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Locking PlatesAdvantages & Indications

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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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Locking Plates are an evolution. . .

. . . of plate fixation

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Plate Evolution

• DCP– Dynamic Compression Plate

• LC-DCP– Limited Contact

Dynamic Compression Plate

• LCP– Locking Compression Plate

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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 Conventional

Screw & PlateScrew & Plate

Locked Locked

Screw & PlateScrew & Plate

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Conventional vs Locking Plates

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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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Plate Design

Looks familiar:– Same basic construct of

plates and screws– Anatomically shaped– Same stainless steel and

titanium materials

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Plate Design:Combination Hole

• “Figure of eight” hole design

• Locking screws

• Conventional cortex & cancellous screws

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• Threaded underside of head – 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

Locking Screw Design

Cortex ScrewLocking Screw

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Locking Screw Design

• Core design:– Solid and cannulated– Cannulated screws are inserted over guide wires

for precise placement

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Screw Head Designs

• Threaded 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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Locking Plates and Screws

• How do locking screws affect the surgical technique?

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Conventional Plate Fixation

Pre Reduced Fracture Loss of Reduction

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Conventional Plate Fixation

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Locking Plates & Screws

Non Reduced FractureNo Bone Alignment to the Plate

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Locking Plates & Screws

Pre Reduced FractureNo Fracture Malalignment

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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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Variable Angle Plates• Now part of new Forefoot-Midfoot System• Will be seen in large & small fragment

periarticular plates

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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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Locking Plates and Screws

• Technique Requirements:– Reduction essential first– Lag before you lock

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Original AO Principles

• Anatomic reduction

• Stable fixation

• Preservation of blood supply

• Early motion

Do the AO Principles still apply?

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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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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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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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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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