Chapter 8: Principles of External Fixation

J. Tracy Watson

Chapter Outline

Historical Perspective

External fixation was described by Hippocrates almost 2,400 years ago, when he described a method to immobilize a fracture of the tibia, which also allowed inspection of the soft tissue injury. This was accomplished by wrapping the proximal and distal tibia with leather wraps, “such as are worn by persons confined for a length of time in large shackles, and they should have a thickened coat on each side, and they would be well stuffed and fit well, the one above the ankle, and the other below the knee. Four flexible rods, made of the cornel tree (European dogwood), of equal length should be placed between the knee and ankle wrap. If these things be properly contrived, they should occasion a proper and equable extension in a straight line. And the rods are commodiously arranged on either side of the ankle so as not to interfere with the position of the limb; and the wound is easily examined and arranged” (Fig. 8-1).133,229 
Figure 8-1
Hippocrates “shackle” external device for maintaining a tibia fracture at length.
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The history of modern external fixation dates back to the 19th century with Malgaigne’s description of an ingenious mechanism consisting of a clamp that approximated four transcutaneous metal prongs for use in reducing and maintaining patellar fractures. This was described in 1843 a full 12 years before the introduction of plaster casting techniques.116,229 

Origins of Monolateral External Fixation

The original description of the management of long bone fractures suggestive of an external fixator is attributed to a British surgeon, Keetley, in 1893.34,118 In an effort to decrease malunion and nonunion in the femur, rigid pins were inserted percutaneously into the femur and attached to an external splint system. “A carefully purified pin of thickly plated steel, made to enter through a puncture in the skin, cleansed with equal care” was passed through drill holes, one in each main fragment. The two horizontal arms of each device, suitably notched along the edges, were united by twists of wire, and the construct was then dressed with a wrapping of iodoform gauze (Fig. 8-2). 
Figure 8-2
Keetley’s fixator consisted of implanted pins connected by wire, then overwrapped with gauze.
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In 1897, Clayton Parkhill, a Denver surgeon and dean of the University of Colorado School of Medicine (1895 to 1897) reported on the results of nine patients treated with an external device similar to a modern simple monolateral four-pin external fixator. His first case was performed in 1894, and his device consisted of four screws, two of which were inserted into each fragment above and below the fracture. The ends of the screws were fixed together by interlocking plates and bolts. He did require supplemental plaster immobilization to provide additional support to the construct (Fig. 8-3). He treated eight nonunions and one unstable tibial shaft fracture. Union of the fractures occurred in eight of the nine patients.225,226 His career was unfortunately cut short when he died from appendicitis. Although himself a surgeon, he would not submit to surgery for his condition and died in Denver in 1902. 
Figure 8-3
Parkhill’s external fixator for tibia fractures.
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Leonard Freeman was a contemporary of Parkhill, as both were professors of surgery in the Medical Department of the University of Colorado. Freeman developed his own system of external fixation which he thought was much simpler than Parkhill’s device. Single pins were inserted above and below the fracture or nonunion and were connected to each other using an external metal band with wooden plate liners firmly clamping the pin shafts (Fig. 8-4A). He was the first to develop a system of instrumentation to insert the pins applied through very small incisions, and he carefully reviewed the technique of “clean” insertion using a trocar and drill sleeve to protect the soft tissues during predrilling of the fixation holes. He also utilized a “T handle” to carefully insert the pins into the bone. He recommended that the pins be inserted “at a distance from the fracture, perhaps in normal tissues, through small openings in the skin.” In spite of the fact that he continually praised Parkhill’s work, he felt that Parkhill’s clamp, and “others which have appeared abroad are unnecessarily complicated and difficult of application, owing to the various wings, nuts, and adjustments with which they are hampered. This apparatus described … is so simple that it can always rapidly and easily be inserted.”100104 He initially reported the treatment of a proximal femoral neck nonunion and two tibial nonunions with this technique (Fig. 8-4B).100 
Figure 8-4
 
A: Freeman’s fixator. B: Freeman device used to stabilize proximal femoral fractures and nonunions.
A: Freeman’s fixator. B: Freeman device used to stabilize proximal femoral fractures and nonunions.
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Figure 8-4
A: Freeman’s fixator. B: Freeman device used to stabilize proximal femoral fractures and nonunions.
A: Freeman’s fixator. B: Freeman device used to stabilize proximal femoral fractures and nonunions.
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The Belgian surgeon Lambotte recognized Parkhill’s work but was unable to obtain a copy of Parkhill’s paper. In 1902 he expanded external fixation further and was the first to apply a simple unilateral frame in a systematic fashion. He recognized that the metal pins which penetrated the bone and protruded through the skin were remarkably well tolerated and could be connected to an external clamp device, which would allow for stabilization of these pins and the bone fragments they were attached to (Fig. 8-5).172 Lambotte’s concepts and design evolved and eventually allowed for frame adjustments to occur including compression and distraction at the fracture site. 
Figure 8-5
Lambotte’s external fixator using simple pins and a clamp device.
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In Europe, Lambotte’s original concepts were expanded significantly and in 1938, Raul Hoffmann began tinkering with the external fixators of his era, whose shortcomings included the need for open reduction before fixator application. He developed his own technique for fracture fixation, which he termed “ostéotaxis,” a Greek term meaning “to put the bones in place.” Hoffmann was also a doctor of theology and a carpenter in his free time, and his external fixator incorporated a universal ball joint connecting the external ball of the fixator to strong pin-gripping clamps. This universal joint permitted fracture reduction to occur in three planes while the fixator was in place. Hoffman could substitute a sliding compression—distraction bar connecting the pin-gripping clamps, and then interfragmentary compression or limb length restoration could be performed (Fig. 8-6).134,135 In 1938, Hoffmann published his new technique and presented it to the French Congress of Surgery.247 
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Figure 8-6
Hoffman’s multipin clamp external fixator.
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In the United States, Roger Anderson devised an apparatus for the mechanical reduction of fractures utilizing transcutaneous pins connected to metal clamps. Anderson’s early concept called for application of transfixion pins. This permitted multiplanar adjustment of the fracture fragments and also allowed compression at the fracture site. Following reduction, a cast was applied whereas the limb was still held by the external device.7 After the cast was applied, the external device was removed and reused on additional patients. Later, Anderson extended this concept and designed an entire external system that connected transcutaneous pins to bars, eliminating the need for a plaster cast (Fig. 8-7).115 
Figure 8-7
Anderson device with through-and-through transfixion pins.
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In 1937, Otto Stader devised a system of fracture management for use in his veterinary practice, which permitted stabilization of fractures and also allowed the independent reduction of fracture fragments to occur in three planes.115,229 Stader’s work was observed by surgeons from Bellevue Hospital in New York. They persuaded him to adapt his fixator for use in humans and thus the Stader device was refined and enlarged for use in human long bones. In 1942, Lewis and Breidenbach reported their experience with this device for treating 20 patients with long bone fractures at Bellevue Hospital They were encouraged by the frame’s ability to achieve excellent alignment and early ambulation without the need for adjunctive casting. (Fig. 8-8).184 They were the first to describe the technique of placing pins as far from the fracture as possible and avoiding pins directly near the site of fracture. This was done to improve the fixator’s ability to gradually reduce a malaligned extremity by adjusting the device. They felt a wide pin spread increased the overall mechanical stability of the construct. They also were one of the first investigators along with Schanz, Riedel, and Anderson to point out the advantages of inserting the fixation pins at an angle to each other (not parallel) as a means of firmer control over the bone fragments.184,229 
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Figure 8-8
The Stader device.
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World War II Use of External Fixation

During World War II (WWII) there were initial favorable reports on the use of the Roger Anderson device in the European theatre where external fixation techniques were demonstrated at base hospitals. However, experience showed that the techniques were too specialized and time consuming for use in an active combat zone. Also, there was a high incidence of complications, including poor pin fixation, pin tract infection, and localized osteomyelitis. Indeed, the copious purulent drainage from the pin sites of Anderson device became so infamous that it was dubbed “Seattle serum,” after the city in which he worked.247 This technique fell into general disfavor because these complications were by and large attributed to the external fixation device and not necessarily to the problems of treating high-energy open fractures.120 This resulted in a directive issued to military surgeons of the United States Armed Forces to discontinue the use of external fixation in the European theatre of WWII conflict.115 
However, excellent results were reported by the United States Navy, utilizing external fixation techniques in the Pacific conflict. These were documented by Shaar and Kreuz in their monograph outlining their use and results of the Stader splint.266,267 They describe the use of this fixator for a wide variety of fractures including femur, tibia, humerus, forearm, and even facial and mandibular fractures. These procedures were primarily performed on evacuation hospital ships and away from the chaos of field hospitals. 
Similar results were documented by the Canadian Armored Corps with their use of the Stader device beginning in 1942. They felt that pretraining with cadaver application and familiarity of the device was a crucial factor in their excellent results. They also discussed pin insertion technique extensively to avoid heat generation and the development of ring sequestra.250 
In 1950, a study was commissioned by the Committee on Fracture and Trauma Surgery of the American Academy of Orthopaedic Surgeons (AAOS) to investigate the efficacy and indications for external fixation in clinical fracture management. The study was based on 3,082 questionnaires sent to practicing clinicians who were members of the AAOS, the American association for the surgery of trauma and the Iowa Medical Society. Only 395 replies were analyzed by the committee. In all, 28% of the respondents felt that external skeletal fixation had a definite place for fracture management, whereas 29.4% felt that external fixation was not inadvisable except in select rare instances.140 Over 43% of respondents had used external fixation at one time, but had abandoned it completely at the time of the survey. Based on the results of the survey and concerns that practitioners had with the potential mechanical difficulty associated with these frames, as well as the prospect of converting a closed fracture to an open fracture, the committee concluded that any physicians who contemplated the use of external skeletal fixation required special training under the supervision of a surgeon who had treated at least 200 cases by this method.115,271 As a consequence, by 1950, the majority of American surgeons were not using this modality. 

Contemporary Monolateral External Fixation Evolution

From 1950 to 1970, external fixators were generally unpopular with American orthopedists, although the “pins and plaster” technique was still widely used for wrist and tibial fractures. In Europe, Vidal and his coworkers were the first to subject the various external fixator frames to mechanical testing. Vidal utilized Hoffman’s equipment, but designed a quadrilateral frame to provide rigid stabilization of complex fracture problems. His biomechanical studies determined that the quadrilateral configuration was quite stable.115,287 
Similarly, Franz Bernie continued with Dr. Hoffman’s original concept of a unilateral frame utilizing a single connecting bar and half pins. His extensive clinical experience with a half-pin frame documented the success of this device when treating several large series of fractures.40,41 This European experience in the late 60s and early 70s demonstrated that the use of external fixation could not only treat fractures, but could also be extended to the treatment of pseudoarthrosis, infections, and arthrodeses. 
During the 70s, De Bastiani developed the “dynamic axial fixator” and Gotzen the “monofixator.” These were simple four-pin frames with large pin clusters positioned at either ends of the bone. These were then connected to each other by a large-diameter telescoping tubular rod (Fig. 8-9). This innovation allowed the frames to be more patient-friendly compared with the complex fixators of Vidal-Adrey. These frames would promote axial loading with full weight bearing, accentuating micromotion, and dynamization at the fracture site to enhance healing. 
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Figure 8-9
Large body monotube external fixator.
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The outstanding basic science work on external fixation and the promising clinical results emanating from Europe in the early 70s stimulated renewed interest in the use of these techniques in North America. This also coincided with the publication of the second edition of the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Manual in 1977.132 It was at this time that external fixation was recommended for the treatment of acute open fractures. Simultaneously, with the recommendations found in the second AO Manual was the production of a new tubular monolateral external fixation system. The tubular system of the Association for the Study of Internal Fixation (ASIF) gained wide acceptance very rapidly, because of improved pin design and frame biomechanics, as well as precise indications for their use. These factors contributed to many North American surgeons revisiting and adopting this technique, with good clinical results (Fig. 8-10). 
Figure 8-10
The “simple monolateral” multicomponent external fixation system that helped renew interest in contemporary external fixation techniques.
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External fixation has enjoyed a renaissance over the last 10 years with the adoption of damage control orthopedic (DCO) techniques and the concepts of temporary spanning external fixation for the treatment of complex periarticular injuries. These treatment methodologies emphasize the application of simplistic monolateral external fixators to facilitate the initial management of complex articular injuries, or long bone fractures in the polytraumatized patient.234 Minimalistic frames combined with delayed skeletal reconstruction using locking plates and IM nails have become the standard of care for most centers treating these patients. 

Circular External Fixation

The credit for establishing circular external fixation as a method for fracture reduction and limb lengthening has to be given to Joseph E. Bittner MD, a general surgeon from Yakima, Washington. He developed a system of circular rings with transfixion wires which were tensioned by expanding a hinged ring with the wire attached between the hinges. As the ring diameter was expanded, the tension increased in the wires (Fig. 8-11). He published his work in a German Science Journal in 1933 and patented his device 1 year later in 1934. This was followed by a plethora of Russian and European circular fixators initiated first by Pertsovsky in 1938, followed by other Russian surgeons including Gudushauri and Kalnberz. Their devices all resembled Bittner’s original concept of circular rings with tensioned wires.116,141 
Figure 8-11
 
A, B: The original patent application for Bittner’s circular external fixator with the principle of tensioned thin fixation wires.
A, B: The original patent application for Bittner’s circular external fixator with the principle of tensioned thin fixation wires.
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Figure 8-11
A, B: The original patent application for Bittner’s circular external fixator with the principle of tensioned thin fixation wires.
A, B: The original patent application for Bittner’s circular external fixator with the principle of tensioned thin fixation wires.
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External fixation as a modality for fracture treatment continued to remain viable in Russia following WWII. Instead of concentrating on half-pin and monolateral type configurations that were popular in the United States, their techniques continued to focus on the use of tensioned transfixion wires to maintain bone segment fixation. In 1948, Gavril Abramovich Ilizarov developed his version of a circular fixator, which permitted surgeons to stabilize bone fragments with distraction techniques and also made three-dimensional reconstructions possible. In 1950 Ilizarov moved to the city of Kurgan where he continued to explore ways to achieve improved results in bone healing and patented his device in 1954. By attaching these wires to separate rings, the rings could be individually manipulated to provide for three planes of correction, similar to the concepts pioneered by Hoffman, Bernie, Vidal, and Bittner. This ability to achieve precise ring positioning resulted in significant flexibility of the device (Fig. 8-12). Because of the success rate he reported for complex problems, devices similar to the Ilizarov circular frame began emerging in other areas of the USSR.141 Gudushauri device was a half ring (bow) designed at the Central Institute of Traumatology and Orthopedics (CITO) in 1955. Later, the Gudushauri device was given the green light and became the “official” external device used in Moscow for many years. In the mid 1960s the central power structure in Moscow did not want to credit a simple “province” doctor from Siberia (Ilizarov) with these revolutionary concepts.141 
Figure 8-12
 
A: Ilizarov’s circular fixators using small tensioned wires attached to individual rings. Note the pins wrapped with gauze to provide stabilization of the pin–skin interface. B: Radiographs demonstrating bilateral tibial lengthening using classic Ilizarov thin wire frames.
A: Ilizarov’s circular fixators using small tensioned wires attached to individual rings. Note the pins wrapped with gauze to provide stabilization of the pin–skin interface. B: Radiographs demonstrating bilateral tibial lengthening using classic Ilizarov thin wire frames.
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Figure 8-12
A: Ilizarov’s circular fixators using small tensioned wires attached to individual rings. Note the pins wrapped with gauze to provide stabilization of the pin–skin interface. B: Radiographs demonstrating bilateral tibial lengthening using classic Ilizarov thin wire frames.
A: Ilizarov’s circular fixators using small tensioned wires attached to individual rings. Note the pins wrapped with gauze to provide stabilization of the pin–skin interface. B: Radiographs demonstrating bilateral tibial lengthening using classic Ilizarov thin wire frames.
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Dr. Mstislav V. Volkoff, head of the CITO, was one of the prominent figures who actively worked against universal acceptance of the Ilizarov methodology in the USSR. Together with Dr. Oganesyan they patented a similar device and used their prestige to promote their device for many years.141 In 1975, Volkoff and Oganesyan published a series of patients treated with distraction arthroplasty at the knee and elbow utilizing small transfixion wires attached to ring fixators. Their work went largely unnoticed in North America even though it was published in the American Journal of Bone and Joint Surgery.290 
Dr. David Fisher was exposed to Volkoff’s circular apparatus and designed a circular type fixator of his own. Instead of using thin tensioned wires as with the Russian device, he designed a fixator construct which allowed for significant pin separation, deviation of pins at various angles, and a semicircular configuration using larger Schanz half pins. He determined that fracture site stability could be increased using these circular configuration concepts.94,115 
As the traditional Soviet Ilizarov type devices were quite cumbersome and complex compared with the more straightforward A/O and Hoffman type fixators, Kroner, in 1978, refined and modified the Russian devices by employing plastic components and transfixion pins in place of the thin wires used by the Ilizarov technique.1,115,140 
For many years, the Ilizarov method was restricted to the region of Kurgan in Siberia. In 1980, the technique was introduced in Western Europe thanks to the persistence of world famous Italian explorer, Carlo Mauri. Mauri traveled to Russia specifically for this technique, and was successfully treated for an infected psuedoarthrosis of the tibia by Ilizarov. His fracture had occurred 10 years earlier in a mountain climbing accident. Through the friendship established by Mauri with Professor Ilizarov, the technique was introduced to Mauri’s initial treating surgeons, and subsequently, Ilizarov was invited to speak at the XXII Italian AO conference in Bellagio, Italy. This was the first clinical presentation that Ilizarov gave on his techniques outside of the “Iron Curtain.” Italian surgeons realized the significance of his methods and brought the techniques back to Italy under the guidance of Professor Roberto Cattaneoto and his associates, Villa, Catagni, and Tentori. They began the first western clinical trials with transosseous osteosynthesis utilizing Ilizarov’s fixator in Lecco, Italy, in 1981.1,140,141 
When the political climate in the Soviet Union changed under different leadership in the 1980s, the possibilities of the Ilizarov method that had previously been unrecognized in the West became more apparent. These techniques were presented at various orthopedic meetings in Italy and other centers in Western Europe in the early 1980s.115,135,140,141 Victor H. Frankel (then president of the Hospital for Joint Diseases) saw the external device at a scientific exhibition while attending a meeting in Spain. He investigated further and eventually traveled to Kurgan to visit Ilizarov’s center along with Dr. Stuart Green MD in 1987. This began a progression of North American surgeons, notably Victor Frankel, James Aronson, Dror Paley, and Stewart Green, who were exposed to Ilizarov’s work. They recognized the potential of this methodology as applied to difficult contemporary orthopedic problems and all began clinical applications in the mid 1980s.140,141 In 1989, Stewart Green, who had significant expertise in treating nonunions and osteomyelitis with external fixation techniques, was entrusted by Ilizarov to translate his original basic science work into English. This was published in Clinical Orthopaedics and Related Research in 1989.1,138141 
The North American experience was popularized by a small cadre of American surgeons in the late 1980s. In an effort to simplify and apply these techniques to traumatology, the tensioned ring concept was married to the unilateral fixator, and the hybrid external fixator was developed to address periarticular injuries with all the advantages of tensioned wires, while limiting the disadvantages of tethering large musculotendinous units with through-and-through transfixion wire constructs. (Fig. 8-13).1,117 However, this “advancement” had a relatively short life span because of inferior biomechanics. 
Figure 8-13
 
A: An early version of a hybrid external fixator which combines periarticular tensioned wires and diaphyseal half-pin configurations. B: Clinical picture of the same hybrid frame on a patient with a tibial plateau fracture.
A: An early version of a hybrid external fixator which combines periarticular tensioned wires and diaphyseal half-pin configurations. B: Clinical picture of the same hybrid frame on a patient with a tibial plateau fracture.
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Figure 8-13
A: An early version of a hybrid external fixator which combines periarticular tensioned wires and diaphyseal half-pin configurations. B: Clinical picture of the same hybrid frame on a patient with a tibial plateau fracture.
A: An early version of a hybrid external fixator which combines periarticular tensioned wires and diaphyseal half-pin configurations. B: Clinical picture of the same hybrid frame on a patient with a tibial plateau fracture.
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A significant innovation in deformity correction and precise fracture reductions was developed by Charles Taylor and others to correct complex deformities through the use of simple ring constructs using half-pin fixation. These “hexapod” fixators have rings interconnected and manipulated by a system of adjustable struts, which allow for six-axis correction of bone fragments (Fig. 8-14).246,262,263 The development of this concept, as well as the ability to interface deformity correction with web-based software, has vastly simplified frame construction and is the basis for contemporary circular external fixation techniques in use at this time. 
Figure 8-14
Hexapod external fixator with multiple oblique connecting struts through which the limb segments can be manipulated for simultaneous correction of multiple deformities.
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Frame Types, Biomechanics, and Components

External fixation systems in current clinical use can be categorized according to the type of bone anchorage utilized. This is accomplished by using either large threaded pins, which are screwed into the bone or by drilling small-diameter transfixion wires through the bone and then placing the wires under tension to maintain bone fragment position. 
The pins or wires are then connected to one another through the use of longitudinal bars or circular rings. Thus the distinction is made between monolateral external fixation (longitudinal connecting bars) and circular external fixation (wires and/or pins connecting to rings). Circular fixation may use either threaded pins or small tensioned wires to attach the bone to the frame. Monolateral fixation is accomplished using various diameter threaded pins; however, these may occasionally involve the use of centrally threaded through-and-through transfixion pins. 

Large Pin Fixation

Large pin fixator constructs are attached to the bone using various sizes of terminally threaded pins. The half pins have a wide range of diameter ranging from 2 to 6 mm with all intermediate sizes available. In addition, there are large-diameter pins with threads in the midportion of the device (centrally threaded pins), for use in transfixion-type constructs, that is, Hoffman-Vidal configurations (Fig. 8-15A–E). 
Figure 8-15
 
A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
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A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
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Figure 8-15
A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
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A: Large centrally threaded Schanz pin placed as a distal femoral transfixion pin in a temporary knee-spanning external fixator as seen on radiographs. Clinical image of proximal transfixion pin and quadrilateral spanning frame with intercalary half pin mid tibia. B–E: Multiple pin types; (B) 5-mm self-tapping predrilled pins with a short thread length, (C) 5-mm self-tapping predrilled pin with long threads, (D) 6-mm hydroxyapatite self-drilling pin, note self-drilling tip, and (E) 6-mm self-tapping predrilled titanium pin. F–J: Multiple thread designs are used for specific purposes; (F) tapered pins facilitate subsequent pin removal, (G) self-drilling pins with drill-type pin tip; (H) pins with larger thread diameter suitable for cancellous bone insertion, (I) small pitch angle and narrow thread-diameter pins are applied in cortical bone, and (J) hydroxyapatite-coated pins improve the pin–bone interface by encouraging direct bone apposition and ingrowth.
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The basic indications for large pin external skeletal fixation are numerous. The actual biomechanical function that a monolateral frame will perform is dependent upon the placement of the pins and orientation of the connecting bars applied. These factors, as well the inherent skeletal pathology treated, combine to impart a specific biomechanical function to the fixation construct. The ability to neutralize deforming forces is the most common mechanical principle exploited by external fixation. This is especially true for acute fractures accompanied by severe soft tissue damage. The use of monolateral fixation for the stabilization of acute fractures deals with the soft tissue compromise in the immediate posttrauma/postoperative period.90 Following resolution of the soft tissue injury, secondary procedures such as bone grafting or delayed internal fixation are performed. The primary function of fixators used in this way is to provide relative stability to maintain temporary fracture reduction and length to avoid collapse of the fracture construct (Fig. 8-16). It should be noted, however, that this type of stabilization is reasonably “flexible.” It is nearly impossible to achieve absolute rigidity to achieve primary bone healing utilizing monolateral external fixation. 
This maintains the reduction but is not “rigid” and requires additional temporary splinting.
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Figure 8-16
Simple triangular ankle-“spanning” fixator across a distal tibial injury, with a transfixion pin through the calcaneal tuberosity and two midtibial half pins.
This maintains the reduction but is not “rigid” and requires additional temporary splinting.
This maintains the reduction but is not “rigid” and requires additional temporary splinting.
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Monolateral as well as circular frames can also be used to bring areas of metaphyseal or metadiaphyseal bone into close contact through the use of compression techniques. This may be useful in arthrodesis, osteotomy, or nonunion repair (Fig. 8-17).187,221 Similarly, distraction forces can also be applied across pin groups to effect deformity correction, intercalary bone transport, or limb lengthening. 
Figure 8-17
 
A: A simple “compression” monolateral system constructed to achieve arthrodesis of the knee. B: Complex ring external fixator to effect similar compression forces for an infected knee fusion below a pre-existing femoral nail. Solid arthrodesis was achieved following frame nail removal, debridement, and compression treatment.
A: A simple “compression” monolateral system constructed to achieve arthrodesis of the knee. B: Complex ring external fixator to effect similar compression forces for an infected knee fusion below a pre-existing femoral nail. Solid arthrodesis was achieved following frame nail removal, debridement, and compression treatment.
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Figure 8-17
A: A simple “compression” monolateral system constructed to achieve arthrodesis of the knee. B: Complex ring external fixator to effect similar compression forces for an infected knee fusion below a pre-existing femoral nail. Solid arthrodesis was achieved following frame nail removal, debridement, and compression treatment.
A: A simple “compression” monolateral system constructed to achieve arthrodesis of the knee. B: Complex ring external fixator to effect similar compression forces for an infected knee fusion below a pre-existing femoral nail. Solid arthrodesis was achieved following frame nail removal, debridement, and compression treatment.
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Components

No matter what the biomechanical function of the frame type, the most important factor regarding the longevity and performance of the frame is the strength and competency of the pin–bone interface. Pin loosening with subsequent pin sepsis continues to be problematic. There are many biomechanical factors, which have been evaluated for the prevention of pin tract problems.14,25,64,111,114,126 
  1.  
    Pin geometry and thread design
  2.  
    Pin biomaterials and biocompatibility
  3.  
    Pin insertion techniques and pin–bone interface mechanics

Pin Design

It has been determined that both the screw thread design and the type of cutting head have a significant effect on the holding power of screws. Screw diameter is crucial in determining the stiffness of the frame, as well as determining the risk of stress fracture at the pin site entry portal. The bending stiffness of the screw increases as a function of the pin’s radius raised to the fourth power (S = r4). Placing a screw hole greater than 20% or 30% of the bone’s diameter will substantially increase the risk for pinhole fracture. It is important to match the pin diameter to the diameter of the bone being stabilized. In general, it is recommended to err on the side of using a smaller pin diameter. 
Calculations have determined that in adult bone, a pin diameter of 6 mm is the maximum that can be used to achieve a stable implant without suffering the consequences of stress fracture through the pinhole itself.47,232,265 This risk will resolve in 6 to 8 weeks through bone remodeling once the pin has been removed. However, the pin site does remain a stress riser until full remodeling of the pin site can occur. 
In addition to the variable diameter of the pin, the screw thread may also have differing pitch angle and pitch height. The screw design must make allowances for the quality and location of the bone to which the screw is applied. Pins with a small pitch height and low pitch angle are usually applied in regions of dense cortical bone, such as femoral and tibial diaphysis (Fig. 8-15F–J). 
As the pitch vertex angle increases and the curvature and the diameter of the thread increases, the area captured by each individual thread is broader and more likely to be applied in cancellous bone rather than hard cortical bone. Conical pins have been designed so that the threads taper and increase in diameter from the tip of the pin to the shaft. This allows the pins to increase their purchase theoretically by cutting a new larger path in the bone with each advance of the pin. This conical taper also produces a gradual increase in radial preload and thus the screw–bone contact is optimized (Fig. 8-15F–J). Micromotion typical of a straight cylindrical screw is avoided.175,206,208 

Pin Biomaterials and Biocompatibility

Traditionally, external fixator pins have been composed of stainless steel offering substantial stiffness.151 Finite element analyses of the near pin–bone interface cortex revealed stress values which were significantly increased by the use of deep threads and by the use of stainless steel as opposed to titanium pins. Titanium has a much lower modulus of elasticity. However, because of the better biocompatibility afforded with titanium and titanium alloys, there are some investigators who prefer the lower pin–bone interface stresses, as well as the better biocompatibility when using titanium, as they feel there is a lower rate of pin sepsis. Titanium alloy half pins had greater recoverable deformation and less stress concentration at the pin–bone interface. Micro-CT analysis also indicated a larger and higher quality of newly formed bone at the pin–bone interface in titanium alloy group when compared with a pin with a titanium core and a vanadium surface coat (TAV). Histology demonstrated that the newly formed bone integrated well into the threads of titanium alloy half pins. In contrast, there was a layer of necrotic tissue between the bone tissue and the vanadium half pin at the pin–bone interface in the TAV group. The extraction torque values of the titanium alloy half pins near the fracture line were significantly higher than the TAV pins. It appears that pins with a low elastic modulus and excellent biocompatibility can enhance osseointegration and reduce pin loosening.322 
The perceived advantages of titanium in demonstrating excellent biocompatibility may be because of the oxide layer formed on titanium implants. Biocompatibility studies comparing the efficacy of pins coated with titanium dioxide (TiO2) for inhibition of infection was compared with that of stainless steel control pins in an in vivo study. The bone–implant contact ingrowth ratio of the TiO2-coated pin group was significantly higher (71.4%) than in the control pin group (58.2%). The TiO2 was successful in decreasing infection both clinically and histomorphometrically.161 
This improved performance may be because of many factors including an actual bone ingrowth phenomenon seen at the pin–bone interface.186,201,202,206 A prospective trial examined 80 patients (320 pins) with unstable distal radius fractures who were treated with external wrist fixators. The ex-fix pins were either stainless steel or titanium alloy. The rate of premature fixator removal because of severe pin tract infection (5% vs. 0%) and the rate of pin loosening (10% vs. 5%) were higher in the stainless steel pin group. The authors concluded that the use of titanium alloy external fixator pins in distal radial fractures may reduce pin-related complications and significantly reduce pain levels compared with the stainless steel pin fixators.232 
Among the many different techniques to enhance the pin–bone interface fixation, coating the pins with hydroxyapatite (HA) has been shown to be one of the most effective.20,43,202 
Moroni et al.205 demonstrated that HA-coated tapered pins improved the strength of fixation at the pin–bone interface, which corresponded to a lower rate of pin tract infection. The HA coating provides a significant increase in direct bone apposition with a decrease in the fibrous tissue interposition at the pin–bone interface. There is significantly less pin loosening in studies comparing HA-coated pins with other pin material groups.256 These advantages provided by HA coating appear to be more relevant clinically when these pins are used in cancellous bone rather than in cortical bone (Fig. 8-15B–E).43,203,204 In subsequent studies HA coating on fixator pins has been shown to be more important for optimal pin fixation than the particular combination of design parameters used in each pin type (i.e., thread pitch, thread configuration, tapered, etc.).200 

Pin Insertion Technique and Pin–Bone Interface Mechanics

Preloading the implant–bone interface has an effect on pin loosening. Radial preload is a concept that prestresses the pin–bone interface in a circumferential fashion rather than in just one direction.30,78 Fixator pins are placed with a slight mismatch in the greater thread diameter versus the core diameter of the pilot hole. The small mismatch increases insertion and removal torque, with a decrease in signs of clinical loosening. There is a point at which insertion of pins with a mismatch of greater than 0.4 mm can result in significant microscopic structural damage to the bone surrounding the pin. High degrees of radial preload or large pilot hole thread diameter mismatch will exceed the elastic limit of cortical bone, with subsequent stress fracture. Thus, the use of oversize pins producing excessive radial preloads must be questioned.30,105,149 
However, local bone yielding at the pin–bone interface of external fixation half pins has been known to initiate fixator loosening. Deterioration of bone properties because of aging and disease can lead to an increase in the risk of pin loosening. Finite element analysis has demonstrated that peri-implant bone resorption around pins increases three-fold comparing young with old-aged cases. The authors recommend fixator modifications when treating elderly patients such as the use of three, rather than two, half pins on either side of the fracture.75 
Additional recommendations include the use of small tensioned wire constructs in severely osteopenic individuals as a means to avoid pin–bone resorption and subsequent loosening. The volume of resorped bone at all wire–bone interfaces decreased with an increase in wire pre-tension. The absence of continuous cortical thickness resorption offers an explanation for the clinical observation that Ilizarov ring-wire fixation can provide stable fracture fixation even in a bone with high porosity.75,76 
Screw insertion technique also has an effect on the pin–bone interface. The pins typically come in two types, predrilled pins and self-drilling pins (Fig. 8-15B–E). Predrilled pins by their name require a drill to be used to produce a pilot hole prior to insertion of the pin. The pilot hole has a root diameter equal to or somewhat less than the core diameter of the pin itself.137,265 As a better pilot hole is drilled with a precise cutting tip, the radial preload is also effected, which will also effect the overall pullout strength. The advantages of predrilling using very sharp drills for pilot holes minimizes the risk of thermal necrosis and subsequent bone damage.78 The use of self-tapping cortical pins allows each thread to purchase bone as the pin is slowly advanced by hand (Fig. 8-15B–E).57,64 
Self-drilling pins have a drill tip point and are driven under power into the bone to engage the threads in cortical or cancellous bone. There is some concern that when using self-drilling pins, the near cortex thread purchase may be stripped as the drill tip of the pin engages the far cortex. As the drill tip on the pin spins to cut the far cortex, the newly purchased bone in the near threads is stripped and the pin stability compromised (Fig. 8-15F–J). Some studies indicate a 25% reduction in bone purchase of self-drilling, self-tapping pins compared with that of predrilled pins.22 This is also accompanied by a marked increase in the depth of insertion required to achieve a similar pin purchase or pin “feel,” when a self-drilling pin has a long sharp-tipped drilling portion adjacent to the actual threads.190 To have both cortices engaged with full threads, the pin must be advanced through the far cortex enough to capture the fully threaded portion of the pin and avoid the tapered drill tip. This may leave the tip of the pin “proud” for 2 to 3 mm, which may be problematic in certain anatomic areas where neurovascular structures are directly adjacent to the bone (Fig. 8-18). 
Figure 8-18
Pin insertion technique should include the evaluation of the far cortex–pin interface to determine the appropriate depth pin penetration.
 
Excessive penetration can result in potential neurovascular injury if self-drilling pins “pull” the pin too far to gain adequate thread purchase. These pins are placed correctly and do not protrude excessively beyond the far cortex.
Excessive penetration can result in potential neurovascular injury if self-drilling pins “pull” the pin too far to gain adequate thread purchase. These pins are placed correctly and do not protrude excessively beyond the far cortex.
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Figure 8-18
Pin insertion technique should include the evaluation of the far cortex–pin interface to determine the appropriate depth pin penetration.
Excessive penetration can result in potential neurovascular injury if self-drilling pins “pull” the pin too far to gain adequate thread purchase. These pins are placed correctly and do not protrude excessively beyond the far cortex.
Excessive penetration can result in potential neurovascular injury if self-drilling pins “pull” the pin too far to gain adequate thread purchase. These pins are placed correctly and do not protrude excessively beyond the far cortex.
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Reduction in the length of the drilling portion of the pin means that less of the pin tip needs to project through the far cortex before a firm grip is achieved on the bone. The flutes for tapping the bone run obliquely back down the shaft of the pin. The helical or spiral nature of the flutes steer the bone debris back along the pins and out into the soft tissue. The efficient removal of this bone is mandatory to avoid compacting and jamming the cutting flutes with bone debris and thus compromising their cutting ability, increasing the heat of insertion.105 
The potential disadvantages of self-drilling pins are increased heat of insertion, increased microfracture at both cortices (specifically at the near cortex with increased bone resorption), and subsequent decreased pullout strength with decreased insertion and extraction torque.57,206 Studies have noted elevations of temperature on heat of insertion with a direct drill technique, where temperatures in excess of 55°C can occur during insertion of self-drilling pins.193 Temperatures that exceed 50°C can result in cell death leading to an increased risk for pin site loosening. The use of a water-cooled sharp drill at lower torque speeds can decrease the risk of thermal necrosis.113,193 The complication of thermal necrosis with secondary loosening caused by the resorption of nonviable bone is a practical concern (Fig. 8-19). Clinically, however, an increased incidence of pin tract infection or other pin complications associated with the use of self-drilling pins has yet to be confirmed.264 
Figure 8-19
 
A, B: Distal tibial nonunion with varus deformity following failure of a hybrid external fixation. Self-drilling pins utilized in the diaphysis resulted in a ring sequestrum at the proximal pin site (black box). C: Sclerotic bone at prior pin location, with circumferential lucency characteristic of ring sequestrum. This complication required excision of the infected sequestrum.
A, B: Distal tibial nonunion with varus deformity following failure of a hybrid external fixation. Self-drilling pins utilized in the diaphysis resulted in a ring sequestrum at the proximal pin site (black box). C: Sclerotic bone at prior pin location, with circumferential lucency characteristic of ring sequestrum. This complication required excision of the infected sequestrum.
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Figure 8-19
A, B: Distal tibial nonunion with varus deformity following failure of a hybrid external fixation. Self-drilling pins utilized in the diaphysis resulted in a ring sequestrum at the proximal pin site (black box). C: Sclerotic bone at prior pin location, with circumferential lucency characteristic of ring sequestrum. This complication required excision of the infected sequestrum.
A, B: Distal tibial nonunion with varus deformity following failure of a hybrid external fixation. Self-drilling pins utilized in the diaphysis resulted in a ring sequestrum at the proximal pin site (black box). C: Sclerotic bone at prior pin location, with circumferential lucency characteristic of ring sequestrum. This complication required excision of the infected sequestrum.
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Monolateral Frame Types

Monolateral frames are subdivided into those fixators that come with individual separate components, that is, separate bars, attachable pin bar clamps, bar-to-bar clamps, and separate Schanz pins. These “simple monolateral” frames allow for a wide range of flexibility with “build-up” or “build-down” capabilities. These components are available with various diameter connection bars as well as multiple clamp sizes and pin clamp configurations. These are often available in “mini” configurations as well for the stabilization of smaller areas of involvement such as for the fingers, wrist, and hand, as well as foot and ankle involvement (Fig. 8-20). As noted above, pin diameters should be undersized especially when stabilizing lesser diameter bones (Fig. 8-21). This allows the surgeon to apply a frame specific to the clinical and biomechanical needs of the pathology addressed (Fig. 8-22). 
Figure 8-20
 
A: “Mini” monolateral frame used to span an ankle. B: 4-mm pins used to provide stabilization of the ankle to maintain neutral position. C: Mini fixator spanning into talar neck and calcaneous with mini connecting bars. D: Titanium 4-mm fixation pins at the time of frame removal; note excellent biocompatibility at pin–skin interface with the use of Ti pins.
A: “Mini” monolateral frame used to span an ankle. B: 4-mm pins used to provide stabilization of the ankle to maintain neutral position. C: Mini fixator spanning into talar neck and calcaneous with mini connecting bars. D: Titanium 4-mm fixation pins at the time of frame removal; note excellent biocompatibility at pin–skin interface with the use of Ti pins.
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Figure 8-20
A: “Mini” monolateral frame used to span an ankle. B: 4-mm pins used to provide stabilization of the ankle to maintain neutral position. C: Mini fixator spanning into talar neck and calcaneous with mini connecting bars. D: Titanium 4-mm fixation pins at the time of frame removal; note excellent biocompatibility at pin–skin interface with the use of Ti pins.
A: “Mini” monolateral frame used to span an ankle. B: 4-mm pins used to provide stabilization of the ankle to maintain neutral position. C: Mini fixator spanning into talar neck and calcaneous with mini connecting bars. D: Titanium 4-mm fixation pins at the time of frame removal; note excellent biocompatibility at pin–skin interface with the use of Ti pins.
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Figure 8-21
 
A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
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A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
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Figure 8-21
A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
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A: Small diameter humeral shaft, with fracture and arterial disruption. B–D: Fracture stabilized with mini fixator to allow for arterial repair. Diameter of pins used to match the small relative diameter of the humeral shaft. E: Following recovery of soft tissues and success of arterial repair, conversion of the fixator to a plate was carried out 7 days after initial injury with excellent healing.
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Figure 8-22
 
A, B: Two similar monolateral external fixators both used to span knee dislocations. Note similar components: Separate pin clamps and bars.
A, B: Two similar monolateral external fixators both used to span knee dislocations. Note similar components: Separate pin clamps and bars.
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Figure 8-22
A, B: Two similar monolateral external fixators both used to span knee dislocations. Note similar components: Separate pin clamps and bars.
A, B: Two similar monolateral external fixators both used to span knee dislocations. Note similar components: Separate pin clamps and bars.
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The other major category of monolateral frames is a more constrained type fixator which is supplied preassembled with a multi pin clamp at each end of a long rigid tubular body. The telescoping tube will allow for axial compression or distraction of this so-called “mono tube”-type fixator. “Simple monolateral fixators” have the distinct advantage of allowing individual pins to be placed at different angles and varying obliquities while still connecting to the bar. This is helpful when altering the pin position relative to the areas of soft tissue compromise. The advantage of the monotube-type fixator is its simplicity. Pin placement is predetermined by the multipin clamps. Loosening the universal articulations between the body and the clamps allows these frames to be easily manipulated to reduce a fracture. Similarly, compression (dynamization) or distraction can be accomplished by a simple adjustment of the monotube body (Fig. 8-9). 

“Simple” Monolateral Fixators

The stability of all monolateral fixators is based on the concept of a simple “four-pin frame.” Pin number, pin separation, and pin proximity to the fracture site, as well as bone–bar distance and the diameter of the pins and connecting bars, all influence the final mechanical stability of the external fixator frame (Fig. 8-23). 
Figure 8-23
Factors affecting the stability of monolateral external fixation include pin distance from fracture site, pin separation, bone–bar distance, connecting bar size and composition, pin diameter, pin number, and pin–bone interface.
A: Pin to center of rotation; (B) pin separation; (C) bone–bar distance.
A: Pin to center of rotation; (B) pin separation; (C) bone–bar distance.
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Most simple monolateral frames allow for individual placement of pins prior to the application of the connecting bars. This permits the surgeon to place pins out of the zone of compromised skin or away from the fracture hematoma. The versatility of contemporary pin/bar clamps have multiple degrees of freedom built into the clamp which allows a single bar to attach to all four clamps while still retaining the ability to reduce the fracture. The pins do not have to be placed in precise alignment as was required by earlier monolateral frame designs (Fig. 8-24). If aligned pin placement is contraindicated because of soft tissue or other concerns, the fractures can still be reduced by simply adding additional connecting bars and using the proximal and distal pin groupings as reduction handles. Once reduction is achieved, the bar-to-bar connecting clamp is tightened and reduction maintained (Fig. 8-25). 
Figure 8-24
 
A: The versatility of a monolateral frame is demonstrated. Pins can be positioned out of plane with respect to each other. B: A solitary connecting bar is able to connect to all pin–bar clamps. C: Reduction can be accomplished by manipulating each limb segment and then tightening the clamps to lock the reduction in place.
A: The versatility of a monolateral frame is demonstrated. Pins can be positioned out of plane with respect to each other. B: A solitary connecting bar is able to connect to all pin–bar clamps. C: Reduction can be accomplished by manipulating each limb segment and then tightening the clamps to lock the reduction in place.
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Figure 8-24
A: The versatility of a monolateral frame is demonstrated. Pins can be positioned out of plane with respect to each other. B: A solitary connecting bar is able to connect to all pin–bar clamps. C: Reduction can be accomplished by manipulating each limb segment and then tightening the clamps to lock the reduction in place.
A: The versatility of a monolateral frame is demonstrated. Pins can be positioned out of plane with respect to each other. B: A solitary connecting bar is able to connect to all pin–bar clamps. C: Reduction can be accomplished by manipulating each limb segment and then tightening the clamps to lock the reduction in place.
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Figure 8-25
 
A: A tibia fracture is grossly reduced and two pins each placed above and below the fracture. B: Each two-pin segment is connected with a single bar. The reduction is fine-adjusted and the two bars are connected to each other to lock in the reduction. C: Final postreduction x-ray demonstrating two pins in each limb segment. D: Four-pin monofixator with pins out of plane to each other. E: Temporary reduction with four-pin frame.
A: A tibia fracture is grossly reduced and two pins each placed above and below the fracture. B: Each two-pin segment is connected with a single bar. The reduction is fine-adjusted and the two bars are connected to each other to lock in the reduction. C: Final postreduction x-ray demonstrating two pins in each limb segment. D: Four-pin monofixator with pins out of plane to each other. E: Temporary reduction with four-pin frame.
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Figure 8-25
A: A tibia fracture is grossly reduced and two pins each placed above and below the fracture. B: Each two-pin segment is connected with a single bar. The reduction is fine-adjusted and the two bars are connected to each other to lock in the reduction. C: Final postreduction x-ray demonstrating two pins in each limb segment. D: Four-pin monofixator with pins out of plane to each other. E: Temporary reduction with four-pin frame.
A: A tibia fracture is grossly reduced and two pins each placed above and below the fracture. B: Each two-pin segment is connected with a single bar. The reduction is fine-adjusted and the two bars are connected to each other to lock in the reduction. C: Final postreduction x-ray demonstrating two pins in each limb segment. D: Four-pin monofixator with pins out of plane to each other. E: Temporary reduction with four-pin frame.
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Simple four-pin system rigidity can be increased by maximizing pin separation distance on each side of the fracture site as well as the number of pins used. In the case of a four-pin system, two pins on each limb segment with maximal pin spread, and minimizing the bone-connecting bar distance also increases stability (Fig. 8-23).215,216 Behrens demonstrated that unilateral configurations with stiffness characteristics similar to those of the most rigid two-plane constructs are easily built using the “four-pin frame” as a basic building block (Figs. 8-23 and 8-24).2527 Mechanically, most effective were the “delta” plane configurations, when two simple four-pin fixators are applied at 90-degree angles to each other and connected (Fig. 8-26). However, single and double stacked bar anterior four-pin frames have the best combination of clinical and mechanical features (Fig. 8-27). 
Figure 8-26
 
A: A delta configuration is composed of two “simple” four-pin frames connected at 90 degrees to each other. B: Clinical examination of severe crush injury to tibia with soft tissue compromise. C: Fracture stabilized with modified delta configuration with two out-of-plane half pins on either side of the fracture and two connecting bars. Note soft tissue recovery afforded by the external fixator.
A: A delta configuration is composed of two “simple” four-pin frames connected at 90 degrees to each other. B: Clinical examination of severe crush injury to tibia with soft tissue compromise. C: Fracture stabilized with modified delta configuration with two out-of-plane half pins on either side of the fracture and two connecting bars. Note soft tissue recovery afforded by the external fixator.
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Figure 8-26
A: A delta configuration is composed of two “simple” four-pin frames connected at 90 degrees to each other. B: Clinical examination of severe crush injury to tibia with soft tissue compromise. C: Fracture stabilized with modified delta configuration with two out-of-plane half pins on either side of the fracture and two connecting bars. Note soft tissue recovery afforded by the external fixator.
A: A delta configuration is composed of two “simple” four-pin frames connected at 90 degrees to each other. B: Clinical examination of severe crush injury to tibia with soft tissue compromise. C: Fracture stabilized with modified delta configuration with two out-of-plane half pins on either side of the fracture and two connecting bars. Note soft tissue recovery afforded by the external fixator.
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Figure 8-27
 
A: Stability of a “simple” four-pin frame can be increased by adding a second connecting bar. A “double-stacked” frame. B: The bone-connecting bar distance was increased to avoid soft tissue impingement on the bars. Because of the increased distance to the bone an additional connecting bar was added to increase the stability of the frame. C: Reduction maintained with “simple” four-pin double stack frame. Early consolidation is noted in this comminuted open fracture. D: Infected femur fracture with severe soft tissue injury and bone loss required additional pins (six) and a double stack frame to achieve the stability necessary to treat this injury.
A: Stability of a “simple” four-pin frame can be increased by adding a second connecting bar. A “double-stacked” frame. B: The bone-connecting bar distance was increased to avoid soft tissue impingement on the bars. Because of the increased distance to the bone an additional connecting bar was added to increase the stability of the frame. C: Reduction maintained with “simple” four-pin double stack frame. Early consolidation is noted in this comminuted open fracture. D: Infected femur fracture with severe soft tissue injury and bone loss required additional pins (six) and a double stack frame to achieve the stability necessary to treat this injury.
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Figure 8-27
A: Stability of a “simple” four-pin frame can be increased by adding a second connecting bar. A “double-stacked” frame. B: The bone-connecting bar distance was increased to avoid soft tissue impingement on the bars. Because of the increased distance to the bone an additional connecting bar was added to increase the stability of the frame. C: Reduction maintained with “simple” four-pin double stack frame. Early consolidation is noted in this comminuted open fracture. D: Infected femur fracture with severe soft tissue injury and bone loss required additional pins (six) and a double stack frame to achieve the stability necessary to treat this injury.
A: Stability of a “simple” four-pin frame can be increased by adding a second connecting bar. A “double-stacked” frame. B: The bone-connecting bar distance was increased to avoid soft tissue impingement on the bars. Because of the increased distance to the bone an additional connecting bar was added to increase the stability of the frame. C: Reduction maintained with “simple” four-pin double stack frame. Early consolidation is noted in this comminuted open fracture. D: Infected femur fracture with severe soft tissue injury and bone loss required additional pins (six) and a double stack frame to achieve the stability necessary to treat this injury.
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The complex delta frames allow for gradual frame removal on a rational basis to slowly transfer more load to the bone. This stepwise frame reduction leads from the most rigid unilateral constructs to frames that allow the most complete force transmission across the fracture site while still providing adequate protection against sagittal bending movements.2527 Studies have shown that a unilateral biplanar delta frame without transfixion pins have an overall rigidity equal to a bilateral transfixion-type device.280 
When the connecting bar to bone distance increases, implant stability decreases. This is clinically significant when dealing with patients who present with wide areas of soft tissue compromise, which may preclude the ability to place the connecting bar close to the subcutaneous border of the bone. To counteract this, a standard four-pin fixator should be augmented by increasing the number of pins applied in each fracture segment (Fig. 8-27).36 
The materials that the connecting bars are constructed of have a significant effect on overall frame stability. Kowalski et al.162 demonstrated that carbon fiber bars were approximately 15% stiffer than stainless steel tubes, and that an external fixator with carbon fiber bars achieved 85% of the fixation stiffness compared with that achieved with stainless steel tubes. They felt that the loss of stiffness of the carbon fiber construct was likely because of the clamps being less effective in connecting the carbon fiber rods to the pins. 
The weakest part of the system is the junction between the fixator body and the clamp or between the fixator clamp and the Schanz pins. Insufficient holding strength on a pin by a clamp may result in a decrease in the overall fixation rigidity, as well as increased motion and cortical bone reaction at the pin–bone interface.11 Cyclic loading of external fixators has been shown to loosen the tightened screws in the pin clamps. Thus, one needs to be aware of the mechanical yield characteristics of the clamps, bars, and pins throughout the course of treatment.79 
Because of the gradual fatigue of components and loosening of pin-to-bar and bar-to-bar connections, the clinical practice of regular tightening of the device during the course of treatment should be routine.79,126,313 

Monotube Fixators

Stability of the large monotube fixators is obtained in a distinctly different way compared with that of simpler monolateral fixators. Most monotube fixators have a fixed location for their pins mounted in pin clusters. These are connected to the body and thus the ability to vary pin location is substantially less when compared with simple monolateral fixators. Because the pin clusters are fixed at either end of the monotube body, the ability to maximize pin spread in relation to the fracture site is limited by the monotype body’s length. There is little variability to lower the large monotube connection bar closer to the bone in an effort to increase stability. These frames are very stable and accomplish their inherent rigidity by having a large-diameter monotube connecting body, which are typically three to four times the diameter of the simpler monolateral connecting bars. Because of the large body configuration, these devices offer higher bending stiffness, as well as equal torsional stiffness and variable axial stiffness when compared with standard Hoffman-Vidal quadrilateral frames with transfixion pins (Fig. 8-28).36,51,131,145,147 
Figure 8-28
Large-pin “monotube” fixator.
 
Device has fixed proximal and distal pin clamps and a large telescoping body.
Device has fixed proximal and distal pin clamps and a large telescoping body.
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Figure 8-28
Large-pin “monotube” fixator.
Device has fixed proximal and distal pin clamps and a large telescoping body.
Device has fixed proximal and distal pin clamps and a large telescoping body.
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These frames have ball joints at either end connecting the large fixator bodies to their respective pin clamp configurations. There has been concern about the ability to achieve stability because of the ball locking mechanism. Chao determined that the ball joint locking cam and fixation screw clamp required periodic tightening during clinical application to prevent loss of frame stiffness under repetitive loading. However, frank clinical failure with these types of ball joint devices has not been demonstrated.12,51,131 
In an attempt to provide the convenience of a multipin clamp, most monolateral manufacturers now provide a large clamp which can accommodate four to six Schanz pins applied directly through the clamp as a template. These clamps are then connected to the separate monolateral bars and other modular components. These frames attempt to combine the ease of pin insertion with excellent biomechanics. However, the exact mechanical performance of these frames has not been ascertained (Fig. 8-29).219 
Figure 8-29
 
A: Monolateral ankle-spanning frame demonstrating a multipin clamp proximally, and mini fixator components at the foot. B: Polytrauma patient with double stack femoral frame for more stability. Ankle-spanning frame with proximal multipin clamp, mini fixator components spanning ankle and a “delta”-like configuration of connecting bars on tibial component.
A: Monolateral ankle-spanning frame demonstrating a multipin clamp proximally, and mini fixator components at the foot. B: Polytrauma patient with double stack femoral frame for more stability. Ankle-spanning frame with proximal multipin clamp, mini fixator components spanning ankle and a “delta”-like configuration of connecting bars on tibial component.
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Figure 8-29
A: Monolateral ankle-spanning frame demonstrating a multipin clamp proximally, and mini fixator components at the foot. B: Polytrauma patient with double stack femoral frame for more stability. Ankle-spanning frame with proximal multipin clamp, mini fixator components spanning ankle and a “delta”-like configuration of connecting bars on tibial component.
A: Monolateral ankle-spanning frame demonstrating a multipin clamp proximally, and mini fixator components at the foot. B: Polytrauma patient with double stack femoral frame for more stability. Ankle-spanning frame with proximal multipin clamp, mini fixator components spanning ankle and a “delta”-like configuration of connecting bars on tibial component.
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Insufficient holding strength on a pin within a constrained pin clamp may result in the diminution of the overall construct rigidity, as well as pin movement at the pin–bone interface. This is a distinct disadvantage compared with the single component simple monolateral frames where each pin has its own pin–bone clamp.12 When using monotube fixators the use of six pins increased torsional rigidity, but the configuration failed at lower bending loads when compared with the four-pin configuration, reflecting the uneven holding strength of the pin clamp on three pins.12 

Monolateral Pin Orientation and Frame Stability

The rigidity of a half-pin system is maximal in the plane of the pins and is minimal at right angles to this plane. Thus, a simple four-pin frame placed along the anterior border of the tibia will resist the anterior and posterior forces generated with normal stride, whereas this frame is weakest in mediolateral bending.280,283,310 This demonstrates the biomechanical advantages of adding an additional two to four pins perpendicular (90 degrees) to the anterior pins (Figs. 8-25 and 8-26). 
Stability is also improved when the pins are placed in a nonorthogonal position (i.e., not at 90 degrees to the long axis of the tibia).316 If half the pins are oriented out of plane in relation to the remaining pins, this decreases the overall strength of the construct in the primary plane of the pins; however, this would be compensated for by increasing the strength of the construct in the plane at right angles.26,27,268 Thus, overall frame rigidity would be improved. 
Shear and Eagan demonstrated that a system in which the pins were placed at 60 degrees to each other offered substantial advantages. This increase in torsional rigidity is maintained to 30 degrees of pin divergence angle, after which torsional stability rapidly decreases. With only a 10-degree separation between the pin angles, displacement and response to torsional stress was reduced by 97%. The effects on compressive forces are much less. When fixator pins are spread out, the fixator was 91% stronger for resisting angular displacements and torsion compared with the traditional monolateral orientation.268 However, preferable to merely reducing rigidity in all planes is the production of a frame which more closely mimics the biomechanics of normal bone. An external fixator which allows an offset pin angle of 60 degrees demonstrates the ability to equalize forces in the sagittal and coronal planes, providing mechanical stimuli much closer to those normally encountered in the sagittal and coronal planes (Fig. 8-30).52,198,215,216,260,268 
Figure 8-30
Frames with nonlinear pin placement neutralize forces similar to the normal forces developed in a tibia.
 
This frame demonstrates pins out of plane to each other in the transverse and sagittal orientations. Six-millimeter HA-coated pins were utilized which gives this simple frame very stable mechanics requiring only three pins on each side of the fracture line.
This frame demonstrates pins out of plane to each other in the transverse and sagittal orientations. Six-millimeter HA-coated pins were utilized which gives this simple frame very stable mechanics requiring only three pins on each side of the fracture line.
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Figure 8-30
Frames with nonlinear pin placement neutralize forces similar to the normal forces developed in a tibia.
This frame demonstrates pins out of plane to each other in the transverse and sagittal orientations. Six-millimeter HA-coated pins were utilized which gives this simple frame very stable mechanics requiring only three pins on each side of the fracture line.
This frame demonstrates pins out of plane to each other in the transverse and sagittal orientations. Six-millimeter HA-coated pins were utilized which gives this simple frame very stable mechanics requiring only three pins on each side of the fracture line.
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Many investigators are currently examining alternative pin placement as a way to achieve maximal fracture stability with relative frame simplicity.26,27,198,280,283,310 A simplified two-ring circular frame utilizing three 6-mm half pins has been shown to increase circular frame stability compared with more complex ring constructs. The pins for these simple frames were applied at divergent angles of at least 60 degrees to the perpendicular. These divergent 6-mm half-pin frames demonstrated similar mechanical performance compared with standardized multiple tensioned wire and 5-mm half-pin frames in terms of axial micromotion and angular deflection.177 
A recent study evaluated the stiffness characteristics of a simple Taylor Spatial Frame (TSF) fixed with 1.8-mm transverse wires or HA-coated 6.5-mm half pins in 45-, 60-, 75-, and 90-degree divergence angles. There was an increase in axial and torsional stiffness with the increase in the divergence angle between the wires or pins (p < 0.05). The simple half pins provide greater stiffness to TSF frames and allowed for axial micromotion as well.159 Thus the clinical decision making regarding the use of tensioned transverse wires in comparison to half pins when using a circular fixator can be based on soft tissue or boney constraints without fear of inferior biomechanics with half-pin frames. 
Based on the available evidence, the mechanical performance of these simplified divergent half-pin frames are equivalent, if not superior, to the traditional transfixion wire frames. Surgeons can now reliably improve frame stability by simply placing pins out of plane to the long axis of the bone (Fig. 8-31). 
Figure 8-31
 
A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
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A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
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Figure 8-31
A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
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A: Oblique (out of plane) pin testing construct, which confirms oblique orientation of pins, allows for fewer pins to be used with no decrease in relative fixator stability. B, C: “Simple” construct with only 3- to 6-mm pins above and below the nonunion. All pins were placed out of plane to each other to affect larger pin spread and confer increased stability.
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Frame stability is most problematic when treating highly comminuted fractures or in fractures with significant fracture obliquity and increased shear stresses. Standard half pin application with pins placed perpendicular to the long axis of the bone fails to oppose the shear force vector directly, because the pins are placed oblique to the shear force vector, and thus do not neutralize the cantilever forces induced by this standard pin insertion angle. 
When half pins are placed parallel to the fracture line, they are known as steerage pins. Steerage pins placed parallel to the fracture line are thus in direct opposition to the shear force vector. The shear force is actively converted into a dynamic compressive moment directed at to the edge of the fracture fragments. (Fig. 8-32). In this way, compression is dependent on axial load, and the shear phenomenon is dramatically reduced, thereby yielding nearly zero shear. For fracture obliquities less than or equal to 30 degrees, there is inherent stability such that standard modes of fixation can be utilized without undue concern.132,185,316 However, at fracture obliquities greater than 30 degreesi nherent shear is present at the fracture ends with axial loading. Added steps should therefore be considered to help minimize this shear component, such as the application of the steerage pin concept. At fracture obliquities greater than 60 degrees, shear is a dominating force and one must be aware that even with steerage pins (pins placed parallel to the fracture lines), the forces may be extreme. Frames should be modified to perform strictly as a neutralization device as interfragmentary compression will be difficult to achieve even with the most complex devices (Fig. 8-32).132 
Figure 8-32
Steerage pin experimental set up demonstrating pins placed parallel to the major fracture line, dramatically reducing the shear forces and accentuating compressive forces with axial weight bearing.
(Courtesy of David Lowenberg MD.)
(Courtesy of David Lowenberg MD.)
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An alternative method of monolateral external fixation has developed using anatomically-contoured metaphyseal locking compression plates as external fixators (Fig. 8-33). The locking plates are applied outside the soft tissue envelope following closed reduction. The plates function as external monolateral connecting bars, and the locking screws secure the bone to the external plate. The locking compression plates function well as external fixators, given their angular stable screw fixation, much like Schanz pins, which are also locked into their connecting clamps. In a series of seven patients for acute or posttraumatic problems of the tibia (“supercutaneous plating”) locking compression plate (LCP) external fixators facilitated mobilization and were more manageable and aesthetically acceptable than traditional bar-Schanz pin fixators.160,286,312 The locking plates were applied outside the soft tissue envelope following closed reduction. The locking compression plates functioned well as external fixators, given their angular stable screw fixation. 
Figure 8-33
 
A: Comminuted, closed proximal tibial fracture with significant soft tissue concerns which precluded internal fixation. B, C: Use of proximal tibial locking plate as an external fixator. D: Plate (fixator) stabilizing comminuted fracture.
A: Comminuted, closed proximal tibial fracture with significant soft tissue concerns which precluded internal fixation. B, C: Use of proximal tibial locking plate as an external fixator. D: Plate (fixator) stabilizing comminuted fracture.
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Figure 8-33
A: Comminuted, closed proximal tibial fracture with significant soft tissue concerns which precluded internal fixation. B, C: Use of proximal tibial locking plate as an external fixator. D: Plate (fixator) stabilizing comminuted fracture.
A: Comminuted, closed proximal tibial fracture with significant soft tissue concerns which precluded internal fixation. B, C: Use of proximal tibial locking plate as an external fixator. D: Plate (fixator) stabilizing comminuted fracture.
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Small Wire Circular Frame Fixation

A major advantage of a monolateral system is that it can be applied in a uniplanar fashion minimizing the transfixion of soft tissues. The ring-type systems have the disadvantage of transfixion-type wires tethering soft tissues, as the wires pass from one side of the limb to the other.115,140 Because of the smaller wire diameter, soft tissue trauma, bony reaction, and intolerance to the wires are minimized. Large-pin monolateral fixators rely on stiff pins for frame stability. Upon loading, these pins act as cantilevers and do produce eccentric loading characteristics. Shear forces are regarded to be inhibitory to fracture healing and bone formation, which may be accentuated with certain types of monolateral half pin stabilization, especially when the pins are aligned.10,11,13,19,50,224,314 Circular or semicircular fixators allow for multiple planes of fixation which minimizes the harmful effects of cantilever loading and shear forces, while accentuating axial micromotion and dynamization.94,185,194,216,233,310,311 

Components

Ring fixators are built with longitudinal connecting rods and rings to which the small-diameter tensioned wires are attached. Alternatively, the bone fragments may be attached to the rings by half pins. The connecting rods may incorporate universal joints, which give these frames their ability to produce gradual multiplanar angular and axial adjustments. 
There are several component-related factors which can be manipulated to increase the stability of the ring fixation construct. 
  1.  
    Increase wire diameter
  2.  
    Increase wire tension
  3.  
    Increase pin-crossing angle to approach 90 degrees
  4.  
    Decrease ring size (distance of ring to bone)
  5.  
    Increase number of wires
  6.  
    Use of olive wires/drop wires
  7.  
    Close ring position to either side of the fracture (pathology) site
  8.  
    Centering bone in the middle of the ring

Wires

Thin, smooth wires of 1.5, 1.8, and 2 mm are the most basic component used in a circular small wire fixator (Fig. 8-34A). Wire strength and stiffness increases as the square of the diameter of the wire (S = d2). As these wires are tensioned, they provide increased stability. This occurs by increasing wire stiffness which simultaneously decreases the axial excursion of the wires during loading. The amount of tension in the wires directly affects the stiffness of the frame. Compression and bending resistance increases as a function of wire tension as it is gradually increased up to 130 kg. Beyond this threshold, further wire tensioning is difficult to accomplish because commercially available wire tensioning devices are unable to stop the slippage of the wire in the device as the wire is tensioned.16,245 
Figure 8-34
 
A: Smooth and beaded (olive) wires come in the common sizes of 1.5-, 1.8-, and 2-mm diameters. B: A wire tensioning device used to increase the overall rigidity of the frame construct. C: Multiple ring diameters are available to match the diameter of the applied extremity. Too large a ring increases the distance from bone to ring and thus makes the frame less rigid.
A: Smooth and beaded (olive) wires come in the common sizes of 1.5-, 1.8-, and 2-mm diameters. B: A wire tensioning device used to increase the overall rigidity of the frame construct. C: Multiple ring diameters are available to match the diameter of the applied extremity. Too large a ring increases the distance from bone to ring and thus makes the frame less rigid.
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Figure 8-34
A: Smooth and beaded (olive) wires come in the common sizes of 1.5-, 1.8-, and 2-mm diameters. B: A wire tensioning device used to increase the overall rigidity of the frame construct. C: Multiple ring diameters are available to match the diameter of the applied extremity. Too large a ring increases the distance from bone to ring and thus makes the frame less rigid.
A: Smooth and beaded (olive) wires come in the common sizes of 1.5-, 1.8-, and 2-mm diameters. B: A wire tensioning device used to increase the overall rigidity of the frame construct. C: Multiple ring diameters are available to match the diameter of the applied extremity. Too large a ring increases the distance from bone to ring and thus makes the frame less rigid.
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Beaded wires (olive wires) perform many specialized functions. During insertion the beaded portion of the wire is juxtaposed onto the cortex. As the far side of the wire is tensioned, the bead is compressed into the near cortex. This allows olive wires to be inserted to perform interfragmentary compression, which may be useful in fracture applications (Fig. 8-35). These wires act as a source of additional transverse force to correct deformity in malunions or nonunions and provide additional support to a limb segment that a smooth wire cannot achieve.140 
Figure 8-35
 
A: Fracture extending over distal one-third of tibia with large medial butterfly fragment is an ideal indication for a small-wire fixator. B: Olive wires were used as a “lag screw” to achieve additional stability of the medial butterfly fragment and distally in the metaphyseal region.
A: Fracture extending over distal one-third of tibia with large medial butterfly fragment is an ideal indication for a small-wire fixator. B: Olive wires were used as a “lag screw” to achieve additional stability of the medial butterfly fragment and distally in the metaphyseal region.
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Figure 8-35
A: Fracture extending over distal one-third of tibia with large medial butterfly fragment is an ideal indication for a small-wire fixator. B: Olive wires were used as a “lag screw” to achieve additional stability of the medial butterfly fragment and distally in the metaphyseal region.
A: Fracture extending over distal one-third of tibia with large medial butterfly fragment is an ideal indication for a small-wire fixator. B: Olive wires were used as a “lag screw” to achieve additional stability of the medial butterfly fragment and distally in the metaphyseal region.
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Wire Tension

During limb lengthening, tension in the wire will inherently be generated from the soft tissue forces achieved through distraction. This may generate tension in the wire up to as much as 50 kg. If the patient is weight bearing, and the limb is loaded, then further wire deflection (tension) occurs. This generates additional tension in the wire. Additional rigidity of the entire construct is also demonstrated (the so called “self-stiffening effect of tensioned wires”). If the wire was initially tensioned to 130 kg and additional tension is added through lengthening and weight bearing, then the yield point of the wire may be approached with possible wire breakage occurring (Fig. 8-34B). A fracture frame is essentially a static fixator where additional wire tension will only occur through weight bearing. Thus the degree of initial wire tension should take into account the pathology being treated and the treatment forces being generated.15,44,45,59 

Ring Diameter

The diameter of the ring also affects the stiffness of frame; as the diameter of the ring increases so does the distance of the ring to the bone, similar to the bone–bar distance described for half-pin monolateral fixators (Fig. 8-34C). Stability decreases as this distance increases. Ring diameter and wire tension have a dramatic effect on overall frame stability. As ring diameter increases, the effect of increasing wire tension on gap stiffness and gap displacement is also decreased. Decreased ring diameter has a greater affect on all variables compared with simply increasing wire tension. Although the effect of wire tension decreases as ring diameter increases, tensioning wires on frames with larger ring constructs is important because these constructs are inherently less stiff because of longer wires.15,42,44,45,59 

Wire Orientation

Wires placed parallel to each other, and parallel to the applied forces, provide little resistance to deformation. The bone can slide along this axis much like a central axle in a wheel. In bending stresses, the frames are much less rigid because of bowing of the transverse wires and slippage of the bone along these wires. The most stable configuration occurs when two wires intersect at 90 degrees. The bending stiffness in the plane of the wire is decreased by a factor of two as the angles between the wires converge from 90 to 45 degrees (Fig. 8-36). Therefore, changing pin orientation to a less acute angle decreases the stiffness in anterior posterior (AP) bending, but has a lesser effect on lateral bending, torsion, and axial compression.44,45,97,218 
Figure 8-36
 
A: Wire-crossing angle of 90 degrees provides the most stable configuration with small mediolateral translations and a rigid frame. B: A wire convergence angle of 45 to 60 degrees allows acceptable amounts of translations to occur with satisfactory frame stability. C: As the convergence angle decreases, the translation increases dramatically to the point where the bone slides along a single axis. Parallel wires produce a grossly unstable frame configuration.
A: Wire-crossing angle of 90 degrees provides the most stable configuration with small mediolateral translations and a rigid frame. B: A wire convergence angle of 45 to 60 degrees allows acceptable amounts of translations to occur with satisfactory frame stability. C: As the convergence angle decreases, the translation increases dramatically to the point where the bone slides along a single axis. Parallel wires produce a grossly unstable frame configuration.
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Figure 8-36
A: Wire-crossing angle of 90 degrees provides the most stable configuration with small mediolateral translations and a rigid frame. B: A wire convergence angle of 45 to 60 degrees allows acceptable amounts of translations to occur with satisfactory frame stability. C: As the convergence angle decreases, the translation increases dramatically to the point where the bone slides along a single axis. Parallel wires produce a grossly unstable frame configuration.
A: Wire-crossing angle of 90 degrees provides the most stable configuration with small mediolateral translations and a rigid frame. B: A wire convergence angle of 45 to 60 degrees allows acceptable amounts of translations to occur with satisfactory frame stability. C: As the convergence angle decreases, the translation increases dramatically to the point where the bone slides along a single axis. Parallel wires produce a grossly unstable frame configuration.
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Clinically, a wire divergence angle of at least 60 degrees should be attempted. Because this is not always possible because of anatomic constraints of passing transfixion wires, the use of olive wires or the addition of a wire at a distance from the primary ring (drop wires) significantly improves bending stiffness. The use of olive wires placed at the same level but from opposite directions improves resistance to shear forces by “locking” in the segment (Fig. 8-35).44,45,97,119,140,233,300,301,305 

Limb Positioning in the Ring

The location of the tibial bone in the limb is actually eccentric in nature compared with the humerus or the femur. This is important when placing the rings around the particular extremity. The center of the ring applied may not be located over the actual center of the bone. It may be positioned eccentrically with respect to the ring, affecting the overall stiffness of the frame. If the bone is located off center, this position provides greater stiffness to loading in axial compression, compared with a construct where the center of the ring is positioned exactly over the center of the bone. This center/center configuration demonstrates lowered axial stiffness at the fracture site during axial loading.15,42,44,45,47,86,218 Clinically, since tibial frames are most common, this is usually not an issue because the bone is routinely eccentric in the ring as long as the ring is centered on the leg itself. The eccentric location of the muscular compartments ensures this offset bone position. To place a frame on a tibia with the center/center orientation, a very large ring would be needed. This would vastly increase the ring–bone distance and further decrease the frame stiffness (Fig. 8-37). 
Figure 8-37
 
A: Eccentric bone location in the ring, simulating a tibial mounting. B: Center/center location of bone in the ring mounting simulating a femoral or humeral mounting. C: Central position of tibia in too small of a ring, results in posterior soft tissue impingement. A larger ring should have been used to center the bone within the ring and avoid soft tissue concerns.
A: Eccentric bone location in the ring, simulating a tibial mounting. B: Center/center location of bone in the ring mounting simulating a femoral or humeral mounting. C: Central position of tibia in too small of a ring, results in posterior soft tissue impingement. A larger ring should have been used to center the bone within the ring and avoid soft tissue concerns.
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Figure 8-37
A: Eccentric bone location in the ring, simulating a tibial mounting. B: Center/center location of bone in the ring mounting simulating a femoral or humeral mounting. C: Central position of tibia in too small of a ring, results in posterior soft tissue impingement. A larger ring should have been used to center the bone within the ring and avoid soft tissue concerns.
A: Eccentric bone location in the ring, simulating a tibial mounting. B: Center/center location of bone in the ring mounting simulating a femoral or humeral mounting. C: Central position of tibia in too small of a ring, results in posterior soft tissue impingement. A larger ring should have been used to center the bone within the ring and avoid soft tissue concerns.
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A typical three- or four-ring frame consists of eight crossed wires, two wires at each level and four rings with supporting struts connecting two rings on either side of the fracture (Fig. 8-12). When this circular frame was tested against the standard Hoffman-Vidal quadrilateral transfixion frame, the circular type frame was noted to be stiffer in compression. However, the circular fixators are less rigid than all other monolateral-type fixators in all modes of loading, most particularly in axial compression.15,45,59 This may be clinically beneficial to allow for axial micromotion and facilitate secondary bone healing.80 The Ilizarov fixator allowed significantly more axial motion at the fracture site during axial compression than the other fixators tested; however, the device controlled shear at the fracture site as well as other half-pin frames.80,147 The overall stiffness and shear rigidity of the Ilizarov external fixator are similar to those of the half-pin fixators in bending and torsion.95,140,158,194,233,258,311 

Wire Connecting Bolts

Mechanical slippage between wire and fixation bolt is the primary reason for loss of wire tension and thus frame instability. The change in wire stiffness can be explained mainly as a result of wire slippage, but plastic deformation and material yielding also contribute.108 Studies demonstrate that when clamping a wire to the frame, the wire tension is reduced by approximately 7%.260 This may be because of wire deformation by the bolts and as such can reduce wire tension during fixator assembly.306,307 Slippage can be avoided by adequate torque on the fixation bolt, that is, greater than 20 N m. Material yield accompanied by some wire slippage through the clamps is responsible for the decreased tension at the pin–clamp interface (Fig. 8-38). The relatively simple modification made by roughening the wire–bolt interface resulted in improved holding capacity and wire stiffness and these fixation devices are now clinically available.108 Although the initial wire tension has an appreciable effect on the wire stiffness, it does not affect the elastic load range of the clamp wire system. To prevent yield of the clamp wire system in clinical practice, the fixator should be assembled with sufficient wires to ensure that the load transmitted to each wire by the patient does not exceed 15 N.313 Adding additional wires will increase the frame stiffness directly proportional to the number of wires in the system. Stiffness of an Ilizarov frame is more dependent on bone preload than on wire number, wire type, or frame design. Preload stiffness can be increased simply by compressing the rings together and achieving bone-on-bone contact.15,16,42,44,47,97 
Figure 8-38
Wire fixation bolt that captures the wire and prevents “slippage” after tensioning has taken place.
Rockwood-ch008-image038.png
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Hybrid Fixators

Because of the complexity in the assembly of a full circular ring fixator, hybrid configurations were developed to take advantage of tensioned wires’ ability to stabilize complex periarticular fractures. Early designs married a periarticular ring using few tensioned wires to a monolateral bar connected to the shaft using two to three half pins. Unfortunately, these simple frames were shown to be mechanically inferior in their abilities to resist cantilever loading with resultant malunion/nonunion (Fig. 8-13B).158,236,237,246,301 Mechanical instability was especially pronounced when the frames were applied with specific errors in technique: (1) Insertion of only two transfixion wires in periarticular locations. Because of anatomic constrains the wires cannot be placed at 90 degrees to each other in most periarticular locations. As noted previously, if the two wires are not at 90 degrees then the bone can translate easily along the two wires. (2) Half pins placed too far from the site of pathology placing significant strain on the connecting clamps to maintain frame stability (Fig. 8-39). 
Figure 8-39
“Hybrid” frame demonstrating mechanical instability with only two periarticular tensioned wires on the distal ring and two small monolateral bars connecting two diaphyseal half pins located at an extreme distance from the fracture.
This unstable fixation resulted in fracture nonunion.
This unstable fixation resulted in fracture nonunion.
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The term “hybrid” when applied to external fixation denotes the use of half pins and wires in the same frame mounting as well as using a combination of rings and monolateral connecting bars. Stable hybrid frames should include a ring incorporating multiple levels of fixation in the periarticular fragment. This is accomplished with a minimum of three tensioned wires and if possible, an additional level of periarticular fixation using adjunctive half pins.5,6,15,38,158 
The use of a single bar connecting the shaft to the periarticular ring places significant stresses on the single connecting clamp and accentuates the harmful off-axis forces generated with weight bearing. Multiple connecting bars or a full circular frame is preferred with a minimum of four half pins attached to the shaft component.5,6,42,236,237,246,311 

Biology of External Fixation and Distraction Histogenesis

Basic Biology

The fracture repair process proceeds through constant physiologic stages depending on external forces imparted to the fracture site. There are four distinct types of fracture healing which have been identified. External fixation facilitates external bridging callous. 
External bridging callous is largely under the control of mechanical and biologic factors and is highly dependent upon the integrity of the surrounding soft tissue envelope. The critical cells necessary for healing are derived from the surrounding soft tissues and from the revascularization response that occurs during the inflammatory phase of fracture healing.39,138,139 This type of fracture healing has the ability to bridge large gaps and is very tolerant of movement. It results in the development of a large callous with the formation of cartilage because of the greater inflammatory response caused by increased micromovement of the fragments.155,174 Migrating mesenchymal cells from the surrounding area reach the fracture ends where they differentiate into various cell types, primarily cartilage. The cartilage is formed in the well-vascularized granulation tissue because of its ability to repel vessels. These early cartilaginous elements undergo remodeling through endochondral bone formation. It is well known that this type of indirect bone healing occurs with less rigid interfragmentary stabilization.154156 The rate of this type of healing and the extent of callous in this type of repair can be modulated by mechanical conditions at the fracture site.183 It has been shown that applying cyclic interfragmentary micromotion for short periods of time influences the repair process and leads to a larger area of callous formation compared with those fractures that are rigidly fixed.10,11,56,80,110,111,123,147,154156,224,230 Alternatively, efforts to reduce micromotion by increasing frame stiffness can cause a significant reduction in the rate of healing.21,50,310,314 
Larger interfragmentary movements lead to more fibrocartilage, as well as an increase in the number of blood vessels.56,292 However, as the amount of fibrocartilages increases, the ability for remodeling and bone formation is simultaneously decreased. There appears to be some threshold at which the degree of micromotion becomes inhibitory to the remodeling process and thus hypertrophic nonunion can result. It should be noted, however, that fractures requiring external fixation in general are usually more complex, which may result in an intrinsically higher rate of nonunion. Healing problems encountered in these severe injuries may reflect the severity of the local soft tissue and periosteal injury, and should not be attributed solely to the inherent features of the external fixation device. 
Bony healing is not complete until remodeling of the fracture has been achieved. At this stage, the visible fracture lines in the callous decrease and subsequently disappear. The bone transmits mechanical forces to the encapsulating callous as the tissue differentiates from granulation tissue to collagen and hyaline cartilage, and then to woven intramedullary bone through the process of endochondral bone formation.140,293 

Dynamization

Dynamization converts a static fixator which neutralizes all forces including axial motion to a construct that allows the passage of controlled forces across the fracture site. As the elasticity of the callous decreases, bone stiffness and strength increase and larger loads can be supported. Thus the advantages of axial dynamization help to restore cortical contact and produce a stable fracture pattern with inherent mechanical support. Aro described a uniform distribution of callous following dynamization and noted this as “secondary contact healing.”11,13 By increasing cortical contact, dynamization attempts to decrease the translational shear forces.10,11,13 Shear forces are thought to be the leading factor in producing a predominance of fibrous tissue at the fracture site with resultant delayed or nonunion.19,26,42,52 
Frames are distinguished between static and dynamic fixators. Active dynamization occurs with weight bearing or with loading when there is progressive closure of the fracture gap. This usually occurs by making adjustments in the pin bar clamps with simple monolateral fixators. This is accomplished by loosening the clamp portion that attaches to the bar which then allows the bar to slide within the clamp. The pin portion is still tight and thus the fracture can “slide” and compress or dynamize, whereas the alignment is maintained by the pin portion still remaining securely attached. For large monotube fixators the telescoping body can be released and the tow portions allowed to compress across the fracture. Dynamization also decreases the pin–bone stresses and prolongs the lifetime of the frame.147,154,192 
There is a race between the gradually increasing load-carrying capacity of the healing bone and failure of the pin–bone interface. In unstable fractures, very high stresses can occur at the pin–bone interface which may create localized yielding failure. In half-pin frames these high stresses are generated primarily at the entry cortex and stress-related pin–bone failures occur mainly in this location.231 It is well accepted that the relative motion of the bone ends at the fracture site is a very important parameter in the healing of the fracture; however, the threshold at which this motion becomes deleterious is as yet unknown.60,140 

Fracture Healing with Limited ORIF Combined with External Fixation

On occasion, it is advantageous to perform limited internal fixation in combination with an external fixator. Whereas this type of methodology is very useful in metaphyseal bone and has been demonstrated to work well in periarticular fractures, its use in diaphyseal regions must be questioned. The use of interfragmentary screws seeks to achieve direct bone healing through the use of constant compression. Primary cortical healing occurs only when mechanical immobilization is absolute and bony apposition is perfect. It is very intolerant of movement and is not dependent upon soft tissues. This type of healing is very slow and has no ability to cross gaps, as opposed to external bridging callous.127,154 In many ways, it represents bone healing through gradual remodeling. Primary cortical healing is characterized by sequential cutting cones of osteoclasts crossing across the fracture line with subsequent re-establishment of new osteons. The vasculature develops from a budding process sprouting from the intramedullary blood vessels, which are very fragile and intolerant of motion. The external fixator does not entirely eliminate extraneous forces, but seeks to limit the degree of micromotion.56,127,132,140,147,154,292 Therefore, because the bone is rigidly fixed with lag screws, very poor bridging callous develops. Because external fixators do not produce absolute rigidity, insufficient cortical healing occurs, demonstrating the worst of both biologic entities.224 This technique has been abandoned for use in diaphyseal regions because of the increased incidence of pseudoarthrosis. A combination of internal and external fixation for diaphyseal fractures may at first appear to be desirable, but is in fact often disastrous and should be avoided.274 

Biology of Distraction Osteogenesis

Distraction osteogenesis is the mechanical induction of new bone that occurs between bony surfaces that are gradually pulled apart. Ilizarov described this as “the tension stress effect.” 138140 Osteogenesis in the gap of a distracted bone takes place by the formation of a physis-like structure. New bone forms in parallel columns extending in both directions from a central growth region known as the interzone (Fig. 8-40A). Recruitment of the tissue-forming cells for the interzone originates in the periosteum.15,16,140 Under the influence of tension stress, fibroblast-like cells found in the middle of the growth zone develop an elongated shape and are orientated along the tension stress vector during distraction. Surrounding the fibroblast-like cells are collagen fibers aligning parallel to the direction of the tension vector. The fibroblastic cells transform into osteoblasts which deposit osteoid tissue upon these collagen fibers. They further differentiate to become osteocytes within the bone matrix laid down upon the longitudinal collagen bundles. These cells will become incorporated into their own HA matrix as the collagen bundles are consolidated into bone. This tissue gradually blends into the newly formed bone trabeculae in the regions farthest away from the central interzone. Thus, newly formed bone grows both proximally and distally away from the middle of the distraction zone during elongation. These columns of bone will eventually cross the fibrous interzone to bridge the osteogenic surfaces following distraction (Fig. 8-40B).138140 
Figure 8-40
 
A: The interzone (dark “z” area midregenerate) is the central growth region involved in the genesis of new bone formation during distraction. B: Collagen fibrils line up along the vector of distraction. Osteoblasts line the collagen bundles forming new bone. There are large vascular channels surrounding each collagen bundle.
A: The interzone (dark “z” area midregenerate) is the central growth region involved in the genesis of new bone formation during distraction. B: Collagen fibrils line up along the vector of distraction. Osteoblasts line the collagen bundles forming new bone. There are large vascular channels surrounding each collagen bundle.
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Figure 8-40
A: The interzone (dark “z” area midregenerate) is the central growth region involved in the genesis of new bone formation during distraction. B: Collagen fibrils line up along the vector of distraction. Osteoblasts line the collagen bundles forming new bone. There are large vascular channels surrounding each collagen bundle.
A: The interzone (dark “z” area midregenerate) is the central growth region involved in the genesis of new bone formation during distraction. B: Collagen fibrils line up along the vector of distraction. Osteoblasts line the collagen bundles forming new bone. There are large vascular channels surrounding each collagen bundle.
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With stable fixation, osteogenesis in the distraction zone proceeds by direct intramembranous ossification omitting the cartilaginous phase characteristic of endochondral ossification. Distraction osteogenesis also provides a significant neovascularization effect. The fibroblast precursors are concentrated around sinusoidal capillaries. The growth of these newly formed capillaries under the influence of tension stress proceeds very rapidly and in some instances overgrows development of bony distraction resulting in enfolding of this tremendous capillary response. This dense network of newly formed blood cells has a longitudinal orientation connecting to the surrounding soft tissue vessels by numerous arteries that perforate the regenerate bone. Thus the regenerate distraction gap is very vascular, with large vascular channels that surround each longitudinal column of distracted collagen. Neovascularization extends from each bone end surface toward the central fibrous interzone. This intense formation of new blood vessels under the influence of tension stress occurs not only in the bone, but also in the soft tissues. These vessels contain a thin lining of endothelial cells very similar to the neovascular response that occurs in a centripetal fashion during routine fracture healing (Fig. 8-40B). 
The rate and rhythm of distraction are crucial in achieving viable tissue following distraction histogenesis. Histologic and biochemical studies have determined that a distraction rate of 0.5 mm per day or less leads to premature consolidation of the lengthening bone, whereas a distraction rate of 2 mm or greater often results in undesirable changes within the distracted tissues. Faster rates of distraction will disrupt the small vascular channels and areas of cysts can occur inhibiting mineralization.15,16,138140 For osteogenesis to proceed more rapidly, optimum preservation of the periosteal tissues, bone marrow, and surrounding soft tissue blood supply at the time of osteotomy is mandatory.140,299 The new bone and soft tissues are formed parallel to the tension vector even when the vector is perpendicular to the limb’s overall mechanical axis. 
Studies have documented that superior bone regenerate is formed when a very low energy osteoclasis technique is utilized to produce a corticotomy. This is achieved by osteotomizing the anterior, anterior lateral, and anterior medial cortices, and then performing a closed osteoclasis maneuver to the posterior cortex preserving the periosteal tissues as much as possible.164 Ilizarov recommended a rate of 1-mm total distraction (rate of distraction) per day. The actual number of distractions (rhythm of distraction) should be at least four each day, achieving the total daily distraction in four divided doses. His work has also demonstrated that constant distraction over a 24-hour period produces a significant increase in the regenerate quality as compared to other variables.138140 
In this setting, when motion is present at the fracture site, bone resorption always occurs. The greater the interfragmentary motion at the site of the fracture, the greater the resorption of the fragment and slower the consolidation. The healing process depends on arterial revascularization and if the fracture fragments are excessively mobile, the local blood supply is traumatized by the moving bone ends.56,212,292 Instability that introduces translational shear across the distraction gap will result in an atrophic fibrous nonunion with mixed cartilage and incomplete vascular channels, interspersed within the longitudinal collagen columns. In these areas of mechanical instability, intramembranous ossification is irregular with islands of endochondral ossification seen and if local vascularity is insufficient, mineralization will be inhibited leaving necrotic fibrous areas or vascular cysts. 
Circular frames are able to limit the magnitude of abnormal forces when they are placed in compression.15,16,80,158 This stabilizes the small blood vessels and allows for neutralization of the forces that are destructive to the neovascular region.15,16 This allows endochondral bone remodeling to proceed. 
Compression osteosynthesis with constant compression on the bone does not suppress the reparative process and does not cause damage or resorption of the bone tissues. Under conditions of both compression and distraction in the presence of stable fixation, bone is actively formed by cellular elements of the endosteum, bone marrow, and periosteum. The osteogenic activity of connective tissue is stimulated by tension stress when the tissue is stabilized. Soon after the end of distraction, the connective tissue is replaced by bone. Therefore compression or dynamization can facilitate healing of delayed or nonunions under this mechanical environment. Increase in axial loading is accompanied by enhanced blood supply that activates osteogenesis.138140,292 Many authors have demonstrated the positive benefit that axial loading combined with muscular activity has on new bone formation.154156,174 
As noted by Ilizarov, all tissues will respond to a slow application of prolonged tension with metaplasia and the differentiation into the corresponding tissue type. Bone responds best followed by muscle, ligament, and tendons in that order. Neurovascular structures will respond with gradual new vessels and some degree of nerve and vessel lengthening. However, they respond very slowly and are intolerant of acute distraction forces.138140,179 
Muscle growth results from the tension stress effect by increasing the number of myofibrils in pre-existing muscle. Muscle also responds by the formation of new muscle tissue through the increased numbers of muscle satellite cells, the appearance of myoblasts, and their fusion into myotubes. Within the newly formed muscle fibers active formation of myofibrils and sarcomeres also occurs.138140 Smooth muscle tissue and blood vessels walls are also stimulated by tension stress. Smooth muscle activity and proliferation are accompanied by an increase in the extent and number of intercellular contacts between myocytes and by the formation of new elastic structures. These morphologic changes in the ultra structure of arterial smooth wall muscle cells resemble the changes seen in the walls of arteries elongated during active prenatal and early postnatal growth.138140 
A similar response also occurs in the connective tissue of fascia, tendons, and dermis. The number of fibroblasts is increased during distraction and an increase in the density of intracellular junctions is multiplied, which is characteristic of fibroblasts in the developing connective tissue of embryos, fetuses, and newborn animals. The adventitial blood vessels in the epineurium and perineurium of major nerve trunks also undergo similar changes.138140 
Distraction, accomplished through the use of a ring fixator, or a stable monotube device, initiates the histogenesis of bone, muscle, nerves, and skin.15,16,138140,180 This facilitates the treatment of complex orthopedic diseases, including pathologic conditions such as osteomyelitis and fibrous dysplasia. Other conditions that have been historically refractory to standard treatments such as congenital pseudoarthrosis and severe hemimelias can also be addressed.61,64,140,150,196,211,253,275,281 
Bone transport methodologies can replace large skeletal defects with normal healthy bone structure, which is well vascularized and is relatively impervious to stress fractures. The ability to correct significant angular, translational, and axial deformities simultaneously through relative percutaneous techniques, as well as perform these corrections in an ambulatory outpatient setting adds to the attractiveness of this methodology (Figs. 8-41 and 8-42).55,81,118,119,140,148,187,220,257,258,285,295,298300,302 
Figure 8-41
Monotube device used to correct valgus deformity of the right knee (compare with left knee).
 
This is accomplished via gradual distraction across a distal femoral corticotomy.
This is accomplished via gradual distraction across a distal femoral corticotomy.
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Figure 8-41
Monotube device used to correct valgus deformity of the right knee (compare with left knee).
This is accomplished via gradual distraction across a distal femoral corticotomy.
This is accomplished via gradual distraction across a distal femoral corticotomy.
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Figure 8-42
 
A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
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A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
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Figure 8-42
A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
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A: Severe bone and soft tissue loss stabilized with a ring fixator. B: Gradual compression across defect gradually closes down the defect via soft tissue transport. C: Skin grafting was performed over reconstructed soft tissues, once docking of the bone ends had been completed. D: Healed tibia later underwent limb lengthening.
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Contemporary External Fixator Applications

Traditionally, external fixation has been used primarily for trauma applications, including the treatment of open fractures and closed fractures with high-grade soft tissue injury or compartment syndrome. In addition, external fixation has been used in critically ill patients with multiple long bone fractures as a method for temporary stabilization of these injuries. 
Following the adoption of circular and hybrid techniques, indications have been expanded to include the definitive treatment of complex periarticular injuries which include high-energy tibial plateau and distal tibial pilon fractures. With the introduction of minimally invasive techniques, combined with locking plate technologies, the indications for use of circular fixation for the definitive fixation of periarticular fractures have narrowed. Circular fixator use in periarticular injuries is largely restricted to the most severe fractures patterns with extensive comminution, bone loss, or critical soft tissue injury. 
Given the mechanical and biologic advantages of external fixation, their use in reconstructive orthopedics has gained wider acceptance and is currently used for limb lengthening, osteotomy, fusion, and deformity correction, as well as bone transport for the reconstruction of bone defects.37,119,170,221,246,298,300 

Damage Control External Fixation

The concept of temporary spanning fixation for complex articular injuries has become widely accepted. The ability to achieve an initial ligamentotaxis reduction substantially decreases the amount of injury-related swelling and edema by reducing deformity. It is important to achieve an early reduction, as a delay for more than a few days will result in an inability to disimpact displaced metaphyseal fragments. When definitive stabilization is attempted, reduction will be more difficult by indirect means and may require larger or more extensile types of incisions.227,270,294,296,302,303 With temporary fixation in place, the patient is then able to have other procedures or tests performed while effective distraction is maintained and the soft tissues are put to rest (Fig. 8-43). 
Figure 8-43
 
A: Polytrauma patient with a complex injury at the knee with a distal femur and proximal tibial fracture. B: Temporary knee-spanning frame placed on this patient. Note multiple connecting bars to compensate for this large patient. C: Knee fractures spanned out to length to await definitive reconstruction once patient’s condition improves. D: Necrotizing fasciitis in another polytrauma patient who had sustained a severe crush injury to the entire lower extremity. The spanning fixator is spanning multiple ipsilateral fractures with an associated compartment syndrome. Entire limb was spanned to include the patient’s knee and ankle.
A: Polytrauma patient with a complex injury at the knee with a distal femur and proximal tibial fracture. B: Temporary knee-spanning frame placed on this patient. Note multiple connecting bars to compensate for this large patient. C: Knee fractures spanned out to length to await definitive reconstruction once patient’s condition improves. D: Necrotizing fasciitis in another polytrauma patient who had sustained a severe crush injury to the entire lower extremity. The spanning fixator is spanning multiple ipsilateral fractures with an associated compartment syndrome. Entire limb was spanned to include the patient’s knee and ankle.
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Figure 8-43
A: Polytrauma patient with a complex injury at the knee with a distal femur and proximal tibial fracture. B: Temporary knee-spanning frame placed on this patient. Note multiple connecting bars to compensate for this large patient. C: Knee fractures spanned out to length to await definitive reconstruction once patient’s condition improves. D: Necrotizing fasciitis in another polytrauma patient who had sustained a severe crush injury to the entire lower extremity. The spanning fixator is spanning multiple ipsilateral fractures with an associated compartment syndrome. Entire limb was spanned to include the patient’s knee and ankle.
A: Polytrauma patient with a complex injury at the knee with a distal femur and proximal tibial fracture. B: Temporary knee-spanning frame placed on this patient. Note multiple connecting bars to compensate for this large patient. C: Knee fractures spanned out to length to await definitive reconstruction once patient’s condition improves. D: Necrotizing fasciitis in another polytrauma patient who had sustained a severe crush injury to the entire lower extremity. The spanning fixator is spanning multiple ipsilateral fractures with an associated compartment syndrome. Entire limb was spanned to include the patient’s knee and ankle.
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Many types of temporary “traveling traction” have been described. Most commonly used are the knee- or ankle-bridging constructs. This may be a simple quadrilateral frame, constructed by applying medial and lateral radiolucent external bars to proximal and distal threaded transfixion pins placed across the respective joint. Manual distraction is carried out and a ligamentotaxis reduction achieved (Fig. 8-44). A simple anterior monolateral frame can be used to maintain similar reduction across the knee joint for temporizing the management of knee dislocations, complex distal femoral fractures, and tibial plateau fractures (Fig. 8-58).227,270,294,296,297,303 A simple monolateral frame can be configured in a triangular-type construct about the distal tibial and ankle region in an effort to achieve relative stability. These are usually constructed with two or three pins in the mid- to distal tibia and a single transversely placed centrally threaded calcaneal tuberosity pin. These tibia pins are then connected in a triangular fashion with distraction across the calcaneal pin effecting a ligamentotaxis reduction at the distal tibia (Figs. 8-44 and 8-45). This typical external fixator construct can obscure the site of injury on radiographs, and because the construct may rotate about the solitary pin calcaneal, many complications have been attributed to this unstable pin site. Pin tract infections, loosening of the calcaenal pin fixation, and heel ulcerations, have all been reported.323 Strategies to prevent calcaneal complications have included the placement of two longitudinal axis pins placed from posterior to anterior in the body of the calcaneous to prevent rotation. These are then connected to a U-tube bar around the posterior calcaneous. The calcaneous pin connecting the bar is then attached to the tibial shaft pin/bar couple with distraction performed at the ankle joint. Alternatively, application of forefoot pins and stabilization of the foot in neutral position not only prevents rotation with calcaneal pin loosening, but also maintains the foot in neutral and prevents the common complication of forefoot equinus (Fig. 8-46).24 
Figure 8-44
 
A: (top) A severe ankle fracture dislocation with compartment syndrome and significant soft tissue compromise was spanned with a triangular ankle-spanning external fixator. The reduction achieved with the simple frame facilitates the definitive reconstructive procedures once soft tissue recovery has occurred and the fasciotomy incisions have healed (bottom). B: A pilon fracture stabilized with an ankle-spanning frame. The forefoot was maintained in neutral with the addition of a metatarsal pin. C: A ligamentotaxis reduction maintained alignment and allowed definitive reconstruction once the soft tissues had recovered. D: Simple two-pin fixator spanning open tibia fracture to allow for staged debridement and eventual IM nailing, once the zone of injury has been defined.
A: (top) A severe ankle fracture dislocation with compartment syndrome and significant soft tissue compromise was spanned with a triangular ankle-spanning external fixator. The reduction achieved with the simple frame facilitates the definitive reconstructive procedures once soft tissue recovery has occurred and the fasciotomy incisions have healed (bottom). B: A pilon fracture stabilized with an ankle-spanning frame. The forefoot was maintained in neutral with the addition of a metatarsal pin. C: A ligamentotaxis reduction maintained alignment and allowed definitive reconstruction once the soft tissues had recovered. D: Simple two-pin fixator spanning open tibia fracture to allow for staged debridement and eventual IM nailing, once the zone of injury has been defined.
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Figure 8-44
A: (top) A severe ankle fracture dislocation with compartment syndrome and significant soft tissue compromise was spanned with a triangular ankle-spanning external fixator. The reduction achieved with the simple frame facilitates the definitive reconstructive procedures once soft tissue recovery has occurred and the fasciotomy incisions have healed (bottom). B: A pilon fracture stabilized with an ankle-spanning frame. The forefoot was maintained in neutral with the addition of a metatarsal pin. C: A ligamentotaxis reduction maintained alignment and allowed definitive reconstruction once the soft tissues had recovered. D: Simple two-pin fixator spanning open tibia fracture to allow for staged debridement and eventual IM nailing, once the zone of injury has been defined.
A: (top) A severe ankle fracture dislocation with compartment syndrome and significant soft tissue compromise was spanned with a triangular ankle-spanning external fixator. The reduction achieved with the simple frame facilitates the definitive reconstructive procedures once soft tissue recovery has occurred and the fasciotomy incisions have healed (bottom). B: A pilon fracture stabilized with an ankle-spanning frame. The forefoot was maintained in neutral with the addition of a metatarsal pin. C: A ligamentotaxis reduction maintained alignment and allowed definitive reconstruction once the soft tissues had recovered. D: Simple two-pin fixator spanning open tibia fracture to allow for staged debridement and eventual IM nailing, once the zone of injury has been defined.
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Figure 8-45
 
A: Open tibial shaft fracture with complex foot injury is temporarily stabilized with a spanning monolateral fixator. B: An anatomic reduction was achieved and maintained with the frame. Once soft tissues are recovered and the patient’s condition stabilized, the frame was converted to an IM nail at 10 days post injury.
A: Open tibial shaft fracture with complex foot injury is temporarily stabilized with a spanning monolateral fixator. B: An anatomic reduction was achieved and maintained with the frame. Once soft tissues are recovered and the patient’s condition stabilized, the frame was converted to an IM nail at 10 days post injury.
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Figure 8-45
A: Open tibial shaft fracture with complex foot injury is temporarily stabilized with a spanning monolateral fixator. B: An anatomic reduction was achieved and maintained with the frame. Once soft tissues are recovered and the patient’s condition stabilized, the frame was converted to an IM nail at 10 days post injury.
A: Open tibial shaft fracture with complex foot injury is temporarily stabilized with a spanning monolateral fixator. B: An anatomic reduction was achieved and maintained with the frame. Once soft tissues are recovered and the patient’s condition stabilized, the frame was converted to an IM nail at 10 days post injury.
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Figure 8-46
 
A: Ankle-spanning fixator placed to distract pilon fracture and place soft tissues at rest. Note excellent skin wrinkles denoting soft tissues’ availability for surgery. B: Patient did not have any forefoot pins or adjunctive calcaneous fixation allowing the heel to rotate about the axis of the heel pin. This can result in early pin loosening and equinus positioning.
A: Ankle-spanning fixator placed to distract pilon fracture and place soft tissues at rest. Note excellent skin wrinkles denoting soft tissues’ availability for surgery. B: Patient did not have any forefoot pins or adjunctive calcaneous fixation allowing the heel to rotate about the axis of the heel pin. This can result in early pin loosening and equinus positioning.
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Figure 8-46
A: Ankle-spanning fixator placed to distract pilon fracture and place soft tissues at rest. Note excellent skin wrinkles denoting soft tissues’ availability for surgery. B: Patient did not have any forefoot pins or adjunctive calcaneous fixation allowing the heel to rotate about the axis of the heel pin. This can result in early pin loosening and equinus positioning.
A: Ankle-spanning fixator placed to distract pilon fracture and place soft tissues at rest. Note excellent skin wrinkles denoting soft tissues’ availability for surgery. B: Patient did not have any forefoot pins or adjunctive calcaneous fixation allowing the heel to rotate about the axis of the heel pin. This can result in early pin loosening and equinus positioning.
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Temporary column distraction is a useful technique for complex foot injuries. Mini–ex fix components are used to distract across medial column injuries such as complex “nut cracker” navicular fractures,162 medial cuneiform fractures, and metatarsal base fractures/dislocations where the fracture morphology results in significant shortening of the medial column. Similarly, lateral column mini fixators can be used to maintain length in cases of comminuted cuboid, lateral cuneiform, and lateral metatarsal base fracture/dislocations. Simple two-pin mini fixators are placed with single 2.5-, 3-, or 4-mm Schanz pins placed proximally (usually medially in the talar neck or in the lateral calcaneous), with distal fixation into the first or fifth metatarsal shafts and a simple distraction bar attached to maintain length (Fig. 8-47). Once the soft tissues have recovered then definitive reconstruction is carried out with the reduction accomplished and maintained early (Fig. 8-48).32,49,71,217 
Figure 8-47
 
A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
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A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
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Figure 8-47
A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
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A, B: Complex forefoot injury with midfoot dislocation and navicular fracture. C, D: Medial and lateral column distraction accomplished with mini fixator components. E, F: Fixator maintained during definitive reconstruction for additional stability postoperatively. G: Frames removed at approximately 3 weeks post ORIF.
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Figure 8-48
 
A: Complex Lisfranc fracture dislocation of forefoot stabilized initially with medial column distraction. B, C: Postoperative views of bridge plate fixation of medial column injury with the addition of a lateral column distractor to maintain the reduced position.
A: Complex Lisfranc fracture dislocation of forefoot stabilized initially with medial column distraction. B, C: Postoperative views of bridge plate fixation of medial column injury with the addition of a lateral column distractor to maintain the reduced position.
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Figure 8-48
A: Complex Lisfranc fracture dislocation of forefoot stabilized initially with medial column distraction. B, C: Postoperative views of bridge plate fixation of medial column injury with the addition of a lateral column distractor to maintain the reduced position.
A: Complex Lisfranc fracture dislocation of forefoot stabilized initially with medial column distraction. B, C: Postoperative views of bridge plate fixation of medial column injury with the addition of a lateral column distractor to maintain the reduced position.
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Application of these techniques in a polytraumatized patient is valuable when rapid stabilization is necessary for a critically injured or physiologically unstable patient, so-called DCOs. Simple monolateral or monotube fixators can be placed very rapidly across long bone injuries providing adequate stabilization to facilitate the management and resuscitation.121,279 Excessive traction across a joint should be avoided when applying these temporary joint-spanning frames. By overdistracting these extremities, the muscular compartments can become stretched effectively compressing the compartments and lead to late compartment syndrome.84 However, the most common complication encountered when utilizing temporary spanning external fixation is the inability to re-establish length. As well, fixator “creep” or gradual loosening of the fixator components may occur prior to definitive reconstruction, causing the initial reduction and length to be lost. If correct length is not maintained, then when definitive reconstruction is undertaken many of the perceived advantages of spanning external fixation are lost.214 If a delay of more than a week is anticipated prior to definitive reconstruction, interim radiographs should be performed and repeat reduction performed if length has been lost. 
For periarticular fractures, the decision to convert to definitive stabilization is usually based on the condition of the soft tissues. A latency period of at least 10 to 14 days is required to allow the soft tissues to recover to the extent where definitive fixation can be undertaken safely. Many series have demonstrated excellent results achieved with a staged approach consisting of early fracture stabilization using spanning external fixation. This is followed by careful preoperative planning based on traction CT scans and the judicious clinical evaluation of the soft tissue injury prior to definitive internal fixation.4,181,223,227,270,303 When applying temporary spanning external fixation there was concern that overlap of external fixation pins and the proposed definitive incision would increase infection rates and should be avoided. Investigators evaluated the overlap between temporary external fixator pins and definitive plate fixation correlates with infection in high-energy tibial plateau fractures. 
There was no correlation seen between any deep plate-related infection and distance from pin to plate, pin–plate overlap distance, time in the external fixator, open fracture, classification of fracture, sex of the patient, age of the patient, or healing status of the fracture.171 Fears of definitive fracture fixation site contamination from external fixator pins do not appear to be clinically grounded. Thus a temporary external fixation construct with pin placement that provides for the best reduction and stability of the fracture, regardless of plans for future surgery, is recommended (Fig. 8-49). 
Figure 8-49
 
A, B: Complex bicondylar plateau fracture with associated compartment syndrome with medial and lateral fasciotomy wounds. Note the location of potential incisions for eventual ORIF have been marked on the skin medially and laterally. This is done to place pins and connecting bars out of the proposed fixation area.
A, B: Complex bicondylar plateau fracture with associated compartment syndrome with medial and lateral fasciotomy wounds. Note the location of potential incisions for eventual ORIF have been marked on the skin medially and laterally. This is done to place pins and connecting bars out of the proposed fixation area.
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Figure 8-49
A, B: Complex bicondylar plateau fracture with associated compartment syndrome with medial and lateral fasciotomy wounds. Note the location of potential incisions for eventual ORIF have been marked on the skin medially and laterally. This is done to place pins and connecting bars out of the proposed fixation area.
A, B: Complex bicondylar plateau fracture with associated compartment syndrome with medial and lateral fasciotomy wounds. Note the location of potential incisions for eventual ORIF have been marked on the skin medially and laterally. This is done to place pins and connecting bars out of the proposed fixation area.
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The timing of conversion of a DCO external fixator to an intramedullary nail is determined by the condition of the soft tissues and the overall stability of the patient. With the temporary stabilization of long bone fractures, definitive conversion to intramedullary nailing has demonstrated variable success especially in the tibia.67 Most authors would suggest early (within the first 2 to 3 weeks of frame application) conversion to intramedullary nailing to avoid colonization of the medullary canal by the external fixator pins. Increased infection rates have been documented when conversion is done after 2 weeks of external fixation. It has been shown that the longer the external fixator remains in place, the greater the risk of complications occurring following conversion to intramedullary devices, especially if the pins are removed and the nail exchanged at the same operative setting (Fig. 8-50).143,196 
Figure 8-50
 
A–C: Severe soft tissue injury prevents acute IM nailing of the femoral shaft. Fracture. Stability required spanning across the knee to maintain reduction. Secondary conversion to IM occurred at 12 days post injury with no secondary infection noted.
A–C: Severe soft tissue injury prevents acute IM nailing of the femoral shaft. Fracture. Stability required spanning across the knee to maintain reduction. Secondary conversion to IM occurred at 12 days post injury with no secondary infection noted.
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Figure 8-50
A–C: Severe soft tissue injury prevents acute IM nailing of the femoral shaft. Fracture. Stability required spanning across the knee to maintain reduction. Secondary conversion to IM occurred at 12 days post injury with no secondary infection noted.
A–C: Severe soft tissue injury prevents acute IM nailing of the femoral shaft. Fracture. Stability required spanning across the knee to maintain reduction. Secondary conversion to IM occurred at 12 days post injury with no secondary infection noted.
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In the femur, conversion from external fixation to nailing has demonstrated good rates of success if the exchange is done when the patient’s overall physical condition has improved. Acute conversion to an intramedullary device for the femur in a single procedure is preferred in patients without evidence of pin tract infection. Studies have shown that infection rates after DCO for femoral fractures are comparable to those after primary intramedullary nailing (IMN). One study suggested an increased risk for DCO femoral fractures treated with initial external fixation compared with those placed in traction.259 Scannell et al.259 found in a comparative study that the initial traction group of femoral fractures had a lower rate of sepsis (8.3% vs. 31.6%, p = 0.0194) and a shorter length of stay (26.5 days vs. 36.2 days, p = 0.0237) than the initial external fixation group. However, there appears to be no contraindication to the implementation of a damage control approach for severely injured patients with femoral shaft fractures initially subjected to general anesthesia for life-saving procedures when appropriate. Pin site contamination is more common when the femoral fixator is in place for more than 2 weeks. For patients treated by using a DCO approach, conversion to definitive fixation should be performed in a timely fashion.29,128 
Stabilization of unstable pelvic fractures has been achieved by the rapid application of simple external fixation for use in the immediate resuscitative period. The application of an external frame affords significant reduction in the volume of the true pelvis, as well as stabilizing the movement of large bony cancellous surfaces along the posterior aspect of the pelvic ring. The ability to provide stabilization and decrease the pelvic volume allows the surgeon to control hemorrhage and has helped to contribute to the low mortality seen with these injuries.63,153 
Anterior pelvic external fixator constructs provide excellent adequate fixation, and traditional constructs include single and multiple pin placements in several locations in each iliac crest. However, anterior frame application, specifically the anterior superior iliac crest pins that course between the inner and outer iliac tables may be problematic. These frames may be difficult to apply in a large obese patient.122 As well, these pins may loosen very rapidly because of the variable pin purchase in cancellous bone (Fig. 8-51). 
Figure 8-51
 
A: Pelvic injury with anterior and posterior disruption and hemodynamic instability. Note large abdominal pannus prohibiting supra-acetabular pin placement. B: Simple anterior frame applied to help in the resuscitation of the patient and provide temporary pelvic stabilization. C: Anterior iliac wing frames can be modified with additional crest pins and additional bars to increase stability.
A: Pelvic injury with anterior and posterior disruption and hemodynamic instability. Note large abdominal pannus prohibiting supra-acetabular pin placement. B: Simple anterior frame applied to help in the resuscitation of the patient and provide temporary pelvic stabilization. C: Anterior iliac wing frames can be modified with additional crest pins and additional bars to increase stability.
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Figure 8-51
A: Pelvic injury with anterior and posterior disruption and hemodynamic instability. Note large abdominal pannus prohibiting supra-acetabular pin placement. B: Simple anterior frame applied to help in the resuscitation of the patient and provide temporary pelvic stabilization. C: Anterior iliac wing frames can be modified with additional crest pins and additional bars to increase stability.
A: Pelvic injury with anterior and posterior disruption and hemodynamic instability. Note large abdominal pannus prohibiting supra-acetabular pin placement. B: Simple anterior frame applied to help in the resuscitation of the patient and provide temporary pelvic stabilization. C: Anterior iliac wing frames can be modified with additional crest pins and additional bars to increase stability.
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A recent study compared the stability provided by a two-pin iliac crest fixator to the stability provided by a commercially available binder device (trauma pelvic orthotic device [T-POD]). Mechanical testing simulated log rolling the patient and performing bed transfers. The T-POD conferred more stability in all planes of motion, although this did not reach statistical significance. This study does document the equivalency of the T-POD devices and suggests that clinicians advocate acute, temporary stabilization of pelvic injuries with a binder device followed by early conversion to internal fixation when the patient’s medical condition allows.223 
Recent biomechanical and anatomic studies have focused on pin placement lower in the pelvis, specifically in the supra-acetabular region. Pins in this location are more stable biomechanically because of the improved purchase in the hard cortical bone of the posterior column (Fig. 8-52). This pin placement allows for pelvic reduction in the transverse plane of deformity and may allow improved reduction of the posterior elements. In addition, the location of the pins and frame can facilitate concurrent or subsequent laparotomy procedures.106,178 
Figure 8-52
 
A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
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A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
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Figure 8-52
A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
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A: Severe pelvic injury with anterior and posterior injury. B: Supra-acetabular pins placed and pelvic volume decreased. Note significant bending of these pins needed to maintain symphysis reduction. C, D: Correct placement technique of supra-acetabular pins using a trocar and drill sheath to protect the anterior soft tissue structures during insertion. The pin trajectory should parallel the superior acetabular dome (white arrow). E: Pins traverse the area just superior to the dome of the hip joint and gain purchase in the dense cortical bone of the posterior column. F, G: Location of supra-acetabular pins placed using 1.5-cm incisions which are closed following insertion. H: The connecting bar is located low on the pins and does not impinge on the abdominal tissues. I: Pins perfectly located just above the acetabular domes on both hips with excellent reduction of symphysis achieved.
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Pelvic frames are most useful in those fractures that are vertically stable.195 Rotationally unstable fracture such as anterior–posterior compression and lateral compression injuries are best suited to application of an anterior pelvic frame.63 At times, the application of an anterior frame may be complicated, cumbersome, and time consuming, and may be contraindicated as an emergency application. For this reason, a modification of pelvic external fixation, the C-clamp, can provide temporary stability in the patients with massive pelvic ring disruption and hemorrhage. 

Specific Fracture Management Using External Fixation

The choice of external fixator type depends on the location and complexity of the fracture, as well as the type of wound present when dealing with open injuries. The less stable the fracture pattern, the more stable a frame needs to be applied to control motion at the bone ends. If possible, weight bearing should be promoted. If periarticular extension or involvement is present, the ability to bridge the joint with the frame provides satisfactory stability for both hard and soft tissues. It is important that the frame be constructed and applied to allow for multiple debridements and subsequent soft tissue reconstruction. This demands that the pins are placed away from the zone of injury to avoid potential pin site contamination with the open wound (Fig. 8-49). In this setting, ring fixators have a potential advantage for extra-articular injuries in that they allow for immediate weight bearing and can gradually correct deformity and malalignment, as well as achieve active compression or distraction at the fracture site. 

Monolateral Applications

The largest indication for the use of monolateral frames for fracture management occurs in the distal radius and in the tibial shaft. This is followed closely by temporary application of trauma frames for complex femoral and humeral shaft injuries. Much less likely is the use of monolateral frames for forearm injuries. 

Wrist External Fixation

Specific fixators have been designed for use in the distal radius, and may be either joint bridging or joint sparing. Following the restoration of palmar tilt by closed fracture manipulation, wrist position can be adjusted into neutral or extension to help avoid finger stiffness and carpal tunnel syndrome without compromising fracture reduction. For unstable fractures, it has been shown that augmentation of the fixator construct with multiple dorsal and radial percutaneous pins corrects the dorsal tilt and maintains the reduction in those fractures that are difficult to maintain with distraction ligamentotaxis alone (Fig. 8-53).188,208 
Figure 8-53
Simple wrist spanning (bridging) fixator with two pins in the second metacarpal and two pins in the distal radius.
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The use of dynamic external fixation devices across the wrist allowing movement during fracture healing of unstable distal radial fractures has demonstrated mixed results. The concept was to achieve a ligamentotaxis reduction, and decrease the rate of stiffness by initiating early range of motion through uncoupling the device.74,113,167 For distal radius fractures with metaphyseal displacement but with a congruous joint, there exists a trend for better functional, clinical, and radiographic outcomes when treated by immediate external fixation and optional K-wire fixation compared with most conservative approaches including pins and plaster and closed reduction and casting. 
Adjuvant K-wire fixation is useful in cases with poor bone quality or in cases where the joint is highly comminuted with small articular fragments (Fig. 8-54). The K-wires are used as a buttress to maintain articular congruency, whereas the external fixator maintains the overall metaphyseal length and orientation.228 
Figure 8-54
 
A: Mini fixator used in combination with percutaneous pins to maintain reduction of a distal radius fracture. Solitary connecting bar placed between the metacarpal and radial pins. B: Alternative configuration using quadrilateral frame construct with percutaneous pins.
A: Mini fixator used in combination with percutaneous pins to maintain reduction of a distal radius fracture. Solitary connecting bar placed between the metacarpal and radial pins. B: Alternative configuration using quadrilateral frame construct with percutaneous pins.
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Figure 8-54
A: Mini fixator used in combination with percutaneous pins to maintain reduction of a distal radius fracture. Solitary connecting bar placed between the metacarpal and radial pins. B: Alternative configuration using quadrilateral frame construct with percutaneous pins.
A: Mini fixator used in combination with percutaneous pins to maintain reduction of a distal radius fracture. Solitary connecting bar placed between the metacarpal and radial pins. B: Alternative configuration using quadrilateral frame construct with percutaneous pins.
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Though there is insufficient evidence to confirm a better functional outcome, external fixation reduces redisplacement, and gives improved anatomical results compared with pins and plaster and other conservative modalities. Most of the surgically related complications are minor, probably related to the meticulous technique of pin insertion.124,165,182,276 External fixation devices function best when maintaining radial length alone.208 
Joint-bridging external fixation allows the radial length to be restored with the fixator; however, the anatomic reduction of articular fragments and restoration of the normal volar tilt proves to be more difficult when using a joint spanning frame. A method of nonbridging external fixation combined with percutaneous pinning facilitates fracture reduction and allows for free wrist movements (Fig. 8-55). The cross K-wires capture and stabilize the larger fragments while buttressing the smaller fragments. 
Figure 8-55
Fracture spanning (nonbridging) wrist fixator allows for range of motion with no loss in stability.
 
This joint sparing configuration is indicated in certain select distal radius fractures that have a distal fragment of sufficient size.
This joint sparing configuration is indicated in certain select distal radius fractures that have a distal fragment of sufficient size.
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Figure 8-55
Fracture spanning (nonbridging) wrist fixator allows for range of motion with no loss in stability.
This joint sparing configuration is indicated in certain select distal radius fractures that have a distal fragment of sufficient size.
This joint sparing configuration is indicated in certain select distal radius fractures that have a distal fragment of sufficient size.
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This technique has been modified and combines traditional cross-pin fixation of the distal fragments with a nonbridging external fixator. The cross K-wire configuration is constructed with pins in multiplanar and multiangle directions which creates a rigid construct. These cross pins are then attached an external strut locking them into position. Attaching the cross wires to an external fixator significantly improves fracture stability, allows for early mobilization of the wrist, and resumption of usual activities.199 This technique is simple and most orthopedic surgeons are familiar with it. This method has demonstrated no clinical differences when used for both intra- and extra-articular distal radius fractures compared with wrist bridging fixation.18,114,166,212 However, nonbridging fixation has been shown radiographically to reduce the risk of dorsal malunion compared with bridging external fixation.130 Major complication rates are low and the technique is applicable to most unstable fractures of the distal radius. Most authors recommend that nonbridging external fixation be used in cases where there is space for the pins in the distal fragment. The ability to maintain the reduction and minimize the total load transmitted from the wrist joint to the fracture site is fixator-dependent, and will differ from manufacturer to manufacturer.315 
There is no consensus on the surgical management of unstable distal radius fractures. In one systematic review and meta-analysis, data was pooled from trials comparing external fixation and open reduction and internal fixation (ORIF) for this injury. For unstable distal radius fractures, ORIF demonstrated significantly better functional outcomes, forearm supination, and restoration of anatomic volar tilt. However, external fixation resulted in better grip strength, wrist flexion, and remains a viable surgical alternative.228,309 

Femoral External Fixation

The use of external fixation for the management of acute femur fractures is primarily limited to pediatric indications, fractures with significant soft tissue or neurovascular compromise, or to those severely injured patients who cannot tolerate more extensive surgery (DCO). Commonly, femoral applications include the use of a minimum of four pins placed along the anterolateral aspect of the femoral shaft. These simple monolateral frames have been shown to provide adequate stabilization for most complex femoral fracture patterns (Figs. 8-50 and 8-56).6,31 Fixator constructs with independent pins placed out of plane relative to one another allow for safer pin insertion and demonstrate increased stability over monotube or simple monolateral frames where pins are placed in a straight line orientation.33,77 
Figure 8-56
 
A–C: Proximal femoral shaft fracture in a polytrauma patient. Damage control measures were necessary for the overall management of the patient and a simple external fixator maintained length and alignment while the patient recovered from his other injuries. Successful IM nailing was carried out at 14 days from his initial injury.
A–C: Proximal femoral shaft fracture in a polytrauma patient. Damage control measures were necessary for the overall management of the patient and a simple external fixator maintained length and alignment while the patient recovered from his other injuries. Successful IM nailing was carried out at 14 days from his initial injury.
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Figure 8-56
A–C: Proximal femoral shaft fracture in a polytrauma patient. Damage control measures were necessary for the overall management of the patient and a simple external fixator maintained length and alignment while the patient recovered from his other injuries. Successful IM nailing was carried out at 14 days from his initial injury.
A–C: Proximal femoral shaft fracture in a polytrauma patient. Damage control measures were necessary for the overall management of the patient and a simple external fixator maintained length and alignment while the patient recovered from his other injuries. Successful IM nailing was carried out at 14 days from his initial injury.
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In many underdeveloped nations, external fixation of femoral shaft fractures is often the definitive treatment. Monolateral or monotube fixators are commonly utilized with four or six pin configurations (Fig. 8-57). A pin tract infection with occasional pin loosening is the most commonly reported complication. Pin tract infections, although a common occurrence, are not a major problem and can be treated by local wound care and antibiotic therapy, and pin removal when required. The most common problem is significant decrease in the range of motion of the knee which can be difficult to treat successfully and is the major drawback to using this technique as definitive fixation when other methods are available.87,309 Other complications include the high rate of refracture following frame removal, especially when used in a pediatric population for definitive femoral shaft fracture treatment.48,238 
Figure 8-57
Pediatric patient with proximal femoral and tibial shaft fractures treated definitively with monotube large body fixators.
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Knee Dislocation

Knee dislocation is always a difficult topic mainly with regard to the structures that have been damaged and the best treatment option. Knee dislocation in the polytrauma patient is also problematic in the context of open knee dislocations or dislocation in association with arterial disruption, or compartment syndrome. 
In an effort to maintain the reduction and allow for arterial repair, compartmental release or the treatment of other injuries, spanning external fixation is a valuable option. Simple knee-spanning monolateral or monotube fixators can be easily applied with two pins above the knee located in the distal femur and two pins in the midtibia. The knee is reduced under fluoroscopy and the fixator locked, maintaining the reduction to facilitate other procedures and avoid the phenomenon of redislocation or subluxation that can occur when stabilizing these severe injuries with temporary splinting or casting (Fig. 8-58). In a biomechanical study, the stiffest construct for external fixation of a knee dislocation consisted of two anterolateral femoral pins and two monolateral rods connected to two tibial half pins (compared with a large monotube bar and a circular construct). This stiffer construct may provide a better clinical outcome and this frame configuration was recommended by the authors.197 
Figure 8-58
 
A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
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A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
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Figure 8-58
A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
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A, B: Severe open knee dislocation in conjunction with arterial disruption. C, D: Emergent knee-spanning fixator was applied at the time of initial surgical management which included arterial repair and multiple debridements. Wound was eventually closed and the patient underwent delayed ligamentous reconstruction at 10 weeks post injury.
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Following definitive surgical repair of associated ligamentous injuries of the globally unstable knee, some investigators advocate the immediate application of an articulated hinged knee fixator. Articulated external fixation has been proposed as a method to protect ligament reconstructions while allowing aggressive and early postoperative rehabilitation after knee dislocation.144,321 Mechanical studies have evaluated the additional stability afforded to knees by these monolateral or bilateral hinged knee frames.273 Application of articulated external fixators to specimens with intact ligaments significantly reduced cruciate ligament forces for Lachman, anterior drawer, and posterior drawer tests, respectively. Thus, there is biomechanical evidence that articulated external fixation of the knee can reduce stresses in the cruciate ligaments after multiligament reconstructions and can decrease anteroposterior translation in the cruciate-deficient knee.96 

Humeral External Fixation

External fixation is an infrequent treatment option for the management of acute humeral shaft fractures. Unlike the tibia in which fixator half pins can be placed perpendicular to the subcutaneous medial tibial face, external fixation in the humerus often involves transfixion of crucial musculotendinous units. Complications related to these frames may include pin track sequelae and an inhibition of shoulder and elbow motion. However, with contemporary fixation devices, the indications for use in the humerus continue to expand. In addition to their initial use for shaft injuries, many series now report the successful treatment of supracondylar and proximal humerus fractures treated with monolateral, circular, and hinge fixators.53,120,191 
The most frequent indication for use in the humerus is for the stabilization of severely contaminated open fractures from blunt trauma or gunshot wounds that occur in association with vascular disruption (Figs. 8-21 and 8-59). Rapid application of a simple four-pin external fixator provides excellent stability such that the limb may be manipulated during subsequent vascular arterial repair without concern for disruption of the repair. External fixation together with radical debridement has reduced the incidence of chronic infection and improved the prognosis for the vascular repair (Fig. 8-60). Average fixator time is dependent upon associated extremity injures and has been reported to be an average 16 weeks for these severe injuries. Secondary surgical procedures for soft tissue and bony reconstruction are facilitated and reported rates of pin tract infection are relatively low.207 
Figure 8-59
 
A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
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A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
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Figure 8-59
A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
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A, B: Gunshot wound humerus fracture in association with arterial injury. C: Humerus was emergently stabilized with a spanning external fixator and arterial repair was performed. D, E: Frame was removed at 11 weeks post injury with complete healing.
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Figure 8-60
Multiply injured patient with proximal humerus fracture.
 
Damage control measures included application of fracture-spanning external fixator. When the patient had recovered from initial injuries, definitive fixation was carried out at 9 days post injury.
Damage control measures included application of fracture-spanning external fixator. When the patient had recovered from initial injuries, definitive fixation was carried out at 9 days post injury.
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Figure 8-60
Multiply injured patient with proximal humerus fracture.
Damage control measures included application of fracture-spanning external fixator. When the patient had recovered from initial injuries, definitive fixation was carried out at 9 days post injury.
Damage control measures included application of fracture-spanning external fixator. When the patient had recovered from initial injuries, definitive fixation was carried out at 9 days post injury.
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When treating polytrauma or multiply injured patients, immediate external fixation and planned conversion to internal fixation of humeral shaft fractures is an option in the treatment of associated severe soft tissue injuries and severely injured patients (Fig. 8-60). A recent review of this technique documented no systemic complications after conversion from external to internal fixation, with excellent rates of healing following plating. The authors suggested that planned conversion to plate fixation within 2 weeks of external fixator application proved to be a safe and effective approach for the management of humeral shaft fractures in these selected patients.278 
Patients with supracondylar, intracondylar, and other fracture/dislocations about the elbow can be temporized by the application of a provisional elbow-spanning fixator. This restores length with a generalized repositioning of the fragments and can maintain the reduction of a grossly unstable elbow dislocation. When the patients’ status improves, or the soft tissues recover, definitive fixation of the injuries can be safely undertaken (Fig. 8-61). 
Figure 8-61
 
A, B: Severe open elbow injury with substantial articular injury. Stability was maintained with an elbow-spanning fixator before and after definitive surgery. Fixator was removed 3 weeks post ORIF and range of motion initiated.
A, B: Severe open elbow injury with substantial articular injury. Stability was maintained with an elbow-spanning fixator before and after definitive surgery. Fixator was removed 3 weeks post ORIF and range of motion initiated.
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Figure 8-61
A, B: Severe open elbow injury with substantial articular injury. Stability was maintained with an elbow-spanning fixator before and after definitive surgery. Fixator was removed 3 weeks post ORIF and range of motion initiated.
A, B: Severe open elbow injury with substantial articular injury. Stability was maintained with an elbow-spanning fixator before and after definitive surgery. Fixator was removed 3 weeks post ORIF and range of motion initiated.
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In select severe elbow injuries which undergo internal fixation, the stability can be augmented by the application of a hinge-type elbow fixator or a static elbow-spanning fixator. The use of a hinged external fixator for supplemental fixation of distal humerus fractures may be effective in cases where internal fixation is severely compromised by comminution, bone loss, or in conjunction with an unstable elbow joint.68 Other indications for application of an elbow hinge fixator are related to elbow instability as the primary pathology. This includes recurrent dislocation or subluxation of the elbow after repair or tenuous fixation of large coronoid fractures because of comminution or osteopenia (Fig. 8-62). The hinge fixator has also been used to augment the reconstruction of bony, capsuloligamentous, and/or musculotendinous stabilizers following open stabilization of the joint. A relative indication for use of an elbow hinge includes providing stability following fascial arthroplasty or debridement for infection, if the debridement destabilizes the elbow (Figs. 8-63 and 8-64).210,242,243,319 
Figure 8-62
 
A, B: Complex fracture/dislocation with residual post-op instability. Hinge fixator applied to provide concentric stability and allow range of motion. C, D: Intra-op images demonstrating the precise nature of positioning the hinge exactly at the center of rotation of the elbow. E, F: A simple elbow fixator hinge attached to humeral and ulnar monolateral fixator components to provide stable range of motion.
A, B: Complex fracture/dislocation with residual post-op instability. Hinge fixator applied to provide concentric stability and allow range of motion. C, D: Intra-op images demonstrating the precise nature of positioning the hinge exactly at the center of rotation of the elbow. E, F: A simple elbow fixator hinge attached to humeral and ulnar monolateral fixator components to provide stable range of motion.
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Figure 8-62
A, B: Complex fracture/dislocation with residual post-op instability. Hinge fixator applied to provide concentric stability and allow range of motion. C, D: Intra-op images demonstrating the precise nature of positioning the hinge exactly at the center of rotation of the elbow. E, F: A simple elbow fixator hinge attached to humeral and ulnar monolateral fixator components to provide stable range of motion.
A, B: Complex fracture/dislocation with residual post-op instability. Hinge fixator applied to provide concentric stability and allow range of motion. C, D: Intra-op images demonstrating the precise nature of positioning the hinge exactly at the center of rotation of the elbow. E, F: A simple elbow fixator hinge attached to humeral and ulnar monolateral fixator components to provide stable range of motion.
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Figure 8-63
Hinge elbow fixator utilized to provide elbow stability and facilitate physical therapy following fascial arthroplasty of the elbow joint.
 
Key to application is the precise location of the center of rotation pin as seen on fluoroscopy.
Key to application is the precise location of the center of rotation pin as seen on fluoroscopy.
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Figure 8-63
Hinge elbow fixator utilized to provide elbow stability and facilitate physical therapy following fascial arthroplasty of the elbow joint.
Key to application is the precise location of the center of rotation pin as seen on fluoroscopy.
Key to application is the precise location of the center of rotation pin as seen on fluoroscopy.
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Figure 8-64
Elbow hinge placed to augment the repair of a chronically dislocated elbow.
 
Hinge assists in providing concentric reduction while the repair heals. Patient is able to continue to perform therapy without fear of redislocation.
Hinge assists in providing concentric reduction while the repair heals. Patient is able to continue to perform therapy without fear of redislocation.
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Figure 8-64
Elbow hinge placed to augment the repair of a chronically dislocated elbow.
Hinge assists in providing concentric reduction while the repair heals. Patient is able to continue to perform therapy without fear of redislocation.
Hinge assists in providing concentric reduction while the repair heals. Patient is able to continue to perform therapy without fear of redislocation.
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One of the difficulties encountered with the use of hinge fixators for the elbow is the ability to precisely position the center of rotation axis pin to accurately reproduce and preserve the concentric motion of the elbow once the fixator is applied. Recent works suggest that compared with the conventional free hand method of axis pin placement for an elbow fixator, two-dimensional guidance from virtual images (computer-assisted navigation) allows a reduction in the number of drilling attempts required. Furthermore, the accuracy in terms of AP angulation and lateral distance from a defined optimal placement is better when compared with that obtained with the conventional technique (Figs. 8-62 to 8-64).83 Many investigators using hinge fixators document the restoration of stability and excellent motion after relocation of a chronic elbow dislocation. Good results have also demonstrated its usefulness as a tool following the reconstruction of acute and chronic elbow instability or instability after fracture-dislocation (Fig. 8-64). 
In some cases of nonunion of the humerus shaft, standard treatment options such as intramedullary nailing or compression plating and bone grafting may not be applicable or recommended, because of lingering infection, severe osteoporosis, poor soft tissue coverage, or other confounding variables. Many authors have advocated a one-stage debridement, with or without autogenous bone grafting, and application of an Ilizarov external fixator. Successful treatment of complex distal humeral and midshaft nonunions that have failed internal fixation have been reported with this technique.37,239,284 

Tibial Fractures

Open tibial diaphyseal fractures are primarily treated with intramedullary nailing, but there are occasions when external fixation is indicated. External fixation is favored when there is significant contamination and severe soft tissue injury or when the fracture configuration extends into the metaphyseal/diaphyseal junction or the joint itself, making intramedullary nailing problematic. In these settings, monolateral external fixation allows for rapid reduction, which also helps to limit the amount of operative time and blood loss. In addition, it is useful in patients with multiple injuries or in the patients where prolonged anesthesia is contraindicated. A simple single or double bar unilateral system allows for independent pin placement, whereas the larger monotube frames facilitate rapid application with fixed pin couples.29,54,82,91,94 
Contemporary simple monolateral fixators have clamps that allow independent adjustments at each pin–bar interface allowing wide variability in pin placement which helps to avoid areas of soft tissue compromise. In general, the most proximal and most distal pins are first inserted as far away from the fracture line as possible and the connecting rod attached. The rod is positioned close to the bone to increase the strength of the system. The intermediate pins can then be inserted using the multiaxial pin fixation clamps as templates with drill sleeves as guides. Upon placement of these two additional pins, the reduction can then be achieved with minimal difficulty (Figs. 8-24 and 8-25). Alternatively, the two proximal pins can be connected by a solitary bar and the two distal pins are connected to a solitary bar. Both proximal and distal bars are then used as reduction tools to manipulate the fracture into alignment. Once reduction has been achieved, an additional bar-to-bar construct between the two fixed pin couples is connected. 
Use of the large monotube fixators facilitate rapid placement of these devices with the fixed pin couple acting as pin templates. Two pins are placed through the fixator pin couple proximal to the fracture and two pins placed through the pin couple distal to the fracture. Care must be taken to allow adequate length of the monotube frame prior to final reduction and tightening of the body (Fig. 8-65). 
Figure 8-65
 
A: Monotube fixator allows rapid reduction and stabilization for complex tibia fractures. Fixed pin connectors act as templates to place proximal pins. B: Distal pins are then applied again through the distal pin clamp. The monotube allows for reduction in all three planes. Once reduction has been achieved the monotube is locked and reduction maintained.
A: Monotube fixator allows rapid reduction and stabilization for complex tibia fractures. Fixed pin connectors act as templates to place proximal pins. B: Distal pins are then applied again through the distal pin clamp. The monotube allows for reduction in all three planes. Once reduction has been achieved the monotube is locked and reduction maintained.
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Figure 8-65
A: Monotube fixator allows rapid reduction and stabilization for complex tibia fractures. Fixed pin connectors act as templates to place proximal pins. B: Distal pins are then applied again through the distal pin clamp. The monotube allows for reduction in all three planes. Once reduction has been achieved the monotube is locked and reduction maintained.
A: Monotube fixator allows rapid reduction and stabilization for complex tibia fractures. Fixed pin connectors act as templates to place proximal pins. B: Distal pins are then applied again through the distal pin clamp. The monotube allows for reduction in all three planes. Once reduction has been achieved the monotube is locked and reduction maintained.
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Most monotube bodies have a very large diameter which limits the amount of shearing, torsional, and bending movements of the fixation construct. Axial compression is achieved by releasing the telescoping mechanism. Dynamic weight bearing is initiated at an early stage once the fracture is deemed stable. In fractures that are highly comminuted, weight bearing is delayed until visible callous is achieved and sufficient stability has been maintained. The telescoping body allows for dynamic axial compression once weight bearing is initiated, and this serves to stimulate early periostel callous formation.1214 
External fixators offer the ability to compress actively across fracture fragments, and fracture gaps secondary to comminution and minimal bone loss can be closed directly by this maneuver. Fracture gaps secondary to malalignment can be corrected sequentially as bone union takes place. This can be accomplished with most circular and select monolateral fixators with three-dimensional adjustability.13,14,220,241 
Closed tibial fractures treated with external fixation heal on an average in 4 to 5 months. In an effort to accelerate this rate, most proponents of external tibial fixation feel that early dynamization or gradual frame disassembly should be performed in an effort to effect load transfer to the fracture and promote secondary callous formation. Research and clinical studies have been inconclusive on the advantages of passive dynamization. However, dynamization does seem to facilitate fracture healing if it is utilized within the first 6 to 8 weeks following the fracture. Kenwright demonstrated significant improvement in the time to union with active dynamization.153155 If a major bone defect exists at the fracture site, dynamization may result in permanent shortening. If more than 1.5 to 2 cm of shortening will occur then dynamization is contraindicated. Most external fixators have bone transport capabilities as an option to regain limb length and skeletal continuity.295,298300,302 
Tibia fractures with severe soft tissue injury may have concomitant foot injuries as well. These patients require multiple reconstructive procedures and are often initially treated with external fixation techniques such as a bridging frame. It is advantageous to extend these frames to the hind and forefoot to avoid the common complication of equinus deformity. This can develop over time specifically in those patients with a wide zone of injury, causing the posterior compartment and other tissues to contract (Figs. 8-29, 8-45, 8-46). 

Small Wire External Fixation

Diaphyseal long bone injuries are best managed using half-pin techniques. This is readily accomplished when the fracture occurs in the mid portion of the long bone, allowing the diaphyseal bone above and below the fracture to be stabilized by half pins which achieve solid bicortical pin purchase. However, as many high-energy fractures involve the tibial metaphyseal regions, transfixion techniques using small tensioned wires are ideally suited to this area, as they demonstrate superior mechanical stability and longevity. The improved stability of these tensioned periarticular wires may eliminate the need to span the ankle or the knee joint. The small tensioned wires may be used in concert with limited open reduction if necessary. Olive wires can be used to achieve and maintain “tension compression fixation” across small metaphyseal fragments, similar to the effect achieved with small lag screws. Therefore, the combination of smooth and olive wires is used to neutralize deforming forces across the fracture lines and also help to achieve and maintain compression across the fracture lines (Fig. 8-66).140 
Figure 8-66
 
A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
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A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
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Figure 8-66
A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
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A: Comminuted pilon fracture with articular and metaphyseal involvement. B–D: Distal ring construct using tensioned smooth and olive wires to stabilize small periarticular fracture fragments at the joint. The zone of injury is spanned with the proximal rings. E: Postframe with articular and metaphyseal healing noted.
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Randomized prospective trails comparing circular external fixation with standard internal fixation for the treatment of bicondylar tibial plateau fractures have demonstrated excellent functional results comparable to traditional open methodologies. The major advantage of circular techniques was the reduction of soft tissue complications and infections that are traditionally associated with open procedures. In contrast to other hybrid techniques, a completely circular frame offers more adjustability and superior resistance to deformation from detrimental mechanical forces such as cantilever bending. The “hybrid” frame has evolved to include a traditional monolateral diaphyseal bar attached to a solitary circular periarticular ring. Full ring stabilization is preferable to monolateral shaft stabilization because of the cantilever loading accentuated with this construct. Specifically in the proximal tibia, this type of frame configuration functions similar to a diving board producing tremendous loads at the metaphyseal diaphyseal junction with the associated development of non- or malunion.46,296,297,299,305,318 If monolateral adaptations are to be used, it is recommended that at least three divergent connecting bars be attached to the periarticular ring.5 The bars should be oriented to achieve at least 270 degrees of separation to alleviate cantilever loading. An additional disadvantage of this “hybrid” construct is the inability to easily dynamize the fixator.236,237,301,311 
Surgical application of a circular hybrid periarticular fixator can be performed with the patient on either a fracture or radiolucent table with calcaneal pin or distal tibial pin traction. Following a ligamentotaxis reduction of the metaphyseal fragments, olive wires or percutaneous small fragment screws can be used to achieve interfragmentary compression of these metaphyseal components. If necessary, limited incisions are used to elevate the depressed articular fragments as well as bone graft the subchondral defects. It has been shown that at least three periarticular wires are necessary to stabilize these injuries. Most authors using small wire techniques recommend that as many wires as can be inserted safely should be used for maximal stability.6,88,289,303 Biomechanical data supports the use of tensioned wire fixation stabilizing complex fractures of the proximal tibia. The stability achieved with a four-wire fixation construct is comparable to that of dual plating for bicondylar tibial plateau fractures.23,297,305 
When utilizing transfixion wires, care should be taken to avoid the proximal tibial capsular reflection and ankle joint capsule to avoid penetrating the capsule.107,289,291 This maintains the wires in an extra-articular location and avoids secondary contamination of the joints which can result in knee or ankle sepsis (Fig. 8-67). 
Figure 8-67
Anatomic specimen showing the capsular reflections around the knee joint.
 
Care must be taken to avoid capsular penetration when placing periarticular wires around the knee. (Courtesy of Spence Reid, MD.)
Care must be taken to avoid capsular penetration when placing periarticular wires around the knee. (Courtesy of Spence Reid, MD.)
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Figure 8-67
Anatomic specimen showing the capsular reflections around the knee joint.
Care must be taken to avoid capsular penetration when placing periarticular wires around the knee. (Courtesy of Spence Reid, MD.)
Care must be taken to avoid capsular penetration when placing periarticular wires around the knee. (Courtesy of Spence Reid, MD.)
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In certain situations a multiplane circular external fixator can be used to prevent further deformity while allowing weight bearing for a neglected diabetic ankle fracture. This technique may also be utilized for the management of complex diabetic ankle fractures that are prone to future complications and possible limb loss (Fig. 8-68).70,91 
Figure 8-68
 
A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
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A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
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Figure 8-68
A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
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A: Bimalleolar ankle fracture with poor soft tissues in a diabetic with early Charcot development. Reduction could not be maintained in a cast or splint. B: A circular frame was used in concert with percutaneous techniques to achieve reduction of the fractures and maintain stability while permitting weight bearing. C: Frame removed at 10 weeks with excellent joint congruency and ankle stability.
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The treatment of tibial metaphyseal injuries has also included the use of monotube ankle bridging and simple monolateral external fixator designs.35,95 These are applied to achieve a distraction reduction across their respective joints, followed by limited ORIF (Figs. 8-69A,B). The advantage of using monotube constructs for either plateau or pilon fractures is that articular fixation is achieved and maintained without the use of small tensioned wires, and the potential for articular contamination is avoided (Fig. 8-69A).236 
Figure 8-69
 
A: Monotube ankle bridging fixator used to provide distraction in combination with limited internal fixation for pilon fractures. B: Limited ORIF of a pilon fracture is carried out while a spanning fixator is in place maintaining the reduction during surgery.
A: Monotube ankle bridging fixator used to provide distraction in combination with limited internal fixation for pilon fractures. B: Limited ORIF of a pilon fracture is carried out while a spanning fixator is in place maintaining the reduction during surgery.
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Figure 8-69
A: Monotube ankle bridging fixator used to provide distraction in combination with limited internal fixation for pilon fractures. B: Limited ORIF of a pilon fracture is carried out while a spanning fixator is in place maintaining the reduction during surgery.
A: Monotube ankle bridging fixator used to provide distraction in combination with limited internal fixation for pilon fractures. B: Limited ORIF of a pilon fracture is carried out while a spanning fixator is in place maintaining the reduction during surgery.
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Bone Transport

Treatment of acute bone loss following severe tibial shaft fractures continues to be a complex reconstructive challenge. Many procedures have been devised to reconstitute bone stock, obtain fracture union, and provide a stable functional limb. Cancellous grafting whether placed directly into the defect or through a posterolateral approach has been the most common methodology; however, often, this technique requires numerous grafting procedures.54,55,282 Fibular bypass, tibial fibular synostosis, ipsilateral direct fibular transfer, as well as free vascularized fibular transfer, have been used to reconstruct these large defects.9,55,82,89 Internal bone transport has been developed as a primary method of bony reconstruction in acute tibial fractures with bone loss. This technique is indicated for reconstruction of defects greater than 4 cm.17,55,69,119,140,148,220,252,295,298,299,302 
Bone transport can be carried out with a modified monotube monolateral fixator that has an intercalary sliding mechanism to transport the bone segment. Similarly, ring fixators can also be configured to perform successful intercalary bone transport. 
The basic transport frame utilizing a ring fixator consists of three rings. A stable proximal and distal ring block is placed and at the level of the knee and ankle joints. A transport ring is placed in the midportion of the tibia. Orientation of the frame on the limb is crucial to ensure that the proposed docking site is aligned and will provide sufficient cortical contact for union to occur. Likewise, appropriate alignment utilizing a monotube construct is also critical to ensure docking site alignment. The intercalary transport component is attached to the bone using either transfixion wires or half-pin techniques. An antibiotic cement spacer is also placed across the defect. This block provides additional stability to the frame–bone construct and acts to maintain the transport space. This is very similar to the Masquelet technique allowing the development of a well-circumscribed soft tissue sleeve through which the transport segment can occur. The block remains in place until the final debridement, free flap procedure, or delayed primary closure of the wound (Figs. 8-70A–C). 
Figure 8-70
 
A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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Figure 8-70
A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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A, B: A transport frame spanning the segmental injury with the defect filled with an antibiotic spacer and the soft tissue deficiency treated with a free flap. The frame is attached to the bone using a combination of transfixion wires or half pins. C: Following flap maturation, the antibiotic spacer is removed and replaced with a small chain of antibiotic beads and a proximal corticotomy is performed. D, E: Transport is initiated using autodistractors. As distraction continues the docking site gradually shortens and compresses the beads. F: At near docking, the beads are removed and bone grafting to the docking site is carried out. G, H: Transport is then continued, fully compressing the graft, achieving a stable docking site. I: The frame was successfully removed without docking site nonunion or late deformity of the regenerate.
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At the time of definitive wound coverage, the antibiotic block spacer is removed and a solitary string of antibiotic cement beads is placed in the defect. The beads provide and maintain a “potential space” or fibrous tunnel through which the transport segment will travel. This space allows relative unencumbered movement of the transport segment underneath the flap. If no flap is needed, the wound is closed primarily and antibiotics beads are still used to maintain the potential space and prevent invagination of the intact soft tissue envelope into the transport pathway (Figs. 8-70D–I).118,119,140,258,298,299,302 In addition, this well-vascularized Masquelet-“like” transport sleeve facilitates the healing of the docking site.281 
If soft tissue coverage is adequate then soft tissue transport in conjunction with the bone transport is possible.55,69,138,139 Tissue loss that exposes bone is not amenable to combined soft tissue–bone transport without first addressing the exposed bone. This is accomplished through rotational or free tissue transfer. Alternatively, the bone should be resected until healthy soft tissue covers the bony segment.198,250,298,299 At this time acute shortening or gradual shortening can be accomplished and the soft tissue defect allowed to heal without additional coverage procedures. Following soft tissue healing, lengthening or deformity correction can then be carried out through the use of the frame. 
Transport is delayed for at least 3 weeks following free flap coverage. This allows for healing of the flap over the bony defect and neovascularization of the zone of injury. The delay also allows the free flap anastomosis site to become fully epithelialized which is then able to withstand the inevitable tension forces that it is subjected to during the bone transport process.140 If no flap is utilized, corticotomy and transport can be undertaken immediately at the time of wound closure. The location of the transport Schanz pins should be in the inferior portion of the transport segment, so that it will “pull” the bone into docking position rather than “push” the transport segment, which occurs if the pins were located more proximally in the transport segment. This construct results in an unstable situation where the transport segment will have a tendency to deviate during transport.118,119,140,299 
Following fixation of the transport segment, a proximal or distal corticotomy is performed. Following open tibial fractures, a wide zone of injury may be present and it is preferred that the corticotomy be performed away from this potentially compromised area. A latency period of 7 to 10 days is allowed prior to the initiation of transport. The initial rate of distraction begins slowly at 0.25 to 0.5 mm per day. A slower distraction rate is recommended initially because of the wide variability in injury patterns and vascularity of the limb. In more extensive fractures with a wide zone of injury, transport should be undertaken very slowly and only after the regenerate bone is visualized approximately 2 to 3 weeks post corticotomy. The distraction rate can then be adjusted depending on the quality of the regenerative bone. Transport in the acute fracture proceeds at a much slower rate, 0.5 to 0.75 mm per day, as opposed to the standard rate of 1 mm a day typical for standard limb lengthening. 
To decrease the transport distance, the limb can be shortened acutely at the time of frame application.55,295,299,302 This shortening aids in soft tissue coverage by decreasing tension and gaps in the soft tissues. Shortening acutely can be accomplished safely for defects up to 3 to 4 cm in the tibia or humerus, and 5 to 7 cm in the femur. In some situations, it is advantageous to decrease the transport distance, and thus patient time, in the frame. Shortening aids in soft tissue coverage by decreasing tension and gaps in the open wound; this approach combined with vacuum-assisted closure (VAC) may allow wounds to be closed by delayed primary closure or healed by secondary intention or simple skin grafting. With this technique, one may avoid extensive free flap coverage.55,69,138,139,209,254,295 
However, acute shortening greater than 4 cm is not recommended because of distortion of the neurovascular elements which results in the development of edema and inability of the musculotendinous units to function properly (Fig. 8-42).295,299,302 Bone transport continues until the antibiotic beads have been compressed to the width of one bead. At this time, the patient is returned to surgery and the docking site exposed. The beads are removed and the bone ends freshened to achieve punctate bleeding surfaces. A high-speed burr can be used to fashion congruent surfaces on the ends of the proposed docking segments. This ensures maximal cortical contact and increases stability at the docking site. Autogenous iliac crest bone graft is placed directly into the docking site at this time and distal transport is resumed within 24 hours of the procedure (Figs. 8-70F–I).55,118,119,295,298300,302 
The docking site is impacted and gradually compressed 0.25 mm every 48 hours until the docking site is radiographically healed. Numerous authors have found that grafting the atrophic docking site aids in the speed of union with a subsequent decrease in the overall time the patient must remain in the fixator.55,118,119,295 Bone transport is a reliable technique; however, it is very time consuming and requires extreme patient compliance. 
Other strategies have been developed to decrease the amount of fixator time the patient must undergo during these arduous reconstructions. Recently, bone segment transport for the treatment of large tibia bone defects was described by applying a locked bridge plate and transporting with a monolateral external fixation frame.109 This technique allows correction of length and alignment, stabilizes the limb, and facilitates earlier frame removal. Rapid distraction is accomplished and once the defect has docked, the opportunity to additionally compress and stabilize the transported segment by additional nonlocking and/or locking screws through the plate is present. This technique has been modified to include rapid transport or lengthening of a limb segment and once the pathology has been corrected, insertion of a locked plate allows earlier removal of the external fixator during consolidation. Plate insertion is accomplished through a clean pin-free zone avoiding contamination, and before frame removal (Fig. 8-71).125,142 
Figure 8-71
 
A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
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A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
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Figure 8-71
A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
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A: Bisphosphonate-related atypical femur fracture with resultant nonunion and 2 inches of shortening following locking screw failure. B: Gradual distraction is carried out following nail removal. Length was re-established slowly over 4 weeks. C: Percutaneous plating was carried out at the end of distraction (LOP [lengthening over plate]) and the frame is removed. D: Healed femur maintained at length with the plate.
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Bone transport over intramedullary nails has also been employed for larger femoral and tibial defects.213,240 The “monorail” technique is similar to transport over plates; however, the ability to compress the docking site is problematic and some authors have advocated applying a small compression plate to this area to avoid transport segment “rebound.” This occurs when the transport segment retracts away from the docking site gradually once the distraction force has been removed. These hybrid transports using internal and external fixation combinations have limited applicability and published results are limited at best. Thus, use of these should be carried out with great caution and under ideal circumstances. The combination of a circular fixator performing transport over a percutaneously applied locking plate demonstrates all the advantages that lengthening/transport over an intramedullary nail provides. However this technique eliminates the concern regarding deep infection that can occur in the medullary canal from the intramedullary nail. It also can be applied to virtually any bone in any age group of patients without any concern with regard to causing avascular necrosis, fat embolism, or physeal injury.142 One should strictly adhere to the principles of transport which include a stable external fixation system above and below the defect, and a biologically sound wound at the transport location. 

Hexapod Fixators

As external fixation devices and techniques have become more sophisticated, the ability to simultaneously correct a complex deformity with a simplistic device has become more attractive. The TSF was designed to allow simultaneous correction in six axes, that is, coronal angulation, translation, sagittal angulation and translation, rotation, and shortening. To achieve this with conventional frames a complex customized frame mounting would be required. In addition, the mounting of these traditional frames would be fairly difficult because of the fact that the rings need to be placed parallel to the respective reference joints, as well as perpendicular to the long axis of the limb. In cases of deformity or fracture, this can be very problematic. The hexapod-type frames allow the rings to be positioned in any orientation within their respective limb segment, that is, above the fracture site. It is not necessary that the rings be parallel with respect to joints or perpendicular to the long axis of the bones. This demanding technique has been vastly simplified using this six-axis “hexapod” concept.262,263 
The hexapod is a ring fixator Ilizarov-type design with a configuration consisting of 6 distractors and 12 ball joints which allows for six degrees of freedom of bone fragment displacement. By adjusting the simple distractors, gradual three-dimensional corrections or acute reductions are possible without the need for complicated frame mechanisms.263 
As a fixation device, it is unique in that deformity correction depends on the use of computer software. Once the rings are mounted, the deformity parameters are calculated with respect to angulation and translation, in both the coronal and sagittal planes. Additional information about rotational and axial malalignment is also entered. These deformity parameters are then placed into the software program along with the frame mounting parameters. The frame mounting parameters include data points such as height of the distance of the frame from the deformity or fracture site location. The overall length of the six struts is also a variable, which is entered into the software calculations. The program will then calculate the final strut lengths necessary to achieve a corrected limb alignment. In addition, daily strut adjustments can also be calculated to affect a very gradual correction over a specific time period that the surgeon wishes to achieve. The final alignment can be further adjusted using the same software applying similar deformity and strut parameters to the program.249 
In the acute application, this frame allows emergent placement of a relatively simple frame. The frame can be attached using either transfixion wires or a minimum of three half pins on either side of the fracture. At this point, an approximate reduction can be achieved grossly at the time of surgery and the final reduction can be completed over a short period of time using the software program and gradual adjustment of the six struts (Figs. 8-72A,B). The hexapod frames and internet software offer the advantage of very accurate and precise control of multiple deformities without significant soft tissue dissection. A relatively straightforward and simple external device is applied to effect these corrections. 
Figure 8-72
 
A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
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A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
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Figure 8-72
A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
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A, B: Complex open distal tibial fracture with large open wound potentially requiring free flap coverage. Acute management included conversion of the spanning fixator to a Taylor Spatial Frame, with intentional shortening and creation of varus deformity, to help achieve primary wound closure. C, D: Once the wound has been stabilized, gradual correction of the induced deformity was gradually carried out. Complete healing of the wound is noted. E: Skin appears normal following frame removal and subsequent follow-up.
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Studies now have documented the hexapod frames’ ability to achieve gradual realignment of complex pediatric fractures, deformities, and complex foot reconstruction procedures.3,86,87,93,99,129,272 Traditional reconstructive surgical approaches involve large, open incisions to remove bone and the use of internal fixation to attempt to fuse dislocated joints. Such operations can result in shortening of the foot and/or incomplete deformity correction, fixation failure, incision healing problems, infection, and the long-term use of casts or braces. The ability to gradually reduce a chronically dislocated ankle or foot deformity in the setting of a severe diabetic and Charcot arthropathy without the need for extensive incisions is advantageous.173 As extensive open reduction can frequently be contraindicated because of local skin conditions and contractures (Fig. 8-68).173 
One can comprehensively approach tibial nonunions with the TSF. This is particularly useful in the setting of stiff hypertrophic nonunion, infection, bone loss, leg length discrepancy (LLD), and poor soft tissue envelope. Investigators have determined that previously infected nonunions have a higher risk of failure than noninfected cases, consistent with most studies on this topic.238,239 What is unique is the hexapod frames’ ability to resolve multiple deformities and restore leg length equality with a relatively simplistic frame application (Fig. 8-73).92,251,254,263,290 
Figure 8-73
 
A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
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A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
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Figure 8-73
A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
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A: Complex tibial nonunion with malrotation, angulation, translation, and leg length discrepancy. B: Taylor Spatial Frame applied to limb using primarily half-pin attachments. Patient self-adjustment of the six oblique struts will gradually correct all deformity parameters. C: Complete realignment and consolidation via gradual distraction osteogenesis, no grafting was required to achieve these results. D, E: Clinical views of Taylor Spatial Frame applied to combined deformities, both consisting of varus, extension, lateral translation, and external rotation.
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Correction of severe tibial deformity because of a nonunion of the tibia can be achieved by slow gradual correction, allowing the compromised tissues to adapt. Studies have demonstrated that patients with either a hypertrophic or oligotrophic nonunion of the tibia with deformity are the best candidates for TSF application. Similarly, patients with three-dimensional deformity and malunion can also be corrected through the use of select corticotomies and gradual distraction with a TSF.251,254 
As noted previously in this chapter, acute shortening with a circular external fixator has been shown to be helpful in the treatment of open tibia fractures with simultaneous bone and soft tissue loss. This is especially true in cases of axial bone transport where longitudinal defects are closed by the soft tissue recruitment that accompanies the transport segment. However, in most cases the soft tissue defect considerably exceeds the bone loss and may require a concomitant soft tissue procedure. There are a number of potential difficulties with vascularized pedicle flaps and free tissue flaps, including anastomotic complications, partial flap necrosis, and flap failure in these cases. With the versatility of the TSF open fractures can be acutely deformed with regard to shortening and angulation to facilitate primary wound closure.209 This limb distortion is temporary and does not require a concomitant soft tissue reconstructive procedure to achieve coverage (Figs. 8-72A,B). Once the wound is healed, the limb deformity and length are gradually corrected by distraction using the Direct Scheduler module of the web-based TSF software (Figs. 8-72C–E). A relatively simplistic (two-ring) frame has been described for the use of these techniques when treating complex tibial shaft fractures with concomitant soft tissue injuries.6 

External Fixator Frame Management

Secondary procedures are frequently required during treatment utilizing external fixators. These may include soft tissue coverage procedures or delayed bone grafting. Most external fixator frames can be easily modified or placed out of the zone of injury. Most surgeons find it problematic to drape the fixator out of the operative field and maintain this unusually small area as sterile throughout an entire procedure. The benefits of safely prepping an external frame into the operative field include the ability to maintain reduction during secondary conversion procedures, and decreasing the time, material cost, and frustration of trying to drape a fixator safely out of the operative field. It has been shown that following a standardized protocol, including precleansing the external fixator frame, followed by an alcohol wash, sequential povidone-iodine prep, paint, and spray with air drying followed by draping the extremity and fixator directly into the operative field, additional surgery can be safely performed without the risk of an increased rate of postoperative wound infection.115,304 It is possible to perform free flaps and other soft tissue procedures directly around the external fixator pins as long as the pins do not communicate directly with the operative site. 

Pin Insertion Technique

The integrity of the pin–bone interface is the critical link in the stability of the external fixation system. External fixation pins placed in cancellous metaphyseal bone frequently loosen with time resulting in fixation failure and increased risk for infection. The fixation pin in cortical/diaphyseal regions can remain intact and infection-free for extended periods of time. Thus each pin in the fixation construct should be continually evaluated for these potential problems to avoid an unstable fixator. The correct insertion technique involves incising the skin directly at the side of pin insertion. Following a generous incision, dissection is carried directly down to bone and the periosteum incised where anatomically feasible. A small Penfield-type elevator is used to gently reflect the periosteum off of the bone at the site of insertion. Extraneous soft tissue tethering and necrosis is avoided by minimizing soft tissue at the site of insertion. A trocar and drill sleeve is advanced directly to bone, minimizing the amount of soft tissue entrapment that might be encountered during predrilling. The drill sleeve should be centered in the midportion of the medullary canal (Figs. 8-74A–D). One needs to ensure that the pin trajectory traverses the near cortex, then the medullary canal, and finally exits the far cortex. In this fashion a transcortical pin, which acts as a stress riser and can be a site of fracture once the frame has been removed, is avoided. A sleeve should also be used if a self-drilling pin is selected. Following predrilling, an appropriate size depth of pin is advanced to achieve bicortical purchase and any offending soft tissue tethering should be released with a small scalpel (Figs. 8-74D–I).115 
Figure 8-74
 
A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
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A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
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Figure 8-74
A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
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A, B: A trocar and drill sleeve is centered on the bone under fluroscopic control to ensure that the pin is not eccentrically located and traverses both cortices as well as bisects the medullary canal. C: The pin must engage the posterior cortex and be central in the bone to avoid postframe stress fracture through an errant transcortical pin tract. Note the central location of the diaphyseal pin. D, E: Following pin insertion there is some degree of soft tissue tethering. Because of this tissue encroachment, hand placement of the pins with a “T” handle limits any soft tissue damage during pin insertion.F, G: The skin can be released using a no. 11 blade scalpel. H, I: The tethering is relieved and a small suture can be used to loosely reapproximate the skin.
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Pin Care

There is no consensus in the literature as to the appropriate regimen for pin tract care and infection prevention. A recent intra-subject, randomized, prospective controlled trial comparing daily pin tract care with no pin tract care was undertaken. Outcome measures evaluated in this study included the pin/skin soft tissue interface integrity, stability of the pins including torsional stability as determined with a torque meter, presence of radiographic pin site osteolysis and presence of pin site pain. There were no statically significant differences between the two groups (pin care to no pin care) when comparing granulation tissue and pin site drainage (36% vs. 35%), pin stability (20 vs. 25 pins with loosening), osteolysis (7 vs. 6 pins), or torque on extraction (mean 0.75 Nm and maximum 3.05 Nm vs. mean 0.6 Nm and maximum 3.55 Nm). This study suggested that specific routine pin tract care is unnecessary as long as daily hygiene for the patient and frame is maintained.46 Thus a universal standard for pin care has yet to be identified. Pin site recommendations are based more often on clinical preference rather than strict research findings.94 It should be noted that correct pin site insertion technique removes most of the factors that cause pin site infection and subsequent pin loosening.8,115,222 If appropriate insertion technique is utilized, the pin sites will completely heal around each individual pin, much like a pierced earring insertion site heals. Once healed, only showering without any other pin cleaning procedures is necessary.307 The occasional removal of a serous crust around the pins using dilute hydrogen peroxide and saline may be beneficial.28,112,116 
In general, recommendations include using normal saline as the cleansing agent in concert with dilute hydrogen peroxide.112,116 A review of the Cochrane database with regard to the most effective pin care regime was performed, and all randomized controlled trials (RCTs) comparing the effect on infection and other complication rates of different methods of cleansing or dressing orthopedic percutaneous pin sites were evaluated. Three trials compared a cleansing regimen with no cleansing, two trials compared cleansing solutions, one trial compared identical pin site care performed daily or weekly, and four trials compared dressings. One of these trials reported that infection rates were lower (9%) with a regimen that included cleansing with half-strength hydrogen peroxide and application of Xeroform dressing when compared with other regimens.180 Additional studies have recommended the use of polyhexamethylene biguanide, silver sulfadiazine, or 10% polyvinylpyrrolidone iodine (Polyod)-impregnated gauze pin wraps to reduce the risk of pin tract infection compared with pin gauze wraps soaked in normal saline.58,65,176,320 However, the authors agree with the conclusions of other investigators that there is insufficient evidence for a single particular strategy of pin site care which minimizes infection rates.85,180 Ointments are not recommended for postcleansing care, as these tend to inhibit the normal skin flora and can lead to superinfection or pin site colonization.189 It is important to remove the buildup of crusted material, which will tend to stiffen the pin–skin interface and increase shear forces at the pin–bone interface (Fig. 8-75A). This leads to the development of additional necrotic tissues and fluid buildup around the pin.58 Immediate postoperative compressive dressing should be applied to the pin sites to stabilize the pin–skin interface and thus minimize pin–skin motion, which can lead to additional necrotic debris. By “training” the skin, the pin site remains stable.140 This allows the skin to heal around the pin undisturbed. Compressive dressings can be removed within 10 days to 2 weeks’ time once the pin sites are healed (Figs. 8-75B,C). If pin drainage does develop, then providing pin care three times per day should be undertaken. This may also involve rewrapping and compressing the offending pin site in an effort to minimize the abnormal pin–skin motion (Figs. 8-12A, 8-75B,C).140 
Figure 8-75
 
A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
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A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
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Figure 8-75
A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
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A: Whereas the pin sites are healing, serous fluid exudes at the pin site and develops crusting which should be removed with mild peroxide or mild soap and water. B: The pin–skin interface should be compressed and stabilized to minimize motion and subsequent development of any necrotic material. Gauze wraps around the pins or pin sponges can be used to provide stabilization following pin site healing. C: Immediate postoperative dressings should include compressive dressings around all pins to compress and stabilize the pin–skin interface. D: Healed pin sites require no special care other than mild soap and water. No ointments or antiseptics are required for the maintenance of a healed/sealed pin site. E: A mildly inflamed pin site with serous type discharge. At long term, these pins can develop painful hypertrophic keratosis surrounding the pin sites and should be excised at the time of pin removal. F, G: Grade IV pin tract infection with seropurulent drainage and redness requires vigorous pin care and antibiotics. H: Grade V pin tract infection with surrounding erythema, inflammation, and purulent drainage. Radiographs of this region must be examined for radiographic signs, suggestive of pin loosening. I: Radiographic evidence of pin sepsis and loosening includes pin sequestrum (white arrow) and cortical lucencies (black circle).
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Review of large pin site registries has documented a significant difference in the rates of pin tract infection between large Schanz half pins and small transfixion wires. For acute fracture fixation fixators, patients with hybrid external fixators demonstrated a similar risk of pin tract infection as patients who had unilateral fixators. The infection rate in the ring fixator (using small transfixion wires) group was significantly lower than the hybrid external and unilateral fixator groups (using primarily Schanz half pins).222 Pin registries evaluating the rates of pin tract infection for limb-lengthening procedures demonstrated similar results. The rate of half-pin site infection was significantly (p < 0.05) higher in half-pin fixators (100%) compared with hybrid fixators (78%) where a combination of thin wire and half pins was used. When half pins were compared exclusively with thin wires, a significantly (p < 0.05) higher incidence of half-pin site infection (78%) over fine-wire site infection (33%) was revealed.8 These findings highlight the need to insert half pins with correct technique (as described above) to avoid excessive soft tissue impingement, incarceration, or development of necrotic tissue at the site of half-pin insertion. In general, it appears that a simple, inexpensive, and patient-friendly plan of pin site care is equal to more complex or costly plans. 

Frame Removal

Definitive treatment with an external fixator demands close scrutiny of radiographs to ensure that the fracture or distraction site has completely healed prior to frame removal. Numerous authors have described various techniques including CT scans, ultrasound, and bone densitometry to determine the adequacy of fracture healing.16,17,140 In general, the patient should be fully weight bearing with a minimal amount of pain noted at the fracture site. The frame should be fully dynamized such that the load is being borne by the patient’s limb rather than by the external fixator (Fig. 8-76). For distraction osteogenesis, radiographs are visualized in the AP and lateral plane. It is necessary to see three out of four neocortices in the regenerate zone reconstituted to ensure that the bone is mechanically stable and able to tolerate frame removal (Fig. 8-77).15,17,118,119 Late deformity following frame removal is very common and usually is the result of incomplete healing of the distraction regenerate.140 In the tibia, this is because the subcutaneous border anteriorly has the least amount of soft tissue coverage, and thus, blood supply. However, mechanical stability requires only three out of four reconstituted cortices. With standard external fixation techniques, similar precautions should be adhered to in order to avoid refracture or the development of nonunion. Multiple x-ray views of the extremity should be obtained to determine the adequacy of fracture healing prior to frame removal. Out of plane ununited fracture lines may be present and may be overlooked if only orthogonal AP and lateral x-rays are obtained to confirm fracture healing. Oblique views should also be obtained in addition to standard views to help identify any residual fracture gaps. 
Figure 8-76
Prior to frame removal all the connecting rods were removed and only the rings remain.
 
The frame has been fully dynamized and the patient allowed to ambulate full weight bearing. The patient is instructed to be aware of any signs of pain or deformity which would indicate incomplete healing. If this occurs, the connecting bars can easily be reapplied and the frame not removed at this time.
The frame has been fully dynamized and the patient allowed to ambulate full weight bearing. The patient is instructed to be aware of any signs of pain or deformity which would indicate incomplete healing. If this occurs, the connecting bars can easily be reapplied and the frame not removed at this time.
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Figure 8-76
Prior to frame removal all the connecting rods were removed and only the rings remain.
The frame has been fully dynamized and the patient allowed to ambulate full weight bearing. The patient is instructed to be aware of any signs of pain or deformity which would indicate incomplete healing. If this occurs, the connecting bars can easily be reapplied and the frame not removed at this time.
The frame has been fully dynamized and the patient allowed to ambulate full weight bearing. The patient is instructed to be aware of any signs of pain or deformity which would indicate incomplete healing. If this occurs, the connecting bars can easily be reapplied and the frame not removed at this time.
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X
Figure 8-77
 
A, B: Reconstitution of both medial and lateral cortices on the AP view, as well as the anterior and posterior cortices on the lateral view, demonstrates complete healing of the regenerate and the fixator can be safely removed at this time.
A, B: Reconstitution of both medial and lateral cortices on the AP view, as well as the anterior and posterior cortices on the lateral view, demonstrates complete healing of the regenerate and the fixator can be safely removed at this time.
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Figure 8-77
A, B: Reconstitution of both medial and lateral cortices on the AP view, as well as the anterior and posterior cortices on the lateral view, demonstrates complete healing of the regenerate and the fixator can be safely removed at this time.
A, B: Reconstitution of both medial and lateral cortices on the AP view, as well as the anterior and posterior cortices on the lateral view, demonstrates complete healing of the regenerate and the fixator can be safely removed at this time.
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X
Ease of frame removal in an outpatient or office setting is variable depending upon the type of fixator pins utilized. A study evaluated the ability to remove stainless steel pin fixators in the office setting without anesthesia. Removal of these particular external fixators without anesthesia was well tolerated by the great majority of patients. Inflammation at pin sites was associated with a higher degree of discomfort during external fixator removal. Despite the higher pain score, most patients with pin site inflammation report that they would repeat the procedure without anesthesia.255 This study confirms the concept that stainless steel pins are usually easily removed; however, newer pin designs including titanium pins, as well as HA-coated pins are more problematic. With the biologic ingrowth nature of these biomaterials, pin removal is often difficult requiring sufficient force to loosen (break) the intact pin–bone interface. This may inflict a significant amount of pain which may preclude this procedure occurring in an office setting.202,206,256 In patients whose treatment time has been prolonged, there is often a large overgrowth of heterotopic pin keratosis which has built up around the pin sites. This can leave an unsightly painful scar if not removed, and therefore should be excised at the time of pin removal (Fig. 8-78). 
Figure 8-78
Hypertrophic pin site keratosis develops around pin sites with long-term fixator applications and should be excised sharply at the time of frame removal to avoid unsightly scarring.
Rockwood-ch008-image078.png
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Frame Reuse

In this era of cost containment for health care, the practice of recycling external fixator components makes economic sense. Dirschl and Smith reported on a single center’s experience with a reuse program. Components in good repair were returned to the operating room stock for reuse, whereas those showing signs of wear were discarded. No component was used more than three times. The institution charged patients a “loaner fee” equal to the hospital’s cost for the inspection, processing, and recycling of fixator components. The mean hospital cost for a fixator decreased 34% as a result of this program. There were no differences in the rates of reoperation or complications before and after institution of the reuse program. No patient had mechanical failure of a new or reused component.72,73,169 Many investigators have evaluated the mechanical properties of recycled fixator components.72,73,136,169 A thorough examination of clinically removed frames, including static mechanical testing, has shown no reduction in performance or catastrophic mechanical failure of recycled parts that showed no visual signs of wear. A recent study from the U.S. Army evaluated reprocessed connecting bars from a commonly used external fixation system. The bending strength and stiffness of these rods was determined using four-point bending testing. The location of rod failure was noted. Testing conditions simulated those utilized by the manufacturer for release of new rods. There was no statistically significant difference in bending strength, but there was a 6% decrease in bending stiffness of the used rods compared with the new rods, the clinical significance of which is unknown. Thirteen total used/refurbished rods broke at locations of previous clamping.244 Thus it is recommended that the rods undergo thorough examination for signs of notching or excessive wear prior to reuse. The potential cost savings, combined with the documented safety of recycled components, makes reuse of these devices attractive. 
August 2000 marked a significant change for hospitals or companies that perform in-house reprocessing of single use medical devices (such as external fixator components) The U.S Food and Drug Administration (FDA) announced new guidelines for hospitals as well as third party reprocessing companies that now holds them to the same rigorous premarket submission requirements as manufacturers. For every device a hospital wants to reprocess, it must submit information to the FDA that demonstrates the safety and effectiveness of that device following reprocessing. This means that hospitals now face tough choices, with a wide range of factors to consider, such as cost liability, quality assurance, and device tracking. Since this ruling went into effect many hospitals have determined that they lack the resources to meet the arduous premarket submission requirements. (510K approval). Hospitals that performed their own reprocessing have been forced to decide whether to continue to recycle at great expense, stop using reprocessed devices, or outsource to a third party preprocessor. Many have decided to outsource the service. 
Reprocessing, whether in-house or by a third party company, can result in cost savings over the purchase price of new fixator components. Data currently suggests that this does not compromise the standard of care or patient outcome. A recent study at Boston University evaluated reuse of reprocessed external fixator frames at the time of removal, for efficacy of function and potential complications.277 The authors found no statistical differences in the incidence of pin tract infections, loss of fixation, or loosening of the components compared to those patients treated with new fixators. Their study demonstrated that this type of reuse program was safe and effective with a potential savings of 25% compared with the cost of all new frames. 
Devices must be tested and recertified prior to redeployment in hospital stock. Horwitz et al.,136 utilizing a conservative pass rate and the assumption of a maximum of three recertifications for each component, calculated the total potential hospital savings on external fixation components when this program was instituted. Components were returned back to the original manufacturer for reprocessing. The first pass rate was 76% for initial reprocessing. The second pass rate (i.e., the rate for components that had already been recertified once and had been sent for a second recertification) was 83%. On the basis of a conservative pass-rate estimate of 75%, the predicted average number of uses of a recyclable component was 2.7. The recertified components were sold back to their institution at 50% of the original price. Because carbon fiber bars and half pins were not recycled, 85% of the charges expended on new external fixation components were spent on portions of the system that were recyclable. The potential total savings on reusable components was found to be 32%, with a total savings of 27% for the whole external fixation system. The investigators noted that no recertified components failed in clinical use over the course of the study. 
These studies demonstrate the real cost savings associated with a manufacturer-based testing and recertification program. However, issues of voluntary participation in reuse programs by the patient as well as informed consent of the use of reprocessed components, component ownership, and the impact of savings on patient charges, still need to be clarified. 

Fixator-Related Complications

Infection

Wire and pin site complications include pin site inflammation, chronic infection, loosening, or metal fatigue failure. Most authors agree that infection rates from external fixation pins have steadily decreased, as pin technology has increased, but are still significant.60 The rates of frank pin tract infection have been based on anecdotal accounts in many studies regarding external fixation. The major problem inherent in all external fixator studies has been the exact definition of an infected pin site. Histologic examination of the tissues surrounding the inflamed pin site might lead to the conclusion that almost every pin tract is infected. The most common wire and pin site complications are now graded by the classification as described by Dahl et al.62 (Table 8-1). 
 
Table 8-1
DAHL Pin Site Classification
View Large
Table 8-1
DAHL Pin Site Classification
Grade Inflammation Drainage X-ray Findings Treatment
0 None or marginal None None Weekly care
1 Marginal inflammation None None Frequent pin care with mild soap or half-strength peroxide
2 Inflamed Serous None Same as for grade 1 plus oral antibiotics
3 Inflamed Purulent None Same as grade 2 treatment
4 Inflamed with induration Seropurulent Osteolysis at near and far cortices Pin removal local wound care
5 Inflamed with induration, tenderness, surrounding erythema Gross purulent drainage Sequestrum and medullary abscess Formal surgical debridement with culture-specific antibiotics
X
The Grade 0 pin site appears normal other than marginal erythema and requires only weekly pin care (Figs. 8-75D, E). 
Grade 1 infection does show marginal inflammation; however, no drainage is apparent and treatment requires more frequent pin care consisting of daily cleansing with mild soap or half-strength peroxide and saline solution. 
Grade 2 pin tract infection consists of an inflamed pin site with serous type discharge. Grade 3 pin tract infections consist of an inflamed pin site with purulent discharge (both grade 2 and grade 3 pin tract infections require placement of the patient on antibiotics and continued daily pin care). 
Grade 4 pin tract infection consists of serous or seropurulent drainage in concert with redness, inflammation, and radiographs demonstrating osteolysis of both the near and far cortices (Figs. 8-75 F,G). Once osteolysis is visible demonstrating bicortical involvement, removal of the offending pin should be carried out immediately. Local soft tissue debridement of the pin tract with peroxide or other astringent irrigant should be performed. Formal surgical management is unnecessary as long as there are no obvious radiolucencies noted on radiographs. 
Grade 5 pin tract inflammation consists of inflamed purulent drainage, osteolysis, as well as sequestrum noted around these abscesses within the medullary canal. Deep-seated infection is present and this requires formal irrigation and debridement procedures with delivery of culture-specific antibiotics (Figs. 8-75H,I). In an effort to avoid collapse of the external fixation construct and the establishment of biomechanical frame instability, pin exchange should be carried out in conjunction with the pin removal process. 

Premature Consolidation and Refracture

In patients undergoing distraction osteogenesis techniques, the problem of premature consolidation is most commonly diagnosed as a failure of the corticotomy site to open and lengthen following initiation of distraction. In most instances, the problem is actually an incomplete osteotomy rather than the premature healing of the osteotomy site.140,295 When this occurs in the tibia, it is often a failure to completely osteotomize the posterior lateral cortex. Most experienced surgeons perform the corticotomy and then manually distract the corticotomy site acutely for 1 to 2 mm under fluoroscopic control to ensure that the corticotomy is complete and can be distracted manually. Using the fixator pins above and below the corticotomy as joysticks, the limb segments can be counterrotated one against the other under fluoroscopy to ensure that a complete osteotomy has occurred.117119,140,295 
Premature consolidation does occur most commonly in a pediatric population where distraction must begin much sooner compared with a mature patient. It is usually because of a prolonged latency period allowing significant callous formation to bridge across the corticotomy site. This is seen clinically as excessive deflection of the wires or half pins with a concomitant lack of a distraction gap on radiographs. If this is recognized early in the treatment phase, continued slow distraction can be carried out until the premature area of consolidation ruptures.140 The patient should be warned, however, that he may feel or hear an audible ache, snap, or pop in the limb with sudden pain and concomitant swelling. Should this occur, the patient should immediately reverse the distraction and compress the region until the pain has subsided. If the patient continues to distract following the fracture of the premature consolidation zone, significant diastasis in the distraction gap will be created causing rupture of the neovascular channels. This may result in the formation of cysts with incomplete regenerate formation and possible regenerate failure.15,16,138140,220 Should the slow distraction fail to achieve disruption of the premature consolidation, the patient should be returned to the operating room where closed manipulation can sometimes be successful in achieving complete corticotomy. Should this fail, a repeat corticotomy should be carried out. 
The most common cause of incomplete regenerate healing includes disruption of the periosteum and soft tissues during corticotomy, too rapid a distraction, and frame instability.15,16,138140 
The rate and rhythm of distraction should be modulated in accordance with the radiographic visualization of the regenerate bone including the formation of the interzone and longitudinal orientation of trabecular bone. Any evidence of disruption or nonlinear orientation of the trabecular bone should be a clear sign that frame instability has occurred. Each pin, wire, and ring connection should be checked and if necessary, additional pins or wires added to assure adequate frame stability. This will help to avoid the formation of intercalary cartilaginous elements. 
Regenerate refracture or late deformity following removal of the apparatus usually presents as a gradual deviation of the limb. This often occurs as a result of the patient and treating surgeon becoming “frame weary,” which results in premature frame removal prior to complete healing of the regenerate or fracture.140 The frame should remain on for an extended period of time to ensure that the fracture has healed. Refracture through a docking site is unusual and is typically the result of incomplete healing. What is more common is fracturing through an osteoporotic stress fracture or through a previous pin or wire hole site. When late deformity or regenerate collapse occurs, this usually leads to an unsatisfactory outcome unless collapse is detected early and the frame reapplied. Untreated, the resulting malunion requires secondary osteotomy procedures. 
Pin- and wire site fracture, as well as docking site or fracture site refractures can usually be treated with a cast if detected early before significant malalignment occurs. However, in complex cases, frame reapplication is required. 

Contractures

Muscle contractures usually result from excessive joint distraction, and occur when elastic tissues and contractile elements cannot accommodate changes in length. This can occur over an extended period of time such as the use of an ankle-bridging monotube fixator, or temporary traveling traction spanning the knee or ankle.269 A common complication when using lower extremity external fixators is the development of equinus contractures of the foot and ankle. To prevent this, spanning the tibial frame to the forefoot in a neutral position can be performed. 
As well, extension contracture of the knee can occur with femoral lengthening or impalement of the quadriceps mechanisms from prolonged monolateral external fixation. Knee flexion exercises to stretch the contracture with physical therapy can be effective but take a prolonged amount of time to work and place increased stress across the patellofemoral joint. An extension contracture can be corrected if manipulated early, utilizing general anesthesia. However, long-standing contracture can be corrected with limited open or formal quadricepsplasty.157 
Contractures result when the resting muscle length becomes relatively short to that of the newly lengthened bone. Thus, tibial lengthening or bone transport can cause flexion contractures at the knee and equinus contractures of the ankle. Measures should be taken to prevent severe muscle contractures when dealing with correction of leg length discrepancy.140 This also occurs during the correction of malunions or nonunions, where, following the deformity correction, relative length is restored. Preventive measures include avoiding transfixion of tendons and maximizing muscle excursion before placing transfixion wires or half pins. Physical therapy throughout the course of treatment is helpful as is splinting and maintaining a plantigrade foot in neutral and the knee in full extension when the patient is at rest. 

Conclusion

The traditional complications of external fixation have been related to the complexity of the external devices, the prolonged treatment times in the frame, and suboptimal outcomes of nonunion, malunion, and pin-related infection. These have largely been eliminated because of advancements in contemporary pin design and frame constructs as a result of innovations in biomaterials and orthobiologics, and an improved understanding of fracture biomechanics. External fixation frames can now remain in place for prolonged periods of time without degradation of the pin–bone interface, and the stiffness of the frames can be adapted to match the clinical demands of the application at hand. Simplified frame mountings have extended the indications for use of these devices, not only for acute fracture management but also for the reconstruction of complex posttraumatic conditions. Advanced technologies such as web-based software interfacing with digital x-rays, uncomplicated frame adjustments, and automated distraction devices can now produce anatomic restoration of limbs that previously could not be achieved with external devices.168 External fixation continues to provide a powerful means to treat a variety of challenging conditions as the ultimate noninvasive tool. 

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