Evaluation of the learning curve for laparoscopic liver resection by risk-adjusted CUSUM analysis using the Iwate difficulty index

Abstract

Background: Laparoscopic liver resection (LLR) is technically challenging and requires training in both hepatobiliary and advanced laparoscopic techniques. The aim of this study was to compare the learning curve of LLR using CUSUM (cumulative sum control chart) analysis before and after risk adjusting for operative difficulty using the Iwate difficulty index. Methods: Retrospective analysis of a prospective database of consecutive patients who underwent LLR by two surgeons at a single centre between January 2011 and June 2016. The learning curve for LLR for both surgeons was evaluated using CUSUM analysis before and after risk-adjusting for operative difficulty using the Iwate difficulty index. Results: 125 consecutive patients underwent LLR during the study period, including non-anatomical resection (57), left lateral sectionectomy (42) and major hepatectomy (26). Conversion to open surgery was necessary in 14 patients (11%). The first major resection was jointly performed by surgeon A and B after 38 minor resections (surgeon A – 15; surgeon B – 23). Unadjusted CUSUM analysis of operating time identified a learning curve of 50-60 procedures. After risk-adjusting for operative difficulty, the shape of the CUSUM plot changed and the learning curve reduced to 25-30 procedures. Conclusion: Risk-adjustment using the Iwate difficulty index may enhance the applicability of CUSUM analysis in the assessment of learning curve of laparoscopic liver resection, and warrants further study.