Interobserver and intraobserver reliability of determining the deformity angular ratio in severe pediatric deformity curves.

The mean C-DAR was 14.9 (range 1.3-51.5) with a mean Cobb angle of 88.8° (range 15.0-163.0) over a mean of 7.5 (range 2.0-14.0) levels. The mean S-DAR was 8.6 (range 1.0-19.6), with a mean Cobb angle of 68.0° (range 10.0-137.0) over a mean of 7.5 (range 3-11) levels. The intraobserver reliability of the C-DAR was ICC = 0.908 (range 0.846-0.960) and the S-DAR 0.914 (range 0.815-0.961). The interobserver reliability of the C-DAR was ICC = 0.868 (range 0.846-0.938), and the S-DAR was ICC = 0.848 (range 0.815-0.961). Despite poor reliability among UEV, LEV, and apex selection (aggregated range 0.340-0.724), the C-DAR and S-DAR were demonstrated to be reliable in our study CONCLUSIONS: Reliability was good to excellent for C-DAR and S-DAR, despite poor to moderate reliability among UEV, LEV, and apex selection. These data support the use of the C-DAR, S-DAR, and combined T-DAR as a means of quantifying deformity magnitude.