Lecture 14: Laminitis Flashcards
The ___phalanx is suspended by the laminae inside of a hoof capsule
Third
When the laminae of the foot are weakened by injury the normal forces on the digit cause ___
Shearing/tearing of the laminae which results in slipping of the digit inside the hoof capsule downwards and rotation from pull of DDFT
What are the clinical signs of laminitis
- Lameness (usually front feet)
- Stiffness
- Weight shifting
- Reluctance to move
- Worse on turns
- Increased hoof temp
- Increased digital pulses
- Sensitivity to hoof tester
- Hoof wall changes
What is a grade 1 on the obel grading scale
Shifting weight, but no apparent lameness at the walk, stilted trot
What is grade 2 for laminitis
Willing to walk but have stilted gait and can pick up foot if asked
Wha is grade 3 laminitis
Reluctance to ambulate resistant to having foot picked up
What is grade 4 laminitis
Horse reflexes to move, cant lift foot or down, can’t stand
What are some causes of laminitis
- Endocrinopathic (equine metabolic syndrome, Cushing)
- Enzymatic (SIRS, endotoxemia)
- Support limb overload
- Black walnut toxicity
- Steroid induced
- Heat induced
What model do we use to study endocrinopathic laminitis
Hyperinsulinemic model
What model do we use to study enzymatic associated laminitis
Starch overload
What is the pathophysiology of enzymatic laminitis
Accumulation of leukocytes in lamellar tissue, matrix metalloproteases are unregulated and cause basement membrane damage
What is the pathophysiology endocrinopathic laminitis
Lamellar epithelial cell stretching
What is the pathophysiology of support limb laminitis
Load cycling through walking or shifting weight when standing helps maintain blood flow to lamellar tissue, if not using one limb and offloading on others it will induce laminitis in the limbs that are supporting weight
How do you dx laminitis and describe procedure
Radiographs- stand horse on blocks and take lateral and DP views
What are some abnormal findings in acute laminitis radiographs
- Jet line- edema over laminae
- Possible to have no overt changes
What are some abnormal findings for chronic laminitis on radiographs
- Ski tipping of p3
- Loss of parallel between dorsal hoof wall and dorsal P3
- Medial to lateral asymmetry
- Sinking
What wrong and what do you see
Laminitis- not parallel, ski tipping, sinking
Where do you measure for founder distance and what is normal measurement
Coronary band to extensor process
Normal: 2-15mm
What does the founder distance determine
Presence of sinking if length increased
What does the Cobb angle determine
Rotation, hoof wall and dorsal P3 should be parallel
What is normal Cobb angle
0
What is the normal sole depth
15-20mm
What is normal dorsal wall thickness
<18-20mm
What is normal palmar angle
3-10 degrees
Identify the measurements indicated by the blue, purple, green, yellow, orange and black lines
blue: founder distance
Purple: Cobb angle
Green: wall thickness
Orange: palmar angle
Yellow: sole depth
Black: bony alignment
which normal vs abnormal and what is wrong
Left: normal
Right: laminitis
What are venograms
Vascular contrast study of foot
To do a venogram you inject radiopaque contrast into the ___to evaluate the arterial and venous structures of the digit
Palmar digital vein
With laminitis what does venogram look like
Venous compression and distortion of vascular structures
normal or abnormal
Normal
How do you perform a venogram
- Abaxial block
- Tourniquet above fetlock
- Contrast injected into palmar digital nerve
- Immediately a LM and DP rads taken
- Foot is lifted for solar projection and then repeat LM and DP after being unweighted
All films must be taken within 45 seconds of dye injected
What areas are evaluated in venogram
- Terminal arch
- Coronary papillae that make up coronary plexus
- Sublamellar vascular bed
- Circumflex vessels
- Lamellar circumflex junction with terminal papillae
Identify 1-5 and red arrow
- Coronary papillae/ coronary plexus
- Sublamellar plexus
- Terminal papillae
- Terminal arch
- Heel vessels
Red arrow: circumflex vessels
Venograms are useful to determine ___ or ___
Progress or deterioration
A return to normal of a venogram within the first __weeks indicates an excellent chance for return to use
4weeks
Which normal vs abnormal
Left: abnormal- decreased blood supply
Right: normal
What are the pharmacological treatments for acute laminitis
- Phenylbutazone/ NSAID
- DSMO
- Pentoxyphylline
- Acepromazine
- Opioids- butorphanol/ fentanyl patches
- Anticoagulant therapy- heraprin
What is dose for phenylbutazone to tx acute laminitis
2.2-4.4mg/kg IV or PO q12hrs
How does DSMO work
Free radical scavenger that aids in reduction of edema and may reduce ischemia
What is dose for DSMO to tx acute laminitis
0.1-1gram/kg IV q12-24 hrs diluted to <10% to avoid hemolysis
How does pentoxyphylline work
Phosphodiesterase inhibitor that alters RBC membranes to make them more deformable and improve blood flow. Also anti-inflammatory
How does acepromazine work to tx acute laminitis
Increases digital blood flow and relaxes them
What is dose for acepromazine to tx acute laminitis
0.03-0.06mg/kg IM or IV q6-8hrs
What anticoagulant can you give to tx acute laminitis and what does it do
Heparin- reduces micro-thrombi that may compromise vasculature in foot
What are some physiological treatments for acute laminitis
- Farrier care- elevate heel with wedge, deep bedding, trim toes (maintain sole depth though)
- cryotherapy
- Frog support
- Stall rest, lie down
You can perform a ___ for rotating laminitis (not sinking) as a salvage therapy
DDT tenotomy
What two structures do we need to reduce tension on when tx acute laminitis
DDFT (elevate heal)
Suspension apparatus (stall rest)
What is the prognosis for acute laminitis
Wait and see if respond to tx
Perform venogram
What ix tx for chronic laminitis
Farrier care and control underlying disease
What is most common cause of chronic laminitis
Endocrinopathic laminitis- Cushing or equine metabolic syndrome
What should farrier do to tx chronic laminitis
- Realign bony column: remove excess toe and heel
- Shortened cycle, every 2-4 weeks
what drug do you give to tx PPID/cushings associated laminitis
Prascend
What drugs do you give to tx insulin dysregulation causing laminitis
Metformin, levothyroxine
What diet should horses be fed to manage chronic laminitis
Low starch <10% NSC
Caloric restriction for weight loss
What drugs can be given to tx chronic laminitis
NSAIDS
1. Phenylbutazone
2. Firocoxib
What is dose for firoxoxib when managing chronic laminitis
0.1mg/kg PO q24
