Determination of Distal Fusion Level with Segmental Pedicle Screw Fixation in Single Thoracic Idiopathic Scoliosis

Se-Il Suk; Jin-Hyok Kim; Sang-Min Lee; Ewy-Ryong Chung; Ki-Ho Nah; Jung-Hee Lee; Sung-Soo Kim; Soo-Chul Park; Rack-Yong Chung; Sung-Wook Won

doi:10.4184/jkss.2002.9.2.98

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Suk, Kim, Lee, Chung, Nah, Lee, Kim, Park, Chung, and Won: Determination of Distal Fusion Level with Segmental Pedicle Screw Fixation in Single Thoracic Idiopathic Scoliosis

Original Article

Journal of Korean Spine Surg 2002;9(2):98-105.

Published online: 21 February 2002

DOI: https://doi.org/10.4184/jkss.2002.9.2.98

Determination of Distal Fusion Level with Segmental Pedicle Screw Fixation in Single Thoracic Idiopathic Scoliosis

Se-Il Suk, M.D., Jin-Hyok Kim, M.D., Sang-Min Lee, M.D., Ewy-Ryong Chung, M.D., Ki-Ho Nah, M.D.^∗, Jung-Hee Lee, M.D., Sung-Soo Kim, M.D., Soo-Chul Park, M.D., Rack-Yong Chung, M.D., Sung-Wook Won, M.D.

Seoul Spine Institute, Inje University Sanggye Paik Hospital

^∗Dept. of Orthopaedic Surgery. St. Paul's Hospital. Catholic University of Korea School of Medicine

Address reprint requests to Ewy-Ryong Chung, M.D. Seoul Spine Institute, Inje University Sanggye Paik Hosital 761-1 Sanggye Dong, Nowon-Ku, Seoul 139-707, Korea Tel : 82-2-950-1290, Fax : 82-2-3392-1101, E-mail : dragon@sanggyepaik.ac.kr

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Study Design

Retrospective study.

Objectives

To determine the exact distal fusion level in the treatment of single thoracic idiopathic scoliosis (King III and IV) with segmental pedicle screw fixation and rod rotation.

Summary of Literature Review

Pedicle screw fixation effectively shortens the distal fusion extent by improved 3- D deformity correction. However, the selection of distal fusion extent remains controversial in single thoracic idiopathic scoliosis.

Material and Methods

Forty- two single thoracic adolescent idiopathic scoliosis patients subject to segmental pedicle screw fixation and rod rotation with minimum followup of 2 years (2∼6 years) were analyzed. The patients were grouped according to the distal fusion level with reference to the standing neutral vertebra (NV) for comparison of deformity correction, radiological and clinical spinal balance using standing radiographs. Distal fusion down to NV +1 was in 9 patients, NV in 5, NV- 1 in 9, NV-2 in 12 and NV- 3 in 7 patients respectively.

Results

Preoperative 50± 11° of thoracic deformity was corrected to 13± 5° showing 74% of curve correction. Preoperative 23± 7° of lumbar deformity was corrected to 2± 8° showing 93% of curve correction. Postoperative adding on deformity was obtained in 14 patients. Significant difference was found not by King classification but by distal fusion level: significantly higher chance of unsatisfactory results from not going to the NV- 1(p=0.001).

Conclusions

In correction of single thoracic idiopathic scoliosis with segmental pedicle screw fixation, the curve should be fused to NV- 1saving one or more motion segments when compared to the fusion to the stable vertebra.

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Keywords: A dolescent idiopathic scoliosis, Single thoracic curve, Distal fusion level, Pedicle screw fixation, Rod rotation

REFERENCES

1). Arlet V, Marchesi D, Papin P, Aebi M. Decompensation following scoliosis surgery: treatment by decreasing the correction of the main thoracic curve of “ letting the spine go”. Eur spine J. 9:156–60. 2000.

2). Benli IT, Tuzuner M, Akaline S, Kis M, Ayden E, Tandogan R. Spinal imbalance and decompensation problems in patients treated with Cotrel-Dubousset instru - mentation. Eur Spine J. 5:380–6. 1996.

3). Bridwell KH, McAllister JW, Betz RR, Huss G, Clancy M, Schoenecker PL. Coronal decompensation produced by Cotrel-Dubousset “derotat ion” maneuver for idiopathic right thoracic scoliosis. Spine. 16:769–77. 1991.

4). Cochran T, Irstam L, Nachemson A. Long term anatomic and functional changes in patients with adolescent idiopathic scoliosis treated by Harrington rod fusion. Spine. 8:576–84. 1983.

5). Cotrel Y, Dubousset J, Guillaumat M. New universal instrumentation in spinal surgery. Clin Orthop, Feb;. 227:10–23. 1988.

6). King HA, Moe JH, Bradford DS, Winter RB. The selection of fusion levels in thoracic idiopathic scoliosis. J Bone Joint Surg [Am]. 65:1302–13. 1983.

7). Lenke LG, Betz RR, Bridwell KH, Harms J, Clements DH, Lowe TG. Spontaneous lumbar curve coronal correction after selective anterior or posterior thoracic fusion in adolescent idiopathic scoliosis. Spine. 24:1663–71. 1999.

8). Lenke LG, Bridwell KH, Baldus C, Blanke K, Schoenecker PL. Cotrel-dubousset Instrumentation for Adolescent idiopathic Scoliosis. J Bone Joint Surg [Am]. 74:1056–67. 1992.

9). Margulies JY, Floman Y, Robin GC, Neuwirth MG, Kuflik P, Weidenbaum M, Farcy JP. An algorithm for selection of instrumentation levels in scoliosis. Eur Spine J. 7:88–94. 1998.

10). Mason DE, Carango P. Spinal decompensation in Cotrel-Dubousset instrumentation. Spine. 8:S394–403. 1991.

11). Moore MR, Baynham GC, Brown CW, Donaldson DH, Odom JA Jr. Analysis of factors related to truncal decompensation following Cotrel-Dubousset instrumentation. J Spinal Disord. 4:188–92. 1991.

12). Suk SI, Kim JH, Kim WJ, Lee SM, Liu Yi, Lee CS, Chung ER, Yoon YS. Restoration of thoracic kyphosis in idiopathic scoliosis - A comparison between multiple hook and segmental pedicle screw fixation in adolescent idiopathic scoliosis(AIS). J of Korean Spine Surg. 5:184–92. 1998.

13). Suk SI, Lee CK, Kim WJ, Park YB, Chung YJ, Song KY. Segmental pedicle screw fixation in the treatment of thoracic idiopathic scoliosis. J of Korean Orthop Assoc. 30:49–58. 1995.

14). Suk SI, Kim WJ, Lee SM, Kim JH, Chung ER. Thoracic pedicle screw fixation in spinal deformities. Are they really safe Spine. 26:2049–57. 2001.

15). Shufflebarger HL, Clark CE. Fusion levels and hook patterns in thoracic scoliosis with Cotrel-Dubousset instrumentation. Spine. 15:916–20. 1990.

16). Thompson JP, Transfeldt EE, Bradford DS, Ogilvie JW, Bouchie-Adjei O. Decompensation after Cotrel-Dubousset instrumentation of idiopathic scoliosis. Spine. 15:927–31. 1990.

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Figures and Tables%

Fig. 1-A.

Preoperative standing anteroposterior radiograph of a 15.8 year old female with 50。 thoracic and 32。 lumbar fractional curve. As determined by the spinous process and pedicle shadows, the neutral vertebrae was L1. Fig. 1-B. Preoperative standing lateral radiograph. Fig. 1-C. Anteroposterior radiograph taken 3.5 years after surgery. The distal fusion was down to neutral vertebra(NV). The thoracic curve is corrected to 10。 with 9。 lumbar fractional curve and balanced spine. Fig. 1-D. Lateral radiograph taken 3.5 years after surgery.

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Fig. 2-A.

Preoperative standing anteroposterior radiograph of a 12.4 year old female with 58。 thoracic and 30。 lumbar fractional curve. As determined by the spinous process and pedicle shadows, the neutral vertebrae was L3. Fig. 2-B. Preoperative standing lateral radiograph. The thoracic spine was hypokyphotic, 4。 of kyphosis. Fig. 2-C. Anteroposterior radiograph taken 4 years after surgery. The distal fusion was down to NV-1 (one level proximal to neutral vertebra). The thoracic curve is corrected to 3。 with 29。 lumbar fractional curve and balanced spine. Fig. 2-D. Lateral radiograph taken 4 years after surgery. The thoracic kyphosis was improved to 25。.

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Fig. 3-A.

Preoperative standing anteroposterior radiograph of a 14.8 year old female with 51。 thoracic and 21。 lumbar fractional curve. As determined by the spinous process and pedicle shadows, the neutral vertebrae was L3. Fig. 3-B. Preoperative standing lateral radiograph. Fig. 3-C. Anteroposterior radiograph taken 2 weeks after surgery. The distal fusion was down to NV-2 (two level proximal to neutral vertebra). The thoracic curve was corrected to 14。 with 2。 lumbar fractional curve and balanced spine. Fig. 3-D. Anteroposterior radiograph taken 3 years after surgery. The lumbar fractional curve shows reversal, resulting in extension of the index thoracic curve into the lumbar segments through adding on. Fig. 3-E. Lateral radiograph taken 3 years after surgery.

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Table 1.

Preoperative and postoperative curve characteristics.

	Type III	Type IV	Total
No. of Patients	32	10	42
Thoracic
Preoperative Curves	47.7± 7.9。	58.8± 13.6。	50.3± 10.5。
	(40~67)	(41~85)	(40~85)
Postoperative Curves	12.1± 5.3。	16.2± 4.4。	13.0± 5.3。
	(2~23)	(8~22)	(2~23)
Correction Rate	74.7± 10.2%	71.7± 8.4%	74.0± 9.8%
	(47.7~95.6)	(53.7~86.9)	(47.7~95.6)
Lumbar
Preoperative Curves	22.7± 7.2。	25.4± 6.5。	23.4± 7.0。
	(12~49)	(15~35)	(12~49)
Postop. Curves	2.5± 7.8。	2.1± 7.6。	2.4± 7.7。
	(-12~17)	(-12~14)	(-12~17)
Correction Rate	93.1± 35.6%	94.2± 31.0%	93.4± 34.2%
	(47.4~180.0)	(53.3~157.1)	(47.4~180.0)
Postoperative spinal balance	27/32	8/10	35/42
Postoperative lumbar adding on deformity	9/32	5/10	14/42

Table 2.

Comparison between satisfactory and unsatisfactory results.

	Satisfactory	Unsatisfactory
Type III	23/32 (72%)	9/32 (28%)
Type IV	5/10 (50%)	5/10 (50%)
NV-EV^∗	1.7± 1.6	3.3± 0.9
DF	13.0± 1.1	13.3± 1.1
DF-NV^∗	-0.4± 1.3	-2.4± 0.5
DF-EV	1.3± 0.6	0.9± 1.0
DF-SV	-1.9± 1.3	-2.6± 0.8
Thoracic Curve
Preoperative	50.6± 9.4。	49.6± 12.9。
Flexibility	64.4± 8.0%	61.3± 9.0%
Postoperative	12.7± 5.5。	12.8± 5.0。
Correction Rate	75.2± 9.4%	71.6± 10.5%
Lumbar Curve
Preoperative	24.6± 7.0。	20.9± 6.7。
Flexibility	115.5± 17.3%	120.8± 27.4%
Postoperative^∗	4.9± 5.5。	-2.6± 9.0。
Correction Rate^∗	80.4± 20.4%	119.4± 41.6%

NV : neutal vertebrae

EV : end vertebra

DF : distal fusion level. L1 was counted as 13, and L2 was 14, and so on.

SV : stable vertebra

Flexibility (%) = (preoperative angle-bending angle / preoperative angle) × 100

^∗ p<0.01 in Mann-Whitney test.

Table 3.

Postoperative adding on according to the relationships between the neutral vertebra (NV) and end vertebra (EV)

NV - EV	DF-NV Total					Total
NV - EV	1	0	-1	-2	-3	Total
0	0 / 9 (0%)					0 / 9 (0%)
1	0	0 / 5 (0%)				0 / 5 (0%)
2			0 / 6 (0%)	3 / 3 (100%)		3 / 9 (33%)
3			0 / 2 (0%)	2 / 3 (67%)	3 / 3 (100%)	5 / 8 (63%)
4			0 / 1 (0%)	3 / 4 (75%)	2 / 4 (50%)	5 / 9 (56%)
5				1 / 2 (50%)		1 / 2 (50%)
Total	0 / 9 (0%) 0	0 / 5 (0%)	0 / 9 (0%)	9 /12 (75%)	5 / 7 (71%)	14 / 42 (33%)

NV : neutal vertebrae

EV : end vertebra

DF : distal fusion level

^∗ Significant difference of postoperative spinal imbalance and adding on between fusion below NV-1 groups (NV+1, NV and NV-1 and above NV-1 groups (NV-2, NV-3) (p<0.01).

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