External Skeletal Fixation Flashcards by Lindsay Patterson

How is external skeletal fixation accomplished?

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

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How do fx heal with external fixation?

By secondary bone healing

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What 3 types of fractures are external fixators used for?

Fx of appendicular skeleton
Spinal fx/luxation
Mandibular fractures

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What are 4 other uses (beyond fx fixation)?

Correcting of angular limb deformities
Limb lengthening
Arthrodesis
Joint immobilization

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What is arthrodesis?

Biologically fuse a joint (commonly carpus or tarsus)

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What are the 2 components of an ESF construct?

Pins inserted thorugh near and far cortex

Pins secured with specialized clamps and connecting bars

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What are the 4 different pin types?

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

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What is a positive profile pin?

Threads are outside the core diameter

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What is a negative profile pin?

Threads are inside the core diameter

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What is the strongest pin type?

Positive profile

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What are 3 rules for placement of the transfixation pins?

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

Place pins in area with little soft tissue

Avoid important neurovascular structures

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

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

1/2 the bone diameter

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How far are the clamps placed from the skin?

1cm

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How close do you want the connecting rod to be?

As close as possible

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What strain types can an ESF counteract?

Tension
Rotation
Bending
Axial Compression

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What are 7 ways you can strengthen ESF Rigidity?

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

What is the most stable pin distribution?

Pins close to the ends of the bone and fracture.

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

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

What is dynamization?

Planned decraesed of the stability

What is a Type 1A construct?

Unilateral-uniplanar

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

What is a Type 1B construct?

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

NOTE: Interconnecting bars increase rigidity

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

Type 1A and 1B

What is a Type 2A construct?

Bilateral-uniplanar | Full pins

What is a Type 2B construct?

Bilateral-uniplanar | Combo of half and full pins

What is a Type 3 construct?

Bilateral-biplanar

How do the construct stiffnesses compare?

Type 3 > Type 2 > Type 1

What is a circular external skeletal fixator (CERF)?

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

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

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

What is a hybrid fixator?

Uses components of linear and circular external skeletal fixators

What is a hybrid fixator useful for?

Treatment of metaphyseal fractures

How is a hybrid fixator useful for treating metaphyseal fractures?

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

What are 3 benefits of using ESF with acrylic frames?

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

What is dynamization?

Incremental destabilization of the construct

What is the benefit to dynamization?

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

When would you start dynamization?

At ~6weeks post repair

What must be present to achiece the benefits from dynamization?

Callus

What type and grade of fracture are ESFs useful for?

Grade II and III open fractures

What are 5 benefits to using an ESF?

- 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

What are 5 disadvantages of ESFs?

- 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

What are 5 complications associated with ESFs?

``` Pin tract drainage Loosening of pins/wires Osteomyelitis Ring sequestrum Nerve or vascular damage ```

What causes loosening of pins?

Pin-bone interface sustains high stress loads NOTE: Loose pins and wires must be removed

What is a ring sequestrum?

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