External SKeletal Fixation Flashcards
What is true regarding acrylic-based ESF?
a. They generally cost more than conventional linear systems
b. They are stiffer at the pin-bar interface than conventional system
c. They generally are heavier than conventional linear systems
d. They do not need to engage all transfixation pins
B
True/False: In general, the increase in external skeletal fixator frame complexity was proportional to an increase in the mechanical strength and stiffness properties of the frame. The exception to this is type IIa frames have greater resistance to shear than type IIb frames.
False (Exception = type Ia better than type II)
Tre/False: • Placing a second connecting bar on a type Ia frame will increase the frame’s resistance to axial stiffness by a factor of 0.5.
false (2.5)
True/false The use of a solid external plate augmentation to a single stainless steel connecting bar will produce almost a 4.5-fold increase in axial stiffness and medial-lateral bending.
true
True/false A double stainless steel connecting bar type Ia frame will be 170% stiffer in axial compression and 80% stiffer in medial-lateral bending compared with the external augmented plate system.
(Switch 180 and 70)
Which of the following is true?
• A minimum of 4 wires per segment is recommended
• Pins should be > 20-25% of the bone width
• When using a wire tensioning over 30kg should be performed
• Smooth pins should be perpendicular, and positive profile pins should go in at a 70 degree angle
A is true
B (
Which of the following is false?
• A minimum of 2 pins is recommended
• A drill at a speed > 150 rpm is better than a hand chuck to prevent wobble with a hand chuck
• The clamp will ultimately dictate the size of the pins/connecting bars you apply
• Cancellous bone graft is recommended for large cortical defects in bone
B < 300 rpm recommended >700 rpm = increased pin and peri-pin bone temp
Which of the following is true?
A The more flexible the construct, the less callous that forms
B Destabilization at 6 weeks will increase callous but not increase bending strength
• Skin should be cut if it is observed to bind with the implant at the pin interface
• Craniolateral and caudomedial pin placement is recommended for R/u fractures
C is true
A (more rigid)
B no change in periosteal callus with INCREASE bending strengt
D (craniomedial and craniolateral oblique plane for greater purchase in radius (flattened bone)
What is the main advantage of hinged ESF?
Joint immobilization has deleterious effects on cartilage physiology and may lead to periarticular adhesions, contractures, and OA. Therefore they permit superior healing of damaged structures while avoiding deleterious effects of joint immobilization.
What are the 4 benefits of applying the scrub brush btw the skin and implant and on the edges of an ESF?
1) May retain some chlorhexadine which may help retard the bacterial growth, 2) compression to the soft tissues to limit swelling and edema, 3) protect the implant, 4)large absorptive capacity for blood and exudate, 5) Cheap.
True or false: circular external fixators do not need to be destabilized
- True- already have microaxial motion in weight bearing
* Dynamization when weight bearing
T/F: ESF frame stiffness can be increased and pin-bone interface stress decreased by increasing the number of transfixation pins incorporated into the frame by using up to six or eight pins per construct
(three to four pins per fragment).
T/F: A minimum insertion of two pins per fragment is always required to create at least two-point fixation of all fragments within the construct.
true?
T/F: Placing more than three pins per fragment does not significantly increase frame stiffness.
False: 4 pins
• More than 4 does not offset the increased morbidity with more pins
T/F: Placing smooth pins at a 70 degree angle to the long axis of the bone will enhance the pin-bone interface purchase and increase the stiffness of the external skeletal fixation construct
smooth pins at 70 is the old way to do it. Better to have positive threaded pins in parallel alignment (stiffness, greater axial pullout, greater fatigue life)
