Cobb angle measurement of scoliosis using computer measurement of digitally acquired radiographs-intraobserver and interobserver variability.

Abstract

We evaluated computer assisted digital measurement of radiographic parameters in patients with idiopathic scoliosis. To assess the reliability of digital measurements. Various authors analyzed scoliotic deformities by conventional radiographs, but very few studies have addressed the reliability of digital radiographic measurement using computer software. Three independent, blinded observers measured 318 whole spine pre-operative antero-posterior radiograms of children with varying degrees of idiopathic scoliosis. Only one curve per radiograph was measured. Each observer measured the Cobb angle three times with a 1-week gap between each measurement. The computer system, picture archiving and communication system (PACS, PiViewSTAR version 5) was used in all cases. The end vertebrae were pre-selected to avoid this as a potential source of error. The results were statistically analyzed for intraobserver and interobserver reliability and variability. The 95% confidence intervals for intraobserver and interobserver variability were +/-1.30 and +/-1.260, respectively. There was better reliability in larger curves. Measurement using a digitized system may help to minimize measurement discrepancies by eliminating an intrinsic cause of error.