Changes in the Adjacent Segment After Thoracolumbar Posterior Instrumentation and Fusion Surgery in Thoracolumbar Junction Fractures

Tae-Keun Ahn; Tae-Ho Kim; Sang-Jun Lee; Chul-Gie Hong; Dong-Eun Shin; Youngsuk Sim

doi:10.4184/jkss.2017.24.3.147

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Ahn, Kim, Lee, Hong, Shin, and Sim: Changes in the Adjacent Segment After Thoracolumbar Posterior Instrumentation and Fusion Surgery in Thoracolumbar Junction Fractures

Original Article

Journal of Korean Spine Surg 2017;24(3):147-152.

Published online: 30 September 2017

DOI: https://doi.org/10.4184/jkss.2017.24.3.147

Changes in the Adjacent Segment After Thoracolumbar Posterior Instrumentation and Fusion Surgery in Thoracolumbar Junction Fractures

Tae-Keun Ahn, M.D., Tae-Ho Kim, M.D., Sang-Jun Lee, M.D., Chul-Gie Hong, M.D.^∗, Dong-Eun Shin, M.D., Youngsuk Sim, M.D.

Department of Orthopaedic Surgery, CHA Bundang Medical Center, CHA University, Korea

^∗Department of Orthopaedic Surgery, CHA Gumi Medical Center, CHA University, Korea

Corresponding author: Dong-Eun Shin, M.D. ORCID ID: https://orcid.org/0000-0002-8072-2358 Department of Orthopaedic Surgery, CHA Bundang Medical Center, CHA University, 59 Yatap-ro, Bundang-gu, Seongnam-si, Gyeonggi-do 13496, Korea TEL: +82-31-780-5289, FAX: +82-31-708-3578 E-mail: shinde@cha.ac.kr

Received 3 November 20161 March 2017 Accepted 3 June 2017

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) 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 evaluate changes in the adjacent segment after posterior instrumentation and fusion in thoracolumbar spinal fractures.

Summary of Literature Review

The incidence of adjacent-segment disease is increasing as spinal surgery becomes more common. Many studies have been conducted on the risk factors for adjacent-segment changes in the lumbar spine, but few articles have been published on this topic in the thoracolumbar spine.

Material and Methods

The records of 50 patients who received treatment from 2000 to 2013 were reviewed retrospectively. They underwent posterior instrumentation and fusion due to thoracolumbar fracture and were followed up for more than 2 years. To evaluate changes in the adjacent segment, immediate postoperative and last follow-up values of the sagittal angle, disc height, and disc angle were compared between groups divided by age (more or less than 50 years), laminectomy, and fusion levels. The Pfirrmann grade of the discs proximal and distal to the fusion level was also measured using preoperative magnetic resonance imaging.

Results

Thirty-six patients were male and 14 were female. The average age of the 50 patients was 45.6 years, and the mean follow-up period was 4.3 years. There were no cases of adjacent-segment disease. The mean kyphotic sagittal angle progression was 6.8° (range, −11° to 28.5°, p=0.000). The mean change of disc height of the proximal adjacent segment was 0.3 mm (range, −1.6 to 3.4 mm, p=0.013) and 0.6 mm (range, −4.1 to 5.8 mm, p=0.013) in the distal adjacent segment. Laminectomy did not make a significant difference. In the group below 50 years of age, the angle of the adjacent segment discs increased by 0.8° (range, −3.1° to 5.1°, p=0.004) at the proximal adjacent segment and by 0.5°(range, −4.8° to 2.9°, p=0.016) at the distal adjacent segment. Proximal adjacent disc height decreased as the fusion levels increased. As the preoperative Pfirrmann grade increased, degenerative changes in the proximal adjacent segment disc tended to accelerate.

Conclusions

Adjacent-segment disease after lumbar fusion surgery was not found in adjacent segments of the thoracolumbar spine. This seems to be due to the anatomical characteristics of the lumbar spine, which is more flexible than the thoracolumbar vertebra. The mobile segments of the lumbar spine may account for this difference, rather than the instrumentation and fusion procedure itself.

Keywords: Thoracolumbar spine, Fusion, Adjacent segment degeneration, ASD

REFERENCES

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Fig. 1.

Radiologic measurements of the adjacent segments. (A) Measurement of the segmental sagittal angle. (B) Measurement of the disc angle in the proximal and distal adjacent segments. (C) Measurement of the disc height from the midpoint of the proximal segment to the midpoint of the distal adjacent segment.

Table 1.

Baseline data of patients

Variable	Value
Gender (Male:Female)	36:14
Age
<50 (n)	27
>50 (n)	23
Mean age (years)	45.6
Mean follow up (years)	4.3
Fusion levels
2 levels (n)	17
> 2 levels (n)	33

Table 2.

Surgical level analysis through fracture site

Fracture site	Surgical level UIV ∼ LIV	n
T11	T9 ∼ T11	1
	T10 ∼ L1	6
T12	T11 ∼ L1	4
	T11 ∼ L2	1
L1	T10 ∼ L2	1
	T11 ∼ L2	4
	T11 ∼ L3	2
	T12 ∼ L2	8
L2	T12 ∼ L3	6
	T12 ∼ L4	1
	L1 ∼ L3	3
L3	L2 ∼ L4	1
T12, L1	T10 ∼ L3	1
	T11 ∼ L3	1
	T10 ∼ L2	2
	T11 ∼ L2	2
L1, L2	T11 ∼ L4	1
L1, L2	T12 ∼ L3	2

UIV: Uppermost instrumented vertebra, LIV: Lowest instrumented vertebra.

Table 3.

Intraclass correlation coefficient of variables

	ICC	95% CI
Difference of sagittal angle	0.995	0.992-0.997
Difference of proximal adjacent disc height	0.878	0.805-0.927
Difference of distal adjacent disc height	0.962	0.940-0.977
Difference of proximal adjacent disc angle	0.975	0.960-0.985
Difference of distal adjacent disc angle	0.985	0.976-0.991

Table 4.

Differences of radiologic parameters between postoperative and last follow up

	Mean±SD (min∼max)	Confidence Interval		p-value
	Mean±SD (min∼max)	Upper limit	Lower limit	p-value
Difference of sagittal angle	6.8±6.64 (−11.0-28.5)	4.91877	8.69723	0.000
Difference of proximal adjacent disc height	0.3±0.92(−1.6-3.4)	0.07408	0.60192	0.013
Difference of distal adjacent disc height	0.6±1.59(−4.1-5.8)	0.13032	1.03768	0.013
Difference of proximal adjacent disc angle	0.2±1.69(−3.1-5.2)	−0.27422	0.69022	0.390
Difference of distal adjacent disc angle	−0.4±2.75(−7.2-5.6)	−1.18022	0.38422	0.312

Statistics method – Paired t-test.

Table 5.

Correlation between radiologic parameter and Pfirrmann grade

	Pearson correlation	p-value
Difference of proximal adjacent disc height	−0.308	0.029
Difference of proximal adjacent disc angle	−0.313	0.027

Statistics method – Pearson correlation analysis.

Table 6.

Mean differences of radiologic parameters between postoperative and last follow up according to the age.

		Mean±SD	p-value
Mean difference of sagittal angle	<50 years	6.5±4.4	0.736
Mean difference of sagittal angle	>50 years	7.1±8.6
Mean difference of proximal adjacent disc height	<50 years	0.6±0.94	0.029
Mean difference of proximal adjacent disc height	>50 years	0.03±0.82
Mean difference of distal adjacent disc height	<50 years	0.7±1.76	0.657
Mean difference of distal adjacent disc height	>50 years	0.5±1.40
Mean difference of proximal adjacent disc angle	<50 years	0.8±1.6	0.004
Mean difference of proximal adjacent disc angle	>50 years	−0.5±1.5
Mean difference of distal adjacent disc angle	<50 years	0.5±2.3	0.016
Mean difference of distal adjacent disc angle	>50 years	−1.4±2.89

Statistics method Independent-sample t-test.

Table 7.

Mean differences of radiologic parameters between postoperative and last follow up according to the fusion levels.

		Mean±SD	p-value
Mean difference of sagittal angle	2 levels	6.5±4.9	0.148
Mean difference of sagittal angle	≥3 levels	6.9±7.45	0.148
Mean difference of proximal adjacent disc height	2 levels	0.4±1.01	0.964
Mean difference of proximal adjacent disc height	≥3 levels	0.3±0.89	0.964
Mean difference of distal adjacent disc height	2 levels	0.9±1.11	0.269
Mean difference of distal adjacent disc height	≥3 levels	0.4±1.79	0.269
Mean difference of proximal adjacent disc angle	2 levels	0.1±1.54	0.990
Mean difference of proximal adjacent disc angle	≥3 levels	0.3±1.78	0.990
Mean difference of distal adjacent disc angle	2 levels	−0.2±1.97	0.460
Mean difference of distal adjacent disc angle	≥3 levels	−0.5±3.1	0.460

Statistics method Independent-sample t-test.

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