Equine Laminitis Flashcards
What is laminitis? What does it lead to?
inflammation of the lamina of the hoof wall
loss of adherence between hoof capsule and coffin bone
What is the difference between sinking and rotational laminitis?
SINKING = distal displacement with circumferential displacement
ROTATIONAL = dorsal displacement
What are the 3 major cases of laminitis?
- ENDOCRINE - equine metabolic syndrome, insulin resistance, PPID, corticosteroid administration
- INFLAMMATION - endotoxemia, sepsis, SIRS (colitis, retained placenta), endothelial/vascular dysfunction, black walnuts
- MECHANICAL - compensatory, excessive concussion
What is indicative of equine metabolic syndrome? What are 4 sequelae?
regionalized/generalized obesity - cresty neck, base of tail, near prepuce or mammary tissue, near shoulder (easy keepers)
- insulin resistance
- changes to foot/lamina
- infertility in mares
- hypertriglyceridemia
What causes pasture-associated laminitis? When is this most commonly seen?
grasses with high levels of nonstructural carbohydrates - lush/actively growing or stressed when environmental conditions restrict forage growth
spring > fall > mid-summer
What causes PPID? What 7 signs are associated?
pituitary adenoma causes an increase in ACTH in horses >15 y/o
- delayed shedding - long, wavy coat
- muscle wasting
- weight loss with regional adiposity
- PU/PD
- immune system dysfunction - difficulty controlling infections
- laminitis
- insulin dysregulation
What causes steroid-induced laminitis? How does dose affect outcome?
high doses of glucocorticoids has an effect on lamina mediated by insulin in horses with insulin resistance
- HIGH dose Triamcinolone - hyperglycemia, hyperinsulinemia, divergent growth rings
- NORMAL dose Dexamethasone - hyperinsulinemia in insulin sensitive ponies, no increase in normal ponies
How should horses that need to be treated with high doses of intra-articular corticosteroids be handled? What other treatments can be considered?
- low risk to develop laminitis, but inform client
- test horses for PPID, EMS, and IR, and if positive control disease before intra-articular injections
- use lowest dose possible
Equioxx (Firocoxib), ProStride, IRAP
What are the proposed mechanisms of elevated insulin, obesity, and metabolic disturbances causing endocrinopathic laminitis?
increased laminar failure
adipose tissue releases pro-inflammatory cytokines, increased weight bearing, insulin resistance
takes lower insulin level to push them over the edge into a laminitic crisis
What are some proposed ideas of why endotoxemia/septicemia causes laminitis?
- hypoperfusion
- systemic inflammation - marked inflammatory response distant to source of infection (SIRS) where the laminar endothelium acts as an end organ
- tissue damage amplified inflammation
What causes inflammation associated with SIRS in cases of endotoxemia?
neutrophil matric metalloproteinases cause degradation of the basement membrane, which leads to separation of the laminae
What causes vascular dysfunction associated with endotoxemia?
venoconstriction + microthrombi (coagulopathy vs. secondary effect)
How does compensatory laminitis progress?
- vascular dysfunction from mechanical overload
- horse requires shifted of weight to encourage venous return (1-5x/min)
- decreased venous return if the horse is unable to shift and bears weight continuously
- congestion leads to platelet activation, microthrombi formation, and ischemia
What are the 4 stages of laminitis?
- prodromal - no signs
- acute - heat in hoof, increased digital pulse, lameness, founder stance, NO rotation - hindlimbs move forward to take weight off
- subacute - begin rotation of P3
- chronic - clear rotation of P3, reduction in pain as inflammation resolved
What 7 clinical signs are associated with laminitis?
- heat in hooves
- shifting weight
- elevated DP
- founder stance
- reluctance to move
- walked heel to toe
- P3 comes out of the bottom of the foot - consider human euthanasia
What is seen with palpation with “sinkers” in cases of laminitis?
distal displacement of coffin bone causes a space to form where the coffin joint usually is
What are the 4 Obel grades of of laminitis?
- at rest, the horse shifts weight between forelimbs; horse is sound at a walk, but gait is stilted at the trot when turning
- gait is stilted at the walk and horse turns with difficulty, but one forelimb can be lifted
- horse is reluctant to walk and one forelimb can only be lifted with great difficulty
- horse only moves if forced to
What radiograph views are required for diagnosing laminitis? How is the hoof prepared?
lateral and DP of P3
- dorsal hoof wall marker, no need to remove shoes to pack foot
- distal alignment of P3 in all planes (not the coffin joint)
- level surface straight through the shoe to see sinking medially
- include entire hoof capsule
What are the 5 normal values evaluated on hoof radiographs?
- founder distance - <8 mm
- P3 rotation - <2 degrees
- wall thickness - 16-18 mm
- sole depth - 20 mm
- palmar angle - 3-5 degrees
How is the sole dept measured? What is the normal value?
from tip of P3 to bottom of the sole
~20 mm
(green)
How is the palmar angle measured? What is the normal value? What is ideal?
angle of bottom of P3 to the ground
3-5 degree in front, 5-7 degree in rear –> depends on breed and use of horse
a line that bisects P1, P2, and P3 (50-53 degrees in front, 53-55 degrees in rear)
What does the angle of the dorsal hoof wall measure? What is normal?
measures P3 rotation
parallel - difference should be <2 degrees, use angle to ground to determine
(pink)
What is the founder distance? What is normal? What does it measure?
coronary band to extensor process of P3
<8mm –> measures sinking
How is the wall thickness measured? What is normal? What horses have a naturally thicker measure?
distance from P3 to dorsal hoof wall directly under the extensor process and at the toe of P3
15-18mm - measures rotation
SB, draft horses - 20-22 mm
Normal vs laminitic hoof:
medial sinking
What measurement is not affected by trimming? Which one is?
founder distance
P3 rotation
How is venography used to diagnose laminitis? How is it done?
visualizes blood flow within the foot to determine prognosis –> filing defects indicate lack of perfusion
- inject contrast into peripheral vein
- tourniquet leg to keep contrast within the foot
- take radiographs within 45 seconds before the contrast clears
Venogram:
no fill past extensor process over dorsal P3
What are 4 common causes of false venogram results?
- inadequate contrast injection
- waited too long to take the radiograph
- difficulty finding peripheral vessel
- tourniquet not tight enough
What bony column support is recommended in cases of laminitis? What are 5 options?
axial support to decrease lever on lamina at the toe and pull of DDFT
- pull does - rasp nails on the ground to relief pressure on unstable wall
- impression material or styrofoam on palmar 2/3, multiple layers added q 24 hours
- wooden clogs
- orthotics
- sand stall or deep bedding
(take weight off wall and put it on frog and sole)
What are 2 aspects to wooden clogs used to treat laminitis? What do they do?
- screwed on - less painful than nails
- has multiple angles - weight shifting, comfortable breakover point
elevates heel to reduce pull of DDFT
What are the 2 major parts of treating chronic laminitis?
- weight loss
- corrective shoeing - reduce weight bearing on walls and toe, short toe to ease breakover and reduce pull on DDFT, elevate heel, leave sole
How is a DDF tenotomy approached? What is prognosis like?
above DFT sheath to leave more distal sites as an option
salvage procedure
