Lameness Flashcards
Important aspects of the standing examination
- consistent complete; always performed and documented in same way
- NOT BIASED by Hx…..unless horse is non-weight bearing lame, follow routine
Hoof conformation/angle problems
- sloping
- stumpy
- broken back
- broken forward
areas of hoof palpation
- frog
- coronary band
- heel bulbs
Lameness not perceptible under any circumstance
grade 0
Lameness is difficult to observe and is not consistently apparent, regardless of circumstances
grade 1
Lameness is difficult to observe at a walk or when trotting in a straight line but consistently apparent under certain circumstances
grade 2
Lameness is consistently observable at a trot under all circumstances
grade 3
Lameness is obvious at a walk
grade 4
Lameness produces minimal weight bearing in motion and/or at rest or a complete inability to move
grade 5
Flexion tests
- help localize source of lameness
- NOT factored into lameness score
- should not “block” off positive flexion test lameness alone
- perform and interpret consistently
- evaluate limb flexed AND opposite limb for increased lameness after weight-bearing
Wedge test with heel elevated is done to evaluate ______________
suspensory ligament
Wedge test elevating the toe is done to evaluate __________
- navicular structures
- DDFT
A wedge test placed to elevate one side of the foot is evaluating __________
collateral ligaments
Examples of mechanical gait abnormalities
- upward fixation of patella
- fibrotic myopathy
- stringhalt
- shivers
- ruptured peroneus tertius
Types of diagnostic analgesia
- Perineural = “nerve block”
- Intra-articular = “joint block”
Why are nuclear scintigraphy and thermography exceptions to the rule of performing blocks prior to imaging?
with these two modalities, any injection site will be “hot” regardless of pathology
What is the lowest nerve block?
Palmar/plantar digital (PD)
PD nerve block blocks:
- L & M palmar/plantar digital nerves; back of pastern below level of dorsal branches
(so heel, more than toe)
Abaxial (basisesamoid) nerve block blocks:
- L & M palmar/plantar digital nerves at level of sesamoid bones
Of the L&M artery, vein, and nerve, how do the structures go from lateral to medial?
L to M: VAN so nerves are most medial
Low 4 point - nerves blocked
- L&M palmar/plantar metacarpal/tarsal nn
- L&M palmar/plantar nn
Be cautious about what structure when doing low four point block?
digital flexor tendon sheath
Blocking the deep branch of the lateral plantar nerve is done for what purpose?
suspecting proximal suspensory disease
Local anesthetic considerations for blocks:
- Lidocaine: rapid onset but shortest duration (~1.5h)
- Mepivicaine: rapid onset and intermediate duration (~3h)
- Bupivicaine: intermediate onset but longest duration (6-8h)
Preparation of joint/tendon sheath blocks and nerve blocks close to joints
- sterile preparation (4-5 min contact)
- sterile gloves and technique
- new bottle of local anesthetic
Needle size for low blocks? What about higher blocks and joint blocks?
Low: 25g
Higher & joint: 20 or 21
Diagnostic imaging-anatomical only
- Radiography
- CT
- MRI
- Standard US
Anatomical and functional diagnostic imaging
- Nuclear scintigraphy
- MRI
- Advanced US
- Thermography
If you have a suspect stress fracture but normal rads, how long should you wait before re-imaging?
7-10 days (latent period)
How does MRI produce an image?
exciting hydrogen nuclei at a specific resonance frequency within magnetic fields then detecting the energy released as the nuclei relax
What is the only good way to image soft tissue structures within the hoof capsule?
MRI
Preferred modality for soft tissue imaging after lameness is localized to a specific region
MRI
What functional information does MRI give you?
fluid signal within tissues indicates edema & inflammation
Primary imaging modality for soft tissue structures outside of the hoof
ultrasound
Functional assessments-ultrasound
- doppler-blood flow
- elastography-tissue strain for tendons and ligaments; helps determine how functionally tendons are healing
What imaging modality may be indicated when you can’t effectively diagnose lameness from a block?
nuclear scintigraphy
mechanism-nuclear scintigraphy
99mTc - diphosphonate thought to bind to exposed hydroxyapatite crystals in areas of bone remodeling or in soft tissues undergoing mineralization
Pool phase-nuclear scintigraphy
- less than 15 min
Thermography is touchy, but possible applications are:
detect inflammation or vascular damage in limbs
Origin of the majority of lameness in horses:
forelimb, within foot
Laminar corium
soft tissue attachment to the coffin bone
What structures are interdigitating in the hoof
epidermal lamina + laminar corium(dermal lamella)
abnormal foot angles predispose to:
- coffin joint OA
- navicular dz
With sheared heels, what side is generally longer?
medial longer than lateral
What abnormal hoof-pastern axis is most common?
broken back
angle of heels at least 5 degrees<toe>
</toe>
underrun heels
Breed disposition to underrun heels
TB
Consequences of underrun heels
- subsolar abscesses
- bruised heels
- increased strain on DDFT
Underrun heels-corrective shoeing
heel support (wedge)
Etiology of contracted feet
- secondary to lameness
- induced through shoeing (too small)
- hereditary
Tx for contracted foot
- fix primary problem
- keep barefoot
- exercise-concussive forces encourage foot to grow
Single most common cause for sudden onset of severe unilateral limb lameness
subsolar foot abscess
Etiologies of subsolar abscess
- sole trauma
- laminitis
most important aspect of tx for subsolar abscess
debride to provide drainage
Dx for subsolar abscess
very reactive to hoof testers at the abscess site
Organism causing thrush
Fusobacterium necrophorum
Breeds with higher incidence of navicular than others
QH, TB, WB
Clinical signs of navicular syndrome
- insidious onset
- commonly bilateral & worse on hard surfaces and when circled
- often short strided
- may stumble/shuffle-trying to land on toe
- often point the forelimb that is most painful
Predisposing factors-navicular syndrome
- excessive weight
- small or narrow feet (e.g. QH)
- broken back conformation
- medial-lateral hoof imbalances
- work on hard surfaces
Structures involved in navicular syndrome
- navicular bone
- flexor surface of navicular bone
- DIP (coffin) joint
- DDFT
- navicular suspensory ligaments
- impar ligament
What is the origin of pain with navicular syndrome?
- intraosseous pressure
- damaged supporting soft tissue structures
- inflammation of bursa & coffin joint
Navicular syndrome-dx
CS, response to blocks, rads
- PD - also blocks coffin joint and navicular bursa
- rads: increase in #, size, shape of synovial invaginations. changes in navicular bone shape. flexor cortex (where DDFT glides over back of navicular bone) erosions, roughening. loss of corticomedullary distinction. medullary sclerosis. enthesopathy at collateral lig.
MRI findings - navicular syndrome
- bone edema
- adhesions
- flexor cortex adhesions
can change prognosis, see things rads can miss
Corrective trimming/shoeing for navicular syndrome
- enhance breakover w/ rocker or square toe
- raise and support heel (2-3 degrees)
can vary with indiv. horses. have to see how they respond.
What does Tildren do?
inhibit bone resorption
Mainstay of surgical treatment of navicular syndrome
PD Neurectomy
Potential complications with PD neurectomy
- neuroma
- re-innervation
- DDFT rupture-poor prognosis, maybe life ending
Laminitis CS
- classic stance to take weight of front feet
- reluctance to move/walk
- increased recumbency
- increased digital pulses
- sinking at or separation of coronary band
Etiologies-laminits
- mechanical-d/t overload from opposite leg lameness
- endotoxemia-vascular microthrombosis
- grain overload
- metabolic derangements
- black walnut shavings
A _______ can be done to stop P3 rotation
DDF tenotomy
Prognosis for a toe/quarter crack that starts at the bottom
good
Prognosis for coronary cracks
poor
Tx for toe cracks
patch, hoof resection, shoeing
chronic, hypertrophic, moist pododermatitis of the epidermal tissues of the foot
canker
Causes of canker
- F. necrophorum
- Bacteroides spp.
Main difference in canker vs. thrush
horn hypertorpy
Canker is most common in ____breeds
draft
Topical abx that would be suitable for canker
oxytetracycline, metronidazole