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Principles of External Fixation

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1 Principles of External Fixation
Roman Hayda, MD Original 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
Complications In 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 fractures Pediatric fractures Temporary fx care “Damage control” Long bone fracture temporization Pelvic ring injury Periarticular fractures Pilon fracture Malunion/nonunion Arthrodesis Osteomyelitis Limb deformity/length inequality Congenital Acquired Indications 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 application Useful both as a temporizing or definitive stabilization device Reconstructive and salvage applications Complex 3-C humerus fx External 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
Mechanical Distraction of fracture site Inadequate immobilization Pin-bone interface failure Weight/bulk Refracture (pediatric femur) Biologic Infection (pin track) May preclude conversion to IM nailing or internal fixation Neurovascular injury Tethering of muscle Soft tissue contracture May result in malunion/nonunion, loss of function There 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
Pins Clamps Connecting rods The “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 Pins Principle: The pin is the critical link between the bone and the frame Pin diameter Bending stiffness proportional to r4 5mm pin 144% stiffer than 4mm pin Pin insertion technique respecting bone and soft tissue < 1/3 dia Factors that influence pin strength and rigidity include: Material Pin diameter Pin design Most 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 failure Too 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 pins 2) shorter threads to engage only the far cortex 3) pins with longer threaded portions

8 Pins Various diameters, lengths, and designs Materials 2.5 mm pin
4 mm short thread pin 5 mm predrilled pin 6 mm tapered or conical pin 5 mm self-drilling and self tapping pin 5 mm centrally threaded pin Materials Stainless steel Titanium More biocompatible Less stiff Pins 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 interface B. Tapered thread design to limit the magnitude of the stress riser at any single point C. Shorter thread design to move the stress riser to the far-cortical side

9 Self Drilling and Tapping
Pin Geometry ‘Blunt’ pins - Straight - Conical Pin 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 coatings Recent development of various coatings (Chlorohexidine, Silver, Hydroxyapatite) Improve fixation to bone Decrease infection Moroni, JOT, ’02 Animal study, HA pin 13X higher extraction torque vs stainless and titanium and equal to insertion torque Moroni, JBJS A, ’05 0/50 pts pin infection in tx of pertrochanteric fx Moroni 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 skin Spread soft tissues to bone Use sharp drill with sleeve Irrigate while drilling Place appropriate pin using sleeve Blunt Schantz pins Generous Skin incisions blunt dissection to bone Soft tissue protection Sharp Drill bits Irrigation minimize thermal necrosis Insertion with T-handle chuck Bicortical fixation Avoid soft tissue damage and bone thermal necrosis

12 Pin insertion Self drilling pin considerations vs. Short drill flutes
thermal necrosis stripping of near cortex with far cortex contact Quick insertion Useful for short term applications vs. 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 Length Half Pins single point of entry Engage two cortices Transfixation Pins Bilateral, uniplanar fixation lower stresses at pin bone interface Limited anatomic sites (nv injury) Traveling traction Half 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 mm Tibia – 5 or 6 mm Humerus – 5 mm Forearm – 4 mm Hand, Foot – 3 mm Remember 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 dia Slide courtesy Matthew Camuso

15 Clamps Principles Two general varieties: Features:
Single pin to bar clamps Multiple pin to bar clamps Features: Multi-planar adjustability Open vs closed end Principles Must securely hold the frame to the pin Clamps placed closer to bone increases the stiffness of the entire fixator construct Clamps come in 2 general varieties: The single pin to bar clamps, as shown on the left The multi-pin to frame clamp, shown on the middle and right Clamps 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: Steel Aluminum Carbon fiber Design Simple rod Articulated Telescoping Principle increased diameter = increased stiffness and strength Stacked (2 parallel bars) = increased stiffness Connecting rods are made from a variety of materials: Steel, titanium, plastics, carbon fiber Metals 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
Bars Stainless vs Carbon Fiber Radiolucency ↑ diameter = ↑ stiffness Carbon 15% stiffer vs stainless steel in loading to failure frames with carbon fiber are only 85% as stiff ? ? ? ?Weak link is clamp to carbon bar? Added bar stiffness increased frame stiffness Carbon 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 clamps Rings Rods Motors and hinges (not pictured) Ring fixator combines components of the standard ex fix with a ring frame construct Useful for correction of: (Reconstruction) Length Angulation rotation Components: Rings Ring fixators employ frame components that pass around the limb Made of Metal or Carbon fiber Full vs. Half-ring design B.Pins Pins or wires may be inserted from multiple directions Mostly smooth, varying diameter from 1.5 to 2.0mm Specialized push/pull wires (olive wires) available Bone 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 other Half pins also effective Use full rings (more difficult to deform) Can maintain purchase in metaphyseal bone Allows dynamic axial loading May allow joint motion Mechanics: 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 used Ring 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 stiffness Open ring design are less stiff than full-ring constructs When 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 pins Adjustable with 6 degrees of freedom Deformity correction acute chronic

21 Type 3A open tibia fracture with bone loss

22 Following frame adjustment and bone grafting

23 Unilateral uniplanar Unilateral biplanar
Frame Types Uniplanar Unilateral Bilateral Pin transfixes extremity Biplanar Circular (Ring Fixator) May use Half-pins and/or transfixion wires Hybrid Combines rings with planar frames Biplanar frames always use transfixion wires or pins Unilateral uniplanar Unilateral biplanar

24 From Rockwood and Green’s, 5th Ed
Hybrid Fixators Combines the advantages of ring fixators in periarticular areas with simplicity of planar half pin fixators in diaphyseal bone Hybrid 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 modification Adding 2nd proximal ring and anterior half pin improves stability of hybrid frame Clinical application: Use full ring fixator for fx with bone defects or expected long frame time Pugh et al, JOT, ‘99 Yilmaz et al, Clin Biomech, 2003 Roberts et al, JOT, 2003

26 MRI Compatability Issues: Safety
Magnetic field displacing ferromagnetic object Potential missile Heat generation by induced fields Image quality Image distortion

27 MRI Compatibility Stainless steel components (pins, clamps, rings) most at risk for attraction and heating Titanium (pins), aluminum (rods, clamps, rings) and carbon fiber (rods, rings) demonstrate minimal heating and attraction Almost 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 pins Kumar, JOR, 2006 Davison, JOT, 2004 Cannada, CORR, 1995

28 Frame Types Standard frame Joint spanning frame:
Nonarticulated Articulated frame Distraction or Correction frame There are 3 main types of frame placement/design: Standard frame used in definitive treatment or as temporary frame Nonarticulated Joint spanning often used as a temporary “damage control” frame or allows for soft tissue recovery as in pilon fractures Articulated

29 Standard Frame Standard Frame Design Diaphyseal region
Allows adjacent joint motion Stable The standard frame: Mainly used in diaphyseal fractures and thus, does not cross the joint Allows motion of the joints above and below the fracture Highly stable construct

30 Joint Spanning Frame Joint Spanning Frame Indications:
Peri-articular fx Definitive fixation through ligamentotaxis Temporizing Place pins away from possible ORIF incision sites Arthrodesis Stabilization of limb with severe ligamentous or vascular injury: Damage control Joint spanning frame Useful for comminuted intra-articular and peri-articular fracture patterns Immobilizes the joint Useful as a temporizing frame and/or as a definitive treatment in combination with limited internal fixation It 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 injury Most commonly used in the ankle, elbow and knee Allows joint motion Requires precise placement of hinge in the axis of joint motion Articulated frame: Limited indication Allows for joint motion Complex construct with high learning curve Mainly 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 frames Simple deformities may use simple frames Complex deformities require more complex frames All 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

35 Consolidation *note: docking site bone grafted

36 Healed

Leave the Eiffel tower in Paris! Understand fixator mechanics do not over or underbuild frame!

38 Fixator Mechanics: Pin Factors
Larger pin diameter Increased pin spread on the same side of the fracture Increased 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 shear Use oblique pin to counter these effects Pin Spread: A vs B,C. Increased pin spread increases overall stability of the fixator construct. Metcalfe, et al, JBJS B, 2005 Lowenberg, et al, CORR, 2008

40 Fixator Mechanics: Rod Factors
Frames placed in the same plane as the applied load Decreased distance from bars to bone Stacking of bars Decreased 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 forces Double 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 deformation Delta 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 possible Use at least 2 planes of wires/half pins in each major bone segment

43 Modes of Fixation Compression Neutralization Distraction
Sufficient bone stock Enhances stability Intimate contact of bony ends Typically used in arthrodesis or to complete union of a fracture Neutralization Comminution or bone loss present Maintains length and alignment Resists external deforming forces Distraction Reduction through ligamentotaxis Temporizing device Distraction osteogenesis Modes of Fixation: Compression Neutralization Distraction

44 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed,
Biology Fracture healing by stable yet less rigid systems Dynamization Micromotion micromotion = callus formation Current External fixation systems have been designed to allow micromotion at the fracture site to promote callus formation Stable yet less rigid systems of external fixation maintain alignment and length while allowing and actually encouraging beneficial micromotion Fracture Healing by: Dynamization Micromotion Figure: Radiographs depict osteotomy in sheep at different stages of healing A. Rigidly Fixed: shows little callous formation at 10 weeks B. Dynamization and Applied Micromotion: shows exuberant callous formation at 10 weeks Kenwright 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, 1998 Larsson, CORR, 2001

45 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed,
Biology Dynamization = load-sharing construct that promote micromotion at the fracture site Controlled load-sharing helps to "work harden" the fracture callus and accelerate remodeling Dynamization = load-sharing construct that promote micromotion at the fracture site Controlled load-sharing helps to "work harden" the fracture callus and accelerate remodeling Dynamization 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, ‘91 Quicker union less refracture Marsh and Nepola, ’91 96% union at 24.6 wks

46 Anatomic Considerations
Fundamental knowledge of the anatomy is critical Avoidance of major nerves,vessels and organs (pelvis) is mandatory Avoid joints and joint capsules Proximal tibial pins should be placed 14 mm distal to articular surface to avoid capsular reflection Minimize muscle/tendon impalement (especially those with large excursions) Anatomic considerations Fundamental knowledge of the anatomy is critical Avoidance of major Nerves,Vessels and Organs (Pelvis) is mandatory

47 Lower Extremity “safe” sites
14 mm Avoid Nerves Vessels Joint capsules Minimize Muscle transfixion Fundamental 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 lanes Proximal: axillary n Mid: radial nerve Distal: radial, median and ulnar n Dissect to bone, Use sleeves Ulna: safe subcutaneous border, avoid overpenetration Radius: narrow lanes Proximal: avoid because radial n and PIN, thick muscle sleeve Mid and distal: use dissection to avoid sup. radial n.

49 Damage Control and Temporary Frames
Initial frame application rapid Enough to stabilize but is not definitive frame! Be aware of definitive fixation options Avoid pins in surgical approach sites Depending on clinical situation may consider minimal fixation of articular surface at initial surgery

50 Conversion to Internal Fixation
Generally safe within 2-3 wks Bhandari, JOT, 2005 Meta analysis: 6 femur, 9 tibia, all but one retrospective Infection in tibia and femur <4% Rods or plates appropriate Use with caution with signs of pin irritation Consider staged procedure Remove and curette sites Return following healing for definitive fixation Extreme caution with established pin track infection Maurer, ’89 77% 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 nonunion Scalea, J Trauma, ’00 43 ex-fix then nailed vs 284 primary IM nail ISS 26.8 vs 16.8 Fluids 11.9l vs 6.2l first 24 hrs OR time 35 min EBL 90cc vs 135 min EBL 400cc Ex fix group 1 infected nonunion, 1 aseptic nonunion Bilat open femur, massive compartment syndrome, ex fix then nail Scalea: 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, 1999 49 fxs, 22 open days, 5 minor wound problems, 1 osteomyelitis Patterson & Cole, JOT, 1999 22 fxs 24 d (15-49) no wound healing problems 1 malunion, 1 nonunion

53 Complications Pin-track infection/loosening Frame or Pin/Wire Failure
Malunion Non-union Soft-tissue impalement Compartment syndrome Complication with the use of the External Fixator include: Pin-track infection Pin Loosening Frame or Pin/Wire Failure Malunion Non-union Soft-tissue impalement Compartment syndrome

54 Pin-track Infection Most common complication 0 – 14.2% incidence
4 stages: Stage I: Seropurulent Drainage Stage II: Superficial Cellulitis Stage III: Deep Infection Stage IV: Osteomyelitis Pin-track infection Most common complication 0 – 14.2% incidence 4 stages: Stage I : Seropurulent Drainage Stage II : Superficial Cellulitis Stage III: Deep Infection Stage IV: Osteomyelitis

55 Pin-track Infection Mendes, ‘81 Velazco, ’83 12.5% Behrens, ’86 6.9%
Union Fx infection Malunion Pin Infection Mendes, ‘81 100% 4% NA Velazco, ’83 92% 5% 12.5% Behrens, ’86 1.3% 6.9% Steinfeld, ’88 97% 7.1% 23% 0.5% Marsh, ‘91 95% 10% Melendez, ’89 98% 22% 2% 14.2% Table Adapted from Browner, Skeletal Trauma, 1st Ed, W.B. Saunders 1992

56 (Figures from: Rockwood and Green, Fractures in Adults, 4th ed,
Pin-track Infection Prevention: Proper pin/wire insertion technique: Subcutaneous bone borders Away from zone of injury Adequate skin incision Cannulae to prevent soft tissue injury during insertion Sharp drill bits and irrigation to prevent thermal necrosis Manual pin insertion Prevention: Proper pin/wire insertion technique: Pins placed in subcutaneous bone borders Pins placed away from zone of injury Use of adequate skin incision Use of cannulae to prevent introduction of skin flora Use of sharp drill bits to prevent thermal necrosis Fixator 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
Saline Gauze Shower Post-operative Care of Pin-track include: Maintain a clean implant/skin interface with as little irritation as possible Saline 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 interface Shower vs. bathing and then, only after wounds are healed

58 Pin-track Infection Treatment:
Stage I: aggressive pin-site care and oral cephalosporin Stage II: same as Stage I and +/- Parenteral Abx Stage III: Removal/exchange of pin plus Parenteral Abx Stage IV: same as Stage III, culture pin site for offending organism, specific IV Abx for 10 to 14 days, surgical debridement of pin site Treatment of Pin-track infection should consist of: Stage I: aggressive pin-site care and oral cephalosporin Stage II:same as Stage I and +/- Parenteral Abx Stage III: Parenteral Abx plus removal of pin Stage 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/osteomyelitis Thermonecrosis Delayed union or non-union Bending Pre-load Pin Loosening Factors influencing Pin Loosening: Bending Pre-load: excess eccentric stresses at the pin-bone interface leading to bone necrosis Excess stress at the pin-bone interface is undesirable and leads to early implant loosening Causes rapid pressure necrosis on the compression side of the preloaded pin thermonecrosis subsequent bony resorption (which can occur as a result of improper pin insertion technique) osteomyelitis secondary to severe pin tract infection Delayed 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 techniques Radial preload Euthermic pin insertion Adequate soft-tissue release Bone graft early Pin coatings Treatment: Replace/remove loose pin Pin loosening can be prevented by: 1)Proper pin/wire insertion techniques that stress predrilling of screw holes 2)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 screw And by using a tapered root-diameter screw design to produce a radial preload as the screw is introduced 3)Euthermic pin insertion 4)Adequate soft-tissue release around the implant sites 5)Bone graft defects early if indicated Treatment for loose pins: Replace/remove loose pin

61 Frame Failure Incidence: Rare
Theoretically can occur with recycling of old frames However, no proof that frames can not be re-used Another complication is Frame Failure It is quiet rare There are anecdotal reports only It can theoretically occur with recycling of old frames However, there is no proof that frames cannot be re-used

62 Malunion Intra-operative causes: Prevention: Treatment:
Due to poor technique Prevention: Clear pre-operative planning Prep contralateral limb for comparison Use fluoroscopic and/or intra-operative films Adequate construct Treatment: Early: Correct deformity and adjust or re-apply frame prior to bony union Late: Reconstructive correction of malunion Intra-operative causes are usually due to poor technique Prevent malunion by: Clear pre-operative planning (understand deforming forces and control for them) Prep contralateral limb for comparison Use fluoroscopic and/or intra-operative films Once malunion has occurred treatment should be initiated: Early: Correct deformity and re-apply frame prior to bony union Late: Reconstructive correction of malunion

63 Malunion Post-operative causes: Prevention: Treatment:
Due to frame failure Prevention: Proper follow-up with both clinical and radiographic check-ups Adherence to appropriate weight-bearing restrictions Check and re-tighten frame at periodic intervals Treatment: Osteotomy/reconstruction Post-operative causes of malunion is most probably due to frame failure One can prevent this from occurring by: Proper follow-up with both clinical and radiographic check-ups Adherence to appropriate weight-bearing restrictions Check and re-tighten frame at periodic intervals Treatment is the same as for intra-operative: (See previous slide)

64 Non-union Union rates comparable to those achieved with internal fixation devices Minimized by: Avoiding distraction at fracture site Early bone grafting Stable/rigid construct Good surgical technique Control infections Early wt bearing Progressive dynamization It is important to note that union rates in fractures treated with an external fixator is comparable to those achieved with internal fixation devices Non-union can be minimized by: Avoiding distraction at fracture site Early bone grafting Stable/rigid construct Good surgical technique Controlling infections

65 Soft-tissue Impalement
Tethering of soft tissues can result in: Loss of motion Scarring Vessel injury Prevention: Check ROM intra-operatively Avoid piercing muscle or tendons Position joint in NEUTRAL Early stretching and ROM exercises Soft tissue impalement probably occurs more often than we think. Tethering of soft tissues can result in: Temporary or permanent loss of motion Scarring of tendon and/or muscle Vessel Impalement and eventual erosion Most frequent mechanism of Vascular Injury A. The pin displaces the vessel B. The vessels lie tented over the pin causing erosion C. Bleeding is noted after pin removal Prevention: Know your anatomy Good surgical technique Prevention include: ROM should be check intra-operatively after frame applied Avoid piercing muscle or tendons when possible Place joints locked in frame in neutral position I.e.. Ankle Stretching and ROM exercises post-op to keep the joints supple

66 Compartment Syndrome Rare Cause: Prevention: Injury related
pin or wire causing intracompartmental bleeding Prevention: Clear understanding of the anatomy Good technique Post-operative vigilance Compartment syndrome occurring because of the application of an external fixator is rare The cause is usually injury related, but if due to the fixator, is most probably related to a pin or wire causing compartment bleeding Preventative technique include: Clear understanding of the anatomy Good technique Post-operative vigilance

67 Future Areas of Development
Pin coatings/sleeves Reduce infection Reduce pin loosening Optimization of dynamization for fracture healing Increasing ease of use/reduced cost

68 Plan ahead! Construct Tips Chose optimal pin diameter
Use good insertion technique Place clamps and frames close to skin Frame in plane of deforming forces Stack frame (2 bars) Re-use/Recycle components (requires certified inspection). Plan ahead!

69 References Bhandari 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 application Appropriate use can lead to excellent results Recognize and correct complications early If 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 to OTA about Questions/Comments Return to General/Principles Index

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