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internal fixation
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Principles of Internal Principles of Internal FixationFixation
Loretta Bubenik, DVM, MSLoretta Bubenik, DVM, MS
Diplomate ACVSDiplomate ACVS
March 6, 2002March 6, 2002
Principles of Internal Principles of Internal FixationFixation
• The Goals of fracture repair areThe Goals of fracture repair are
– Atraumatic techniqueAtraumatic technique– Good reductionGood reduction– Stable fixationStable fixation– Early return to full function****** Early return to full function******
Principles of Internal Principles of Internal FixationFixation
• Open reduction Open reduction – Surgically exposure of the fracture site Surgically exposure of the fracture site – Implants placed internallyImplants placed internally
• Closed reductionClosed reduction– Fracture site is not openedFracture site is not opened– External fixation (casts, splints, etc.) External fixation (casts, splints, etc.) – Becoming more popular with advanced imagingBecoming more popular with advanced imaging
Principles of Internal Principles of Internal FixationFixation
• Advantages of open reductionAdvantages of open reduction
– Provides rigid fixation with few complicationsProvides rigid fixation with few complications– Allows weight bearing during fracture Allows weight bearing during fracture
healinghealing•Health of the limb and joints Health of the limb and joints
• Increases the circulationIncreases the circulation
•Promotes healingPromotes healing
– Internally placed implants are hidden Internally placed implants are hidden •No extensive careNo extensive care
Principles of Internal Principles of Internal FixationFixation
• Disadvantages of open reductionDisadvantages of open reduction
– InvasiveInvasive– Potential for slow healing Potential for slow healing – InfectionInfection– Longer procedureLonger procedure– Higher cost Higher cost
Principles of Internal Principles of Internal FixationFixation
• Factures affecting fracture repairFactures affecting fracture repair
– Type of fracture (simple/comminuted)Type of fracture (simple/comminuted)– Anatomical area fracturedAnatomical area fractured
•ArticularArticular•Which limbWhich limb•Where on the boneWhere on the bone
– Extent of soft-tissue damageExtent of soft-tissue damage– Duration of the fractureDuration of the fracture
Principles of Internal Principles of Internal FixationFixation
• Factures affecting fracture repairFactures affecting fracture repair
– Animal’s age, weight and temperamentAnimal’s age, weight and temperament– Owner’s finances and ability to provide Owner’s finances and ability to provide
aftercareaftercare– Equipment available Equipment available – Surgeon’s experience. Surgeon’s experience.
Tension
Bending
Rotation
Compression
Fracture Forces
Orthopedic WireOrthopedic Wire
• FlexibleFlexible
• Made of stainless Made of stainless steelsteel
• Generally used in Generally used in conjunction with conjunction with other forms of other forms of fixationfixation
Full
Cerclage
Inter-
fragmentaryTension
band
Hemi-
cerclage
• Tension band Tension band – Opposes tensile forcesOpposes tensile forces
• muscle / ligament muscle / ligament
– converts tensile forces converts tensile forces to compressive forcesto compressive forces
• Principles of full cerclage wire Principles of full cerclage wire placementplacement
– Fracture must be long obliqueFracture must be long oblique– Bone must be reconstructedBone must be reconstructed– Use the appropriate sizeUse the appropriate size– Never use a single cerclage wireNever use a single cerclage wire– Place wires ~ 1 cm apartPlace wires ~ 1 cm apart– Place wires ~ 0.5 cm from fracturePlace wires ~ 0.5 cm from fracture
WiresWires
• Principles of full cerclage wire Principles of full cerclage wire placementplacement
– Do not entrap soft tissuesDo not entrap soft tissues– Place perpendicular to bonePlace perpendicular to bone– Lock wire in place where it changes Lock wire in place where it changes
diameter (K-wire or notch)diameter (K-wire or notch)– Wires must be tightWires must be tight– Do not bend ends overDo not bend ends over
WiresWires
WiresWires
• Securing full cerclageSecuring full cerclage
– Twisted wiresTwisted wires•Wire holders/pliersWire holders/pliers
•Wire tightenersWire tighteners
– Single and double loop wiresSingle and double loop wires•Special tensioning device requiredSpecial tensioning device required
Good
Bad
• Other factsOther facts
– Bending the twistBending the twist– Cutting the twistCutting the twist– Twist vs loopsTwist vs loops– Shift in bone Shift in bone
diameterdiameter– Blood supplyBlood supply
WiresWires
Intramedullary (IM) PinsIntramedullary (IM) Pins
• Very resistant to bending forcesVery resistant to bending forces
• Require little equipment to placeRequire little equipment to place
• Easy to removeEasy to remove
• Do little damage to blood supply if Do little damage to blood supply if properly usedproperly used
• InexpensiveInexpensive
• Closed or open techniquesClosed or open techniques
• IM pins do not counteract IM pins do not counteract rotational forcesrotational forces– Use additional fixationUse additional fixation
• External fixator External fixator
• PlatePlate
• Cerclage wiresCerclage wires
– Provide endosteal contactProvide endosteal contact• Fill 70% of the bone diameterFill 70% of the bone diameter
• ““Stacked” pinsStacked” pins– Do not provide appreciable Do not provide appreciable
stabilitystability
• IM pins alone are IM pins alone are poorly suited for poorly suited for comminuted comminuted fracturesfractures
• They can’t withstand They can’t withstand axial forcesaxial forces
• Collapse and Collapse and instability will resultinstability will result
• Steinmann pins are Steinmann pins are most commonly most commonly usedused
• They pins vary in They pins vary in diameterdiameter– Proportional to Proportional to
strengthstrength
• Vary in point Vary in point morphologymorphology– ChiselChisel– TrocarTrocar– ThreadedThreaded
• IM pin insertionIM pin insertion
– Jacob’s chuckJacob’s chuck– Low speed drillLow speed drill– RetrogradeRetrograde– NormogradeNormograde
• Retrograde Insertion:Retrograde Insertion:– Pin inserted from Pin inserted from
fracture site and fracture site and driven through driven through epiphysisepiphysis
• Normograde Normograde insertioninsertion– Pin inserted at Pin inserted at
epiphysis and driven epiphysis and driven across fracture lineacross fracture line
FemurFemurRetro or
Normograde
Extend hip
Intertrochanteric fossa
Direct laterally
Over reduce
TibiaTibia
Intra-articular
Always Normograde
Countersink or cut short
HumerusHumerus
Retro or NormogradeRetro or Normograde
Exit or start distal to Exit or start distal to greater tubercle on greater tubercle on the lateral aspectthe lateral aspect
Direct into medial Direct into medial aspect of condyleaspect of condyle
RadiusRadius
Avoid IM pins in the Avoid IM pins in the radiusradius
Must go through a Must go through a jointjoint
Radius is ovalRadius is oval
Kirschner WiresKirschner Wires
• Small and elasticSmall and elastic
• Usually used as:Usually used as:– Transcortical pins Transcortical pins
(“skewer wires”)(“skewer wires”)– Pin and tension Pin and tension
band fixationband fixation– Cross pinningCross pinning
• Dynamic pinningDynamic pinning
Interlocking NailsInterlocking Nails
• Specialized IM pinSpecialized IM pin
• Locked in place with bone screwsLocked in place with bone screws
• Counteracts all fracture forcesCounteracts all fracture forces
• Can be used for fractures of the Can be used for fractures of the femur, tibia, and humerusfemur, tibia, and humerus
• Can be placed open or closedCan be placed open or closed
• Limited approachLimited approach
Interlocking NailsInterlocking Nails
• 4, 4.7, 6, and 8 mm4, 4.7, 6, and 8 mm
• Various lengthsVarious lengths
• Screw holesScrew holes
– 2 proximal, 2 distal2 proximal, 2 distal– 1 proximal, 2 distal1 proximal, 2 distal– 2 proximal, 1 distal2 proximal, 1 distal– 1 proximal, 1 distal1 proximal, 1 distal
Interlocking NailsInterlocking Nails
• A few specificsA few specifics– Chose the biggest nail possibleChose the biggest nail possible– Don’t place an empty hole at the Don’t place an empty hole at the
fracture sitefracture site– Place screws 2 cm away from fracturePlace screws 2 cm away from fracture– Try to use four screws totalTry to use four screws total– Use smaller screws for 6 and 8 mm nailsUse smaller screws for 6 and 8 mm nails– Can dynamize the fractureCan dynamize the fracture
ScrewsScrews• Cortical ScrewsCortical Screws
– More threads, low pitch, More threads, low pitch, thin threadthin thread
– Only Fully threadedOnly Fully threaded– Used for cortical boneUsed for cortical bone
• Cancellous ScrewsCancellous Screws– Less threads, steep Less threads, steep
pitch, wide threadpitch, wide thread– Fully and partially Fully and partially
threadedthreaded– Used in soft boneUsed in soft bone
ScrewsScrews
• Used to secure bone plates to boneUsed to secure bone plates to bone
• Used as primary means of fracture Used as primary means of fracture repair repair
• Used to hold fracture fragments in Used to hold fracture fragments in place place
• Used to compress fracture fragmentsUsed to compress fracture fragments
• Used to form prosthetic ligamentsUsed to form prosthetic ligaments
ScrewsScrews
• Positional screwsPositional screws
– Hold bone fragments in placeHold bone fragments in place– Do not provide compression Do not provide compression – Threads engage both near and far Threads engage both near and far
cortexcortex– Must be placed perpendicular to boneMust be placed perpendicular to bone
• if positioning small fragments if positioning small fragments
ScrewsScrews
• Lag principleLag principle
– Used to compress fracture fragmentsUsed to compress fracture fragments– Used to hold plates on bone Used to hold plates on bone – Threads only engage far cortexThreads only engage far cortex– Must be placed perpendicular to the boneMust be placed perpendicular to the bone– Can be accomplished with Can be accomplished with
•partially threaded screw partially threaded screw
• over drilling near cortexover drilling near cortex
ScrewsScrews
ScrewsScrews
• Lag principleLag principle
– Used for interfragmentary compression Used for interfragmentary compression – Used for primary fracture repairUsed for primary fracture repair
•Articular fracturesArticular fractures
•Sacroiliac luxationsSacroiliac luxations
ScrewsScrews
Do not over tighten the screw, this will cause stripping
and screw loosening
Bone PlatesBone Plates
• Necessary for many fracturesNecessary for many fractures
• Requires specialized equipment and Requires specialized equipment and trainingtraining
• Not readily available in many Not readily available in many practicespractices
• More expensive than pinningMore expensive than pinning
Bone PlatesBone Plates
• CounteractCounteract
– TensionTension– CompressionCompression– ShearShear– Bending Bending – Rotational forcesRotational forces
Bone plates should be placed on the Bone plates should be placed on the
tension side of the bonetension side of the bone
Tension side of the boneTension side of the bone
• FemurFemur– CraniolateralCraniolateral
• Tibia*Tibia*– CraniolateralCraniolateral
• HumerusHumerus– CraniolateralCraniolateral
• RadiusRadius– CranialCranial
• Unla*Unla*– CaudalCaudal
• Mandible*Mandible*– dorsaldorsal
Some are not plated on the tension side due to impracticality and added difficulty
Plates are stronger if load sharing Plates are stronger if load sharing
with the bone occurs with the bone occurs
Plates come in a wide variety of shapes and
sizes
PlatesPlates
• FunctionsFunctions
– NeutralizationNeutralization– CompressionCompression– ButtressButtress
NeutralizationNeutralization
• Plate protects primary Plate protects primary repair from weight-repair from weight-bearing forcesbearing forces
• The weight-bearing The weight-bearing load is shared by both load is shared by both the plate and the bonethe plate and the bone
CompressionCompression
• Mechanical compression Mechanical compression added to the fracture added to the fracture sitesite
• The weight-bearing load The weight-bearing load is shared by both the is shared by both the plate and the boneplate and the bone
• Primary bone healing Primary bone healing resultsresults
ButtressButtress
• Spans a gap to prevent Spans a gap to prevent collapse of a fracturecollapse of a fracture
• AllAll of the weight-of the weight-bearing forces are bearing forces are transmitted through transmitted through the platethe plate
PlatesPlates
• Plate placementPlate placement
– Reconstruct the boneReconstruct the bone– Contour plate Contour plate – Drill, measure, and tap screws (one by Drill, measure, and tap screws (one by
one)one)– Apply screws from the fracture site out, Apply screws from the fracture site out,
alternating bone fragmentsalternating bone fragments– Engage at least six cortices per a major Engage at least six cortices per a major
bone fragmentbone fragment•More for comminuted fractures if possibleMore for comminuted fractures if possible
PlatesPlates
• Dynamic compression platesDynamic compression plates
– Allows compression of major bone Allows compression of major bone fragmentsfragments•External compressionExternal compression
– Screws must be LOADED in order to get Screws must be LOADED in order to get compressioncompression
– Plate can function in compression, Plate can function in compression, neutralization, and as a buttress plate neutralization, and as a buttress plate depending on how the screws are applieddepending on how the screws are applied
1)1) Load Drill Guide:Load Drill Guide: Provides 1 mm Provides 1 mm compression, screws are placed eccentricallycompression, screws are placed eccentrically
2) 2) Neutral Drill GuideNeutral Drill Guide:: Places the drill hole Places the drill hole centrally, thus little displacement is provided.centrally, thus little displacement is provided.
LoadingLoading a screw in the DCP for compression a screw in the DCP for compression
Applying compression to a fractureApplying compression to a fracture
Plates-Rod constructsPlates-Rod constructs
• Used for comminuted fracture repairUsed for comminuted fracture repair
• Decreases bending stress on plateDecreases bending stress on plate
• Counteracts rotational and axial Counteracts rotational and axial forcesforces
• IM pin only needs to fill 30-40% of IM pin only needs to fill 30-40% of the canal diameterthe canal diameter
• Monocortical screws are o.k.Monocortical screws are o.k.– Make sure you engage enough corticesMake sure you engage enough cortices
Removing ImplantsRemoving Implants
• In general, it is recommended that In general, it is recommended that all orthopedic implants be removed all orthopedic implants be removed
• In practice, however, we rarely In practice, however, we rarely remove orthopedic implantsremove orthopedic implants
Removing ImplantsRemoving Implants
• Why don’t we remove themWhy don’t we remove them
– CostCost– Post-op confinement requiredPost-op confinement required– Traumatic surgeryTraumatic surgery– Anesthesia riskAnesthesia risk– Potential for refracturePotential for refracture
Removing ImplantsRemoving Implants
• When to recommend removalWhen to recommend removal
– Interferes with function Interferes with function – Loosening or Breakage Loosening or Breakage – InfectionInfection– Thermal conductionThermal conduction– Biological reaction to implantsBiological reaction to implants– Young dogs?????Young dogs?????
Removing ImplantsRemoving Implants
• Radiographs should document Radiographs should document healing prior to removalhealing prior to removal– Unless implant failureUnless implant failure
• Warn owners about potential for Warn owners about potential for bone breakagebone breakage– Cage rest required after plate removalCage rest required after plate removal
• Good idea to culture implantsGood idea to culture implants
Removing ImplantsRemoving Implants
• IM pins are easier to remove than platesIM pins are easier to remove than plates– Must leave pins long enoughMust leave pins long enough– Not the same refracture worryNot the same refracture worry
• Young dogs tend to over-grow the implants Young dogs tend to over-grow the implants and they are hard to removeand they are hard to remove
• Plates on the pelvis and humerus should be Plates on the pelvis and humerus should be left in place if not causing a problemleft in place if not causing a problem
Advantages of one over anotherAdvantages of one over another
• IM pins are cheaper than plates and IM pins are cheaper than plates and interfere with blood supply lessinterfere with blood supply less
• Little equipment is required for pin Little equipment is required for pin placementplacement
• IM pins can migrate, especially if IM pins can migrate, especially if motion is presentmotion is present
Advantages of one over anotherAdvantages of one over another
• IM pins must be combined with IM pins must be combined with another form of fixationanother form of fixation– Cross pins can be used as a primary Cross pins can be used as a primary
fracture repair in some instances fracture repair in some instances
• IM pins are not ideal for comminuted IM pins are not ideal for comminuted or transverse fractures (limits to or transverse fractures (limits to amendable fractures)amendable fractures)
Advantages of one over anotherAdvantages of one over another
• Interlocking nails counteract all fracture forces Interlocking nails counteract all fracture forces and may do it better than platesand may do it better than plates
• Interlocking nails do require a lot of equipment Interlocking nails do require a lot of equipment and some expertise to place them, but are and some expertise to place them, but are cheaper than platescheaper than plates
• Interlocking nails are limited by the type of Interlocking nails are limited by the type of fracture you can repair and the size of the fracture you can repair and the size of the animalanimal
Advantages of one over anotherAdvantages of one over another
• Plates counteract all fracture forcesPlates counteract all fracture forces
• Plates are versatile and can be Plates are versatile and can be applied to many fracture types and applied to many fracture types and animal sizesanimal sizes
• Plating requires some expertise and Plating requires some expertise and expensive equipmentexpensive equipment
Advantages of one over anotherAdvantages of one over another
• Plating requires an aggressive Plating requires an aggressive surgical approach in most instancessurgical approach in most instances
• Plates may interfere with blood Plates may interfere with blood supply more than any of the other supply more than any of the other implantsimplants– Clinically not a major problemClinically not a major problem
Advantages of one over anotherAdvantages of one over another
• Open approaches may delay fracture Open approaches may delay fracture healing and predispose to infectionhealing and predispose to infection– Plates/screwsPlates/screws– Interlocking nails Interlocking nails
• Closed approaches can be used withClosed approaches can be used with– IM pinsIM pins
•External fixatorExternal fixator
– Interlocking nails require a limited approachInterlocking nails require a limited approach
Advantages of one over anotherAdvantages of one over another
• Hidden implants allow early function Hidden implants allow early function with out hassle of extra carewith out hassle of extra care– Casts and ex-fixators have added careCasts and ex-fixators have added care
• Articular fractures generally require Articular fractures generally require open approaches and stable fixationopen approaches and stable fixation– Plates are more idealPlates are more ideal– Lag screws are used in many instancesLag screws are used in many instances