Fracture Treatment with Circular External Fixation

FRACTURE MANAGEMENT AND BONE HEALING

0195-5616/99 $8.00

+ .00

FRACTURE TREATMENT WITH CIRCULAR EXTERNAL FIXATION Denis J. Marcellin-Little, DEDV

Circular external skeletal fixation (CEF) was used in rudimentary forms as early as 400 BC by the Greek Hippocrates. 34 Modern CEF was introduced by the Russian Gavriil Abramovitch Ilizarov in 1951.39 Initially, the frames were limited to rings, connecting rods, and cross-wires transfixing bones. Later on, olive wires, posts, hinges, and washers were introduced and allowed surgeons to apply the frames in closed fashion and to adjust bone fragments after frame application. Over a 40-year period, Ilizarov and his colleagues performed a monumental feat in Kurgan, Siberia by transforming a "log cabin" into an 800bed orthopedic hospital staffed with 350 orthopedic surgeons. Ilizarov is credited with 2000 publications as an author or coauthor. 16 CEF has been used to treat several hundred thousand people in the former Eastern Block countries. The Ilizarov method arrived in the West in the early 1980s and was first used to treat clinical problems of dogs and cats in 1984 by Dr. Antonio Ferretti in Milan, Italy. 5' 12 The Ilizarov method has been used on a limited basis over the years by veterinary orthopedic surgeons in Western Europe, North America, and South America. Clinical reports have been published in dogs/-11, 13, 21 - 25, 28, 29, 35, 40, 41 cats, u horses/1' 19 cattle,11 goats,U and a llama. 37 Today, veterinarians use CEF to treat acute and chronic fractures and deformities, to stabilize joints while maintaining range of motion, and to perform arthrodeses and limb sparing. The Ilizarov method has created interest in the area of small animal orthopedics because of some limitations of conventional surgical methods. Internal fixation with pins and cerclage has the drawback of providing insufficient stability for treatment of comminuted fractures. Internal plate fixation requires an extensive surgical approach, can only be performed on relatively long bone segments, and lacks postoperative adjustability. Linear external skeletal fixation systems also have limited postoperative adjustability. CEF has several significant advantages over these conventional methods,

From the Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina VETERINARY CLINICS OF NORTH AMERICA: SMALL ANIMAL PRACTICE VOLUME 29 • NUMBER 5 • SEPTEMBER 1999

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including the facts that (1) it has excellent mechanical properties (high stiffness when submitted to shear and bending forces and relatively low stiffness when submitted to axial loads), (2) short bone segments (10-15 mm long) can be used for stable fixation with cross-wires and half-pins, and (3) the frames are fully adjustable after bone fixation, allowing acute or progressive translation, rotation, or angulation of bone segments. 27 GENERAL PRINCIPLES OF THE ILIZAROV METHOD

The CEF frames are built using rings connected by threaded rods and nuts (Fig. 1). Theoretically, the frames should have four rings (Fig. 2). The rings should span the length of all bone segments to fix. Practically, rings should be placed "far, near, near, and far" from the fracture site. 38 When the fracture is close to a joint, a single ring may be used to stabilize a bone fragment, and additional fixation with an olive wire, a dropped wire (wire fixed to 2 posts), or a half-pin should be used. The inside edge of the ring should be placed about 10 mm from the skin. Practically, the rings used have an inside diameter of 50 to 120 mm. Partial rings or arches can be used to avoid restricting the range of movement of adjacent joints (Figs. 2 and 3). The simplest CEF frames have rings perpendicular to the connecting rods (see Figs. 2 and 3). These frames have limited postoperative adjustability, especially when correcting angulation. Frame adjustability can be increased using hemispherical washers or hinges. Hemispherical washers make possible the angulation of the rings from a plane perpendicular to the connecting rods up to 6 and 12 degrees for the IMEX ring fixator system (IMEX, Longview, TX) and the Small Bone Fixator (SBF; Hofmann SaS, Monza, Italy), respectively (Fig. 4). Hinged CEF may be used to correct the angular deformity present immediately after closed frame placement or in delayed union and malunion. These hinges can be adjusted immediately after surgery or progressively (Fig. 5). The frames are fixed to the bones with tensioned small-diameter (1.0-1.6mm) wires. Two wires are generally connected to each ring using slotted or cannulated bolts. One wire is placed above and one below the ring to avoid interference as the wires cross each other. Wires can also be connected to posts (see Fig. 3) or to threaded rods using slotted washers (see Fig. 4). The size of the wires depends on the size of the bone fixed and on the size of the patient. In human beings, 1.5-mm diameter wires are used for the long bones of children and 1.8-mm diameter wires are used for the long bones of adults. In dogs, Ferretti recommended using wires with a diameter of 1.0 mm in cats and in dogs weighing less than 10 kg, 1.2 mm in dogs weighing less than 20 kg, and 1.5 mm in heavier dogs.Z7 We have used 1.55-mm diameter wires (0.062-in diamond tip Kirschner wires; Kmedic, Northvale, NJ) to repair comminuted long bone fractures in dogs weighing as much as 70 kg (Fig. 6). Olive wires are specialized wires with a larger diameter ball at their midpoint, preventing movement of the bone in relation to the wire (see Fig. 4). They strengthen the fixation and allow translation of bone fragments when traction is applied on their end. Tension is applied to the wires with a wire tensioner. Ideally, a graduated tensioner (SBF dynamometric wire tensioner; Hofmann SaS) is used to place a consistent tension on the wires (see Fig. 1). The bending stiffness of tensioned wires is significantly higher than the bending stiffness of loose wires. A tensioned 1.6-mm diameter wire has a bending stiffness equivalent to a 4.0mm diameter half-pin. 4 Ferretti recommended placing the following tension when tensioning wires connected to full rings: 20 to 30 kg for dogs weighing 5 Text continued on page 1161

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Figure 1. Components of the small bone fixator (SBF, Hofmann SaS, Monza, Italy). From the top down, the first box holds twisted plates, dynamometric tensioner, nuts, hemispheric washers, wrenches, hinges, telescopic rods, slotted threaded rods, standard threaded rods, triangular nuts, posts, buckles, fixation cubes, and spacers. The second box contains standard wires; olive wires; standard, cannulated, and slotted bolts and 1-mm-thick, 2-mmthick, and slotted washers. The third box holds half-rings. The fourth box contains plates and 5/8th rings. Full rings, rulers, goniometer, and a second tensioner are kept separately.

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Figure 2. Comminuted radial fracture of the radius of a 3-year-old Labrador Retriever. A four-ring frame was placed in closed fashion. A half-pin is connected to the proximal ring with a fixation cube. Four weeks later, the fracture has healed.

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Figure 3. Open, comminuted tibial fracture of the tibia caused by a fan belt in a 1-year-old cat. A three-ring frame was placed in closed fashion. The proximal ring is incomplete to avoiding restricting flexion of the stifle joint. Two weeks later, the animal is weight bearing. The animal is presented for its first re-evaluation 10 weeks later. The fracture has healed.

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Figure 4. Postoperative adjustability of ring fixators used for fracture treatment. A comminuted tibial fracture of the tibia of a 4-year-old mixed-breed dog with a large butterfly fragment has been fixed with a three-ring circular external fixator. An olive wire is attached to the connecting rods using slotted washers (inset). Placing traction on the olive wire helps to reduce the bone fragment. The fragments have been compressed by adjusting the nuts on the connecting rods. The angular deformity has been corrected by adjusting ring orientation with hemispheric washers (inset). Nine weeks later, the fracture has healed.

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Figure 5. Acute correction of an angular deformity. An open, comminuted tibial fracture of a 2-year-old Dalmatian has been repaired with a four-ring frame placed in closed fashion. A 15° varus deformity is present on postoperative radiographs. The deformity is corrected immediately by placing hinges on the frame. The dog is presented for its first re-evaluation 10 weeks later. The fracture has healed. Bone resorption around the wire tracts suggests focal osteomyelitis.

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Figure 6- A radial fracture of a 5-year-old Mastiff is treated with a four-ring frame placed in closed fashion. The dog is weight bearing on the day after surgery. Two positive profile half pins were added to the frame because of wire breakage. Twelve weeks later, the fracture has healed .

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to 10 kg, 30 to 60 kg for dogs weighing 10 to 20 kg, and 60 to 90 kg for dogs weighing more than 20 kg. 27 When wires are connected to posts, connecting rods, or partial rings, their tension should not be greater than 30 kg to avoid frame deformation. Half-pins can be added to the frame to reinforce fixation of short bone fragments. The half-pins are generally connected to the rings of connecting rods with fixation blocks or cubes. These components were not part of the original Ilizarov method; instead, they were designed by Italian and North American surgeons to enhance the frame fixation to the femur, humerus, and short bone fragments. 15 These fixators are called hybrid external skeletal fixators because they blend CEF and linear external skeletal fixation. Fixation cubes are available for the IMEX and SBF frames (see Fig. 2). Cortical positive-profile end-threaded pins are used because they enhance the stability and durability of the boneimplant interface? Because of the particular structure of CEF frames, their mechanical characteristics and the biological response to their placement are unique; they have unique mechanical properties and adjustability, and they are minimally invasive. The bending and torsional stiffness of CEF frames is similar to the bending and torsional stiffness of conventional external skeletal fixation frames. The axial stiffness of CEF frames, however, is significantly less than the axial stiffness of linear external skeletal fixation frames. 14 Consequently, weight bearing creates axial micromotion, which is favorable to bone healing. 20 The CEF frames are easily adjustable during and after surgery (see Figs. 4 and 5, Table 1). These adjustments enable the clinician to move bone fragments, realign the limb, and compress or distract the fracture sites. The Ilizarov method is a minimally invasive form of fracture treatment. Most fractures are treated closed or with a keyhole approach, and the tensioned small-diameter wires are less invasive than conventional external fixation pins.

FRACTURE TREATMENT Indications

CEF has been used successfully to treat acute or chronic fractures, open fractures with or without adjacent joint instability, infected or sterile nonunion, and malunion. Because of the need to place rings around the limbs, they are more adapted to treat problems affecting the distal aspects of the humerus and femur; the radius, ulna and tibia; and the extremities. Even though the fixation of humeral and femoral shaft fractures is possible with the use of arches, fixation cubes, and half-pins, it is generally complex and requires more postoperative management than interlocking nail or plate fixation. CEF is particularly useful to treat fractures involving short bone segments. Three wires or two wires and a positive-profile end-threaded half-pin provide stable fixation of a bone fragment measuring as little as 1 cm3 • CEF may be used to stabilize the unstable joint after shearing injuries. Hinged frames may be used to maintain joint range of motion while protecting healing carpal or tarsal collateral ligaments.'° CEF is also useful to treat potentially infected open fractures, because the minimal tissue trauma occurs at the time of surgery and wound management is not impaired by the presence of the frame. With infected nonunion, the increased osteogenic and vascular activity at the fracture site created by its slow distraction2 or compression may be sufficient to eliminate the infection. Ilizarov reportedly said that he "burned the infection in the flame of the regenerate."2

..... ..... ~

Table 1. COMPONENTS OF CIRCULAR EXTERNAL FIXATORS USED IN SMALL ANIMALS Components

Supporting elements

Connecting elements

Assembly elements

Specific Geometry

Half-ring

40, 50, 60, 70, 80, 90, 100, 110, or 120 mm in ID* 50, 66, 84, or 118 mm in IDt Same as above

%*or%+ ring

Same as above

Arches

%ring+

Plates

2---{), 8, or 10 holes*

Threaded rod Slotted threaded rod Spacer Cannulated bolts Slotted bolt

4, 5,* or 6 mmt in D; 40-200 mm in L 60*+ or lOOt mm in L 20 or 30 mm in L* 8-* or 10-mmt head Same as above

Standard bolt

10- or 16-mm shaft*

Full ring

Use

Standard frame construction Paired to build full rings, can be added onto an existing frame Placed on the flexion side of joints proximally or distally Half-pin fixation to the femur, humerus, mandible, or spine Connect rings of different diameters, build oval rings Connect ring Lock a wire to a moving rod for bone transport Separate rings fixed to short bone fragments Fixation of wires centered over ring holes Fixation of wires offset from the center of ring holes Half-pin fixation, long shaft bolt used for hinge construction

Fixation cubes or clamps Standard nut

2-5-mm pins 5* or 6 mmt in 10

Nylon nuts

6 mm in lOt

Triangular nut Flat washer

Faces have 1, 2, or 3 dots* 1- or 2-mm thickness

Slotted washer* Hemispherical washer Fixation elements

Wire Olive wire Half-pins

Tensioner Wrenches

Dynamometric tensioner* Nongraduated tensionert Flat wrench Box wrench

*Small Bone Fixator (SBF, Hofmann SaS, Monza, Italy). tiMEX ring fixator system (IMEX, Longview, TX). ID = insider diameter; D = diameter; L = length.

~

~

12+-24-degree* range of movement 1, 1.2, or 1.5 mm in 0*; 1.6 mm in Dt, beveled tip Same as above 2-5 mm in 0* 3.2. (0.188 in) or 4.8 (0.125 in) mm in Dt 30-110 kg of tension 8* or 10 mmt Same as above

Half-pin fixation Threaded rod fixation, bolt fixation, hinge construction Nylon absorbs vibrations and prevents frame loosening Marked faces ease frame adjustments Placed between a ring and a wire as needed before wire tensioning Wire fixation to a threaded rod Allow angulation of the ring in relation to the threaded rod Bone fixation Additional bone fixation, fragment transport Fixation of short bone segments, femoral or humeral fixation Place wire tension Bolt and nut tightening Bolt and nut tightening

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Preoperative Planning

The preoperative planning of CEF includes radiographic evaluation of the fractured bone, frame preassembly, and frame assessment on the patient. When making radiographs, it is important to orient the bone perpendicular to the xray beam to have a nondistorted representation of the bone. This is best obtained on a mediolateral radiographic projection of long bones. These radiographs are used as templates for frame preassembly (Fig. 7). The presence of fissure lines should be noted on preoperative radiographs because they may affect frame stability. Olive wires may be used to prevent fissure propagation. Two olives are placed on opposite sides of the bone. The bone segment is compressed when tension is placed on the wires. Frame design includes the choice of ring number, size, type, threaded rod type, number, and location. The frame must be stable enough to allow full weight bearing without restricting the range of motion of adjacent joints (see Fig. 6). This rule established by Ilizarov17 should always be respected. Theoretically, the proximal and distal bone segments should be fixed with four wires (2 wires per ring, 2 rings). When the bone segments are too short to place two rings, a single ring is used, and olive wires may be used. A third wire may be placed on posts or on threaded rods (using slotted washers), or one or two halfpins may be added (using fixation cubes). When a midshaft segmental long bone fracture is treated, a single ring is used to hold the segment. The ring size is chosen so that 1 em separates the skin from the inside edge of the ring all around the limb. Partial rings are placed with their opening on the flexion side of the joints, for example, on the cranial aspect of the elbow joint or the caudal aspect of the stifle joint. The connecting and assembly elements are then chosen. A classic frame is then assembled (see Fig. 7) unless specific difficulties are anticipated. These difficulties include severe limb swelling, multiple fissure lines, and small or soft bones. In these cases, the frames may be assembled during surgery. Hemispherical washers are used when the rings may have to be angled in relation to the connecting rods. These adjustments may be made intraoperatively after the most proximal and distal rings have been placed. After frame preassembly, the frame is placed on the limb of the patient, and the limb is moved throughout a normal range of movement to make sure that the frame is sized properly and does not interfere with limb use. Surgical Placement of the Frame

The leg is clipped and prepared with a routine hanging leg preparation. Traction may be placed on the limb if the fracture segments overlap significantly. For distal femoral and humeral, radial, and tibial fractures as well as for surgery of the extremities, the patient is placed on the operating table in dorsal recumbency, and a metal cable may connect a metal loop attached to the foot to a ceiling hook (see Fig. 7). Traction may be placed on the fracture site by changing the length of the metal cable or by adjusting the height of the surgical table. The preassembled frame is placed around the limb. The most distal wire is generally placed first, followed by the most proximal wire. The other wires on the most proximal and distal rings are then placed. If bone fragment overlap remains, the frame may be adjusted to distract the bone fragments. Most CEF frames are placed in a closed fashion. A handheld fluoroscopy unit or portable x-ray source may be used to evaluate bone alignment during surgery. Also, small-diameter needles (0.5 mm, 25 gauge) may be used to localize the articular margins or

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Figure 7. Comminuted radial fracture in a 1-year-old Labrador Retriever. This dog also had a contralateral glenoid fracture. A paper template of the preoperative radiographs of the radial fracture is used to preassemble the frame. Intraoperatively, the limb is held vertically in extension by a metal cable connected to a ceiling hook (design: Dr. Simon C. Roe). The sterilized preassembled frame is placed on the limb and fixed with eight wires. Five weeks later, the fracture has healed.

the bone ends during surgery. A limited surgical approach is beneficial if the intraoperative reduction is unacceptable. Wire diameter is determined by the weight of the patient: 1.0 mm in cats and in dogs weighing less than 10 kg, 1.2 mm in dogs weighing less than 20 kg, and 1.5 or 1.6 mm in heavier dogs. At least three wires are placed in each bone segment. The wires are placed through safe and hazardous corridors. 30• 31 Half-pins are added, if needed, through safe

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corridors only. Autogenous cancellous bone grafting is not considered to be part of the Ilizarov method. Adjustability

The fracture fragments may be adjusted acutely immediately after surgery or progressively over a period of several days. Acute correction is used to realign fragments when intraoperative reduction is incomplete or when an angular or rotational deformity is present after fracture stabilization. The various components of this deformity can be determined and corrected immediately. Abnormal angulation is corrected by placing hinges or hemispherical washers on the connecting rods (see Fig. 4). Abnormal rotation is corrected by moving the threaded rods by one or more holes on one half of the frame or by using buckles. Abnormal length is corrected by adjusting the nuts on all connecting rods. A bone fragment may also be reduced during or shortly after surgery by curving both ends of the wire running through it, connecting the arched wire to the ring, and tensioning the wire. As the wire straightens, the bone fragment is displaced in a direction perpendicular to the wire. Alternatively, a bone fragment may be moved in a direction parallel to the wire by placing an olive wire through it and then by tensioning the olive wire. 3 Progressive correction may be used to correct fragment position when treating a nonunion fracture, to compress or distract a fracture site to enhance bone healing, or to transport a bone segment. Compression and distraction of the fracture site are used to enhance bone healing. Although compression increases bone stability, distraction dramatically increases local blood flow. 2 When fracture healing is less than optimal, the bone ends may be compressed by a length equal to the fracture gap at a rate of 0.5 mm twice daily. Two or 3 days later, the fracture site may then be distracted at the same rate and length. The process can be repeated a few days later. This "back and forth" displacement has been referred to as bone "gymnastics." Bone transport is the slow progressive displacement of a segment, generally a metaphyseal fragment, in order to form new bone by distraction osteogenesis.33· 43 This method is indicated when a large defect results from bone loss or excision due to infection, neoplasia, or trauma. An osteotomy is performed to free a bone segment. The segment is stabilized by two olive wires placed longitudinally and diagonally and connected to a ring placed on the opposite end of the bone or by tensioned cross-wires connected to a "floating" ring that is moved progressively. Bone transport ends when the segment meets the opposite end of the bone. This is referred to as "docking" the bone segment. The segment is compressed to the docking site to enhance bone healing. The adjustment rate is a function of the distance remaining between the transported segment and the docking site divided by the ring diameter. 3 Bone transport has been used successfully to treat tibial fractures with bone loss in human beings.t, 6, 33 Postoperative Management

The postoperative management of CEF is similar to the postoperative management of linear external fixation systems. A soft padded bandage may be placed around the operated limb for 2 to 3 days after surgery to control edema.

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Bandaging is not necessary after this point, but the frame is generally wrapped or covered with a sleeve to prevent patients from licking the wire-skin interface. Triple antibiotic ointment may be placed daily at the wire-skin interface. Open wounds remaining after stabilization of shearing injuries or open fractures are treated with conventional wet-to-dry or nonadherent bandages. Many patients begin to bear weight within 2 days after surgery. Their exercise is limited to leash walks, but walking is encouraged as it is an excellent form of physical therapy. If the patient does not bear weight after surgery, one should make sure that the CEF frame is not interfering with joint range of motion. Physical therapy may be initiated, including flexion and extension of the adjacent joints, hot packing, and gentle distal-to-proximal finger massage of the edematous areas. Radiographic re-evaluations are scheduled 3 to 4 weeks and 6 to 8 weeks after surgery. Most frames are removed 4 to 8 weeks after placement. Frame removal is performed under sedation. We use oxymorphone combined with acepromazine or medetomidine for sedation. The wires are cut, the half-pins are disconnected from the rings, and the frame is removed from the limb. The wires and wire-skin interface are cleaned and disinfected, and the wires are pulled out with locking pliers. Olive wires must be pulled from the side of the olive. When bone growth around the olive locks the wire, a Jamshidi needle with an internal diameter corresponding to the diameter of the olive may be placed around the wire, and a small core of bone is removed, freeing the olive wire. The limb is not bandaged after frame removal. Activity is restricted for 3 additional weeks. Clinical Results

CEF has been used by veterinary surgeons since 1984 to treat fractures. Few case series, however, have been published. Yves Latte (Grenoble, France) reported the results of the treatment of 14 fractures, 12 nonunions, and 5 malunions/3 and a few additional case reports are available.U' 19• 26, 36 Our clinical results using CEF have been good to excellent. We have treated simple, comminuted, open, and chronic fractures. All fractures have been treated in closed fashion, and cancellous bone grafting was not used. In our experience, fracture union after CEF is achieved 4 to 14 weeks (mean, 8 weeks) after frame placement (Figs. 2-8). Others have reported healing times ranging from 2 to 13 weeks (mean, 7 weeks) and from 5 to 13 weeks (mean, 9 weeks).23· 36 Bone healing is relatively slower when the initial trauma is severe (i.e., gunshot wounds, degloving injuries) or when two-piece fractures are treated (see Fig. 5). Slower fracture healing of severely traumatized limbs is likely secondary to the decrease in blood supply to the affected bone. Slower healing of simple fractures relative to comminuted fractures might be secondary to the differences in interfragmentary strain between two-piece and comminuted fractures. Noncomminuted fractures have high strain at the fracture site, leading to bone death and remodeling before bone union can occur at that site. A similar difference in the bone healing rate of simple and comminuted fractures has been reported after plate fixation. 18 CEF has been used extensively to treat long bone fractures in human beings. Tibial fractures represent about 80% of these cases.'2 CEF is particularly indicated when extensive dissection and internal fixation are contraindicated because of soft tissue trauma, bone stock deficiency, or comminution. 8 Complications

The complications resulting from CEF are similar to the complications associated with linear external fixation systems. These complications have been

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Figure 8- A gunshot tibial fracture of a 2-year-old Labrador Retriever has been treated with three-ring frame placed in closed fashion. The frame was hinged immediately after surgery to correct angular misalignment. Fourteen weeks later, the fracture has healed.

divided into three categories: problems, obstacles, and treatment complications.32 Problems do not necessitate additional surgery and do not affect the outcome. They include self-limiting vascular injuries, skin irritation, pin drainage, and delayed union. Obstacles necessitate additional surgery but do not affect the outcome. They include severe vascular injuries, early wire breakage, and bone fracture. Treatment complications affect the treatment outcome and can be further divided into "minor" and " major" complications. Minor complications include angular deformities, length deficit, temporary denervation, bone infection, and loss of range of motion of adjacent joints. Major complications include malunion after loss of fixation, nonunion, luxation of adjacent joints, and denervation. In our experience, serous and serosanguineous drainage commonly occurs at the wire-skin interface, especially around the proximal wires. Wire breakage is rare and usually reflects a lack of frame stability. Complications are uncommon when fractures are treated with CEF. 28• 29 References 1. Aronson J: Cavitary osteomyelitis treated by fragmentary cortical bone tran sportation. Clin Orthop 280:153, 1992 2. Aronson J: Temporal and spatial increases in blood flow during distraction osteogenesis. Clin Orthop 301:124, 1994 3. Aronson J, Johnson E, Harp JH: Local bone transportation for treatment of intercalary defects by the Ilizarov technique. Biomechanical and clinical considerations. Clin Orthop 243:71, 1989 4. Aronson J, Harrison B, Boyd CM, et al: Mechanical induction of osteogenesis: The importance of pin rigidity. J Pediatr Orthop 8:396, 1988 5. Bianchi Maiocchi A: Historical review of the m ethod according to Ilizarov: 15 years after its worldwide application. Bull Hosp Jt Dis 56:16, 1997

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6. Cattaneo R, Catagni M, Johnson EE: The treatment of infected nonunions and segmental defects of the tibia by the methods of llizarov. Clin Orthop 280:143, 1992 7. Clary EM, Roe SC: Enhancing external skeletal fixation pin performance: Consideration of the pin-bone interface. Vet Camp Orthop Traumatol 8:1, 1995 8. Dendrinos GK, Kontos S, Katsenis D, et al: Treatment of high-energy tibial plateau fractures by the Ilizarov circular fixator. J Bone Joint Surg Br 78:710, 1996 9. Dyce J: What is your diagnosis? J Small Anim Pract 35:4, 1994 10. Elkins AD, Morandi M, Zemba M: Distraction osteogenesis in the dog using the llizarov external ring fixator. JAm Anim Hasp Assoc 29:419, 1993 11. Ferretti A: The application of the llizarov technique to veterinary medicine. In Bianchi Maiocchi A, Aronson J (eds): Operative Principles of llizarov. Baltimore, Williams & Wilkins, 1991, p 563 12. Ferretti A: Small bone fixator. In Bianchi Maiocchi A (ed): Advances in Ilizarov Apparatus Assembly. Milan, Medicalplastic 1994, p 134 13. Ferretti A, Faranda C, Monelli M: 11 metoda di Ilizarov: Un nuovo trattamento delle deviazioni e della dismetria del radio e ulna. Veterinaria 1:57, 1987 14. Fleming B, Paley D, Kristiansen T, et al: A biomechanical analysis of the Ilizarov external fixator. Clin Orthop 241:95, 1989 15. Green SA: The Ilizarov method: Rancho technique. Orthop Clin North Am 22:677, 1991 16. Green SA: llizarov method [editorial; comment]. Clin Orthop 280:2, 1992 17. Ilizarov GA: The tension-stress effect on the genesis and growth of tissues. Part II. The influence of the rate and frequency of distraction. Clin Orthop 239:263, 1989 18. Johnson AL, Smith CW, Shaeffer DJ: Fragment reconstruction and bone plate fixation versus bridging plate fixation for treating highly comminuted femoral fractures in dogs: 35 cases (1987-1997). JAVMA 213:1157, 1998 19. Jukema GN, Settner M, Dunkelmann G, et al: High stability of the llizarov ring fixator in a metacarpal fracture of an Arabian foal. Arch Orthop Trauma Surg 116:287, 1997 20. Kenwright J, Richardson JB, Cunningham JL, et al: Axial movement and tibial fractures. A controlled randomised trial of treatment. J Bone Joint Surg Br 73:654, 1991 21. Langley-Hobbs SJ, Carmichael S, Pead MJ, et al: Management of antebrachial deformity and shortening secondary to a synostosis in a dog. J Small Anim Pract 37:359, 1996 22. Latte Y: Application de la methode d'llizarov en chirurgie orthopedique veterinaire. Pratique Medicale et Chirurgicale de l'Animal de Compagnie 29:545, 1994 23. Latte Y: Bilan de 75 applications de la methode d'Ilizarov: deuxieme partie. Pratique Medicale et Chirurgicale del'Animal de Compagnie 30:141, 1995 24. Latte Y: A specific vet Ilizarov apparatus for the treatment of fractures, delayed union, non union and mal union [abstract]. In Proceedings of the Veterinary Orthopedic Society, Snowmass, CO, 1991, p 51 25. Latte Y: Studies of 63 cases treated by llizarov apparatus: Indications, results, complications [abstract]. In Proceedings of the Veterinary Orthopedic Society, Lake Louise, Alberta, Canada, 1993, p 12 26. Lesser AS: Segmental bone transport for the treatment of bone deficits. J Am Anim Hasp Assoc 30:322, 1994 27. Lewis DD, Bronson DG, Samchukov ML, et al: Biomechanics of circular external skeletal fixation. Vet Surg 27:454, 1998 28. Marcellin-Little DJ, Ferretti A: Improving bone healing with the circular external fixation method. Vet Forum 14:40, 1997 29. Marcellin-Little DJ, Ferretti A, Roe SC, et al: Hinged Dizarov external fixation for correction of antebrachial deformities. Vet Surg 27:231, 1998 30. Marti JM, Miller A: Delimitation of safe corridors for the insertion of external fixator pins in the dog. 1: Hindlimb. J Small Anim Pract 35:16, 1994 31. Marti JM, Miller A: Delimitation of safe corridors for the insertion of external fixator pins in the dog. 2: Forelimb. J Small Anim Pract 35:78, 1994 32. Paley D: Problems, obstacles, and complications of limb lengthening by the Ilizarov technique. Clin Orthop 250:81, 1990 33. Paley D, Catagni MA, Argnani F, et al: llizarov treatment of tibial nonunions with bone loss. Clin Orthop 241:146, 1989 34. Peltier LF: An abridged report on external skeletal fixation. Clin Orthop 241:3, 1989

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35. Poy N, DeCamp CE, DeJardin L: Acute angular correction and distraction osteogenesis 36.

37. 38. 39. 40.

41. 42. 43.

for distal radial physeal closure in seven dogs [abstract]. In Proceedings of the Veterinary Orthopedic Society, Snowmass, CO, 1998, p 48 Radasch RM, McDonald DE, Lewis DO, et al: Management of comminuted radius/ ulna fractures using circular external fixators in the dog: Technique and preliminary results [abstract]. In Proceedings of the Veterinary Orthopedic Society, Big Sky, MT, 1997, p 37 Rohde C, Anderson DE, Silveira F, et al: Surgical stabilization of congenital subluxation in a young llama using a ring fixator [abstract]. In Proceedings of the Veterinary Orthopedic Society, Snowmass, CO, 1998, p 2 Schwartsman V, Schwartsman R: Techniques of fracture reduction: The Ilizarov method. Techniques in Orthopaedics 5:53, 1990 Shevtsov VI: Professor G.A. Ilizarov's contribution to the method of transosseous osteosynthesis. Bull Hosp Jt Dis 56:11, 1997 Smith DA: The use of hinged circular external fixators for tarsocrural instability [abstract]. In Proceedings of the Veterinary Orthopedic Society, Snowmass, CO, 1998, p 21 Thommasini MD, Betts CW: Use of the "Ilizarov" external fixator in a dog. Vet Comp Orthop Traumatol 4:70, 1991 Tucker HL, Kendra JC, Kinnebrew TE: Management of unstable open and closed tibial fractures using the Ilizarov method. Clin Orthop 280:125, 1992 Welch RD, Lewis DO: Distraction osteogenesis. Vet Clin North Am Small Anim Pract 29:1171-1189, 1999

Address reprint requests to Denis J. Marcellin-Little, DEDV NCSU /CVM/DOCS 4700 Hillsborough Street Raleigh, NC 27606 e-mail: [email protected]