Cobb Angle Measurement of Scoliosis Using Computer Measurement of Digitally Acquired Radiographs-Intraobserver and Interobserver Variability

Study Design: We evaluated computer assisted digital measurement of radiographic parameters in patients with idiopathic scoliosis. Purpose: To assess the reliability of digital measurements. Overview of Literatures: Various authors analyzed scoliotic deformities by conventional radiographs, but very few studies have addressed the reliability of digital radiographic measurement using computer software. Methods: 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. Results: The 95% confidence intervals for intraobserver and interobserver variability were +/- 1.30 and +/- 1.260, respectively. There was better reliability in larger curves. Conclusions: Measurement using a digitized system may help to minimize measurement discrepancies by eliminating an intrinsic cause of error.