Fig. 4

Calibration curves of the nomogram model in the training cohort (A) and validation cohort (B). Nomogram-predicted probability of SSI is plotted on the x-axis; actual probability of SSI is plotted on the y-axis. The diagonal dotted line represents the perfect prediction of the ideal model. The solid line represents the performance of the nomogram. The closer the fitting is to the diagonal dashed line, the more accurate the prediction is