mediallyandorlaterallyandisimmediatelypalmartothemetacarpalboneRestin - PDF document

1 mediallyand/orlaterallyandisimmediatelyp
mediallyand/orlaterallyandisimmediatelypalmartothemetacarpalbone.Restingmetacarpophalangeal(MCP)jointangleisoftennormalwithsuper“cialdigital”exortendi-nopathybecauseoftheactionoftheothersupport-ersofthisjoint(SLandDDFT).Additionally,painwillresultinareducedloadingofthelimb.How-ever,incasesofseveresuper“cialdigital”exorten-dinopathy,theaffectedlimbshowsgreaterthannormaloverextensionoftheMCPjointwhentheloadonthelimbincreases(e.g.,whenthecontralat-erallimbisraisedorwhenwalking).Severedam-agetotheSLwillhaveagreatereffectonMCPjointextension.ALDDFTdesmitisrarelyaffectslimbpostureunlessadhesionsoccurbetweenitandthe”exortendons.Inthatcase,thelimbcantakeontheappearanceofa”exuraldeformity.Inacaseofsuspected”exortendoninjury,carefulpalpationofthetendonsandligamentsinthelimbshouldbemadebothwhenthelimbisbearingweightandnotbearingweight(”exed).Whenweightbearing,enlargementisassessedbycompar-isonwiththecontralaterallimb;however,bilateraldiseaseiscommon.Withthelimbraised,the”exortendonsbecomeslack.Carefulattentionshouldbegiventopainresponse,subtleenlargement,whichoftenmanifestsasanindistinctbordertotheten-don,andconsistencyofthestructure(softafterre-centinjuryand“rmafterhealing).Thehorsemustberelaxedsothatmuscleactivitydoesnottensethetendonsandmakethemappeararti“cially“rm.Thisassessmentshouldalsoincludethecontralat-erallimb,becausemanystrain-inducedinjuriesarebilateral;however,onelimbisusuallymoreseverelyaffectedthantheotherlimb.SwellingoftheALDDFTisdetectedbyproximalswelling,usuallypredominantlylaterally,becausethisiswherethebodyoftheligamentissituated.Enlargementisbestidenti“edwiththelimb”exedandpalpatedbetweent

2 he”exortendonbundleandtheSLintheproximal
he”exortendonbundleandtheSLintheproximalmetacarpalregion.ThesameevaluationshouldbemadefortheSL.Unfortunately,theproximalregionisimpossibletopalpateintheweight-bearinglimb,especiallyinthehindlimb,becauseitiscoveredbytheheadsofthesplintbonesandthetaut”exortendons.Theprox-imalSLintheforelimbcanbepalpatedintheraisedlimbbymovingthe”exortendonstoonesideandpressingbetweentheheadsofthesplintbones.Acomparisonshouldbemadebetweensides,be-causesomenormalhorsesmayrespond.Percutaneoustendoninjuriesareusuallyassoci-atedwithmoderatetoseverelamenessandmayormaynothaveaconcurrentwound.Ifawoundispresent,itshouldbeinitiallycleanedandthenex-ploreddigitallywithsterileglovesto“ndthedam-agedstructures.Smallwoundsmayhinderfullevaluation,becausethetendonlacerationsite,sus-tainedunderfullweight-bearingload,isunlikelytobevisibleinthewoundwhenthehorseisseverelylame.Insuchcases,concurrentultrasonographicexaminationisveryhelpful.Penetrationinjuriesorpartialseveranceofatendonwillnotalterthefunctionofthetendon,andtherefore,otherthanlameness,therewillbelittlealterationinlimbconfor-mation.Completetransection,however,isassoci-atedwithsigni“cantalterationsinlimbconformationunderloading.SDFTistheoverextensionoftheMCPjointunderweight-bearingload.DDFTistheoverextensionoftheMCPjointatrestandwhenweightbearing;thetoeiselevatedfromthegroundwhenweightbearing.SListheMCPjointontheIfthelacerationiscomplete,theproximalpartofalaceratedtendonoftenrecoilsandcanbecomere-”ectedonitself.Itisalsonecessarytoassessifanysynovialstructureshavebeenpenetrated.Thisisacommoncomplicationoftraumatothedistallimbsandwillfrequentlyleadtosynovialsepsis.3.Ultrasonograp

3 hyIndicationsforUltrasonographicEvaluati
hyIndicationsforUltrasonographicEvaluationoftheTendonandLigamentInjuries1.DiagnosisAlthoughmostmetacarpal/metatarsaltendonandligamentinjuriesareeasilydetectablebypalpation,palpationprovidesapoorobjectiveassessmentoftheseverity.Abase-linescancanprovideanas-sessmentofseveritythatmayrelatetoprognosis.Itisusuallyperformed7…10daysafterinjury,be-causeinjuriescanworseninitially.Inthepas-tern,however,non-speci“c“brosisthatcommonlyaccompaniessofttissueinjuriesinthisregionmakesaccuratedeterminationoftheinjuredstructuredif“cult.Therefore,ultrasonographyisessentialforestablishinganaccuratediagnosisinthisregion.2.ManagementFollow-upultrasonographicexaminations(ideallyevery2…3mo)areusedtooptimizemanagementdecisionsduringtherehabilitationphase.UltrasonographicTechniqueThelimbshouldideallybepreparedbyclippingastripofhairfromthepalmaraspectofthelimb.FortheproximalSLinthehindlimb,itisusefultoextendthisclippedareatothemedialaspecttoincreasethesizeoftheultrasonographicwindow.ŽThebodyoftheSLisusuallyalsoevaluatedfromthepalmaraspect;however,thisonlyenablestheaxialone-thirdoftheligamenttobeexamined.There-fore,amorecompleteexaminationcanbeachievedbyincreasingtheclippedareafortransducerplace-4762008Vol.54AAEPPROCEEDINGSIN-DEPTH:TENDONANDLIGAMENTINJURY Thistechniqueisparticularlyusefulforidentifyingexacerbationsduringthehealingphase.5.UltrasonographicAppearanceoftheMetacarpalRegionandPasternRegionsProximally,thetendonlieswithinthecarpalsheathasasemi-circularstructurethatispalmaromedialtotheDDFT(Figs.5and6).Asthetendonrunsdistally,itreducesintheCSAandadoptsaroundedmedialcontourandsharperlateralborder.Inthedistalmetacarpalre

4 gion,itthinsinadorsopalmardirectionandex
gion,itthinsinadorsopalmardirectionandextendsaringoftissuearoundtheDDFT(themanica”exoria).Tearingoftheattach-mentofthisstructuretotheSDFTcancauselame-ness(especiallyinhindlimbs),althoughdiagnosingthisultrasonographicallyisdif“cult.Distaltothefetlock,theSDFTcontinuesasathinstructurethatthendividesintotwobranchesinthemid-pasternregion.Beforeitsdivision,thedistalmanica,ŽanotherringoftheSDFTsurroundingtheDDFT,isusuallyvisibledeeptotheDDFT.Itisausefullandmark,butcontrarytoitsmoreproximalsister,itisrarelysigni“cantlyinjured.ThetwoSDFTbranchesrunabaxiallytoinsertthroughthethick“brocartilagenousmiddlescutumontotheproximopalmaraspectofthemiddlepha-lanx.Thesebranchesarebestobservedultrasono-graphicallyascomma-shapedstructureswiththetransduceronthepalmarolateralandpalmarome-dialaspects.Intheproximalforelimb,theDDFTliesdorsolateraltotheSDFT.Asthetendonrunsdistally,itbe-comesmorecircularandalsoreducesintheCSA.Inthemid-metacarpallevel,theALDDFTjoinstheDDFTonitsdorsalsurfaceandbecomesenclosedintheoneparatenon.However,the“bersoftheAL-DDFTcanbeidenti“ed,separatedfromtheDDFTbyahypoechoiccurvedline,foranappreciabledis-tancedistally.Inthedistalmetacarpalregion,theDDFTincreasesintheCSAandbecomesovalinshapeattheleveloftheMCPjoint.Inthehind-limb,thedorsalsurfaceoftheDDFTusuallyhasawell-circumscribedhypoechoicregionwithinitintheproximallimitofthedigitalsheaththatisWithinthepasternregion,theDDFTwillfre-quentlycontainadorsalhypoechoicregionimmedi-atelydistaltotheergotcausedbyoff-incidenceartefactfromthechangedirectionintheDDFT.AstheDDFTrunsdistally,itadoptsabilobedTheDDFTcanbeexaminedfurtherdistally,butthisrequiresasmallfo

5 otprint(e.g.,curvilinear)probethatcanbep
otprint(e.g.,curvilinear)probethatcanbeplacedinthelongitudinalplanebetweenthebulbsoftheheel.Thisallowsidenti-“cationoftheDDFTdistallytotheleveloftheproximalborderofthenavicularbone,butitisoffincidence.TheDDFToverlyingthenavicularboneandinsertingontothesolarsurfaceofthedistalphalanxcanbeseenwhenscanningthroughthefrog;however,onlythecentralportionsoftheten-donarevisible.Thisligamentarisesfromthepalmarcarpalliga-mentswhereitliesonthedorsalsurfaceofthecarpalsheath.Itrunsfromadeeppositionproxi-mallytoamoresuper“cialpositiondistallywhereitjoinsontothedorsalsurfaceoftheDDFTinthemid-metacarpalregion.Proximally,itisadiscretestructurethatisseparatefromtheotherstructuresonthepalmaraspectofthelimbwithaprominentlongitudinalstriatedpattern.Itrunsinaslightlyobliqueanglecomparedwiththe”exortendons,anditson-incidenceechogenicitytendstobeataslightlydifferentprobeorientationtothe”exortendons.Thus,the”exortendonsortheALDDFTcanappearbrighterthantheotherdependingonprobeorienta-tion.Asitrunsdistally,itstartstoconformtothedorsalsurfaceoftheDDFT.Themajorityoftheligamentislaterallypositionedsothatthetrans-ducerhastobemovedtoapalmarolateralpositiontoviewtheentireligament.Atitsorigin,theechogenicitycanbeveryvariable,anditcanincludecentralhypoechoicregions.Thesenormalvariantsarecausedbyareasoflooserconnec-tivetissuewithintheligamentthatcontainfatandvascularelements.Theyareusuallybilaterallysym-metrical,butthepresenceofhypoechoicareasinthisregionshouldonlybeinterpretedinthelightofclinicalexaminationanddiagnosticanalgesia.Thedorsalborderoftheligamentisusuallydistinctandsepa-ratedfromtheunderlyingpalmaraspectofthemeta-carpusbyasm

6 allanechoicgap.Thishypoechoicarea Fig.4.
allanechoicgap.Thishypoechoicarea Fig.4.Longitudinalultrasonographfromthemid-metacarpalregionfromahorsewithadamagedSDFTthatshowedincreasedvascularitywithcolor-”owDopplerinanon…weight-bearinglimb.AAEPPROCEEDINGSVol.542008479IN-DEPTH:TENDONANDLIGAMENTINJURY becomesobliteratedwhentheligamentisenlargedthroughpathology.BothproximalandbodyregionsoftheforelimbSLarerectangularinshapeintransverseimages,butthisonlyrepresentsthemiddleone-thirdofthelig-amentbecauseofthesizeoftheultrasonographicwindow.Themedialandlateralborderscanonlybevisualizedbytiltingthetransducerontothepal-maromedialandpalmarolateralaspectsproximallyandthenpositioningthetransducerdirectlyoverthemedialandlateralbordersinthemid-metacar-palregionwherethesplintbonesaresmaller.Be-causeofthevariablepresenceofmusclewithintheproximalandbody(butnotthebranches)oftheSL, Fig.5.Diagramrepresentingtheultrasonographicanatomyofthemetacarpalregion.(A)Transverseimages.(B)Longitudinalimages.(FromSmithRKW,WebbonPM.Diagnosticimaging„musculoskeletalultrasonography.In:HodgsonDR,RoseR,eds.Theathletichorse.1992.)4802008Vol.54AAEPPROCEEDINGSIN-DEPTH:TENDONANDLIGAMENTINJURY thelongitudinalstriatedpatternoftheSLismorecoarsethanseeninthe”exortendons.TheproximalSLinthehindlimbismoretriangularinshape,anditiscloselyassociatedwiththelargeheadofthefourthmetatarsal(lateralsplint)boneandthesmallerheadofthesecondmetatarsal(medialsplint)bone.Thisareaisdif“culttoevaluateandcanbeimprovedbyoneofthefollowingtwoactions:1.Movethetransducertothemedialaspectofthelimb.Theultrasonographicwindowislargerinthislocationbecauseofthesmallheadofthesecondmetatarsalbone.Amorecompleteevaluationof

7 theproximalSLcanbeobtainedinthislocation
theproximalSLcanbeobtainedinthislocation;however,edgerefractionartefactsfromtheprominentbloodvesselssuper“ciallyinthisregioncaninduceshadowswithintheproximalSL.2.Useacurvilineartransducerorcompound-ing,Žwhichprovidesawiderviewofthedeeperareas.Inlongitudinalviews,theproximalSLhasastri-atedpattern,andthemajorityoftheligamentisattachedtotheproximalpalmar/plantarmetacar-pus/metatarsus.Themostsuper“cialportionoftheligament,however,continuesandinsertsmoreInthedistalone-thirdofthemetacarpalregion,theSLadoptsadumbbellshapeintransverseim-agesasitdividesintotwoseparatebranches.Be-causeofedgerefractionshadowingfromthebordersofthe”exortendons,thebranchescannotbevisu-alizedadequatelyfromthepalmaraspectofthelimb,andtherefore,thetransducerneedstobemovedsothatitliesdirectlyoverthemedialandlateralSLbranches.ThesebranchesincreaseintheCSAinaproximodistaldirectionandareatear-dropshape.Theylieimmediatelyadjacenttotheskin.Anypathologyinthesebranchesresultsin“brosisbetweenthebranchandtheskin,whicheffectivelymovesŽthebranchawayfromtheskin. Fig.5.(continued)AAEPPROCEEDINGSVol.542008481IN-DEPTH:TENDONANDLIGAMENTINJURY Correspondinglongitudinalimagesshouldalsobeobtainedstartingwiththemostdistaloftheselon-gitudinalimageswheretheattachmentsiteoftheSLbranchontotheabaxialsurfaceoftheproximalsesamoidboneappearsasanS-shapedsurface;thishasbeentermed,descriptively,theski-jumpview.Ž Fig.6.Diagrammaticrepresentationofultrasonographicanatomyofthepasternregion.(FromSmithRKW,WebbonPM.Softtissueinjuriesofthepastern.In:Robinson,NE,ed.Currenttherapyinequinemedicine,4thed.Philadelphia:W.B.SaundersCo.,1997;61…69.)4822008Vol.54AAEPPROCEEDIN

8 GSIN-DEPTH:TENDONANDLIGAMENTINJURY Thebr
GSIN-DEPTH:TENDONANDLIGAMENTINJURY Thebranchesshowsimilar“beralignmentto”exortendonsatthislevel.DigitalSheathThedigitalsheathextendsfromthedistalmetacar-pal/metatarsalregiontothefootonthepalmar/plan-taraspectofthelimb.Therefore,abnormalitiesofthisstructureshouldincludeevaluationofthisen-tireregion.Thedigitalsheathiscommonlyassoci-atedwithpathologyinthepasternregion,althoughitsinvolvementismorefrequentlysecondary.Innormalhorses,thedigitalsheathcontainsonlysmallamountsofsynovial”uid,anditsintrathecalarchitectureisoftenobscure.However,witheffu-sion,morestructuresbecomevisible.Outpouch-ingsofthedigitalsheathcanbeseenproximallyabaxialtothe”exortendons,immediatelydistaltotheproximalsesamoidbonesabaxially,andinthedistalpasternregioninthemidlinesuper“cialtotheDDFT.Thisisthebestsitetoaspiratesynovial”uidfromthesheath.Inthedistalmetacarpalregionwithintheproxi-malpouchofthedigitalsheath,abaxialsynovialplicaeconnecttheDDFTtothedigitalsheathwallbothmediallyandlaterally.Althoughnotnor-mallyvisibleinthenon-distendedsheath,theyareeasilyidenti“edwiththeimprovedcontrastassoci-atedwithsheathdistension.Theplicaeshouldnotbeconfusedwithadhesions,buttheyareusefulstructureswithwhichtoassessthestatusofthesynovialmembrane.Inthedistalpasternregion,anormalthinmeso-tenonissometimesvisibleinthemidlinebetweentheDDFTandthedigitalsheath.Palmar/PlantarAnnularLigamentoftheFetlockIdenti“cationofthepalmar/plantarannularliga-mentofthefetlock(PAL)innormalhorsesisdif“-cultbecauseofitssize(1…2mminthickness).However,movingtheprobemediallyorlaterallyawayfromthemidline(wheretheannularligamentisjoinedtotheSDFTbythevinculum)willimprovede“nitio

9 noftheligamentbytherelativelyhypo-echoge
noftheligamentbytherelativelyhypo-echogenicsynoviallining(synovial”uid)betweenitandtheSDFT.Ifitstillcannotbeidenti“edwithcon“dence,theprobeshouldbemovedfurtherme-diallyorlaterallytovisualizeitsattachmenttotheverypalmar/plantarborderoftheproximalsesam-oidbones.SomeveterinariansprefertoassessthePALbymeasuringthedistancebetweenthepalmar/plantarsurfaceoftheSDFTandtheskinsurface,althoughthisdistancewillincludetheskin,SCtissues,PAL,andsynovialmembrane.Allofthesecanbeaf-fectedtoavariabledegreeintheconditionofannu-larligamentsyndrome(seebelow).Anormalmeasurementof3.60.7mmhasbeenquoted;therefore,anything5mmshouldbeconsideredDigitalAnnularLigamentsThedigitalannularligaments(proximalanddistal)cannotbeeasilyvisualizedinthenormalhorse,becausetheyareusually1mminthickness.However,theycanbeseenwhenenlarged.Theycanbeidenti“edproximaltothedistalout-pouchingofthedigitalsheath,especiallymediallyandlater-allywheretheyaremorediscretestructuresgrossly.DistalSesamoideanLigamentsBoththeobliquedistalsesamoideanligament(ODSL)andstraightdistalsesamoideanligament(SDSL)canbeidenti“edultrasonographically.TheSDSLsarethemostechogenicstructureswithinthisregionandareoftenmoreeasilyassessedinthelongitudinalimages.TheODSLsrequireobliqueviewsforadequateimaging.Theshortandcruci-atedistalsesamoideanligaments(DSLs)cannotbedistinguishedbutcansometimesbeidenti“edadja-centtothejointcapsuleinobliqueviewsofthepalmar/plantaraspectofthefetlockjoint.TheinsertionoftheSDSLsontothemiddlescutumonthepalmar/plantaraspectoftheproximalinterphalangeal(PIP)jointfrequentlycontainsahy-poechoiccoreŽorsandwichŽinthetransverseviews(P3only)andahypoechoicwedge

10 Žwithitsapexdirectlyproximallyinthelongi
Žwithitsapexdirectlyproximallyinthelongitudinalview.Thehypoechoicregiondoesnotusuallyextendfar-therproximallythanthedistallimitofinsertionoftheODSL.Thesearenormalanatomicalvaria-tionsandshouldnotbemistakenforpathology.DifferencesintheHindlimbTheultrasonographicanatomyofthemetatarsalre-gionissimilartothemetacarpalregion,butthereareafewdifferences:TheSDFTispositionedlaterallyandtheDDFTispositionedmediallyintheproximalmetatarsalregion.Thesubtarsalcheckligament(ALDDFT)isaverythinstructurelyingonthedorsalsurfaceofthedistaltarsalsheathwall.ThemedialheadoftheDDFT,initsownten-donsheath,joinstheDDFTonitsmedialbor-derintheveryproximalmetatarsalregion.TheSLarisesasatriangularstructureadja-centtothethirdandfourthmetatarsalbones(thelatterisparticularlyprominentproxi-Proximaltothetarsometatarsaljoint,threestructuresarevisualized„theSDFTsuper“-cially,theDDFTdeeptotheSDFTandmedi-allypositioned,andtheplantarligamentdeeptotheSDFTandlaterallypositioned.AAEPPROCEEDINGSVol.542008483IN-DEPTH:TENDONANDLIGAMENTINJURY 3.Animprovementinthestriatedpatternseenlongitudinally(“beralignment).4.Anabsenceofperitendinous“brosisandad-Morerecently,theblood”owwithinhealingdigital”exortendonscanbeassessedwiththelimbraisedusingDoppler(Fig.4).Normaldigital”exortendonsusuallyhaveminimaldiscernibleblood”ow,whereas,afterinjury,apronouncedvascularpat-ternisusuallyvisible.Hypervascularityisnormalinthehealingprocess.However,itshouldsubsideashealingprogresses(normallybetween3and6moafterinjury),anditsreappearancecanbeanindica-tionofreinjury.Horsessufferingfromtendonitisareconstantlyatriskofreinjury.Healing,determinedhistologi-cally,takesatleast1

11 5…18mo.Themeanintervalbetweeninjuryandre
5…18mo.Themeanintervalbetweeninjuryandreturntotraininginracehorsesisdependentontheseverityoftheinitialinjuryandvariesbetween9and18mo.Sportshorsesmaybeabletoreturntofullworkinashortertime,buteventhemildestultrasonographicallydetectablein-juriesshouldhaveatleast6motoheal.Occasion-ally,horsesarereturnedtofullworkbeforefullresolutionoftheultrasonographiclesion;however,thissuccessmaybecausedbythehorsebeingcapa-bleofsustainingworkdespitethepresenceofatendoninjury.ChronicTendinopathyTheultrasoundcharacteristicsofchronictendinopa-thyaremorevariableandcanbesubtle.Theten-donisoftenenlarged,butitsechogenicityvariesfromhypoechogenicthroughnormoechogenictohy-perechogeniciftheinjuryissevereandsubstantial“brosishasoccurred.Theintratendinouspatternisusuallymorecoarseandlacksstriationsinthelongitudinalimages(Fig.7).Insomecases,theoutlineoftheoriginalcorelesioncanstillbeseen.Mineralizationmayoccur,whichcausesacousticshadowing.However,ifthecalci“cationis”orid,previousintratendinousinjectionofdepotcorticoste-roidsshouldbesuspected.Off-incidencetrans-ducerorientationcanhelptode“neareasofdisorganizedscartissueinchronicinjury,becauseitretainsitsechogenicityatgreatertransduceranglesthannormaltendon(Fig.1).LocalTraumaOverstraininjuriesneedtobedistinguishedfromlocaltraumacausedbyabandage(so-calledban-dagebowŽ)orpercutaneoustraumafrom,forexam-ple,ahindlimb.Theeffectsoflocaltraumacanvaryfromlocalizedperitendinousedemawithnoevidenceofintratendinousdamagetolocalizedhy-poechoic/anechoiclesionsonthepalmarsurfaceofthetendon(Fig.8)topartialorcompletetransec-tion.Localtraumaticinjuriesdonotextendfarproximodistally.However,partialla

12 cerationscanbeassociatedwithlongitudinal
cerationscanbeassociatedwithlongitudinalsplitsinthetendonthatextendproximallyordistally;theseresultfromalteredshearstresses.Partiallacerationscanalsobeeasilymissediftheexaminationisrestrictedtothesiteofthewound,becausetheyoftenoccurwhenthetendonisfullyloaded.Therefore,thesiteofinjurymovesmoreproximallyintherestingorre-ducedweight-bearinglimb.Ultrasoundis,there-fore,veryusefultoidentifythesesitesofinjuriesnotvisiblethroughthewound.Completetransection Fig.7.(Left)Tranverseand(right)longitudinalultrasonographstakenfromtheproximalmetacarpalregionofahorsewithchronicsuper“cialdigital”exortendinopathy.NotetheenlargedSDFTwithheterogeneousechogenicityandapoorlongitudinalstriatedpattern.Thisissimilartotheappearanceofthetendoninthetransverseimage,whichsuggeststheabsenceofnormallyalignedcollagen“bers.AAEPPROCEEDINGSVol.542008485IN-DEPTH:TENDONANDLIGAMENTINJURY ofonebranchoftheSDFTinthepasternregionresultsinashiftinpositionoftheSDFTtowardthesideoftheintactbranchmoreproximally.Sepsisafterapenetratinginjury(oroccasionally,hematogenousspread)oftheSDFTisrare.Itusu-allygivesananechoiclesion,oftenwithacommuni-catingtracttotheperipheryofthetendon.Aspirationofthelesionwillyieldasamplecontaininglargenumbersofdegenerateneutrophils.Theselesionsdonotusuallycausegrossenlarge-mentoftheaffectedtendonandchangerapidlyintimecomparedwiththecorelesioninatendonstrain.Ifthelesionispresentwithinatendonsheath,therewillusuallybeanaccompanyingsepticManicaFlexoriaTearsThisisacommoncauseofdigitalsheathtenosyno-vitis,especiallyinhindlimbs.diagnosisisdif“cult,butanalteredpositionofthemanica”exoriaseeninalongitudinalscaninthemidlineimmediate

13 lyproximaltothemetacarpo/metatarsophalan
lyproximaltothemetacarpo/metatarsophalangealjointisprobablythebestindi-cator(Fig.9).Tenoscopicassessmentprovidesthede“nitivediagnosis.DeepDigitalFlexorTendinopathyDDFTinjuriesareextremelyrareinthemetacarpalregion,buttheydooccurwithinthecon“nesofthedigitalsheath.Ofthestrain-inducedDDFTinju-ries,therearetwoforms„theintratendinousinjuryandsurfacetears.IntratendinousInjuryIntratendinousinjuriesarefrequentlycenteredattheleveloftheMCPjoint.TheyresultfromasuddenoverextensionofthedistalinterphalangealjointwhentheMCPjointisfullyextendedandthelimbisweightbearing.Theseinjuriesarefre-quentlyassociatedwithconsiderabledisruptionofthetendonresultinginmarkedandpersistentlame-ness.Thereisusuallyconcurrenttenosynovitisandaswithmostsofttissueinjuriesinthephalan-gealregion,SC“brosis.OtherlesionsaremanifestbyfocalhypoechogeniclesionsproximalordistaltotheMCPjoint.Manycentraldefectsmayextendtothesurfaceofthetendonwithoutpenetratingtheepitenonandtherefore,maynotbevisibletenoscopi-cally(Fig.10).Becauseofthelocationoftheinjurieswithinthedigitalsheath,healingis,atbest,problematic.Inthechronicstage,thelesionsoftenpersistashypoechoiclesionswithorwithoutareasofcalci“-cation.Lamenessusuallypersists,arisingfromte-nalgiaand/oradhesionformationwithinthesheath.Suchadhesionscandistortthetendonshape.BorderTearsDamagetothesurfaceoftheDDFTcanoccurasavariantofoverextensioninjurytothetendon.Thisfrequentlyoccursatthelateralandlesscom-monly,medialbordersoftheDDFTintheregionoftheMCPjoint.Itoccursmostcommonlyinthe Fig.8.Transverseultrasonographfromtheproximalmetatar-salregioninahorsethathassufferedpercutaneoustraumatotheSDFT.Notetheplantarsur

14 facedefect(labeled). Fig.9.Thebestmethod
facedefect(labeled). Fig.9.Thebestmethodofdiagnosingamanica”exoriatearultrasonographicallyinvolvestheidenti“cationofinstabilityofthemanicainmidlinelongitudinalviewsinthedistalmetatarsalregion.(A)Thenormalcontralaterallimbisontheleft,andthetornmanica”exoriaisontheright.Notethewavyformtothemanica(arrows).(B)Tenoscopicappearance.Thearrowindicatestorn4862008Vol.54AAEPPROCEEDINGSIN-DEPTH:TENDONANDLIGAMENTINJURY corticosteroids,andbeta-aminoproprionitrilefuma-rate(BAPN).HAisacomponentoftendonmatrixandhasbeenadministeredperitendinously,intralesionally,andsystemicallytotreattendinitis.Inastudyofcollag-enase-induceddigital”exortendinitis,HAwasfoundtominimizetendonenlargementcomparedwithcon-trols;however,histopathologicalexaminationofthetendonsfailedtoshowasigni“cantdifferenceinthedegreeofin”ammation.PeritendinousHAhasbeenshowntohavenoeffectonultrasonographicorhistologicalappearance,biomechanicalproperties,ormolecularcompositionoftendonsincollagenase-in-ducedtendinitiscomparedwithcontrols,althoughitdidappeartoreducelameness.Areviewoftheeffectivenessofvariousmedicationshasfailedtoshowasigni“cantdifferencebetweenthereinjuryratesofhorseswithSDFTtendinitistreatedwithintralesionalHAcomparedwithconservativetreatment.drugisprobablymostappropriatelyusedinthereduc-tionofseverityofadhesionsafterintrathecalinjury.atleastthedepotpreparationssuchasmethylprednisolone,shouldnotbeinjecteddirectlyintotendonsorligaments,becausetheyhavebeenshowntocausedystrophictissueminer-alizationandtissuenecrosis,mostlikelyaconse-quenceofthecarrier.Peritendinousorsystemicuseintheearlystagesareappropriateandcanbeusedjudiciously.BAPN,alathyro

15 genthatinhibitstheenzymelysyloxidasethat
genthatinhibitstheenzymelysyloxidasethatnormallyformscross-linksbetweencol-lagen“bers,hasbeenusedtotreattendinopathy.Therationaleforitsuseistoallowexercisetopro-motealignmentofnewlyformedcollagen“brilswhilepreventingthembeing“xedinahaphazardfashionbycross-linking.BAPNdoesnothastentheresolutionofthetendinitis,butitaimstoim-provethestructureoftherepairedtendon.Earlyexperimentalstudiesincollagenase-inducedmodelsoftendonitisappearedtoshowimprovementinboththeultrasonographicappearanceandthehistologicalcollagenalignment.However,morerecently,concernshavebeenraisedoveritsef“cacybasedonobservationsthatBAPNreducescollagensynthe-andshowednoimprovementovercontrolsinarabbitmodeloftendinitis.ClinicalstudieshavesuggestedthatthereinjuryrateoflimbstreatedwithBAPNwasreduced,althoughtherateforbothlimbswasnodifferentfromothertreatments.Thisiscausedbythefactthatbothlimbsshouldbetreated,becauseunilateraltreatmentincreasestheloading/reinjuryriskonthecontralaterallimb.However,thedrughasbeenwithdrawnfromthemarketandtherefore,isnowrarelyused.3.Surgery1.TendonSplittingTendonsplittingwasinitiallyadvocatedasatreat-mentforchronictendinitistoimproveblood”owtodamagedtendontissue.Thetechniquefelloutoffavorwhensubsequentresearchshowedextensivegranulationtissueformation,increasedtraumatothetendontissue,andpersistentlamenesspost-Tendonsplittingis,therefore,nolongerrecommendedforthetreatmentofchronictendonitis.However,itisnowthoughttobemorerelevantforthemanagementofacutecaseswherethereisananechoiccorelesionevidentonultrasono-graphicexaminationthatindicatesthepresenceofaseromaorhematoma.Ithasbeenhypothesizedthatthepresenceofacorelesion

16 withinatendonproducesacompartmentsyndro
withinatendonproducesacompartmentsyndrome,Žwhichresultsindecreasedperfusionandischemiaoftheregion.Theaimoftendonsplittinginacutecasesistodecompressthecorelesionbyevacuatingtheserum/hemorrhageandtofacilitatevascularingrowth.Removalofthe”uidwithinthecorelesionmayalsoreduceproximodistalpropagationofthelesion.Inacollagenase-inducedmodeloftendinitisinsixhorses,tendonsplittingusingtheknifetechniqueresultedinafasterresolutionofthecorelesion,aquickerrevascularizationofthelesion,andanin-creasedcollagendepositionrelativetocontrols.Tendonsplittingmaybeperformedunderstand-ingsedationorundergeneralanesthesia.Itcanbedoneblindlyorusingultrasonographicguidance,whichminimizesdamagetonormaltendontissuebyenablingtheneedleorknifetobeinsertedatapointwherethecorelesionisclosesttotheperipheryofthetendon.A#11scalpelbladeordouble-edgedbladeisinsertedintothetendonandfannedŽprox-imallyanddistally.Alternatively,theprocedurecanbeachievedwithmultipleinsertionsofa23-gneedle.Thismaycauselessdamagetotheremain-ing,relativelyintacttendontissue.Furthermore,needlesplittingmaybecombinedwithvariousin-tralesionaltreatments,althoughmultipleneedlein-jectionsmayprovokeleakageofthedrug/agentoutofthetendon.Aftertendonsplittinghasbeenperformed,amod-i“edRobertJonesbandageshouldbeapplied.Thehorseshouldberestedinaboxstallfor10…14days,subsequenttowhichacontrolledexerciseprogramshouldbeinitiated.2.DesmotomyoftheAccessoryLigamentoftheTheaimofdesmotomyoftheaccessoryligamentofthesuper“cialdigital”exortendon(orsuperiorcheckligamentdesmotomy(SCLD))istoproduceafunctionallylongermusculotendinousunittoreducestrainontheSDFT.However,ithasbeenshowninequinec

17 adavermodelsthatSCLDactuallyin-creasesth
adavermodelsthatSCLDactuallyin-creasesthestrainontheSDFTandSLduringload-ingbecauseofincreasedextensionoftheMCPThebiomechanicalalterationsofSCLDarecomplex,anditisrecognizedthatstudiesusingca-daverlimbsmaynotrepresentthebiomechanicaleventsinafatiguedgallopingracehorse.However,increasedriskofinjuryoftheSLaftertheSCLDhasbeenperformedhasalsobeenshowninvivo.AAEPPROCEEDINGSVol.542008491IN-DEPTH:TENDONANDLIGAMENTINJURY 2.SurgicalRepairSurgicalrepairof”exortendonlacerationsinvolvesdebridement,withorwithoutsuturingoftheten-don,andclosureofthewound,usuallyperformedundergeneralanesthesiainlateralordorsalrecum-bency.Theaimoftenorraphyistorestoretendonglidingfunction,minimizegapformationbetweenthetendonends,minimizeadhesionformation,andpreservefunctionalvasculature.Ifthelacerationiscomplete,thetendonmayhaverecoiled,requiringproximalanddistalextensionoftheskinwoundinanelongatedSŽtolocatebothtendonends.Flex-ingofthemetacarpal/metatarsaljointmayfacilitatelocatingofthedistaltendonend.Thewoundandtendonendsshouldbedebridedandlavaged.Ifthetendonendscanbeapposed,tenorraphycanbeper-formedusingamono“lamentabsorbablesuture(e.g.,polydioxanoneorpolyglyconate).Non-ab-sorbablematerialsshouldbeavoided,becausethiscanresultinshearingbetweenthehealedtissueandthesuturematerial.Itmayberesponsibleforper-sistentlameness.Twosuturepatternshavebeencommonlyused„thethree-looppulleyandthein-terlockingloop.Thethree-looppulleyisstrongest,anditpreventsdistractionoftheendsofthetendonunderloading(gappingŽ).Theinterlockingloophaslittlesuturematerialoutsidethetendon,anditis,therefore,therecommendedtechniqueforrepairofintrathecallacerations.Frequ

18 ently,however,theinjuryisassociatedwiths
ently,however,theinjuryisassociatedwithsigni“cantblunttraumatothetendonends,whichprecludesdirectappositionofthetendonends.Inthissituation,thetendonendsareleftafterde-bridement,thewoundisclosed,andthelimbiscast,oranimplantcanbeusedtomaintainthealignmentofthetendonends.Theidealtendonimplantma-terialwouldhavesimilarbiomechanicalpropertiestonormaltendon.Variousimplantmaterialshavebeenusedtorepairlacerated”exortendonsinclud-ingcarbon“ber,terylene(polyester),autologousex-tensortendongrafts,absorbabletendonsplints,andpoly-L-lacticacid(PLLA).Carbon“berimplantswereassociatedwithpersistentlamenesspostoper-atively.Thismayhavebeencausedbytenalgiathatresultsfromshearforcesbetweeninelasticcar-bon“bersandthehealedtendontissue.Autolo-gousgraftswithextensortendonscanbeusedtobridgethede“citbetweentwoendsofalaceratedtendon,butthistechniquehasnevergainedpopu-larity.PLLAhasanadvantageinthatitsupports“broblastgrowthonitssurfaceandlosesitsstrengthoverseveralmonths.Therefore,itisabletomatchitsmechanicalpropertieswiththetendon.Implantsareanchoredineachendofthelaceratedtendonby“xingtheendsinVincisionscreatedinthetendonendswithsuturesofmono“lamentab-sorbablesutures.Thetendonsplintshaveasemi-circularcross-sectionandcanbesuturedtothetendonendsthroughholesinthesplints.Implantsarenotrecommendedasatreatmentforstrain-inducedtendinopathies.Partiallacerationsinvolving50%ofthetendonmayneedonlylocaldebridement.Lacerationsin-50%ofthetendonareprobablybestsu-tured,becausethiscanpreventthegenerationoflongitudinalsplitsbetweenloadedandunloadedpartsofthetendonorthefailureoftheremainderofthetendonunderweight-bearingload.Flexortendonlaceratio

19 nsrequireaprotractedre-habilitationperio
nsrequireaprotractedre-habilitationperiod.Adistallimbcastshouldbeplacedwithforelimblacerationspost-operatively.Inthehindlimb,afulllimbcastisideallyrequiredafter”exortendonlacerationtoimmobilizetheforcesofthereciprocalapparatus.Distallimbcastscanbeusedinthehindlimbtoavoidthein-creasedriskofcomplicationswithfulllimbcasts.However,ifanimplanthasbeenplaced,thisusuallyresultsinoneendbeingpulledoutofthetendon.Castingisrequiredforaminimumof6…8wkandnomorethan10…12wk,becausestudieshaveshownthatthebreakingstrengthofthetendonrepairat6wkapproximatesthebodyweightofthehorse.Thismeansthatusuallyatleastonecastchangeundergeneralanesthesiaisneeded.Supportofthemetacarpal/metatarsaljointusingapalmar/plantarsplintwithamodi“edRobertJonesbandageandcaudalshoeextensions(forDDFTlacerations)canhelpprotecttherepairaftercastremoval.Continuedbox-stallrestisnecessaryforanadditional2…3moafterwhichwalkingexer-cisefollowedbyanascendingexerciseregimencanbeinitiated.Ultrasonographicmonitoringoftendonhealingisusefultoassesstheintegrityofthetendonrepair.Aminimumof8…12moisusuallyrequiredbeforefullathleticfunctioncanberesumed.Theprognosisfor”exortendoninjuriesisguarded.Inonestudy,45%returnedtoathleticwhereasinanotherstudy,theprognosiswas59%for”exortendonlacerations.Inthesecondstudy,theprognosisforreturntosoundnesswasnotincreasediftheDDFTandSDFTweresimulta-neouslylaceratedcomparedwithifonlyasinglestructurewaslacerated.Short-termcomplicationsincludenecrotictendonitis,whichoccursasaresultofinfectionordamagetothevascularsupply,con-currentsynovialsepsis,castcomplications,andex-uberantgranulationtissueformation.Long-termcomplicationsincludeadhe

20 sions,whichresultincontinuedpainandlamen
sions,whichresultincontinuedpainandlameness,andoccasionally,”ex-uraldeformity.Incontrasttothe”exortendons,extensortendonshealremarkablysuccessfullywithouttenorraphy,andtheyrespondwelltoconservativemanagement.Thewoundshouldbedebrided,andtheprimarywoundshouldbeclosed,ifappropriate.Iftheex-tensortendonhasbeenlaceratedwithinthecon“nesofatendonsheath(e.g.,forextensorlacerationsoverthedorsalaspectofthecarpus),lavageandelimina-tionofsepsisfromthetendonsheathalsoneedstobeaddressed.Theprognosisforextensortendon4942008Vol.54AAEPPROCEEDINGSIN-DEPTH:TENDONANDLIGAMENTINJURY 3.MesenchymalStemCellsStemcellshavethepotentialofdifferentiatingintoanumberoftissues.Embryonicstemcellsaretrulypluripotentialbuthavethedisadvantagesofbeingallogenic(althoughwithgreaterimmunologi-caltolerance)andbeingassociatedwithariskofteratomaformation.Postnatallyderivedstemcellsarethoughttobemultipotentialorhavearestrictednumberofcelllineagesintowhichtheycandiffer-entiate.Theyaresubdividedintohemopoietic(blood-celllines)andmesenchymalstemcells(MSCs),whichcangiverisetoosteoblasts(bone),chondrocytes(cartilage),tenocytes(tendonandlig-ament),“broblasts(scartissue),adipocytes(fat),andmyo“broblasts(myotubes).Furthermore,thesestemcellscanberecoveredfromadulttissue,andthus,thereisthepossibilityofautologousreim-plantation.Thisalsohastheaddedbene“tthattheydonotinciteanimmuneresponsefromthehost.Suchstemcellsaremosteasilyrecoveredfrombonemarrow,althoughotherworkersarecon-sideringtheuseoffat-derivedstemcells.Thesepreparationsare,however,lesswellcharacterizedatpresent.ThedifferentiationoftheMSCsintotenocytesisbelievedtobeinducedbyacombinationofmechan-i

21 cal(tension)cues,growthfactors,andcontac
cal(tension)cues,growthfactors,andcontactwithlikeŽcellsandmatrix,most,ifnotall,ofwhichareprovidedbyimplantationwithinthetissue.ThereiscurrentlymuchinterestintheuseofstemcellstoengineerŽnewtissue.Clinically,MSCsarecurrentlybeingusedforthetreatmentofischemicheartdiseaseinmanwithencouragingre-sultsofsurvivalandincreasedcardiacoutput.ThetransplantationofMSCsintoinjuredskeletaltissueshasbeenshowntopromotehealinginamultitudeofstudiesinexperimentalanimals.Intendon,studieshaveusedsurgicallycreateddefectsintendonsandligamentsoflaboratoryanimalsandhaveallshownsigni“cantlyimprovedoutcomeswiththeimplantationofbonemarrowTheequineSDFTinjuryhasadifferentetiopatho-genesis.However,itisidealfortheimplantationofMSCs,becausethereisusuallyanencloseddefectwithinthetendonthatcanretainimplantedMSCswithouttheneedforascaffold.Thereareseveraltechniquescurrentlyemployedclinically:directadministrationofbonemarrow,useoffat-derivedstemcells,andautologousimplan-tationofMSCs.1.Thedirectintraligamentous(orintratendi-nous)administrationofbonemarrowhasbeenreportedtoshowpromisingresultsinthetreatmentofSLdisease.thereareveryfewMSCspresentinabone-marrowaspirate(1MSCper10cells),whichhasledsometosuggestthatthistreatmentmoreresemblesagrowth-factortreatmentthanatruecell-basedther-apy.Certainly,thesupernatantofbonemarrowhasbeenshowntocontainarichmixofanabolicfactors.Furthermore,theinjectionoflargevolumes(20…30ml)cannotbefullyretainedinthestructure,andto-getherwiththepresenceofothercelltypesandtissues(e.g.,bonespicules),itcanpo-tentiallybedamagingtothehealingtendonorligament,especiallybyinducingectopic2.TheabovetechniqueusingBM-MSCshasrecei

22 vedthemostbasicscienceresearchandaimstop
vedthemostbasicscienceresearchandaimstoprovideapuresource;however,Vet-intheUnitedStateshasusedanothersourceofstemcellsfromfat(Fig.15).Thistechniqueinvolvescollectingfatfromthe Fig.14.fPRPsystemforpreparingplasmarichinplatelets.Thissystemusesa“ltrationsystemforconcentratingtheplate-letsratherthancentrifugation,anditisaclosedsystemthatcanbeusedhorseside.Ž4962008Vol.54AAEPPROCEEDINGSIN-DEPTH:TENDONANDLIGAMENTINJURY tailhead,digestingthetissue,andremovingthefatcells.Thisleavesamixtureofcellsthatincludestheadipose-derivedstemcells2%),whichareshippedbacktotheveter-inarianwithoutfurtherpuri“cationforin-tratendinousinjections.3.Incontrast,wehavebeendevelopinganalternativeapproachinvolvingtheimplan- Fig.16.TheVetCelltechniqueforthetreatmentoftendonandligamentinjurieswithautologousBM-MSCs. Fig.15.TheVet-Stemsystemforthetreatmentoftendonandligamentinjurieswithfat-derivedcells.AAEPPROCEEDINGSVol.542008497IN-DEPTH:TENDONANDLIGAMENTINJURY however,remainedinferiortonormaltendonbutimprovedwithexercise.Sincetheinitialtrial,inexcessof500horseshavebeentreatedwiththistechnique.Atthemostre-centevaluationofclinicaloutcome(September2007),172racehorseshadbeentreatedwith1yrfollow-up.ForNationalHuntracehorses(nthereinjuryratewas18%(23%wheninjuriestoun-treatedcontralaterallimbswereincluded).Whenonlythosehorsesthathadenteredfulltrainingwereincluded,thereinjuryrateroseslightlyto24%(33%withcontralateralreinjuries).Thesepercentageshaveremainedrelativelyconstantforupto3yraftertreatment,althoughnumbersaresmallforthelongestfollow-up.However,thesedatacomparefavorablywithpreviousanalysesforthesamecategoryofhorse(56%reinjuryrateforNa

23 tionalHunthorses)foranalysisofhorsesused
tionalHunthorses)foranalysisofhorsesusedforthesamedisciplinefollowedfor2yrafterareturntofullwork.Infurthersupportforthisimprovementinoutcome,reinjuryratesforsportshorses(alldisciplinescombined;n109with1yrfollow-up)wasimprovedbyasimilardegree(13%comparedwith23…43%reportedfordifferentsport-horsedisciplinesWeproposedthattheoptimumtimetoimplantthecellsisaftertheinitialin”ammatoryphasebutbefore“broustissueformation.Itwashypothe-sizedthatthepresenceofmature“broustissuewithinthetendonwould(1)makeimplantationmoredif“cultand(2)reducethebene“tsofthestem-celltherapybecauseofitspersistence.Bothhavebeensupportedbyclinicalexperienceofdelayedim-plantationofBM-MSCsandoutcome.Successeshadanaverageintervalbetweeninjuryandimplan-tationof44days,whereashorsessufferingreinjuryhadanaverageintervalof83days(pCurrentrecommendationsarethatbonemarrowisaspiratedwithin1moofinjury.Forthesamerea-son,knownrecurrentinjuriesarenotconsideredidealcases,becausesigni“cant“brosiswouldal-readybepresent.Thetimeofimplantationmaybefurtheroptimizedbypre-injurystorageofcells.Fivecasesthatdiedthroughunrelatedcauseshavebeenanalyzedhistologicallyandshowedexcel-lenthealingwithminimalin”ammatorycellsandcrimpedorganizedcollagen“bers.Incontrast,acontralateraluntreatedSLinjuryinoneofthesehorses,whichwasclinicallysilentatthetimeofimplantation,showedpersistentin”ammatorycellsandpoorlyorganizedcollagen“bers.Amorelimitednumberofcaseshavebeentreatedwithinjuriestoothertendonsandligaments.Forlesionspresentwithinatendonsheath,theimplan-tationisdoneaftertenoscopicevaluationtoensurethattherearenosurfacedefectsthroughwhichthecellscouldleak.10.ConclusionsTheexten

24 sivenumberoftreatmentsavailableforthetre
sivenumberoftreatmentsavailableforthetreatmentoftendonandligamentinjuriespro-videsstrongevidencethatnoneareuniversallyef-fective.Becauseofthenaturalvariabilityofthedisease,carefulandobjectiveassessmentoflargenumbersofcasesisessentialtoproveef“cacyofatreatment.Treatmentshouldbeselectedbystageandseverityofdisease,useofhorse(racingisstillthemostseveretestforaneffectivetreatment),andfollow-uptime(reinjuriestendtooccurwhenthehorseisbackracingbutnotbefore).Thismeansthatstrongevidence-basedtreatmentscannotbeprovided.Thetwomostimportantaspectsareto(1)obtainanaccuratediagnosisofwhichstructureisinjured,includingthestageandseverity,and(2)applytreatmentsbasedonastrongscienti“cratio-nalewithrespecttothepathophysiology.Cur-rently,combinationsoftreatmentsmayofferthebestapproach(e.g.,stem-celltreatmentandSCLD).However,inmanycases,costimplicationsmayalsoin”uencethechoiceofcombinationtreatments.ReferencesandFootnotes1.GenoveseRL,RantanenNW,SimpsonBS,etal.Clinicalexperiencewithquantitativeanalysisofsuper“cialdigital”exortendoninjuriesinThoroughbredandStandardbredVetClinNorthAm[EquinePract]1990;6:129…2.SmithRKW,WebbonPM.Diagnosticimaging„musculo-skeletalultrasonography.In:HodgsonDR,RoseR,eds.Theathletichorse.1992.3.AvellaCS,ElyER,VerheyenKLP,etal.Ultrasonographicassessmentofthesuper“cialdigital”exortendonofNationalHuntracehorsesintrainingovertworacingseasons.VetJ2008.Inpress.4.DikKJ,DysonSJ,VailTB.Aseptictenosynovitisofthedigital”exortendonsheath,fetlockandpasternannularligamentconstriction.VetClinNorthAm[EquinePract]5.DikKJ,vandenBeltAJ,andKegPR.UltrasonographicevaluationoffetlockannularligamentconstrictionintheEquin

25 eVetJ6.SmithRKW,WebbonPM.Softtissueinjur
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26 macherJ,etal.Useofabioabsorbableimplantf
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27 illerBJ,etal.Plateletrichplasma(PRP)enha
illerBJ,etal.Plateletrichplasma(PRP)enhancesanabolicgeneexpressionpatternsin”exordigitorumsuper“cialistendons.JOrthopRes25:230…240.73.SchnabelLV,MohammadHJ,JacobsonMS,etal.Effectsofplateletrichplasmaandacellularbonemarrowongeneexpres-sionpatternsandDNAcontentofequinesuspensoryligamentexplantcultures.EquineVetJ2008;40:260…265.74.WaselauM,etal.Intralesionalinjectionofplatelet-richplasmafollowedbycontrolledexercisefortreatmentofmid-bodysuspensoryligamentdesmitisinStandardbredrace-JAmVetMedAssoc75.RichardsonLE,DudhiaJ,CleggP,etal.Stemcellsinveterinarymedicine„attemptsatregeneratingequinetendonafterinjury.TrendsBiotechnol2007;25:409…416.76.SmithRK.Mesenchymalstemcelltherapyforequineten-DisabilRehabil2008:1…7.[Epubaheadof77.SmithRK,KordaM,BlunnGW,etal.Isolationandimplan-tationofautologousequinemesenchymalstemcellsfrombonemarrowintothesuper“cialdigital”exortendonasapotentialnoveltreatment.EquineVetJ2003;35:99…102.78.SmithRK,WebbonPM.Harnessingthestemcellforthetreatmentoftendoninjuries:heraldinganewdawn?BrJSportsMed79.TaylorSE,SmithRK,CleggPD.Mesenchymalstemcelltherapyinequinemusculoskeletaldisease:scienti“cfactorclinical“ction?EquineVetJ80.HerthelDJ.Enhancedsuspensoryligamenthealingin100horsesbystemcellsandotherbonemarrowcomponents,in.47thAnnualAmericanAssociationofEquinePractitionersConvention2001;319…321.81.SmithJJ,RossMW,SmithRK.Anabolicaffectsofacellularbonemarrow,plateletrichplasma,andserumonequinesuspensoryligament“broblastsinvitro.VetCompOrthop2006;19:43…47.fPRP,VetCellBioscience,CambridgeCB223AT,UnitedKingVet-Stem,Poway,CA92064.BathAP,Unpublisheddata,2003.AAEPPROCEEDINGSVol.542008501IN-DEPTH:TENDO