MSK Flashcards
3 types of equine muscle disorders
primary - traumatic/metabolic/infectious - diffuse or focal pain
secondary - using muscles differently because of pain - localised, muscle enzymes often normal
neuromuscular - muscle atrophy - myogenic or neurogenic
muscle strain - equine
acute pain
localised pain and swelling
hard to isolate - large muscle mass
risk factors -
type of activity
surface terrain
poor warm up
mildly elevated muscle enzymes
Ultrasound - fluid accumulation and disrupted fibre pattern
treatment -
cold hosing/icing
NSAIDs
rest
gentle mobilisation and exercises
exertional myopathies - equine
very prevalent
signs -
poor exercise tolerance
muscle stiffness
shortened hind limb stride
reluctance to move
firm, painful, hindquarter muscles
anxiety
pain
sweating
increased resp rate
colic type signs - pawing, trying to lie down
myoglobinuria
elevated CK and AST
sporadic or recurrant
sporadic - one off extrinsic factors - overexercising, dietary imbalance, exhausted horse syndrome
recurrant - intrinsic factors - heritable factos, breed related, recurrent exertional rhabdomyolysis, polysaccharide storage myopathy
recurrent exertional rhabdomyolysis (RER) - equine
abnormal regulation of muscle contraction
issue in calcium kinetics
light or hot breeds - thoroughbreds
suggested heritability
more often in nervous females
risk factor - high grain diet
diagnosis -
signs and history
serum CK and AST increase
muscle histology - used to rule out concurrent conditions
polysaccharide storage myopathy (PSSM) - equine
accumulation of glycogen in muscle fibres
type 1 - mutation in glycogen synthesis gene
can test for mutation
type 2 - looks similar on biopsy but no gene identified
mutation most common in draft breeds, warmbloods, appaloosas, cobs, and ponies
diagnosis -
signs
muscle enzymes
muscle biopsies - only see changes over 2yo
genetic testing - on blood or hair roots
myofibrillar myopathy - equine
exercise intolerance
intermittent RER
warmbloods and arabs
warmbloods can have normal muscle enzymes - confirm on biopsy
arabs - high enzymes after exercise, myoglobinuria - tend to be less painful
exertional myopathies - treatment - equine
relieve pain
correct fluids
protect kidneys from effects of NSAIDs
stabling for acute stages then keep them working - days off can make it worse
diet -
low starch, high fat
adequate electrolytes
vitamin E supplementation
amino acid supplementation - less evidence
medications - dantrolene sodium (muscle relaxant)
clostridial myositis - equine
rare but nasty
usually iatrogenic - recent IM injection
necrotising infection of muscle
systemic illness - severe toxemia
swollen, painful muscle at injection site
subcutaneous emphysema
antimicrobials
multiple surgical debridements
delayed onset muscle soreness - equine
poor performance
diffuse pain
couple of days after unusual exercise
eccentric muscle contractions - contraction when muscle under tension
equine motor neurone disease
not common
generalised atrophy
oxidative damage to motor neurons
risk factors -
vitamin E/selenium deficiency
prolonged pasture access with high CHO diet
signs -
happy enough
normal appetitie
muscle weakness and atrophy
trembling
weight shifting on standing
walk better than they stand
low head carriage
exercise intolerance
“elephant on tub” stance
retinal changes - pigmentation at back of retina
diagnosis -
low vitamin E in plasma
elevated muscle enzymes
muscle biopsy of tailhead - definitive
usually need euthanising
vitamin E deficiency - equine
presents similar to motor neuron disease
responsive to treatment
immune mediated myositis - equine
rapid atrophy
moderate muscle enzymes elevation
usually quarter horses
MYH1 mutation - homozygous horses more affected
triggered by exposure to episode of strangles or other respiratory disease
diagnosis -
biopsy - epxial or gluteal muscles
genetic testing
treatment - steroids, antibiotics if concurrent infection
hip dysplasia - risk factors
weight
types of exercise
overexercising when young
breed - big dogs
ddx - hip dysplasia
arthritis
legg-calves perthes - avascular necrosis of femoral head
psoas injury
elbow dysplasia
cruiciate injury
luxated patella
nervous conditions - sciatic pathology
neoplasia - bone or joint
sepsis
hip dysplasia - pathophysiology
joint laxity –> femoral head subluxation
osteoarthritis changes - wear, cartilage thinning, fluid, osteophytes
most crucial time for hip development - before 8 weeks
hip scoring
each hip scored between 0-52 (overall out of 106)
lower score better
VD radiograph under GA
very straight
both limbs straight out and tied together
labelled
ID number and kennel club number
reviewed by 2 experts
patellar luxation - pathophysiology
bad conformation - muscle action pulls patellar ligament and displaces patella
not congenital - born normal, other abnormalities/deformities in limb causing them to turn inwards
grading 1-4
hip dysplasia - signs
difficulty rising
abnormal gait
bunny hopping
pelvic limb lameness
clicking of hips
assymetric muscle mass
sensitivity on hind quarters - esp on extension and abduction
reduced range of motion
crepitus
asymmetric pad wear
all non specific
hip dysplasia - testing
ortolani test
barden test
radiography - VD legs extended, VD frogleg, lateral (hip series) - measures of dorsal acetabular cover, norberg angle, distraction index
hip dysplasia - management
pain management
exercises - range of motion, muscle mass, strength
controlled activity level
weight management
nutraceuticals
physiotherapy
surgery - excision arthroplasty (joint fills with soft tissue to create false joint), total hip replacement, joint fusion (not hips but other joints)
cruciate injury - signs
frog sitting - external rotation of opposing stifle
sit test
loss of muscle mass
cranial draw
meniscal injury
seen secondary to cranial cruciate rupture (in most cases)
usually medial meniscus
heals poorly - usually needs taken out
if taken out - always end up with degenerative joint disease
cruciate injury - management
suture - loop round to create rotating force and hold in place
osteotomy - TPLO, TTA - good outcomes, expensive
cruciate injury
cruciate function - prevents cranial translation and internal rotation of tibia and prevents hyperextension of stifle
most common cause of hindlimb lameness
often eventually bilateral
changes can exist before ruptures
partial tears common
usually not a contact injury - different from in people
elbow dysplasia - pathopahysiology
osteochondrosis of humeral condyle - failure of endochondrial ossification
ununited anconeal process - failure of fusion of growth plate allows anconeal process to detach
fragmented coronoid process - medial coronoid fragments due to fissuring under the surface
radio-ulnar incongruity - step between radius and ulna instead of smooth gap
can have any of these concurrently - complicated joint
elbow dysplasia - signs
lameness
choppy forelimb gait
effusion
pain
crepitus
reduced range of motion
patellar luxation - surgery
wedge recession
block recession
abrasion
tibial tubercule transposition
distal femoral osteotomy - dramatic
angular limb deformity - equine
vargus - limb bending inwards
valgus - limb bending outwards
limbs turned in, knees out
happens as they grow
mild deformities - stall confinement
more dramatic - may need surgery - perioteal stripping or transphyseal bridging
corrective foot trimming
prognosis affected by - age at intervention, degree of deformity, joint affected and time that growth plate usually fuses, what the horse needs to eventually do
growth plate closure times - equine
P1 - long pstern - 2-3 months
MC3 - cannon bone - 6-9 months
distal radius - 9-12 months
osteochondrosis - equine
2 types -
osteochondrosis dessicans (OCD) - non loaded margin of high impact joints
sub chondral bone cysts (SBC) - high load margins, cysts develop within the joint
usually genetic with environmental factors
circulation not getting to cartilage as well as it should in rapidly growing young animals
cartilage doesn’t develop how it should
fracture classification
cause - intrinsic or extrinsic
open or closed - is skin breached
extent of damage
number of fractures
position
direction of fracture lines
location
forces acting on the fracture - affects stability after fixed
involvement of other tissues - trapped nerves, vessels, soft tissues, puncture of organs
age of fracture
fracture geometry
transverse - straight across
oblique - line of break offset from right angle
comminuted - multiple peices
segmental - large segment blown out
femoral fracture
most common small animal appendicular fracture
access for surgery lateral - less vessels
radius/ulna fracture
usually distal of mid diaphyseal
usually just repair radius
little dogs jumping off things
can sometimes just use external fixator if sides of fracture well opposed
tibial fracture
high velocity injury
access for surgery from medial side - tension side, skin tighter over bone, less muscles to go through
external fixator may work if comminuted and open
salter-harris fractures
physeal (growth plate) fractures
S - straight across
A - above (along plate then up)
L - lower (along plate then down)
T - through (cutting down through plate)
ER - erasure of plate (crush)
always damage to growth plate
avoid putting in devices that compress or restrict bone lengthening - smooth k wires preferred
femoral head fracture
usually young dogs (3-10 months) and cats
fracture across growth plate
operate early, delayed action worsens prognosis
proximal tibial fracture
main growth plate is a complression plate but also a tension plate at tibial tuberosity (attachment for patellar ligament)
need a tension wire so tibial tuberosity doesn’t just pull off
mandibular symphyseal separation
common in cats
wire it shut - occlude sides but don’t overtighten and crush tissues
take wire out after about 6 weeks
can use heavy gauge PDS instead of wire so will absorb
check no other jaw fractures before fixing
pelvic fractures
referral
needs a significant impact, not easy to break
multiple fractures
check spine, bladder, sciatic nerve
MSK cancer types
primary -
osteosarcoma - most common - make bone
myeloma, lymphoma, chrondrosarcoma - don’t make bone
secondary -
metastasis to bone - squamous cell cancinoma, lung-digit - more common than primary
osteosarcoma
agreesive
osteoblast tumour
large and giant breeds
more in male than female
middle aged to older
usually appendicular
poor prognosis
needs amputation and chemo - amputation alone not enough
90% have micro mets at time of diagnosis
