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evaluation of lameness at the lunge

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kevin keegan

on 23 December 2014

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Transcript of evaluation of lameness at the lunge

Starke et al., Vet Journal , 2012
sound horses (hard ground)
vertical head and pelvic movement asymmetric
more downward movement of head and pelvis on outside limbs






more hip hike on inside hind limb





this would appear like inside forelimb and hind limb lameness
EVALUATING LAMENESS BY LUNGING THE HORSE
WHY?
Easier than trotting in straight line
Thought to exacerbate lameness
Bilateral conditions seen
Helps localize lameness within the limb???
Questions/Difficulties
Does it exacerbate lameness?
Some horses do not lunge well
Is lunging to the right different than lunging to the left?
BIOMECHANICS OF THE LUNGE
Horse are tilted when lunging
up to 18 degrees when trotting at moderate speed on a 10 m circle (Clayton et al., EVJ Suppl. 2006, Hobbs et al., EVJ 2011)
Centripetal force (ground friction) puts shear stress on the limbs
When lunging MCIII and MTIII inclination (tilt to inside) up to 18-19 degrees at the trot and 26 degrees at the canter
Starke et al., Vet Journal , 2012
great variability in left and right directions within horse
thus the inside and outside limbs "see" difference forces
inside limb (increased abaxial compression)
outside limb (increased axial compression)
University of Missouri Study
96 horses (mixture of sound and mild lame)
soft ground
forelimb
lunging to left
maxdiffhead negative (horse throws head up more at end of right [outside limb] stance
mindiffhead positive (head moves down more during right [outside limb] stance
i.e. looks like an
outside forelimb end-of-stance lameness
lunging to right
maxdiffhead positive
mindiffhead negative
i.e. looks like an
outside forelimb end-of-stance lameness
hind limb
lunging to left
maxdiffpelvis positive (pelvis thrust upward less) after pushoff of right [outside] hind limb
mindiffpelvis negative (pelvic fall less on left [inside] hind limb
i.e. looks like an
outside hind limb pushoff and inside hind impact lameness
lunging to right
maxdiffpelvis negative
mindiffpelvis positive
i.e. looks like an
outside hind limb pushoff and inside hind limb impact lameness
.
Hobb et al. EVJ 2011
TAKE HOME MESSAGE
not all lameness evaluations need lunging
not all horses should be lunged during a lameness evaluation
compare lunge left to lunge right before making a decision
keep "conditions" (size of circle) same
"threshold" of asymmetric movement should be raised
be wary of inside limb lameness on hard ground and outside limb lameness on soft ground
SOME OTHER THINGS WE LEARNED
forelimb lameness was exacerbated
hind limb lameness was masked
Detection of Lameness During the Lunge, with Flexion Tests, and Under Saddle
Flexion Tests
Why do we use flexion tests?
to isolate lameness to a limb
to isolate lameness within a limb
in pre-purpurchase evaluations
Ramey (100 forelimb flexion tests in 50 sound horses)
all horses with lameness or gross physical abnormality were rejected from the study
all horses with positive flexion tests re-examined 60 days later
normal vs "firm" flexion for 60 seconds
Ramey flexion study - results
normal flexion - 40% positive
firm flexion - 98% positive
only 2 horses with positive normal flexion developed lameness later
no relationship between radiographic abnormality and positive flexion
Kansas State Study - hind limb flexion tests
5 vs 60 seconds
more likely to respond positively to 60 seconds flexion test
Missouri Study - hock flexion
used objective measures (cameras and markers)
normal horses - 60 second test
even horses without hock-centered lameness were positive for up to 5 strides after the flexion test
TAKE HOME MESSAGE
flexion tests useful - with caveats
be careful when using during pre-purchase evaluations
not for localizing the lameness within the limb
use blocking
use fairly short and "not firm" test
THANK YOU FOR LISTENING
Detecting Lameness Under Saddle
Why would a horse be more lame under saddle?
increased weight on limbs
increased back flexion
poor saddle fit
Why would a horse be less lame under saddle?
training
excitement
Comparing Lameness in Hand to Lameness Under Saddle at the Trot
88 horses
sound, lame (natural/induced)
Results.....
it depends
parameters that are more important
rider activity (posting)
going straight or turning
surface
Effect of Posting
makes horse appear lame on opposite site
most dramatic effect is opposite hind (pushoff)
Riding in a circle has same effect of lunge
on hard ground
appears "off" on inside limbs
on soft ground
appears "off" (pushoff type) on outside forelimb
hip hike (impact type) on inside hind limb
hip dip (pushoff type) on outside hind limb
These Effects are Additive
posting on right (outside) limb on soft ground
will mask an outside hind limb lameness
posting on right (outside) limb on hard ground
will induce/exacerbate an inside hind limb lameness
rider sitting trot
rider posting on left limb
Rational Approach to Lameness Evaluation
Keep it simple
lunge only if lameness not seen (or measured) in straight
flexion tests only if lameness not seen without
ride only if lameness not seen (or measured) without rider
try to find a single primary problem (principle of parsimony; Occum's razor)
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