Orthopedics

Pediatric Limb Deformity Correction

Ilizarov developed the important concepts of stable external fixation combined with minimal soft tissue disruption to obtain reliable healing of deformity corrections. Although good results have been achieved using the Ilizarov method, its largest criticisms are related to the steep learning curve of use and difficulty correcting multiaxial deformity with the frame.⁷ The TSF’s hexapod design and computer-aided strut adjustments make it easier to correct multiaxial deformity. Therefore, an increasing interest has been seen in using the TSF in pediatric limb deformity corrections. To date, the use of the TSF has been described in the literature for many usual and unusual conditions (Table 2).^4,5,7–24 New applications of the TSF continue to be developed as experience with the device expands.

Table 2: Indications for the Spatial Frame

Blondel et al⁸ conducted a prospective study of 36 patients with a mean age of 11.1 years (range, 3 to 18 years) who required isolated limb lengthening of >4 cm, axial deformity correction, or both. Sixty-seven deformities were corrected with the TSF, including deformities of the femur, tibia, forearm, and ankle. Eighty-three percent of patients had no residual deformity at initial follow-up, and 91% of the patients eventually achieved correction objectives. The authors concluded that the TSF performed equally as well as the Ilizarov in limb lengthening while providing better rotational, translational, and residual deformity correction. The authors noted less pain in this study group by following the need for long-term analgesics and length of hospital stay. They postulated that this decrease in pain compared with other fixators may be due to the design of the construct evenly distributing stress among 6 struts instead of among 3 of 4 vertical stems, as in Ilizarov fixation.⁸

A study by Marangoz et al⁹ retrospectively reviewed 22 femurs in 20 patients (age range, 5.9 to 24.6 years) treated with a TSF for femoral deformity correction from multiple etiologies with a mean follow-up of 15.7 months (range, 4.5 to 35 months). Mean time in the frame was 6.2 months (range, 2.6 to 19 months). Mean limb lengthening was 4.9 cm at an average rate of 2.2 months/cm in 8 femurs. All but 1 patient was corrected to within 3° of normal with regard to femoral deformity. Valgus was corrected an average of 12.9°, varus was corrected 10.4°, and procurvatum was reduced an average of 23°.

Naqui et al⁷ reviewed their experiences with congenital and acquired deformity correction of 53 patients (mean age, 10.7 years) with 60 frames on 55 limbs. Their frame constructs included single and stacked TSF frames and combination TSF–Ilizarov foot frames. Mean follow-up was 22 months (range, 12 to 59 months). Seventeen limbs underwent residual correction for leg-length discrepancy >15 mm or angulation >5° using the same frame construct. Ultimately, 40 limbs had no final deformity, 12 limbs had residual deformity accepted by the patient and surgeon (leg-length discrepancy <15 mm or angulation <5°), and 3 limbs and 3 patients needed further treatment. Of the 3 patients who needed further treatment, 1 had deformity recurrence of fibular hemimelia, 1 had aborted treatment of pseudarthrosis of the tibia before regenerate formed, and 1 developed deformity due to a pseuduoaneurysm at the regenerate site of a tibial pseudoarthrosis thought to have occurred from pin site insertion near the long saphenous vein.⁷

A smaller study reported 5 patients with a mean age of 11 years (range, 6 to 16 years) treated for congenital and acquired deformities of the lower extremity (4 femurs and 1 tibia) with the TSF.⁴ All patients in this series had undergone prior operations or lengthening on the affected extremity. The authors achieved mean lengthening of 5.9 cm (range, 1.7 to 7.2 cm), mean sagittal angulation correction of 10.6º (range, 0° to 19°), and mean lateral translation of 12.6 mm (range, 0 to 33 mm).⁴

Eidelman et al⁵ reviewed their experience with the TSF in treating a variety of pediatric conditions. The series consisted of 44 frames on 31 patients with a mean age of 12.2 years (range, 3.5 to 17 years) at the time of surgery. Their experience with angular deformity and shortening revealed a mean lengthening of 40 mm (range, 25 to 80 mm) with a mean external fixation time of 14.1 weeks (range, 9 to 24 weeks). They also reported 9 patients with angular deformity correction in which all but 1 had full restoration of normal mechanical axes.⁵

A more recent study by Iobst²⁴ directly compared limb lengthening with the TSF and hexapodal struts to limb lengthening with the TSF equipped with Ilizarov-type uniplanar struts in pediatric patients. Patients treated with the traditional TSF frame gained a mean length of 4.13 cm with a lengthening index (number of months the fixator is on the patient divided by number of centimeters gained) of 1.79 months/cm. Patients treated with TSFs with Ilizarov struts gained a mean length of 4.21 cm, with a lengthening index of 1.33 months/cm. The lengthening index for the TSF in this study is comparable with that of other studies.^9,10 The author postulated that this increase in lengthening time is caused by the more complex, gradual correction in multiple planes in the TSF compared with the axial-only correction of the Ilizarov-type struts.²⁵ For purely axial lengthening, the Ilizarov construct may have a shorter time to lengthening. However, most deformities involve >1 plane, and the ease of use and ability to correct multiple axes at once with the TSF may decrease overall length of time in the fixator.

Blount’s Disease

Blount’s disease is a condition of unknown etiology that causes multiplanar deformity of the tibia, including proximal tibia vara, proximal tibia procurvatum, and internal tibial torsion.¹¹ Given the multiplanar deformity and limb-length inequality created by the disorder, the TSF is potentially an ideal treatment method for Blount’s disease. A representative case is shown in Figure 2. Fibular osteotomy may be performed concurrently with the proximal tibia osteotomy to aid with correction, but a recent study has shown that fibular osteotomy may not be necessary.¹¹

Figure 2: Full length anteroposterior radiograph showing left sided Blount’s changes to the proximal tibia (A). Anteroposterior radiograph showing correction of proximal tibia deformity after removal of spatial frame (B). Lateral radiograph of tibia showing correction of proximal tibial deformity (C). Clinical photograph of patient with correction of malalignment after spatial frame removal (D).

Feldman et al¹² reported their experience treating patients with Blount’s diesease using the TSF. Nineteen patients (22 tibias) with a mean age of 9.9 years (range, 3 to 16 years) and Langenskiold stages II–V were treated gradually with a TSF for a mean of 14.6 weeks (range, 9 to 24 weeks). Twenty-one tibias were corrected to within 3° of normal in both the sagittal and coronal planes. Internal tibial torsion decreased from a mean of 17.5° (range, 10° to 30°) to a mean of 0°, mechanical axis deviation decreased from a mean of 53.9 mm (range, 31 to 120 mm) to a mean of 1.4 mm (range, 0 to 4 mm), and mean varus decreased from a mean of 16.5° (range, 8° to 50°) to a mean of 0° (range, −2° to 2°). They attribute their excellent results to the gradual correction affording the ability to make subtle changes effortlessly using residual correction without returning to the operating room.¹²

Bar-on et al¹³ reported 4 patients with a mean age of 8.1 years (range, 6.9 to 9.1 years) who were treated for severe, early-onset Blount’s disease (Langenskiold stages V and VI), with elevation of the medial tibial plateau, lateral hemiepiphysiodesis, and proximal tibial metaphyseal osteotomy and gradual correction with a TSF. Mechanical axis was corrected to 0° in 3 patients and 6° in the other patient. Tibial torsion was corrected to 0° in 3 patients and 15° of external rotation the other patient. Lastly, preplanned overlengthening of 1 to 4 cm was achieved in all patients. Two patients had a recurrence of 7° of varus that stabilized after 1 year. The authors attributed the recurrence to either an incomplete lateral epiphysiodesis or to mild distal femoral varus.¹³ Eidelman et al’s⁵ experience treating 4 patients with adolescent Blount’s disease (mean age at surgery, 14.5 years) with the TSF was also positive. They achieved restoration of the mechanical axis to within normal parameters in all 4 patients.

The question as to whether acute or gradual correction in Blount’s disease is more effective was investigated using the TSF. Feldman et al²⁵ evaluated acute vs gradual correction in 32 patients and found statistically greater angular and translational correction with the gradual correction group using medial proximal tibial angle, posterior proximal tibial angle, and mechanical axis deviation as correction criterion. Both groups underwent the same surgical planning and osteotomy procedure, except the acute group had an external fixator placed after acute correction was obtained, and the gradual group had a TSF placed with correction obtained over a mean of 14.3 weeks (range, 9 to 24 weeks).¹⁴

Foot and Ankle

The TSF can be used to treat complex foot and ankle deformities in children and adolescents. Foot and ankle treatments for idiopathic clubfoot, teratalogic clubfoot, metatarsal lengthening, tibial lengthening, arthrogryposis, rigid equinovarus secondary to spina bifida, hindfoot deformity, and ankle deformity have been reported.^2,14 Eidelman and Katzman¹⁴ reported 13 patients (14 frames) with a mean age of 8 years (range, 3.5 to 14 years) at the time of surgery who had complex foot deformities that were treated with the TSF. Eleven of the patients had correction of their deformities, but almost all had some type of complication. The most common complication encountered was metatarsophalangeal joint dislocation, prompting the authors to routinely pin all toes with Kirschner wires and attach them to the frame during treatment. Another case series by Eidelman and Katzman¹⁵ reported their experience in treating rigid clubfoot and congenital vertical talus with the TSF in 7 patients (age range, 4 to 16 years) with arthrogryposis. They used the frame with osteotomies or for soft tissue distraction, and the most common complication was pin-site infection, occurring in >50% of the patients.

A more recent article by Hassan and Letts¹⁶ reviewed their experience with congenital foot deformity correction with the TSF in patients aged between 6 and 14 years. Most patients had untreated congenital talipes equinovarus treated with soft tissue releases and midfoot osteotomies prior to frame application. All patients in the study achieved plantigrade placement of their feet. Superficial pin-tract infection was the most common problem encountered. The authors support this method of treatment for rigid congenital foot deformities because it allows gradual correction to protect soft tissue and structures at risk, it allows full weight bearing in the frame to desensitize the feet to the new anatomic position, and it allows for unrestricted examination of the circulation and neurological function of the foot during treatment.¹⁶

Acute Trauma

Given the appropriate indications and applications, the TSF is an excellent treatment option for acute and delayed pediatric trauma. Several articles in the literature demonstrate successful management of pediatric trauma with the TSF. Al-Sayyad¹⁷ used the TSF to treat 10 high-energy, unstable tibial fractures in 9 patients (mean age, 12 years 3 months), and retrospectively reviewed the outcomes (mean follow-up, 3.1 years). The TSF was constructed, intraoperative radiographs were taken, and the Total Residual program was immediately used to determine strut length for anatomic reduction. These values were dialed into the struts, and the patient was awakened from anesthesia. The fractures healed over a mean of 18 weeks (range, 12 to 29 weeks), and the patients remained in the frame for a mean of 19 weeks (range, 12 to 33 weeks). All fractures united without loss of reduction, remanipulation, or malunion, and all patients were doing well and involved in sports at last follow-up. No patient sustained a refracture.¹⁷

Blondel et al¹⁸ treated 11 patients (mean age, 12 years) with tibial fractures with the TSF. Three had loss of reduction in a cast, 3 had open fractures, 4 had associated fractures and closed head injury, and 1 had compartment syndrome. The frame was applied using traction as the only reduction maneuver, and radiographs were taken later on postoperative day 1 to determine a turning schedule. Radiographically, 9 patients achieved reduction without residual deformation, 1 had a flexion deformity of 8°, and 1 had overgrowth of 7 mm. The authors placed 5 patients in Sarmiento braces after frame removal to limit the risk of refracture, but they did not define their criteria as to which patients would receive the brace.¹⁸

Eidelman and Katzman¹⁹ reported their experiences in treating 13 patients (mean age, 11.1 years) with 13 complex tibial fractures, 9 open fractures, and 4 closed fractures. In this series, all patients were treated with another fixation method (monolateral external fixator, cast, or Ilizarov frame) prior to the TSF. Mean time to TSF application was 31.8 days (range, 3 to 165 days). Acute correction was not performed in any case, but the turning schedule began on postoperative day 1. Twelve patients healed in normal anatomical alignment and 1 developed proximal tibial valgus 1 year after frame removal that was treated with medial hemiepiphysiodesis. The authors stressed gradual correction (1 mm/day) to prevent neurovascular compromise, unnecessary pain, and soft tissue injury in patients who present when fracture reduction is delayed.¹⁹

Posttraumatic Correction

Figure 3 demonstrates how the TSF can be used to correct posttraumatic deformities. In this case, the patient suffered a physeal fracture of his proximal tibia when he was 13 years old. He developed a complex deformity consisting of shortening, external rotation, negative tibial slope, and valgus with mechanical axis deviation. All of these deformities were addressed and corrected simultaneously with a single application of the TSF.

Figure 3: Full length bilateral standing radiographs of the lower extremities showing significant proximal tibial malunion and subsequent limb malalignment (A). Anteroposterior radiograph of the knee showing significant lateral tibial plateau injury and valgus malalignment (B). Lateral radiograph of the knee showing a reverse slope of the tibial plateau after healing (C). Anteroposterior radiograph of the limb with the Spatial Frame in place, after corrective osteotomy (D). Full-length anteroposterior radiograph of the limb after healing, with correction of the coronal malalignment (E). Lateral radiograph of the tibia after osteotomy union, with correction of the malalignment and reversed tibial slope (F).

The TSF can be used for correction of posttraumatic deformities in the subacute or delayed setting. Eidelman et al²⁰ treated 18 patients (mean age, 13.1 years) with various posttraumatic deformities with a TSF. These deformities included malunions and growth arrests (primarily of the tibia), 3 distal femoral deformities, and 1 distal radial physeal-related deformity. Osteotomies were performed, and the frame was removed after a mean of 12.3 weeks (range, 8 to 24 weeks). Follow-up was a minimum of 2 years after frame removal. In all patients, the mechanical axis was restored, length equalization was achieved, all patients were pain free, and all patients had regained preoperative range of motion.

Ganger et al²¹ retrospectively reported their experience in treating 22 patients with 25 posttraumatic lower-limb deformities with the TSF. They analyzed the accuracy of correction, complication rate, clinical outcome, and duration of treatment. Although mean age at time of injury was 14.3 years (range, 2 to 46 years), mean age at time of correction was 22.7 years (range, 12 to 48 years). Mean follow-up was 21.1 months (range, 12 to 43 months). At final follow-up, all sagittal and axial deformities were corrected, and 2 cases showed a residual mechanical axis deviation. One patient sustained a refracture of the distal femur with trauma 8 months after removal of the frame. One patient sustained late bowing of the proximal tibia after non-compliance with weight bearing. The authors support the use of the TSF for correction of posttraumatic deformity because of the good radiographic results and minimal morbidity associated with the TSF.²¹

A case report by Siapkara et al²² described their experiences treating deformity due to anterior growth arrest of the proximal tibia after trauma in 3 patients. They were able to achieve correction of hyperextension and restoration of anatomical posterior proximal tibial angle (posterior tibial slope) in all 3 patients in a mean of 34.7 days (range, 32 to 37 days), with a mean total time in the frame of 18.3 weeks (range, 16 to 20 weeks).

Although the vast majority of posttraumatic corrections reported involve lower-extremity deformities, the TSF has also been applied to posttraumatic deformity of the upper extremity.^20,23 Seybold et al²³ treated 2 boys with a posttraumatic pseudo-Madelung deformity after an epiphyseal fracture of the distal radius. With the TSF, the surgeons were able to gradually achieve multiplanar correction of the distal radius, reduction of the distal radioulnar joint as confirmed by computed tomography, and restoration of pronation and supination to anatomical in a mean of 27 days (range, 23 to 31 days) of distraction and a mean time in the frame of 31 days (range, 79 to 92 days). Preoperative pronation and supination of patient 1 was 40° and 30° and of patient 2 was 30° and 20°, respectively; postoperative pronation and supination were 80° and 90° for patient 1 and 90° and 70° for patient 2, respectively.²³

Disadvantages

The TSF has several disadvantages. First is the cost of the frame itself,^5,19 Cost of the physical frame construct (rings, struts, and pins/wires) can range anywhere from $6000 to $12,000. Second, the smallest ring size is 105 mm and the largest ring size is 305 mm. In the pediatric and adolescent populations, smaller ring sizes than those available may be necessary to accommodate the smaller circumference of the extremities. A rare problem may occur in obese patients, such as those who may present with adolescent Blount’s disease, whom even the largest rings may not fit appropriately.

Another disadvantage may be the learning curve of the TSF. Although it is considered much easier to use and modify than the Ilizarov frame, some physicians still do not use the product because of its complexity. Those physicians may equate the complexity of the construct with the complexity of use. A learning curve exists not just for application of the TSF, but also for the indications of the frame and which patients and family would be able to psychologically handle the frame.

Another disadvantage of the TSF is the necessity for strict patient compliance. Although noncompliance is not exclusive to this type of treatment, patient compliance with the turning schedule is paramount to properly obtaining the appropriate correction. Gradual correction involves turning the struts at a rate of approximately 1 mm/day, either all at once or in divided turns. Patients and their families who either do not comply or are not willing to comply should not be selected as candidates for treatment with the TSF. Also, proper patient compliance with pin-site care is important to minimize and prevent infection. Noncompliance with pin-site care can result in superficial pin-site infections and, although the rates are low, this may lead to deep infection or osteomyelitis, which may have been prevented with proper care.