SPINE Volume 39, Number 13, pp E800-E810 ©2014, Lippincott Williams & Wilkins

DEFORMITY

Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis Meta-analysis of Thoracic Kyphosis Yun Cao, MD, Wei Xiong, MD, and Feng Li, MD

Study Design. A quantitative meta-analysis was conducted on publishing studies reporting results of spinal surgery in adolescent idiopathic scoliosis with instrumentation of pedicle screw or hybrid construct. Objective. The primary objective is to get overview of the power to restore thoracic kyphosis using 2 different instrumentations. Summary of Background Data. During the past years, surgery has mainly focused on correcting the coronal curve, but nowadays, the aims of posterior fusion and instrumentation are to achieve a stable, well-balanced spine in the coronal as well as in the sagittal planes. Methods. A PubMed and EMBASE search was conducted using combinations of the key words “hybrid construct” or “pedicle screw” with “adolescent idiopathic scoliosis” up to October 2013. A hand search of reference lists of obtained articles was also performed. Results. A total of 24 studies were identified and included in this meta-analysis. Of this, 12 included pedicle screw group only, 5 included hybrid construct group only, and 7 included both groups. The total number of patients was 1615. Age ranged from 9 to 26 years, with a mean of 15. For pedicle screw group, we got standard mean difference (SMD) as 0.40 (95% confidence interval, 0.31–0.50); I2= 91.4%. For hybrid construct group, we got SMD as 0.15 (95% confidence interval, 0.04–0.26). Both intervals of SMD lay in positive value side. Overall SMD was 0.30 (95% confidence interval, 0.23– 0.37). The positive value of SMD means thoracic kyphosis improves after surgery, whereas negative value means kyphosis loss after surgery. Conclusion. There is overall tendency for both instrumentations to restore thoracic kyphosis. Hybrid construct seems to be more powerful in restoring kyphosis than pedicle screw. Preoperative From the Department of Orthopaedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, People’s Republic of China. Acknowledgment date: December 9, 2013. First revision date: February 24, 2014. Second revision date: March 8, 2014. Acceptance date: March 13, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and reprint requests to Yun Cao, MD, Department of Orthopaedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Road 1095, Wuhan, Hubei, People’s Republic of China; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000342

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important factor was found to be reasonably distributed or balanced. For operative factor, rod stiffness, fashion of hybrid construct, in situ bending, and rod rotation maneuver could have influence on results of kyphosis in different ways. Loss of correction and limited restoration of loss may do exist after correction. Key words: adolescent idiopathic scoliosis, pedicle screw, hybrid construct, thoracic kyphosis, meta-analysis. Level of Evidence: 3 Spine 2014;39:E800–E810

A

dolescent idiopathic scoliosis is a complex 3-dimensional musculoskeletal disorder characterized by lateral spine curvature in the coronal plane, thoracic hypokyphosis in the sagittal plane, and vertebral rotation in the transverse plane. During the past years, surgery has mainly focused on correcting the coronal curve, but nowadays, the aims of posterior fusion and instrumentation are to achieve a stable, well-balanced spine in the coronal as well as in the sagittal planes, prevent curve progression, and also achieve solid fusion, while keeping the fusion as short as possible.1 In the sagittal plane, results are differing in studies concerning scoliosis populations with thoracic hypokyphosis. Some authors have found an increase of kyphosis with hook, screw, or hybrid constructs whereas others have found no change or decrease of kyphosis with the same type of constructs particularly in recent studies.2–7 Most of the authors found an important number of cases remaining in hypokyphosis after surgery and a postoperative angle of kyphosis close to the inferior value. It seems that there is no ideal instrumentation in regard to sagittal plane correction.8 The purpose of the study is (1) to get an overview of the power to restore thoracic kyphosis using 2 different instrumentations, (2) to compare the efficacy of kyphosis restoration, and (3) to investigate the source of heterogeneity among the studies.

MATERIALS AND METHODS Search Strategy A PubMed and EMBASE search was conducted using combinations of the key words “hybrid construct” or “pedicle

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Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

screw” with “adolescent idiopathic scoliosis” up to October 2013. A hand search of reference lists of obtained articles was also performed.

(if available); (23) preoperative sagittal balance; and (24) implant density.

Inclusion/Exclusion Criteria

Thoracic kyphosis from the included studies was grouped according to whether all-pedicle screws (>80%) were implanted or hybrid construct. A random-effects model acknowledges that the effect of treatment may not be identical from study to study because of heterogeneity. To study the source of heterogeneity, we conducted metaregression with some candidate potential factors, such as anchors type, Risser grade, flexibility of thoracic curve, and sagittal balance. Furthermore, we identified studies that included both pedicle screw group and hybrid construct group and applied metaanalysis of these studies alone. Most of the statistics underwent with the assistance of software Stata 12.0 (StataCorp LP, College Station, TX).

Only articles that reported all of the following information were included: (1) the patient population was adolescent idiopathic scoliosis only; (2) the intervention groups included pedicle screw group, hybrid construct group, or both; and (3) thoracic kyphosis result was reported. Pedicle screw group must satisfy that pedicle screws consisted more than 80% of anchors implanted. Hybrid construct group must satisfy that proximal hooks, wires, or clamps combined with distal pedicle screws were implanted. Articles were excluded if they matched 1 of these conditions: (1) patient population was mixed with other scoliosis, such as adult adolescent scoliosis, congenital scoliosis; (2) only anterior spinal fusion was used; (3) curve type of patients was mostly Lenke 5; and (4) article was case report, or review. Furthermore, taken the following reason into consideration, that is, the same institution was more likely to report results observed from the same population, we chose the most suitable one from articles reported by the same institution.

Review Procedure After being selected, studies were screened independently by authors (Yun Cao and Wei Xiong). Reviewers were not blinded to authors and journal. Rather, a study was included for analysis as long as both screeners agreed that it met inclusion criteria. No authors were contacted.

Data Extraction A meta-analysis database was created from included studies with the following categories: (1) study ID (author, journal, year published, institution); (2) reference; (3) study type (e.g., prospective, randomized, controlled, retrospective series); (4) data evidence class. Prospective randomized controlled trials were considered class I evidence. Good quality prospective cohort and retrospective case-control studies were considered class II evidence. Retrospective series and prospective observational studies were considered class III evidence; (5) study patient inclusion/exclusion criteria; (6) description of surgical procedure; (7) total number of patients; (8) patient age statistics including mean, standard deviation, median, and range (if available); (9) number of male and female patients; (10) final follow-up time; (11) number of patients undergoing pedicle screw instrumentation; (12) number of patients undergoing hybrid construct instrumentation; (13) use of monoaxial or polyaxial pedicle screw; (14) type of hybrid construct; (15) special surgical techniques applied (such as simultaneous translation on 2 rods, direct vertebral derotation); (16) distribution of curve types; (17) Cobb angle of thoracic curve; (18) flexibility of thoracic curve; (19) number of fused levels; (20) Risser grade; (21) preoperative thoracic kyphosis statistics including mean, standard deviation, median, and range (if available); (22) postoperative thoracic kyphosis statistics including mean, standard deviation, median, and range Spine

Statistical Analysis

RESULT Description of Study The search identified 117 articles. Of these, 73 were excluded. Excluded studies included case reports, reviews, non-English articles, and articles that did not match inclusion criteria. Of the remaining 44 articles, 4 studies reported mainly Lenke 5 curve, 1 did not include either pedicle screw group or hybrid construct group, and 1 was duplicate. Fourteen articles were excluded because the same institutions reported other articles included. The 24 remaining studies fit criteria and were included in the meta-analysis. Twelve studies included pedicle screw group only,9–20 5 included hybrid construct group only,1,7,21–23 and 7 included both groups.3,6,24–28 Descriptive information for each included study is given in Table 1. The total number of patients was 1615. Age ranged from 9 to 26 years, with a mean number of 15. Of these 24 remaining studies, 12 included pedicle screw group only. The density of screws in each study did vary. In some study, nearly 100% screws were implanted on both concave and convex sides,9 and in some other studies, only concave side needed 100% screws, whereas convex side got 33% to 50% screws.11 Some studies specifies the screw types into monoaxial and polyaxial.923 Furthermore, 3 studies contained more than 1 pedicle screw group because of different surgical techniques.16,17,19 Five studies included hybrid construct group only. Hybrid construct consisted of proximal hooks (can also be wires or clamps) and distal pedicle screws. One study included 2 types of hybrid construct groups because of different anchors,23 in which one was hook and the other was universal clamp. In total, there were 7 studies that included paired-compare groups between pedicle screw group and hybrid construct group. In these studies, main characteristics of preoperative demographics showed no significant difference between pedicle screw group and hybrid construct group, such as age, sex, curve type, and Cobb angle. Preoperative and postoperative thoracic kyphosis is shown in Table 2. For correction index, it equals to (mean of postoperative kyphosis/mean of preoperative kyphosis − 1) × 100% and was www.spinejournal.com

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TABLE 1. Characteristics of Included Study

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25 24 24 20

PS PS PS PS PS PS (VCA) PS (SR) PS (C-T)

Retro.

Retro.

Prosp.

Retro.

13

14

Retro.

Retro.

Retro.

Retro.

Retro.

Retro.

Retro.

Mladenov et al19

Liljenqvist et al20

Blondel et al21

Sucato et al7

Chaiyamongkol et al22

Krallis et al1

Ilharreborde et al23

18

Retro.

Retro.

Chunguang et al17

Basu et al

Prosp.

Qiu et al16

15

Fu et al

Clement et al

Vallespir et al

Potter et al

12

Retro.

Suk et al

15

PS (SR)

75

75

HC (UC) HC (hook)

43

52

86

60

HC

HC

HC

HC

18

15

PS (DVD)

PS

14

26

PS (CSLRR) PS

24

PS (N-T)

62

25

20

203

116

PS

89

Retro.

Study ID

11

Study Type

Abul-Kasim et al10

PS

Group

Retro.

Number

E802

Hamzaoglu et al9

Age, yr (Range) 15 (13–17)

16 (15–17)

14 (10–18)

15 (13–17)

15 (12–18)

15 (13–18)

15 (16–18)

15 (13–17)

14 (9–23)

15 (10–17)

16 (11–21)

15 (10–20)

14 (13–16)

15 (12–22)

12 (10–24)

14 (12–15)

14 (9–18)

15 (12–24)

16 (13–19)

Sex (Female/ Male) 59/16

64/11

29/14

44/8

52/8

11/3

58/12

54/8

94/22

77/12

Risser Sign 3

3.8

3.6

3

Flexibility 0.42

0.47

0.48

0.624

0.623

0.55

0.6

0.49

0.54

0.51

Sagittal balance 15.48

1.7

1.9

30.5

24.5

16.5

16.1

16.6

Fused Level 12

14

10.5

10

12

7.7

Lenke 1 0.48

0.51

0.74

0.44

0.53

1

1

0.91

0.91

0.91

1

1

0.64

0.63

1

1

0.52

0

Lenke 3 0.08

0.03

0.09

0.06

0.46

0

0

0

0

0

0

0

0.12

0.02

0

0

0.16

0.52

Follow-up ≥2 yr

≥2 yr

≥2 yr

≥2 yr

2y

3m

≥2 yr

≥2 yr

≥2 yr

1 (1–2) yr

≥2 yr

≥2 yr

≥2 yr

IP

IP

2y

IP

IP

4.6 (2–7) yr

≥5 yr

6 wk

5.4(2–8) yr

Category of Hybrid Construct H+ W

UC

H+ W

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Y

Y

Y

Y

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

N

Y

N

In situ Bending (Continued )

N

N

Y

N

6.35SS

H+ W

N

N

Y

Y

N

Y

Y

Y

Y

N

Y

N

N

5.5Ti

5.5Ti

5.5Ti

5.5Ti

5.5Ti

5.5Ti

6.0Ti

N

Y

Y

Y

H+ W

UC

Rod Stiffness 5.5Ti

Rod Rotation N

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Retro.

Retro.

Retro.

Retro.

Retro.

Lowenstein et al6

Lonner et al25

Silvestre et al26

Crawford et al27

Yilmaz et al28

33 33 25

PS (POLY) HC PS

29 35 35

HC PS HC

34

34

PS (MONO)

PS

17

HC

27

17

PS

HC

29

29

PS HC

71

HC

56

PS

Age, yr (Range) 15(11–18)

14 (13–17)

15 (13–16)

15 (11–20)

16 (11–20)

14 (12–16)

14 (12–16)

15 (12–18)

13 (11–18)

14 (10–16)

15 (10–18)

15 (12–21)

14 (12–16)

Sex (Female/Male) 28/7

28/7

26/3

27/7

23/4

16/9

15/2

14/3

25/4

20/9

104/23

Risser Sign 3

3

4

3

2.34

3.04

2.4

2.8

Flexibility 0.42

0.47

0.51

0.52

0.27

0.26

0.5

0.51

0.53

0.47

0.43

0.51

Sagittal balance 42.2

30.5

64

52.5

1.5

3.9

3.9

21.24

28.82

20

19

1.09

0.91

Fused Level 10.1

10.6

12.89

11.84

12

10

11

13

11.7

11.3

10.3

Lenke 1 0.69

0.77

1

1

0.40

0.36

0.61

0.76

0.70

0.48

0.48

0.61

0.68

Lenke 3 0.09

0.09

0

0

0.11

0.12

0.09

0.09

0.12

0.28

0.28

0.07

0.07

Follow-up ≥2 yr

≥2 yr

≥2 yr

≥2 yr

6.7 (4.5–8.5) y

6.7 (4.5–8.5) yr

≥2 yr

≥2 yr

≥2 yr

2m

2m

2 yr

2 yr

≥5 yr

≥5 yr

Category of Hybrid Construct H

H+ W

H

H+ W

H

H+ W

H+ W

Rod Stiffness 5.5Ti

5.5Ti

5.5Ti

5.5Ti

Rod Rotation Y

Y

N

N

Y

Y

N

Y

Y

Y

Y

Y

Y

N

N

Y

Y

N

N

N

N

N

N

N

N

N

N

N

N

N

In situ Bending

Retro. indicates retrospective study; PS, pedicle screw; Prosp. prospective study; VCA, vertebral coplanar alignment; SR, simple rotation; C-T, conventional thoracoplasty; IP, immediate postoperative follow-up; N-T, no thoracoplasty; CSLRR, convex short length rib resection; DVD: direct vertebral derotation; HC, hybrid construct group; UC, universal clamp; MONO, monoaxial screw; POLY, polyaxial screw.

Retro.

Kim et al3

Study ID

Retro.

Study Type

Hwang et al24

Group

Spine

Number

TABLE 1. (Continued )

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Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

listed in Table 2. Most studies measured thoracic kyphosis as T5–T12 Cobb angle in the lateral radiograph. Only 2 studies were claimed as prospectively designed series and the rest 22 were retrospectively series. So, all of the studies were considered class III evidence. We chose the following factors as candidate potential sources of heterogeneity according to clinical and practical consideration: (1) Risser grade; (2) flexibility of thoracic curve; (3) fused level; (4) curve type, which we calculated as the percentage of Lenke 1 and Lenke 3 curve; and (5) sagittal balance, which was usually measured as C7 plumb line’s translation from S1 vertical line in the lateral radiograph and was expressed in millimeter. The results showed in Table 1.

RESULT OF META-ANALYSIS Meta-analysis of all Groups For pedicle screw group, we got standard mean difference (SMD) as 0.40 (95% confidence interval [CI], 0.31–0.50). SMD equals to mean difference of postoperative and preoperative thoracic kyphosis divided by standard deviation. I2= 91.4%. For hybrid construct group, we got SMD as 0.15 (95% CI, 0.04–0.26). Both intervals of SMD lay in positive

Study ID

value side. Overall SMD was 0.30 (95% CI, 0.23–0.37). The positive value of SMD means that thoracic kyphosis improves after surgery, whereas negative value means kyphosis loss after surgery. Details for each study are shown in Figure 1.

Meta-analysis of Paired Groups We chose postoperative thoracic kyphosis of hybrid construct group as control and compared it with pedicle screw group. In this meta-analysis, we got SMD as −0.46 (95% CI, −0.64 to −0.27). The negative values mean that hybrid construct has more power to restore thoracic kyphosis than pedicle screw. This result is shown in Figure 2.

Publication Bias For publication bias, we used Begg’s funnel plot to show. For pedicle screw group, there were 10 of 23 out of the funnel. For hybrid construct group, there were 6 of 13 out of the funnel. Figure 3 shows the result.

RESULT OF METAREGRESSION To explore the source of heterogeneity, we underwent metaregression of several chosen candidate potential sources. Flexibility of thoracic curve was measured by Cobb angle in

%

Pedicle screw group Hamzaogln et al9 Kazi 2011 Suk et al11 potter et al12 Vallespir et al13 Clement et al14 Fu et al15 Qiu et al16 VCA zhou 2011 C-T Basu et al18 Mladenov et al19 DVR Liljenqvist et al20 Hwang et al24 screw Kim et al3screw Lowerstein et al8 screw Lonner et al25 MONO Silvestre et al26 screw Crawford et al27 screw Yilmaz et al28 screw Qui et al16 SR zhou 2011 N-T zhou 2011 CSLRR Mladenon et al19 SR Lonner et al20 POLY Subtotal (I 2 = 91.4%, P = 0.000) Hybrid construct group Blondel et al21 Sucato et al7 Chayamong et al22 Krallis et al1 Ilharreburde et al23 clamp Ilharreburde et al23 hook Hwang et al24 hybrid Kim et al3 hybrid Lowerstein et al6 hybrid Lonner et al25 hybrid Silvestre et al26 hybrid Crawford et al27 hybrid Yilmaz et al28 hybrid Subtotal (I 2 = 80.7%, P = 0.000)

SMD (95% CI)

Weight

1.39 (1.06–1.72)

4.88

1.34 (1.05–1.62)

6.45

0.52 (0.32–0.72)

13.38

–1.66 (-2.38 to 0.93)

1.00

0.06 (-0.50–0.61)

1.70

1.24 (0.86–1.63)

3.53

–0.15 (-0.70–0.41)

1.70

0.79 (0.20–1.38)

1.51

0.64 (0.00–1.27)

1.29

–1.25 (-2.07 to 0.44)

0.79

–1.02 (-1.79 to 0.26)

0.90

0.04 (-0.61–0.70)

1.23

–0.45 (-1.26–0.36)

0.80

–0.70 (-1.23 to 0.17)

1.86

–0.90 (-1.61 to 0.19)

1.05

–0.57 (-1.06 to 0.09)

2.22

–0.57 (-1.13 to 0.00)

1.64

0.95 (0.45–1.46)

2.07

–0.97 (-1.46 to 0.47)

2.13

0.30 (-0.27–0.87)

1.62

0.60 (0.02–1.17)

1.56

1.02 (0.44–1.60)

1.56

0.31 (-0.41–1.03)

1.01

0.00 (-0.48–0.48)

2.25

0.40 (0.31–0.50)

58.13

0.86 (0.49–1.24)

3.74

0.04 (-0.26–0.33)

5.86

-0.09 (-0.48–0.29)

3.54

0.64 (0.21–1.07)

2.79

0.75 (0.42–1.08)

4.77

-0.12 (-0.44–0.20)

5.10

0.35 (0.01–0.68)

4.77

-0.16 (-0.67–0.36)

1.97

-0.35 (-1.03–0.33)

1.14

-0.57 (-1.07 to 0.08)

2.16

-0.46 (-1.00–0.08)

1.79

-0.57 (-1.10 to 0.04)

1.90

0.32 (-0.15–0.79)

2.35

0.15 (0.04–0.26)

41.87

0.30 (0.23–0.37)

100.00

Heterogeneity between groups: P = 0.001

Overall (I 2 = 89.4%, P = 0.000) -1

Kyphosis loss E804

0

1

Kyphosis restore

Figure 1. Meta-analysis of thoracic kyphosis in adolescent idiopathic scoliosis with pedicle screw or hybrid construct instrumentation. The positive values of SMD represent kyphosis restoration after surgery and negative values of SMD represent kyphosis loss after surgery. SMD indicates standard mean difference; VCA, vertebral coplanar alignment; C-T, conventional thoracoplasty; DVR, direct vertebral rotation; MONO, monoaxial screw; SR, simple rotation; N-T, no thoracoplasty; CSLRR, convex short length rib resection; POLY, polyaxial screw.

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Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

Study

%

ID

SM D ( 95 %

Hwang et al24 3

Kim et al

6

Lowenstein et al Lonner et al

25 26

Silvestre et al

27

Crawford et al

CI)

28

Yilmaz et al

Overall (I = 72.7%, P = 0.001) 2

-1

Favors hybrid construct

0

Weight

-0.41 (-0.77 to 0.06)

27.53

-1.04 (-1.59 to 0.49)

11.42

-0.32 (-1.00–0.35)

7.53

-0.14 (-0.62–0.34)

15.00

-0.29 (-0.84–0.26)

11.53

0.14 (-0.35–0.64)

14.02

-1.28 (-1.80 to 0.77)

12.97

-0.46 (-0.64 to 0.27)

100.00

- 0 . 4 1 ( - 0. 77 ,

- 0 . 0 6)

- 1 . 0 4 ( - 1. 59 ,

- 0 . 4 9)

- 0 . 3 2 ( - 1. 00 ,

0. 35 )

- 0 . 1 4 ( - 0. 62 ,

0. 34 )

- 0 . 2 9 ( - 0. 84 ,

0. 26 )

0. 14 ( - 0 . 3 5,

%

SMD (95% CI)

0 . 6 4)

- 1 . 2 8 ( - 1. 80 ,

- 0 . 7 7)

- 0 . 4 6 ( - 0. 64 ,

- 0 . 2 7)

1

Favors pedicle screw

Figure 2. Meta-analysis of thoracic kyphosis in studies including both PS group and hybrid group. The positive value of SMD representing pedicle screw has more power to restore kyphosis, and negative value of SMD representing hybrid construct has more power to restore kyphosis. SMD indicates standard mean difference.

middle and side-bending anterior-posterior radiograph. Sagittal balance was usually measured as distance between C7 plumb line and vertical line of S1 superior posterior edge. Risser grade was defined as 0 to 5 grades according to the

SUBGROUP ANALYSIS Category of Hybrid Construct There were 3 main categories of hybrid construct, that is, hook only fashion, hook plus wires fashion, and universal clamps fashion. According to this situation, we stratified studies to 3 subgroups, respectively. Charts for subgroup analysis on category of hybrid construct are shown in Figure 4A.

Follow-up In included studies, length of follow-up did vary because of different purposes of studies and various realities. To investigate the maintenance of sagittal correction, we stratified studies to 3 subgroups: less than 2 years, a minimum followup of 2 years, and a minimum follow-up of 5 years. Charts for subgroup analysis on length of follow-up are shown in Figure 4B (hybrid construct) and Figure 4C (pedicle screw).

Begg's funnel plot with pseudo 95% confidence limits 2

1

SMD

percentage of bilateral iliac epiphyseal closed surface to assess the maturity of skeletal. Percentage of curve type specified by Lenke classification as type1 (main thoracic curve) and type 3(double main curve) was recorded. We took the SMD of thoracic kyphosis as effect variable and candidate potential sources of heterogeneity (CPSofHG) as assumed dependent variables. Using the software Stata 12.0 for Windows (StataCorp LP, College Station, TX), we got the coefficient of these CPSofHG. As shown in Table 3, all of the coefficient 95% CIs lined on both side of 0 values, P value for test was greater than 0.05 each. According to statistical knowledge, only when the whole interval lines on 1 side of 0 value and P value is less than 0.05, we can say that the factor contributes to the heterogeneity of effect.

0

In situ Bending In situ bending was supposed to directly improve the sagittal curve. Some surgical procedures preferred to use this technique when they considered necessary whereas other surgical procedures found no interest in this technique and chose not to apply it in practice. According to this situation, we stratified studies to 2 subgroups: In situ bending used and in situ bending not used groups. Charts for subgroup analysis on length of follow-up are shown in Figure 4D (hybrid construct) and Figure 4E (pedicle screw).

-1

-2 0

.1

.2 s.e. of: SMD

.3

.4

Begg's funnel plot with pseudo 95% confidence limits 1

Rod Rotation Maneuver

SMD

.5

0

-.5 0

.2 s.e. of: SMD

.4

Figure 3. Begg’s funnel plot of report bias. Top graph represents studies including pedicle screw group, and bottom graph represents studies including hybrid construct group. SMD indicates standard mean difference. Spine

Rod rotation maneuver is one of the basic curve correction methods. But in some studies, they did not use this maneuver. Instead, they used other maneuvers, such as translation technique, vertebral coplanar alignment, and so on. According to this situation, we stratified studies to 2 subgroups: Rod rotation maneuver used and rod rotation maneuver not used groups. Charts for subgroup analysis on lord rotation maneuver are shown in Figure 4F (hybrid construct) and Figure 4G (pedicle screw).

Rod Stiffness Different rod materials and diameters were supposed to have influence on correction of curves. In some studies, they www.spinejournal.com

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Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

TABLE 2. Pre/Postoperative TK of Studies TK Preoperative

TK Postoperative

Group

Mean

SD

Mean

SD

Correction Index (%)

Hamzaoglu et al9

PS

18

5.5

26

6

44.4

Abul-Kasim et al

PS

15.1

8.1

24.8

6.3

64.2

Suk et al

PS

18

11

23

8

27.8

Study ID 10

11

Potter et al

PS

29.4

2.8

25

2.5

−15.0

13

Vallespir et al

PS

18

13.5

18.6

7.3

3.33

14

Clement et al

PS

24

12

24

11

0

Fu et al

PS

21

13.7

34.4

6.7

63.8

PS (VCA)

15.8

10.7

14.5

6.5

−8.2

PS (SR)

18.3

10.5

27.7

13.1

51.4

PS (C-T)

15.5

12.6

19.2

12.4

23.9

PS (N-T)

21.2

8

26.3

8

24.1

PS (CSLRR)

20.1

7.6

24.6

7.5

22.4

PS

20.4

7.8

28.8

8.6

41.2

PS (DVD)

24.38

12.12

12.17

6.55

−50.1

PS (SR)

23.4

9

15.2

6.9

−35.0

Liljenqvist et al

PS

13.9

9.7

16.7

8.3

20.1

Blondel et al

HC

29.6

40

31

23

4.7

HC

18.7

8

24.8

6

32.6

Chaiyamongkol et al

HC

19.3

12.7

19.7

9.5

2.1

Krallis et al

HC

1.7

34.6

−1.3

29.1

−176.5

HC (UC)

24

13

30.7

7.1

27.9

HC (hook)

23.8

14.2

32.3

7.3

35.7

PS

23.6

13.8

22.1

10.7

−6.4

HC

21.7

12.9

16.1

11.8

−25.8

PS

26.3

14.1

30.4

9.1

15.6

HC

26

14

18

8

−30.8

PS

30

14

28

11

−6.7

HC

29.65

13.79

19.35

8.45

−34.7

PS (MONO)

26.24

11.22

22.42

10.47

−14.6

PS (POLY)

27

13

21

7

−22.2

HC

27

13

21

7

−22.2

PS

35.32

19.5

26

12.5

−26.4

HC

35.22

15.25

29.3

10.25

−16.8

PS

17.5

3.5

20.5

2.75

17.1

HC

22

3.75

20

3.25

−9.1

PS

22.1

13.2

11.5

8.1

−48.0

HC

18.4

13.2

21.9

8.1

19.0

12

15

Qiu et al16

Chunguang et al

17

Basu et al

18

Mladenov et al19 20

21

Sucato et al

7 22

1

Ilharreborde et al23 Hwang et al24 Kim et al3 Lowenstein et al6

Lonner et al25

Silvestre et al26 Crawford et al27 Yilmaz et al28

TK indicates thoracic kyphosis; PS, pedicle screw group; VCA, vertebral coplanar alignment; SR, simple rotation; C-T, conventional thoracoplasty; N-T, no thoracoplasty; CSLRR, convex short length rib resection; DVD, direct vertebral derotation; HC, hybrid construct group; UC, universal clamp; MONO, monoaxial screw; POLY, polyaxial screw.

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DEFORMITY

Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

TABLE 3. Metaregression of CPSofHG* Coefficient (95% CI)

P⬎t

Flex.

1.71 (−1.72 to 5.15)

0.309

SB

0.22 (−0.02 to 0.02)

0.897

RG

0.22 (−0.78 to 1.23)

0.631

FL

0.10 (−0.15 to 0.35)

0.406

Lenke 1

−0.44 (−2.15 to 1.26)

0.597

Lenke 3

−0.16 (−3.14 to 3.08)

0.919

CPSofHG

*P < 0.05 is considered as the factor that contributes to the heterogeneity of effect. If coefficient interval goes across both negative and positive values, it means that no evidence supports that the factor contributes significantly to the heterogeneity of effect. CPSofHG indicates candidate potential sources of heterogeneity; CI, confidence interval; Flex., flexibility of thoracic curve; SB, sagittal balance; RG, Risser grade; FL, fused level.

did claim clearly that all included patients got same kind of rod, mainly 5.5-mm titanium alloy rod. We noticed that other kinds of rod were also used in included studies, such as 6.0-mm titanium alloy rod and 6.35-mm stainless steel. In included studies, no studies claimed that they used CoCr alloy rod alone in included patients’ operation. Only 1 latest PS

published article reported its result of CoCr used in vivo.29 Because it was not published when we did our data search earlier, we simply used it as a reference for sensitive test. A number of studies did not verify the rod material or diameters information. According to this situation, we stratified studies to 4 subgroups: 5.5-mm titanium alloy rod, 6.0-mm titanium alloy rod, 6.35-mm stainless steel, and unidentified groups. Charts for subgroup analysis on rod stiffness are shown in Figure 4H (hybrid construct) and Figure 4I (pedicle screw). All the results and details are shown in Table 4.

DISCUSSION In total, 24 articles were included in the analysis. Seven were retrospectively cohort and 2 were prospective series. Overall, the evidence class of article was class III, which is not robust. To avoid introducing more reporting bias, for articles reported by the same institution, we chose only one of them by taking the publishing time and integrity of data into consideration. For quantitative analysis, for both groups, overall effect had positive intervals that showed kyphosis restoration after surgery. For the 7 group-paired studies, we underwent directly comparing the result of postoperative thoracic kyphosis and got a result of comparison between 2 subgroups, which was

SMD (95% CI)

PS

1.39 (1.06 - 1.72)

SMD (95% CI)

-1.66 (-2.38 to -0.93)

1.39 (1.06 - 1.72) 0.52 (0.32 - 0.72) -1.66 (-2.38 to -0.93) 0.06 (-0.50 to 0.61) 1.24 (0.86 - 1.63) -0.15 (-0.70 to 0.41) 0.79 (0.20 - 1.38) 0.64 (0.00 - 1.27) -1.25 (-2.07 to -0.44) -1.02 (-1.79 to -0.26) 0.04 (-0.61 to 0.70) -0.45 (-1.26 to 0.36) -0.70 (-1.23 to -0.17) -0.90 (-1.61 to -0.19) -0.57 (-1.06 to -0.09) -0.57 (-1.13 to -0.00) 0.95 (0.45 - 1.46) 0.30 (-0.27 to 0.87) 0.60 (0.02 - 1.17) 1.02 (0.44 - 1.60) 0.31 (-0.41 to 1.03) 0.00 (-0.48 to 0.48) 0.34 (0.24 - 0.45)

-0.15 (-0.70 to 0.41) 0.64 (0.00 - 1.27)

HC

HC

SMD (95% CI)

-1.02 (-1.79 to -0.26)

SMD (95% CI)

0.04 (-0.61 to 0.70)

HC

-0.70 (-1.23 to -0.17) -0.57 (-1.06 to -0.09)

0.04 (-0.26 to 0.33) -0.09 (-0.48 to 0.29) 0.64 (0.21 - 1.07) 0.75 (0.42 - 1.08) -0.12 (-0.44 to 0.20) -0.16 (-0.67 to 0.36) -0.57 (-1.07 to -0.08) -0.57 (-1.10 to -0.04) 0.32 (-0.15 to 0.79) 0.09 (-0.04 to 0.22)

0.86 (0.49 - 1.24) 0.75 (0.42 - 1.08) 0.80 (0.55 - 1.05)

UC group 0.04 (-0.26 to 0.33) -0.09 (-0.48 to 0.29) 0.64 (0.21 - 1.07) 0.35 (0.01 - 0.68) -0.16 (-0.67 to 0.36) -0.57 (-1.07 to -0.08) -0.57 (-1.10 to -0.04) 0.03 (-0.12 to 0.18)

0.60 (0.02 - 1.17) 1.02 (0.44 - 1.60) 0.31 (-0.41 to 1.03) 0.00 (-0.48 to 0.48) 0.20 (0.06 - 0.34)

a minimun of 2 yr 1.34 (1.05 - 1.62) 0.06 (-0.50 to 0.61) 1.24 (0.86 - 1.63) -1.25 (-2.07 to -0.44) 0.82 (0.64 - 1.01)

less than 2 yr 0.52 (0.32 - 0.72)

0.35 (0.01 - 0.68) -0.46 (-1.00 to 0.08) 0.13 (-0.16 to 0.41)

B

0.15 (0.04 - 0.26)

-0.09 (-0.48 to 0.29) 0.64 (0.21 - 1.07) 0.75 (0.42 - 1.08) -0.12 (-0.44 to 0.20) 0.32 (-0.15 to 0.79) 0.28 (0.11 - 0.45)

-0.90 (-1.61 to -0.19)

-0.45 (-1.26 to 0.36) -0.57 (-1.13 to -0.00) 0.36 (0.18 - 0.54)

a minimun of 5 yr

0.15 (0.04 - 0.26)

In situ bending (-)

0.79 (0.20 - 1.38)

less than 2 yr

Hook only

0.86 (0.49 - 1.24) 0.04 (-0.26 to 0.33) 0.35 (0.01 - 0.68) -0.16 (-0.67 to 0.36) -0.35 (-1.03 to 0.33) -0.57 (-1.07 to -0.08) -0.46 (-1.00 to 0.08) -0.57 (-1.10 to -0.04) 0.05 (-0.10 to 0.20)

0.30 (-0.27 to 0.87)

0.86 (0.49 - 1.24) -0.35 (-1.03 to 0.33) 0.58 (0.25 - 0.91)

-0.12 (-0.44 to 0.20) -0.35 (-1.03 to 0.33) -0.46 (-1.00 to 0.08) 0.32 (-0.15 to 0.79) -0.10 (-0.33 to 0.12)

A

-0.97 (-1.46 to -0.47)

a minimun of 2 yr

Hook + Wire

SMD (95% CI)

0.95 (0.45 - 1.46)

0.40 (0.31 - 0.50)

D

In situ bending (+)

0.15 (0.04 - 0.26)

PS PS

1.34 (1.05 - 1.62) -0.97 (-1.46 to -0.47) 0.77 (0.52 - 1.01)

In situ bending (+)

a minimun of 5 yr

C

In situ bending (-)

E

0.40 (0.31 - 0.50)

SMD (95% CI)

SMD (95% CI) 1.39 (1.06 - 1.72) 0.52 (0.32 - 0.72)

HC

1.39 (1.06 - 1.72) 0.06 (-0.50 to 0.61) 1.24 (0.86 - 1.63) 0.79 (0.20 - 1.38) -1.25 (-2.07 to -0.44) 0.04 (-0.61 to 0.70) -0.45 (-1.26 to 0.36) 0.95 (0.45 - 1.46) 0.80 (0.62 - 0.97)

SMD (95% CI)

0.86 (0.49 - 1.24) 0.04 (-0.26 to 0.33) -0.09 (-0.48 to 0.29) 0.75 (0.42 - 1.08) -0.12 (-0.44 to 0.20) 0.35 (0.01 - 0.68) -0.57 (-1.07 to -0.08) -0.57 (-1.10 to -0.04) 0.17 (0.04 - 0.30)

Rod rotation (+)

G

0.64 (0.00 - 1.27) 0.04 (-0.61 to 0.70) -0.45 (-1.26 to 0.36) -0.90 (-1.61 to -0.19) -0.57 (-1.06 to -0.09) -0.57 (-1.13 to -0.00) 0.95 (0.45 - 1.46) 0.60 (0.02 - 1.17) 1.02 (0.44, 1.60) 0.00 (-0.48 to 0.48) 0.35 (0.23 - 0.47)

unidentified 1.34 (1.05 - 1.62)

unidentified

-0.15 (-0.70 to 0.41)

0.86 (0.49 - 1.24) -0.16 (-0.67 to 0.36) 0.32 (-0.15 to 0.79) 0.45 (0.20 - 0.71)

-1.02 (-1.79 to -0.26)

0.79 (0.20 - 1.38) -0.70 (-1.23 to -0.17) -0.97 (-1.46 to -0.47) 0.30 (-0.27 to 0.87) 0.31 (-0.40 to 1.03)

5.5 mm Ti alloy rod

0.35 (0.18 - 0.53)

5.5 mm Ti alloy rod

-0.09 (-0.48 to 0.29) -0.09 (-0.48 to 0.29)

1.24 (0.86 - 1.63) 1.24 (0.86 - 1.63)

6.35 mm stainless steel rod

Rod rotation (+) 0.40 (0.31 - 0.50)

0.64 (0.00 to 1.27)

0.04 (-0.26 to 0.33) 0.64 (0.21 - 1.07) 0.75 (0.42 - 1.08) -0.12 (-0.44 to 0.20) 0.35 (0.01 - 0.68) -0.35 (-1.03 to 0.33) -0.57 (-1.07 to -0.08) -0.46 (-1.00 to 0.08) -0.57 (-1.10 to -0.04) 0.10 (-0.03 to 0.23)

1.34 (1.05 - 1.62) 0.52 (0.32 - 0.72) -1.66 (-2.38 to -0.93) -0.15 (-0.70 to 0.41) 0.64 (0.00 - 1.27) -1.02 (-1.79 to -0.26) -0.70 (-1.23 to -0.17) -0.90 (-1.61 to -0.19) -0.57 (-1.06 to -0.09) -0.57 (-1.13 to -0.00) -0.97 (-1.46 to -0.47) 0.30 (-0.27 to 0.87) 0.60 (0.02 - 1.17) 1.02 (0.44 - 1.60) 0.31 (-0.41 to 1.03) 0.00 (-0.48 to 0.48) 0.25 (0.14 to 0.36)

0.64 (0.21 - 1.07) -0.16 (-0.67 to 0.36) -0.35 (-1.03 to 0.33) -0.46 (-1.00 to 0.08) 0.32 (-0.15 to 0.79) 0.10 (-0.13 to 0.33)

F

0.06 (-0.50 to 0.61)

Rod rotation (-)

Rod rotation (-)

0.15 (0.04 - 0.26)

-1.66 (-2.38 to -0.93)

HC

SMD (95% CI)

H

0.15 (0.04 - 0.26)

6.0 mm Ti alloy rod

I

0.40 (0.31 - 0.50)

Figure 4. A–I, Subgroup analysis on category of hybrid construct, length of follow-up, rod rotation, in situ bending, and rod stiffness. PS, pedicle screw; HC, hybrid construct. Spine

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DEFORMITY

Pedicle Screw Versus Hybrid Construct Instrumentation in Adolescent Idiopathic Scoliosis • Cao et al

TABLE 4. Subgroup Analysis of TK Hybrid Construct

Pedicle Screw

SMD

95% CI

SMD

95% CI

Pedicle screw versus hybrid construct instrumentation in adolescent idiopathic scoliosis: meta-analysis of thoracic kyphosis.

A quantitative meta-analysis was conducted on publishing studies reporting results of spinal surgery in adolescent idiopathic scoliosis with instrumen...
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