LamenessinRacehorsesPaulREarlFacultaddeCiencias专业知识课件

LamenessinRacehorses

PaulREarl

FacultaddeCienciasBiológicas

UniversidadAutónomadeNuevoLeón

SanNicolás,NL66451,Mexico

Millionsandmillionsofdollarsareinvolvedinhorselameness.Itiscausedmainlybyoverexerciseonhardsurfaces.

Thefirstpointisthat70%ofhorsesondirttrackshavefrontcannonboneproblems,whereas4.1timesless(17%)onturftrackshave.Thecannonboneisthemainfusedlegbone.Thesecondpointisthatmaturityisreachedat4-5yearsofage,andyoungbonesaresoft.Thisisanappealforallracetrackstoswitchfromdirttograss.

Racehorsesrunfartherastheygetolder,staringat¼or3/8thofamile(3furlongs)goingto2milesusually.Nonetheless,itisspeednotdistancethatcausesthedamage.Still,theownerofMano’Warat3yearsoldwinningthePreaknessat1¼andtheBelmontStakesat1½milesthoughttheKentukyDerbyata11/8mileswastoolongforhim!

Thereismoretoitthanifstakewinnersonly.Someownersonlywanttowinstakeraces.Thenthosehorsesthatcannotreacha“GallantFox”triplecrownstandardwillbesoldorcrippledorboth.

Themainsignoftroubleaheadisheatinthelegs.

Infraredthermogram.Whatisyourdiagnosis?Theanatomyofthelegs

SomeProblemswiththeHooves

SubsolarInfectionsarethecommonesthoofinfections,andcommoncausesofacutelameness.Apenetratingwoundinthesole,frogorwhitelinegenerallycausedbythehorsesteppingonasharpobjectlikeanailcausinglacerations.

BruisedSolesareoneofthemostcommoncausesoflamenessinbothshodandunshodhorses.Injurytothesolemaycausedamagetothesensitivestructuresunderneathandresultsinbruising.Theresultcanbedamagetothemanytinybloodvesselsunderneaththesoleandconsequenthemorrhage.Normalandcontractedheels

Splintsthatwerepartsofthetoesmillionsofyearsagocanmakeahorsefrom2to3yearslame.Theligamentbetweeneachsidebone--splint--andthecannonbonefusepossiblycausingatemporarysoreness.

Buckedshinsisaverycommonconditionpossiblycausedbymicrofracturesandthelikecausedinturnbyconcussionandstress.Thesurface,theperiosteum,mayseparatefromthefrontofthecannonboneintheprocessoflayingdownmorebone.Manytrainersforcethehorsetobuckasinevitable.Thisisdonebyfastworks,notgallopinglongdistances.

Thisscaleis:walk,jogortrot,gallop,breeze,workorrace.

DesmitisofSupportingLigamentslikethewithimparligamentandtheproximalsuspensoryligamentdesmitisisaseparatediagnosisfromnaviculardisease.Willsomeoftheselamehorsesdevelopinflammationanddegenerationofthenavicularbone?Suchhorsesareseparatedfromthosewithabnormalfluidinthenavicularbone,althoughafewhorseshavebothfluidintheboneanddesmitisofthesupportingligaments.Thesehorsesarediagnosedwithnaviculardisease.Thetreatmentisthesame,mainlydependingonrest..

Thrushisaninfectiveconditionofthefroganditssulciwhichresultsindegenerationofthehornandtheproductionoffoulsmellinggrey/blackdischarge.Insevereorneglectedcasestheinfectioncanspreadtoinvolvetheunderlyingcorium.Thedegenerationofthehornisduetoinfectionwithbacteriaandespeciallyfungi.Wetunhealthystableconditions,poorroutinefootcare,prolongedconfinement,overgrownraggedfrogsandlongorhighheelswhichproducedeepsulci.Mostoftheseconditionscanbecorrectedbyablacksmith.

NailPrickoccursatshoeingwhenanailpenetratesthelivestructuresofthefoot.Ithappensmostcommonlyifthehorseisrestlessorfractious,thehoofwallisparticularlythinorbroken,theshoeistoosmallorthehoofhasbeendumped.DumpingmeansDumpingisexcessiveraspingoftheoutsideofthewalllusuallyatthetoe,butitcanextendallthewayaroundthewall.NailBindoccurswhenthenailoftheshoeisdrivencloseto,butnotintothesensitivestructuresofthefootresultinginpressureandinflamation.

Tendonitis

Itisinflammationofthesuperficialdeepdigitalflexortendons(DDFT)oftenreferredtoasabowedtendonduetothebowedappearanceofthetendonsonthebackofthecannonbone.The“strap”thatcrossesthecannonboneinfrontistheextenderligamentTendonitisoftheDDFTisfairlyrare.

Thedamagecanrangefrommildtearingoftendonfiberstoactualruptureoftheentiretendonandthebone-attachedligaments.Tearsintendonsarebestdiagnosedbyultrasound.Tendonitisispredominatelyaforelimbproblem.The2primarycausesofsuperficialDDFTareeitheracutetraumaduetooverload,oracumulativedamageduetorepeateddamagetothetendons.Asidefrompoorconditioningandmisappliedracingbandages,highracingspeedcanbowahorse.

HyperextensionofthedistalinterphalangealjointasaresultofallowingthetoetogrowandthusrisemaycausechronicoracutetearingoftheDDFtendonfibers.

Normally,tendonsareelasticsothattheycanstretchwithroutineoverloading.Thisisreferredtoaselasticdeformation.ClinicalsignsofsuperficialDDFTincludeheat,tendonswelling(edema)andthickeningandlameness.X-rayimagesoflamehorseslikelyarelesseffectivethanultrasound.InflammationmaybebestdemonstratedbyIRphotographs.

Notethatinmanylatecasesofinflammation,antiinflammatarydrugsarecontraindicated,asinflammationspeedsupthehealingprocess.

Aftertendonfibersaretorn,hemorrhageresultsinbloodclotslikelyalongwithswellingandinflammation.Astheinflammationandthebloodclotssubside,scartissueformsintheplaceofthedisplacedfibers.

Typicalbowedtendon.ThishorsemightbecheckedforbonechipswithXrays.

Alowbowintheleftleg

Laminitis

Laminitis—inflammationofthelaminasofthefoot--isacommon,painfulandsometimesdisastrousconditionofthehorsehoofthathasalwaysbeenknown.Laminitisoccurswhenthecoffinbone(distalphalanx)andtheinneraspectofthehoofwallareseparated.

Nevertheless,ablacksmithcanlikelycureagivenproblemwithwellmanagedracehorses.Laminitisis—essentially—aproblemofneglectedhorses.

Bringthehoofandthecoffinbonebackintotheiroriginalpositionsthroughtrimming.Optimizebloodflowthroughthefootbyalittlewalkingorroping.Removingthecauseoflaminitis:overloadofthecoffinbone.

Thereare2kindsoflaminas.Dermallaminaegrowoutwardsfromthelaminardermisattachedtothecoffinbone.Theyaremadeoflivingconnectivetissuesthatfoldintoprimaryfinger-likestructures;eachoftheseinturnisfoldedintohundredsoffeather-likesecondarylaminas.Thesedermallaminasinterdigitatewithcorrespondingepidermallaminae,eachagainofprimaryandsecondarygenerations,thatprojectinwardfromtheinnerhornysurfaceofthewall,anchoringthecoffinbonetothehoofwall.Theamountoffoldinginthelaminasincreasesthesurfaceareaofbonding.Thebloodsupplytotheequinefootisunusual.Allarterieshavereceptorsintheirwallsthatcanbindspecificchemicalmessengerscirculatingthroughoutthebody.Thebindingofthesechemicalssomelikebradykinincausesthedilationorconstrictionofthearterieschangingtheamountofbloodreachingthetissues.Bloodrichintheoxygenandnutrientsnecessarytosustainlivingtissuesiscarriedinarteriesfromthehearttothehoof.Itthenpassesthroughacapillarybedinthedermiswhereoxygenandnutrientscandiffusetothecells.

Acutelaminitisoccursanywherefrom24to72hoursaftertheinitialdamagetothebasementmembraneandisheraldedbytheclinicalsignsofpain.Signsofacutelaminitisinclude:

1/severelameness,reluctancetomoveoreventorecumbency

2/typicalstancetotrytogetweightoffthetoes:frontfeetoutinfrontifonlytheforelimbsareinvolved;all4legsinunderthebodyifalllimbsareinvolved;pointingwithalegifonlyonelimbisinvolved

3/increaseddigitalpulsesarealmostalwayspresent

4/continuedheatinthefoot

DisposingFactorsinLaminitis:

Numerouspredisposingfactorshavebeenidentified.Theycanbedividedinto6majorgroups:

1/Highheels

2/Carbohydrateoverload:excessgrain,lushpasture,suddenfeedchange

3/Endotoxemia,sepsis,shock:colic,intestinalobstruction,pleuritis,retainedplacenta,metritis,abortion

4/Excessiveunilateralweightbearing:post-fracturerepair,severelameness

5/management:unconditionedanimalsworkedonahardsurface,coldwateringestionbyoverheatedhorse,overweightanimal

Therapy:

Thetreatmentofhorsesthatdevelopacutelaminitiscanbeconsideredanemergency.Adelayofevenafewhourscanmakethedifferencebetweenasuccessfuloutcomeandafailure.Ifanyoftheknownriskfactorsforlaminitishaveoccurred,therapyshouldbestartedbeforetheclinicalsignsbecomevisible.Thetreatmentshouldbefocusedonrestoringthecirculationofthehoofandofcoursethereattachmentofthelaminastothecoffinbone.Itisatleast8weeksbeforeprognosis.Inchroniccases,4monthstoayeararerequiredbeforefutureperformanceabilitiescanbeestimated.