Flashcards in ESF and MIO Palmer 2012 VCNA Deck (24)
most common complications with ESF?
premature pin loosening and pin tract inflammation (Fitzpatrick 2008)
_______ _________ of fixation pins is proportional to their radius raised to the ______ power? Its also related to ______ _______ to the ______ power
Bending stiffness, 4th power.
Pin length to the 3rd power.
The fatter the fixation pin (no more than 20-30% diameter of the bone) and the closer its attachment to the connecting bar is to its insertion in the bone the more stiff it is.
Proportionate loss of bone strength occurs with incremental increases in circular cortical defect size greater than __% of the bone diameter. Why do you care
Transfixation pin size should not exceed this to avoid a stress riser
Circular ESFs are typically applied with ___ mm non-threaded fixation wires under tension.
While Kirschner wires with a standard trocar tip can be used as fixation wires, purpose-specific fixation wires with a ______________ cutting point are preferred, because they cut much more smoothly across the cortex and are less prone to deviating from their intended directional path
An intramedullary pin approximately __% the diameter of the bone is often used to maintain approximate axial alignment of femur or humerus fractures while the ESF device is applied
ESF pins can be placed in the cranial surface of the femur provided they are in the proximal approximately __% of the bone
Increasing the number of fixation pins per bone segment (up to __ pins per segment) increases the_________ of the construct, decreases the _____ _____ applied to each pin, and reduces the incidence of ________ _____ ______________.
4; stiffness; pin bone interface stress, premature pin loosening, bone resporption around the pin
Ratio between the change in gap width in relation to the original gap width
Hematoma and granulation tissue can tolerate strains up to _____%? As granulation fills the fracture zone, there is less motion and, thereby, less fracture gap strain. This reduced strain allows for proliferation of fibrous connective tissue that can tolerate ___% strain and then proliferation of fibrocartilage with a ______% strain tolerance. This progression to stiffer tissues continues until fracture gap strain approaches ___%, a mechanical environment in which lamellar bone can form.
100, 20, 10, 2
True or False
acrylic connecting bar - transfixation pin junction is a stiffer and stronger frame compared to frames of stainless steel pin-connecting bar clamp
Generally frame stiffness with respect to bending, torsion and shear increases with increased complexity (type III stiffer than type I) with one exception
Type Ib is more resistant to shear than Type II
What affect does adding a second connecting bar to a type Ia frame have?
Increases resistance to axial load (stiffness per tobias) by a factor of 2.5
What affect does adding a solid augmentation plate to a type Ia frame connecting bar have
4.5 fold increase in axial stiffness and medial-lateral bending.
2 fold increased stiffness in cranial-caudal bending
How does adding a second stainless steel connecting bar to a type Ia frame compare to adding a solid augmentation plate?
The double bar Ia construct will be 80% stiffer in axial compression and 170% stiffer in medial-lateral bending
How does a dbl bar Ia compare to Type IIb and Type IIa with respect to axial stiffness. Especially if its a larger diameter carbon fiber type?
Approximately equal to the type IIb and ~50% of the type IIa.
What negates the addition of larger diameter connecting bars?
Frames using two or more full pins (per tobias - unclear if that means per fragment)
In more advanced frames (type II and III) increasing mechanical stiffness is reliant mostly on ________? And how?
The transfixation pins -
By varying the thickness, number per fragment, and orientation along the frame
What angle should a smooth pin be placed and why
~70 degrees to the long axis of the bone
Enhances pin bone interface purchase and increases stiffness of the frame
General rules for pin placement
Place evenly along fragment, no closer than 3 times their width or 1/2 the bone width from joints/fracture edges, use safe corridors, 2-3mm skin incision then bluntly move soft tissues, pre-drill with slightly smaller drill bit, keep rpms under 150 while drilling pin, ideally 3-4 pins per major bone frag (no need for more than 4)
When can you utilize off set pin angles? How much of an offset do you want if you do? And why would you?
You can utilize offset pin angles when using acrylic for the connecting rod. If you are you want ~60 degrees of offset between pins because it has been shown to increase type Ia frame stiffness in axial compression and cranial-caudal static loading by 4-5 fold
There are 10 ways to increase frame stiffness. 5 are specific for certain types of x fix. Name the OTHER 5
-Larger connecting rods (negated if use 2 or more full pins)
-Position connecting bar closer to skin
-Increase the # of transfixation pins per construct (no benefit to more than 4 in a fragment)
-Increase the thickness of the transfixation pin (limited by bone size - no more than 20% of bone size)
-Increase complexity of the frame (add more full transfixation pins)
There are 10 ways to increase frame stiffness. 5 are specific for certain types of x fix. Name them
-Use acrylic based connecting bars (free form)
-60 degree off set of transfixation pins (can only do with free form)
-70 degree offset to long axis of bone if using smooth pins (no need if threaded pins)
-add a second connecting bar to a type Ia frame
-add a solid external augmentation plate to a type Ia frame