Learning Curve for Thoracoscopic Repair of Congenital Diaphragmatic Hernia Using Cumulative Sum Analysis

Purpose: Thoracoscopic repair of congenital diaphragmatic hernia (CDH) is technically challenging and requires various surgical strategies. However, studies investigating the learning curve of thoracoscopic repair of CDH are rare. The objective of this study was to determine whether there is a learning curve of thoracoscopic repair of CDH and analyze its pattern by cumulative sum (CUSUM) analysis. Methods: From 2008, when the first case was performed, to 2020, children diagnosed with Bochdalek-type CDH who underwent thoracoscopic repair were included. Learning curves of 2 operators were analyzed individually using the CUSUM method which is the running total of differences between operation time of each case and the mean operation time. We divided the CUSUM curve into three phases based on its slope and performed interphase analysis of patients’ baseline characteristics and surgical outcomes. Results: A total of 111 children (operator A, n=88; operator B, n=23) underwent thoracoscopic repair of CDH during the study period. CUSUM curve of operator A showed an ascending curve from the first case to the 33rd case, then a plateau between the 34th case and the 55th case, and a descending form from the 56th case. In interphase comparisons of surgical outcome of operator A, recurrence rate and rate of complication did not show statistically significant differences. The learning curve of operator B showed a flat overall appearance and plateaued after the 14th case. Conclusion: Surgical experience based on 33 cases was needed to reach the learning curve to perform thoracoscopic repair of CDH. For a new surgeon experienced with assisting a skilled operator, a relatively high proficiency was obtained from the start with a shorter learning curve. Interphase analysis of surgical outcome suggests that thoracoscopic repair of CDH can be performed without compromising patients’ safety even before reaching the learning curve.