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31. Fracture Fixation Principles

Topic

Basic Science

Podcast

Updated

SCREW

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What is a screw?

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What are the components of a screw?

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What is the relationship between pitch and lead?

Types of screws - differentiate cortical, cancellous, half threaded, locking screws

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Difference between cortical and cancellous screws?

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What is the usual failure mechanism between cortical and cancellous screws?

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Why does fatigue failure occur at the neck shaft junction?

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Difference between self tapping and self drilling screws?

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Are self drilling screws meant to be uni or bicortical?

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What are different uses of screws?

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What is counter sink?

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How to increase pull out strength of screw?

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What are the lag screw principles?

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What size drills for lag screws?

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Why do you use a washer? How do you use it?

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What are reverse cutting screws?

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What is the working length of the screw?

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How do interference screws work?

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What are bioabsorbable screws? Pros and cons?

PLATES

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Types of Plate configuration?

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How to improve fixation in osteoporosis? How does it change?

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How does compression plating work?

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How much compression is achieved when you use the compression plate?

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How do you sequentially compress the plate?

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How do you put on a compression plate? [Draw]

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How does locking plates differ from compression plates?

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Why do you need to prebend the plate?

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What is the working length of plates?

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Ideal plate density?

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Why is ideal plate length 8-10x for a comminuted fracture?

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What kind of plate should you use for Humeral shaft, explain it with its structural property?

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How does a tension band construct work?

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Problems with a short working length in a bridge plating?

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Can you describe the near-near- far-far principle?

Dynamic Hip Screw

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Explain screw cut out in DHS?

RIGIDITY

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Relative Young's Modulus of materials and tissues vs bone?

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What are the type of deforming forces?

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In an IM nail, what determines the rigidity?

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What determines the bending rigidity?

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What determines the torsional rigidity?

NAILS

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What is the working length of a nail?

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What does it mean that the nail is load sharing or load bearing?

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What is the effect of reaming and blood supply? How long does it take to revascularize?

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What are the benefits of reaming?

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Concerns of reaming and how do you circumvent?

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Why hollow vs Solid rods?

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Why hollow vs Solid rods? [Simple Answer]

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Why hollow vs Solid rods assuming same amount of material (Wang Ming

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Why closed section nails vs open section (i.e. Slotted) nails?

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Circular vs cloverleaf shaped nail (Kuntscher nail)?

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How can you describe nails?

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How do you reduce hoop stresses when inserting the IM nail? [Why are nails curved?]

LOCKING BOLTS

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How are locking bolts different from other screws?

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What are the advantages of locking bolts?

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What are potential disadvantages of locking bolts/ their holes?

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What may occur if you place too many bolts in multiple planes?

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How to reduce risk of locking screw fatigue?

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Why don't simply use the largest possible locking screw?

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What are the forces on the locking bolt?

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Why do we need a large core diameter in the locking bolt vs nail?

K-WIRES

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What are the various designs of K-wires tips?

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How to reduce temperature and heat necrosis?

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What is the olive tip used for?

EXTERNAL FIXATION

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What kind of Ex fix do you make?

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What increases stability of the Ex fix?

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Principles of circular frame? What is an ideal "ring block"

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Wire principles for circular frame?

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How to increase stability for circular ex fix?