The Influence of Posture on Instability Evaluation Using Flexion–Extension X-Ray Imaging in Lumbar Spondylolisthesis

Asian Spine Journal 308 DaisukeClinical Inoue et Study al. Asian Spine J 2021;15(3):308-316 •Asian https://doi.org/10.31616/asj.2020.0124 Spine J 2021;15(3):308-316 The Influence of Posture on Instability Evaluation Using Flexion–Extension X-Ray Imaging in Lumbar Spondylolisthesis Daisuke Inoue1, Hideki Shigematsu2, Yoshiyuki Nakagawa3, Toshichika Takeshima3, Yasuhito Tanaka2 1 Department of Orthopaedics, Higashiosaka City Medical Center, Higashiosaka, Japan Department of Orthopedic Surgery, Nara Medical University Hospital, Kashihara, Japan 3 Department of Orthopedics, Uda City Hospital, Uda, Japan 2 Study Design: Prospective clinical study. Purpose: To determine the optimal posture for instability evaluation using flexion–extension X-ray imaging in patients with lumbar spondylolisthesis. Overview of Literature: Currently, flexion–extension X-ray imaging is the most practical approach for the evaluation of lumbar instability. In flexion–extension X-ray imaging, achievement of the greatest segmental motion with flexion–extension movement is necessary. However, to our knowledge, currently, there is no standardized posture for determining lumbar instability. Methods: Twenty-three individuals with lumbar spondylosis related to the fourth vertebra underwent flexion–extension X-ray imaging in different postures (standing, sitting, and lateral decubitus positions), lumbar magnetic resonance imaging (MRI), and low back pain Visual Analog Scale (VAS) evaluation on the same day. Intervertebral angle, percent slippage, and intervertebral disc area ratio for different postures during flexion and extension were compared using Tukey’s method. The effect of low back pain and the association between MRI facet effusion and these measurements were investigated according to posture. Results: The percent slippage during extension (p =0.036), change in the percent slippage between flexion and extension (p =0.004), and change in the intervertebral angle (p =0.042) were significantly different between the sitting and lateral decubitus positions. There were also significant differences between the standing and lateral decubitus positions in the change in intervertebral angle (p =0.010). In patients with VAS score <40, there were significant differences in the intervertebral angle (p =0.011) between the standing and lateral decubitus positions, percent slippage (p =0.048), and intervertebral disk ratio (p =0.008) between the sitting and lateral decubitus positions. We found no relationship between MRI facet effusion and posture in terms of instability. Conclusions: In this study, intervertebral instability was best evaluated in the lateral decubitus position when using flexion–extension X-ray imaging for patients with fourth lumbar vertebral spondylolisthesis. Keywords: Lumbar; Spondylolisthesis; Flexion–extension X-ray; Magnetic resonance imaging; Visual Analog Scale Received Mar 25, 2020; Revised Apr 29, 2020; Accepted May 2, 2020 Corresponding author: Hideki Shigematsu Department of Orthopedic Surgery, Nara Medical University Hospital, 840 Shijocho, Kashihara city, Nara, Japan Tel: +81-744-22-3051, Fax: +81-744-25-6449, E-mail: ASJ Copyright Ⓒ 2021 by Korean Society of Spine Surgery 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. Asian Spine Journal • pISSN 1976-1902 eISSN 1976-7846 • www.asianspinejournal.org Asian Spine Journal Introduction Lumbar instability is an important cause of low back pain (LBP) [1]; however, the optimal method to evaluate lumbar instability remain controversial [2,3]. Various methods, such as simple radiography, computed tomography (CT), and magnetic resonance imaging (MRI), have been used to diagnose lumbar instability [4]. During CT and MRI scanning, patients are typically placed in the supine position; however, the narrow space in these devices hampers the functional imaging of the spine [5]. Thus, flexion–extension radiography is currently the most practical approach for the evaluation of lumbar instability. The use of flexion–extension radiography was first reported by Knutsson [6] in 1944. In this type of imaging, it is necessary to obtain the greatest segmental motion with flexion–extension movement that is improved in the sitting or standing position [6-8]. Wiltse and Hutchinson [8] and Nishimura et al. [5] stated that the functional imaging of the spine should be performed with the patient in the standing position while imaging in the frontal and side views and considering the natural physiological curvature. In contrast, flexion–extension radiography has been frequently used in the lateral decubitus position [9]. Shigematsu et al. [10] compared the instability determined using flexion–extension radiography between the standing and lateral decubitus positions in patients with fourth lumbar vertebral spondylosis and found that the intervertebral angle during flexion was significantly decreased in the lateral decubitus position. However, they only investigated few cases, the definition of imaging was ambiguous in their study, and pain during imaging was not considered. Moreover, Nishimura et al. [5] reported that in lumbar spine functional imaging, the lateral decubitus position during flexion and the standing and lateral decubitus positions during extension were optimal. Nevertheless, their study involved healthy individuals rather than patients with unstable lumbar spondylosis. Recently, it has been reported that “facet effusion” in lumbar MRI correlates with lumbar instability [11]; however, the correlation between this feature and flexion– extension radiography-based instability measurements remains unclear. In this study, we investigated whether posture (standing, sitting, and lateral decubitus positions) during flexionextension radiography affects the instability assessment; whether LBP affects instability assessment on flexion– Instability in Lumbar Spondylolisthesis 309 extension X-ray imaging, and whether facet effusion on MRI correlates with flexion–extension radiography findings. Materials and Methods 1. Participants This study was approved by the appropriate institutional ethics committee in Uda City Hospital (approval no., 001) and conducted as per the principles of the Helsinki Declaration. Informed consent was obtained from each participant. We enrolled spondylolisthesis patients who visited the orthopedic outpatient department of Uda City Hospital with the main complaint of LBP or lower extremity pain between April 2016 and June 2017. Male and female patients with mild scoliosis or spondylolisthesis were included. Age was not considered for study inclusion. The exclusion criteria were as follows: a history of lumbar surgery, trauma involving spinal vertebral fractures, sl (...truncated)