Surgical correction of spinal deformity with the use of transpedicular screw spinal systems in children with idiopathic thoracic scoliosis

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Abstract


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 different pedicle screw placement.

Material and methods.

Thirty-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. The first group included 16 patients for whom the transpedicular support elements were placed on both sides, throughout the completely deformed spine. The 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.

The mean percent correction of the spinal deformity for the first and second groups was 92.5% and 82.6%, respectively. The mean percentage of derotation of the apical vertebra for the first and second groups was 73.9% and 23%, respectively.

Conclusion.

The 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. The 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 effect on all three columns of the spine, restoration of physiological spine profiles, and the achievement of true derotation of vertebral bodies at the apex of the scoliotic curve [1-4]. In addition to the restoration of nearly physiological frontal and sagittal spine profiles, systems are able to maintain the achieved correction over long-term follow-up periods after 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

This study aims at a comparative analysis of the results of surgical correction of spinal deformities in children with idiopathic thoracic scoliosis. Outcomes following the use of transpedicular screw spinal systems with different 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. The 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 two-dimensional plain spinal radiography (frontal and lateral) and functional spondylography with right and left flexion 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 software SpineMap 3D. Three-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 software. The feasibility of transpedicular screw installation in the body of each vertebra within the primary soliotic curve was determined according to anatomic and anthropometric data. The 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 after surgery using CT imaging.

The 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.

The mobility of the deformity was calculated using the following formula:

M =

Standing scoliosis – Scoliosis with lean

× 100 %.

Standing scoliosis

  

The percentage of scoliotic deformity correction was calculated using the following formula:

C =

Standing scoliosis before surgery – Standing scoliosis after surgery

× 100 %.

Standing scoliosis before surgery

  

The percentage of apical vertebra derotation was determined according to the following formula:

DR =

Rotation before surgery – 

– Rotation after surgery

× 100 %.

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 software navigation and under halo-tibial traction. Nail bends followed the physiological sagittal profile 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 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). The ideal approach for correction of the curvature in this group of patients differed 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, halo-tibial traction was performed after installation of the transpedicular support elements. The first nail following the physiological curve was sequentially fixed 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 surgery, 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%. The 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°). The 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. The residual angle of apical vertebra rotation ranged from 4° to 10° (mean residual angle of rotation was 5°). The mean percentage of apical vertebra derotation was 73.9%. The length of fixation varied from 10 to 12 vertebrae, with a mean number of 11 (the level of fixation varied from Th4 to L3). The number of transpedicular support elements per patient varied from 20 to 24, with a mean number of 22 screws. After 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. After 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°). The 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. The 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).

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

Preoperative angle of scoliotic deformity according to Cobb, °

Preoperative angle of scoliotic deformity with felxion according to Cobb, °

Postoperative angle of scoliotic deformity according to Cobb, °

Percentage correction, %

1

40

25

0

100

2

62

42

3

95,1

3

41

20

0

100

4

44

22

3

93,1

5

63

42

9

85,7

6

60

35

10

83,3

7

58

40

0

100

8

63

43

4

93,6

9

47

17

4

91,4

10

65

46

9

86,1

11

75

61

13

82,6

12

50

29

4

92

13

56

38

8

85,7

14

53

34

2

96,2

15

54

25

3

94,4

16

79

47

10

87,3

М ± m

56.8 ± 8.7

35.3 ± 9.5

4 ± 3.5

92.5 ± 3.2

After 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%. The 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. The residual angle of apical vertebra rotation was between 14° and 24° (mean residual angle of rotation was 17°). The mean percentage of apical vertebra derotation was 23%. The length of fixation 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. After 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. After 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.

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

Preoperative angle of scoliotic deformity according to Cobb, °

Preoperative angle of scoliotic deformity with felxion according to Cobb, °

Postoperative angle of scoliotic deformity according to Cobb, °

Percentage correction, %

1

65

50

12

81,5

2

78

58

16

79,4

3

55

40

13

76,3

4

51

35

15

70,5

5

76

43

19

75

6

54

40

13

75,9

7

76

50

11

85,5

8

61

32

7

88,5

9

72

52

9

87,5

10

52

30

10

80,7

11

64

35

6

90,6

12

52

34

7

86,5

13

63

40

10

84,1

14

66

34

10

84,8

15

52

32

9

82,6

М ± m

62.4 ± 8.0

40.3 ± 8.7

10 ± 2.8

82.6 ± 2.5

Table 3. The results of surgical deformity correction in patients with idiopathic thoracic scoliosis in the immediate and late postoperative periods

Parameters

Immediate results

Long-term results

Group 1

Group 2

Group 1

Group 2

Age

15.6 ± 1.1

15.8 ± 0.7

Gender (male/female)

1/15

1/14

Angle of scoliosis before surgery according to Cobb (°)

56 ± 8.7

62.4 ± 8.0

Percentage of scoliosis mobility (%)

37.8

35.4

Angle of scoliosis after surgery according to Cobb (°)

4 ± 3.5

10 ± 2.8*

7 ± 4.1

11.5 ± 3.1

Percentage of scoliosis correction (%)

92.5 ± 3.2

82.6 ± 2.5

Angle of kyphosis before surgery according to Cobb (°)

20.6 ± 8.7

17.4 ± 5.2

Angle of kyphosis after surgery according to Cobb (°)

21.5 ± 5.0

23 ± 3.3

21.4 ± 6.5

21.9 ± 6.6

Angle of lordosis before surgery according to Cobb (°)

31.2 ± 9.5

28.5 ± 7.3

Angle of lordosis after surgery according to Cobb (°)

25 ± 4.8

27 ± 3.0

26.9 ± 7.0

27.7 ± 5.6

Rotation of apical vertebra before surgery

19.2 ± 4.2

22.1 ± 2.4

Rotation of apical vertebra after surgery

5 ± 1.3

17 ± 1.7*

Percentage of apical vertebra derotation (%)

73.,9

23

Hardware length

11 ± 0.6

11 ± 0.7

Number of support elements (screws) per patient

22 ± 1.3

18 ± 1.2

* differences in parameters between groups are statistically significant.

Comparative analysis of surgical treatment efficacy (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 significant differences in the magnitude of apical vertebra rotation were observed between groups. Postoperatively, the residual apical vertebra rotation in group 1 was significantly 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. The magnitude of spinal scoliotic deformity correction in group 1 (92.5%) was significantly 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 significantly greater than that in group 2 (23%). This 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. The 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. Thus, the magnitude of spinal sagittal profile 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. This 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 efficacy of surgery is slightly lower, but long-term outcomes are maintained. These data indicate that the use of this method is also justified. The 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

The authors declare no conflict of interest related to the manuscript. This work was performed as part of research approved by Turner Scientific and Research Institute for Children’s Orthopedics, Saint Petersburg, Russian Federation.

Nurbek N Nadirov

The Turner Scientific and Research Institute for Children’s Orthopedics

Author for correspondence.
Email: nurbeknadir@mail.ru

Russian Federation MD, PhD student of the department of spine pathology and neurosurgery. The Turner Scientific and Research Institute for Children’s Orthopedics.

Sergei M Belyanchikov

The Turner Scientific and Research Institute for Children’s Orthopedics

Email: belijanchikov@list.ru

Russian Federation MD, PhD, chief of the department of spinel pathology and neurosurgery. The Turner Scientific and Research Institute for Children’s Orthopedics

Dmitriy N Kokushin

The Turner Scientific and Research Institute for Children’s Orthopedics

Email: fake@eco-vector.com

Russian Federation MD, research associate of the department of spinal pathology and neurosurgery. The Turner Scientific and Research Institute for Children’s Orthopedics.

Vladislav V Murashko

The Turner Scientific and Research Institute for Children’s Orthopedics

Email: fake@eco-vector.com

Russian Federation MD, orthopedic and trauma surgeon of the department of spine pathology and neurosurgery. The Turner Scientific and Research Institute for Children’s Orthopedics.

Kirill A Kartavenko

The Turner Scientific and Research Institute for Children’s Orthopedics

Email: fake@eco-vector.com

Russian Federation MD, orthopedic and trauma surgeon of the department of spine pathology and neurosurgery. The Turner Scientific and Research Institute for Children’s Orthopedics.

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Copyright (c) 2016 Nadirov N.N., Belyanchikov S.M., Kokushin D.N., Murashko V.V., Kartavenko K.A.

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