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Small Animal Surgery > External Skeletal Fixation > Flashcards

External Skeletal Fixation Flashcards

1
Q

How is external skeletal fixation accomplished?

A

By using percutaneous pins or wires attached to external construct to stabilize fx fragments

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2
Q

How do fx heal with external fixation?

A

By secondary bone healing

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3
Q

What 3 types of fractures are external fixators used for?

A

Fx of appendicular skeleton
Spinal fx/luxation
Mandibular fractures

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4
Q

What are 4 other uses (beyond fx fixation)?

A

Correcting of angular limb deformities
Limb lengthening
Arthrodesis
Joint immobilization

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5
Q

What is arthrodesis?

A

Biologically fuse a joint (commonly carpus or tarsus)

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6
Q

What are the 2 components of an ESF construct?

A

Pins inserted thorugh near and far cortex

Pins secured with specialized clamps and connecting bars

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7
Q

What are the 4 different pin types?

A

Smooth pin (vs. threaded)
Positive profile
Negative profile
Center vs. end threaded

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8
Q

What is a positive profile pin?

A

Threads are outside the core diameter

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9
Q

What is a negative profile pin?

A

Threads are inside the core diameter

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10
Q

What is the strongest pin type?

A

Positive profile

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11
Q

What are 3 rules for placement of the transfixation pins?

A

Pin diameter should be no more than 25% of bone diameter
Placed percutaneous through small incisions
At least 2 pins per bone segment required

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12
Q

What 2 things are important to remember about placing the percutaneous pins?

A

Place pins in area with little soft tissue

Avoid important neurovascular structures

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13
Q

Although you should have 2 pins in each bone segment, what is the ideal number?

A

3

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14
Q

How far should pins be placed from the fracture and each other?

A

1/2 the bone diameter

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15
Q

How far are the clamps placed from the skin?

A

1cm

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16
Q

How close do you want the connecting rod to be?

A

As close as possible

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17
Q

What strain types can an ESF counteract?

A

Tension
Rotation
Bending
Axial Compression

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18
Q

What are 7 ways you can strengthen ESF Rigidity?

A 
Frame type
Double bar
Interconnecting bars
Reduce bone-connecting bar distance
Pin distribution
Increased number of pins
larger diameter of pins and connecting bar
19
Q

What is the most stable pin distribution?

A

Pins close to the ends of the bone and fracture.

20
Q

What are 4 ways you can decrease the rigidity of the ESF?

A

Frame type
Pin distribution
Decreased number of pins
Smaller diameter of pins and connecting bar

21
Q

What is dynamization?

A

Planned decraesed of the stability

22
Q

What is a Type 1A construct?

A

Unilateral-uniplanar

NOTE: Half-pin because pins don’t come all the way out the other side

23
Q

What is a Type 1B construct?

A

Unilateral-bipolar
Pins placed 60-90 degrees from one another (half-pin

NOTE: Interconnecting bars increase rigidity

24
Q

What types of construct can you use on the humerus and femur?

A

Type 1A and 1B

25
Q

What is a Type 2A construct?

A

Bilateral-uniplanar

Full pins

26
Q

What is a Type 2B construct?

A

Bilateral-uniplanar

Combo of half and full pins

27
Q

What is a Type 3 construct?

A

Bilateral-biplanar

28
Q

How do the construct stiffnesses compare?

A

Type 3 > Type 2 > Type 1

29
Q

What is a circular external skeletal fixator (CERF)?

A

Small diameter fixation wires connected to rings which are in turn connected by rods

30
Q

What are 3 indications for using a circular external skeletal fixator?

A

Complicated fractures of the tibia and radius
Distracted osteogenesis
Correction of angular limb deformities

31
Q

What is a hybrid fixator?

A

Uses components of linear and circular external skeletal fixators

32
Q

What is a hybrid fixator useful for?

A

Treatment of metaphyseal fractures

33
Q

How is a hybrid fixator useful for treating metaphyseal fractures?

A

Thin wires allow for multiple sites of bone purchase in a smaller bone fragment.

34
Q

What are 3 benefits of using ESF with acrylic frames?

A

Can connect pins in various planes
Lightweight
Eliminates need for fixation clamps

35
Q

What is dynamization?

A

Incremental destabilization of the construct

36
Q

What is the benefit to dynamization?

A

Allows increased axial load bearing to the fracture to enhance callus hypertrophy and remodelling

37
Q

When would you start dynamization?

A

At ~6weeks post repair

38
Q

What must be present to achiece the benefits from dynamization?

A

Callus

39
Q

What type and grade of fracture are ESFs useful for?

A

Grade II and III open fractures

40
Q

What are 5 benefits to using an ESF?

A
  • Variety of construct options
  • Can be placed with minimal disruption of fx fragments
  • All implants removed after healed
  • Implants can be removed incrementally to slowly increase loading on the bone
  • Cost is relatively low compared to some internal fixators
41
Q

What are 5 disadvantages of ESFs?

A
  • Frequent rechecks required
  • Morbidity associated with skin-pin interface
  • Pin loosening, implant failure
  • External hardware poses a risk to fx and people/objects
  • Additional procedures required for destabilization and implant removal
42
Q

What are 5 complications associated with ESFs?

A 
Pin tract drainage
Loosening of pins/wires
Osteomyelitis
Ring sequestrum
Nerve or vascular damage
43
Q

What causes loosening of pins?

A

Pin-bone interface sustains high stress loads

NOTE: Loose pins and wires must be removed

44
Q

What is a ring sequestrum?

A

Pins can get really hot when placing them which can kill the bone cells around the pin if not properly lavaged

Small Animal Surgery (13 decks)

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