(4)Locking Plates - Advantages & Indications 1-11

DJ 4213Locking PlatesAdvantages & Indications

1-11

DJ 4213ObjectivesDescribe locking plates and how they differ in design from other bone platesIdentify the advantages of locking plates over other platesBecome familiar with the indications for use of locking plates

DJ 4213Locking Plates are an evolution. . .. . . of plate fixation

DJ 4213Plate EvolutionDCPDynamic Compression Plate

LC-DCPLimited Contact Dynamic Compression Plate

LCPLocking Compression Plate

DJ 4213How 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 boneConventional Screw & PlateLocked Screw & Plate

DJ 4213Conventional vs Locking Plates

DJ 4213When do Locking Plates Work Best?When conventional screw purchase may be poor: Osteopenic bone Metaphyseal areas Periprosthetic fractures Failed fixation/nonunion Screw strippage

DJ 4213Plate Design Looks familiar:Same basic construct of plates and screwsAnatomically shapedSame stainless steel and titanium materials

DJ 4213Plate Design:Combination HoleFigure of eight hole design

Locking screws

Conventional cortex & cancellous screws

DJ 4213

Threaded underside of head To thread (lock) into plate hole

Larger core diameter:Increases strengthDissipates load over larger area of bone

Smaller thread pitch:Threads not used to generate screw thread purchase in bone

Locking Screw DesignCortex ScrewLocking Screw

DJ 4213Locking Screw DesignCore design:Solid and cannulatedCannulated screws are inserted over guide wires for precise placement

DJ 4213 Screw Head DesignsThreaded head:Locks screw to plate

Conical head:Can be used before, or instead of, locking screwsPartially threaded -- lags two fragments together Fully threaded -- pulls bone to plate

Spherical head cortex screw: Conventional use

DJ 4213Locking Plates and ScrewsHow do locking screws affect the surgical technique?

DJ 4213Conventional Plate Fixation

DJ 4213Conventional Plate Fixation

DJ 4213Locking Plates & Screws

DJ 4213Locking Plates & Screws

DJ 4213Variable Angle PlatesNew in locking plate technologyAllows screws to be angled around central axis of plate hole to match anatomyFirst seen in distal radius plates

DJ 4213Variable Angle PlatesNow part of new Forefoot-Midfoot SystemWill be seen in large & small fragment periarticular plates

DJ 4213Variable Angle PlatesVA holes require special drill guides & VA Locking ScrewsSpherical rather than straight headBe careful look similar

Variable Angle locking screwStandard locking screw

DJ 4213Locking Plates and ScrewsTechnique Requirements:Reduction essential firstLag before you lock

DJ 4213Original AO PrinciplesAnatomic reductionStable fixationPreservation of blood supplyEarly motion

Do the AO Principles still apply?

DJ 4213Locking 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

DJ 4213Locking Plates & Screws3) Preservation of Blood Supply:Limited contact stabilizes fracture without plate-to-bone compressionTapered tip allows submuscular (percutaneous) plate insertion, decreasing tissue destruction

DJ 4213Locking Plates & Screws4) Early Active Pain Free Mobilization: A more stable construct = earlier return to ADL (Activities of Daily Living)

DJ 4213SummaryNow 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 boneMetaphyseal fracturesPeriprosthetic fracturesFailed fixation (nonunion)Screw strippage

DJ 4213

*****5Again 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***4.5mm Cortex screw has a 3.2mm core diameter4.0mm Locking screw has a 3.4mm core diameter5.0mm Locking screw has a 4.4mm core diameter3.5mm Cortex screw has a 2.5mm core diameter3.5mm Locking screw has a 2.9mm core diameter

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