External Skeletal fixation (lewis) Flashcards
Indications for external skeletal fixation
Comminuted fx Open fx infected/nonunion fx athrodesis Trans-articular stabilization limb deformities
main advantage of external fixation
counteract axial (compressional), bending, and rotational forces
what does Type 1 half pin splint mean
pins pass through both cortices but only one skin surface
Type 1 unilateral
pins go in on same side
Type 2 full pin
pins pass through both cortices and two skin surfaces
Is a type 1 or 2 fixator more stable
2
What locations are type 2 fixators limited to
distal to elbow or stifle
Modified type 2 use both
half and full pin splintage
Advantages of modified type 2
easier to apply with comparable stability
Type 3 splint
both half and full pin
Biplanar
bilateral
Characteristics of type 1 fixator
half pin
uniplanar
unilateral
Characteristics of type 2 fixator
full pin
uniplanar
bilateral
Indications of half pin
cantilever bending
less bulk
Indication of full pin
four point of bending
more stable
advantage of partially threaded pin
greater resistance to axial extraction in cortical bone
Advantage of negative profile pin
less resistant to bending forces because of smaller diameter
Advantage of positive profile pin
superior stiffness and axial extration
What is the weakest link in an external fixation construct
bone-pin interface
Disadvantage of Kirschner-Ehmer apparatus
really difficult to place
Uses lots of pins
What does the SK system allow
pre-drilling of pilot holes and increased variability in fixation pin diameter with better mechanics
What should you place pins through for external fixators
small incisions
What should the drill core be compared to the fixation pin
.1mm smaller
What speed/torque should the drill be for fixations pins
low speed
high torque
Fixation pin should not exceed what percentage of the diameter of the bone
30%
Advantages of acrylic fixators
Pins variable diameter, don’t have to be placed in same longitudinal plane,
Radiolucent
Min. distance between connecting column and the cis-cortex of the bone
Lightweight
Limited inventory and expense
Disadvantages of acrylic fixators
Difficult to maintain reduction if used for primary fixation
Hot, can burn
Fumes are toxic
Difficult to adjust
