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Background
Distraction osteosynthesis refers to a technique in which a limb is gradually lengthened at a controlled rate across the osteotomy site. The original limb lengthening procedure was first described in the English orthopedic literature by Codvilla (1905). In the 1960s, the Wagner method (limb lengthening with cancellous bone grafting and plating of the distraction gap) was introduced into North America, and became the mainstay of limb lengthening in the United States for many years. In this technique, an open mid-diaphyseal osteotomy is carried out across the periosteum, endosteum, and cortex resulting in a 0.5 to 1 cm diastasis; followed by the placement of an external fixation system secured by screws in both the proximal and distal metaphyses. Distraction commences immediately following placement of the fixator. The distraction rate is traditionally set at 1.5 to 2 mm per day. Following attainment of the desired distraction length, iliac crest cancellous bone is grafted into the diastasis in a second operation. The affected bone is plated, and the external distractor is removed. The operated limb does not bear weight for an extended period of time to allow for incorporation of the graft. In a third operation, the plate is removed, and the subject is put on protective weight bearing (Wagner, 1978; Hood and Riseborough, 1981).
A less invasive technique for distraction osteosynthesis was developed by a Russian orthopedist Gavriil Abramovich Ilizarov in the 1950s. His work was introduced to Italy in the 1980s as a result of the former Soviet Union's policy of glasnost, and later to the United States (Frankel et al, 1988). According to Ilizarov's principle of "tension stress", bone and soft tissue will heal and regenerate in a predictable fashion under tension. The Ilizarov procedure comprises 4 phases: (i) corticotomy (a special type of percutaneous osteotomy) and placement of an external fixation system, (ii) latency period, (iii) distraction, and (iv) consolidation. This method has been employed to treat a wide variety of bone defects including limb lengthening while correcting concurrent associated angular and rotational malalignments, transporting bone segments to fill fracture gaps, and healing non-union fractures. Compared to other alternatives such as the Wagner technique, the Ilizarov method requires only one surgical procedure and appears to have fewer complications. Additionally, the Ilizarov procedure allows for simultaneous correction of multiple deformities, early movement of adjacent joints, as well as early weight bearing (Do and Sadove, 1992; Simard et al, 1992).
Cattaneo et al (1993) described the use of the Ilizarov procedure to 97 humeri on 75 patients, with 68 lengthening in 46 patients (27 males and 19 females, average age of 16.5 years) and 29 treatments for non-union in 29 patients (17 males and 12 females, average age of 46 years). For patients who underwent humeral lengthening, results were considered excellent if the projected lengthening was attained, or in the cases of length discrepancy, less than a 3-cm length discrepancy remained, or if axial alignment was acceptable (less than 10 degrees angulation), and scars were minimal. Furthermore, pre-operative function had to be maintained. Outcomes were deemed good if there was only minimal functional loss, and poor if there was a limb discrepancy of greater than 5 cm, angulation of more than 10 degrees and significant loss of function, or a permanent neurological injury. For patients who had treatments for humeral nonunion, consolidation was considered an excellent result, whereas persistence or recurrence of nonunion was considered a poor result. Duration of treatment ranged from 5 to 14 months. Forty-two (91.3 %) of the 46 patients who had undergone humeral lengthening had excellent results, 3 (6.5 %) had good results, and the remaining 1 (2.2 %) had a poor result as a consequence of reduced shoulder motion. There were no major complications associated with this procedure. For patients who underwent treatments for humeral nonunion, 25 (86.2 %) of 29 humeri healed, and 4 (13.8 %) remained ununited. Of these, there were 3 patients aged 55, 70, and 79 years, and 1 patient with irradiated bone. Results of this study indicated that the Ilizarov procedure is effective in humeral lengthening as well as in the treatment of humeral non-union.
Cierny and Zorn (1994) compared conventional methods with the Ilizarov procedure in the treatment of 44 patients with segmental tibial defects. Patients were divided into 2 groups: (i) 21 long bone defects (segmental defects averaged 6.5 cm) were reconstituted by means of transport (part of the Ilizarov procedure that entails sliding a bone fragment internally, producing distraction osteogenesis behind the defect until it is bridged) or distraction methodologies according to the Ilizarov technique, and (ii) 23 subjects (segmental defects averaged 8.5 cm) underwent conventional treatment of reconstruction using tissue transfers and transpositions, massive cancellous grafts, and combinations of internal and external fixation. Total wound consolidation and infection arrest occurred after the first treatment in 71 % of the Ilizarov wounds, and 74 % of the conventionally treated wounds. The major complication rate for the Ilizarov group was 33 %, while that for the conventionally treated group was 60 %. The overall success rate (95 %) were the same for both groups. However, the Ilizarov group averaged 9 fewer hours in the operating room, 23 fewer days in the hospital, 5 fewer months of disability times, and a saving of nearly $30,000 per application. These findings indicated that the Ilizarov procedure is faster, safer, and less expensive approach than conventional methods for the treatment of segmental tibial defects.
Fadel and Hosny (2005) noted that the Taylor Spatial Frame (TSF) uses the slow correction principles of the Ilizarov system but adds a 6-axis deformity analysis incorporated within a computer program. These researchers used the TSF in lengthening and deformity correction of the lower limbs to treat 22 cases from 1999 to 2001. There were 14 females and 8 males (average age of 16.5 years). Their target was lengthening in 8 cases, correction of deformities in 8 and both in 6. The results were excellent in 18 cases, good in 2, and fair in 2. Despite the cost, patient profile and a steep learning curve, the results were encouraging but less favorable than with the traditional Ilizarov external fixator.
Kristiansen et al (2006) noted that different methods and devices are used to perform lengthening and deformity reconstruction in the tibia. Recently, the TSF has been introduced as a computer-assisted and versatile external ring fixator. Lengthening index (LI) and complications are important result parameters, and the aim of this study was to review our first 20 tibial segments operated with the TSF and compared the results with those of using the traditional Ilizarov external fixator (IEF). These researchers lengthened 20 tibial segments in 20 patients with the TSF. The results were compared with those of 27 tibial segments from 27 patients that were lengthened with the IEF. All segments were operated on with monofocal osteotomies. In the over-lapping zone of comparable lengthening distances between 2.4 and 6.0 cm, the LI of 2.4 and 1.8 months/cm was not significantly different between the TSF and IEF groups, respectively (p = 0.17). This non-significant difference was confirmed after adjustment for age. The authors found no difference between the TSF and IEF frames regarding LI and complication rate. However, rotational, translational, and residual deformity correction is easier to perform with the TSF.
Simpson et al (2008) stated that the TSF is a fixation device used to implement the Ilizarov method of bone deformity correction to gradually distract an osteotomized bone at regular intervals, according to a prescribed schedule. These researchers modified conventional technique by: (a) pre-operatively planning a virtual three-dimensional (3D) correction; (b) basing the correction on the actual location of the frame with respect to the anatomy, immediately compensating for frame mounting errors; and (c) calculating the correction based on 3D CT data rather than measurements from radiographs. They performed a laboratory study using plastic phantoms, and a pilot clinical study involving 5 patients. In 20 tibial phantom experiments, these investigators achieved average correction errors of < 2 degrees total rotation and < 0.5 mm total lengthening. They observed clinically acceptable corrections with no complications in this pilot clinical study. The authors concluded that their method achieved high accuracy and precision in a laboratory setting, and produced acceptable outcomes in a pilot clinical study.
Naqui et al (2008) noted that correcting multi-planar lower-limb pediatric deformities requires complex and, in many cases, staged procedures. The TSF is a sophisticated external fixator system that can be used to treat simple to complex multi-planar and multi-apical skeletal deformities. These researchers described its use in 53 children during the last 7 years in a variety of pathologies and demonstrate its ease of use and versatility. A review of medical and physiotherapy records, radiographs, and CT scans of all patients treated with a TSF between June 1999 and December 2005 at the Booth Hall Children's Hospital was conducted. Data recorded were etiology of deformity, sex, age, number of previous operations, pre-operative deformity parameters, operative records and frame constructs, treatment regime, frame duration, follow-up protocol, post-treatment deformity, complications, and clinical and radiological outcome. Fifty-three patients between the ages of 12 months and 16 years (mean of 10.7 years) underwent correction programs for 55 limbs (44 tibia and 11 femurs). The etiology of deformity was congenital in 39 cases and acquired in 14. These investigators were able to achieve an acceptable correction of deformity (leg length discrepancy < 15 mm, angulation < 5 degrees) in 52 limbs. A number of complications were encountered. The authors demonstrated the TSF's ease of use for both surgeon and patient and its versatility in a variety of pathologies. The advantages of the TSF system are many. It is a simple frame construct, and application is easy. The plan and execution are structured with precise end points; it is a single-stage correction and thus avoids frame modifications. Any residual deformity can be further corrected by use of the same frame. The authors concluded that the TSF is an effective and efficient way to correct a wide variety of simple and complex often obstinate pediatric limb deformities.
Marangoz et al (2008) stated that the TSF has been used commonly in children and young adults. Its use in the tibia is more extensively studied and applied than in the femur. These researchers examined if normal alignment can be achieved with accuracy during correction of femoral deformities while avoiding major complications in children and young adults. They retrospectively reviewed the clinical and radiographic records of 20 patients (22 limbs), aged 5.9 to 24.6 years, who underwent a TSF for femoral deformity. Etiology included a number of diagnoses of the pediatric age. Minimum follow-up was 4.5 months (mean of 15.7 months; range of 4.5-to 35 months). The mean time in frame was 6.2 months (range of 2.6 to 19 months). Frontal and sagittal plane deformities were corrected to within normal values. A mean limb lengthening of 4.9 cm (range of 1.5 to 9 cm) was performed in 8 femora; 7 of which the limb length discrepancy was a secondary concern. External fixation index in the lengthening subgroup was 2.2 months/cm. The 15 complications in 13 limbs included pin tract infection, knee stiffness, delayed union, skin irritation, and posterior knee subluxation. No complications occurred in 9 limbs. Computer-assisted femoral deformity correction with 6-axis deformity analysis and the TSF is an accurate and safe technique in children and young adults.
McCarthy and colleagues (2008) examined if a monolateral fixator, which allows for correction of angular deformity and displacement in 3 planes, can correct lower extremity deformities to within normal radiographic means (anatomic lateral distal femoral angle, anatomic medial proximal tibial angle, and tibial femoral angle). These researchers retrospectively reviewed the clinical records and radiographs of 22 consecutive patients (25 limbs) who underwent deformity correction using a new multi-axial monolateral external fixator. The patients were 4 to 16 years of age. The authors had a minimum 1.2-year follow-up (mean of 2.14 years; range of 1.2 to 3.1). Those with primary femoral and tibial deformities had improvements in the mean deviation from normal of the anatomic lateral distal femoral angle, anatomic medial proximal tibial angle and tibial femoral angle. Patients with Blount's disease had improvements in the mean anatomic medial proximal tibial angle from 59.9 masculine to 87.8 masculine. Five patients had complications (2 pin site infections, 1 premature consolidation, 1 knee flexion contracture, 1 recurrence of varus). Six patients developed secondary deformities, all of which were corrected using the primary or secondary hinge. The authors concluded that this fixator can produce satisfactory results with relatively few complications.
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