A new method to measure vertebral rotation from CT scans

Abstract

IntroductionThe importance of vertebral rotation in the etiology and management of scoliosis is well recognized. Evaluation of transverse plane deformity in idiopathic scoliosis is still controversial.Displacement of the spinous process from the midline was used to measure rotation by Cobb [16]. Later, Nash and Moe introduced their own method, in which the displacement of the convex-side pedicle toward the midline was considered to be in direct proportion to the degree of rotation [13]. Perdriolle quantitatively measured pedicle shift using a specific template [14]. Some authors have also described analytic methods based on trigonometric and geometric measurements on plain radiographs [4,5,16,18].Because of the high rate of error, application difficulties and performer variation of these conventional radiography measurement methods, authors have looked for more sensitive methods [3]. The use of CT to measure vertebral rotation was introduced by Aaro and Dahlborn in 1981, in a study of five patients [1]. Subsequently, they used the method to assess rotational deformity of spine and rib cage and the derotation effect of the Boston brace, and to study the relation between lateral curvature and rotation of the apical vertebra [2]. Recently, Ecker et al. used the CT method to evaluate the effect of CotrelDubousset instrumentation in idiopathic scoliosis [6]. In this method, the sagittal angle (RA sag) was taken to be the angle between the sagittal plane and the line between the correct posterior mid-point of the vertebral canal and the center point of the corpus vertebrae.A second method was described by Ho et al. in 1993 [9]. The vertebral rotation angle was taken to be the angle between the sagittal plane and mid-angle line of connecting lines of three points. These three reference points Abstract CT measurement methods have good reliability for idiopathic scoliosis transverse plane deformity evaluation. However, because of application difficulties and variations in how these methods are applied, more sensitive methods are needed. This paper presents a new method for measurement of vertebral rotation from tomographic scans. First, the method was subject to clinical, intraobserver and inter-observer analysis. Twenty-three patients with adolescent idiopathic scoliosis were studied to test the clinical reliability of this method. There were no statistical differences between the results of the new method and Ho's method (P = 0.3380) in the clinical study. Intraobserver and inter-observer analysis showed that this method was reliable. An experimental study was then conducted to show the confidence limits of our new method, which were found to be ± 1.6°, and there was no significant difference between the mean rotation value obtained from CT scans using our new method and that obtained using the mechanical method. These results suggest that our new method is a simple, practical and reliable method for measurement of vertebral rotation from CT scans.

Determination of axial vertebral rotation in MR images: comparison of four manual and a computerized method

“…The manual methods of Aaro and Dahlborn [1], Ho et al [11], Krismer et al [13] and Göçen et al [9] (Fig. 1) were used to measure the AVR in 3D MR images.…”

“…On the other hand, the obtained results were not in accordance with the study of Göçen et al [8], where the method of Ho et al proved to be among the methods with the highest intra-and inter-observer reliability. However, all of the existing comparison studies [2,8,9] were performed on CT spine images (Table 3).…”

“…To the best of our knowledge, the intra-and inter-observer reliabilities of manual and/or computerized methods for measuring AVR in images acquired by magnetic resonance (MR) imaging have not been investigated yet. This study therefore aims to analyze the AVR values obtained by four manual [1,9,11,13] and a computerized method [20], obtained from MR images of normal and scoliotic vertebrae.…”

Validity and reliability of a computer method to estimate vertebral axial rotation from digital radiographs

“…Some advantages over conventional procedures are the shorter exposure of patients to radiation [10], variable contrast scales, efficient image transfers and comparisons and easy storage. Such advantages have encouraged some researchers [11,12] to develop new computer-based methods to assess vertebral axial rotation.…”

A Symmetry-Based Method for the Determination of Vertebral Rotation in 3D

“…In the past, many methods for quantitative assessment of vertebral rotation were developed for two-dimensional (2D) X-ray images, while the measurements in three dimensions (3D) became possible with the development of 3D imaging techniques. Earlier methods were based on identifying a number of distinctive anatomical landmarks on vertebrae in both computed tomography (CT) and magnetic resonance (MR) axial cross-sections [1,2,3,4]. Recently, methods based on image analysis techniques have been proposed for measuring vertebral rotation in 3D.…”