Principles of internal fixation: plates and screws (Johnson) Flashcards

1
Q

Principles of internal fixation

A

anatomic reduction

Stabilize

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2
Q

Cortical screw

A

Core diameter larger than outer diameter

Lower thread pitch

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3
Q

Advantages of cortical screw

A

Thick core, size matters

less breakage

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4
Q

Disadvantage of cortical

A

Pulls out too quick

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5
Q

When would you use cortical screws

A

Diaphyseal

most common

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6
Q

When would you use cancellous screws

A

Metaphyseal

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7
Q

Advantage of locking screw over cortical

A

Threaded head is ribbed for pleasure, resists bending

Thicker core diameter

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8
Q

Implant screws

A

Used with plates

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9
Q

Traditional implant screw

A

compress plate to bone surface

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10
Q

Locking implant screw

A

the head threads into the plate

Does not compress the plate to the bone

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11
Q

Position screw

A

Aid in initial reduction
Hold fragment in reduction
No compression
Comminuted fractures

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12
Q

Design of lag screw

A

Partially threaded screw

Threads engage far, cortex creates compression

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13
Q

Dynamic compression plate

A

Compression across fracture

Full contact between plate and periosteum

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14
Q

Limited contact dynamic compression plate (LC-DCP)

A

Reduces contact w/ bone
increases blood supply
Reduces stress riser at screw holes

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15
Q

Locking compression plate

A

Screws in shear
No compression
No screw loosening

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16
Q

Neutralization plate

A

Protects interfragmentary stabilization via lag screw/cerclage/hemicerclage from bending, shear and torsional loading

17
Q

Bridging plate

A

Splint to maintain limb length and joint alignment

prevent bending or shear

18
Q

For traditional plate repair, minimum number of cortices on each side of fracture

A

6

19
Q

Screw size compared to bone diameter

A

30%