J Korean Soc Spine Surg.  2019 Dec;26(4):132-140. 10.4184/jkss.2019.26.4.132.

Which Criterion Is More Reliable for Selecting the Distal Fusion Level in Cases of Adolescent Idiopathic Scoliosis with Structural Thoracolumbar/Lumbar Curves: Static or Dynamic?

• Cho JH
• Hwang CJ
• Park JW
• Lee DH
• Lee CS

• KMID: 2467942
• DOI: http://doi.org/10.4184/jkss.2019.26.4.132

Abstract

STUDY DESIGN: Retrospective comparative study.
OBJECTIVES
To compare the reliability of 2 criteria to predict the radiological outcomes of corrective surgery in cases of adolescent idiopathic scoliosis (AIS) with structural thoracolumbar/lumbar (TL/L) curves. SUMMARY OF LITERATURE REVIEW: Distal fusion level selection in AIS with structural TL/L curves is debatable.
MATERIALS AND METHODS
This study included 131 AIS patients with structural TL/L curves who underwent corrective surgery in which distal fusion was stopped at L3. Whole-spine standing radiographs and bending radiographs were obtained preoperatively. The patients were divided into 2 groups according to their findings on bending radiographs (dynamic criterion) and by the last touching vertebra and the lower end vertebra (static criterion). Radiological outcomes were assessed by reviewing postoperative radiographs. Reliability tests were conducted to compare the predictability of radiological outcomes using these 2 methods. In addition, radiological parameters were compared between both criteria.
RESULTS
Among 131 patients, 25 showed radiologically poor outcomes (19.1%). The sensitivity of the dynamic and static criteria was 0.69 and 0.50, respectively. The specificity of each criterion was 0.49 and 0.64, respectively. Overall, the dynamic criterion showed superior reliability (p=0.03). However, no significant difference in radiological parameters could be found in a comparison of both criteria.
CONCLUSIONS
Although the dynamic criterion was more sensitive for predicting poor radiological outcomes when stopping fusion at L3 in patients with structural TL/L curves, its specificity was lower than that of the static criterion. Thus, both dynamic and static criteria should be considered when selecting the distal fusion level in cases of AIS with structural TL/L curves.

Keyword

Adolescent idiopathic scoliosis; Double major curve; Distal fusion level; Lower instrumented vertebra

MeSH Terms

Adolescent*
Humans
Retrospective Studies
Scoliosis*
Sensitivity and Specificity
Spine

Figure

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  Fig. 1. Radiological measurements. (A) A preoperative radiograph showing the Cobb angle, LEV, LTV, AVT, and trunk shift (C7-CSVL distance) (B) A postoperative radiograph showing the L3-L4 disc wedge angle and the LIV+1 tilt. LEV, lower end vertebra; LTV, last touching vertebra; AVT, apical vertebral translation; CSVL, central sacral vertical line; LIV, lowest instrumented vertebra.

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  Fig. 2. A receiver operating characteristic curve comparing the reliability of the dynamic and static criteria.

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  Fig. 3. (A, B) A preoperative radiograph of a 13-year-old female patient with a Lenke 6C curve. Good and poor outcomes were expected according to the static and dynamic criteria, respectively (LEV=L3, LTV=L4, rotation grade II, CSVL did not cross the vertebral body of L3). (C) A good radiological outcome was observed at a postoperative 2-year follow-up, even though a poor outcome was expected according to the dynamic criterion. LEV: lower end vertebra, LTV: last touching vertebra, CSVL: central sacral vertical line.

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  Fig. 4. (A, B) A preoperative radiograph of a 19-year-old female patient with a Lenke 3C curve. Good and poor outcomes were expected according to the dynamic and static criteria, respectively (LEV=L4, LTV=L5, rotation grade I, CSVL crossed the vertebral body of L3). (C) A poor radiological outcome was observed at a postoperative 2-year follow-up, even though a good outcome was expected according to the dynamic criterion. LEV: lower end vertebra, LTV: last touching vertebra, CSVL: central sacral vertical line.

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