Figure. Smoothed Restricted Cubic Spline Plot of the Adjusted Log Odds Ratio of Experiencing Any Complication vs the Annual Number of Minimally Invasive Pancreaticoduodenectomy Cases Performed per Hospital.

The curved line with long dashes represents the regression line in the change point estimation. The 2 lighter dotted curves represent the 95% CIs. The black dots correspond to the location of 3 knots used in the model. The intersection at the value of 22 cases per year (dotted blue vertical line) is the cutoff identified by the model, with adjustment for the effects of patient age, sex, race/ethnicity, comorbidities, year of diagnosis, and clinical diagnosis.