Exam 2 - Equine Laminitis

Question 1

what is laminitis?

Answer 1

inflammation of the lamina - disruption/inflammation of the lamina

the lamina hold the distal phalanx to the hoof wall circumferentially, so loss of this attachment results in rotation and/or sinking of the distal phalanx

Question 2

what is rotation in regards to laminitis?

Answer 2

loss of parallelism of the hoof wall with the dorsal aspect of the distal phalanx causing pinching of the circumflex artery

mild: 3-5°

moderate: 5-10°

severe: >10°

Question 3

what horses are more commonly affected by laminitis?

Answer 3

minis, ponies, & donkeys

Question 4

what clinical signs are seen in a horse with acute laminitis?

Answer 4

acute, severe lameness ‘walking on eggshells,’ carrying their weight on the hind end

sensitive to hoof testers over toes

increased to bounding digital pulses

typically bilateral front feet - less common, but can be bilateral hind feet, rare unilateral cases

rare in foals

Question 5

what are the most important radiographic views for diagnosing laminitis?

Answer 5

lateral & dorsopalmar views

Question 6

what is founder?

Answer 6

layman’s term for laminitis - sampson reserves this term for laminitis with rotation

Question 7

how is laminitis diagnosed?

Answer 7

clinical signs - history, physical exam, digital pulses, + hoof testers

block to abaxial nerve - often not needed to diagnose in severe cases, but can confirm with blocking

Question 8

what block should you use for a horse you suspect has laminitis? why?

Answer 8

abaxial sesamoid block - can use to get better radiographs

sometimes can’t get their feet off the ground to put in soft rides without blocking them

Question 9

what does an abaxial sesamoid block desensitize? what nerves are you hitting?

Answer 9

entire foot/pastern & part of the fetlock - medial & lateral palmar/plantar nerves

Question 10

where is an abaxial sesamoid block performed?

Answer 10

lateral & medial palmar aspect of the foot just distal to the fetlock using 2-3 mLs of carbocaine

Question 11

what are some recognized risk factors for laminitis?

Answer 11

obesity, carbohydrate overload, steroids/systemic steroids, endotoxemia

intra-articular steroids - triamcinolone implicated

PPID, black walnut shavings

trimmed too short

severe lameness in opposite limb - support limb laminitis because of mechanical overload on the contralateral limb

Question 12

T/F: in laminitis, mild to severe lameness is seen depending on the stage of disease in horses

Answer 12

true

Question 13

if the front feet of a horse are affected by laminitis, how will they carry their weight?

Answer 13

back end

Question 14

this stance is characteristic for laminitis in what feet?

Answer 14

front feet - weight is shifted back

Question 15

what is the pathogenesis of laminitis?

Answer 15

laminar disintegration is mediated by uncontrolled release of excessive activated MMP (strep bovis implicated)

enzymatic destruction of laminae resulting in the loss of basement membrane integrity

ischemic necrosis of laminae - no force to oppose the pull of DDFT

if not controlled, can result in distal phalanx penetrating through the sole at the toe, typically resulting in euthanasia

Question 16

what is the prognosis of this horse with laminitis that has resulted in sole penetration?

Answer 16

euthanasia

Question 17

what clinical signs are associated with acute laminitis in horses?

Answer 17

severe lameness

bounding digital pulses

normal external hoof wall

extreme hoof tester sensitivity over toes

walking on egg shells

Question 18

what clinical signs are associated with chronic laminitis in horses?

Answer 18

variable lameness

increased digital pulses

dished external hoof wall with horizontal rings - foot becomes upright with a tall heel & stretched white line

none to moderate hoof tester sensitivity over the toes

Question 19

what is the treatment indicated for acute laminitis in horses?

Answer 19

emergency!!!!

soft ride boots - easiest

ice the affected distal limbs - cold stops MMP enzyme activity

phenylbutazone - anti-inflammatory, very important

pentoxyphylline - increases blood flow in tortuous vessels

acepromazine - vasodilation

Question 20

what is the treatment indicated for chronic laminitis in horses?

Answer 20

shoeing to support caudal half of foot & shorten toe (clogs, heart bar, reverse heart bar shoe)

phenylbutazone or equioxx as needed

manage weight - do not want an obese horse, more risk

manage type/amount of feed - low starch diet

Question 21

what are the goals of shoeing for managing chronic laminitis?

Answer 21

1. unweight the sole at the toe & support the foot at the heel
2. increase the heel angle - wedge heel up
3. protect the sole of the foot from concussion

Question 22

what materials are used for shoe management in chronic laminitis horses?

Answer 22

soft ride boots, clogs, heart bar shoes

Question 23

what shoe material is this?

Answer 23

clogs - has to be screwed on or put on by a farrier or veterinarian

Question 24

what type of shoe is this? what is it used for?

Answer 24

heart bar shoe - managing chronic laminitis horses

Question 25

what are these? what are they used for?

Answer 25

soft ride boots - managing chronic laminitis horses

$230/pair, velcro on

Question 26

what is seen on this radiograph that is supportive of laminitis?

Answer 26

dorsal aspect of P3 is no longer parallel with the hoof wall

rotational/sinking

Question 27

this stance is the common clinical presentation of what?

Answer 27

acute laminitis - walking on eggshells stance

Question 28

T/F: laminitis is rare in foals

Answer 28

true

Question 29

what structure is responsible for rotation of the coffin bone away from the hoof wall in laminitis?

Answer 29

deep digital flexor tendon

Question 30

what are the 2 mechanisms that promote the misalignment of the coffin bone within the hoof capsule when laminar disruption occurs?

Answer 30

1. rotation of the coffin bone - loss of parallelism, due to the pull of the DDFT
2. sinking of the coffin bone - collapsing down within the hoof capsule, due to the full weight of the horse

Question 31

what is seen on this radiograph that is supportive of laminitis?

Answer 31

coffin bone sinking - parallel P3/dorsal hoof wall still seen, but decreased distance of the ventral aspect of P3 to the sole surface!!!

Question 32

is this rotational or sinking laminitis?

Answer 32

rotational, loss of parallelism from dorsal aspect of P3 & hoof wall