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European Spine Journal

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01-12-2014 | Original Article

Hilus pulmonis as the center of gravity for AS thoracolumbar kyphosis

Authors: Kai Song, Guoquan Zheng, Yonggang Zhang, Geng Cui, Xuesong Zhang, Keya Mao, Yan Wang

Published in: European Spine Journal | Issue 12/2014

Abstract

Introduction

The sagittal vertical axis (SVA) is a meaningful measurement and widely used for evaluating sagittal balance, and is considered a design standard for surgery, including most ankylosing spondylitis (AS) kyphotic deformity planning. However, recent research indicates that the C7 plumb line is actually not the center of gravity (CG) line. Therefore, whether there is a better radiological marker as the CG of the trunk for AS thoracolumbar kyphosis remains unknown. This research is to investigate a radiological marker for the CG of the trunk in lateral radiographs for AS thoracolumbar kyphosis.

Materials and methods

The center of gravity of an irregular object can be obtained by hanging or supporting it in different points and directions, and the CG will be on the point of intersection. According to this principle of mechanics, we could use the pre- and post-operative hip axis vertical lines to locate the CG of the trunk. We evaluated 38 AS-fixed thoracolumbar kyphotic patients with pedicle subtraction osteotomies. Full-length, free-standing lateral radiographs, including the spine and pelvis, were available for all patients. Pre- and post-operative radiological parameters were measured, including SVA, horizontal distance between hip axis and C7 (HDHC), horizontal distance between hip axis and T5 (HDHT5), horizontal distance between hip axis and T9 (HDHT9), and horizontal distance between hip axis and hilus pulmonis (HDHH). Pre- and post-operative radiological parameter changes were compared by paired samples t tests. The intraclass correlation coefficient (ICC) was used to determine the intra- and interobserver reliabilities of HDHH.

Results

Pre-operative SVA, HDHC, HDHT5, HDHT9, and HDHH values were, respectively, 21.1, 12.7, 3.5, −3.8, and 2.7 cm, and their post-operative values were, respectively, 9.1, 4.2, −2.1, −5.6, and 0.9 cm. Changes in SVA, HDHC, HDHT5, and HDHT9 were significant (p < 0.05), while the change in HDHH was not (p > 0.05). The ICC for overall interobserver reliability was 0.958 (p < 0.001), and it was 0.963 (p < 0.001) for overall intraobserver reliability.

Conclusion

The hilus pulmonis fell approximately on the hip axis both pre- and post-operatively. It was a better marker as the center of gravity of the trunk for deformity planning for AS thoracolumbar kyphosis.

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Title: Hilus pulmonis as the center of gravity for AS thoracolumbar kyphosis
Authors: Kai Song
Guoquan Zheng
Yonggang Zhang
Geng Cui
Xuesong Zhang
Keya Mao
Yan Wang
Publication date: 01-12-2014
Publisher: Springer Berlin Heidelberg
Published in: European Spine Journal / Issue 12/2014
Print ISSN: 0940-6719
Electronic ISSN: 1432-0932
DOI: https://doi.org/10.1007/s00586-013-3134-5

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Springer Medicine

Hilus pulmonis as the center of gravity for AS thoracolumbar kyphosis

Abstract

Introduction

Materials and methods

Results

Conclusion

At a glance: The ONWARDS insulin icodec trials

Springer Medicine

Abstract

Introduction

Materials and methods

Results

Conclusion

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