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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 less than 2 degrees total rotation and less than 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 less than 15 mm, angulation less than 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.
Wukich and Kline (2008) stated that patients with diabetes mellitus (DM) have higher complication rates following both open and closed management of ankle fractures. Diabetic patients with neuropathy or vasculopathy have higher complication rates than both diabetic patients without these co-morbidities and non-diabetic patients. Unstable ankle fractures in DM patients without neuropathy or vasculopathy are best treated with open reduction and internal fixation with use of standard techniques. Patients with neuropathy or vasculopathy are at increased risk for both soft-tissue and osseous complications, including delayed union and non-union. Careful soft-tissue management as well as stable, rigid internal fixation are crucial to obtaining a good outcome. Prolonged non-weight-bearing and subsequently protected weight-bearing are recommended following both operative and non-operative management of ankle fractures in patients with DM.
DiDomenico et al (2009) noted that patients who have a diagnosis of DM, diabetic peripheral neuropathy, peripheral vascular disease and experience an unstable ankle fracture present as difficult case scenarios for treating physicians. In addition, patients who have DM, along with the presence of multiple co-morbidities, have been shown to have higher complication rates than patients who do not have DM. These researchers described a relatively safe alternative surgical percutaneous technique using external circular ring fixation in the vascularly compromised diabetic patient with an unstable ankle fracture. This novel technique decreases the risk for soft tissue complications in the high-risk diabetic patient and serves as a definitive method of fixation without the need for additional surgery. It allows the patient to have early and full weight-bearing when indicated in the post-operative period.
The Intramedullary Skeletal Kinetic Distractor (ISKD) is an internal limb lengthening device consisting of a telescoping internal limb lengthener, locking screws, and an external hand-held monitor that tracks the rotation of an internal magnet on a daily basis. Implanted after osteotomy, the ISKD lengthens gradually in response to normal movements of the limb. The device allows lengthening to take place internally, thus the risk of infection and scarring from pins moving through the soft tissues is potentially reduced.
The ISKD requires a physical leg movement to "click" the device into lengthening. In this method, there is no risk of accidentally over-stretching the bone due to the lengthener being preset to the desired fully extended length. However, there is a risk of growing the bone too quickly. Bone growth is monitored by measuring changes in the magnetic field of the embedded magnet in the system. The poles of the magnet change as the device grows. However, if the motion of the leg makes the device grow too quickly, and the magnet switches poles twice between measurements, then that growth is not recorded. This leads to overly rapid growth which can cause a number of issues such as nerve damage or causing breaks in the bone.
Potaczek and colleagues (2008) presented their findings of limb elongation method with the ISKD. Subjects consisted of 5 patients, aged 14 to 16 years, 3 boys and 2 girls, who underwent femur lengthening with the ISKD nail between 2005 and 2007. Initial shortening, surgical procedure, complications, amount of lengthening, lengthening rate, distraction index, time of treatment and mobility of adjacent joints were evaluated. Initial shortening was 4 to 11 cm. No surgical complications were observed, mean time of surgery was 145 mins, mean blood loss was 200 ml. In 3 patients difficulties with initial distraction required manipulations under general anaesthesia. Distraction was complicated in 3 cases: in 2 patients premature consolidation was noted; in 1 case the distraction rate was too high. Mean lengthening rate in the study group was 0.7 mm/day (0.6 to 0.7 mm/day). Mean distraction index was 41.7 days/cm (26.2 to 55 days/cm). Full weight bearing was allowed after mean 234 days (210 to 275 days). Transient decrease of adjacent joint mobility was observed. The authors concluded that the fully implantable, telescopic ISKD eliminated the need of external fixation and associated complications. Early results of limb lengthening with ISKD are encouraging. The authors stated that careful patient selection and pre-operative planning is required; they also noted that further studies and longer follow-up periods are also needed.
Kenawey and associates (2011a) noted that mechanically activated intramedullary lengthening nails are advantageous over external fixator. However, difficulties with the control of the distraction rate are the main drawbacks, which may in turn cause insufficient bone regenerate. These investigators reviewed the findings of of 57 lengthening procedures using ISKD nail in 53 patients (femoral = 45 and tibial = 12). Average length gain was 4.3 +/- 1.6cm. The cause of shortening was post-traumatic (n = 33), congenital (n = 20), post-tumour resection (n = 1), cosmetic femoral lengthening (n = 2) and post-correction of distal femoral varus deformity (n = 1). The desired lengthening was achieved in all patients. The mean follow-up period was 23 +/- 12 months. The healing index for patients with normal bone healing was 1.2 +/- 0.32 months/cm. Complications in femoral lengthening were superficial wound infection (n = 1), premature consolidation (n = 4) and insufficient bone regenerate (n = 11), while in the tibial lengthening, 2 developed equinus contractures, 1 had compartment syndrome following implantation of the nail and 1 insufficient bone regenerate. Furthermore, 9 runaway nails and 3 non-distracting nails were present in the femoral lengthening. One non-distracting nail responded to manipulation under anaesthesia, 1 required exchange nailing and accidental acute lengthening of 3 cm took place while manipulating the third nail. Patients with femoral lengthening and those with insufficient regenerate had significantly higher distraction rates (p = 0.006 and 0.003, respectively). Six out of the 9 runaway nails developed insufficient bone regenerate. In addition, 10.7-mm tibial ISKD nails were found to have lower rates of runaway nails compared with other used diameters. The authors emphasized the rule of distraction rates above 1.5 mm/day in the development of insufficient bone regenerate. Distraction problems with these nails are mostly due to dysfunction within the ratcheting mechanism, which may be related to the diameter of the nail. They stated that new designs for mechanically activated nails with a better control mechanism for the distraction rate are required.
Kenawey and co-workers (2011b) stated that control of distraction rate with an ISKD may be problematic and a high distraction rate may result in insufficient bone regenerate. These researchers analyzed 37 consecutive ISKD femoral lengthening procedures in 35 patients with a mean age 33 +/- 11 years and minimum follow-up of 12 months (average of 27 +/- 9 months; range of 12 to 55 months). The average length gain was 42.8 +/- 12.9 mm. A total of 8 patients had problems during distraction: 7 had "runaway nails" and 1 had a non-distracting nail. Insufficient bone regenerate developed in 8 patients. Important risk factors were a distraction rate greater than 1.5 mm/day (9.1 times higher risk), age 30 years or older, smoking, and lengthening greater than 4 cm. Less important risk factors identified were creation of the osteotomy at the site of previous trauma or surgery and acute correction of associated deformities. The authors proposed a radiological classification for failure of bone regeneration: partial regenerate failure (Type I) or complete failure resulting in a segmental defect subdivided according to a length of 3 cm or less (Type IIa) or greater than 3 cm (Type IIb). They concluded that distraction problems with the ISKD were related mostly to internal malfunction of the lengthening mechanism. A distraction rate greater than 1.5 mm/day should be avoided in femoral intramedullary lengthening. Furthermore, smoking should be a contraindication for femoral lengthening.
Schiedel et al (2011) reported the results of intramedullary leg lengthening conducted between 2002 and 2009 using the ISKD in 69 unilateral lengthening involving 58 femora and 11 tibiae. These investigators identified difficulties that occurred during the treatment and examined if they were specifically due to the implant or independent of it. Paley's classification for evaluating problems, obstacles and complications with external fixators was adopted, and implant-specific difficulties were continuously noted. There were 7 failures requiring premature removal of the device, in 4 due to nail breakage and 3 for other reasons, and 5 unsuccessful outcomes after completion of the lengthening. In all, 116 difficulties were noted in 45 patients, with only 24 having problem-free courses. In addition to the difficulties arising from the use of external fixators, there was almost the same number again of implant-specific difficulties. Nevertheless, successful femoral lengthening was achieved in 52 of the 58 patients (90 %). However, successful tibial lengthening was only achieved in 5 of 11 patients (45 %).
Mahboubian et al (2012) noted that lengthening over a nail and internal lengthening nails have been developed to minimize or eliminate patients' time wearing a frame during femur lengthening. However it is unclear whether either of these 2 approaches results in faster times to union or fewer complications over the other. These investigators examined which technique better achieved: (i) the lengthening goals, (ii) the distraction rate control, (iii) quality of the regenerate bone, (iv) fewer complications, and (v) if SF-36 scores and American Academy of Orthopaedic Surgeons-Lower Limb Module (AAOS-LLM) scores differ in each treatment modality? They retrospectively reviewed the records and radiographs of 11 patients who had 12 ISKD procedures between 2002 and 2005, and 21 patients with 22 femoral lengthening performed as lengthening over nail procedures between 2005 and 2009. Details such as leg length discrepancies, operative time, time of removal of the external fixator or ISKD, and any complications encountered were recorded; SF-36 and AAOS-LLM scores also were compiled. The minimum follow-ups for the ISKD and the lengthening over nail cohorts were 62 months (average of 76 months; range of 62 to 93 months) and 13 months (average of 27 months; range of 13 to 38 months), respectively. These researchers observed no difference in achieving the lengthening goals between the 2 procedures. Distraction was not well-controlled in the ISKD group; the distraction rates were 1.7 mm per day for the fast group (distraction rate greater than 1 mm/day) and 0.84 mm per day for the slow group (less than 1 mm/day). The lengthening over nail group had an average distraction rate of 0.88 mm per day. One of 20 of the patients who had lengthening over a nail had complications requiring additional unanticipated surgeries whereas 6 of 12 patients who had femoral lengthening in the ISKD group had such complications. The authors concluded that based on their observations, they believe the lengthening over nail technique for femoral lengthening is associated with fewer complications than the ISKD.
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