Presentation on theme: "Principles of External Fixation"— Presentation transcript:
1 Principles of External Fixation Roman Hayda, MDOriginal Authors: Alvin Ong, MD & Roman Hayda, MD; March 2004;New Author: Roman Hayda, MD; Revised November, 2008
2 Overview Indications Advantages and disadvantages Mechanics Biology ComplicationsIn this lecture, we will go over indications for the use of the external fixator, advantages and disadvantages of its use, the mechanics of the fixator, the biology involved which includes modes of fixation, type of healing and anatomic considerations during external fixator application. We will end this talk by considering some of the historic and real complications associated with the use of the exfix device.
3 Indications Definitive fx care: Malunion/nonunion Open fractures Peri-articular fracturesPediatric fracturesTemporary fx care“Damage control”Long bone fracture temporizationPelvic ring injuryPeriarticular fracturesPilon fractureMalunion/nonunionArthrodesisOsteomyelitisLimb deformity/length inequalityCongenitalAcquiredIndications of External Fixation include:Open fractures, closed fractures with severe soft tissue injury, pediatric fractures, multi-trauma, pelvic ring injury, complex intra- and peri-articular fractures, arthrodesis(especially in the infected cases), and osteomyelitis.
4 Advantages Minimally invasive Flexibility (build to fit) Quick applicationUseful both as a temporizing or definitive stabilization deviceReconstructive and salvage applicationsComplex 3-C humerus fxExternal Fixators have many advantages over other forms of surgical stabilization. It is applied with minimal additional soft tissue injury. It is inherently flexible. Thus, have a potential for wide applicability. It is also often useful in emergency situations when quick application is essential. It may be used as a temporizing device such as in the case of severely contaminated open injuries, but can also be utilized as the definitive stabilizing hardware. Often, it can also be used in reconstructive as well as salvage applications.
5 Disadvantages May result in malunion/nonunion, loss of function MechanicalDistraction of fracture siteInadequate immobilizationPin-bone interface failureWeight/bulkRefracture (pediatric femur)BiologicInfection (pin track)May preclude conversion to IM nailing or internal fixationNeurovascular injuryTethering of muscleSoft tissue contractureMay result inmalunion/nonunion,loss of functionThere are also disadvantages inherent in External fixators that should be noted.Because external fixators rely on pins or wires that are left partly outside the body, there is an increased risk of infection. Most of these are superficial in nature and can be easily treated with pin site care and oral antibiotics. However, there are occasions when a deep infection can develop that leads to abscess formation and osteomyelitis. These require surgical debridement and intravenous antibiotics.Historically, distraction at the fracture site has been a problem. With the improvement of external fixator design, distraction has become less of a problem. Currently, this is more a surgeon-dependent problem than a device-dependent problem.In general, external fixators provide less stability to the fractured limb than internal stabilization.Soft tissue contractures can occur with the use of external fixation. Pins can impale muscles and tendons, preventing motion of a joint. Spanning frames that cross a joint also prevent motion for the duration of fracture care and can lead to soft tissue contractures. This can be avoided by careful pin placement and limiting the duration of use of joint spanning frames.Stress is concentrated at the pin-bone interface in early Pin designs. Failure of the pin may be seen at these sites leading to inadequate immobilization, pin loosening and malunions or non-unions.
6 Components of the Ex-fix PinsClampsConnecting rodsThe “anatomy” of the external fixator includes: pins, clamps and connecting rods. Ring fixators (Ilizarov-type frames) are composed of wires and rings. Finally, hybrid frames are composed of a combination of these components.
7 PinsPrinciple: The pin is the critical link between the bone and the framePin diameterBending stiffnessproportional to r45mm pin 144% stifferthan 4mm pinPin insertion technique respecting bone and soft tissue< 1/3 diaFactors that influence pin strength and rigidity include:MaterialPin diameterPin designMost pins in currently available are made of stainless steel or titanium.Keep in mind that even though Pin strength increases with increasing pin diameter, pin holes greater that 30% of the diaphysis can markedly weaken the bone. Use appropriately sized pins and avoid weakening the bone. In most adults 5 mm pins are adequate for the femur, tibia, and humerus. 4 mm pins are used in the forearm and foot and 3mm pins in the hand.Pin diameter is a very important component of overall pin strength and stiffness.Stiffness of a pin is proportional to the fourth power of its radius (small increases in diameter = large increase in stiffness)Too small => lead to micromotion and ultimate pin failureToo large=> stress riser formed in the bone can lead to fracture.Pin strength and fatigue resistance are directly proportional to core diameter, which is generally highest in the unthreaded shank portion of the pin. Highest stress seen at pin-bone interface.Designs that help move the thread-shank junction away from the pin-bone interface include:1) tapered pins2) shorter threads to engage only the far cortex3) pins with longer threaded portions
8 Pins Various diameters, lengths, and designs Materials 2.5 mm pin 4 mm short thread pin5 mm predrilled pin6 mm tapered or conical pin5 mm self-drilling and self tapping pin5 mm centrally threaded pinMaterialsStainless steelTitaniumMore biocompatibleLess stiffPins come in a variety of diameters, lengths, designs, and materials. All are important in their application and eventual effectiveness in the treatment of fractures. Common diameters range from 3 to 5 mm.Purchase in the bone is dependent on thread section design. There is a variety of root versus thread diameter ratios. Thread section design also vary with constant diameter versus conical (gradual taper) design. Constant diameter threads are designed to purchase both the near and far cortex. Conical taper threads also obtain purchase on the near and far cortex while allowing for radial preload. This preload is thought to decrease the rate of pin loosening. Insertion technique is also influenced by pin design. Self-drilling and -tapping pins have built in flutes to allow egress of bony debris during insertion, thus minimizing heat generation. Standard pins have blunt tips, requiring initial drill bit use.Overall pin style can also differ. Transfixion pins are placed across the width of the bone with pin shaft available on each side of the bone for connecting rod stabilization. On the other hand, half pin are designed extend only to the far cortex. This allows for connection to rods on only one side of the bony shaft.Stress is highest at Pin-Bone interface. The thread-shank junction of the pin forms a stress riser. When this junction occurs at the same level as the pin-bone interface, fatigue and fracture can result with loading.A. Longer threads to move the stress riser to the near-cortical side of the pin-bone interfaceB. Tapered thread design to limit the magnitude of the stress riser at any single pointC. Shorter thread design to move the stress riser to the far-cortical side
9 Self Drilling and Tapping Pin Geometry‘Blunt’ pins- Straight- ConicalPin geometry can obviously affect the fixation of the pin in bone. We know historically that placing steinmann pins (smooth pins) into bone generated lots of heat, resuling in thermal necrosis and early pin loosening. Without threads, they are also more likely to slip, loosen and fail. These require predrilling the core diameter.These self drilling and tapping pins are great for us in the military - the Apex pins from one company can be placed with or without power and therefore are very advantageous for use in the field environment. This is a major advantage. It is quick and easy - easy for us to forget about insertion technique…There is a difference as to how these are inserted: While these blunt pins are designed to be inserted bicortically, the other (at least according to the manufacturer) just engages the second cortex.Self Drilling and Tapping
10 Pin coatingsRecent development of various coatings (Chlorohexidine, Silver, Hydroxyapatite)Improve fixation to boneDecrease infectionMoroni, JOT, ’02Animal study, HA pin 13X higher extraction torque vs stainless and titanium and equal to insertion torqueMoroni, JBJS A, ’050/50 pts pin infection in tx of pertrochanteric fxMoroni A, et al, Dynamic Hip Screw versus External Fixation for Treatment of Ostoporotic Pertrochanteric Fractures, J Bone Joint Surg Am. 87: , 2005.
11 Pin Insertion Technique Incise skinSpread soft tissues to boneUse sharp drill with sleeveIrrigate while drillingPlace appropriate pin using sleeveBlunt Schantz pinsGenerous Skin incisionsblunt dissection to boneSoft tissue protectionSharp Drill bitsIrrigationminimize thermal necrosisInsertion with T-handle chuckBicortical fixationAvoid soft tissue damage and bone thermal necrosis
12 Pin insertion Self drilling pin considerations vs. Short drill flutes thermal necrosisstripping of near cortex with far cortex contactQuick insertionUseful for short term applicationsvs.When inserting a self drilling self tapping pin, especially if under power, understand that heat is generated and thermal necrosis occurs when the flutes of the drill fill up; also, unless the bone is metaphyseal and/or osteoporotic, as the pin engages the second cortex, it will strip the near side and lose fixation
13 Courtesy Matthew Camuso Pin LengthHalf Pinssingle point of entryEngage two corticesTransfixation PinsBilateral, uniplanar fixationlower stresses at pin bone interfaceLimited anatomic sites (nv injury)Traveling tractionHalf pins are just that - they engage two cortices, but only exit the skin on one side of the bone. Transfixion pins, in my hands are used primarily when I’d like to create a travelling traction type frame, in which I’m applying a pure distractive force. These pins can also be used to create bilateral frames and added stability. When these are placed, always remember to start on the dangerous side and insert towrard the safe side, because you never know exactly where these pins are going to come out…Courtesy Matthew Camuso
14 Pin Diameter Guidelines Femur – 5 or 6 mmTibia – 5 or 6 mmHumerus – 5 mmForearm – 4 mmHand, Foot – 3 mmRemember your pin insertion technique!Remember that you can make one of these mega holes when you are not paying attention to your insertion and toggling is occurring!< 1/3 diaSlide courtesy Matthew Camuso
15 Clamps Principles Two general varieties: Features: Single pin to bar clampsMultiple pin to bar clampsFeatures:Multi-planar adjustabilityOpen vs closed endPrinciplesMust securely hold the frame to the pinClamps placed closer to bone increases the stiffness of the entire fixator constructClamps come in 2 general varieties:The single pin to bar clamps, as shown on the leftThe multi-pin to frame clamp, shown on the middle and rightClamps act to connect the pins to the rod. They are designed for multi-planar adjustability.Clamps placed close to the bone (thus, bringing the connecting rod and the rest of the frame close to bone) increases the rigidity of the entire frame
16 Connecting Rods and/or Frames Options:materials:SteelAluminumCarbon fiberDesignSimple rodArticulatedTelescopingPrincipleincreased diameter = increased stiffness and strengthStacked (2 parallel bars) = increased stiffnessConnecting rods are made from a variety of materials:Steel, titanium, plastics, carbon fiberMetals are stronger but radio-opaque and heavy. Non-metals are radio-lucent and lighter.As a general rule of thumb, the larger the diameter of the connecting rod, the more rigid the fixator.
17 increased frame stiffness BarsStainless vs Carbon FiberRadiolucency↑ diameter = ↑ stiffnessCarbon 15% stiffer vs stainless steel in loading to failureframes with carbon fiber are only 85% as stiff ? ? ? ?Weak link is clamp to carbon bar?Added bar stiffness≠increased frame stiffnessCarbon fiber rods are found to be 15% stiffer than stainless tubes of the same diameter in bending. In this test, the stainless deformed before breaking. The carbon rods remained in the elastic range over the whole testing range.But the frames were less stiff. How could that be? Because everything else was the same, the difference was assumed to be due to the connection between the clamps and the bars and presumed slippage between the two. For this reason, it is important to know your frame!Kowalski M, et al, Comparative Biomechanical Evaluation of Different External Fixator Sidebars: Stainless-Steel Tubes versus Carbon Fiber Bars, JOT 10(7): , 1996
18 Ring Fixators Components: Tensioned thin wires olive or straight Wire and half pin clampsRingsRodsMotors and hinges (not pictured)Ring fixator combines components of the standard ex fix with a ring frame constructUseful for correction of: (Reconstruction)LengthAngulationrotationComponents:RingsRing fixators employ frame components that pass around the limbMade of Metal or Carbon fiberFull vs. Half-ring designB.PinsPins or wires may be inserted from multiple directionsMostly smooth, varying diameter from 1.5 to 2.0mmSpecialized push/pull wires (olive wires) availableBone purchase achieved via friction alone but stability through wire tension
19 Ring Fixators Principles: Can maintain purchase in metaphyseal bone Multiple tensioned thin wires ( kg)Place wires as close to 90o to each otherHalf pins also effectiveUse full rings (more difficult to deform)Can maintain purchase in metaphyseal boneAllows dynamic axial loadingMay allow joint motionMechanics:Overall stiffness increases with the number of wires used, the diameter of the ring, the angle between the wires, and wire tension kg of tension is typically usedRing constructs exhibit excellent bending and torsional stiffness but are markedly less stiff than half-pin or full-pin frames under axial loading conditions. However as axial load increases so does stiffnessOpen ring design are less stiff than full-ring constructsWhen used in a bone segment avoid using the ring as a single plane of fixation. Add a second ring or a half pin either proximally or distally to avoid rotation of that segment around the pins
20 Multiplanar Adjustable Ring Fixators Application with wire or half pinsAdjustable with 6 degrees of freedomDeformity correctionacutechronic
23 Unilateral uniplanar Unilateral biplanar Frame TypesUniplanarUnilateralBilateralPin transfixes extremityBiplanarCircular (Ring Fixator)May use Half-pins and/or transfixion wiresHybridCombines rings with planar framesBiplanar frames always use transfixion wires or pinsUnilateral uniplanar Unilateral biplanar
24 From Rockwood and Green’s, 5th Ed Hybrid FixatorsCombines the advantages of ring fixators in periarticular areas with simplicity of planar half pin fixators in diaphyseal boneHybrid fixators have gained great popularity in the treatment of periarticular fractures securing the metaphyseal segment with the tensioned wires and the diaphysis with half pins using each method where it is best suited.From Rockwood and Green’s, 5th Ed
25 Biomechanical Comparison Hybrid vs Ring Frames Ring frames resist axial and bending deformation better than any hybrid modificationAdding 2nd proximal ring and anterior half pin improves stability of hybrid frameClinical application: Use full ring fixator for fx with bone defects or expected long frame timePugh et al, JOT, ‘99Yilmaz et al, Clin Biomech, 2003Roberts et al, JOT, 2003
26 MRI Compatability Issues: Safety Magnetic field displacing ferromagnetic objectPotential missileHeat generation by induced fieldsImage qualityImage distortion
27 MRI CompatibilityStainless steel components (pins, clamps, rings) most at risk for attraction and heatingTitanium (pins), aluminum (rods, clamps, rings) and carbon fiber (rods, rings) demonstrate minimal heating and attractionAlmost all are safe if the components are not directly within the scanner (subject to local policy)Consider use of MRI “safe” ex fix when area interest is spanned by the frame and use titanium pinsKumar, JOR, 2006Davison, JOT, 2004Cannada, CORR, 1995
28 Frame Types Standard frame Joint spanning frame: NonarticulatedArticulated frameDistraction or Correction frameThere are 3 main types of frame placement/design:Standard frame used in definitive treatment or as temporary frameNonarticulated Joint spanning often used as a temporary “damage control” frame or allows for soft tissue recovery as in pilon fracturesArticulated
29 Standard Frame Standard Frame Design Diaphyseal region Allows adjacent joint motionStableThe standard frame:Mainly used in diaphyseal fractures and thus, does not cross the jointAllows motion of the joints above and below the fractureHighly stable construct
30 Joint Spanning Frame Joint Spanning Frame Indications: Peri-articular fxDefinitive fixation through ligamentotaxisTemporizingPlace pins away from possible ORIF incision sitesArthrodesisStabilization of limb with severe ligamentous or vascular injury: Damage controlJoint spanning frameUseful for comminuted intra-articular and peri-articular fracture patternsImmobilizes the jointUseful as a temporizing frame and/or as a definitive treatment in combination with limited internal fixationIt is also useful in arthrodesis, especially in association with infection where internal fixation is not ideal
31 Articulated Frame Articulating Frame Limited indications Intra- and peri-articular fractures or ligamentous injuryMost commonly used in the ankle, elbow and kneeAllows joint motionRequires precise placement of hinge in the axis of joint motionArticulated frame:Limited indicationAllows for joint motionComplex construct with high learning curveMainly utilized for intra-articular fracture patterns(Figure from: Rockwood and Green, Fractures in Adults, 4th ed, Lippincott-Raven, 1996)
32 Correction of Deformity or Defects May use unilateral or ring framesSimple deformities may use simple framesComplex deformities require more complex framesAll require careful planning
33 3B tibia with segmental bone loss, 3A plateau, temporary spanning ex fix
34 Convert to circular frame, orif plateau Corticotomy and distraction
37 EXTERNAL FIXATION Biomechanics Leave the Eiffel tower in Paris!Understand fixator mechanicsdo not over or underbuild frame!
38 Fixator Mechanics: Pin Factors Larger pin diameterIncreased pin spreadon the same side of the fractureIncreased number of pins (both in and out of plane of construct)Pin Spread:A vs B,C. Increased pin spread increases overall stability of the fixator construct.
39 Fixator Mechanics: Pin Factors Oblique fxs subject to shearUse oblique pin to counter these effectsPin Spread:A vs B,C. Increased pin spread increases overall stability of the fixator construct.Metcalfe, et al, JBJS B, 2005Lowenberg, et al, CORR, 2008
40 Fixator Mechanics: Rod Factors Frames placed in the same plane as the applied loadDecreased distance from bars to boneStacking of barsDecreased distance from bar to bone:When the fixator bar is placed closer to the bone, the overall construct is more stable as depicted in the figure as decrease deflection in reaction to equivalent forcesDouble Stacking of Bars:When a second connecting rod/bar is added, the overall construct is made more stable/rigid
41 Frame Mechanics: Biplanar Construct Linkage between frames in perpendicular planes (DELTA)Controls each plane of deformationDelta Frame:The delta configuration offers increased resistance to deformation in two planes without the need for transfixion pins, avoiding the attendant risks of neurovascular injury
42 Frame Mechanics: Ring Fixators Spread wires to as close to 90o as anatomically possibleUse at least 2 planes of wires/half pins in each major bone segment
43 Modes of Fixation Compression Neutralization Distraction Sufficient bone stockEnhances stabilityIntimate contact of bony endsTypically used in arthrodesis or to complete union of a fractureNeutralizationComminution or bone loss presentMaintains length and alignmentResists external deforming forcesDistractionReduction through ligamentotaxisTemporizing deviceDistraction osteogenesisModes of Fixation:CompressionNeutralizationDistraction
44 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed, BiologyFracture healing by stable yet less rigid systemsDynamizationMicromotionmicromotion = callus formationCurrent External fixation systems have been designed to allow micromotion at the fracture site to promote callus formationStable yet less rigid systems of external fixation maintain alignment and length while allowing and actually encouraging beneficial micromotionFracture Healing by:DynamizationMicromotionFigure:Radiographs depict osteotomy in sheep at different stages of healingA. Rigidly Fixed: shows little callous formation at 10 weeksB. Dynamization and Applied Micromotion: shows exuberant callous formation at 10 weeksKenwright summarizes studies defining the changes in callus formation with micromotion attempting to define the optimal amt of stress.Larsson et al demonstrated increased callus attained earlier with improved endosteal bone formation resulting in better torsional stiffness in a dog model comparing axial dynamization vs rigid control(Figures from: Rockwood and Green, Fractures in Adults, 4th ed,Lippincott-Raven, 1996)Kenwright, CORR, 1998Larsson, CORR, 2001
45 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed, BiologyDynamization = load-sharing construct that promote micromotion at the fracture siteControlled load-sharing helps to "work harden" the fracture callus and accelerate remodelingDynamization = load-sharing construct that promote micromotion at the fracture siteControlled load-sharing helps to "work harden" the fracture callus and accelerate remodelingDynamization is achieved by progressive closure of the fracture, promoting micromotion at fracture site.This avoids the distraction that is believed to be associated with non-unions in early fixator designs(Figures from: Rockwood and Green, Fractures in Adults, 4th ed,Lippincott-Raven, 1996)Kenwright and Richardson, JBJS-B, ‘91Quicker union less refractureMarsh and Nepola, ’9196% union at 24.6 wks
46 Anatomic Considerations Fundamental knowledge of the anatomy is criticalAvoidance of major nerves,vessels and organs (pelvis) is mandatoryAvoid joints and joint capsulesProximal tibial pins should be placed 14 mm distal to articular surface to avoid capsular reflectionMinimize muscle/tendon impalement (especially those with large excursions)Anatomic considerationsFundamental knowledge of the anatomy is criticalAvoidance of major Nerves,Vessels and Organs (Pelvis) is mandatory
47 Lower Extremity “safe” sites 14 mmAvoidNervesVesselsJoint capsulesMinimizeMuscle transfixionFundamental knowledge of anatomy is critical to avoid major nerve, vessels and organs.In the upper extremity dissection is recommended to avoid neurovascular injury.
48 Upper Extremity “Safe” Sites Humerus: narrow lanesProximal: axillary nMid: radial nerveDistal: radial, median and ulnar nDissect to bone, Use sleevesUlna: safe subcutaneous border, avoid overpenetrationRadius: narrow lanesProximal: avoid because radial n and PIN, thick muscle sleeveMid and distal: use dissection to avoid sup. radial n.
49 Damage Control and Temporary Frames Initial frame application rapidEnough to stabilize but is not definitive frame!Be aware of definitive fixation optionsAvoid pins in surgical approach sitesDepending on clinical situation may consider minimal fixation of articular surface at initial surgery
50 Conversion to Internal Fixation Generally safe within 2-3 wksBhandari, JOT, 2005Meta analysis: 6 femur, 9 tibia, all but one retrospectiveInfection in tibia and femur <4%Rods or plates appropriateUse with caution with signs of pin irritationConsider staged procedureRemove and curette sitesReturn following healing for definitive fixationExtreme caution with established pin track infectionMaurer, ’8977% deep infection with h/o pin infection
51 Evidence Femur fx Nowotarski, JBJS-A, ’00 59 fx (19 open), 54 pts, Convert at 7 days (1-49 days)1 infected nonunion, 1 aseptic nonunionScalea, J Trauma, ’0043 ex-fix then nailed vs 284 primary IM nailISS 26.8 vs 16.8Fluids 11.9l vs 6.2l first 24 hrsOR time 35 min EBL 90cc vs 135 min EBL 400ccEx fix group 1 infected nonunion, 1 aseptic nonunionBilat open femur, massive compartment syndrome, ex fix then nailScalea:Patients treated with EF had more severe injuries with significantly higher Injury Severity Scores (26.8 vs. 16.8) and required significantly more fluid (11.9 vs. 6.2 liters) and blood (1.5 vs. 1.0 liters) in the initial 24 hours. Glasgow Coma Scale score was lower (p < 0.01) in those treated with EF (11 vs. 14.2). Twelve patients (28%) had head injuries severe enough to require intracranial pressure monitoring. All 12 required therapy for intracranial pressure control with mannitol (100%), barbiturates (75%), and/or hyperventilation (75%). Most patients had more than one contraindication to IMN, including head injury in 46% of cases, hemodynamic instability in 65%, thoracoabdominal injuries in 51%, and/or other serious injuries in 46%, most often multiple orthopedic injuries. Median operating room time for EF was 35 minutes with estimated blood loss of 90 mL. IMN was performed in 35 of 43 patients at a mean of 4.8 days after EF. Median operating room time for IMN was 135 minutes with an estimated blood loss of 400 mL. One patient died before IMN. One other patient with a mangled extremity was treated with amputation after EF. There was one complication of EF, i.e., bleeding around a pin site, which was self-limited. Four patients in the EF group died, three from head injuries and one from acute organ failure. No death was secondary to the fracture treatment selected. One patient who had EF followed by IMN had bone infection and another had acute hardware failure
52 Evidence Pilon fx 49 fxs, 22 open plating @ 12-14 days, Sirkin et al, JOT, 199949 fxs, 22 opendays,5 minor wound problems, 1 osteomyelitisPatterson & Cole, JOT, 199922 fxs24 d (15-49)no wound healing problems1 malunion, 1 nonunion
53 Complications Pin-track infection/loosening Frame or Pin/Wire Failure MalunionNon-unionSoft-tissue impalementCompartment syndromeComplication with the use of the External Fixator include:Pin-track infectionPin LooseningFrame or Pin/Wire FailureMalunionNon-unionSoft-tissue impalementCompartment syndrome
54 Pin-track Infection Most common complication 0 – 14.2% incidence 4 stages:Stage I: Seropurulent DrainageStage II: Superficial CellulitisStage III: Deep InfectionStage IV: OsteomyelitisPin-track infectionMost common complication0 – 14.2% incidence4 stages:Stage I : Seropurulent DrainageStage II : Superficial CellulitisStage III: Deep InfectionStage IV: Osteomyelitis
56 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed, Pin-track InfectionPrevention:Proper pin/wire insertion technique:Subcutaneous bone bordersAway from zone of injuryAdequate skin incisionCannulae to prevent soft tissue injury during insertionSharp drill bits and irrigation to prevent thermal necrosisManual pin insertionPrevention:Proper pin/wire insertion technique:Pins placed in subcutaneous bone bordersPins placed away from zone of injuryUse of adequate skin incisionUse of cannulae to prevent introduction of skin floraUse of sharp drill bits to prevent thermal necrosisFixator pins should be placed away from the zone of injury to minimize/avoid pin-track contamination of the fracture site(Figures from: Rockwood and Green, Fractures in Adults, 4th ed,Lippincott-Raven, 1996)
57 Pin-track Infection Postoperative care: Clean implant/skin interface SalineGauzeShowerPost-operative Care of Pin-track include:Maintain a clean implant/skin interface with as little irritation as possibleSaline vs. other cleaning solutions (all forms of vigorous mechanical cleansing as well as the use of noxious chemical treatments (peroxide, betadine) have been associated with worsened rates of pin-site problems)Use of gauze around pins to hold skin down to prevent excessive motion at pin/skin interfaceShower vs. bathing and then, only after wounds are healed
58 Pin-track Infection Treatment: Stage I: aggressive pin-site care and oral cephalosporinStage II: same as Stage I and +/- Parenteral AbxStage III: Removal/exchange of pin plus Parenteral AbxStage IV: same as Stage III, culture pin site for offending organism, specific IV Abx for 10 to 14 days, surgical debridement of pin siteTreatment of Pin-track infection should consist of:Stage I: aggressive pin-site care and oral cephalosporinStage II:same as Stage I and +/- Parenteral AbxStage III: Parenteral Abx plus removal of pinStage IV: same as Stage III , culture pin site for offending organism, specific IV Abx for 10 to 14 days, surgical debridement of pin site
59 Pin Loosening Factors influencing Pin Loosening: Pin track infection/osteomyelitisThermonecrosisDelayed union or non-unionBending Pre-loadPin LooseningFactors influencing Pin Loosening:Bending Pre-load: excess eccentric stresses at the pin-bone interface leading to bone necrosisExcess stress at the pin-bone interface is undesirable and leads to early implant looseningCauses rapid pressure necrosis on the compression side of the preloaded pin thermonecrosissubsequent bony resorption (which can occur as a result of improper pin insertion technique)osteomyelitis secondary to severe pin tract infectionDelayed union or non-union (all implants eventually loosen)Self-drilling pins or dull drill bits tend to generate heat (thermonecrosis) and microfracture during insertion.Pre-drilling pin holes with a sharp drill helps minimize heat generation and bone damage while use of a drill sleeve or cannula minimizes soft tissue damage (Muscle does not wrap around the pin and necrose creating a culture medium.Self-tapping screws may then be introduced without thermonecrosis and microfracture.
60 Pin Loosening Prevention: Treatment: Proper pin/wire insertion techniquesRadial preloadEuthermic pin insertionAdequate soft-tissue releaseBone graft earlyPin coatingsTreatment:Replace/remove loose pinPin loosening can be prevented by:1)Proper pin/wire insertion techniques that stress predrilling of screw holes2)Radial preload (avoiding bending preload)See Figure at lower right:Radial preload improves screw fixation and prevents loosening.This is achieved by drilling a pilot hole slightly smaller than the root diameter of the screwAnd by using a tapered root-diameter screw design to produce a radial preload as the screw is introduced3)Euthermic pin insertion4)Adequate soft-tissue release around the implant sites5)Bone graft defects early if indicatedTreatment for loose pins:Replace/remove loose pin
61 Frame Failure Incidence: Rare Theoretically can occur with recycling of old framesHowever, no proof that frames can not be re-usedAnother complication is Frame FailureIt is quiet rareThere are anecdotal reports onlyIt can theoretically occur with recycling of old framesHowever, there is no proof that frames cannot be re-used
62 Malunion Intra-operative causes: Prevention: Treatment: Due to poor techniquePrevention:Clear pre-operative planningPrep contralateral limb for comparisonUse fluoroscopic and/or intra-operative filmsAdequate constructTreatment:Early: Correct deformity and adjust or re-apply frame prior to bony unionLate: Reconstructive correction of malunionIntra-operative causes are usually due to poor techniquePrevent malunion by:Clear pre-operative planning (understand deforming forces and control for them)Prep contralateral limb for comparisonUse fluoroscopic and/or intra-operative filmsOnce malunion has occurred treatment should be initiated:Early: Correct deformity and re-apply frame prior to bony unionLate: Reconstructive correction of malunion
63 Malunion Post-operative causes: Prevention: Treatment: Due to frame failurePrevention:Proper follow-up with both clinical and radiographic check-upsAdherence to appropriate weight-bearing restrictionsCheck and re-tighten frame at periodic intervalsTreatment:Osteotomy/reconstructionPost-operative causes of malunion is most probably due to frame failureOne can prevent this from occurring by:Proper follow-up with both clinical and radiographic check-upsAdherence to appropriate weight-bearing restrictionsCheck and re-tighten frame at periodic intervalsTreatment is the same as for intra-operative:(See previous slide)
64 Non-unionUnion rates comparable to those achieved with internal fixation devicesMinimized by:Avoiding distraction at fracture siteEarly bone graftingStable/rigid constructGood surgical techniqueControl infectionsEarly wt bearingProgressive dynamizationIt is important to note that union rates in fractures treated with an external fixator is comparable to those achieved with internal fixation devicesNon-union can be minimized by:Avoiding distraction at fracture siteEarly bone graftingStable/rigid constructGood surgical techniqueControlling infections
65 Soft-tissue Impalement Tethering of soft tissues can result in:Loss of motionScarringVessel injuryPrevention:Check ROM intra-operativelyAvoid piercing muscle or tendonsPosition joint in NEUTRALEarly stretching and ROM exercisesSoft tissue impalement probably occurs more often than we think.Tethering of soft tissues can result in:Temporary or permanent loss of motionScarring of tendon and/or muscleVessel Impalement and eventual erosion Most frequent mechanism of Vascular InjuryA. The pin displaces the vesselB. The vessels lie tented over the pin causing erosionC. Bleeding is noted after pin removalPrevention:Know your anatomyGood surgical techniquePrevention include:ROM should be check intra-operatively after frame appliedAvoid piercing muscle or tendons when possiblePlace joints locked in frame in neutral position I.e.. AnkleStretching and ROM exercises post-op to keep the joints supple
66 Compartment Syndrome Rare Cause: Prevention: Injury related pin or wire causing intracompartmental bleedingPrevention:Clear understanding of the anatomyGood techniquePost-operative vigilanceCompartment syndrome occurring because of the application of an external fixator is rareThe cause is usually injury related, but if due to the fixator, is most probably related to a pin or wire causing compartment bleedingPreventative technique include:Clear understanding of the anatomyGood techniquePost-operative vigilance
67 Future Areas of Development Pin coatings/sleevesReduce infectionReduce pin looseningOptimization of dynamization for fracture healingIncreasing ease of use/reduced cost
68 Plan ahead! Construct Tips Chose optimal pin diameter Use good insertion techniquePlace clamps and frames close to skinFrame in plane of deforming forcesStack frame (2 bars)Re-use/Recycle components (requires certified inspection).Plan ahead!
69 ReferencesBhandari M, Zlowodski M, Tornetta P, Schmidt A, Templeman D. Intramedullary Nailing Following External Fixation in Femoral and Tibial Shaft Fractures. Evidence-Based Orthopaedic Trauma , JOT, 19(2): , 2005.Cannada LK, Herzenberg JE, Hughes PM, Belkoff S. Safety and Image Artifact of External Fixators and Magnetic Resonance Imaging. CORR, 317, :1995.Davison BL, Cantu RV, Van Woerkom S. The Magnetic Attraction of Lower Extremity External Fixators in an MRI Suite. JOT, 18 (1): 24-27, 2004.Kenwright J, Richardson JB, Cunningham, et al. Axial movement and tibial fractures. A controlled randomized trial of treatment, JBJS-B, 73 (4): , 1991.Kenwright J , Gardner T. Mechanical influences on tibial fracture healing. CORR, 355: ,1998.Kowalski, M et al, Comparative Biomechanical Evaluation of Different External Fixator Sidebars: Stainless-Steel Tubes versus Carbon Fiber Bars, JOT 10(7): , 1996.Kumar R, Lerski RA, Gandy S, Clift BA, Abboud RJ. Safety of orthopedic implants in Magnetic Resonance Imaging: an Experimental Verification. J Orthop Res, 24 (9): , 2006.Larsson S, Kim W, Caja VL, Egger EL, Inoue N, Chao EY. Effect of early axial dynamization on tibial bone healing: a study in dogs. CORR, 388: , 2001.Lowenberg DW, Nork S, Abruzzo FM. The correlation of shearing force with fracture line migration for progressive fracture obliquities stabilized by external fixation in the tibial model. CORR, 466:2947–2954, 2008.Marsh JL. Nepola JV, Wuest TK, Osteen D, Cox K, Oppenheim W. Unilateral External Fixation Until Healing with the Dynamic Axial Fixator for Severe Open Tibial Fractures. Review of Two Consecutive Series , JOT, 5(3): , 1991.Maurer DJ, Merkow RL, Gustilo RB. Infection after intramedullary nailing of severe open tibial fractures initially treated with external fixation. JBJS-A, 71(6), ,Metcalfe AJ, Saleh M, Yang L. Techniques for improving stability in oblique fractures treated by circular fixation with particular reference to the sagittal plane. JBJS B, 87 (6): , 2005.Moroni A, Faldini C, Marchetti S, Manca M, Consoli V, Giannini S. Improvement of the Bone-Pin Interface Strength in Osteoporotic Bone with Use of Hydroxyapatite-Coated Tapered External-Fixation Pins: A Prospective, Randomized Clinical Study of Wrist Fractures . JBJS –A, 83: , 2001.Moroni A, Faldini C. Pegreffi F. Hoang-Kim A. Vannini F. Giannini S. Dynamic Hip Screw versus External Fixation for Treatment of Osteoporotic Pertrochanteric Fractures, J BJS-A. 87: , 2005.Moroni A. Faldini C. Rocca M. Stea S. Giannini S. Improvement of the bone-screw interface strength with hydroxyapatite-coated and titanium-coated AO/ASIF cortical screws. J OT. 16(4): ,Nowotarski PJ, Turen CH, Brumback RJ, Scarboro JM, Conversion of External Fixation to Intramedullary Nailing for Fractures of the Shaft of the Femur in Multiply Injured Patients, JBJS-A, 82: , 2000.Patterson MJ, Cole J. Two-Staged Delayed Open Reduction and Internal Fixation of Severe Pilon Fractures. JOT, 13(2): 85-91, 1999.Pugh K.J, Wolinsky PR, Dawson JM, Stahlman GC. The Biomechanics of Hybrid External Fixation. JOT. 13(1):20-26, 1999.Roberts C, Dodds JC, Perry K, Beck D, Seligson D, Voor M. Hybrid External Fixation of the Proximal Tibia: Strategies to Improve Frame Stability. JOT, 17(6): , 2003.Scalea TM, Boswell SA, Scott JD, Mitchell KA, Kramer ME, Pollak AN. External Fixation as a Bridge to Intramedullary Nailing for Patients with Multiple Injuries and with Femur Fractures: Damage Control Orthopedics. J Trauma, 48(4): , 2000.Sirkin M, Sanders R, DiPasquale T, Herscovici, A Staged Protocol for Soft Tissue Management in the Treatment of Complex Pilon Fractures. JOT, 13(2): 78-84, 1999.Yilmaz E, Belhan O, Karakurt L, Arslan N, Serin E. Mechanical performance of hybrid Ilizarov external fixator in comparison with Ilizarov circular external fixator. Clin Biomech, 18 (6): 518, 2003.
70 Summary Multiple applications Choose components and geometry suitable for particular applicationAppropriate use can lead to excellent resultsRecognize and correct complications earlyIf you would like to volunteer as an author for the Resident Slide Project or recommend updates to any of the following slides, please send an toOTAaboutQuestions/CommentsReturn toGeneral/PrinciplesIndex