Rev. bras. ortop. vol.49 número6

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

Updating

Article

Osteochondroma:

ignore

or

investigate?

夽

Antônio

Marcelo

Gonc¸alves

de

Souza

_,

_Rosalvo

_Zósimo

_Bispo

_Júnior

a_{SchoolofMedicine,FederalUniversityofPernambuco(UFPE),Recife,PE,Brazil} b_{SchoolofMedicine,FederalUniversityofParaíba(UFPB),JoãoPessoa,PB,Brazil} c_{UniversityCenterofJoãoPessoa(UNIPÊ),JoãoPessoa,PB,Brazil}

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Articlehistory:

Received23August2013 Accepted31October2013 Availableonline27October2014

Keywords:

Osteochondroma/etiology Osteochondroma/physiopathology Osteochondroma/diagnosis Boneneoplasms

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Osteochondromasareboneprotuberancessurroundedbyacartilagelayer.Theygenerally affecttheextremitiesofthelongbonesinanimmatureskeletonanddeformthem.They usu-allyoccursingly,butamultipleformofpresentationmaybefound.Theyhaveavery charac-teristicappearanceandareeasilydiagnosed.However,anatypicalsite(intheaxialskeleton) and/ormalignanttransformationofthelesionmaysometimesmakeitdifficultto iden-tifyosteochondromasimmediatelybymeansofradiographicexamination.Inthesecases, imagingexaminations thataremorerefinedarenecessary.Although osteochondromas donotdirectlyaffectthesepatients’lifeexpectancy,certaincomplicationsmayoccur,with varyingdegreesofseverity.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditora Ltda.Allrightsreserved.

Osteocondroma:

ignorar

ou

investigar?

Palavras-chave:

Osteocondroma/etiologia Osteocondroma/fisiopatologia Osteocondroma/diagnóstico Neoplasiasósseas

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Osteocondromas sãoprotuberânciasósseas envolvidasporumacamada decartilagem. Atingem, habitualmente,asextremidades dos ossos longosno esqueletoimaturo e os deformam.Emgeralsãoúnicos,masaformadeapresentac¸ãomúltiplapodeser encon-trada.Deaspectobastantecaracterístico,sãodefácildiagnóstico.Contudo,porvezes,a localizac¸ãoatípica(esqueletoaxial)e/ouamalignizac¸ãodalesãopodemdificultarasua prontaidentificac¸ãoporexamesradiográficos.Nessescasos,examesdeimagemmais apura-dossãonecessários.Apesardenãoafetaremdiretamenteaexpectativadevidadoportador, algumascomplicac¸ões,comvariadosgrausdegravidade,podemocorrer.

©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublicadoporElsevierEditora Ltda.Todososdireitosreservados.

夽

Pleasecitethisarticleas:deSouzaAMG,BispoJúniorRZ.Osteocondroma:ignorarouinvestigar?.RevBrasOrtop.2014;49:555–564.

∗ _{Correspondingauthor.}

E-mail:[email protected](R.Z.BispoJúnior).

2255-4971/$–seefrontmatter©2014SociedadeBrasileiradeOrtopediaeTraumatologia.PublishedbyElsevierEditoraLtda.Allrightsreserved.

556

Introduction

Debatecontinuesastowhetherosteochondromaisa devel-opmental disorder (pseudotumoral lesion) or a neoplasm.1

Nonetheless, irrespectiveof whetherit is apseudotumoral lesionoramorecommonbenignbonetumor,2_{itiscertainlyan}

exostosis(externalboneproliferationthatdeformsthebone).3

Thisboneprotuberanceisgenerallyfoundintheimmature skeletonofchildrenandadolescents(Fig.1).

AccordingtotheWorldHealthOrganization(WHO), osteo-chondromas are bone projections enveloped bya cartilage coverthatariseontheexternalsurfaceofthebone.1_Despite

theirpredominantcomposition ofbone,their growthtakes placeinthecartilaginousportion.4

Theypresent two distinct clinical forms5_{: singlelesions}

(solitary osteochondromas) and several lesions (multiple osteochondromas).

Solitary

osteochondroma

This entity is also known as an osteochondromatous exostosis,1 _{osteocartilaginous exostosis}4,5 _{or simply}

exostosis.2

Multiple

osteochondromas

Among the various synonyms used in the literature, the commonestonesare:hereditarymultipleexostosis,multiple cartilaginousexostosis,hereditaryosteochondromatosisand multiplehereditaryosteochondromatosis.

Fig.1–Anteroposterior(AP)radiograph(A)andlateralradiograph(B)oftheleftknee.Noteexostosis(osteochondroma– arrows)intheproximalregionofthetibiainaskeletallyimmaturepatient.

Epidemiology

Solitaryosteochondroma

This formconstitutes 10% of all bone tumorsand,among these, 35% (20–50%) of the benign tumors.1,4–8 _Single

lesions arefoundin85% ofthe individualsdiagnosedwith osteochondroma.5_{Theexostosisiscommonlyidentified}

dur-ingchildhoodoradolescence.1,4

Osteochondromasmorefrequentlyaffecttheappendicular skeleton(upperandlowerlimbs).5_{Thelongbonesofthelower}

limbsarethebonesmostcommonlyaffected.6,9–11_Theknee

istheregionmostaffected(40%ofthecases)(Fig.2).5–7,12_After

theknee,theproximalportionsofthefemurandthehumerus are thesitespreferentiallyaffected.Afterosteochondromas appearinthelongbones,theyusuallybecomelocatedinthe metaphysisandonlyrarelyinthediaphysis.2_{Flatboneslike}

thescapulaandhipmayalsobeinvolved(Fig.3).5

Despitetheslightpredominanceofthemalegenderover thefemalegenderthathasbeenreportedbysomeauthors,4,5,7

it seemsthatthereisnoeffectivepredilectionaccordingto sex.1

Multiple

osteochondromas

Some authors have reported that the incidence of mul-tiple osteochondromas is 1:50,000 individuals.1,13 _Among

patients withexostosis,15%havemultiplelesions.1 _Inthis

presentation, osteochondromas tend to be large and ses-sile, withalobulated abundantcartilaginouscover.5 _{In the}

Fig.2–Thelongbonesofthelowerlimbs(kneeregion)aremostcommonlyaffected.(A)Simplelateralradiograph.(B) Computedtomographywith3Dreconstruction.Notelesion(arrows)intheproximalregionofthetibia.

osteochondromashaveapredilectionforthemetaphysisof the long bones, and especially those of the lower limbs (Fig.4).14

Theagesofpatientswithmultiplelesionsare similarto thoseofothers withsingleexostoses, and thereisalsono predilectionaccordingtosex.1

Etiology

The cause of osteochondromas remains unknown. Based onthesimilarityofthecartilaginouscover oftheexostosis tothe growth cartilage (growth plate) ofthe bone, several hypotheseshave been put forward, all of them relating to alterationstothegrowth plate.1 _{Anotherfact that}

corrobo-ratesthe possiblecorrelation betweenthe cartilage (of the osteochondromaand epiphyseal plate) isthat when skele-tal maturity is reached (after adolescence), the growth of the lesion usually also ceases.2 _{Thus, the lesion seems to}

result from separation of a fragment of growth cartilage (from the immature skeleton), which suffers herniation.2

Continuous growth of this loosepiece of cartilage and its subsequentendochondralossificationformsasaliencethat projects from the bone surface, coated with a covering of cartilage.2 _{However, it is still unclear how this separation}

actuallyoccurs.2

Thevariantwithmultiplelesionsisadominant autoso-malalteration15,16 _{that istransmittedbybothsexes and is}

characterizedbythepresenceofseveralosteochondromas.2

Inthisgroup,mostoftheindividualshaveapositivefamily historyand/ormutationinoneoftheEXTgenes.17,18 _These

genes(EXT1,EXT2andEXT3)arefoundinchromosomes8,11 and19,respectively.19–22

Clinical

diagnosis

Solitaryosteochondroma

Among solitary osteochondromas, the vast majority are asymptomatic.7,8,15,23 _{Infact,theyareusuallydiscoveredby}

chance.Aftertheyhavebeendetected,theypresent slowly increasingbulgingandhardenedconsistency,butarepainless (Fig.5).1,2

Symptomatic cases are often related to the size and location of the exostosis. In the immature skeleton, the

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Fig.4–Hereditarymultipleexostosis.(AandB)Intheknees,radiographsshowingmultiplelesionsintheproximalregions ofthetibiasandfibulas.

osteochondromagrowsslowlyand progressivelyalongwith the bone involved, and it stops when skeletal maturity is reached.24

Inafewcases,painofgreaterintensitymaybepresent, associatedwithcomplicationsofamechanicalorigin1 _that

arepromotedbytheprojectionofhardtissue(bone)intothe softtissues.14 _{Whetherduetosimplecontact,compression}

orfriction,varyingdegreesofparesthesia,paresis,cracking, edema,rednessorpallorcanbeobserved,dependingonthe anatomicalstructureaffectedbytheexostosis.

In osteochondromas of pedunculate type (see imaging diagnosticssection),acutepainmayoccurduetofracturing ofthebaseofthepediclefollowinglocaltrauma.1,4,14,25

Multipleosteochondromas

Inthemultipleformofthiscondition,lowheight,deformities ofthebonesaffectedanddisproportionbetweenthetrunkand limbscanbeobserved.2,5,14,17,26–28_{Severeinvolvementofsome}

bonespromotesshorteningandosteoarticulardeformity,with

consequentlimitationofjoint rangeofmotion.14_Themain

examplesofthiscomprisedeformityoftheforearm(dueto shorteningoftheulna),inequalityofthelengthsofthelower limbsandangling(varusorvalgus)oftheknee(Fig.6).13,29,30

Malignanttransformation

Rapidly increasing lesion size and local pain processes suggest that sarcomatous transformation is occurring in individuals with osteochondroma that was previously asymptomatic.1,16,28,30,31 _{Continuing growth of the lesion}

afterskeletalmaturityisreachedshouldalsoawaken such suspicions. Other clinical findings that are occasionally reportedincludeslightincreasesinsofttissues,elevationof temperatureandlocalerythema.30

Imaging

diagnostics

Simpleradiographs

Theradiographicappearancereflects thecomposite nature ofthelesion,formedbycorticalandmedullarybonetissue,2

whichprojectsoutwardsfromtheaffectedbone.Itisprecisely thecontinuityofthelesionwiththesurfaceofthehostbone thatispathognomonicforosteochondroma.2_{Thiscontinuity}

iseasilyobservedinlesionsthat“inhabit”thelongbones,2_in

thestandard radiographicviews(twoimagesinorthogonal planes).However,inplanarbones (pelvisand scapula)and irregularbones(vertebrae),thisrelationshipandconsequently thediagnosismaynotbeevidentonsimpleradiographsalone (Fig.7).2

The characteristic image consists of an external bone protuberance1,4 _{and it may havea wide base(sessile) or a}

Fig.6–Radiographofanindividualwithhereditary multipleexostosis.Notethedeformityoftheforearm(due toshorteningoftheulna).

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Fig.8–Differenttypesofosteochondroma.Notethatinexamination(A),thelesiononthehumerusissessile(withwide base–arrows),whilein(B),itispedicledorpedunculated(narrowbase[arrow],i.e.lessinrelationtoitsheight).

narrowbase(pedicled or pedunculated)(Fig. 8). Becauseof thesingularappearanceoftheselesions,itispossibleinmost cases,forexample,todoawaywithbiopsiesfordiagnosing them.

The cartilaginous cover is often not visible in these examinations, because its density is similar to that of

the surrounding soft tissues.15 _{However, cartilaginous}

cal-cifications may sometimes be observed.15,23,31 _Irregular

calcification is sometimes seen.1 _{However, on radiographs}

with excessive calcification of “flake” type,1

sarcoma-tous transformation of the osteochondroma should be suspected.

Fig.10–Computedtomographyimagesfacilitatelocatingtheexostoses(whiteovalfigures)atanatomicalsitesofgreater complexity(suchasthespine–sacralregion).(A)Axialimage.(B)3Dreconstruction.

Computedtomography

Thistechniquecomplementsradiographsandshowsdetails ofthecontinuityofthecorticalandspongyboneinsidethe lesion32–37_{andtheirrelationshipwiththeadjacentsofttissues}

(Fig.9).Axialtomographicslicesfacilitateinterpretation2 _of

thelesionslocatedinanatomicalsitesofgreatercomplexity,23

suchasthespineandthebeltsoftheupperandlowerlimb (Fig.10).

Magneticresonance

Thisisanexaminationthatalsodemonstratesthecorticaland medullarycontinuitybetweentheosteochondromaandhost bone.2_{Inthesame wayasseeninanormalpieceofbone,}

thecorticalboneoftheexostosispresentslowsignalintensity (hyposignal)inallsequences,whereasthemedullary compo-nentcontinuestohavetheappearanceoftheyellowmedulla (Fig.11A).2

Thisisacceptedasthe safestimagingmethodfor eval-uatingstructures adjacent to the osteochondroma and for observingandmeasuringthecartilagecover2,30_thatenvelops

theexostosis.Thethicknessofthislayerisusedasacriterion fordifferentiatingsuspectedsarcomatousmalignant transfor-mationfromcartilaginoustissue1,30_{(Fig.11B).However,there}

isnoconsensusofopinionsinthisregard.30_Someauthors1,4,38

havesuggestedthatathicknessgreaterthan2cm(inadults) maybeindicativeofmalignanttransformation,whileothers haveacceptedthispossibilitywhenitisgreaterthan1.5cm.2

Ithastobeborne inmindthatduringchildhood,this car-tilagelayerisnaturallythickerthan inthematureskeleton andmayreach3cm.Calcifiedareasofthecoverpresentlow signalintensityinT1andT2-weightedsequences.2_However,

highconcentrationsofwaterinthenon-calcifiedportionof thislayershowanintermediatetolowsignalonT1-weighted imagesandahighsignalonT2-weightedimages.2

Bonescintigraphy

Thecartilaginoustissue(cover)oftheexostosismayormay notpresenthighuptakeofradiopharmaceuticals,bothunder conditionsofnormalityandinsituationsofmalignant trans-formation(secondarychondrosarcoma).Forthisreason,bone

scintigraphy does not have great value in differentiating betweenbenignandmalignantcartilaginouslesions.39

Anatomopathological

diagnosis

Macroscopicappearance

The lesion surface is lobulated and has an abundant car-tilaginous cover (Fig. 12).5 _{These are lesions that vary in}

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Fig.12–Intraoperativephotographofexcisionofan osteochondroma.Noteitsmultilobulatedsurfaceand cartilagecover.

size considerably: from 1 to 10cm.2 _{The cartilage cover}

maypresent dimensionsof1–3cminthicknessinyounger patients.6,9,12,32,33,40,41

Microscopicappearance

Solitary and multiple osteochondromas are histologically similar.30 _{Thelesion presents threelayers}1_{: perichondrium}

(mostexternal),cartilage(intermediate)andbone(most inter-nal).

Malignanttransformation

Differentiationfromnormalcartilageisgenerallydonein rela-tiontosecondarychondrosarcomaoflow-grademalignity.30

Lossofcartilagearchitecture,mitoticactivity,presenceofcell atypiaandnecrosisaresomeofthefindingsthatmayindicate secondarymalignanttransformation.1

Treatment

Solitaryosteochondroma

Presenceofanexostosisis,initself,insufficientreasonforits surgicalexcision,especiallyinisolatedcases.42_{Forindividuals}

withsinglelesions,themanagementisexpectantinthegreat majorityofthecases,withsuccessivereturnvisitsbecauseof thechance(albeitsmall)ofmalignanttransformation.

Surgicalremovalisindicatedifthetumorcausespainor functionalincapacity,4_{eitherduetoneurovascular}

compres-sionorduetolimitationofjointmovement(Fig.13).Another situationforsurgicalremovalrelatestofracturingofthebase oftheosteochondroma.25

Multipleosteochondromas

Inthesepatients,thetreatmentismorecomplex.Inthe multi-pleformsofthispathologicalcondition,osteochondromasare

Fig.13–Surgicalresection(specimen)waschosenforthis exostosisthatwascausingvascularcompressioninthe poplitealregion.

removedsurgicallyforcosmeticreasons,43_{inordertoavoid}

progressionofthebonedeformities.Intheforearm,for exam-ple,simpleexcisionofthelesion(inthedistalportionofthe ulna)mayimpedelocaldeformity.44

Malignanttransformation

Sarcomatoustransformationisgenerallytreatedbymeansof widesurgicalresection,withpreservationofthelimb,30_while

followingrigorousoncologicalcriteria.

Complications

Amongthepossiblecomplicationsoftheselesionsare frac-tures (generally of pedunculated exostoses, at their base), vascular lesions (formation of pseudoaneurysm) and neu-rological complications (compression of peripheral nerves, which involves the spine or the periarticular regions), for-mation ofa bursa (whichaffects the cartilaginous surface of the lesion, resulting from local friction) and malignant transformation.5,14,30,45 _{Thislastcomplication, whichisthe}

mostfearedofallthecomplications,isveryvariablein fre-quency: insolitaryosteochondromacases,it occurs inless than 1%1,16,23,45_{; while in patients with multiple lesions it}

mayrangefrom1%to30%1,4–6,9,46–48_{indifferentseries.}

How-ever, studies conductedmorerecentlyhave suggestedthat theprevalenceislower:3%to5%inindividualswithmultiple osteochondromatosis.49–54

Final

remarks

Osteochondromasare benignlesions thatdonotaffectlife expectancy.However,theriskofmalignanttransformation(to secondarychondrosarcoma)shouldbetakenonto consider-ation,especiallyincasesofmultipleexostoses.

aviewtomakingaprecisediagnosis.Furthermore,ifthereis clinicalsuspicionofmalignanttransformationand/or radio-graphic alterations in comparison with old examinations, magneticresonance imaging is well indicated for detailed analysisonthethicknessofthecartilaginouscoating.

Insituationsinwhichexcisionoftheosteochondromais chosen,thisisusuallycurative.Recurrenceisseenincasesof incompleteremoval.

Theoverall survivalofpatientswithsarcomatous trans-formation is generally good. However, those with poorly differentiatedlesionshaveamuchworseprognosis.

Conflicts

of

interest

Theauthorsdeclarenoconflictsofinterest.

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