Equine Anatomy Exam

clinical anatomy

what is diagnostic perineural anesthesia

nerve block

what are the 4 types of nerve blocks

palmar/plantar digital

abaxial sesamoid

low 4-point

high 4-point

why do we do nerve blocks

to dx lameness & to desensitize an area for sx

what is desensitized in a palmar/plantar nerve block

palmar/plantar 2/3 of foot

entire sole, navicular structures, distal interphalangeal joint, distal DDFT, distal sesamoidean ligaments

what is desensitized in an abaxial sesamoid nerve block “basisesamoid block”

foot, second phalanx, proximal interphalangeal joint, distopalmar/plantar aspect of proximal phalanx, distal portions of DDFT & SDFT, distal sesamoidean ligaments, digital annular ligament

v shaped area at front of P1 may not be blocked

what is desensitized in a low 4 point nerve block (proximal to fetlock)

metocarpo(tarso)phalangeal joint & structures distal

distal aspects of suspensory branches

what is desensitized in a high 4 point nerve block (below carpus)

medial & lateral plantar nerves (DDFT & SDFT)

medial & lateral palmar metacarpal nerves (MC2, MC4, prox suspensory ligament & origin)

inferior check ligament

why do we perform arthrocentesis

joint injections to tx arthritis

joint fluid sample to dx sepsis

joint lavage to dx communication w/ wound/laceration

joint lavage to tx sepsis

what is desensitized in distal interphalangeal joint

joint

navicular bursa

what is desensitized in metacarpo(tarso)phalangeal joint

joint

what are the names of the proximal row of carpal bones (medial to lateral)

radial, intermediate, ulnar

what are the names of the distal row of carpal bones (medial to lateral)

2nd, 3rd, 4th

what are the 3 joints of the carpus

radiocarpal (antebrachial) joint

middle/intercarpal joint

carpometacarpal joint

what two joints are the carpus are in communication with e/o

middle/intercarpal joint & carpometacarpal joint

“down in front”

identify the image

purple- radiocarpal joint

green- middle/intercarpal joint

blue- carpometacarpal joint

proximal row of carpal bones: radial, intermediate, ulnar

distal row of carpal bones: 2, 3, 4

(medial to lateral)

the accessory carpal bone is medial or lateral

lateral

what is desensitized in radiocarpal joint

joint

what is desensitized in middle/intercarpal joint

middle/intercarpal joint + carpometacarpal joint

the equine foot

P3 is suspended within the hoof by laminae

-epidermal laminae attached to hoof wall

-dermal laminae attached to P3

laminitis (founder)

inflammation of the laminae

degeneration of the laminae

can lead to rotation of P3 (more common) or sinking of P3 within hoof capsule (worse, can feel a depression)w

what is this condition

laminitis, rotation of P3

what is this

a normal hoof, note parallel angle

navicular disease

most common cause of chronic forelimb lameness

chronic degenerative condition of the navicular bone

-loss of medullary structure (+ lollipop synovial invaginations)

-bone sclerosis (hardening)

-enthesiophyte formation (excessive mineralization of soft tissue) on proximal and distal borders of the bone

-traumatic fibrilation of DDFT from contact w/ damaged flexor surface of the bone with adhesion formation btwn tendon and bone

what is this

a- normal

b- navicular dz w/ synovial invaginations (lollipops)

left vs right images

left: normal

right: navicular disease with loss of medullar architecture and increased synovial invaginations (lollipops) and damaged flexor surface (loss of mineralization)

what is this

arrow on left- enthesiophyte (rounded edge)

arrow on bottom- synovial invaginations

what is arrow pointing at on MRI

edema of the navicular bone

white spots on mri are indicative of pathology (bc of fluid, inflammation)

penetrating wounds of the foot

anything towards the frog: BAD

ungual/collateral cartilage, DDFT sheath (synovial structure), DDFT, navicular bursa (synovial structure), navicular bone, distal interphalangeal joint (synovial structure) P3

if damage to synovial structure, risk of infxn arises & considered an emergency

tendonitis

inflammation of the tendon

desmitis

inflammation of a ligament

tendonitis & desmitis

common injuries in horses, tendons and ligaments lack a good blood supply (but rather have scar tissue so more prone to recurrence) so these injuries take a while to heal

label equine distal limb ultrasound (top to bottom)

superficial digital flexor

deep digital flexor

check ligament

suspensory ligament

what is this

superficial digital flexor tendonitis

black round object on imaging= hematoma

what is this

left= normal

right= deep digital flexor tendonitis

yellow arrows= tear in deep digitial flexor tendon

what is this

left= normal

right= suspensory ligament desmitis

cloudyness (red arrow) is showing fluid injury

white lines on left image is normal for comparison

what is this

suspensory ligament desmitis

green is surrounding tear

on left side of MRI, bulging out is visible, hitting neurovascular bundle and causing pain

what tendons are torn for these lacerations (L to R)

SDFT only

SDFT & DDFT

SDFT, DDFT, & SL (completely plantigrade)

what are the bones of the tarsus

distal tibia, calcaneus + sustentaculum tali (fused), talus (+ medial and lateral trochlea), central tarsal bone, 3rd tarsal bone, 4th tarsal bone, fused 1 & 2 tarsal bone, proximal 2 3 and 4 metatarsal bones

joints of the tarsus

red- tibiotarsal (or tarsocrural)

green- proximal intertarsal

blue- distal intertarsal

purple- tarsometatarsal

which joints of the tarsus communicate w/ e/o

tibiotarsal and proximal intertarsal joints

which tarsal joints are the most common sites of arthritis in horses

distal intertarsal and tarsometatarsal

identify middle image

orange- medial trochlear ridge (of talus bone)

purple- lateral trochlear ridge (of talus bone)

blue= sustentaculum tali

green= chestnut

yellow= central tarsal bone

pink= 3rd tarsal bone

light purple= 4th tarsal bone

cream= fused 1 & 2 tarsal bone

red= metatarsal 2 and 4

what is desensitized in a tarsometatarsal joint block

joint

what is desensitized in a distal intertarsal joint block

joint

what is desensitized in a tibiotarsal joint block (dont hit saphenous vein)

tibiotarsal joint & proximal intertarsal joint (communicate w/ e/o)

stifle

bones- patella, distal femur (+ medial and lateral trochlear ridges), tibia

lateral trochlear ridge of femur is shorter and smaller than medial

soft tissue structures- 3 patellar lig (medial middle lateral), medial & lateral collateral lig

joints- femoropatellar, medial femorotibial, lateral femorotibial

what is desensitized with a femoropatellar joint block

joint, in 65% of horses it can communicate w/ medial femorotibial joint but youre never sure which horses so you treat them all separately

what is desensitized with a medial femorotibial joint block

joint, +/- communication w/ femoropatellar joint in some horses

what is desensitized with a lateral femorotibial joint block

joint

degenerative joint disease “arthritis”

a radiographic diagnosis

most common location in horse are distal tarsal joints: distal intertarsal, tarsometatarsal

what are the radiographic abnormalities that dx arthritis (in order of apperance)

osteophytes & enthesiophytes (bone spurs)

joint space thinning

subchondral bone sclerosis (more opaque)

periosteal proliferation (sunburst, more mineralized on surface of bone)

subchondral bone lysis (darker on rad)

ankylosis (joint fusion)

what is this

distal tarsal joint osteoarthritis (OA)

what is circled on image on the right

osteophyte (bone spur, body is trying to fuse joint)

patient has distal tarsal joint osteoarthritis

gastrocnemius lacerations, left to right

normal

gastrocnemeus only (plantigrade stance)

gastroc & SDFT → cannot stand

pathway for normal abdomen anatomy

esophagus→stomach→duodenum→jejunum→ileum→cecum(R side, blind ending sac)→right ventral colon→sternal flexure→left ventral colon→pelvic flexure→left dorsal colon→diaphragmatic flexure→right dorsal colon→transverse colon→small colon→rectum

what makes the horse a hind gut fermenter

large/ascending colon

difference btwn dorsal and ventral colons

dorsal= smooth

ventral= has sacculations (bumpy)

what is a common cause of colic

pelvic flexure impaction

sx→pelvic flexure enterotomy

normally, can feel at lower L of colon but when impacted it is very easily reached (at anus)

what is this

cecal impaction

sx→ typhlotomy

left dorsal displacement is aka

nephrosplenic entrapment

right dorsal displacement

pelvic flexure is high and on R side (normally low and L)

what is a large colon volvulus

twist on mesentery (location of blood vessels, cuts off supply & colon dies)

small intestine distension

blown up w/ fluid & gas, always feels abnormal (normally its smooth, texture is abnormal)

enterolith

stones of calcium and magnesium in intestine, common in southwest, usually in right dorsal colon theyre single

from transverse colon → small/descending colon theyre multiple

where does a nasogastric inubation occur

ventral nasal meatus (no ethmoid turbinates here)

what happens if you hit the carotid while getting a jugular stick

p will seizure

dental anatomy- triadan system

1-upper right

2-upper left

3- lower left

4-lower right

x01= first incisor

x04= canine

x05= wolf tooth

x08= last premolar

x09= first molar

paranasal sinuses

frontal

maxillary (rostral and caudal compartments)

sphenopalatine

dorsal conchal

middle conchal

ventral conchal

bold= clinically relevant

frontal sinus: ethmoid hematoma

mild, intermittent, unilateral, spontanous epistaxis (bloody nose)

smooth, glistening mottled green surface

unknown cause

maxillary sinuses

109/209 teeth communicate w/ rostral compartment

110/210 and 111/211 communicate w/ caudal compartment

tooth root infections =

secondary sinusitis

guttural pouch

paired extensions of the eustachian tubes

connects pharynx to middle ear

has various theorized functions

what divides the guttural pouch into medial and lateral compartments

stylohyoid bone

how does the guttural pouch communicate with the pharynx

through the nasopharyngeal orifice of the eustachian tube

this orifice also allows access to guttoral pouch w/ endoscope

what runs in the guttural pouch

external carotid artery (lateral compartment)

cranial nerves 9-12 and internal carotid a. (medial compartment, contained within a fold of mucous membrane on caudal wall)g

guttural pouch mycosis

fungal infxn caused by Aspergillus species

unilateral dz

no predisposition

diphtheritic membrane composed of necrotic tissue, cellular debris, bacteria, and fungal mycelia

can lead to severe & often fatal bilateral epistaxis

larynx endoscopic view

arytenoids, aryepiglottic fold, vocal folds, laryngeal saccule, epiglottis

laryngeal hemiplagia

half paralysis

aBduct- to move away from midline done by dorsal cricoarytenoid muscle (innervated by left recurrent laryneal nerve)

aDduct- move towards middline

jugular venipuncture

omohyoideus muscle, between carotid a and jugular v

muscle is thicker top 2/3 which will separate carotid and jugular for easier venipuncturegu

guttural pouch cranial nerves cause

9- dysphagia

10- facial paralysis

11- n/a

12- dysphagia