Content area
Full Text
Eur Spine J (2014) 23:27432750 DOI 10.1007/s00586-013-3134-5
ORIGINAL ARTICLE
Hilus pulmonis as the center of gravity for AS thoracolumbar kyphosis
Kai Song Guoquan Zheng Yonggang Zhang
Geng Cui Xuesong Zhang Keya Mao Yan Wang
Received: 25 August 2012 / Revised: 11 December 2013 / Accepted: 12 December 2013 / Published online: 31 December 2013 Springer-Verlag Berlin Heidelberg 2013
AbstractIntroduction 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-xed 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 coefcient (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 signicant (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...