SURGICAL CORRECTION OF SPINAL DEFORMITY WITH THE USE OF TRANSPEDICULAR SCREW SPINAL SYSTEMS IN CHILDREN WITH IDIOPATHIC THORACIC SCOLIOSIS

Aim. To compare the results of surgical correction of spinal deformity in children with idiopathic thoracic scoliosis with the use of transpedicular screw spinal systems with diff erent pedicle screw placement. Material and methods. Th irty-one patients (14–17 years) with spinal curvature with a Cobb angle from 40° to 79° were operated on. Surgical correction of the deformity was performed using two methods, depending on the possible placement of a pedicle screw. Th e fi rst group included 16 patients for whom the transpedicular support elements were placed on both sides, throughout the completely deformed spine. Th e second group included 15 patients for whom the pedicle screws were not placed for two or more vertebrae on the concave side of the curve, at the top of the main curve. Results. Th e mean percent correction of the spinal deformity for the fi rst and second groups was 92.5% and 82.6%, respectively. Th e mean percentage of derotation of the apical vertebra for the fi rst and second groups was 73.9% and 23%, respectively. Conclusion. Th e use of data based on the anatomical and anthropometric features of the vertebral body with scoliosis facilitates selection of the best option for correction of thoracic curve in children with idiopathic scoliosis using pedicle multi-support metal construction. Th e use of the spinal pedicle system for correction of spinal deformity in children with idiopathic scoliosis enabled a uniform load distribution along the support elements of the metal construction and maintained the correction in the late postoperative follow-up period.


Introduction
Idiopathic scoliosis refers to a three-axis deformity of the spine.Surgery is considered to be the most effective treatment for severe and rigid forms of idiopathic scoliosis in children.Surgical intervention aims to correct and stabilize existing spine curvature using modern systems.In recent years, surgical hardware has evolved rapidly.Studies conducted by domestic and foreign experts have demonstrated the superiority of transpedicular screw spinal systems over hook and hybrid hardware.The advantage of systems with transpedicular supporting structures is a corrective eff ect on all three columns of the spine, restoration of physiological spine profi les, and the achievement of true derotation of vertebral bodies at the apex of the scoliotic curve [1][2][3][4].In addition to the restoration of nearly physiological frontal and sagittal spine profi les, systems are able to maintain the achieved correction over long-term follow-up periods aft er the intervention [5,6].Comparative studies on surgical treatment in patients with idiopathic scoliosis of the thoracic spine have evaluated various spinal systems, including the hook and hybrid [7] and hybrid and transpedicular systems [8].These findings demonstrate the advantages of one hardware type over others.However, only a few studies have evaluated different surgical interventions for spinal deformity in idiopathic scoliosis using spinal systems with transpedicular supporting structures [9].Notably, no studies on spinal deformity treatment in children with idiopathic scoliosis comparing transpedicular spinal systems with other surgical technologies have been reported to date.

Aim of the study
Th is study aims at a comparative analysis of the results of surgical correction of spinal deformities  Pediatric Traumatology, Orthopaedics and Reconstructive Surgery.Volume 4. Issue 2. 2016 in children with idiopathic thoracic scoliosis.Outcomes following the use of transpedicular screw spinal systems with diff erent pedicle screw placement on both sides of all vertebrae within the curvature (group 1) were compared with those of patients who received less than two pedicle screws on the concave side of the curvature due to a small (less than 4 mm) curve base (group 2).

Materials and methods
We performed comparative analysis of the outcomes of surgical treatment in 31 patients (2 boys, 29 girls) between the ages of 14 to 17 years with idiopathic thoracic scoliosis (type I by Lenke) of III-IV degree (according to V.D. Chaklin).In all adolescents, thoracic scoliotic curves were in clockwise orientation.Th e magnitude of the main thoracic scoliotic curve ranged from 40° to 79° by Cobb.All patients voluntarily provided consent to participate in the study and undergo the surgical intervention.
All patients underwent preoperative examination according to standard procedures.Standing twodimensional plain spinal radiography (frontal and lateral) and functional spondylography with right and left fl exion were performed to assess the mobility of the thoracic spine.With the aim of eliminating intracanal pathology and assessing the spinal cord, magnetic resonance imaging of the spine was performed.Computer tomography (CT) was performed to evaluate the anatomical features of deformed vertebra.CT data were transferred to a navigation system equipped with soft ware SpineMap 3D.Th ree-dimensional CT reconstructions of the external transverse and longitudinal size of the curve base for all vertebra involved in the scoliotic curve were created using SpineMap 3D soft ware.Th e feasibility of transpedicular screw installation in the body of each vertebra within the primary soliotic curve was determined according to anatomic and anthropometric data.Th e criterion for the feasibility of correct installation of the screw was an external transverse and longitudinal diameter of the curve root of no more than 4 mm.When the transverse size of the curve base was less than 4 mm, screw installation was not performed.Measurement of the apical vertebra rotation was performed according to the method of S. Aaro, G. Ohlen [10] before and aft er surgery using CT imaging.
Th e mobility of the primary scoliotic curve, the percentage of curvature correction, and derotation of apical vertebra obtained during surgery were determined on the basis of radiological studies.
Th e mobility of the deformity was calculated using the following formula:

Rotation before surgery
The first surgical treatment option was performed in patients of group 1 (16 patients) by approaching the posterior bone structures of the vertebral bodies over the scoliotic curve.Two transpedicular support elements were installed at all vertebrae within the scoliotic curve with the use of soft ware navigation and under halo-tibial traction.Nail bends followed the physiological sagittal profi le of the spine and were placed on the concave side of the deformity into hardware support elements.To perform a true derotation maneuver, the VCM system was installed according to the placement of pedicle screws on the convex and concave sides of the deformity apex (support length included 3-4 vertebra).Nail rotation by 90° was performed at the same time as the true derotation maneuver of the thoracic spine in the opposite direction using the Vertebral Сolumn Manipulation (VCM) system.Segmental correction was performed according to deformity of the concave side of the curvature.Nails were then installed following physiological spinal curves in the support elements on the opposite side to perform segmental compression.Surgery was competed with hardware stabilization in combination with dorsal spinal fusion along the implant (Fig. 1 a, b, c, and d).
A total of 15 patients (group 2) underwent the second surgical treatment option.In this group of patients, it was not possible to install two or  Pediatric Traumatology, Orthopaedics and Reconstructive Surgery.Volume 4. Issue 2. 2016 more pedicle screws on the concave side of the curvature due to small anatomical dimensions of the vertebral arch base (outer diameter less than 3.5 mm).Th e ideal approach for correction of the curvature in this group of patients diff ered from the above-described option of nail installation along the sides of the main curve and maneuvers to correct the spinal deformity.In this group, halotibial traction was performed aft er installation of the transpedicular support elements.Th e fi rst nail following the physiological curve was sequentially fi xed into the support elements on the convex side of the deformity.Kyphotic and scoliotic deformities were corrected by direct pressure to the top of the main curve, with a translational maneuver and segmental compression.A second nail was then installed, following the physiological curve, into the support elements of the hardware on the opposite side, with final correction performed according to segmental deformities.Surgery was completed with posterior spinal fusion (Fig. 2 a,  b, c, and d).
Postoperative treatment included breathing exercises, massage of the upper and lower extremities, and therapeutic rehabilitation exercises.Patients were allowed to stand on postoperative day 3 or 4 and were discharged for outpatient treatment on postoperative days 12-14.All children were examined preoperatively, directly after surger y, 6 and 12 months postoperatively, and then once a year thereafter.The late follow-up period was from 1 to 3 years postoperatively.

Results
Postoperatively, patients in group 1 with idiopathic thoracic scoliosis had deformities of 40° to 79° (mean deformity magnitude, 56.8°).The angle of scoliotic deformity with flexion ranged from 17° to 61° (mean angle, 35.3°), with a mobility of 37.8%.Th e magnitude of kyphosis in the thoracic spine ranged from 4° to 42° (mean angle of kyphosis was 20.6°) and of lumbar lordosis ranged from 17° to 50° (mean angle of lordosis was 31.2°).Th e angle of apical vertebra rotation was 10.4° to 31.4° (mean angle of rotation was 19.2°).Postoperatively, all patients had improved or fully restored frontal and sagittal trunk balance according to clinical examination (Table 1).
After surgery, the residual deformity of the scoliotic curve varied from 0° to 13° (mean magnitude of residual deformity was 4°), with a mean percentage of correction of 92.5%.The magnitudes of kyphosis and lordosis ranged from 10° to 40° (mean angle of kyphosis was 21.5°) and 17° to 40° (mean angle of lordosis was 25°), respectively.Th e residual angle of apical vertebra rotation ranged from 4° to 10° (mean residual angle of rotation was 5°).Th e mean percentage of apical vertebra derotation was 73.9%.Th e length of fi xation varied from 10 to 12 vertebrae, with a mean number of 11 (the level of fi xation varied from Th 4 to L3).Th e number of transpedicular support elements per patient varied from 20 to 24, with a mean number of 22 screws.Aft er 12 months, the mean magnitude of scoliotic curve was 4°, the mean kyphotic angle was 21.1°±6.7°,and the mean angle of lordosis was 25.7° ± 6.6°, indicating no loss of correction.Aft er 3 years of follow-up, the mean angle of scoliosis was 7°, the mean angle of kyphosis was 21.4° ± 6.5°, and the mean angle of lordosis was 26.9° ± 7.0°, indicating that the loss of correction was within the range of measurement error.In group 2, the degree of deformity prior to surgery ranged from 51° to 78° (mean deformity magnitude was 62.4°).Th e mean angle of scoliotic deformity with flexion ranged from 30° to 58° (mean deformity magnitude was 40.3°), with a mean mobility of 35.4%.The magnitudes of kyphosis in the thoracic spine and lumbar lordosis ranged from 7° to 40° (mean angle of kyphosis was 17.4°) and 20° to 50° (mean angle of lordosis was 28.5°), respectively.Th e angle of apical vertebra rotation ranged from 18.1° to 31° (mean angle of rotation was 22.1°).Postoperatively, all patients had improved or fully restored frontal and sagittal trunk balance according to clinical examination (Table 2).Aft er surgical treatment, the residual deformity of the scoliotic curve ranged from 6° to 19° (mean value of residual deformity was 10°), with a mean percentage of correction of 82.6%.Th e magnitudes of kyphosis and lordosis ranged from 10° to 33° (mean angle of kyphosis was 23°) and 21° to 37° (mean angle of lordosis was 27°), respectively.Th e residual angle of apical vertebra rotation was between 14° and 24° (mean residual angle of rotation was 17°).Th e mean percentage of apical vertebra derotation was 23%.Th e length of fi xation varied from 10 to 12 vertebrae, with a mean of 11 vertebrae (level of fixation varied from Th4 to L3).The number of transpedicular support elements per patient ranged from 15 to 22, with a mean number of 18 screws.Aft er 12 months, the mean angle of scoliosis was 11.5°, the mean kyphotic angle was 23.0° ± 7.0°, and the mean lordosis angle was 27.3° ± 5.4°, indicating no loss of correction.Aft er 3 years of follow-up, the mean angle of scoliosis was 13.0°, the mean angle of kyphosis was 21.9° ± 6.6°, and the mean angle of lordosis was 27.7° ± 5.6°, indicating that the loss of correction was within the range of measurement error.Comparative analysis of surgical treatment effi cacy (Table 3).
Preoperatively, no significant differences in scoliotic curve magnitude were observed between groups.Postoperatively, the residual scoliotic curve in group 1 was significantly smaller than that in group 2 (P < 0.001).Preoperatively, no signifi cant diff erences in the magnitude of apical vertebra rotation were observed between groups.Postoperatively, the residual apical vertebra rotation in group 1 was signifi cantly smaller than that in group 2 (P < 0.0001).
None of the children in either group had any neurological complications, hardware instability, or loss of correction during the late follow-up period.

Discussion
Age, gender, and preoperatively angle of scoliosis and mobility were comparable between groups preoperatively (Tables 1 and 2).Apical vertebra rotation, kyphosis, and lordosis were also comparable preoperatively.Improvement or restoration of all measured parameters to physiological norms was observed according to postoperative clinical and radiological examinations in both groups of patients.Th e magnitude of spinal scoliotic deformity correction in group 1 (92.5%) was signifi cantly greater than that in group 2 (82.6%) likely due to the use of two support elements in each segment of the scoliotic curve.At the same time, the magnitude of apical vertebra derotation in group 1 (73.9%) was signifi cantly greater than that in group 2 (23%).Th is result was attributed to the use of the VCM system to achieve true derotation of the vertebral bodies around the apex of the main curve in group 1. Th e magnitude of kyphosis and lordosis correction in both groups of patients was similar, with improvement or restoration to physiological norms observed according to clinical and radiological examination.Th us, the magnitude of spinal sagittal profi le correction in children with idiopathic thoracic scoliosis did not depend on the surgical treatment performed or the sequence of manipulations used during surgery.

Conclusion
The use of anatomical and anthropometric analyses of vertebral bodies facilitates the selection of the best surgical option for correction of thoracic curvature using pedicle multisupport hardware in children with idiopathic scoliosis.Th is study demonstrates that the installation of transpedicular support elements throughout the deformed spine from two sides provides better three-dimensional correction of spinal deformity, particularly regarding derotation of the vertebral bodies at the apex of the scoliotic curve.In cases where it is not possible to install two or more screws, the effi cacy of surgery is slightly lower, but long-term outcomes are maintained.Th ese data indicate that the use of this method is also justifi ed.Th e use of the spinal pedicle system for correction of spinal deformity in children with idiopathic scoliosis enables a uniform load distribution along the support elements of the metal construction, with the correction maintained throughout the late postoperative follow-up period.

Funding information and conflicts of interest
of scoliotic deformity correction was calculated using the following formula: C = Standing scoliosis before surgery -Standing scoliosis aft er surgery × 100 %.Standing scoliosis before surgery Th e percentage of apical vertebra derotation was determined according to the following formula: DR = Rotation before surgery --Rotation aft er surgery × 100 %.

Figure 1 .Figure 2 .
Figure 1.Spinal radiographs of patient T (16 years old).Idiopathic right thoracic scoliosis.A, Preoperatively, the angle of scoliotic deformity was 58° according to Cobb, the angle of kyphosis was 10°, and the angle of lordosis was 17°.В, Postoperatively, the angle of scoliosis was 0°, the angle of kyphosis was 22°, and the angle of lordosis was 30°

Table 1
The results of surgical deformity correction in group 1 of patients with idiopathic thoracic scoliosis in the early postoperative period

Table 2
Surgical deformity correction in group 2 of patients with idiopathic thoracic scoliosis

Table 3
The results of surgical deformity correction in patients with idiopathic thoracic scoliosis in the immediate and late postoperative periods  Pediatric Traumatology, Orthopaedics and Reconstructive Surgery.Volume 4. Issue 2. 2016