Key points

Introduction and history of external fixation for fracture management

Modern fracture care routinely involves the use of external fixation to achieve initial fracture stability with minimal adverse impact on the soft tissues in preparation for definitive management by internal fixation. Although less frequently used, external fixation has an often underappreciated role in definitive management of fractures, both diaphyseal and articular. These injuries are typically high energy in nature, where the soft tissue envelope is in a particularly vulnerable state and must be protected from further insult. Similarly, injuries in which segmental bone loss prevents the use of conventional internal fixation, definitive external fixation with distraction osteogenesis may be used. Although definitive management of fractures with external fixation in the modern era of orthopedic surgery is the exception rather than the rule, methods used today are the result of many years of external fixation development.

Although the concept of external fixation had been in use for hundreds of years, Jean Francois Malgaigne, a professor of surgery at University of Paris published advancements in both the concept of indirect fracture reduction and fracture stabilization through external fixation in the mid 1800s. His device designs, the pointe métallique and griffe métallique, are considered by many as the forerunners of modern external fixator design.

Surgeons continued to improve on technology and develop new fixators through the nineteenth century, but Clayton Parkhill is credited for the first true uniplanar external fixator. In 1897 he reported on his then novel method of reducing and immobilizing fractures by placing 2 threaded pins above the fracture and 2 below, and connecting them with a set of steel wings and clamps. He went on to publish a series of 14 patients all treated with this method, reporting a 100% rate of union. In 1902 in Antwerp, Belgium, Albin Lambotte reported on a similar unilateral design. These designs were popularized and subsequently improved on through the twentieth century to evolve into what we now know as the unilateral external fixator.

In the mid-1900s, Raoul Hoffman of Geneva, Switzerland, published several articles detailing his design innovations for external fixation, which used adjustable pin-to-bar clamps that, by virtue of sliding up or down the bar, could be used for gross adjustment of fracture angulation and length. His design became the first widely used form of external fixation in North America after the Committee on Fractures and Traumatic Surgery of the American Academy of Orthopedic Surgeons designated it as a useful adjunct to fracture management.

Although unilateral external fixation methods were being improved on throughout Europe and North America in the mid to late twentieth century, developments that would revolutionize our understanding of external fixation from the biomechanics and basic science to deformity, infection, and fracture management were simultaneously under way in Siberia.

The development of circular fixation for the treatment of periarticular and long bone fractures was developed and refined by Gavril A. Ilizarov in Kurgan, Russia. He trained at the Soviet Crimean Medical Institute School of Medicine in Ukraine, and then posted to remote Siberia where he was inundated with many injured World War II veterans. Despite a lack of orthopedic training, Ilizarov treated many war veterans with fractures, malunions, nonunions and infections. As the sole practitioner in a remote and isolated region, improvisation led to innovation and discoveries that are now foundational to our understanding of circular fixation and its wide breadth of applications. His design of crossed fine transosseous wires tensioned to rings above and below a fracture allowed immediate full weight bearing, protecting against shear forces at the fracture while promoting axial loading at the fracture to enhance healing. It specifically allowed for quicker return of limb function and joint mobilization, which Ilizarov felt was essential to promoting limb healing. Also credited to Dr Ilizarov is the concept of distraction osteogenesis, a discovery that has established a subfield within orthopedic surgery.

Most of his work was confined to Siberia until 1968. He then assumed treatment for Valerie Brumel, a national hero and Olympic gold medalist in the high jump who suffered a tibial fracture in a motorcycle accident. He was treated with plate and screw fixation by using early A-O technique and developed an infected nonunion with 2 inches of shortening. On Brumel’s return to Moscow after completion of treatment with Ilizarov, he was able to return to competition. Ilizarov and his methods rapidly gained national attention in the Soviet Union. In 1978 he won the Lenin prize for Medicine in the Soviet Union for his work with circular fixation, bone regeneration, and fracture healing.

Ilizarov’s method stagnated behind “The Iron Curtain” until 1980 when Carlo Mauri, a famous Italian explorer, learned of Ilizarov’s method during his participation in the Ra Expedition. Mauri had suffered a tibial fracture 10 years prior in a mountaineering accident and was left with a nonunion that had failed all conventional treatments. He went to Kurgan and attained full union of his fracture with Ilizarov’s method of circular external fixation. This one event opened up the methods of fine wire external fixation to the Western world, as Mauri’s physicians from Lecco, Italy, traveled to Kurgan to learn Ilizarov’s methods.

In 1982, the Soviet Union opened a hospital dedicated to performing Ilizarov’s work in Kurgan. It was a 1000-bed orthopedic hospital, which at that time was the largest orthopedic hospital in the world.

The use of circular external fixation and Ilizarov’s methods did not make headway into North America until the later half of the 1980s. A group of surgeons began experimenting with its use in pediatric applications, as well as nonunions, malunions, and limb length inequality. Small groups of American surgeons went to Kurgan in the late 1980s to learn from Ilizarov with the last organized group from America visiting Kurgan in 1989 while the institute was still under Ilizarov’s leadership. Ilizarov passed away in 1992. Surgeons throughout the world continue to advance his methods, making it a more conventional mode of fracture management, along with standard techniques of internal fixation. The refined techniques of external fixation are now part of an orthopedic traumatologist’s armamentarium. New concepts and designs continue to evolve, enhancing our ability to treat both simple and complex fractures, all while minimizing insult to the soft tissue envelop.

Introduction and history of external fixation for fracture management

Modern fracture care routinely involves the use of external fixation to achieve initial fracture stability with minimal adverse impact on the soft tissues in preparation for definitive management by internal fixation. Although less frequently used, external fixation has an often underappreciated role in definitive management of fractures, both diaphyseal and articular. These injuries are typically high energy in nature, where the soft tissue envelope is in a particularly vulnerable state and must be protected from further insult. Similarly, injuries in which segmental bone loss prevents the use of conventional internal fixation, definitive external fixation with distraction osteogenesis may be used. Although definitive management of fractures with external fixation in the modern era of orthopedic surgery is the exception rather than the rule, methods used today are the result of many years of external fixation development.

Although the concept of external fixation had been in use for hundreds of years, Jean Francois Malgaigne, a professor of surgery at University of Paris published advancements in both the concept of indirect fracture reduction and fracture stabilization through external fixation in the mid 1800s. His device designs, the pointe métallique and griffe métallique, are considered by many as the forerunners of modern external fixator design.

Surgeons continued to improve on technology and develop new fixators through the nineteenth century, but Clayton Parkhill is credited for the first true uniplanar external fixator. In 1897 he reported on his then novel method of reducing and immobilizing fractures by placing 2 threaded pins above the fracture and 2 below, and connecting them with a set of steel wings and clamps. He went on to publish a series of 14 patients all treated with this method, reporting a 100% rate of union. In 1902 in Antwerp, Belgium, Albin Lambotte reported on a similar unilateral design. These designs were popularized and subsequently improved on through the twentieth century to evolve into what we now know as the unilateral external fixator.

In the mid-1900s, Raoul Hoffman of Geneva, Switzerland, published several articles detailing his design innovations for external fixation, which used adjustable pin-to-bar clamps that, by virtue of sliding up or down the bar, could be used for gross adjustment of fracture angulation and length. His design became the first widely used form of external fixation in North America after the Committee on Fractures and Traumatic Surgery of the American Academy of Orthopedic Surgeons designated it as a useful adjunct to fracture management.

Although unilateral external fixation methods were being improved on throughout Europe and North America in the mid to late twentieth century, developments that would revolutionize our understanding of external fixation from the biomechanics and basic science to deformity, infection, and fracture management were simultaneously under way in Siberia.

The development of circular fixation for the treatment of periarticular and long bone fractures was developed and refined by Gavril A. Ilizarov in Kurgan, Russia. He trained at the Soviet Crimean Medical Institute School of Medicine in Ukraine, and then posted to remote Siberia where he was inundated with many injured World War II veterans. Despite a lack of orthopedic training, Ilizarov treated many war veterans with fractures, malunions, nonunions and infections. As the sole practitioner in a remote and isolated region, improvisation led to innovation and discoveries that are now foundational to our understanding of circular fixation and its wide breadth of applications. His design of crossed fine transosseous wires tensioned to rings above and below a fracture allowed immediate full weight bearing, protecting against shear forces at the fracture while promoting axial loading at the fracture to enhance healing. It specifically allowed for quicker return of limb function and joint mobilization, which Ilizarov felt was essential to promoting limb healing. Also credited to Dr Ilizarov is the concept of distraction osteogenesis, a discovery that has established a subfield within orthopedic surgery.

Most of his work was confined to Siberia until 1968. He then assumed treatment for Valerie Brumel, a national hero and Olympic gold medalist in the high jump who suffered a tibial fracture in a motorcycle accident. He was treated with plate and screw fixation by using early A-O technique and developed an infected nonunion with 2 inches of shortening. On Brumel’s return to Moscow after completion of treatment with Ilizarov, he was able to return to competition. Ilizarov and his methods rapidly gained national attention in the Soviet Union. In 1978 he won the Lenin prize for Medicine in the Soviet Union for his work with circular fixation, bone regeneration, and fracture healing.

Ilizarov’s method stagnated behind “The Iron Curtain” until 1980 when Carlo Mauri, a famous Italian explorer, learned of Ilizarov’s method during his participation in the Ra Expedition. Mauri had suffered a tibial fracture 10 years prior in a mountaineering accident and was left with a nonunion that had failed all conventional treatments. He went to Kurgan and attained full union of his fracture with Ilizarov’s method of circular external fixation. This one event opened up the methods of fine wire external fixation to the Western world, as Mauri’s physicians from Lecco, Italy, traveled to Kurgan to learn Ilizarov’s methods.

In 1982, the Soviet Union opened a hospital dedicated to performing Ilizarov’s work in Kurgan. It was a 1000-bed orthopedic hospital, which at that time was the largest orthopedic hospital in the world.

The use of circular external fixation and Ilizarov’s methods did not make headway into North America until the later half of the 1980s. A group of surgeons began experimenting with its use in pediatric applications, as well as nonunions, malunions, and limb length inequality. Small groups of American surgeons went to Kurgan in the late 1980s to learn from Ilizarov with the last organized group from America visiting Kurgan in 1989 while the institute was still under Ilizarov’s leadership. Ilizarov passed away in 1992. Surgeons throughout the world continue to advance his methods, making it a more conventional mode of fracture management, along with standard techniques of internal fixation. The refined techniques of external fixation are now part of an orthopedic traumatologist’s armamentarium. New concepts and designs continue to evolve, enhancing our ability to treat both simple and complex fractures, all while minimizing insult to the soft tissue envelop.

Biomechanics of circular fixation versus uniplanar fixation

Although the biomechanics of external fixation have been studied substantially, understanding of the mechanical forces across the bone/fixator interface remain poorly understood. To better understand the biomechanical differences between fixator designs, it is instructive to review the evolution of fixator design with each design’s historical problems.

The first-generation fixator was a unilateral fixator with the classic “A-frame” design ( Fig. 1 ). Although it was effective in stabilizing fractures, there were inherent problems in its use, as not enough emphasis was placed on proper alignment with fragment apposition. A large number of fractures treated with this device went on to nonunion, with the contemporary thinking being the device was excessively rigid. In fact, the fixator was not too rigid; rather, it allowed no axial micromotion while creating excessive shear forces at the fracture site. This lack of axial loading with excessive fracture site shear led to its poor clinical results for definitive fracture care treatment and led to it being labeled a “nonunion maker.”

First-generation “A-frame” external fixator.

The second generation in fixator design was the unilateral fixator, as we know it today, with the classic prototype being the Hoffman external fixator. Advantages of this design included solid body design in some models, as well as the ease of sliding fixation up and down the stabilization unit. It used parallel half pins above and below a fracture site. These designs gained wide popularity and became the workhorses of external fracture stabilization ( Fig. 2 ). Although these fixators worked well for provisional stabilization, they did not provide the proper biomechanical stability necessary to promote appropriate biology for fracture healing. Because of their unilateral design, they were susceptible to shear and torque with axial loading, and displayed significant coronal and sagittal plane bending moment arm to load. This resulted in shear across the fracture site when loading of the limb occurred in any degree of attempted gait. Despite this, it did provide a useful method of fracture stabilization when internal fixation was not appropriate.

Classic unilateral external fixator.

The Ilizarov fixator revolutionized concepts of external fixation and represented the third generation in external fixation and was the first to use tensioned fine wires in a multiplanar design. Until then, the merits of multiplanar fixation were overlooked and not appreciated in fracture care ( Fig. 3 ). The fine-wire design proved advantageous for fixation of periarticular fractures. It allowed for variable axial micromotion with load modification, such that low loads allow greater axial motion, and increasing load results in decreasing axial micromotion. This was termed the “trampoline effect,” such that increasing load continually tightens the wires and their ability to stretch so that resultant axial deformation exponentially decreases. This axial micromotion in a low shear environment has been shown to be advantageous for callus formation and fracture healing.

Schematic of Ilizarov type of external fixation using fine wires under tension and the multiplanar fixation that it resultantly achieved.

In comparing multiplanar circular external fixation to conventional uniplanar external fixation, Duda and colleagues found that for similar applied loads, there was a fourfold decrease in coronal plane deformity and a sevenfold decrease in sagittal plane deformity with the circular fixator as compared with the unilateral fixator. This has been attributed in part to the cantilever phenomenon of the unilateral fixator construct design. In this same study, the investigators also showed a 1.75-fold increase in axial micromotion with the fine-wire circular fixator as compared with the unilateral design. It is this controlled axial micromotion combined with diminution in shear that provides for the beneficial fracture biology environment for healing that is seen in clinical practice.

The fourth generation of external fixation includes a wide range of mobile, hinged unilateral fixators that emerged in the marketplace beginning in the mid 1980s. These are essentially unilateral fixators with design modifications to allow for deformity correction and bone transport ( Fig. 4 ). They were popularized owing to their ease of application as compared with a circular fixator. These designs, in essence, are the incorporation of hinges and moving parts into a unilateral, uniplanar fixator.

Schematic of fourth-generation fixators that are unilateral fixators that could deangulate through hinges, as well as lengthen or shorten bone segments in a controlled fashion.

A fundamental flaw in this generation of fixators is inherent in the basic biomechanical limitations of standard unilateral fixation, principally the excessive shear and bending forces at the fracture site. This led to the limited success of these fixators in clinical practice, particularly in deformity correction and distraction osteogenesis. Their popularity was mainly market-driven owing to their ease of application.

The fifth generation of external fixator are those as prototyped by the Taylor Spatial Frame. This fixator is a circular multiplanar external fixator that can correct in all planes in 3-dimensional space simultaneously. To achieve this, the design allows 6 points of correction; hence, the 6 struts. Additionally, these designs have the advantage of a software system to aid in deformity analysis and correction.

With the introduction of hybrid external fixation a decade and a half ago, more was elucidated about the biomechanical properties of both unilateral and multiplanar designs. Initially, this design was used in the treatment of complex tibial plateau fractures with diaphyseal extension. In this method, a ring fixator was used to fix the articular segment and attached to the diaphysis with bars leading to a conventional unilateral parallel half-pin design ( Fig. 5 ). A high nonunion rate was observed with this technique and it has since been abandoned in modern fracture care. The additive effect of 2 distinct attributes of each form of external fixation at the 2 fixation blocks is responsible for its failure. At the diaphyseal level, unilateral fixation generates higher shear forces and torque. At the epiphyseal/metaphyseal level, fine wire fixation allows for higher axial micromotion. This axial micromotion magnifies the shear and torque seen at the fracture site from the unilateral fixation, creating an unfavorable environment for fracture healing.

Schematic of hybrid external fixation. This led to exaggerated shear due to the axial micromotion of the fine wire fixation combined with the torque and shear from the unilateral shaft component of fixation.

With regard to biomechanical stability of circular external fixation, Lowenberg and colleagues showed that the fracture obliquity has a direct bearing on the overall bone-frame construct stability. They found that progressive fracture obliquity led to greater shear. They concluded that fracture obliquity over 30° led to shear becoming a dominant factor with physiologic fracture loading. This could be modified with changes in frame construction and design by adding additional forms of fixation to include arced wires and steerage pins. Lenarz and colleagues, in the same journal, found that the incorporation of 3 divergent half pins for diaphyseal fixation, with divergence angles at 60° in 3-dimensional space, was at least as stable and resistant to shear as any other more involved fixation construct. This information has helped changed the way fixation is performed in the tibia.

Indications for circular ex fix versus internal fixation methods

Although modern techniques and implant design continue to improve, there still remains a subset of fractures that are more amenable to definitive treatment with external fixation devices. General factors to consider when evaluating the use of internal fixation methods versus circular external fixation as definitive management include (1) overall risk/benefit of each method, (2) surgeon experience and training, and (3) the ability to predict and treat possible complications of the selected method. One must also not forget that psychological tolerance and compliance are vastly different from patient to patient and must not be left out of the decision-making process.

Although indications and use of circular external fixation differ from surgeon to surgeon, all would agree that the use of these devices is best in high-energy lower extremity injuries with significant bone loss or soft tissue compromise.

These complex injuries are often devoid of significant soft tissue, making soft tissue dissection for internal fixation a problem.

A review of the literature reveals extensive support for circular external fixation for intra-articular and extra-articular fractures of the tibia. The tibial soft tissue sleeve is limited and often disrupted in high-energy injuries. There is often also significant segmental bone loss in these injuries. Circular fixation devices or even minimal internal fixation with circular frames have been shown to provide adequate outcomes in these problem fracture patterns. In cases of significant diaphyseal bone loss, circular frames can be used to provide initial shortening and soft tissue closure with the plan to later restore length through distraction osteogenesis. This technique was described by Ilizarov in 1969, and Green and colleagues found relatively good outcomes in patients treated with this method. Of the 17 patients treated, Green and colleagues had union rate of 94%. They did note, however, that this technique is not without its complications; most commonly wire site infections and frame loosening. Although wire site infection continues to pose a problem, frame loosening is no longer an issue because of our better understanding of the technique. Six patients in this series also required late bone-grafting procedures. Overall, there were no long-term nerve or vessel complications and outcomes for this difficult problem were acceptable. Although complications do exist, circular external fixation with distraction osteogenesis remains a powerful tool for treatment of complicated tibial bone defect injuries.

Although improved implant design, specifically locked plating, has led to improved outcomes of short-segment articular fractures, circular fixators also have been shown to be a powerful tool in treating these fractures. Watson and Coufal showed good results when applying external fixation devices in combination with minimal internal fixation in high-energy atypical tibial plateau fractures. At follow-up, all 14 complex fractures had healed and 85% had good or excellent Knee Society clinical rating scores. Watson and colleagues felt that this combined method showed excellent clinical results without the severe soft tissue complications often seen with extensive surgical exposure and internal fixation. Using the same principle Raikin and Froimson also found 82% excellent or good outcomes on the Knee Society clinical ratings scale. It should, however, be noted that both investigators recognized that this technique is not without complications. Both listed multiple surgeries, delayed union, delayed bone grafting, pin tract infections, and difficulty with patient hygiene as common occurrences. Krupp and colleagues recently published results on treatment of bicondylar tibial plateau fractures using locked plating versus external fixation. Overall, they found average time to union was 6 months for the locked plating group versus 7 months for the external fixation group. Knee stiffness and malunion were significantly higher in the group treated with ringed external fixation. Even in the face of this new technology, Krupp and colleagues felt that use of circular external fixation for tibial plateau fractures was still a viable option in cases of severe soft tissue injury or comminution, as well as in the unstable patient.

For much the same reasons as the proximal tibia, distal tibial fractures also have been treated with circular external fixation devices. Again the soft tissue envelope around the distal tibia is scant and surgical dissection of injuries with already present soft tissue injury is fraught with complications. Raikin and Froimson described the outcomes of these injuries when treated with circular fixators. They found a 90% rate of union at an average of 4.8 months (n = 20). They reported 3 superficial and 2 deep infections and found post healing ankle range of motion averaged 5° of dorsi flexion and 26° of plantar flexion. All patients recovered at least neutral ankle flexion after frame removal and physical therapy. Overall, they reported a 70% excellent or good outcome when treating these difficult fractures with circular external fixation.

Circular external fixation has also been described in the treatment of femoral shaft as well as upper extremity injuries. Most would agree that internal fixation is likely the modality of choice in these locations; however, one should not exclude from their armamentarium external fixation in these locations, especially in the face of severe soft tissue compromise or in the unstable patient.

The use of circular external fixation for the treatment of fractures is still evolving. Today’s improved plate and intramedullary nail designs are designed for minimal soft tissue damage. However, there remains and will always be a use for circular external fixation in those patients in which soft tissue or vascular impairment does not allow significant surgical dissection or in the unstable patient.