairmentofthekneeinthesepatients, whichcouldexplaintheunsatisfactorypostoperativeresults hitherto.Thepre-andpostoperativequadricepsstrengthwas comparedusinganisokineticdynamometerandtheIKDCand

ShortForm-36functional scoresinaminimumfollow-up of twoyears.Theauthorsfoundthat14ofthe20patients(70%) hadanincreaseinquadricepsstrength,17(85%)reporteda functional improvementofthe operatedknee, with conse-quentimprovement ofthe physicalstate, and no cases of recurrence or medial instability were observed. They cau-tion,however,thatthistechniqueshouldbeusedinsuitably selectedpatients.

In contrast, two years later, Miller et al.32 _{published a}

series of 25 patients who underwent arthroscopic medial plication without lateral retinacular release. One of the objectives was precisely to assess the need forthe use of lateral release as part of routine surgery in patients with patellofemoral instability who have minimum patellar tilt

andnormalalignment.Their studyusedcongruenceangle, lateral patellofemoral angle, lateral patellar displacement, patellarphysicalexaminationmaneuvers(seizure, compres-sion,andpatellarmobility),aswellasthefunctionalscales ofLysholmandTegner,andsubjectivesymptomaticcriteria as comparative parameters between the pre- and postop-erativeperiods, with amean follow-up of60 months. The authors observedanimprovementin all assessed parame-ters,aswellassatisfactionlevelssimilartothose observed instudieswithlateral retinacularrelease,whichledtothe conclusion that medial plication can lead to good results without the complication risks inherent to the release procedure.

In anattempt to compare the success rates ofsurgical techniques,Ricchettietal.21_{conductedasystematicreview}

oftheliteratureandcontrastedtheresultsofstudieson iso-lated lateral retinacular release with those of studies that usedthistechniquetogetherwithamedialrealignment pro-cedure(reefing,plication,VMOadvance)forcasesofrecurrent patellar instability.After applyingthe inclusion and exclu-sioncriteria, the authors reviewed14articles withlevel of evidenceIIIandIVandobservedasignificantsuperiorityof thecombinedprocedure:thecombinedprocedurehadamean successrate of93.6%,associatedwithalowerlikelihood of recurrenceovertime,versusthemeansuccessrateof77.3% fortheisolatedprocedure, whichhadasignificantlyhigher chance of recurrence (odds ratios). Therefore, the authors concludedthattheuseofisolatedlateralretinacularrelease led to worse results over time when compared with joint procedures.

With comparable objectives, Lee et al.33 _{retrospectively}

reviewed 31 cases of recurrent patellar dislocation treated by plicationassociatedwith percutaneouslateral retinacu-larrelease, withamedianfollow-up of11.6±2.4years.As evaluationparameters,theauthorsusedtheKujalaand Teg-nerfunctionalcriteria,thesubjectivescaledescribedbyDrez et al.,34 _{and semiotic and radiological measuressimilar to}

previousstudies;theydescribedthecaseswithdysplasia tro-clearbyDejourclassification,35_{orthosewithpatellofemoral}

osteoarthritis, imposing strict exclusion criteria. By being judicious in the selection of patients in which the afore-mentionedparameterswereassessed,theauthorsobserved significant improvements in the clinical and radiological results, a low complication rate, no cases with evolution to osteoarthritis (OA), and only 10% of recurrence. It is noteworthy that, of the three cases reoperated, two had trochleardysplasiaandonehadsystemicligament hyperlax-ity.Finally,theauthorsdiscussedtheadvantagesofthistype ofsurgicaltechniqueoverthealreadyrenownedMPFL recon-structionasasurgicaltreatmentoptionforrecurrentpatellar dislocations.

Lateral

retinacular

release

in

patellofemoral

pain

Lateral retinacular release was widely used in the 1970s and 1980sasatreatmentforanteriorknee painsyndrome, withwidelyvaryingpostoperative satisfactionratesamong studies at the time.13,36–39 _{Comparing the results of these}

studiesisdifficultduetothedifferentmethodologiesused, patient selection, follow-up, evaluation criteria, and espe-cially thedifferentterminology used.Many studiesdidnot distinguish betweenpatients who had both patellofemoral pain andinstability fromthose who had onlypain oronly instability.14–16,39

Nonetheless, it was demonstrated that inpatients with lateral patellar hyperpressure syndrome, evidenced by an increase in the patellar tilt observedat knee CT or at the test of medial patellar slide in extension,40 _{a significant}

improvementinpainwasobservedintheshorttermafter lat-eralretinacularrelease.9,11,38,40–42_{However,theresultswere}

less than satisfactory in patients who had Outerbridge43

grade III or IV patellar chondropathy at surgery and in those who presented patellofemoral instability in addition to pain.3,13 _In1982,18 _{Metcalfindicated thatyoung women}

generally had worse prognosis and that the proportion of good and excellent results deteriorated after one year of follow-up. Krompinger and Fulkerson42 _{reportedworse}

lat-eral retinacular release results in patients with Q angles greaterthan20degrees,andGechaandTorg41_{observedbetter}

resultswhenpatellarhypermobilityormalalignmentwerenot detected.

Intheirhistologicalstudy,Morietal.44_{suggestedthatthe}

strongconsensusamongexpertsthatthereductionofthe lat-eraltension,whichleadstoareliefofthesurfacepressure togetherwiththe denervation,isthemechanism bywhich thelateralreleaserelievespain.

Pannietal.29_{publishedaretrospectiveclinicaltrial}

com-paring long-term resultsof lateral retinacular release in a group of patients who presentedonly patellofemoral pain with those of another group who presented only instabil-ity,excludingthosewithahistoryofpatellardislocationand osteoarthritis.Asevaluationparameters,theLysholmIIand BuschandDeHavenquestionnaireswereused,aswellasthe classical radiologicalmeasurements describedbyMerchant andMercer.39_{Amongthemostimportantfindings,the}

func-tionalcriteriadidnotdeteriorateovertimeforpatientswho onlyhad patellofemoralpain;themean rateofsatisfactory resultsremainedat70%,whereasthosewhohadinstability presentedasignificantworseningintheirfunctionalcondition withinfiveyearsaftertheprocedure.

Inasystematicreviewoftheliteratureontheuseof lat-eral retinacular release foranterior knee pain, Lattermann etal.45_{observedthattheisolatedprocedureyielded76%good}

resultswhenstudieswerecompiled;nosignificantdifference wasobservedbetweenopenorarthroscopicprocedures,and complicationrateswereminimal.Theaggregateresults indi-catedaneedforrevisionsurgeryin12%ofthecasesaftera meanof52monthsoffollow-up,buttheauthorsemphasized thatthesurgicalprocedureisnecessaryinlessthan15%of patientspresentingwithanteriorknee pain.Intheir study, theauthorscalledattentiontotheneedforrandomized clin-icaltrialstobetterevaluatethebenefitsofthisprocedurein thetreatmentofanteriorkneepain.

Recently, Pagenstert et al.19 _{conducted a prospective}

double-blindedstudy of28 patients, comparing the lateral retinacularreleasetechniquewiththeirtechniqueoflateral retinacular stretching. After a minimum follow-up of two years,theauthorsfoundbetterfunctionalresultsintheKujala scorefor thegroup submitted tostretching,who also pre-sented less medialinstability and less quadriceps atrophy, whicharecommoncomplicationsreportedinlateral retinac-ularrelease.10,17,18,46,47

Lateral

retinacular

release

in

patellofemoral

OA

IsolatedOA ofthepatellofemoral compartmentisa preva-lentdisease,affectingapproximately11%ofmenand24%of womenover55yearsofagewithcomplaintsofpatellofemoral pain. In rare cases, this condition is not associated with trochlear dysplasia or poor alignment ofthe lower limb.48

Thus,itcanbeinferredthattreatmentwithlateral retinac-ulumreleasewillprobablyleadtounsatisfactoryresults.

IntheclassicalstudybyAgliettietal.,23_{lessthan20%of}

thecasesofpainorinstabilityassociatedwithpatellofemoral OApresentedfavorablefunctionaloutcomeafterarthroscopic lateralretinaculumrelease.Usingthesametechnique, Ader-intoandCobb1_{conductedaretrospectivestudytoassessthe}

resultsof53proceduresinpatientswithpatellofemoralOA, usingtheOxfordKneescoreandthevisualanaloguepainscale

(VAS).Although80%ofthepatientsreportedanimprovement insymptoms aftera meanof31monthsoffollow-up, 42% remainedunsatisfied,whichtheauthorsinterpretedas pos-siblyduetohighexpectationofimprovementbythepatients. They concluded that this minimally invasive procedure is valuableforselectedpatientsandpromotestemporarypain relief, postponingtheneedformajorinterventionssuchas patellofemoralortotalkneearthroplasty(TKA).Intheirstudy, theauthorsalsodemonstratedthatthepresenceof femorotib-ialOAdidnotsignificantlyinfluencetheresultsobtained.

Recently,biomechanicalexperiencesincadaverspointed toaworsening ofpatellar stabilityaftersequentiallylarger releasesofthelateralretinaculum,butsuggestedthat pres-sureonthelateralsurfaceofthepatellacanbealleviatedwith thisprocedure.5,8,12_{Ostermeieretal.}8_{demonstratedthatthe}

medializationafterlateralreleaseofthehighpatellofemoral pressurepointthatoccursin30◦_–70◦_{offlexion,inwhichmost}

pain complaintsare observed,could haveadecompression effectonthelateralsurfaceofthepatella.

In2008,Alemdarogluetal.49_{conductedaprospectivestudy}

in35patientsabovethefifthdecadeoflifewithgradeIIandIV patellarchondrallesionswhounderwentlateral retinacular release combined with cartilage debridement via radiofre-quency.TheauthorsobservedimprovementsintheWOMAC index for OA and in the VAS, regardless of the degree of chondropathy,whichweremaintainedforuptotwoyearsof follow-up.

Lateral

retinacular

release

in

TKA

Lateralretinacularreleasemaybecomenecessaryif,afterall implantsareplaced,thepatellapresentsatendencyforlateral positioning orsubluxation.Thepatellarcomponent is usu-allyplacedmoremediallywithrespecttothecenterofthe retropatellar surface, recreating the asymmetricalcontours ofthe apex, centralizingthe quadricepstendon and patel-larreactionforce,andtherebyimprovingalignment.However, once the femorotibial components havebeen cemented in placeorsnap-fittedontothebonesurfaces,failuretocorrect patellarpositionorfailureinthefemoralcomponentrotation cannotberectifiedbylateralrelease,whichmaynecessitate formalrevision.50

Lateral retinacularrelease ismostcommonlyperformed onkneearthroplastieswithvalgusdeformitytoimprovejoint congruity,51–55_{decreasingtheincidenceofanteriorkneepain,}

especially if the patellar component is notperformed.52,56

WithTKA,theforcesandpeakpressuressignificantlyincrease inthepatellofemoraljoint,andlateralreleasemayreducethe ratiooftheseforcesandpressureinthisregion,8,54,57,58_with

lowratesofcomplications.51,55,56

Complications

of

lateral

patellar

retinacular

release

Hemarthrosis and medial patellar subluxation, usually of iatrogeniccause,arethemaincomplicationsoflateral reti-nacularrelease.4,9,22,31,37_{Morerarely,albeitnotlessseriously,}

complex regional pain syndrome, weakening of the knee extensor mechanism, and skin burnrelated to the arthro-scopic procedure may be observed.46 _{In addition to these}

complications,theprocedureisconsideredtohavefailedin casesofinsufficientreleaseofthelateralretinaculum,hence maintainingthepreviousclinicalpicture.2,9,10,22,41_InTKA,in

turn,this proceduremay present avascularnecrosisofthe patellaasacomplication;itisimportanttopreservethe super-olateralgeniculateartery,locatedlaterallytothesuperiorpole ofthepatella,asitisthemainsourceofpatellarcirculation, sincethemedialgenicularvesselsaresacrificedinthemedial parapatellarapproachtotheknee.50

Theincidenceofhemarthrosisvariesgreatlybetween stud-iesanddependsonthetechniquechosen;arelativeincrease isreported in arthroscopic procedures in which therewas failureintheidentificationandhemostasisofthe superolat-eralgenicularartery.13,22 _{TheclassicstudybyHughstonand}

Deese31 _{indicated that lateral retinacular release had been}

previouslyperformed in 89% of the 65 knees operated for symptomaticmedialsubluxationofthepatella.Theauthors recommendedthatthekneeshouldbeflexedandextended several timesintraoperatively to confirm the improvement ofpatellar congruence inthe trochlear groove afterlateral release.Apracticalwaytoavoidthis dreadedcomplication istoensurethatthereleasedoesnotextendbeyondthefibers oftheVLO.4

Fortunately,withthepassageoftimeand the identifica-tion ofthe limits oflateral retinacular release,lower rates ofcomplicationshavebeenobservedwhentheprocedureis judiciouslyindicated.22,46_Elkousy46_{elaboratedaninstructive}

dichotomyofthecomplicationsrelatedtodiagnosticand indi-cationerrorsfromthose relatedtointraoperative technical errors,suggestingwaystoprevent,detect,andfixtheproblem.

Final

considerations

Themainconclusionsofthisreviewoftheliteratureregarding theroleofthelateralretinacularreleaseofthepatellainthe maindisordersofthepatellofemoraljointinclude:

(1) Less extensive retinacular releases, which respect the upperandlowerlimits,decompressthelateralsurfaceof thepatellaandaidinpaincontrol,whilereducingtherisks ofmedialdislocationofiatrogeniccause.

(2) Thereisclearevidenceforitsindicationinlateralpatellar hyperpressuresyndrome,demonstratedbyanincreaseof thelateralpatellartiltassociatedwithanteriorkneepain, sincethereisaconcomitantinstability.

(3) Itwill usually actadjunctively in extensor mechanism realignment procedures in cases of recurrent patellar instability.

(4) InTKA,itismostcommonlyperformedinthecorrection ofvalgusdeformitiestoimprove the congruenceofthe components,aswellastodecreasethepeakpressurein thepatellofemoraljoint.

(5) When this procedure is combined with cartilagi-nous debridement, the initial results (<2 years) for patellofemoralOAareencouraging.

(6) It is necessary to accurately differentiate the distinct pathologiesofthepatellofemoraljoint sothatthis pro-cedurecanbeindicated.

(7) Further randomizedclinical trials comparinglong-term resultsofsurgicaltechniquesarestillnecessary.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

r

e

f

e

r

e

n

c

e

s

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