The Ilizarov procedure: limb lengthening and its implications.

The Ilizarov Procedure: Limb Lengthening and Its Implications

The purpose of this article is to provide a historical and clinical perspective on the Ilizarov method of external fixation for limb lengthening and deformity correction of the lower extremity. Though relatively new in the United States, the technique has been applied for orthopedic problems with great success for over three decades in Russia and Europe. Physical therapy management is discussed from the preoperative planning phase to removal of the apparatus. [Simard S, Marchant M, Mencio G. The Ilizarov procedure: limb lengthening and its implications. Phys Ther. 1992;72:25-34.]

Key Words: External fixation, Ilizarov procedure, Orthopedics.

The Ilizarov external fixator is a complex combination of metal rings, threaded rods, and Kirschner wires used for the correction of limb deformities, specifically limb-length inequalities. The fixator is used to create an environment in which distraction osteogenesis takes place. Distraction osteogenesis is a form of direct membranous ossification.[1] A fibrovascular lattice spans the two ends of bone that are undergoing distraction and does so without a cartilage intermediary. Bony trabeculae orient longitudinally in the lattice to form a fibrouslike interzone.[1] This interzone is composed of primitive mesenchymal cells that differentiate into osteoblasts, which form the bone. Normally, the process of bone growth is controlled by the growth rates of the physes at each end of the bone, whereas in distraction osteogenesis, the rate of lengthening is controlled mechanically by the external fixator.[1] The Ilizarov device has been recently introduced in the United States and has been used successfully with children,[2] but the device is not limited to pediatric use. This article provides an overview of the history, application, advantages, and complications of the Ilizarov external fixator. The rehabilitation course of patients who undergo this procedure is also described.

History

The Ilizarov method of external fixation originated during World War II when numerous cases of osteomyelitis and bone deformities occurred.[3] In 1943, Professor Gavriil Abramovich Ilizarov developed a transfixion-wire, circular external fixation system using metal rings, wires, and threaded rods with nuts. This fixation system was initially used for stabilizing fractures and managing difficult bone and soft tissue problems. Limb lengthening was not a new concept in the 1940s. Codvilla,[3] in 1905, reported the use of this procedure in the English orthopedic literature. Ilizarov, however, refined the method by which bone and soft tissue could regenerate based on a principle called "tension stress." According to Ilizarov, bone and soft tissue, including skin, muscle, and neurovascular structures, will heal and regenerate in a predictable manner under tension. Ilizarov suggested that, with stable external skeletal fixation, blood supply preservation, and controlled mechanical distraction, new bone would form within an osteotomy site. By inducing tension stress with the circular external fixator, Ilizarov devised numerous strategies for lengthening limbs while simultaneously correcting associated angular and rotational malalignments, transporting bone segments to fill fracture gaps, and healing nonunited fractures.[4,5]

Purpose and Candidate Selection

When Ilizarov developed this technique, its principal goals were to stabilize long-bone fractures, to correct angular deformities, and to minimize limb-length discrepancies. As this technique has evolved, it has been utilized in the management of a variety of other orthopedic conditions, such as joint contractures and pseudarthroses of long bones (whether congenital or acquired), and in the lengthening of vasculature to avoid amputation secondary to peripheral vascular disease.[6] Typical goals of Ilizarov external fixator use with children are to lengthen long bones, to correct angular deformities, to provide fixation for fractures, and to facilitate bone growth at sites of nonunion. This article will focus specifically on lengthening and deformity correction of the long bones in the lower extremity, because this is the most common application of the Ilizarov external fixator to date. Limb-length inequality is a common problem encountered during the growing years and can be caused by a variety of conditions. In the past, poliomyelitis was the most common cause of limb-length inequality[7]; however, the use of prophylactic vaccination has greatly reduced the incidence of poliomyelitis. Today, marked limb-length inequality may result from congenital or developmental abnormalities or from growth arrest of the physes induced by infection or trauma. Malposition of fracture fragments and inflammatory diseases may also contribute to the development of asymmetries. Minor asymmetries between right and left sides are very common; discrepancies from a few millimeters to 2 cm are observed in approximately two thirds of US Army recruits.[7] Limb-length discrepancies greater than 2 cm often result in pelvic obliquity, scoliosis, alterations in normal walking pattern, and abnormal loading of the hip and patellofemoral joints on the long side, with the attendant risks of premature arthrosis.[8] We believe that discrepancies less than 2 cm generally are not clinically significant and do not require surgical treatment. Discrepancies between 2 and 6 cm are usually treated by a procedure to shorten the longer limb. For discrepancies greater than 6 cm, the shorter limb can be lengthened or a combined lengthening and shortening procedure can be performed. In very severe discrepancies, amputation of the deficient limb and prosthetic fitting may be appropriate.[8] Shortening of the longer limb can be achieved by epiphysiodesis, a procedure in which the epiphyseal plates about the knee are surgically obliterated in a skeletally immature patient who has sufficient growth remaining in the shorter limb to accommodate the discrepancy.[8] Alternatively, if there is insufficient growth remaining, the longer limb can be shortened by excising a segment of bone and then stabilizing it with a metal plate or rod.[8] For patients with larger discrepancies (ie, > 6 cm) or those of short stature with lesser discrepancies in whom shortening or epiphysiodesis may not be appropriate, limb lengthening is an option. The advantages of this approach are fairly obvious. By performing a corrective procedure on the abnormal, shorter limb rather than a compensatory procedure on the longer, normal limb, stature is not compromised and body proportions are maintained. The results of limb lengthening can be quite dramatic. Limb lengthening, however, is a much more complex procedure than either the limb-shortening or epiphysiodesis procedure.[9,10]

Surgical Procedure

The basic components of the Ilizarov fixator are smooth and beaded transfixion wires (1.5 or 1.8 mm in diameter), metal rings and arches, threaded rods, and an array of miscellaneous hardware for interconnecting the basic components. The technique for wire insertion includes passing the wire through skin and soft tissue, drilling it through near and far cortices of the bone, and then tapping it through the soft tissue and skin to avoid winding of soft tissue or neurovascular structures around the surgical instrument. The wires are attached to a series of half or full metal rings, which encircle the affected limb, and tensioned to enhance stability. The fixator is completed by connecting the rings with threaded rods aligned colinearly, in the case of straight lengthenings, or at angles by using hinges, if angular deformity correction is planned. The modular design of the system allows for customized assemblage into an almost infinite variety of configurations, making it extremely versatile (Fig. 1).[5,6,11,12] A corticotomy is then performed through the metaphyseal portion of the bone. This is a special type of osteotomy wherein only the cortex of the bone is cut, leaving intact the periosteal and endosteal blood supplies, which are the most important elements responsible for osteogenesis. The corticotomy is accomplished through a 1-cm incision under fluoroscopic guidance, so as to minimally disrupt the soft tissues enveloping the bone.[11] After a latency period of 5 to 10 days, distraction is begun by turning the nuts on the threaded rods 0.25 mm four times per day, resulting in a total lengthening of 1 mm a day (Fig. 2). As the distraction proceeds, osteogenesis occurs within the gap (Fig. 3). When the desired limb length has been achieved, the distraction is stopped, but the fixator is not removed to allow consolidation of the new bone. The consolidation phase is generally double the time span required for limb lengthening. Total treatment time using this method averages about 1 month per centimeter of limb lengthened. Although this procedure may seem somewhat protracted, the patient remains ambulatory throughout treatment, can bear full weight on the extremity, is encouraged to participate in low-impact activities (eg, isokinetic training, stationary bicycling, walking on a treadmill), and may swim.[11,12] Results with this technique can be quite dramatic. Lengthenings of 20% to 30% of the original length of the bone can be achieved (Figs. 4, 5). In contrast to previous methods of limb lengthening (eg, distractional epiphyseolysis, Wagner method, Anderson-Mitchell method), in which bone regeneration was unpredictable and mechanical difficulties with the fixators were common, treatment goals are usually met with the Ilizarov technique and patient satisfaction is almost universal.[13-15]

Advantages

The Ilizarov method has numerous advantages compared with other methods of limb lengthening and deformity correction. First, osteogenesis occurs immediately to bridge the distraction gap. Second, the regenerating bone quickly resembles the already existing bone. Third, the ability to grow new bone exists even in mature bone, making the Ilizarov method effective in adults as well as in children.[2] Another advantage is the modular design of the fixator, which allows each apparatus to be custom-fit for the individual. The use of 1.5- to 1.8-mm pins produces fewer pin-track problems (ie, infection of pin sites) than do conventional methods of limb lengthening, which use larger-diameter (4.5-6.0 mm) half pins. Moreover, the tensioned, smaller-diameter wires are inherently able to withstand dynamic loading of the lengthening segment, which experimentally has been shown to be favorable for fracture gap healing.[16,17] The circular configuration of the frame enhances stability while ensuring that stress is evenly distributed across the corticomy and distraction gap. This biomechanical combination of frame stability and axial elasticity allows for weight bearing throughout the limb-lengthening and consolidation periods while ensuring osteogenesis across the distraction gap.[16,17]

Complications/Problems

Problems, obstacles, and complications that may arise with the Ilizarov technique during limb lengthening include muscle contractures, joint subluxation, axial deviation, neurological or vascular insult, premature consolidation, delayed consolidation, refracture, pin-site infection, and difficulties with psychological adjustment. According to Paley's classification system, problems represent difficulties that do not require operative intervention to resolve and obstacles are difficulties that do require operative intervention. True complications represent intraoperative injuries and all problems not resolved before the end of treatment.[10] In a study conducted by Paley in 1990, 60 limb segments were treated by the Ilizarov method of limb lengthening. From this sample, there were 35 problems, 11 obstacles, and 27 true complications. Despite these problems, obstacles, and complications, the goals of surgery were met in 57 of the 60 limb segments treated.[10] Muscle contractures may occur because of the imbalance between the flexors and extensors on opposite sides of the bone and their resultant inability to accommodate to the distraction of the lengthening limb. Contractures often involve muscles that cross two joints. Range of motion (ROM) may be decreased in all planes of the affected joint. Additionally, there may be significant limitation in one direction because of the overpowering force of a large muscle group. For example, in lengthening of the femur, the hamstrings are the larger muscle group in mass and will therefore offer more resistance to lengthening. Patients with severe muscle contractures 1 year after removal of the fixator may require surgical intervention.[10] Subluxation may occur in a joint that has preexisting instability or unbalanced muscle tension during lengthening. Femoral lengthenings may lead to posterior tibial subluxation secondary to increased stress on the posterior capsule and anterior cruciate ligament from knee hyperextension throughout the stance phase of gait. Patients with joint instability may have the fixator extended to both sides of the joint to prevent subluxation.[10] As the limb is lengthened, there is a potential risk of angular deformity because of a deviation of the lengthened segment. This deformity may be corrected with a modification of the external hardware or of the amount of daily distraction. There is a risk of neurological or vascular injury during surgery or distraction, although the surgical procedure is designed to minimize this type of injury. During limb lengthening, patients who are experiencing extreme pain or who demonstrate signs of vascular compromise may have the amount of daily distraction decreased.[18] Premature consolidation of the lengthening segment may occur before the desired limb length has been achieved, and additional surgical intervention may be necessary. Delayed consolidation may increase the length of time the fixator must be worn. Refracture may also warrant that the fixator remain on for a longer period of time or may indicate the need for additional external support. Pin-site infection may occur because of poor pin-site care by the patient. The infection must be treated promptly to avoid spreading to other pin sites and to avoid osteomyelitis.[10] Children who undergo the Ilizarov procedure require support in adjusting to the discomfort, the care, and the loss of independence experienced after surgery. The frustration, anger, and fear felt by the children may manifest in behavior that is difficult to manage. Intervention by a psychologist for behavior management facilitates appropriate ways of coping and dealing with the child's temporary change in lifestyle.[10]

Physical Therapy Intervention

Preoperative Phase

The preoperative evaluation of a patient who is a candidate for the Ilizarov procedure provides baseline information about the patient's musculoskeletal system and allows for early identification of potential problem areas postoperatively. We believe the preoperative evaluation should include the following:

1. Manual muscle testing of the

upper and lower extremities. In the

upper extremities, all shoulder,

elbow, and wrist motions are

tested in order to help determine

what piece of adaptive equipment

may be the most appropriate for

ambulation postoperatively. In the

lower extremities, all hip, knee,

and ankle motions are tested so

that baseline information is

obtained. This baseline information

is used to predetermine what

areas may need emphasis on

strengthening or stretching during

the rehabilitation process. 2. Assessment of passive ROM of the

upper and lower extremities. This

assessment is performed to obtain

baseline information for

comparison postoperatively. 3. Sensation testing of the lower

extremities. Sensation of the lower

extremities is usually intact to

light touch, deep pressure, and

pinprick tests prior to surgery.

After surgery, there may be

alternation in normal sensation for

reasons that have been explained

previously. This item provides

baseline information for

postoperative comparison. 4. Girth measurements of bilateral

thighs and calves. These

measurements provide baseline data for

determining the amount of edema 

in the limb postsurgically. 5. Measurement of shoe lift and leg-length

discrepancy. These

measurements are used to determine

what height the shoe lift will need

to be after application of the

Ilizarov apparatus. 6. Assessment of joint stability. This

is particularly noted at the knee

joint, where postsurgical

problems most frequently occur. Varus 

and valgus ligamentous stress

tests are performed, as well as

anterior and posterior drawer

tests and the Lachman test. 7. Description of bony deformities.

These deformities are noted

preoperatively so that any effects or

changes that the Ilizarov

apparatus may have on the deformities

may be monitored closely after

surgery. 8. Postural and gait evaluation. A

general assessment of the

patient's postural tone and

observation of gait serve to identify

possible weaknesses in major muscle

groups that will need to be

particularly emphasized during the

rehabilitation phase. 9. Assessment of functional

mobility skills. This assessment

provides baseline data about the

patient's ability to ambulate, to

ascend and descend stairs, and

to move into and out of

different positions. It also identifies

areas that need to be further

developed after surgery. 10. Crutch fitting and instruction in

ambulation, including ascending

and descending stairs with

crutches. This is done so that the

patient will be able to learn these

skills correctly and so that better

carryover is achieved once the

Ilizarov apparatus is in place. 11. Instruction in a home exercise

program. This instruction is

given so that the patient learns

to perform the exercises

correctly and without substitution,

as well as to achieve better

carryover postoperatively. 12. Instruction in postoperative

positioning and splinting. This

instruction is given to improve the

patient's and family's carryover after

surgery. 13. Instruction in stretching and

strengthening exercises to

prepare for surgery. The following

exercises are included: gluteal 

sets, straight leg raising, hip

abduction in a side-lying position,

hip extension in a prone position,

knee flexion in a prone position,

quadriceps femoris muscle sets,

short-arc quadriceps femoris

muscle sets, knee flexion and

extension in a sitting position, ankle

dorsiflexion and plantar flexion,

and passive heelcord stretching

using a towel or Thera-Band [R](*) in

a long-sitting position. The home exercise program for patients who are candidates for the Ilizarov procedure may include various isometric, active, and passive exercises of muscles crossing the joints above and below the segment being lengthened.[18]

Postoperative Phase

Considerations and precautions. Precautions postoperatively may vary among surgeons. Generally, a patient is encouraged to begin activities out of bed on the first or second day after surgery. The patient is allowed to begin active-assistive and isometric exercises of the affected limb the first day after surgery. A patient with a lower-extremity Ilizarov external fixator is allowed to bear as much weight as is tolerated the first day after surgery and may begin progressive gait training 2 to 3 days after surgery.[18] Sterile pin-site care, whereby each pin is individually cleansed with Betadine [R] ([dagger]) solution followed by application of sterile minisponges, is begun on the second day after surgery and is continued for 7 days. The patient may bathe after 8 days, but may not soak the fixator, as this may cause oxidation of the hardware. The patient may swim in a chlorinated pool within 1 to 4 weeks after the surgery, depending on physician preference.[18] Patients are usually hospitalized for 7 to 10 days to ensure limb lengthening is proceeding without complications.

Pre--limb-lengthening stage. Goals of physical therapy management postoperatively are to prevent joint and soft tissue contractures, to decrease pain and edema, to increase ROM of the affected limb, to increase muscle strength, to prevent or minimize gait deviations, and to restore functional mobility and independence. Pain is a major limiting factor the first week after surgery. The use of modalities in conjunction with medication can be useful for pain management. Edema after surgery can be significant; therefore, patients should be encouraged to begin isometric and active-assistive exercise the first day after surgery. Positioning of the extremity to increase ROM is also encouraged immediately postoperatively and may assist in decreasing joint stiffness.

Limb-lengthening stage. Limb lengthening is usually begun 5 days after surgery. The goals in this stage remain the same as those in the postoperative pre-limb-lengthening stage. Patients may experience increased pain or loss of ROM from the distraction placed on the limb. Patients who have significantly limited ROM at this point may benefit from dynamic splinting, which is the application of force-adjustable splints for the purpose of low-intensity, prolonged stretch.[18] Following hospital discharge (ie, 7-10 days postsurgery), physical therapy continues three to five times a week, with emphasis on increasing ROM and muscle strength, monitoring of splinting programs, and monitoring of shoe-lift height for patients with lower-extremity fixators. Physical therapy techniques that have been used throughout Ilizarov rehabilitation include isokinetic exercise, eccentric exercise, passive exercise on isokinetic equipment, stationary bicycling, walking on a treadmill, electrical stimulation, hydrotherapy, massage, and gross motor developmental activities.[18] Patients who develop pin-site infections, severe joint stiffness, or joint contractures may need to be readmitted to the hospital. Patients with joint stiffness or contractures may receive intensive physical therapy, possibly in conjunction with manipulation by the physician, followed by splinting or continuous passive motion exercises.

Consolidation Phase

Goals of physical therapy management after lengthening of the limb is complete are to increase ROM where limited, to increase strength of the affected limb, and to maximize independent function.

Removal of the Fixator

Upon removal of the fixator, the patient's limb may be casted or braced for approximately 1 month to prevent fracture. Goals of physical therapy management during this phase are to maximize ROM, to maximize strength, to eliminate gait deviations for patients with lower-extremity lengthenings, and to restore functional abilities and independence. Orthotic or prosthetic devices worn preoperatively may require refitting, and patients may require retraining with these devices.

Research

The first study of distraction osteogenesis in humans via the Ilizarov technique was reported by Tajana et al[19] in 1989. The purpose of this study was twofold: (1) to describe the development of the extracellular matrix of the bone created by distraction and (2) to determine the time sequence of morphogenesis. Sixty-four human tibial biopsies were taken at various time frames from the onset of distraction, ranging from 10 days to 24 months. The conclusion yielded by this study was that the process of osteogenesis does not occur in a strict sequential manner, but in stages that overlap. The quality of tissue was not that of a typical homogeneous tissue, but that of a discontinuous, unorganized tissue. The most noteworthy finding of this study was that the phases of osteogenesis resultant from distraction follow a differentiation process that does not include the formation of a cartilaginous model; rather, it is ossification of the direct type.[19] Another study, conducted by Connolly et al[20] and reported in 1986, had as its main objective to describe animal and clinical investigations of a method of correcting acquired epiphyseal growth deformities, either in length or angularly. The method by which correction was attempted was epiphyseal traction. Connolly et al[20] conducted their initial animal study, which involved 34 immature dogs from 12 to 16 weeks of age, to determine whether deformity correction achieved initially by epiphyseal traction would have long-lasting effects (ie, until the animals reached skeletal maturity) or would be lost by premature closing of the physis. The initial effect of the limb lengthening on the dogs was a pull-out fracture produced at the junction between the physis and the primary spongiosa of the metaphysis. This separation was consistent in that it began at the posterior part of the femur and progressed anteriorly. The medial and lateral periosteal fibers stretched, but did not rupture, and returned to normal length as the defect healed. This area subsequently filled in with calluslike tissue and later with bony trabeculae.[20] This study[20] yielded an average of 66% deformity correction across all experimental groups. In 3 of the original 34 cases, the lengthened epiphyseal plate closed prematurely, resulting in a loss of previously gained length. The reasons for this closure were inconclusive; however, the authors hypothesized that compression of the physis or excessively long periods of external fixation may have contributed to the closure. The methods for limb lengthening and angular deformity correction in the canine model were later applied clinically on humans by the same authors.[20] The first case was that of an 8-year-old boy with a growth deformity of 7 cm in the distal femoral epiphysis secondary to enchondroma. His results were unsatisfactory because the external fixation device was removed prematurely and the lengthened area shortened approximately 2.5 cm before healing completely. The second patient was an 11-year-old girl with multiple enchondromatosis and a progressively increasing leg-length discrepancy. This trial was also unsuccessful because the external fixation device was removed prematurely secondary to patient discomfort and pin-tract drainage. At growth plate closure 2 years later, the leg-length discrepancy remained at 5 cm as compared with the initial 7 cm.[20] Although both clinical trials were unsuccessful, the authors[20] felt that the method merits further consideration and application, as the technique allows limb lengthening and angular deformity correction without the need for internal fixation or bone grafting. The authors also concluded that this method is likely to be followed by premature closure of the physis and that this consideration should be kept in mind when treating younger patients.

Implications for the Future

The results of previous limb-lengthening procedures were discouraging because of the unpredictability of regenerated bone formation and mechanical difficulties with the fixators.[15] Technical improvements in the external fixation method and a better understanding of the biological aspects of bone and soft tissue elongation have led to overall improved results with the Ilizarov limb-lengthening procedure. Physical theraphy management of a patient with an Ilizarov external fixator, however, may vary among different institutions, and there is no definitive research on the efficacy of physical therapy management with these patients. Continued efforts need to be made for more standardized physical therapy management in order to maximize the benefits of surgery and to ensure improved functional outcomes.

(*)The Hygenic Corp, 1245 Home Ave, Akron, OH 44310. ([dagger])The Purdue Frederick Co, 100 Connecticut Ave, Norwalk, CT 06856.

PHOTO : Figure 1. Ilizarov apparatus hardware: Wires of half pins insert into bone and are then attached to threaded rods (A); modular design allows for customized assemblage into an almost infinite variety of frame configurations (B).

PHOTO : Figure 2. Rods have 1-mm pitched threads, such that one full turn of the nut distracts or moves the rings closer by 1 mm. Patients perform limb lengthening by advancing the nut one-quarter turn four times daily. Alternatively, graduated telescopic rods with calibrated "clicker" can be used to simplify the process.

PHOTO : Figure 3. Radiographs showing limb lengthening via Ilizarov method in a 12-year-old child with right hypoplasia of the femur: initial corticotomy (A), distraction phase into longitudinally oriented trabeculae filling the interzone (B-D), and maturation during the consolidation phase (E-F). Total lengthening was 8.5 cm.

PHOTO : Figure 4. Child, aged 10 years 6 months, with paralytic shortening of left leg (predicted limb-length discrepancy = 7.5 cm) attributable to poliomyelitis (A). Correction by simultaneous lengthening of tibia and femur, with equalization of limb lengths (B, C).

PHOTO : Figure 5. Sixteen-year-old patient with Ollier's disease, predicted limb-length inequality of 11 cm, and associated multiple-level angular deformities in tibia (A, B). Anterior-posterior radiograph of tibia showing valgus angulation proximally of 30 degrees (C). Lateral radiograph showing distal procurvatum deformity of 30 degrees (D). Postoperative use of Ilizarov frame with hinges to allow gradual correction of both angular deformities, simultaneously (E,F). Note angulation of rings relative to each other, but perpendicular to the long axis of the bone in the plane of the deformity. Anterior-posterior proximal tibia (G). Lateral distal tibia (H). On completion of the angular corrections, rings are parallel to each other (I, J). Hinges have been replaced by threaded rods, and limb lengthening is being performed through the proximal corticotomy (K, L).

References

[1]Aronson J, Harp J. Factors influencing the choice of external fixation for distraction osteogenesis. In: External Fixation: Instructional Course Lectures. Park Ridge, Ill: American Academy of Orthopaedic Surgeons; 1990;39:175-183. [2]Ilizarov GA, Frankel V. The Ilizarov external fixator: a physiologic method of orthopaedic reconstruction and skeletal correction. Orthopaedic Review. 1988;17:1142-1154. [3]Codvilla A. On the means of lengthening in the lower limbs, the muscles, and the tissues which are shortened through deformity. American Journal of Orthopaedic Surgery. 1905;2:353-369. [4]Browner B, Treharne R. A historical review of the Ilizarov technique. Presented at the Richards Medical Company Convention on Treatment of Pseudarthrosis, Malunions, and Bone Defects; November 15-17, 1989; Houston, Tex. [5]Schwartsman V, McMurray MR, Martin SN. The Ilizarov method: the basics. Contemporary Orthopaedics. 1989;6:628-638. [6]Ilizarov GA. The principles of the Ilizarov method. Bull Hosp Jt Dis Orthop Inst. 1988;48:1-11. [7]Tachdjian M. Pediatric Orthopaedics. Philadelphia, Pa; WB Saunders Co; 1990;4:2850. [8]Moseley CF. Leg length discrepancy. In: Morrissy RT, ed. Pediatric Orthopaedics. 3rd ed. Philadelphia, Pa: JB Lippincott Co; 1990;767. [9]Mosca V, Moseley CF. Complications of Wagner leg lengthening and their avoidance. Orthopaedic Transactions. 1986;10:462-473. [10]Paley D. Problems, obstacles, and complications of limb lengthening by the Ilizarov technique. Clin Orthop. 1990;250:81-104. [11]Newschwander G, Dunst R. Limb lengthening with the Ilizarov external fixator. Orthopaedic Nursing. 1989;8:15-21. [12]Paley D. Current techniques of limb lengthening. J Pediatr Orthop. 1988;8:73-92. [13]DeBastiani G, Aldegheri R, Brivio L, Trivella G. Chondrodiastasis: controlled symmetrical distraction of the epiphyseal plate. J Bone Joint Surg [Br]. 1968;4:550-556. [14]Wagner H. Operative lengthening of the femur. Clin Orthop. 1978;136:125-142. [15]DalMonte A, Donzelli O. Comparison of different methods of limb lengthening. J Pediatr Orthop. 1988;8:62-64. [16]Aronson J, Boyd C, Harrison B, et al. Mechanical induction of osteogenesis: the importance of pin rigidity. J Pediatr Orthop. 1988;8:396-401. [17]Catagni M, Cattaneo R, Tentori L, Villa A. Limb lengthening in achondroplasia by Ilizarov's method. Int Orthop. 1988;12:113-179. [18]Newington Children's Hospital Protocol for Ilizarov Procedures. Newington, Conn: Newington Children's Hospital; 1990:1-5. [19]Tajana GF, Morandi M, Zembo M. The structure and development of osteogenic repair tissue according to Ilizarov technique in man. Orthopedics. 1989;12:515-523. [20]Connolly J, Huurman W, Lipiello L, Pankaj R. Epiphyseal traction to correct acquired growth deformities. Clin Orthop. 1986;202:258-268.

S Simard, BS, PT, was Staff Physical Therapist, Newington Children's Hospital, 181 E Cedar St, Newlington, CT 06111, when this article was written. She is currently Staff Physical Therapist and Clinical Coordinator, Greater Hartford Physical Therapy, 85 Gillett St, Hartford, CT 06105 (USA). She is also a student in the Orthopaedic Physical Therapy Master's Degree Program at Quinnipiac College, Hamden, CT. Address all correspondce to Ms Simard. M Marchant, MAPT, PT, was staff Physical Therapist, Newington Children's Hospital, when this article was written. She is currently pursuing her doctoral degree in community health at the University of Connecticut, Storrs, CT. G Mencio, MD, was Assistant Professor of Orthopaedic Surgery, University of Connecticut, Storrs, CT 06268, and Director, Limb Lengthening/Reconstructive, Newington Children's Hospital, when this article was written. He is currently Assistant Professor of Orthopaedics and Rehabilitation, Department of Orthopaedics (ND-4207), Vanderbilt University Medical Center, Medical Center North, Nashville, TN 37232.