lecture 7 - the equine digit

AAEP56thAnnualConvention:Baltimore,Maryland2010

Dr.KathrynCarmalt,DVM,MSc,BA,AS,-slidescourtesyofDr.Anderson

UNIVERSITY OF SASKATCHEWAN Saskatoon, Saskatchewan, Canada. www.usask.ca

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

Essentially these animals stand on just 1 finger or toe.

¡  Commonterm=knee§  Conformationterminology

¡  Jointcommunication§  Separate▪  Radiocarpal

§  Alwayscommunicate▪  Middlecarpalandcarpometacarpal

¡  Whatis“communication”

¡  Whydoescommunicationmatter?§  Diagnosis,prognosis,treatmentoptions

If you injected a dye into 1 joint space will it end up in another joint.

Radiocarpaljointl

Middlecarpaljoint

Carpometacarpaljoint

The carpal joint has 3 joint spaces

Bigger joint spaces have larger ranges of motion than smaller joint spaces

Radius

Metacarpal III & Splint Bones (MT II, IV).

Accessory Carpal

Seperate

Always Communicate

IntermediateRadial

UlnarAccessory

Fourth

Third

Second

SometimesFirst

The Carpus

¡  Commonterm=hock¡  Jointcommunication

§  Alwayscommunicate▪  Tibiotarsal,talocalcaneal,andproximalintertarsal

§  Sometimescommunicate▪  Distalintertarsalandproximalintertarsal

§  Usuallycommunicate▪  Distalintertarsalandtarsometatarsal

Hindlimb

TibiotarsalJoint

TalocalcanealJointProximalIntertarsalJoint

DistalIntertarsalJointTarsometatarsalJoint

Tibiotarsal, Talocalcaneal, and Proximal Intertarsal joints will always communicate.

Distal Intertarsal and tarsometatarsal joints also communicate w/ eachother

The Tarsus

Calcaneus

TalusCentraltarsal

Fourthtarsal

Thirdtarsal

First/secondtarsal

¡  Commontermformetacarpal/metatarsal3=Cannonbone

¡ MC3isoneofthestrongestbonesinthehorse’sbody

¡  Severelystressedduringatheleticuse§  Adapts!OR§  Breaks!

Common term for metacarpal/metatarsal 3 = cannon bone.MC3 is one of the strongest bones in the horse’s body. Severely stressed during

Condylar fracture - commonly occurs in race horses

Common term for metacarpal/metatarsal 3 = cannon bone.MC3 is one of the strongest bones in the horse’s body. Severely stressed during

Condylar fracture - commonly occurs in race horses

¡  CommontermforMC/MT2&4=Splintbone§  Vestigialstructuresthatstillsupport(akasplint)!▪  OnlyMT4mayberemovedenblocwithoutde-stabilizingajoint

§  ConnectedtoMC/MT3viafibrousinterosseousligaments

The splint bones act to stabilize the joint above.MT4 = lateral splint bone

The splint bones act to stabilize the joint above.MT4 = lateral splint bone

“”Buttons”ofthesplint

Cannon Bone

Cannon Bone

MC/MT3=Cannonbone

MC/MT2=Medialsplintbone

MC/MT4=Lateralsplintbone

Lateral View

Cranial View

Purple arrows - nutrient foramens - blood supply.

Lateral View

Cranial View

Purple arrows - nutrient foramens - blood supply.

¡  Commonterm=fetlockjoint¡  Commonsiteofinjury

§  Racehorses§  Jumpers

¡  Highmotionjoint§  Almost180°

Outline around a fragment (P1 fractures) usually occurs medially, but can occur laterally. It is a common issue with race horses.

Fetlock joint is a common site of injury that occurs when the horse is landing.

Outline around a fragment (P1 fractures) usually occurs medially, but can occur laterally. It is a common issue with race horses.

Fetlock joint is a common site of injury that occurs when the horse is landing.

Hyperextension Flexion

Extension Hyper-extension Straight Flexion

MC/MT3

ProximalSesamoidBones

P1

cannon bone

proximal phalanx

cannon bone

proximal phalanx

¡  Firstorproximalphalanx§  Commonterm=longpasternbone

¡  Secondormiddlephalanx§  Commonterm=shortpasternbone

¡  Thirdordistalphalanx§  Commonterm=coffinbone

¡  Proximalinterphalangealjoint§  Commonterm=pasternjoint§  Lowmotionjoint▪  Arthrodesis

¡  Distalinterphalangealjoint§  Commonterm=coffinjoint§ Moderatemotionjoint§  Closetonavicularbursaandflexortendonsheath

fusing the joint - reduces the motion - cannot be an athlete but is not painful anymore.

P3

P2

P1

fusing the joint - reduces the motion - cannot be an athlete but is not painful anymore.

P3

P2

P1

P1

P3

P2

Proximalinterphalangealjoint

Distalinterphalangealjoint

Both of these joints can be injected. You can also palpate these joints.

Both of these joints can be injected. You can also palpate these joints.

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

Samantha Bray

A painful tendon is very painful.

A painful tendon is very painful.

¡  Frontlimbvs.Hindlimb§  Front:Commondigitalextensorandlateraldigitalextensortendonsareseparate

§  Hind:LongdigitalandlateraldigitalmergetoformtheCDET

¡  Cantransectcompletelyandhorsecanreturntoathleticuse

Samantha Bray

Dorsal aspect of the leg

Can be injured and recover from it.

Dorsal aspect of the leg

Can be injured and recover from it.

¡ Majorflexorofthedigit¡  FrontLimb

§  Stayapparatusandsuspensoryapparatusofdigit

¡  HindLimb§  Partofcommoncalcanealtendon§  Reciprocalapparatusandsuspensoryapparatusofdigit

¡  Experienceshighstrainatspeed

Samantha Bray

Flexor tendons is more important.

Flexor tendons is more important.

MC3 MC3

Skin SkinSDFT

Tendon Injuries

Bone - 4 monthsTendon - 6 months Ligament - 8 months(think of # of letters in the word to see how long it will take to heal)

fluid

Cross section

Longitudinal Section

Tendon Injuries

Bone - 4 monthsTendon - 6 months Ligament - 8 months(think of # of letters in the word to see how long it will take to heal)

fluid

Cross section

Longitudinal Section

¡  Almostexclusivelyaforelimbproblem

¡  LocalizedtoMid-Metacarpalregion

¡  Seeninracehorses(43%!),eventhorses,dressage,jumpinghorses,poloponies

Samantha Bray

¡  Majorflexorofthedigit¡  Stayapparatusandsuspensoryapparatusofthedigit

¡  Bi-lobedinpasternregion

¡  Hindlimb§  Crossesmedialalongsustenaculumtalioftalus

Samantha Bray

Bilobed in the pastern region. It attaches to the coffin bone (P3) - plays a key role in the rotation seen in laminitis.

Bilobed in the pastern region. It attaches to the coffin bone (P3) - plays a key role in the rotation seen in laminitis.

¡  Akainterosseousmuscle§  Verylittlemusclefiberinlargeanimals§  Connectsbonetobone=ligament

¡  Partofthesuspensoryapparatus§  Passive:DOESNOTFLEXJOINTS

¡  Brokendowninto4anatomicalareas§  Proximal§ Mid-body§  Branches§  Extensorbranches

Samantha Bray

Proximal - attaches to proximal palmar surface of MC3. It is involved in proximal suspensory desmitis. It happens because its most likely to tear at the attachment point.

Proximal - attaches to proximal palmar surface of MC3. It is involved in proximal suspensory desmitis. It happens because its most likely to tear at the attachment point.

¡  Commoncauseofsofttissueinjurytolimbs

¡  Comprises60%ofsoft-tissueinjurieslocalizedtoproximalMC/MT

¡  Sporthorses

¡  Hindlimb>Forelimb

Samantha Bray

¡  Anyplaceatendoncrossesajointorbonyprotuberance

¡ Mostimportantinthedistallimbisthedigitalflexorsheath§  COMMONLYinvolvedinwounds

FrontLimb

Nodifferencebetweenhindand

frontlimb

Begins:Distal1/3ofcannonEnds:Withinhoofatnavicularbone

Blue - tendon sheath

Blue - tendon sheath

Medialview:Tarsus

SDF

DDF

CalcanealBursa

TarsalSheathCunean

ligament&bursa

MC3

MC2 MC4

SDFTDDFT

SuspensoryligamentInferiorcheckligament

Commondig.extensorLateraldig.extensor

MC3

MC2 MC4

ClinicalanatomyoftheHorse

Cannon bone

MC2 and MC4 are splint bones

cranial

plantar

Cannon bone

MC2 and MC4 are splint bones

cranial

plantar

Flexortendonsheath

Commondig.extensorLateraldig.extensor

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


¡  Palmar/PlantarAnnularligament§  Supportstendonsandligamentscrossingthepalmaraspectofthefetlock

§  Canresultina“carpaltunnel-like”syndrome

¡  Collateralligaments§  Minimumofmedialandlateralonalljoints

Commondigitalextensortendon

Palmarannularligaments

Extensorbranchofsuspensoryligament

Branchofsuspensoryligament

DDFT

SDFT

Buttonofsplint


palpable

palpable

Innervation of the equine digit

forelimb

forelimb

Ulnar Median

Caudalantebrachium

Medialantebrachium

MedialPalmar

LateralPalmar

Dorsalbranch

Craniomedialantebrachium

MedialCutaneous

Antebrachial

Musculocutaneous

Medialmetacarpal

Lateralmetacarpal

Cutaneousinnervation

MedialMedial

Lateral Lateral

PalmarView DorsalView

Palmar

Dorsal

DDFT

SDFT

SL

MC3

MC2MC4

CDET

Medial Lateral

PalmarView

Palmar Digital Block

Palmar digital nerve has a medial and lateral side - must block both.This blocks caudal heel pain.

You know its working when the heel is desensitized (in the coronary band). It does not desensitize the dorsal part of the coronary band.

Can help you distinguish between navicular disease or laminitis.

Palmar digital nerve has a medial and lateral side - must block both.This blocks caudal heel pain.

You know its working when the heel is desensitized (in the coronary band). It does not desensitize the dorsal part of the coronary band.

Can help you distinguish between navicular disease or laminitis.

Medial Lateral

PalmarView

Abaxial Block

This nerve block desensitizes the whole foot.

Can help you rule out laminitis.

This nerve block desensitizes the whole foot.

Can help you rule out laminitis.

Cutaneoussensation

Musculocutaneous

Ulnar

Median

Radial

innervates extensor muscles - however no sensation in the digit.

medial cranial sensation

Lateral

Caudal Fetlock Area

innervates extensor muscles - however no sensation in the digit.

medial cranial sensation

Lateral

Caudal Fetlock Area

SaphenousCraniomedialtibia Cranialtibia Caudaltibia

Peroneal Tibial

DeepPeroneal

MedialDorsal

Metatarsal

LateralDorsal

Metatarsal

LateralPlantar

CaudalCutaneous

Sural

MedialPlantar

SuperficialPeroneal

LateralPlantar

Metatarsal

MedialPlantar

Metatarsal

Deepbranch

Cutaneousinnervation

PlantarView DorsalView

Lateral

Lateral

MedialMedial

Dorsal

Plantar

more extensive dorsal innervation compared to the forelimb

more extensive dorsal innervation compared to the forelimb

Cutaneoussensation

SaphenousPeroneal/Fibular

Tibial

craniomedial

craniolateral

caudal hindlimb and dorsal fetlock area

craniomedial

craniolateral

caudal hindlimb and dorsal fetlock area

¡  Dorsaltopalmar/plantarorderofneurovascularbundle§  Vein,artery,nerve=VAN

¡  Nomuscleinlowerlimbandlimitedvenous/lymphaticdrainage§  Physiologicconsequences

Need motion to pump the lympatics back up to the heart.

Need motion to pump the lympatics back up to the heart.

¡  Besuretopalpatestructureslistedonlabhandout§  Alargepartofequinepracticeisspentpalpatinglimbs!

CephalicVein MedianArtery RadialArtery

LateralPalmar

Metacarpal

MedialPalmar

Metacarpal

LateralPalmarDigital

LateralPalmar

MedialPalmar

MedialPalmarDigital

LateralPalmar

MedialPalmar

LateralPalmarDigital

MedialPalmarDigital

PalmarDigitalVein

PalmarView PalmarView

LateralMedial LateralMedial

MedialView LateralView

Easilypalpable

Saphenousa.&v.Tibiala.&v.

DorsalPedala.

DorsalMetatarsala.DorsalCommon

Digitalv.

LateralPlantara.&v.

MedialPlantara.&v.

LateralPlantarDigitala.&v.

MedialPlantarDigitala.&v.

¡  Partofthestayapparatus§  Superior▪  Stabilizesthesuperficialdigitalflexormusculotendinousunit▪  AttachesSDFMTunittothedistalcaudomedialradius▪  Nosuperiorcheckinhindlimb

§  Inferior▪  Stabilizesthedeepdigitalflexortendon▪  AttachesDDFTtoproximalsuspensoryligament▪  Variableinhindlimb

Superiorcheck

Inferiorcheck

Cranial

ClinicalAnatomyoftheHorse

Questions?

lecture 7 - the equine digit

Health & Medicine