Risk factors for vertebral bridging in residual adolescent idiopathic scoliosis with thoracolumbar/lumbar curves

Elsevier

Available online 1 December 2022

Journal of Orthopaedic ScienceAuthor links open overlay panelAbstractBackground

Although vertebral bridging in residual adolescent idiopathic scoliosis (AIS) can make corrective surgery more complicated, no study has investigated the risk factors. The purpose of this research was to determine risk factors for vertebral bridging in individuals with residual AIS with thoracolumbar/lumbar (TL/L) curves.

Methods

Forty-two pre-operative patients with residual AIS and TL/L curves (3 males, 39 females: age 41.9 ± 18.0 years) were divided into bridging (n = 17) and non-bridging (n = 25) groups. All patients were 20 years or older with a diagnosis of AIS in adolescence. The bridging group consisted of patients with third or more degree bridging by the Nathan classification.

Results

There were significant differences in age, absolute value of apical vertebral translation (AVT), C7 translation, and L3,4 tilt between groups. There was no significant difference in TL/L Cobb angle. Multivariate analyses and ROC curves demonstrated that older age was a significant risk factor for vertebral bridging (odds ratio [OR]: 1.08; 95% confidence interval: 1.02–1.14; P = 0.004), with a cutoff value of 38.0 years old.

Conclusions

This study indicates that patients >38 years old are at risk for vertebral bridging in residual AIS. Because of the higher risk of vertebral bridging and other degenerative changes, residual AIS patients about 40 years of age are at a critical point for treatment strategy. Because appropriate surgical time should not be missed, regular follow-up is required even after 30 years of age, especially if the patient with residual AIS has a large TL/L curve indicated for surgery.

Introduction

Vertebral bridging is prevalent in preoperative residual adolescent idiopathic scoliosis (AIS) patients in middle and old age who have a thoracolumbar/lumbar (TL/L) curve. On the other hand, vertebral bridging is uncommon in teenagers with AIS. Bridging decreases spinal flexibility [1], which leads to more surgical invasion than in individuals who undergo surgery as adolescents. Thorough bony release or more extensive surgery may be required to achieve mobility in these patients [2,3]. Greater surgical invasiveness may lead to more surgical complications and a lower postoperative quality of life than in younger patients [4]. Therefore, corrective surgery before bridging occurs is desirable.

With increasing age and curvature [5,6], vertebral bridging is expected to occur. At some point between adolescence and middle age, there must be a threshold of curvature at which bridging occurs. However, no study has determined the age or Cobb angle at which bridging is most likely to occur. Clarifying this point will help surgeons to choose the best surgical timing for individuals with residual AIS.

The purpose of this study was to determine risk factors for vertebral bridging in individuals with residual AIS with TL/L curves. We also aimed to determine the age and degree of scoliosis at which vertebral bridging is most frequent. We hypothesized that the Cobb angle of the lumbar scoliosis curve is a risk factor for vertebral bridging.

Section snippetsMaterial and methods

Approval for this study was obtained from our institutional review board. Informed consent was obtained from all patients for publication. No identifiable information of the patients was included in the manuscript. Data for consecutive preoperative AIS patients with TL/L curves in our hospital between June 2011 and January 2020 were collected from their medical records. To evaluate vertebral bridging accurately, computed tomography (CT) was necessary. Therefore, this study included only

Results

There were no significant differences between the bridging and non-bridging groups in sex ratio, curve type according to the Lenke classification, the Cobb angle of MT and TL/L curves, the location of apex of TL/L curve, or the convexity of TL/L curve. In contrast, there were significant differences in age, LL, TLK, the absolute value of AVT and C7 translation, AVR, numbers of slipped vertebrae, shift of L2, L3, and L4, tilting angle of L3 and 4, and VAS of preoperative leg and back pain.

Discussion

Age and the absolute value of AVT are risk factors for vertebral bridging. Although it is evident that older patients have vertebral bridging more frequently, no study has determined when it occurs. The finding that vertebral bridging is likely to occur shortly before age 40 is significant. Furthermore, we found that following vertebral bridging, LIV was more often at L5 or sacral, operative time was longer, and the correction rate of the Cobb angle was worse.

We hypothesized that the Cobb angle

Ethical statement

IRB approval (2020009). No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Declaration of Competing Interest

The authors declare no conflicts of interest associated with this manuscript.

Acknowledgments

The authors would like to express deepest gratitude for Ms. Yuri Ichikawa and Ms. Nana Kondo for assisting with the data collection.

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© 2022 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.

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