Pastern and fetlock Flashcards
Where is the pastern joint?
Between P1 and P2
Which ligaments/tendons lie at the palmar aspect of the pastern joint?
SDFT branch
Straight sesamoidean ligament
Oblique sesamoidean ligaments
Palmar scutum
Which ligament lies on the medial/lateral aspect of the pastern joint?
Collateral ligaments
Where does the distal sesamoidean ligament insert?
Onto the palmar/plantar scutum
Is the pastern joint a high or low motion joint?
Low
Is the pastern joint a high or low loading joint?
High
Where is the fetlock joint?
Between the 3rd metacarpal/tarsal bone and P1
Also proximal sesamoid bone
Which tendon is found at the dorsal aspect of the fetlock joint?
Common extensor tendon and extensor branch
Which tendons/ligaments are found at the palmar/plantar aspect of the fetlock joint?
Suspensory ligament
Collateral sesamoidean ligaments
Straight sesamoidean ligament
Oblique sesamoidean ligament
How is the fetlock joint stabilised?
Collateral/collateral sesamoidean ligaments
Is the fetlock joint a high or low motion joint?
High
The fetlock is primarily supported by which structure?
Suspensory ligament
Describe the initial investigation into pastern/fetlock problems
Clinical examination - Pain/lameness, swelling (synovial/soft tissue), heat, instability, ROM
Describe diagnostic analgesia of the pastern/fetlock
Perineural: ASNB (abaxial sesamoidean nerve block – blocks the foot and pastern); L4/6NB
Intra-synovial: PIPJ; MCPJ; (DFTS)
The L4 nerve block blocks which nerves?
Medial/lateral palmar and palmar metacarpal n.
The L6 nerve block blocks which nerves?
Medial/lateral plantar and plantar metatarsal n.
Dorsal metatarsal n. (med/lat)
Which radiographic views would you use for the pastern?
DP = front to back
LM = side to side
DMPLO = 45 degree angle dorsomedial
DLPMO = 45 degree angle dorsolateral
Which radiographic views would you use for the fetlock?
DP, LM, DMPLO, DLPMO, flexed LM
Which other imaging techniques can be used in the pastern/fetlock?
Ultrasonography
Advanced imaging e.g. nuclear scintigraphy, MRI or CT
Name 4 conditions of the equine pastern
Osteoarthritis
Osteochondrosis
Soft tissue injuries
Fractures/subluxation
What is a common term used to describe pastern osteoarthritis?
Articular ringbone
What is osteoarthritis?
Progressive destruction of articular cartilage with subchondral bone thickening and osteophyte production
What may severe cases of osteoarthritis have?
Cystic formation/joint collapse
How does arthritis occur?
Maybe insidious or secondary to other problem (e.g. trauma, sepsis, osteochondrosis)
What are the clinical signs of pastern osteoarthritis?
Lameness (mild to moderate)
Bony thickening over dorsal pastern
How is pastern osteoarthritis diagnosed?
Diagnostic anaesthesia: Perineural or intra-articular
Radiography
- Standard projections
- Changes often dorsal
How is pastern osteoarthritis managed?
- Rest/light exercise
- Intra-articular medication
- Shoeing
- NSAIDs
- Arthrodesis (surgical, chemical)
What is sclerosis?
Subchondral bone formation - an abnormal increase in density and hardening of bone
How common are osteoarthritis and osteochondrosis in the pastern?
Osteoarthritis = common
Osteochondrosis = uncommon
How does osteochondrosis manifest?
Osseous cysts (P1 or P2) or palmar/plantar osteochondral fragmentation
How is osteochondrosis managed?
Management often palliative
Guarded prognosis
Name 2 common soft tissue injuries of the pastern joint
SDFT branch injury
Distal sesamoidean ligament injury - Oblique or straight sesamoidean ligament
How do horses with soft tissue injuries of the pastern joint present?
Usually present acutely lame following traumatic injury
Moderate lameness and soft tissue swelling
What is the best method for diagnosing soft tissue injuries?
Ultrasonography
How are soft tissue injuries managed?
Rest, NSAIDs, monitor healing by ultrasound
Describe the main features of P1 fractures
Sagittal, frontal, comminuted
Often seen in racehorses
Describe the pathway of P1 fractures
P1 fractures begin at sagittal groove at articular surface
- Extend distally (short <30mm; long>30mm)
- Complete fractures exit lateral cortex or through PIPJ
Describe the features of P2 fractures
Palmar/plantar eminence, comminuted
Usually due to acute overload injury
What are the common clinical findings of pastern fractures?
Usually acute onset severe lameness +/- instability +/- joint effusion
How are pastern fractures diagnosed?
Radiography
How are pastern fracture managed?
- First aid stabilisation: Zone 1 external coaptation
- Conservative = Short, incomplete fractures
- Surgical = Internal fixation – most cases
- Euthanasia = Comminuted, open, unstable
What are the two main causes of pastern subluxation
Traumatic event (e.g. cattle grid/fence)
Fracture/subluxation common (e.g. avulsion fracture)
How do cases of pastern subluxation present?
Acute lameness/instability
Marked soft tissue swelling
How is pastern subluxation diagnosed?
Radiography +/- stress
How is pastern subluxation managed?
Initially stabilise through external co-aptation (zone 1) but often require pastern arthrodesis
List the main problems occurring at the equine fetlock
- PSB fractures
- Sesamoiditis
- Osteochondral fragmentation of P1
- Osteochondrosis
- Osteoarthritis
- Subchondral bone disease/POD
- Chronic proliferative synovitis
- Subluxation
What types of fractures can occur in the proximal sesamoid bone?
Apical (<30% of bone), mid-body, axial, basilar and comminuted
may be unilateral or bilateral
What are the causes of proximal sesamoid bone fractures?
Usually acute trauma but may be due to non-adaptive modelling
How do cases of proximal sesamoid bone fractures present?
Clinical signs usually acute lameness with swelling and pain on palpation +/- joint effusion
How are proximal sesamoid bone fractures diagnosed?
- Standard radiographic projections but may need additional oblique views
- Ultrasonography important as may also have concurrent SL injuries
Describe when conservative management of proximal sesamoid bone fractures is indicated
Uniaxial PSB fractures in foals
Non-articular
Describe when surgical management of proximal sesamoid bone fractures is indicated
Fragment removal (e.g. apical fracture removed arthroscopically)
Fracture repair (e.g.mid-body)
Describe when euthanasia for proximal sesamoid bone fractures is indicated
Biaxial/comminuted fractures
Define sesamoiditis
Inflammation around the soft tissues of the palmar fetlock
Increased size/no. vascular channels
Sesamoiditis is most commonly seen in which horses?
Young performance horses
Sesamoiditis may indicate which injury?
May be an indicator of SL branch/annular ligament injury
How is sesamoiditis managed?
Rest/NSAIDs + local cold therapy
Shockwave therapy in refractory cases
How is Osteochondral fragmentation of P1 managed?
- May not be clinically relevant (or relevant at high speed) so need to prove significance (e.g. diagnostic analgesia)
- Radiography: Check contralateral limb
- Fragment removal frequently performed arthroscopically
Name the clinical form of osteochondrosis
Osteochondritis dissecans
Describe the main features of osteochondrosis of the fetlock region
Includes OCD of the sagittal ridge of Mc/MtIII and osseous cysts of distal McIII
OCD may be seen as flattening of the sagittal ridge to separate fragmentation
Usually seen in young horses (1-4 fetlocks involved) with joint effusion +/- lameness
Describe management of osteochondrosis
Surgical removal of fragments (OCD) or curettage of the cyst
Describe fetlock osteoarthritis
Degenerative joint disease resulting in joint effusion, cartilage loss, osteophyte production and loss of joint function
May be secondary to trauma, sepsis, osteochondrosis
Describe the clinical findings of fetlock osteoarthritis
Lameness exacerbated by fetlock flexion; reduced ROM
Positive i/a anaesthesia
What would be seen on radiography of a fetlock with osteoarthritis?
Periarticular osteophyte formation (particularly proximodorsal aspect of P1 and dorsoproximal and dorsodistal margins of PSBs), modelling of proximal aspects of the dorsal and palmar sagittal ridges, subchondral bone sclerosis and joint space reduction
Describe management of mild/early cases of fetlock osteoarthritis
Intra-articular medication e.g. hyaluranon/ corticosteroids
Describe management of moderate cases of fetlock osteoarthritis
NSAIDs, i/a corticosteroids, IRAP, polyacrylamide gel
Describe management of severe cases of fetlock osteoarthritis
Arthrodesis (salvage)
Euthanasia
What is Palmar/plantar osteochondral disease
Degenerative condition of the distal condyles of young racehorses
How does palmar/plantar osteochondral disease occur in young racehorses?
Repetitive high strain on bone and articular tissues leading to cartilage loss with eventual collapse of the articular surface
Associated with repeated corticosteroid use?
Describe the clinical signs of palmar/plantar osteochondral disease
Mild/moderate lameness in 1 or more limbs localised to the fetlock
How does palmar/plantar osteochondral disease appear on radiography?
Minimal signs to focal increases in bone density (sclerosis) and change in contour of the subchondral bone
Advanced imaging include nuclear scintigraphy and MRI
How is palmar/plantar osteochondral disease in young racehorses managed?
Alteration in exercise schedule
Describe the aetiology of chronic proliferative synovitis
- Usually forelimb
- Chronic repetitive trauma to dorsal aspect of fetlock due to hyperextension
- Can lead to supracondylar bone lysis
What are the clinical signs of chronic proliferative synovitis?
Lameness, reduced range of motion, heat/pai
How does chronic proliferative synovitis present on radiography?
Crescent shaped bone loss distal McIII
Soft tissue swelling
How does chronic proliferative synovitis present on ultrasound?
Thickening of dorsal synovial pad
How is chronic proliferative synovitis managed?
Intra-articular medication; surgical resection
How does fetlock subluxation occur?
Often due to trauma
Disruption of the collateral ligaments +/- avulsion fracture
How is fetlock subluxation diagnosed?
Acute, severe lameness +/- overt luxation
Radiography +/- stress
How id fetlock subluxation treated?
Closed reduction + cast - Will fibrose but may end up with OA
Arthrodesis if unstable
