Study design: Observational study with three examiners.
Objective: To compare the reliability of the Cobb and centroid methods.
Summary of background data: The Cobb method is considered to be the gold standard in scoliosis measurement despite its low reliability. In adolescent idiopathic scoliosis (AIS) patients, the centroid method can be a good method for measuring scoliosis.
Methods: Sixty whole spine postero-anterior radiographs were collected to compare the reliability of the Cobb and centroid methods in AIS patients. Sixty radiographs were measured twice by each of the three examiners using the two measurement methods. The data were analyzed statistically to determine the inter- and intraobserver reliability.
Result: In comparisons of inter- and intraobserver reliability of all 60 radiographs, the inter- and intraclass coefficients (ICCs) were higher in the centroid (>0.969) than in the Cobb method (>0.832), although both were in the excellent range. The mean absolute difference (MAD) values were higher in the Cobb method (<7.15° vs. <3.75°), and >5° in five comparisons. Regarding measures of mismatched radiograms, the inter- and intraobserver MAD values were higher in the Cobb method (<9.81° vs. <3.82°), and >5° in six comparisons. And, the ICCs were higher in the centroid method (>0.972) than the Cobb method (>0.758). In immature radiograms, the ICCs were higher in the centroid (>0.973) than in the Cobb method (>0.764), even though it was in the excellent range. And, the inter- and intraobserver MAD values were higher in the Cobb method (<8.49° vs. <3.99°), and >5° in seven comparisons.
Conclusion: The centroid method is more reliable for measuring scoliosis in AIS than the Cobb method, and it can substitute the Cobb method, which showed high variability.