EQUINE LIMBS Flashcards
Why might we want to take radiographs of the musculoskeletal system
-Answer the clinical questions/ confirm clinical suspision
-Document the extent of the disease +/- progression
-Provide images to direct treatment
Where do equine limb radiographs fit into our workup?
-History
-Physical exam
-Lameness exam
-Nerve blocks
-Narrowed differential list
-Use radiographs to rule out clinical suspicion
Why might we take radiographs of horses
To look for change associated with
-Osteoarthritis
-Osteochondrosis
-Trauma/fractures
-Infection
-Neoplasia
T/F: osseous neoplasia is common in horses so radiographs are a valuable diagnostic tool in diagnosing this
False- although they are valuable
osseous neoplasia is uncommon in horses
What can you see on radiographs
1) Bones
2) Soft tissue and fat
3) The space where cartilage lives
What are the 5 opacities
1) Gas/Air
2) Fat
3) Soft tissue
4) Mineral
5) Metal
What also affects the opacity we see on radiograph
the thickness/volume of the tissue
Radiographs are _____ for bone but ______ for soft tissues
good for bone- highest spatial resolution for all modalities (but can only get 2D)
Poor for soft tissues but can give you clues about possible soft tissue injury / involvement
Radiographs are poor for soft tissue but can
but can give you clues about possible soft tissue injury/ involvement
How is cross-sectional imaging like CT for the equine musculoskeletal imaging
good for bone (less spatial resolution than radiographs)
ok for soft tissues
How is cross-sectional imaging like MRI for equine musculoskeletal imaging
ok for bones (Less spacial resolution than radiographs and CT (ie less detail)
great for soft tissues
Are radiographs, CT, or MRI best at soft tissues
MRI
Rank the following modalities in spatial resolution on bone
Radiographs >CT> MRI
Proximal to the radiocarpal and tarsocrural joint we use what directional terms
Cranial/Caudal
Distal to the radiocarpal and tarsocrural joint we use what directional term?
Dorsal and palmar/plantar
At what joint in the front limb do we distinguish cranial/caudal vs dorsal/palmar
radiocarpal
At what joint in the hind limb do we distinguish cranial/caudal vs dorsal/plantar
tarsocrural
Why is more than one projection important
to see the different views and know where things are
How many views/projections do we take?
Depends on the joint/region
From the carpus/tarsus to the pastern region generally a minimum of four projections for each region
-often more projections for the foot
-fewer for the upper limb as we are restricted by anatomy that gets in the way
Why do we take fewer views/ projections of the upper limb
because we are restricted as anatomy gets in the way
For carpus/tarsus to the pastern region we generally take _________
generally a minimum of four projections for each region
1) Lateromedial
2) Dorsopalmar
3) DLPMO
4) DMPLO
radiographic projections are named after
the path of the xray beam from the generator to the plate
the path of the xray beam from the generator to the plate
how radiographic projections are named
Where does the beam enter vs exit in a latero-medial projection
Lateral side- where the beam enters
Medial side- where the beam exits (plate side)
Where does the beam enter vs exit in a dorsopalmar projection
Dorsal- where the beam enters
Palmar- where the beam exits (plate side)
What is a DLPMO?
A dorsolateral to palmaromedial oblique projection
The beam enters the dorsolateral aspect, exits the palmaromedial aspect
The beam enters the dorsolateral aspect, exits the palmaromedial aspect
Dorsolateral to Palmaromedial oblique (DLPMO)
In a DLPMO view- where does the beam enter/exit
The beam enters the dorsolateral aspect, exits the palmaromedial aspect
created when you move 45 degrees towards the lateral frin the dorsal plane to create an oblique image on the front limb
D45LPMO- dorsal 45 degree lateral - palmaromedial oblique
how are images named when they are taken from the palmar/plantar aspect
they are still named after the direction of the beam
ex: Palmaromedial to dorsolateral oblique (PMDLO) will create the same image as the DLPMO
T/F: Palmaromedial to dorsolateral oblique (PMDLO) will create the same image as the DLPMO
True- they are same image but still named after the direction of the beam
What are hanging protocols
set of rules that govern how images are displayed for review.
They automate several aspects of image interpretation, making it more efficient and consistent
1) Head to the left
2) medial to the left
3) Right side on the left
What are the three rules of hanging protocol, used for efficient and consistent interpretation
1) Head to the left
2) medial to the left
3) Right side on the lef
According to hanging protocols, the head should be orientated towards the
Left
According to hanging protocols, the medial side should be
to the left or the right side of left
what is highlighting
the margin/edge of the bone that we are seeing well
In a latero-medial image what is being highlighted
Dorsal margin
Palmar margin
In a dorso-palmar image what is being highlighted
Medial margin
Lateral margin
In a DLPMO image, what is being highlighted?
Dorsomedial margin
Palmarolateral margin
Why are markers important
1) is it right or left
2) What is medial and what is lateral
-sometimes asymmetric anatomy can help you (e.g carpus)
How do you determine where the markers go
the marker goes dorsal or lateral
The marker goes ______ or _____
Dorsal or lateral
on an oblique projection, how do you decide where the marker goes
It will go lateral (lateral wins over dorsal)
the marker goes along with whichever highlighted margin has lateral in its name
If you have a DMPLO projection of the left front fetlock, how will you determine where the marker is?
the dorsal aspect
IF you have a DLPMO projection of the left front fetlock, how will you determine where the marker goes
on the plantar side
you have a radiograph of an oblique view and the marker is on the palmar side. What view is this in?
DLPMO
T/F: centering on the area of interest is important
True
ex: you cant evaluate stifles if they are in the corner of an abdominal radiograph
What is the checklist of 5 things MSK radiographs in horses
1) Articular surfaces of the joint - joint space, subchondral bone, adjacent trabecular bone
2) Periarticular region- for osteophytes
3) Areas of soft tissue attachment- enthesophytes (or lysis)
4) Other soft tissue structures- synovial structures (joint pouches/recesses, tendon sheaths, bursae), plane/location of tendons and ligaments, cutaneous margins/soft tissue swelling (intracapsular or extracapsular)
5) Periosteum/ endosteum: irregular/active vs smooth/inactive ; aggressive vs nonaggressive
Why do you examine the peri-articular region
For osteophytes
What are you looking for in the articular surfaces of the joint on radiographs
1) Joint space
2) Subchondral bone
3) Adjacent trabecular bone
What are you looking for in the areas of soft tissue attachment on radiographs
Enthesophytes (or lysis)
osseous proliferation at the articular margin (at the junction of the articular cartilage and the periosteum)
indicator of joint disease
Osteophytes
Where are osteophytes
at the articular margin (at the junction of the articular cartilage and the periosteum)
Where are enthesophytes located
osseous proliferation at the insertion of ligaments/tendons/ joint capsule on the bone
osseous proliferation at the insertion of ligaments/tendons/ joint capsule on the bone
usually grows in the direction of the pull of soft tissue structure
Enthesophyte
Enthesophytes usually grow in the direction of
usually grows in the direction of the pull of soft tissue structure
What soft tissue structures should you examine on MSK radiographs
1) Synovial structures0 joint pouches/recesses, tendon sheaths, bursae
2) Plane/location of tendons and ligaments
3) Cutaneous margins/soft tissue swelling
Intracapsular soft tissue swelling
soft tissue swelling on radiograph that is associated with the joint
-effusion, synovitis, synovial hypertrophy
Extracapsular soft tissue swelling
soft tissue swelling on radiograph that is associated outside the joint
-cellulitis
-edema
-hemorrhage
-abscess
What are the three signs youll see in aggressive bone lesions
1) Cortical destruction
2) Active periosteal rxn
3) Indistinct transition zone
*Only need one of these features to be classified as aggressive
What is an example of a non-aggressive bone lesion
normal fracture callus
How do you classify periosteum/endosteum
-Irregular/active vs smooth/inactive
-Aggressive vs non-aggressive
-
How do you descrube radiographic changes
1) Opacity category (Air, fat, soft tissue/fluid, Mineral, metal)
2) Roentgen signs: Size, shape, margination, opacity, location, number
3) Relative opacity change: ex- increased opacity of the third carpal bone (sclerosis) or ex- bone becomes darker but not so dark it looks like soft tissue- decreased opacity of the patella and medial femoral condyle -> lysis associated with joint sepsis and secodnary osteomyelitis
How do you use Roentgen signs to describe a lesion
1) Size
2) Shape
3) Margination
4) Opacity
5) Location
6) Number
example: single, moderate sized, ovoid, well-defined, radiolucent region of proximal radius for an osseous cyst-like lesion of the proximal radius
What are the 6 roentgen signs to describe radiographic changes
1) Size
2) Shape
3) Margination
4) Opacity
5) Location
6) Number
different types of complete fractures
1) Transverse
2) oblique
3) Spiral
4) Comminuted
the whole bone cortex is not broken
incomplete fractures
fractures that involve the growth plate
Salter-Harris
How do you describe fractures
1) Type
a) Complete: transverse, oblique, spiral, comminuted
b) Incomplete
c) Salter-harris: fractures that involve the growth plate
2) Open vs Closed
3) Location: diaphysis, metaphysis, epiphysis
4) Fx displacement- the distal component displacement in relation to the proximal component
5) Other- joint involvement, underlying bone lesion- if pathological fracture
What is a Salter-harris fracture
a fracture that invovles the growth plates
How do you describe fracture displacement
the distal component in relation to the proximal component
Fracture displacement is descrubes as
the distal component in relation to the proximal component
What can mimic fracture lines
Mach lines : an optical phenomenon from edge enhancement
an inbuilt enhancement mechanism of the retina
the edges of darker objects next to lighter objects will appear darker
What are the two parts of a radiographic report
1) Radiographic findings: a description of the radiographic abnormalities
ex: a well defined ovoid radiolucent area within the medial femoral condyle with a radiopaque rim that extends to articular surface
2) Radiographic diagnosis/conclusion
ex: osseous-cyst like lesion of the medial femoral condyle with associated sclerosis and articular communication
What are the 7 radiographs routinely taken of the equine foot
Full series
1) Lateromedial
2) Dorsopalmar
3) DP-60
4) DP- 65
5) Proximopalmar to distopalmar “navicular skyline”
6) Obliques of P3- D65Pr-45M/LPaO
What areas of soft tissue attachment do you need to look at in the equine foot
1) Collateral ligaments
2) Collateral sesamoidean ligament
3) Impar ligament
4) DDFT
5) Joint capsule
What synovial structures do you need to evaluate in the equine foot
1) Digital flexor tendon sheath
2) DIP and PIP joints
3) Navicular bursa
What radiograph view is important to see the navicular skyline
Proximopalmar to distopalmar
How do you prepare the foot before taking radiographs
1) Pick out feet well and brush any dirt from hoofwall
2) Ideally remove shoes
3) Pack sulci with playdoh
4) Sedation and stading square on elevated blocks
What is another name for the DP60 view
Solar margin view
a radiograph where the horse is standing on a plate
generator is placed dorsally and moved 60 degree proximally to be centered on the coronary band
DP 60 - Dorso60 proximal-palmarodistal
“Solar margin view”
In a DP60 radigraph, the generator is centered on the
coronary band
What is the name of a radiograph that has the horse standing on plate
generator is dorsal and moved 65 degrees proximally
collimated down to the navicular bone
DP 65- Dorso65Proximal- Palmarodistal
“Navicular DP”
What is another name for the DP65
Navicular DP
What is the point of a DP65 radiograph
it is good for looking at the margins of the navicular bone and the palmar processes of P3
What does the D60Pr45L/MPaO highlight?
the medial and lateral margins of P3 and palmar processes
a view where the horse is standing on a plate and the limb is positioned caudally
generator is positioned palmaroproximal and x ray beams and ejected palmarodistally
Palmaroproximal to Palmarodistal (PaPr-Pa-Di)
What is another name for the Palmaroproximal to Palmarodistal (PaPr-Pa-Di)
Navicular Skyline
How should the horse be standing for a Palmaroproximal to Palmarodistal (PaPr-Pa-Di)
standing on the plate
want the limb positioned caudally
highlights the flexor surface of the navicular bone and allows for evaluation of distinction between cortex and medullary bone
Palmaroproximal to Palmarodistal (PaPr-Pa-Di)
“Navicular Skyline”
What are the three types of synovial structures
1) JOints
2) Tendon sheaths
3) Bursae
What views are useful to assess overall foot shape/conformation and part of preventative hoof management
1) Dorso-palmar (DP)
2) Lateromedial
The phrase for overall shape of the bones and foot
hoof balance
hoof imbalance can cause pain
What is normal dorsopalmar balance
A positive palmar angle
solar margin angle is between 3 and 8 degrees
The solar margin angle should be about
Between 3 and 8 degrees
Positive palmar angle
*on lateral radiograph
What is medial-lateral balance
a sign of good foot conformation where
1) same sole depth medial and lateral
2) Joints are parallel to the ground
Medial-lateral imbalance
where on DP radiograph you see different sole depths and joints that are compressed on one side and not parallel to the ground
what is negative palmar angle
a sign of poor foot conformation where on Lateromedial radiographs you see a solar margin angle of less than 0 degrees
Puts strain on the deep digital flexor tendon and navicular bone
What is the consequence of having a negative palmar angle
if the angle is less than 0 degrees this puts stain on the deep digital flexor tendon and navicular bone
“Dorsopalmar imbalance”
Upon lateromedial radiograph of an foot you see a solar margin on 0 degrees. Is this good
No this is poor conformation
needs to be between 3 to 8 degrees
work with a ferrier to get more of a heal
What should you always ensure when evaluating foot conformation
make sure there is a straight projection
if you take the images not face on then there is artifactual imbalance
straight positioning corrects the false impression of imbalance
What corrects the false impression of foot imbalance
straight positioning
What are common disease processes of the phalanges and navicular bone
-Osteoarthritis
-Fractures
-Laminitis
-Navicular degeneration
-Misc: foot abscess, pedal osteitis, keratoma, collateral cartilage ossification, penetrating foregin bodies
What causes osteoarthritis of the phalanges in horses
Primary: normal wear and tear with age
SecondaryL trauma, soft tissue injury and instability, prior infection
What are radiographic signs of early/mild osteoarthritis in horse phalanges
1) Joint effusion. synovitis- intracapsular soft tissue swelling (convexity of soft tissue margin at this level)
2) Periarticular osteophytes
3) Enthesophyte production at joint capsule insertion
What should you consider about the extensor process when interpreting radiographs
it can have multiple different variations (double point, blunt single point, single point, or rounded)
so be careful diagnosing osteoarthritis solely on the extensor process of P1
bone fusion across a joint space
can be seen with late/severe osteoarthritis
ankylosis
What radiographic evidence do you see with osteoarthritis in the equine phalanges
Early/Mild:
1) Joint effusion. synovitis- intracapsular soft tissue swelling (convexity of soft tissue margin at this level)
2) Periarticular osteophytes
3) Enthesophyte production at joint capsule insertion
Late/Severe:
1) Loss of cartilage resulting in narrowing of joint space
2) Subchondral bone sclerosis and/or lucent regions due to demineralization and/or degenerative cystic changes
3) Ankylosis
What changes do you see with late/severe osteoarthritis
1) Loss of cartilage resulting in narrowing of joint space
2) Subchondral bone sclerosis and/or lucent regions due to demineralization and/or degenerative cystic changes
3) Ankylosis
How can you tell if there is narrowing of joint space of equine foot
Best evaluated on DP projection
DIP is widest and PIP is about 50% the width
Fetlock is 40% the width of DIP
1) Compare to contralateral limb
2) Age/breed comparison
3) Compare to normal in textbook
artifactual if they are not standing square- might show the DIP is smaller
Does the Fetlock, PIP, or DIP have the largest joint space
DIP > PIP> Fetlock
PIP is 50% width of DIP
Fetlock is 40% width of DIP
P1 and P2 fractures usually occur by _____ while P3 fractures typically occur when _______
P1+P2: during athletic activity
P3: when the horse kicks a stationary object
What are the clinical signs of phalanges fracture in horses
lameness +/- joint effusion
positive hoof tester reaction (for P3 fractures)
What might be a clinical sign of P3 fractures
positive hoof tester reaction
lameness +/- joint effision
T/F: acute phalanges fractures can be hard to see so you may need to repeat radiographs in several days or weeks where some resoprition of the fracture margins can make them easier to be seen
True
P3 fractures can heal with
fibrous union -> so may still be evident radiographically even when healed and sound
Why might you see a P3 fracture even though the horse is not lame
p3 fractures heal by fibrous union and may still be evident even when healed and sound
What is the main thing to determine with P3 fractures
Are they articular or non-articular
Most common P3 fracture
Non-articular or articular (Type I and II) palmar/plantar process fracture
Non-articular palmar/plantar process fracture
most common P3 fracture
forelimb: impact trauma or repetitive stress (often seen with ossified collateral ligaments)
Hindlimb: usually trauma kicks
Always need oblique views to determine if they are articular
favorable prognosis with rest as non-articular
How do you determine if a P3 fracture is articular
you need oblique views to determine this
What else might affect the prognosis/recovery time with P3 fractures
if there involvement of the collateral ligament fossa? If so then yes
normally Type 1 P3 fractures are quick recovery
P3 is most commonly fractured at the
Palmar/Plantar process
due to impact trauma/ repetive stress (forelimb) or trauma kick (hindlimb)
can be articular or nonarticular
Does Type I or Type II P3 fracture have a better prognosis
Type 1 because both of these involve fractures of the palmar/plantar process but type I is non-articular
Type 3 P3 fracture is a _______ fracture of P3
Sagittal articular fracture
Type 4 P3 fracture is a ________ fracture of P3
Extensor process fracture
-may be incidental or cause of lameness
Acute: sharp margins
Chronic: rounded
Solar margins of P3 occur
along the rim of P3
seen with laminitis or previous inflammation (pedal osteitis)
Type VII P3 fractures are only seen in
Foals
Palmar process fracture
Palmar process fractures in foals
most likely represent acute traumatic fractures or separate center of ossification or developmental orthopedic disease
hard footing and overtrimming are thought to be predisposing factors
thorough bred foals seem to be overrepresented
P2 fractures are commonly found in horses that
perform sliding and turning activitying on hindquarters
P2 fractures are typically (simple or comminuted)
comminuted and involve articular surfaces of the PIP and DIP
*CT is valuable for these
Why is CT valuable for P2 fractures
they are commonly comminuted and involve articular surfaces of the PIP and DIP
What are the 2 forms of P1 fractures
Incomplete: Begin at proximal articular surface in the sagittal groove, and extend a variable distance into P1, periosteal rxn can occur
Complete: incomplete can become complete, prognosis for athletic function is significantly affected by articular involvement, can fix with screws
inflammation of the laminae of the foot
very complex condition of blood dlow disruption to snesitive and insensitive lamina of the foot
eventually can lead to separation of P3 from hoof wall
laminitis
Laminitis can eventually lead to
separation of P3 from the hoof wall
What do you see clinically with laminitis
lame horse
pain localized to foot
increased digital pulse and heat in hoof
Laminitis is common in ______ feet but can occur in all 4
front
What radiographic views are you going to use for evaluation of laminitis
Lateromedial
DP
How do you radiographically evaluate laminitis in a horse
1) Lateral and DP projections
2) Normal: dorsal P3 and hoofwall are parallel
*Look for dorsal surface of hoof wall, Dorsal P3, and cornary bands
+/- metallic markers- typically not needed
do serial radiographs for progress
How might you rule out laminitis
Do lateral projection and check
dorsal P3 and hoofwall are parallel
HOWEVER: CLINICAL SIGNS OFTEN PRECEDE RADIOGRAPHIC CHANGES - need to do radiographs to monitor
How to you assess normal dorsal hoof wall thickness
MEASURE
Proximally: 2mm distal to junction of extensor process and the dorsal cortex of P3
Distally: measure 6mm proximal to the tip of P3
*2 measurements are the same
about 18mm in thoroughbreds but greater in draft and warmblood horses
What are the two main types of laminitis
1) Rotational
2) Sinking
*Can be combination of both
loss of strength of the lamina between the hooft wall and P3 with inflamamtion
Pull on DDFT on P3 causes palmar rotation of P3
May see radiolucent line in dorsal hoof wall = gas between sensitive and insensitive lamina
Rotational Laminitis
What do you see with rotational laminitis
Palmar rotation of P3 (caused by pull of DDFˇ on P3)
loss of strength of the lamina between the hoofwall and P3 with inflamamtion and the entire P3 sinks distally within the hoof capsule
Sinking laminitis
What kind of laminitis would result in a horse’s P3 penetrating through the sole
Sinking laminitis
What is vital in monitoring laminitis
Monitor changes with serial radiographs
radiographic changes can lag behind clinical signs
laminitis becomes chronic after
3-4 weeks
What is seen with chronic laminitis
after 3-4 weeks,
1) rotation of P3 generally persists
2) irregularity of dorsal margin of P3 persist; remodeling into ski tip of P3
3) With severe can see resoprtion of P3 and misshapen hoof capsule
How do you determine if P3 fractures are articular
you need to take an oblique view
What affects the prognosis of a P3 fractue
1) If articular involvement
2) If involvement of collateral ligament fossa
What might cause a type VII (palmar process fracture of P3) in foals
1) acute traumatic
2) separate center of ossification
3) developmental orthopedic disease
4) hard footing and overtrimming are predispositions factors
5) thoroughbred foals seem to be overrepresented
Why are CTs important in evaluating P2 fractures?
because radiographs tend to underestimate the number of fragments in these often times communited fractures involving the PIP and DIP joints
What causes rotational laminitis
pull of the DDFT on P3 causing palmar rotation of P3
What three radiographic findings you see in a horse with rotational laminitis
1) Increased Parietal Surface angle (the angle between the dorsal hoof wall and the dorsal P3)
2) Increased solar margin angle (Solar surface of P4 and the ground)
3) Distance in hoof wall thickness between the proximal and distal hoof wall
What 3 radiographic findings might you see in a horse with sinking laminitis
1) Increased coronary to extensor process distance >15mm
2) Decreased sole depth <11mm
3) Sinker line (visible depression in the coronary band)
What can severe chronic laminitis lead to
resorption of P3 and a severely misshapen hoof capsule
T/F: changes to the navicular bone can be seen without the horse being lame
true but lame horses might not have any radiographic changes
What are the clinical signs of navicular bone degeneration
1) Unilateral/bilateral forelimb lameness/ shortened stride
2) Sensitivity to hoof testers applied to the heel or frog
3) Lameness improves with palmar digital nerve block
What block would improve the lameness of a horse with navicular bone degeneration
palmar digital nerve block
What 5 radiographic changes can be seen in a horse with navicular bone degeneration
1) Synovial invagination (Enlargement and rounder shape and increased number)
2) Medullary bone sclerosis
3) Thickening of flexor cortex
4) Irregularity of the flexor cortex
5) Osseous proliferation associated with the attachment of ligaments
What might flexor cortex erosions of the navicular bone indicate
soft tissue injury
the DDFT and navicular bursa run palmar/plantar to the navicular bone
What ligament attaches to the distal aspect of the navicular bone
Impar ligament
What ligament attaches to the proximal aspect of the navicular bone
Collateral sesamoidean ligament
What ligamentous changes might help you determine navicular degeneration?
At proximal margin, you will see enthesophytes (collateral seasamoidean ligament)
Distal margin (small avulsion fragments) from the Impar ligament
foot abscesses in horses can only be seen on radiograph if
they are associated with a pocket of gas
infection within the subsolar region of the horse’s foot
usually 4/5 lameness and + to hoof test
Foot abscess
What can cause pedal osteitis in horses
foot abscesses
bruising
overtaining
foot deformities
Why do you see little periosteal reaction in P3 after injury
because it responds differently to inflammation
will see osteolysis generally 10-14 days after the injury
What are the radiographic findings in pedal osteitis
1) Resorption of solar margin
2) Irregular solar margin
3) Wide vascular channels
Is pedal osteitis a descriptive term or diagnosis
descriptive term
Septic pedal osteitis occurs
secondary to a puncture or foot abscess
could also contain a sequestrum
results in focal pedal osteitis
benign tumor of keratin of the hoof wall
causes smoothly margined conical bone resorption of P3
can cause deformation of hoof wall
Keratoma
What causes ungual cartilage mineralization
secondary to trauma, poor farriery, ligamentous injury, hereditary
radiolucnet line between ossidied cartilage and the rest of P3 is an area of non-ossified cartilage
Why might ungual cartilage mineralization become an issue
because if extensive it may lead to a fracture at the base
more common in draft and warmblood horses
What 5 views are taken of the fetlock
1) DP
2) Lateral
3) Flexed lateral
4+5) Dorsomedial and dorsolateral obliques
+/- special oblique views to highlight the proximal sesamoids
What does a flexed lateral of the fetlock expose
the dorsal surface of the sagittal ridge of MC3
When taking a dorso-palmar view of the fetlock, why do you want to angle downwards 20 degrees
because it will high light the proximal sesamoid bones
if taken at true horizontal, then the sesamoid bones are superimposed over the fetlock joint and the proximal phalanx
When taking a DLPMO or DMPLO of the fetlock, why do you want to angle down 20 degrees
it elevaates the sesamoid bones away from the proximal phalanx
The ___ and ____ are known as splint bones in the horse
MC 2 and MC4
Can you tell the difference between DLPMO and DMPLOs of the fetlock without markers?
No- these are almost identical.
radiographic marker placement is crucial to decipher which is which
The flexor tendons run _____ the sesamoid bones of the pastern
between
What are the three types of synovial structures
1) Joints
2) Tendon sheaths
3) Bursae
What 4 radiograph views are typically taken of the equine metacaprus/metatarsus
1) LM
2) DP
3) DMPLO
4) DLPMO
What are the differences between primary and secondary osteoarthritis in horses
Primary: result of normal wear and tear
Secondary: secondary to trauma, soft tissue injury and instability, prior infection
What are the common sites of fetlock osteophytes
1) dorsomedial and dorsolateral aspects of P1
2) Proximal and distal aspects of sesamoid bones
3) Palmar processes of P1
What will you see with late/severe osteoarthritis in the fetlock joint
loss of cartilage resulting in narrowing of the joint space
sunchondral bone sclerossi and/or lucent regions due to demineralization and/or degenerative cystic changes
ankylosis= bone fusion across a joint space (hard to see in the fetlock because there is a lot of motion there)
What might the fetlock skyline projection be useful for
seeing subchondral bone changes associated with osteoarthritis
flattening of the distal palmar articular margin of MC3 with associated sclerosis
palmar osteochondral disease
palmar osteochondral disease is typically seen in
race + sport horses
pseudo-flattening of the condyles
where there is flattening of the distal palmar articular margin of MC3 but since the condyles are not superimposed, it is not Palmar osteochondral diseases just mal-alignment
the proximal sesamoids in the horse is best evaluated in the ______ view
oblique progressions
What do normal sesamoids of the equine fetlock look like?
1) Smooth outer margin of the sesamoid bones
2) Parallel margins of the vascular channels <2mm width
What happens with equine fetlcok sesamoiditis?
rougher edges of the sesamoid bone margins
vascular channels >2mm width that are funnel shaped instead of parallel
With axial sesamoiditis, there are resorptive changes associated with the
intersesamoidean ligament enthesopathy
irregular lysis on the acial aspect of the sesamoid bones
associated with interseasmoidean ligament enthesopathy
can be non-septic or septic process
Axial sesamoiditis
If you see axial sesamoiditis, what should you start taking into account
is there a septic process going on?
This is unlike normal sesamoiditis
proximal sesamoid fractures are commonly seen in horses that are
athletic, commonly in racehorses
What is commonly referred to as chip fractures in horses
Dorsal proximal P1 fractures
What kind of fracture results in overextension of the fetlock
Dorsal proximal P1 fracture
Dorsal proximal P1 fracture
Chip factures
result in overextension of the fetlock
can also be osteochondrosis lesions (typically seen in warmbloods) -developmental
hard to differentiate in chronic stage
How do you differentiate acute fractures from chronic ones
Acute: sharp margins
Chronic: rounded margins
MC3/MT3 condylar fractures are most common in
racehorses
are MC3 or MT3 fractures more common in thoroughbred horses?
MC3 >MT3
Are MC3 or MT3 fractures more common in standardbred horses?
MC3 = MT3
What is the best view to see MC3/MT3 condylar fractures?
Flexed DP or 125DP
hard to see in standard projections esp if not propagated
“Bucked shins”
periostitis of dorsal MC3 diaphysis
-nonadapative remodeling, can lead to stress fractures (saucer fractures)
most common in racehorses
generally occur in forelimbs
microfractures and subperiosteal hemorrheage occuring leading to subperiosteal callus formation
What is another name for periostitis of dorsal MC3 diaphysis
Bucked shins
What are the second and fourth metacarpals/metatarsals called
Splint bones
acute manifestation of chronic periostitis
stress fractures
what might you have to do to visualize stress fractures
may have to take multiple oblique projections at slightly different angles to visualize the fracture
periostitis
non-adaptive remodeling that can lead to stress fractures
generally occur in forelimbs
microfractures and subperiosteal hemorrhage occur leading to subperiosteal callus formation
Splint bone fractures that are in the proximal half are likely to be caused by _______ while the distal half are likely related to ______
Proximal: secondary to trauma (comminuted)
Distal: Suspensory injury
What is “Splints”
Reactive Periositis
-secondary to trauma (hitting MC2 with the contralateral foot) or secondary strain on the interosseous ligament leading to remodeling of bone
-Can look similar to callus formation from a healing/healed prior fracture
more common medial than lateral
more common in forelimbs
can be active or inactive
What might cause reactive periositis “Splints”
1) secondary to trauma (hitting MC2 with the contralateral foot) 2) Secondary strain on the interosseous ligament leading to remodeling of bone
Are splints more likely to be medial or lateral
medial
are splints more common in forelimb or hindlimb
forelimb
With joint sepsis, bone changes on radiographs can lag by
10-14 days
a sclerotic piece of bone
sequestrum
a radiolucent region of bone
involcrum
Why are MC3/MT3 susceptible to sequestrum formation?
because there is a lack of soft tissue there, making the susceptible to rauma
when there is an injury to the outer surface of the bone from a wound or blunt trauma it may cause loss of periosteal blood supply resulting in death to the outer 1/3 cortex leading to sequestrum formation
Where is a typical place to see OC/OCD in the fetlock joint?
1) sagittal ridge of MC3
2) Palmar/Plantar P1 region
What is the best view to see OC/OCD of the sagittal ridge of MC3
LM or flexed LM
when might you see an attached fragment or a fragment that is free in the joint space
osteochondritis dissecans (OCD)
T/F: you may see incidental findings associated with OC/OCD of the fetlock
true- there may be mild flattening or defects without sclerosis or fragments
are palmar/plantar P1 osteochondral fragments more common in the forelimbs or hindlimbs?
hindlimbs
What is the best view to see palmar/plantar osteochondral P1 fragments?
obliques- moves the sesamoids up
harder to see on lateral projections
palmar/plantar osteochondral P1 fragments are likely caused by
either
1) OCD
2) avulsions fragments associated with ligaments that insert in that area
what should be aware of that looks like a bone fragment
the ergot
chronic condition where there is inflammation in the fetlock with proliferation of the synovial tissues
chronic proliferative synovitis
What do you see with chronic proliferative synovitis?
smooth bone resorption along the dorsal and palmar aspects of the condyle
osseous changes
1) sclerosis
2) resorption
3) avulsion fragments
What radiographic changes are seen with suspensory ligament enthesopathy
1) Sclerosis: enlarged suspensory ligament w irregular bone proliferation (increased uptake)
2) Bone resorption
3) Avulsion fragments
Injury to the suspensory ligament can affect
1) SL only
2) SL and bone
3) Bone only
What is suspensory ligament enthesopathy
injury to the suspensory ligament. can affect SL only, SL and bone, or bone only
leads to osseous changes
1) Sclerosis: enlarged suspensory ligament w irregular bone proliferation (increased uptake)
2) Bone resorption
3) Avulsion fragments
What are the standard images taken of the equine carpus
1) lateromedial
2) flexed lateromedial
3) DP
4) DLPMO
5) DMPLO
When taking a flexed lateromedial view of the equine carpal, what 2 bones go higher than the others
1) Intermediate carpal bone
2) 4th carpal bone
What is being highlighted in the DLPMO view of the equine carpus?
the palmarlateral and dorsomedial highlighted
What is being highlighted in the DMPLO view of the equine carpus?
the dorsolateral and palmarmedial highlighted
is the accessory carpal bone more radiodense in the DLPMO or DMPLO?
DLPMO
How do you know youve achieved good positioning for a DLPMO equine carpal bone rad
space between MC3 and MC4
What carpal bone is being highlighted in the DLPMO of equine carpus
the radiocarpal bone
it is the most medial and this view highlights dorsomedial
What carpal bone is being highlighted in the DMPLO view of the equine carpus
the intermediate carpal bone
C1 in horses is present about
30% of the time
dont confuse with fragments
C5 in horses is present about
2% of the time
dont confuse with fragments
What do the 3 dorsoproximal-dorsodistal obliques highlight in the equine carpus?
1) Distal Radius
2) Proximal Row of carpal bones
3) Distal Row of carpal bones
*Common area of sclerosis in racehorses
optional to look for sclerosis or fracture
What are early osteoarthritis changes seen in the carpus
1) Increased intracapsular soft tissue
2) Osteophyte production
3) Enthesophyte production
4) Effusion
What are late osteoarthritis changes seen in the carpus
1) Narrowing of joint space
2) Cystic areas in subchondral boen
3) Ankylosis
How do you distinguish between intra vs extra-capsular swelling of the equine carpus
look at the position of the fat pad
if dorsal displacement = effusion/synovial proliferation
*Intracapsular fluid may be determined on the lateral projection by assessment of the dorsal fat pads of the antebrachiocarpal and middle carpal joints
What will you see with dorsal enthesophytes of the equine carpus
1) loss of fat pad
2) extracapsular swelling
What is a common site on the 3rd carpal bone of horses to see sclerosis
the radial facet
Sclerosis of the 3rd carpal bone is common in
1) racehourses
2) young TB in training (remodeling)
excessive sclerosis predisposes to fracture
What could result due to sclerosis of the 3rd carpal bone?
Fracture
What does sclerosis of the 3rd carpal bone in horses look like
there is no distinction between cortical and medullary bone
most common place is at the radial facet
What causes carpal bone fractures in horses
repetitive forceful trauma
hyperextension injury
What are the two kinds of carpal bone fractures?
1- Marginal Bone Fractures (Chip/Corner fx): occur at periarticular margins of carpal bones. Involves one subchondral bone surface
2- Slab: fracture extends through a carpal bone. Involves two another articular surface
How many articular surfaces do marginal carpal bone fractures include
one subchondral bone surface
How many articular surfaces do slab carpal bone fractures include
fracture extends through the carpal bone
involves two another articular surface
fractures of the carpal bone that occur at the periarticular margins of carpal bones
involves one subchondral bone surfaces
Marginal fractures
fractures of the carpal bone that extends through a carpal bone
involves two another articular surface
slab fractures
What will you see in chronic vs acute marginal carpal bone fracture
Acute: sharp angular margin, regional soft tissue swelling
Chronic: Rounded smooth margins +/- adjacent bone resoprtion +/- rim of sclerosis
How do you see C3 slab fractures
may need obliques to find the fracture
may only see on skyline (30%)
What should be aware of when evaluating the equine carpus to not confuse it with a fracture
Ulnar lateral styloid process
an ulnar remnant that fuses with the radius
incomplete fusion leads to a radiolucent line where it didnt fuse correctly
normal anatomical variant
an ulnar remnant that fuses with the radius
incomplete fusion leads to a radiolucent line where it didnt fuse correctly
normal anatomical variant
Ulnar lateral styloid process
what might cause avulsion carpal fractures in the horse
from the lateral palmar intercarpal ligament
most often incidental
What view is best to see avulsion carpal fractures
DP and DLPMO views
the most common fracture sites of the equine carpus are all
DORSAL
Antebrachiocarpal joint
1. Proximal intermediate CB
2. Proximal Radial CB
3. Distal medial radius
Middle Carpal joint
1. Distal Radial CB
2. Distal Intermediate CB
3. Proximal third CB
What are the most common fracture sites of the equine carpus
Antebrachiocarpal joint
1. Proximal intermediate CB
2. Proximal Radial CB
3. Distal medial radius
Middle Carpal joint
1. Distal Radial CB
2. Distal Intermediate CB
3. Proximal third CB
all are dorsal
what makes an osseous cyst like lesion clinical
if it communicates with the articular space,
otherwise it is usually incidental and not associated with lameness
Why are horses with osseous cyst like lesions in the carpus not typically lame
cysts seen in 2nd, ulnar, radial carpal bones are ofthe deep and in bone and insignificant
ulnar cysts like lesions may be incidental- usually associated with rhe lateral intercarpal ligament
can be clinical if communicate with articular surface
bony protrusions occassionally seen on the caudal aspect of the distal radius along midline
can be either osteochondromas or exostosis
Osteochondromas tend to be ______ to the physis while exostosis is ______ to the physis
Osteochondromas: cartilage capped exostosis, proximal to the physis
Exostosis: at the level of the physis
What are radiographic signs of equine infection
-Soft tissue swelling
-Effusion
-Irregular subchondral radiolucencies
+/- periosteal proliferation
+/- degenerative joint disease
What are the major differences between foal and adult septic joints
Foal: Hematogenous
Adult: Direct inoculation
how is valgus and vargus named
around the joint
ex: carpal valgus
an angular limb deformity where the carpus is located more medially and the limb is angled outwards
carpal valgus
What are different causes of carpal angular limb deformities in foals
-Ligamentous
-Differential growth (physis)
-Differential growth (Epiphysis)
-Differential growth (carpal bones)
-Carpal bone collapse/crush injury
*Often a combination of these
T/F: the are abnormally shaped cuboidal bones in ligamentous angular limb deformities
False- normal bones, just mild to moderate incomplete ossification
mild to moderate incomplete ossification of the cuboidal bones (resulting in wider joints)
ligamentous angular limb deformities
ligamentous angular limb deformities
mild to moderate incomplete ossification of the cuboidal bones (resulting in wider joints), not supporting joints appropiately
normally shaped cuboidal bones
normal epiphysis/physis
how can incomplete ossification lead to angular limb deformities
when the animal goes to bear weight it will put pressure and lead to deformities
poor prognosis
What are the three standard radiographs in the equine stifle
1) Lateromedial
2) Caudocranial
3) Caudo45lateral- craniomedial-oblique
Why are caudocranial projection done in horse stifles
Because it is easier to have the plate on the cranial aspect of the stifle
How many patellar ligaments do horses have
3 (dogs just have 1)
horses have 3 and asymmetrical trochlear ridge to lock patella in place
The cranioproximal-Craniodistal oblique of the equine stifle is also called the
Skyline Patella
What are other non-standard equine stifle radiograph views you may do
1) Cranioproximal- Craniodistal oblique (Skyline Patella)
2) Flexed lateromedial oblique- highltinging medial trochlea
What trochlea is larger in the horse stifle
medial trochlea
What are the three joints spaces that make up the equine stifle
1) Femoropatellar joint
2) Medial femorotibial joint
3) Lateral femorotibial joint
Made of the synovial structures: Joints, tendon sheaths, bursae
fluid-filled sacs that cushion and lubricate the body’s joints and muscles, allowing for smooth movement.
bursae
a protective layer of connective tissue that surrounds some tendons in the body.
tendon sheath
What are radiographic findings of the equine stifle that you can see on radiographs
1) Joint space narrowing (possibly damage to meniscus or
2) Osteophyte production (medial is most common)
3) Joint capsule enthesopathy (where the joint capsule inserts)
4) smooth bone resorption at the medial condyle
With osteoarthritis of the equine stifle, it is most common to see ostephyte production on what aspect
the medial aspect -
With osteoarthrosis of the equine stifle, where do you typically see smooth bone resorption
medial epicondyle
What might cause artificial narrowing of the equine stifle
if taken at an incorrect angle
What equine joint capsules communicate>
Femoropatellar joint capsule communicates with the medial femorotibial joint capsule
and the lateral femorotibial joint capsule (25%)
Medial and lateral femorotibial joint capsules do not communicate
T/F: Medial and lateral femorotibial joint capsules communicate with each other
False
T/F: Femoropatellar joint capsule communicates with the medial femorotibial joint capsule
True
T/F: Femoropatellar joint capsule communicates with the lateral femorotibial joint capsule
True- but only in 25%
Is the fibula lateral or medial to the tibula
lateral
is the medial or lateral tibial eminence taller
medial
Why is it hard to see effusion/synovitis in equine stifle
because there is increased intracapsular soft tissue volume
What are the two manifestations of equine stifle osteochondrosis
1) Osteochondrosis of femoral trochlear ridge and patella
2) Osseous cyst-like lesions of the medial femoral condyle (Cyst like lesions may result from trauma)
In osteochondrosis of the equine stifle, cyst-like lesions are most commonly seen on the
1)medial femoral condyle
2) Medial tibial condyle
3) LFC (rare)
(may result from trauma)
Are cyst-like lesions more common in the medial femoral condyle or lateral femoral condyle
medial femoral condyle
In equine stifle osteochondrosis, where do you typically see fragmentation/ concave defects
1) Lateral femoral trochlea
2) Patella
3) Medial femoral trochlea
a manifestations of equine stifle osteochondrosis
most common site for a subchondral bone cyst
often bilateral so take rads of contralateral stifle
can be articular or nonarticular
Medial Femoral condyle osseous cyst like lesion
What should you do if you notice an osseous-cyst like lesion of the medial femoral condyle in a horse
take rads of the other stifle because 50-60% of the time is bilateral
What is the best view to screen for common OC lesions in the horse stifle
Caudolateral-craniomedial oblique
this view highlights the lateral trochlear ridge and medial femoral condyle
What are the two most common osteochondrosis sites of the equine stifle
1) Medial femoral condyle cyst like lesions
2) Lateral femoral trochlea fragmentation / concave defects
If you had to choose one 1 view to screen for OC then do the Caudolateral-craniomedial oblique view
What appearance does the foal’s stifle look like?
irregular trochlear ridges - require 6-9 months for ossification (dont not confuse with osteomyelitis)
tibial apophysis and patella can also be irregular
radiograph the other limbs to compare
When do the foal’s trochlear ridges ossify
6-9 months
What might you see on radiographs that might tell you a foal has a septic joint
Soft tissue swelling
+/- gas
+/- bone lysis
Where do equine tibial stress fractures typically occur
mid to distal diaphysis
may not see radiographic changes initially
T/F: tibial eminence fractures in horses are avulsion fragments
False
What are the 4 standard routine tarsus views in equine
1) Lateral
2) DP
3) DMPLO
4) DLPMO
Is the calcaneous medially or laterally located
laterally
In what view do you see larry’s nose (lateral trochlea) of the equine tarsus
DMPLO
What are optional equine tarsal radiographs you can take
1) Flexed Skyline
2) Flexed lateral
What is a flexed lateral tarsus view of equine tarsus important for
to exposes more of the trochlea of the talus
What structure runs over the sustentaculum tali
*DDFT (runs medially)
while the SSFT runs over the top of the calcaneous
The horses has _____ calcaneal bursa
3 (runs between SSFT and calcaneous)
osteoarthritis/ osteoarthrosis of the distal intertarsal and tarsometatarsal joints
Bone Spavin
Bone spavin is osteoarthritis/osis of the
distal intertarsal and tarsometatarsal joints
What is most common location of osteoarthritis of the tarsus
dorsomedial
Osteoarthritis of the tarsus is more likely to show clinical signs if it
is located proximately
What are different degenerative changes seen in the equine tarsus osteoarthrosis
1) Medullary and subchondral bone sclerosis
2) Subchondral blone lysis/erosive changes/resorption
3) Periarticular ostephytes
4) Joint collapse/fusion: ankylosis
What are the different joint spaces in the equine tarsus
1) Talocalcaneal
2) Proximal intertarsal
3) Distal intertarsal
4) Tarsometatarsal
What two joints of the equine tarsus communicate with each other
Tarsocrural and proximal intertarsal joint
Distal intertarsal joint and tarsometatarsal joint
what is seen in early septic arthritis
marked intracapsular swelling
What is one of the most commonly affected joints in the horse for osteochondrosis
Tarsocrural joint and stifle
What are the most common sites to see equine osteochondrosis of the tarsocrural joints
1) Distal intermediate ridge of tibia (DIRT)
2) Lateral trochlear ridge of talus
3) Medial malleous > lateral malleoulus
4) Medial trochlear ridge of the talus
What is the most common place to see osteochondrosis in the tarsocrural joint of a horse
Distal intermediate ridge of tibia (DIRT)
What is the second most common place to see osteochondrosis in the tarsocrural joint of a horse
Lateral trochlear ridge of talus
If you could only take one view to screen for the two most common OC lesions of the equine tarsus, what would you pick
DMPLO-
This highlights distal intermediate ridge of the tibia and the lateral trochlear ridge
IS OCD more common in the lateral or medial malleolus in horses
Medial malleolus
What view do you need to detect a horse with OCD of the medial malleoulus
Dorso10lateral- plantaromedial oblique
fractures of the tarsus are generally rare but when they occur they are
1) slab fractures of the third and central tarsal bones
2) stress fractures of tibia cochlea
3) traumatic calcaneus fractures
4) avulsion fractures associated with collateral fragments
