Laminitis - Causes + consequences Flashcards
What is laminitis?
- Inflammation of the lamellae causing lameness
Where does the horn grown from?
- From the coronary band
What is the anatomy of the sole of the hoof?
- No lamellae on sole
- Weight bearing on lamellae, frog + walls of hoof - not sole
What is the blood supply of the foot? (GLucose)
- V well vascularised - single hoof uses more glucose per day than its brain
- Glucose uptake not insulin mediated
- Glucose needed to keep basement membrane structures intact
What are different theories of laminitis?
- Endotoxemic\sepsis\inflammatory theory
- Carbohydrate overload theory
- Supporting limb laminitis
- Mechanical laminitis
- Corticosteroid induced laminitis
- Endocrinopathic laminitis
What is the theory of endotoxin causing laminitis?
- Laminitis recognised as complication of SIRS / endotoxaemia in horses
e.g. - RFM, colitis, post colic surgery, pleuropneumonia - Relevance = hospitalised horses
What is the supporting limb laminitis?
- Horses non-weight bearing in one limb will often develop laminitis in the contralateral limb - due to failure of circulation + tissue ischaemia
- Relevance = hospitalised horses
What is mechanical laminitis?
- Any force that tears hoof from laminae
- V traumatic one off or chronic forces on weakened digit
What is glucocorticoid induced laminitis?
- Glucocorticoid administration can cause laminitis
- Relevance = owners should know there is a risk with corticosteroid use
What is carbohydrate overload laminitis?
- Excessive carbs = overwhelms SI + overspills into large bowel = bacterial proliferation causes acidosis causing release of variety of laminitis inducing substances
What sugars used by plants do horses struggle to digest leading to overspill to large bowel + causing bacterial proliferation + laminitis?
- Fructans - mammals lack enzymes to digest it = bacteria feast on the sugars
What is endocrine induced laminitis?
- 90% of laminitis have underlying endocrinopathy =
-equine metabolic syndrome (EMS)
-pituitary pars intermedia dysfunction (PPID)
-EMS + PPID together - Changes of horse having laminitis if it doesn’t have EMS or PPID is low
What is equine metabolic syndrome?
- Syndrome obesity, insulin dysregulation and laminitis.
- Thrifty” genotype leading to “survivor” phenotype enabling horses to survive in harsh conditions by putting on weight in good times to prepare for hard times.
- UK horses never experience “hard times” and so just get fatter and fatter…
- Lack of recognition of obesity in horse owners.
- Recent social trend to treat horses as “toys” causes welfare problems.
- Hyperinsulinaemia = cause of EMS related laminitis
How does hyperinsulinaemia cause laminitis?
- Damages cytoskeleton of laminar cells and also has vasoactive properties
How does PPID cause laminitis?
- Believed to be related it insulin dysregulation
- Older horses (>15y/o) - v common
What are consequences of laminar failure?
- Pedal bone is free to move within the foot
What is capsular rotation?
- Hoof capsule diverges from the dorsal surface of P3, but P3 itself still aligned with P2
What is bony rotation?
- The hoof capsule diverges form the dorsal surface of P3, and P3 itself is rotated palmarly around the DIP. Implies significant pull of DDF and usually a sign of severe damage
What are consequences of pedal bone movement?
- acute stage – gap forms where the bone was + becomes a haematoma/seroma /necrotic mess.
- If this gets infected a foot abscess will result.
- The forces on the foot stretch the white line junction – providing an easy ingress route for abscess –causing bacteria
- haematoma replaced by poor quality horn = lamellar wedge
- Rotation of pedal bone drags coronary band with it = crushed blood supply to coronary band
- Abnormal horn growth = diverging hoof rings
- Hoof remodels itself around new position of pedal bone = abnormal hoof shape = chronic lameness
