Correlation coefficients between the effect of the main curve correction and some relevant factors Factors Correlation coefficient r (spearman) p Age - 0.434 0.005 Main curvature angle before surgery - 0.204 0.206 Iliac crest ossification - 0.187 0.248 Rotation value of peduncle Nash - Moe - 0.132 0.418 Number of screw 0.197 0.222 18 Figure 3.1.