A Comparison of Manual Versus Computer-Assisted Radiographic Measurement

Abstract

The results of this study demonstrate that intraobserver variability for manual and computer Cobb angle measurements yield a 95% confidence interval of approximately 3 degrees, with the computer having a slightly lower variability. The computer technique removes sources of intrinsic error, e.g., the variability introduced by using different manual protractors, the inaccuracy of standard protractors, and the use of wide-diameter radiographic markers. Identical digital images can be shared electronically between centers, without having to duplicate and mail films. Multicenter studies in which different examiners will be measuring Cobb angles may consider using the computer as a measuring device to reduce intrinsic measurement errors.

Inter- and intraobserver reliability assessment of the Cobb angle: manual versus digital measurement tools

“…These data suggest that the use of digital measurements does not improve measurement accuracy of the Cobb angle. These findings are in contrast to those reported by Shea et al [11], who found a statistically better correlation in digital, compared to manual measurement of curves. However the intra-and interobserver reliability results of this study are comparable with those from previous studies [2,6,8] (Table 4).…”

“…Important parts of the spine can be enlarged and seen more clearly by changing the contrast, and the borders of the vertebrae can be enhanced by computerized options. After drawing lines through the endplates of end vertebrae the software measures the angle automatically, which may reduce sources of error [11].…”

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].…”

“…Documented coronal plane deformity progression in scoliosis as reflected by Cobb angle progression beyond defined thresholds directs treatment. Cobb angle is usually measured from erect radiographs and measurement variability associated with this technique has been reported for manual measurement of plain radiographs [6,10,11,14] and computer-based measurement of digitized radiographs [5,8,18]. Reduction of digitized image output size could impact image quality.…”