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12 Cards in this Set
- Front
- Back
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Inner (root) diameter determines what property?
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Tensile strength
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Outer diameter determines what property?
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Pullout strength
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What three screw dimensions maximize pullout strength?
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Small inner diameter
Large outer diameter Fine pitch |
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What is the most important factor determining pedicle screw pullout strength?
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Bone density
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A screw hole reduces the strength of bone by how much?
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50%
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When does the strength return to baseline?
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9 to 12 months after the screw has been removed
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ls an oval hole or a rectangular hole biomechanically superior?
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Oval hole
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What mechanical advantage does a closed nail have over a slotted nail?
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Closed nails have greater torsional stiffness
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What then is the advantage of a slotted nail?
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Decreased hoop stress on insertion
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What are the top two factors determining the stability of an external fixation construct?
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Contact between the two ends of bone
Pin diameter |
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What is the most stable circular external fixation construct that can be achieved with two implants?
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1 olive wire and 1 half-pin at 90 degrees to each other
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How does construct stability vary with ring diameter?
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Stability increases with decreasing ring diameter
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