CUSUM Analysis of the Initial Learning Curve for Robot-Assisted Gynecologic Surgery at a German Tertiary Center

Abstract Abstract Objective: To evaluate the initial learning curve of robot-assisted laparoscopic hysterectomy performed by a single surgeon during the implementation of robotic gynecologic surgery at a German tertiary university center using cumulative sum (CUSUM) analysis. Methods: This retrospective observational study included the first 66 consecutive patients who underwent robot-assisted laparoscopic hysterectomy using the da Vinci X surgical system between January 2022 and September 2023 at the University Hospital Frankfurt. Operative performance was assessed using CUSUM analysis of skin-to-closure time, console time, and docking time. Based on the CUSUM curve for operative time, cases were divided into two phases: phase 1 (cases 1 to 36) and phase 2 (cases 37 to 66). Demographic, perioperative, and postoperative outcomes were compared between phases. Results: Sixty-six patients were included. Median age was 48.5 years, and median BMI was 27.45 kg/m2. Previous abdominal surgery was present in 80.3% of patients, and 47% had endometriosis. At least 25% of cases had elevated BMI and large uterine volume. CUSUM analysis identified a transition point after 36 cases, indicating completion of the initial learning phase. Median skin-to-closure time significantly decreased from 108 minutes in phase 1 to 85.5 minutes in phase 2 (p=0.029). Console time and docking time showed progressive improvement, although these differences did not reach statistical significance. Perioperative outcomes, complication rates, conversion rates, postoperative pain scores, and hospital stay were comparable between phases. Conclusion: Robot-assisted laparoscopic hysterectomy demonstrates a well-defined learning curve, with procedural stabilization achieved after approximately 36 consecutive cases. The successful and safe implementation of robotic gynecologic surgery, even for complex cases, is feasible during the initial adoption phase at a tertiary university center when supported by structured training and standardized workflows. Competing Interest Statement The authors have declared no competing interest. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Ethic Commission of Goethe-University , Frankfurt Frankfurt am Main- Germany approval no. 2023-1476 I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability We will provide our data for the reproducibility of this study if our institution approves the request.