Assessing the learning curve in robot-assisted intracorporeal colorectal anastomosis and transrectal extraction (NICE) procedure: from Initial Learning to Mastery

Abstract

The robotic NICE procedure is a novel minimally invasive approach in colorectal surgery, yet its learning curve remains undefined; this study aimed to define its distinct phases by analyzing operative time trends. A retrospective review of 170 consecutive NICE procedures performed by a single surgeon between May 2018 and August 2019 was undertaken. Skin-to-skin operative time was the learning curve surrogate and plotted with unadjusted and risk-adjusted cumulative sum (CUSUM) analyses. Risk adjustment incorporated age, body mass index, ASA class, sex, prior abdominal surgery, diagnosis, anastomotic level, and the need for diverting loop ileostomy-used as a marker of case complexity rather than a direct time determinant. Phase-specific peri-operative outcomes were compared non-parametrically. Five proficiency phases were identified: Initial Learning (cases 1-10), Experienced (11-65), Second Learning (66-80), Advanced Experienced (81-124) and Mastery (125-170). The unadjusted CUSUM rose to + 342 min above the cohort mean by case 10, crossed the baseline at case 55, then gradually declined and plateaued at approximately -215 min by case 170. Risk-adjusted CUSUM displayed parallel inflection points (peak + 78 min, nadir -162 min), confirming that an easier case mix did not explain efficiency gains. Mean operative time fell from 248.8 ± 64.1 min in the first phase to approximately 185 min in Mastery, and inter-quartile variability narrowed from 125 to 59 min. Intraoperative complications (overall 12.4%), blood loss, organ/space surgical site infection, and 30-day morbidity did not differ across phases (p > 0.05). The robotic NICE procedure follows a five-phase learning curve, with true proficiency-and a 20% reduction in operative time-achieved after ~ 55 cases. Safety metrics remained similar across phases, confirming that efficiency gains reflect skill acquisition rather than easier case mix. These milestones can guide training for surgeons adopting the technique.

Keywords: Colorectal surgery; Learning curve; Natural orifice intracorporeal anastomosis; Robotic surgery; Transrectal extraction.