lecture 7 - the equine digit
TRANSCRIPT
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AAEP56thAnnualConvention:Baltimore,Maryland2010
Dr.KathrynCarmalt,DVM,MSc,BA,AS,-slidescourtesyofDr.Anderson
UNIVERSITY OF SASKATCHEWAN Saskatoon, Saskatchewan, Canada. www.usask.ca
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Skeleton Biggest evolutionary change is a reduction in number of digits/metatarsal bones • Digit I is lost, then V,
then II, then IV • Horses have a
complete Mt III and vestigial Mt II and IV
Dr. L. Hudson
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¡ Commonterm=knee§ Conformationterminology
¡ Jointcommunication§ Separate▪ Radiocarpal
§ Alwayscommunicate▪ Middlecarpalandcarpometacarpal
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¡ Whatis“communication”
¡ Whydoescommunicationmatter?§ Diagnosis,prognosis,treatmentoptions
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Radiocarpaljointl
Middlecarpaljoint
Carpometacarpaljoint
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IntermediateRadial
UlnarAccessory
Fourth
Third
Second
SometimesFirst
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The Carpus
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¡ Commonterm=hock¡ Jointcommunication
§ Alwayscommunicate▪ Tibiotarsal,talocalcaneal,andproximalintertarsal
§ Sometimescommunicate▪ Distalintertarsalandproximalintertarsal
§ Usuallycommunicate▪ Distalintertarsalandtarsometatarsal
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TibiotarsalJoint
TalocalcanealJointProximalIntertarsalJoint
DistalIntertarsalJointTarsometatarsalJoint
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The Tarsus
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Calcaneus
TalusCentraltarsal
Fourthtarsal
Thirdtarsal
First/secondtarsal
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¡ Commontermformetacarpal/metatarsal3=Cannonbone
¡ MC3isoneofthestrongestbonesinthehorse’sbody
¡ Severelystressedduringatheleticuse§ Adapts!OR§ Breaks!
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¡ CommontermforMC/MT2&4=Splintbone§ Vestigialstructuresthatstillsupport(akasplint)!▪ OnlyMT4mayberemovedenblocwithoutde-stabilizingajoint
§ ConnectedtoMC/MT3viafibrousinterosseousligaments
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“”Buttons”ofthesplint
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MC/MT3=Cannonbone
MC/MT2=Medialsplintbone
MC/MT4=Lateralsplintbone
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¡ Commonterm=fetlockjoint¡ Commonsiteofinjury
§ Racehorses§ Jumpers
¡ Highmotionjoint§ Almost180°
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Hyperextension Flexion
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Extension Hyper-extension Straight Flexion
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MC/MT3
ProximalSesamoidBones
P1
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¡ Firstorproximalphalanx§ Commonterm=longpasternbone
¡ Secondormiddlephalanx§ Commonterm=shortpasternbone
¡ Thirdordistalphalanx§ Commonterm=coffinbone
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¡ Proximalinterphalangealjoint§ Commonterm=pasternjoint§ Lowmotionjoint▪ Arthrodesis
¡ Distalinterphalangealjoint§ Commonterm=coffinjoint§ Moderatemotionjoint§ Closetonavicularbursaandflexortendonsheath
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P1
P3
P2
Proximalinterphalangealjoint
Distalinterphalangealjoint
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Tendon Innervation and Blood Supply
In general poor blood supply – and well innervated
However, there is still wide individual variation • The Superficial Digital Flexor Tendon (SDFT) has a blood
supply similar to resting muscle and can increase blood flow after injury and during exercise - Kraus BLH, Kirker-Head CA, Kraus KH, et al: Vascular supply of the tendon of the equine deep digital flexor muscle within the digital sheath. Vet Surg 24:102, 1995
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¡ Frontlimbvs.Hindlimb§ Front:Commondigitalextensorandlateraldigitalextensortendonsareseparate
§ Hind:LongdigitalandlateraldigitalmergetoformtheCDET
¡ Cantransectcompletelyandhorsecanreturntoathleticuse
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¡ Majorflexorofthedigit¡ FrontLimb
§ Stayapparatusandsuspensoryapparatusofdigit
¡ HindLimb§ Partofcommoncalcanealtendon§ Reciprocalapparatusandsuspensoryapparatusofdigit
¡ Experienceshighstrainatspeed
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MC3 MC3
Skin SkinSDFT
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¡ Almostexclusivelyaforelimbproblem
¡ LocalizedtoMid-Metacarpalregion
¡ Seeninracehorses(43%!),eventhorses,dressage,jumpinghorses,poloponies
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¡ Majorflexorofthedigit¡ Stayapparatusandsuspensoryapparatusofthedigit
¡ Bi-lobedinpasternregion
¡ Hindlimb§ Crossesmedialalongsustenaculumtalioftalus
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¡ Akainterosseousmuscle§ Verylittlemusclefiberinlargeanimals§ Connectsbonetobone=ligament
¡ Partofthesuspensoryapparatus§ Passive:DOESNOTFLEXJOINTS
¡ Brokendowninto4anatomicalareas§ Proximal§ Mid-body§ Branches§ Extensorbranches
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¡ Commoncauseofsofttissueinjurytolimbs
¡ Comprises60%ofsoft-tissueinjurieslocalizedtoproximalMC/MT
¡ Sporthorses
¡ Hindlimb>Forelimb
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¡ Anyplaceatendoncrossesajointorbonyprotuberance
¡ Mostimportantinthedistallimbisthedigitalflexorsheath§ COMMONLYinvolvedinwounds
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FrontLimb
Nodifferencebetweenhindand
frontlimb
Begins:Distal1/3ofcannonEnds:Withinhoofatnavicularbone
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Medialview:Tarsus
SDF
DDF
CalcanealBursa
TarsalSheathCunean
ligament&bursa
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MC3
MC2 MC4
SDFTDDFT
SuspensoryligamentInferiorcheckligament
Commondig.extensorLateraldig.extensor
MC3
MC2 MC4
ClinicalanatomyoftheHorse
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Flexortendonsheath
Commondig.extensorLateraldig.extensor
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Flexor insertions
(palmar view) Suspensory ligament
Superficial digital flexor tendon
Deep digital flexor tendon insertion on P3
Superficial flexor digital tendon insertion on P2 and P1
ClinicalanatomyoftheHorse
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¡ Palmar/PlantarAnnularligament§ Supportstendonsandligamentscrossingthepalmaraspectofthefetlock
§ Canresultina“carpaltunnel-like”syndrome
¡ Collateralligaments§ Minimumofmedialandlateralonalljoints
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Commondigitalextensortendon
Palmarannularligaments
Extensorbranchofsuspensoryligament
Branchofsuspensoryligament
DDFT
SDFT
Buttonofsplint
ClinicalanatomyoftheHorse
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Innervation of the equine digit
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Ulnar Median
Caudalantebrachium
Medialantebrachium
MedialPalmar
LateralPalmar
Dorsalbranch
Craniomedialantebrachium
MedialCutaneous
Antebrachial
Musculocutaneous
Medialmetacarpal
Lateralmetacarpal
Cutaneousinnervation
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MedialMedial
Lateral Lateral
PalmarView DorsalView
Palmar
Dorsal
DDFT
SDFT
SL
MC3
MC2MC4
CDET
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Medial Lateral
PalmarView
Palmar Digital Block
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Medial Lateral
PalmarView
Abaxial Block
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Cutaneoussensation
Musculocutaneous
Ulnar
Median
Radial
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SaphenousCraniomedialtibia Cranialtibia Caudaltibia
Peroneal Tibial
DeepPeroneal
MedialDorsal
Metatarsal
LateralDorsal
Metatarsal
LateralPlantar
CaudalCutaneous
Sural
MedialPlantar
SuperficialPeroneal
LateralPlantar
Metatarsal
MedialPlantar
Metatarsal
Deepbranch
Cutaneousinnervation
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PlantarView DorsalView
Lateral
Lateral
MedialMedial
Dorsal
Plantar
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Cutaneoussensation
SaphenousPeroneal/Fibular
Tibial
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¡ Dorsaltopalmar/plantarorderofneurovascularbundle§ Vein,artery,nerve=VAN
¡ Nomuscleinlowerlimbandlimitedvenous/lymphaticdrainage§ Physiologicconsequences
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¡ Besuretopalpatestructureslistedonlabhandout§ Alargepartofequinepracticeisspentpalpatinglimbs!
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CephalicVein MedianArtery RadialArtery
LateralPalmar
Metacarpal
MedialPalmar
Metacarpal
LateralPalmarDigital
LateralPalmar
MedialPalmar
MedialPalmarDigital
LateralPalmar
MedialPalmar
LateralPalmarDigital
MedialPalmarDigital
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PalmarDigitalVein
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PalmarView PalmarView
LateralMedial LateralMedial
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MedialView LateralView
Easilypalpable
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Saphenousa.&v.Tibiala.&v.
DorsalPedala.
DorsalMetatarsala.DorsalCommon
Digitalv.
LateralPlantara.&v.
MedialPlantara.&v.
LateralPlantarDigitala.&v.
MedialPlantarDigitala.&v.
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¡ Partofthestayapparatus§ Superior▪ Stabilizesthesuperficialdigitalflexormusculotendinousunit▪ AttachesSDFMTunittothedistalcaudomedialradius▪ Nosuperiorcheckinhindlimb
§ Inferior▪ Stabilizesthedeepdigitalflexortendon▪ AttachesDDFTtoproximalsuspensoryligament▪ Variableinhindlimb
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Superiorcheck
Inferiorcheck
Cranial
ClinicalAnatomyoftheHorse
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Questions?