Equine studies Flashcards
Stages of assessing a lame horse
1) Take a history
2) Perform full clinical exam
3) Lameness examination
4) Diagnostic analgesia via nerve blocks
5) Further diagnostics
Definition of lameness
Change in gait usually in response to pain somewhere in the limb but also possibly as a result of a mechanical restriction on movement
- Rare to be due to mechanical restriction
What to be aware of that may be confused for lameness
Neurological elements; need to do a neurological examination if this is suspected
Spotting forelimb lameness
Look for asymmetry in gait
Head nod is main factor: head goes up when lame leg hits the ground to keep weight off (‘down on sound’)
Stride length: can look like shuffling; shorter cranial phase
- Can look like shuffling
Irregular rhythm of a trot; less loud bang from lame leg
Spotting hindlimb lamesness
Looking for an asymmetrical pelvic tilt/hip movement
- Hip hike: pelvis will be lifted when the lame leg hits the floor
Stride length changes: back leg won’t track up well; won’t reach footprint of the front leg
Interpreting compensatory lameness
Where there is a change in weight distribution due to lameness which can be misinterpreted
e.g Hindlimb lameness can cause compensatory load redistribution onto the contralateral forelimb
- SO: head goes down when contralateral forelimb goes down
(see head nod and pelvic tilt)
This can be misinterpreted as an ipsilateral forelimb lameness as well as hindlimb
Two scales used for lameness
- 1-10 scale: most UK vets use this; grade walking, trotting and circle trotting separately
Where 1-3 is mild, 4-6 is moderate, 7-10 is severe - 0-5 scale: incorporate degree of lameness and trot into one grade
Where 0 = sound and 5 = non-weight bearing lame
What are flexion tests in lameness diagnosis
Use to apply pressure to set regions of the limb i.e flexing joints to stress it
- Then trot the horse up after this test and re-grade the lameness
For forelimb can do individual joints or whole limb at once
For hindlimb will flex the whole limb at one time due to stay apparatus
What is diagnostic analgesia
Used to localise the source of pain to a specific limb region/joint using local anaesthetic to desenstise the area
Requirements for doing diagnostic analgesia in a lame horse
Horse should be consistently and sufficiently lame such that any improvement in gait can be detected
Differences in site preparation in nerve vs joint blocks
In perineural blocks, the area must be very clean but doesn’t need to be sterile
In joint blocks need completely sterile preparation to avoid septic joint
What is the most popular drug used for diagnostic analgesia
Mepivicaine: rapid onset; lasts 2-4 hours
Prilocaine used for other nerve blocks e.g dentals but doesn’t last long enough for a multiple block testing work up on horses
Why don’t we use lidocaine on horses
Because it has adrenaline as an additive in the UK
This formulation can cause white hair formation, dehiscence, tissue ischemia and necrosis
Restraint for blocking
Ideally don’t want sedation as horse needs to be trotted up; want experienced handler + lip/neck twitches
May use chemical restraint: usually Xylazine as this has a short duration of action so analgesia won’t last
Can also use low dose acepromazine for restraint as it has no analgesia and doesn’t cause sedation (just tranquiliser); so won’t affect lameness interpretation
When to never do a nerve block
If you suspect the bone could be fractured
Horse will put weight on during block and break the leg
