The reliability of quantitative analysis on digital images of the scoliotic spine

Abstract

Although analysis of scoliotic deformity is still studied extensively by means of conventional roentgenograms, computer-assisted digital analysis may allow a faster, more accurate and more complete evaluation of the scoliotic spine. In this study, a new computer-assisted measurement method was evaluated. This method uses digital reconstruction images for quantitative analysis of the scoliotic spine. The aim of the current study was to determine the reliability of the computer-assisted measuring method, which was done by establishing coefficients of repeatability for a variety of measurements. Measurements were carried out by five observers on 30 frontal and 10 lateral scoliotic digital reconstruction images. Each image was measured on three separate occasions by placing anatomical vertebral landmarks and drawing lines with a computer pointing device. The computer then calculated a number of geometrical shape parameters from scale calibration, landmarks and lines. The intra- and interobserver results were subjected to an analysis of variance to assess the level of agreement, and the means and standard deviations were calculated. The coefficient of repeatability (CR) was taken to be equal to two standard deviations. The mean intraobserver CR was found to be 3.1 degrees for the Cobb angle on the frontal digital image and 3.3 degrees for the kyphosis Cobb angle on the lateral overview. The mean difference in the intraobserver CR of the Cobb angle between measurements made by placing landmarks and those made by drawing lines was not statistically significant (P>0.05). The mean intraobserver CR for the other parameters can be summarized as follows: for lateral deviation it was 0.8 mm, for axial rotation 4.0 degrees and for length of the spine 3.3 mm. The interobserver bias was negligible. It can be concluded that the reliability of our new method for quantifying geometrical variables on digital reconstruction images is better than measurements on conventional roentgenograms in previously published reports. The presented method is therefore considered to be more accurate for research of spinal deformities and more adequate for clinical management of scoliosis.

Reliability analysis for manual measurement of coronal plane deformity in adolescent scoliosis. Are 30 × 90 cm plain films better than digitized small films?

“…First, the mean angular difference was 2.81°±2.61°. The reproducibility of the Cobb angle measures obtained here appears equal to or better than previously reported for intra-observer or inter-observer studies using manual or computer-assisted techniques [4,5,15,17,18,20]. However, direct comparisons cannot be made with the previously mentioned studies because different radiographs were evaluated and differing statistical methods used in those studies.…”

“…Studies of inter-observer and intra-observer variability in measurement of this angle [3,7,9,15,16,20] have revealed that errors in radiographic measurements are typically ±5°and are comparable with thresholds of change that can influence treatment decisions [19]. Recent studies [4,5,8,14,18] demonstrate computer-assisted methods to reduce technical errors and the need for memorization of measurement and classification procedures. However, the manual technique is routinely used in many surgical teams because of its simplicity and cost [10,11].…”

Measuring procedures to determine the Cobb angle in idiopathic scoliosis: a systematic review

“…Tanure et al [9] identified no statistically [11] demonstrated that, using the two landmarks procedure, the Cobb angle is 0.3°greater than using the six landmarks digital procedure (p \ 0.05).…”

“…This may lead to selection, reviewer and information bias and bias the assessment of test characteristics. Three studies [11,12,14] with a high risk of bias were included.…”

“…Aside from the manual procedure, there are so-called digital computer-assisted (semi-automatic) [6][7][8][9][10][11][12], automatic [13,14] and smartphone app procedures [15,16].…”