1. Locking Plates Advantages & Indications
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2. Objectives
Describe locking plates and how they differ in design from other bone plates
Identify the advantages of locking plates over other plates
Become familiar with the indications for use of locking plates
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3. Locking Plates are an evolution. . .
. . . of plate fixation
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4. Plate Evolution DCP LC-DCP LCP Dynamic Compression Plate
Limited Contact Dynamic Compression Plate
LCP
Locking Compression Plate
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5. How is a Locking Plate Different?
Conventional plates & screws depend on friction between the screw thread & bone for stability
Locking plates & screws create fixed angles that do not rely on screw purchase in bone
Conventional
Screw & Plate
Locked
Screw & Plate
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6. Conventional vs Locking Plates
Again we see the initial stress in the bone due to tightening. When the bone is loaded along its axis, the bone around the screw is compressed on the load side of the fracture.
As the load is increased, and the angle between the screw and the plate starts to change, the resultant loading vector on the screw changes from pure compression to a compressive and a tensile component. It is this additional tensile component which, when the elastic limit of the bone is exceeded, will cause toggling and eventual collapse across the fracture gap.
The lock plate does not exhibit this behavior as the angles of the screws are fixed and there is no pre-load
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7. When do Locking Plates Work Best?
When conventional screw purchase may be poor:
Osteopenic bone
Metaphyseal areas
Periprosthetic fractures
Failed fixation/nonunion
Screw strippage
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8. Plate Design Looks familiar: Same basic construct of plates and screws
Anatomically shaped
Same stainless steel and titanium materials
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9. Plate Design: Combination Hole
“Figure of eight” hole design
Locking screws
Conventional cortex & cancellous screws
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10. Locking Screw Design Threaded underside of head Larger core diameter:
To thread (lock) into plate hole
Larger core diameter:
Increases strength
Dissipates load over larger area of bone
Smaller thread pitch:
Threads not used to generate screw thread purchase in bone
4.5mm Cortex screw has a 3.2mm core diameter
4.0mm Locking screw has a 3.4mm core diameter
5.0mm Locking screw has a 4.4mm core diameter
3.5mm Cortex screw has a 2.5mm core diameter
3.5mm Locking screw has a 2.9mm core diameter
Locking Screw
Cortex Screw
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11. Locking Screw Design Core design: Solid and cannulated
Cannulated screws are inserted over guide wires for precise placement
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12. Screw Head Designs Threaded head: Conical head:
Locks screw to plate
Conical head:
Can be used before, or instead of, locking screws
Partially threaded -- lags two fragments together
Fully threaded -- pulls bone to plate
Spherical head cortex screw:
Conventional use
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13. Locking Plates and Screws
How do locking screws affect the surgical technique?
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14. Conventional Plate Fixation
Loss of Reduction
Pre Reduced Fracture
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15. Conventional Plate Fixation
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16. Locking Plates & Screws
No Bone Alignment to the Plate
Non Reduced Fracture
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17. Locking Plates & Screws
No Fracture Malalignment
Pre Reduced Fracture
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18. Variable Angle Plates New in locking plate technology
Allows screws to be angled around central axis of plate hole to match anatomy
First seen in distal radius plates
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19. Variable Angle Plates Now part of new Forefoot-Midfoot System
Will be seen in large & small fragment periarticular plates
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20. Variable Angle Plates
VA holes require special drill guides & VA Locking Screws
Spherical rather than straight head
Be careful – look similar
Variable Angle locking screw
Standard locking screw
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21. Locking Plates and Screws
Technique Requirements:
Reduction essential first
Lag before you lock
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22. Original AO Principles
Anatomic reduction
Stable fixation
Preservation of blood supply
Early motion
Do the AO Principles still apply?
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23. Locking Plates & Screws
AO Principles
1) Anatomic Reduction:
Locked plate design allows lag screw and
compression plating techniques
2) Stable Internal Fixation:
Locking screws increase stability in osteoporotic
and metaphyseal bone
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24. Locking Plates & Screws
3) Preservation of Blood Supply:
Limited contact stabilizes fracture without plate-to-bone compression
Tapered tip allows submuscular (percutaneous) plate insertion, decreasing tissue destruction
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25. Locking Plates & Screws
4) Early Active Pain Free Mobilization:
A more stable construct = earlier return to ADL (Activities of Daily Living)
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26. Summary Now you should be able to:
Describe how locking plates are designed and function differently than conventional plates
Identify the advantages of locking plates for certain fractures
Know the indications for using locking plates:
Poor quality bone
Metaphyseal fractures
Periprosthetic fractures
Failed fixation (nonunion)
Screw strippage
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