External Skeletal Fixation Flashcards
How is external skeletal fixation accomplished?
By using percutaneous pins or wires attached to external construct to stabilize fx fragments
How do fx heal with external fixation?
By secondary bone healing
What 3 types of fractures are external fixators used for?
Fx of appendicular skeleton
Spinal fx/luxation
Mandibular fractures
What are 4 other uses (beyond fx fixation)?
Correcting of angular limb deformities
Limb lengthening
Arthrodesis
Joint immobilization
What is arthrodesis?
Biologically fuse a joint (commonly carpus or tarsus)
What are the 2 components of an ESF construct?
Pins inserted thorugh near and far cortex
Pins secured with specialized clamps and connecting bars
What are the 4 different pin types?
Smooth pin (vs. threaded)
Positive profile
Negative profile
Center vs. end threaded
What is a positive profile pin?
Threads are outside the core diameter
What is a negative profile pin?
Threads are inside the core diameter
What is the strongest pin type?
Positive profile
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
What 2 things are important to remember about placing the percutaneous pins?
Place pins in area with little soft tissue
Avoid important neurovascular structures
Although you should have 2 pins in each bone segment, what is the ideal number?
3
How far should pins be placed from the fracture and each other?
1/2 the bone diameter
How far are the clamps placed from the skin?
1cm
How close do you want the connecting rod to be?
As close as possible
What strain types can an ESF counteract?
Tension
Rotation
Bending
Axial Compression
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
