Equine Lameness Flashcards
Brad
What is Lameness?
Abnormal stance or gait caused by structural or functional abnormality of the locomotor system
Lameness is a manifestation of pain, mechanical dysfunction, or neuromuscular deficit causing alteration of gait
How to grade lameness?
Grading:
0: Not detectably lame 1: Inconsistently lame at trot on circle
2: Inconsistent on straight line but consistent in circle
3: Consistent on straight line trot
4: Lame at walk
5: Non-weight bearing
How to pin point the site of lameness?
Method of Examination: *HEEL PHFNDT
1. History, breed, age, use of horse
- Examine from distance
- Reluctant to Flex Carpi:
Shift weight w/ sharp turns, trip on step, takes 1-2 short strides out of stable
- Obvious Abnormalities:
Conformation, Angular limbs, contracted hoof, pelvic symmetry, swollen joint, splints, m. atrophy - Examine gait in hand/lunge
Method:
- Walk in hand:
Foot landing & arc of flight of limbs: May indicate heel pain (Toe > Heel) or conformational (Varus)
- Trot: In hand towards & way from you to indicate which leg is lame
- Other Gaits: Not used as it is difficult to determine at higher speeds
- Lunging:
Indication: If lameness is not readily apparent
Method: From left to right (Vice-versa) from large (20m) to smaller (10m – exacerbates lameness)
Identification:
a) Lame Leg: Lameness more apparent when the lame leg is on the inside UNLESS the site of pain is on the medial aspect of the leg, e.g., proximal suspensory, medial hoof
b) Hindlimb lameness: Shortened cranial phase stride and ‘toe stabbing’ action with affected leg on inside of circle
- Lame leg Identification
Front leg: Head goes up when lame leg lands – observed with horse trotting towards you
Back leg: Hip hike – point of hip moves up/down more when lame lands – observed trotting away - Palpation of joints, tendons & ligaments
Feeling for: Heat (Hoof wall), pain, swelling, digital pulse (NVB at palmar/plantar abaxial border of proximal sesamoids), joint/tendon sheath effusion
Method: Ground up - Hoof testers & percussion
Tester
Method: Heels, quarters, toe, frog, repeat on other side
Percussion
Method: Use hammer and percuss around solar surface of hoof/shoe and allow trotting off
Indication: Deep pain, e.g., Navicular dz, pedal osteitis
- Flexion Tests
- Nerve & Joint Blocks
- Diagnostic Imaging
Describe flexion tests for detecting lameness
Method: Apply flexion to joints for 60 seconds to increase the intra-articular & subchondral bone pressure → exacerbates clinical/subclinical lameness
Static Flexion: Is flexing without trotting off afterwards
–> Screening test and assess joint range of motion
Dynamic Flexion: Involves trotting off post-flexion
Order of Flexion Tests:
- Distal Limb Flexion: Coffin, Pastern, Fetlock (contributes most in +ve flexion of a non-lame)
Flexes: Prox. Interphalangeal joint, DIJ, Metacarpophalangeal Joint & navicular apparatus
Cannon bone MUST perpendicular to avoid flexing
- Carpal Flexion: Carpus
Positive: Via lameness originating from carpus, MC3 or distal radius
Grab pastern and pull until hoof is lateral of elbow – pull up pastern & push radius down - Prox. Forelimb: Elbow, shoulder
Positive: Hard to isolate due to lacertus fibrosis - Spavin (Hock): Hock, stifle, hip
Positive: May also flex fetlock
Grasp fetlock and lift leg until cannon is parallel to ground
Describe nerve blocks for detecting lameness
Nerve/perineural Block
Method: 1.5-3ml of prilocaine/mepivacaine – 25G x 5/8” needle – alcohol wipe or aseptic scrub if by synovium → wait 10-15min & prick injection site
Joint Block
Method: 5ml fetlock, 35ml stifle → no shaving, but do aseptic prep – 21/20G x 1.5” needle w/ new bottle – does not result in loss of skin sensation
Forelimb:
- Distal Limb:
a) Palmar Digital NB (PDNB)
Location: Neurovascular bundle (NVB) proximal to collateral cartilages
Blocks: Caudal 1/3rd of foot – Heels, Navicular pone, P3, Varied amount of sole, DIP Joint
b) Abaxial Sesamoid NN (ABSNB)
Location: NVB at base of proximal sesamoids bones
Blocks: Mid pastern and entire distal foot including skin sensation
c) IA Coffin/DIP JB
Location: Dorsal or lateral approach to minimise P3 extensor process damage Blocks: DIP, sole & NBo
d) Navicular Bursa JB
Needle: 18G 3.5”
Location: Btwn heel bulbs at coronet level ~1cm distal with limb raised in partial flexion
Directed midway along circumference of hoof
- Fetlock
a) Low 4 Point
Location: Distal metacarpus near buttons of splints and btwn DDFT & suspensory
Blocks: Fetlock, sesamoid, SL br (Suspensory ligament?) & below
b) IA Fetlock JB (Intra-articular fetlock joint block)
Location: Through collateral lig. of sesamoid btwn palmar MC3 & suspensory lig
- Metacarpus:
a) High 2 Point - Carpus: 3 Joints
a) IA Middle Carpal JB & Radiocarpal JB: Middle carpal & carpometacarpal have communication, radiocarpal stands alone.
Hindlimb:
- Distal Limb:
a) PBDN
b) IA Coffin JB
c) Navicular Bursa JB
d) ABSNB:
Location: Inject medial nerve from contralateral side of horse +- Combine dorsal metatarsal n. at pastern either side of extensor - Fetlock
a) Low 6 Point
Location: Same as 4-point but inset two more cranial to the 3MC bone
b) IA Fetlock JB
- Metatarsus:
a) Lateral Plantar NB
Location: Elevate limb & hock partially flexed to displace ADFT medially → inject axial to prox. MT4
- Tarsus
Tibiotarsal & Proximal intertarsal ALWAYS communicate
Distal & tarsa-metatarsal sometimes communicate
a) Tarsometatarsal
Location: Head of splint & T4 at palpable notch – aim opposite to from fetlock
b) Distal intertarsal
Location: Medial 6-8mm proximal to tarsometatarsal at the distal calcaneon tendon
c) Tibiotarsal:
Location:
Dorsal pouch - either side of saphenous v. ~3cm below medial malleolus
Plantar pouch – Between lateral malleolus & Calcaenous
Explain how diagnostic imaging can be used to detect lameness
Radiography
Issues: Portability (minimalistic), delayed exposure, requires oblique views, mixed practice multi-application, less than ideal environment
Radiation Safety: Limit exposure, increase distance, body protection, limit personnel, safety badge
Definitions: Radio-lucency (the degree of ‘blackness’), Radio-opacity (the degree of ‘whiteness’)
Interpreting Hoof Radiographs:
* Forelimb
– “Craniocaudal” – proximal
to the radiocarpal joint
– “Dorsopalmar” – distal to the radiocarpal joint
- Hindlimb
– “Craniocaudal” – proximal
to the tibiotarsal joint
– “Dorsoplantar” – distal to the tibiotarsal joint
Musculoskeletal US
MOA: Ultrasound waves emitted from piezo-electric crystal
Method: Sedate, clip palmar/plantar region, mark 5cm intervals, alcohol clean, contact gel
Definition:
- Power: No. of sound waves
- Gain: No. sound waves receive by probe
- Higher freq: Poorer penetration, better resolution
- Lower freq: Better penetration, poor resolution
- Isoechoic: Uniform
- Hypoechoic: Less echogenic (Black)
- Anechoic: Absence of fluid/blood
- Hyperechoic: Increased echo (White)
- Fascicle Alignment: Parallel linear echoes
Defining Lesions:
a) CSA (Cross-Sectional Area): Most sensitive indicator of damage
- SDFT - <120mm,
DDFT <1.5mm, SL - <1.5mm
b) Lesion Type/Severity:
0: Isoechoic – normal
1: Slightly hypoechoic
2: 50% anechoic, 50% echoic
3: Mostly anechoic
4: Completely anechoic (Core lesion)
Hyperechoic – Cr. tendonitis:
1 – brighter cf. isoechoic = dense scar,
2 – Mineralisation
c) Fibre Alignment
Good predictor of outcome
0: >75% parallel
1: 50-75% parallel
2: 25-50%
3: <25%
d) Echogenicity
e) Location/length
Others:
- Scintigraphy (Technetium 99): Soft tissue and bone – uptake is increased at bone modelling
- MRI: Good for soft tissue but limited to distal limb
- CT: Good for bone & soft tissue, for distal limb & head
- Thermography: Subjective
What are some soft tissue causes of Distal Limb Lameness?
- Subsolar Abscess
- Septic Pedal Osteitis
- Seedy Toe AKA White Line Disease
- Corns
- Poor Hoof Quality
- Vertical Hoof Wall Crack
- Thrush
- Canker
- Navicular Disease AKA Caudal/Palmar Heel Pain
- P3 Fracture
- Sole Punctures
- Others
What is Subsolar Abscess?
Cause: Recent rain softens sole → easy to penetrate, shod recently & nail close to whiteline, subclinical seedy toe
CS: 4-5/5 lame, bounding digital pulse, hot hoof wall/coronet, +ve hoof tester +- coronet eruption
Ddx: Fracture, cellulitis, penetrating injury, septic synovitis – All 4-5/5 lameness
Tx:
- ABSNB sedation
- Find black holes/tracts in white line→ loop knife
- Drain (14G) → small loop knife to drain pus between sensitive sole corium and non-sensitive/cornified sole
- Sugar-iodine hoof poultice 7-10d or until drainage stops
What is Septic Pedal Osteitis?
Cause: Secondary to penetrating wound or unresolved hoof abscess
CS: Persistent lameness & discharging tract, under-run sole, concurrent cellulitis & coronet swelling
Dx:
- Radiography
Views: LM, High coronary
Path: Osteolysis, demineralisation, irregular margin +- Osseous sequestrum & involucrum
Tx:
- General anaesthesia, torniquet & ABSNB
- Pack defect w/ saline gauze q2-3d
- Ab: Systemic, topical, local
- Hospital plate: Bar shoe & solar plate
- Rx curettage of GT
- 3m rehabilitation
What is Seedy Toe/White Line Disease?
Cause:
- Chronic subclinical laminitis
- Inadequate hoof care
- Wet environment
- Impaction of white line: Separation of wall and white line resulting in foreign material impaction.
CS: Severe cases may have distal displacement of P3 via dorsal wall detachment caused by laminitis
Dx: Radiograph - Radiolucent area in hoof wall that extends to ground surface
Tx:
- Resect disease wall/laminae
- Bandage/iodine if sensitive laminae
- Wall strip disease wall contacts coronet
- Rx radiograph/farrier assessment
- Heart bar/Straight bar shoe with wall clips to stabilise wall +- support sole
What is Corns?
Cause: Ill-fitting shoe or prolonged shoeing interval
Deep bruising of sole often adject to the bar/heel region
Tx: Resection of bruised thickened sole,
Apply Sugar-iodine poultice until sole is firm enough to apply wide webbed seating out shoe with no sole pressure
What causes poor hoof quality?
Cause: Wet season
CS: 3-4/5 lame, worse on hard ground
Tx: Wide webbed deep-seated aluminium shoe. No sole sole pressure from shoe
Aluminium shoe attenuates force better, lighter shoe
What is vertical hoof wall crack?
Cause:
- Poor hoof care/farriery
- Previous coronary trauma
- Laminar damage
- Untreated hoof abscess
- Foreign body
- Seedy toe
- Laminitis
Type 1
NOT involving coronet Cause: Seeding toe, long toes, dermal lamellar cracks/bruises
Tx: Resection to normal, shoe w/ side clips (+-bar shoe), equilox patch/wall plates as temporary solution
Type 2
Involves coronet
Cause: Coronet trauma, progress from Type 1 crack
Tx: Same as above but may require complete hoof wall strip & bar shoe w/clips OR hoof cast
→ 9-12m to grow down
What is Thrush?
Thick black putrid discharge usually in frog sulci and heel bulbs
Cause: Poor hoof care, moisture
Treatment: Debridement, topical alcohol/iodine, dry environment, regular hoof care, open up sulci angles
What is Canker?
Cause: Environmental, Bacterial (Fusobacterium), ? Immune mediated, BPV
CS: Proliferative degeneration of frog, solar corium, digital cushion +- concurrent coronary dystrophy
Tx: Debridement under GA), pack w/ metronidazole paste, change enviro, improve hoof care
Px: HIGH recurrence rate
