Evaluation of Mis-Selection of End Vertebrae and Its Effect on Measuring Cobb Angle and Curve Length in Adolescent Idiopathic Scoliosis

Abstract

Background: The Cobb angle is critical in assessing adolescent idiopathic scoliosis (AIS) patients. This study aimed to evaluate the error in selecting the upper- and lower-end vertebrae on AIS digital X-rays by experienced and novice observers and its correlation with the error in measuring the Cobb angle and determining the length of the scoliotic curves. Methods: Using the TraumaMeter v.873 software, eight raters independently evaluated 68 scoliotic curves. Results: The error percentage in the upper-end vertebra selection was higher than for the lower-end vertebra (44.7%, CI95% 41.05–48.3 compared to 35%, CI95% 29.7–40.4). The mean bias error (MBE) was 0.45 (CI95% 0.38–0.52) for the upper-end vertebra and 0.35 (CI% 0.69–0.91) for the lower-end vertebra. The percentage of errors in the choice of the end vertebrae was lower for the experienced than for the novices. There was a positive correlation (r = 0.673, p = 0.000) between the error in selecting the end vertebrae and determining the length of the scoliotic curves. Conclusions: We can conclude that errors in selecting end vertebrae are common among experienced and novice observers, with a greater error frequency for the upper-end vertebrae. Contrary to the consensus, the accuracy of determining the length of the scoliotic curve is limited by the Cobb method’s reliance on the correct selection of the end vertebrae.

Keywords

• adolescent idiopathic scoliosis
• Cobb angle
• measurement errors
• radiographic assessment
• spine curvature