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Large Animal Surgery > Disorders of the Equine Foot & Navicular Disease > Flashcards

Disorders of the Equine Foot & Navicular Disease Flashcards

1
Q

What is navicular disease? At what age is this most commonly seen? What breeds are predisposed?

A

caudal heel pain - chronic, bilateral, progressive degeneration of navicular bone and apparatus

early middle-aged —> 7-9 y/o

  • Quarterhorses**
  • Warmbloods
  • Thoroughbreds
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2
Q

What kind of function does the navicular bone have?

A

distal sesamoidean bone - pulley function to decrease strain on DDFT as it changes direction to cross the coffin joint and decrease work of DDFT on P3 to increase mechanical effect

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3
Q

Label the bones and ligaments in the equine foot.

A
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4
Q

What 4 structures take part in the navicular apparatus?

A
  1. DDFT
  2. navicular bursa
  3. impar ligament
  4. collateral sesamoidean (suspensory) ligament of the navicular bone
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5
Q

What is the main etiology of navicular syndrome? What are 2 other possible etiologies?

A

conformation –> small feet, big body or underrun heels

  1. genetics
  2. chronic poor shoeing
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6
Q

How do horses present with navicular syndrome? What stride is characteristic?

A

unilateral or bilateral forelimb lameness with lame limb on the inside of the circle on hard ground

short, choppy stride, where they land toe first to keep DDF from flexing over the navicular bone

  • owner commonly thinks it is a shoulder issue
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7
Q

What 3 conformations are associated with navicular syndrome?

A
  1. long toe, low heel
  2. small feet
  3. contracted heels
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8
Q

Why do underrun heels predispose to navicular syndrome?

A

concentrated forces on the navicular apparatus in the heel

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9
Q

What is the preferred method of diagnosing navicular syndrome? What are 2 other common findings?

A

blocks to a PD nerve block - may need to add abaxial with pronounced discomfort (commonly bilateral and lameness will switch to the other side)

  1. sore over heels to hoof testers
  2. positive to coffin joint hyperextension (toe up = increased stress on DDFT)
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10
Q

What imaging can be used to diagnose navicular syndrome?

A
  • RADIOGRAPHS - bone
  • MRI - soft tissue and bone –> suspensory DDFT and impar ligament
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11
Q

What 3 things are required for imaging the equine foot to diagnose navicular syndrome?

A
  1. pull shoe
  2. clean foot meticulously with hoof knife
  3. pack foot with piece of Play Doh to remove air pockets
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12
Q

What 5 things are evaluated on lateral radiographs in possible cases of navicular syndrome?

A
  1. flexor cortex
  2. medullary cavity
  3. insertion of impar ligament
  4. insertions of navicular suspensory ligament to P2
  5. hoof balance
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13
Q

What 2 things are evaluated on DP radiographs in possible cases of navicular syndrome? What is characteristic of this view?

A
  1. hoof balance
  2. lateral and medial aspects (wings) of NB

NB superimposed on P2 and P3

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14
Q

What 3 things are evaluated on 60-65 degree DP radiographs in possible cases of navicular syndrome? When is this view used?

A
  1. insertions of navicular suspensory ligament on lateral and medial aspects of NB
  2. distal and proximal borders of NB
  3. shape of NB

if NB is completely superimposed on P@ on regular DP

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15
Q

What 4 things are evaluated on palmaroproximal palmarodistal oblique (skyline) radiographs in possible cases of navicular syndrome?

A
  1. flexor cortex
  2. medullary cavity
  3. corticomedullary junction
  4. shape of NB
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16
Q

What abnormalities are seen in this radiograph?

A
  • enthesophyte on insertion of impar ligament
  • sclerosis of medullary cavity

(navicular syndrome!)

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17
Q

What abnormalities are seen in this radiograph?

A
  • SEVERE enthesopathy on the navicular suspensory and impar ligaments
  • flattened palmar angle
  • sclerosis of NB (radiograph may be obliqued)
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18
Q

What is occurring in this radiograph?

A
  • YELLOW = cyst in navicular bone
  • PINK = synovial invagination (lollipop lesions) - rough flexor surface, can be normal but multiple are pathologic
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19
Q

Navicular bone, radiograph:

A

cyst

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20
Q

What is occurring in this radiograph?

A
  • YELLOW = defect in flexor cortex where the DDF glides over
  • BLUE = medullary sclerosis, loss of corticomedullary junction
  • PINK = increased synovial invaginations
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21
Q

What abnormalities are seen in this radiograph?

A
  • YELLOW = enthesophyte where navicular suspensory ligament attaches
  • PINK = mineralization of DDFT
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22
Q

What abnormalities are seen in this radiograph?

A
  • YELLOW = enthesophyte at the insertion of the navicular suspensory ligament
  • PINK = roughening of the abaxial surface of the navicular bone
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23
Q

What abnormality is seen in this radiograph?

A

severe sclerosis and loss of corticomedullary junction in the navicular bone

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24
Q

What abnormalities are seen in this radiograph?

A

synovial invaginations - lollipop lesions

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25
Q

What 5 structures can also be affected by navicular syndrome if the radiograph appears normal? What is used for a definitive diagnosis?

A
  1. DDFT
  2. impar ligament
  3. suspensory ligament of the navicular bone - may see mineralization at insertion
  4. collateral ligaments of DIP joint
  5. navicular bursa

MRI

26
Q

What is the first treatment option for navicular syndrome? What 4 options are commonly added?

A

corrective farriery

  1. corticoid steroid injection into coffin joint to diffuse into navicular structures or radiology guided into navicular bursa - Triamcinolone +/- HA
  2. NSAIDs
  3. osteoclast inhibitors - $$$, good for cystic lesions
  4. palmar digital neurectomy
27
Q

What 3 things are addressed in corrective farriery for navicular syndrome?

A
  1. ease breakover to shorten toe and lessen need for horse to go “up and over” in their gait
  2. support palmar structures
  3. address coffin bone palmar angle
28
Q

Navicular syndrome, breakover:

A

long toe increases stress of suspensory ligament and its insertion

29
Q

Which shoe best supports palmar structures?

A

A - relatively normal, could use more shoe causally

B - shoe covers more and offers best support for palmar aspects

C - long toe and unerrun heel = high stress and pressure on palmar angle

30
Q

How is the heel addressed in farriery of horses with navicular syndrome? What shoe is able to do this?

A
  • support palmar structures
  • use a 2-3 degree wedge or pad to raise heel

bar shoes - shoed in active months and left barefoot when less active

31
Q

What can happen when bar shoes are put on incorrectly?

A

contracted heels - too rigid, no room for ligaments to contract and relax

32
Q

What is the most common starting point for intra-articular corticosteroid injections for horses with navicular syndrome? Refractory cases?

A

coffin joint - easier to reach, communicates with navirular structures

radiograph-guided navicular bursa injection

33
Q

What NSAIDs are commonly used for horses with navicular syndrome?

A
  • Phenylbutazone
  • Firocoxib - good for chronic, long-term pain
34
Q

Why are osteoclast inhibitors used in navicular syndrome? What are 2 options?

A

slows progression of bony changes

  1. Clodronate (Oshphos)
  2. Tiludronate (Tildren)
    $$$
35
Q

Treating athletic horses with navicular syndrome:

A
36
Q

What is the prognosis of navicular syndrome like?

A

progressive disease that is managed, not cured

  • depends on response to treatment and soft tissue involvement
37
Q

When are palmar digital neurectomies used for treating navicular syndrome? What does it do? What are 2 important considerations?

A

improves lameness and extends career of horse —> semi-permanent nerve block, pathology is still there but horse doesn’t feel it

last resort to alleviate pain and does NOT cure the problem

  1. nerve regrowth is possible
  2. not recommended if there is concurrent soft tissue injury
38
Q

What 5 situations are amendable to palmar digital neurectomy to treat navicular syndrome?

A
  1. lameness significantly improves with a PD nerve block
  2. no ossification of DDFT
  3. no DJD in the coffin joint
  4. no roughening of the flexor surface of the navicular bone, which can lead to ruptured DDFT
  5. owner compliance is not questioned - needs careful foot monitoring following the surgery
39
Q

Palmar digital neurectomy:

A

cut ~cm to avoid immediate regrowth

40
Q

What are 5 potential complications following a palmar digital neurectomy?

A
  1. neuroma formation/neuritis***
  2. unnoticed injury to foot or abscess - loss of innervation and cannot feel pain
  3. DDFT rupture - toe still remains up
  4. coffin joint subluxation
  5. reinnervation - commonly within 3 years
41
Q

What is the difference between thrush and white line disease? What is the most common cause?

A

infection of the frog

infection of the white line - seedy toe

mixed anaerobic (Fusobacterium necrophorum), aerobic, and fungal infection

42
Q

What 4 conditions predispose to thrush and white line disease?

A
  1. MOISTURE
  2. poor hygiene
  3. poor hoof care
  4. reduced weight bearing
43
Q

What 3 clinical signs are associated with thrush and white line disease? When are radiographs recommended?

A
  1. smell
  2. hoof abnormalities
  3. lameness in severe cases

white line disease - determines extent

44
Q

What 4 treatments are used for thrush and white line disease?

A
  1. improve hoof care and stall hygiene
  2. debride damaged tissue (may require hoof wall resection with white line disease)
  3. copper naphthenate
  4. iodine
45
Q

What are cankers? In what horses are they most common? What is suspected to be the cause?

A

chronic inflammation and proliferation leads to hypertrophy of the sensitive lamina and degeneration of the superficial horn (looks like granulation tissue)

Draft horses

anaerobic bacteria

46
Q

What 3 signs are indicative of cankers? How does it compare to thrush?

A
  1. mild lameness
  2. soft, greasy, friable, proliferative tissue over frog and caudal heel
  3. yeasty smell

lameness is not as common with thrush, but there will be a more black exudate

(can affect multiple hooves)

47
Q

How are cankers treated?

A
  • debride
  • local Metronidazole +/- antifungals, corticosteroids
  • cryotherapy

months of treatment, can’t always cure

48
Q

What 3 conditions predispose to subsolar bruising?

A
  1. thin-soled horses + flat palmar angle
  2. wet conditions
  3. rocky ground
49
Q

What 2 signs are indicative of subsolar bruising?

A
  1. variable lameness worse on rocky ground
  2. diffusely positive to hoof testes due to soft sole (may leave an indentation)
50
Q

What 3 treatments are recommended for subsolar bruising?

A
  1. poultices
  2. shoes
  3. keep mud out of hoof
51
Q

What is one of the most common causes of severe lameness in horses? What is the pathogenesis? What are 4 possible etiologies?

A

subsolar abscesses

bacteria enters through failed hoof barrier, allowing pus to accumulate and pressure increases = pain!

  1. wet conditions
  2. sequela to a bad bruise (hematoma)
  3. solar puncture wound
  4. nail from shoe
52
Q

Subsolar abscess:

A

can break out for the coronet or heel!

53
Q

What are 4 signs of subsolar abscesses? What 2 strategies are used for diagnosis?

A
  1. acute onset severe lameness (DDx = fracture)
  2. increased digital pulse
  3. distal limb swelling
  4. soft spot at coronet
  • extremely positive to hoof testers over the area of the abscess
  • radiographs
54
Q

What are 6 methods of treating subsolar abscesses?

A
  1. pain relief - Phenylbutazone
  2. tetanus toxoid vaccine
  3. pare out abscess to allow ventral drainage
  4. soak foot in Epsom salts (magnesium sulfate) esp if uable to open abscess
  5. poultice foot
  6. protect foot - keep confined to clean, dry areas
55
Q

What are the 2 purposes of using foot poultice to treat subsolar abscesses?

A
  1. reduce inflammation - hyperosmotic sugar or Epsom salts, DMSO (clay poultice, Animalintex)
  2. harden hoof - hyperosmotic, tincture of iodine, Keratex (formaldehyde)
56
Q

Label the structures in the equine foot.

A
  • A = impar ligament
  • B = coffin joint
  • C = navicular bone
  • D = navicular bursa
  • E = suspensory ligament of the navicular bone
  • F = DDFT

(commonly affected by penetrating solar wounds)

57
Q

What areas highlighted in this hoof are commonly affected by penetrating solar wounds?

A
  • orange = navicular bone
  • purple = P3
  • caudal heel = DDFT

size and direction of nail matters!

58
Q

What should be done before removing FB from penetrating solar sounds?

A

radiograph –> use contrast to see if synovial structures are involved (then treat as synovial sepsis)

59
Q

What 5 things are included when treating penetrating solar wounds?

A
  1. broad spectrum antimicrobials
  2. local antimicrobials - intrasynovial, regional limb perfusion
  3. NSAIDs
  4. tetanus toxoid +/- antitoxin
  5. clean and disinfect sole and tract standing
    (refer if synovial structures are involved)

early aggressive treatment necessary

60
Q

How is synovial sepsis resulting from penetrating solar wounds treated?

A
  • surgical debridement under GA
  • synovial lavage
  • street nail procedure - hole in solararea into navicular bursa for drainage and shoeing
  • endoscopy - navicular bursa, DF, tendon sheath, coffin joint

Large Animal Surgery (32 decks)

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