Equine Foot/Pastern Flashcards

1
Q

describe the anatomy of the pastern bone (3)

A
  1. a saddle joint formed from the distal aspect of the proximal phalanx (P1) and the proximal aspect of the middle phalanx (P2)
  2. bound dorsally by common or long digital extensor tendon; pretty limited range of motion
  3. palmar/plantar support structures:
    -distal sesamoidean ligaments: back of P1 and P2
    -SDFT and DDFT
    -proximal and distal digital annular ligaments: like a sleeve to hold flexor tendons in place
    -medial and lateral collateral ligaments: provide stabilization
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2
Q

describe physical exam of the pastern (5)

A
  1. pastern region should be symmetric and free of swelling or bony enlargement
  2. pastern injuries are rarely bilateral (but OA may be), so always compare with contralateral limb
  3. abnormalities (swelling or bony enlargement) usually obvious because of minimal soft tissue in the area
  4. lameness associated with pastern region can be subtle to severe depending on injury
    -generally, injuries involving the PIPJ or DFTs cause obvious lameness
    -lameness due to early strains of distal sesamoidean ligaments may be mild
  5. pain often exacerbated by distal limb flexion or lunging with affected limb on inside of circle
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3
Q

what are 5 differential diagnoses for disorders of the pastern region?

A
  1. osteoarthritis (OA)
  2. osteochondrosis (OC)
  3. fractures
  4. infection
  5. tendon/ligament injuries
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4
Q

describe diagnostic procedures for the pastern region

A
  1. regional nerve blocks (some complications)
    -PIPJ not always completely anesthetized by abaxial sesamoid block, so a low 4 point block may also be necessary; beware of anesthetic migration!
    -AVOID nerve block if fracture suspected
  2. intra-articular anesthesia: pastern is one of the harder joints to block/inject bc crappy landmarks
  3. diagnostic imaging:
    -rads/US for initial characterization of injury
    -nuclear scintigraphy/bone scan: isotope binds in higher rates of bone turnover; good for pelvis!
    -CT; helpful for pre-op plan of fracture repair
    -MRI
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5
Q

describe tendon/ligament injury

A
  1. most frequently occurring (in order) in forelimb are:
    -superficial digital flexor tendon
    -oblique sesamoidean ligament
    -deep digital flexor tendon
    -straight distal sesamoidean ligament
  2. tendon/ligament injuries are less common in pastern region of hindlimb
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6
Q

describe orthopedic injuries in pastern region

A
  1. P1 fractures most often in racing breeds
  2. P2 fractures most common in western-type activity horses
  3. treated with internal fixation if orientation of fracture allows
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7
Q

describe osteoarthritis of the proximal interphalangeal joint

A
  1. also called high ringbone
    (low ringbone = OA of coffin joint)
  2. predispositions: jumping, dressage, western-type activities
  3. treatment:
    -mild OA: NSAIDs and IA anti-inflams

-advanced: surgical arthrodesis: better outcome with hindlimb than forelimb (less weight on hind end); can get away with this because PIPJ is a relatively low motion joint so can do and still have an athletic career

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8
Q

describe osteochondrosis of proximal interphalangeal joint

A
  1. less common than in other joints in horses
  2. osteochondral fragments associated with OC tend to occur dorsally on palmar/plantar eminence of P2
  3. arthroscopic removal possible, but low mobility in joint = hard to get in to operate
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9
Q

describe subluxation of the PIP joint

A
  1. uncommon!
  2. medial/lateral subluxation is due to severe injury to the collateral ligaments
  3. palmar/plantar subluxation usually follows a severe traumatic soft tissue innury
    -complete tear of distal sesamoidean ligaments
    -SDFT branch injury
  4. treatment of med/lateral palmar/plantar:
    -conservative management with external coaptation or surgical arthrodesis
  5. dorsal subluxation:
    -can occur without any identifiable structural abnormalities or soft tissue structures
    -occurs primarily in hindlimbs of young horses
    -lameness usually absent or mild
    -treatment similar to other sublux types
    -subsequent damage to stabilizing soft tissue structures more likely with more chronic subluxation
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10
Q

describe distal limb flexor anatomy

A
  1. SDFT inserts on distal P1 and proximal P2, NOT on P3, so fetlock contracture = SDFT
  2. DDFT insert on flexor cortex of P3 (only flexor insert on P3); if fetlock normal but heel off ground = DDFT
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11
Q

what is the etiology of distal limb flexural deformity (2)?

A
  1. congenital: usually neonates
    -uterine malposition (big foal little mare)
    -teratogenic insults: toxin ingestion in utero
    -genetic defects
  2. acquired: any age, chronic pain
    -physitis
    -OC
    -degenerative joint disease
    -soft tissue injury
    -infection
    pain = reflexive muscle contraction = tendon restructuring and loss of elastic capability
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12
Q

describe clinical presentation of congenital versus acquired distal limb flexural deformity

A

congenital: foal born unable to stand and knuckling over

acquired:
-abnormal fetlock angle
-heel of foot not toching ground
-abnormal hoof growth

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13
Q

describe diagnostics and treatment of congenital versus acquired distal limb flexural deformity and general prognosis

A

congenital:
-physical exam: unable to manually extend distal limb to normal position
-treatment:
–bandage/splint
–high dose oxytetracycline (diluted in saline) IV once daily for up to 3 days to prevent influx of calcium ions into muscle fibers to allow some relaxation of tendon

acquired:
-physical exam: distal limb does not fully extend when weight bearing, heel not touching ground, abnormal hoof growth rate (heel > toe)
-treatment:
–early (<1 week from onset): nutritional correction, farriery (if DDFT), pain management
–advanced: surgery and farriery (accessory ligament (of SDFT or DDFT) desmotomy)

prognosis:
-dependent upon duration
-generally better for congenital than acquired

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14
Q

know which accessory ligaments associated with SDFT and DDFt

A

SDFT: accessory ligament/radial check ligament is more proximal; comes off back of radius

DDFT: accessory ligament/inferior check ligament is more distal and comes off back of MC 3

cut the accessory ligament attached to the contracted ligament to treat flexural deformity!!

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15
Q

describe navicular apparatus

A
  1. collateral sesamoidean ligaments hold navicular bone in place/suspensory ligaments of navicular bone
  2. distal sesamoidean/impar ligaments: hold navicular bone in pace distally
  3. DDFT forms navicular bursa as it passes by to attach to P3
  4. also called the podotrochlear apparatus, nav bone = distal sesamoid bone
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16
Q

describe deep digital tendinopathy (6)

A
  1. MRI hella important for diagnosis!! only way to image this region
  2. etiology:
    -acute traumatic injury or
    -chronic degenerative overuse injury
    -stress on tendon exceeds yield point of the tendon fibers
  3. clinical presentation:
    -variable degree of lameness; dependent upon severity of injury
  4. diagnostics:
    -lameness evaluation/exam
    -regional anesthesia
    -imaging: rads, US, MRI (usually only way to get an answer)
  5. treatment:
    -pain management: NSAIDs (pirocoxib = better for >1 week)
    -intralesional biologic injection
    -farriery: objective is to decrease tension on the tendon, heel elevation common
    -time: approx 1 year but never heal back to same structural strength as pre-injury and re-injury common
  6. prognosis: dependent on severity of injury, may not be able to return to previous level of work
17
Q

describe distal interproximal joint collateral ligament desmopathy

A
  1. etiology: acute traumatic injury or chronic degenerative/overuse injury leads to strain that exceeds yield point of ligament fibers
  2. clinical presentation: varying degrees of intermittent/circumstantial lameness
  3. diagnostics:
    -lameness exam
    -regional anesthesia
    -imaging: rads, US, MRI
    -stand horse on a wedge block to shorten distance between ligament origin and insertion on wedged side and increasing it on other side to see if can make lameness more severe before resorting to MRI
    -ultrasound only useful if lameness in proximal 1/3, can’t see if deeper
  4. treatment:
    -pain management: NSAIDs
    -intralesional biologic injection: more challenging location than DDFT
    -farriery: objective is to decrease tension on the affected ligament; wider ground surface area on one side versus the other will make a difference on soft footing (functionally wedging affected side of the foot on soft footing) to decrease strain on injured ligament)
    -time