Table 1.

Studies reporting on learning curve during urgent/emergent minimally invasive surgery

References	Study design	Time period	Surgical emergency	Nb. of pts/procedures	Type of intervention	Surgeons involved	Surgeon experience	Groups calculation and methods	Outcomes (on which LC was evaluated)	Main results	Estimated learning curve
Jaffer et al (2008) [29]	Retrospective observational study - prospectively collected database	May 2005 - November 2006	Appendicitis	40	Laparoscopic appendectomy	1	NR	4 groups (10 pts each) - according to moving average method and CUSUM	OT CR	OT was significantly shorter after 20 cases (p < 0.0001). CR decreased after 20 cases	20 cases are sufficient to gain competences in term of operative time and conversion rate
Kim et al (2010) [27]	Retrospective observational study with subgroup analysis	March 2008 - December 2008	Appendicitis	103 (50 laparoscopic, 53 open)	Laparoscopic and open appendectomy	1	Single 2nd year resident who had performed > 30 open appendectomies (Supervised)	Subgroup analysis for laparoscopic cases: 5 groups (10 pts each) - according to moving average method	OT LOS CR	OT was significantly shorter after 30 cases LOS and CR were comparable	The LC is reached after 30 operations
Lin et al (2010) [21]	Retrospective observational study	January 2002 - December 2007	Appendicitis	240	Laparoscopic appendectomy	6	Residents (FLS certified; trained in basic laparoscopy in wet and simulation laboratories for 2–4 years while assisting in simple laparoscopic surgeries (Supervised)	2 groups (120 pts LC; 120 pts after LC)	OT POC LOS CR	OT was significantly shorter after the LC. (p = 0.005). POC rate was significantly reduced after the LC. (p = 0.04) LOS and CR were not different between the two groups	The LC is reached after 20 cases only for OT
Liao et al (2013) [22]	Retrospective observational study with subgroup analysis	July 2009 - June 2010	Appendicitis	30	Laparoscopic single port appendectomy	1	At least 30 conventional three-port laparoscopic appendectomy	3 groups (10 pts each) - consecutively assigned	OT POC LOS CR TTOI	OT were longest in the first group (P = 0.017). No difference in CR, TTOI, LOS, POC	Significant improvement in OT after the first 10 cases. An experience of 30 cases achieved an OT equivalent to conventional three-port laparoscopic appendectomy First 10 cases had a much steeper downward slope of OT. (–1.5 min/case)
Abdelrahman et al (2016) [31]	Retrospective observational study	August 2007 - August 2014	Appendicitis	/	Laparoscopic and open appendectomy	69	Higher surgical trainees from 3rd to 8th year	According to procedural-based assessment	Procedural-based assessment	Three consultant-validated PBAs at level 4 (competent to perform independently and deal with complications) are reached after 107 cases	The proficiency is reached after 107 cases (median) The number is 35% higher than the number imposed to certify the trainee
Kim et al (2016) [23]	Retrospective observational study	March 2013 - February 2015	Appendicitis	120	Laparoscopic single port appendectomy	1	More than 500 open appendectomy; more than 500 laparoscopic appendectomy	4 groups (30 pts each) - consecutively assigned	OT POC LOS CR TTOI	OT were longest in group A and shortest in group D (P = 0.012) The mean OT was shortened after 30 operations, it was further shortened after 90 operations No difference in POC, LOS, TTOI, CR	Surgical skills can be achieved after 30 operations and more experienced surgical skills after 90 operations
Mán et al (2016) [24]	Retrospective observational study	January 2006 - December 2009	Appendicitis	600	Laparoscopic appendectomy	10	5 residents (2—3 years of surgical experience) Completed a two-week basic laparoscopic skills course and assisted in other laparoscopic procedures (Supervised) 5 consultants (8—9 years of surgical experience) Regularly performed other surgical procedures independently (Supervised)	4 groups (100 pts residents LC; 100 pts consultant LC; 219 residents after LC; 181 consultants after LC) - consecutively assigned	OT POC LOS CR	OT was significantly shorter in both groups (residents and consultants) after the completion of the LC (P < 0.05) The OT was significantly different between the two groups, before and after the completion of the LC (P < 0.05)	The LC is reached after 20 cases both for residents and consultants
Brown et al (2017) [32]	Retrospective observational study	August 2007 - August 2016	Appendicitis	/	Laparoscopic appendectomy	84	Higher surgical trainees from 3rd to 8th year	According to procedural-based assessment	Procedural-based assessment	Three consultant-validated PBAs at level 4 (competent to perform independently and deal with complications) are reached after 95 cases Significant variance was observed in the gradients of all LC related to both the caseload between the first level 3 and the first level 4 PBA (P = 0.001), and between the first and third level 4 PBAs (P < 0.001). Significant variance was also observed in the gradients of all learning curves related to time between the first and third level 4 PBA (P = 0⋅025), but not related to the period between the first level 3 and first level 4 PBA (P = 0.732)	The proficiency is reached after 95 cases (median)
Kim et al (2020) [30]	Retrospective observational study	October 2015 - November 2016	Appendicitis	150	Laparoscopic appendectomy	3	Resident A (1st year 96 surgeries comprising 19 appendectomies and performed 4 laparoscopic appendectomies.) Resident B (2nd year, participated in 272 general surgeries comprising 42 appendectomies and performed 3 laparoscopic appendectomies) Resident C (3rd year, participated in 510 general surgeries comprising 98 appendectomies and performed 4 laparoscopic appendectomies)	(50 pts each resident) - according to moving average method and CUSUM	OT Surgical failure	CUSUM for OT exhibited peaks at the 24th, 18th, and 31st cases for residents A, B, and C, respectively In terms of surgical failure, residents A, B, and C reached steady states after their 35th, 11th, and 16th cases, respectively No significant difference in surgical failure but resident A showed a relatively equal distribution of surgical failure throughout the study period, whereas residents B and C experienced surgical failure earlier on	According to the OR, the LC varies depending on surgical experience ranging from 11 to 35 cases based on a multidimensional analysis
Lee et al (2021) [25]	Retrospective observational study	May 2008 - November 2014	Appendicitis	1948	Laparoscopic single port appendectomy	41	8 surgeons 33 residents (training protocol: at list 10 cases as assistant then first three procedures supervised)	2 groups (483 pts LC; 1465 pts after LC)	OT POC LOS CR HRR Mortality	After a PSM: OT was significantly longer in group 1 than in group 2 (p < 0.001) POC, LOS, CR, HRR and mortality were comparable The rate of incisional hernia tended to be larger in group 1 than in group 2	The LC is reached after 40 cases
Ussia et al (2021) [26]	Retrospective observational study	January 2013 - December 2018	Appendicitis	1173	Laparoscopic appendectomy	73	9 attendings 64 residents (asked to spectate several cases before assisting)	Comparison after PSM: (409 pts attendings 409 pts residents)	OT POC LOS Mortality	After a PSM: LOS was significantly longer in attendings group (p < 0.007) OT, POC and mortality rate were comparable After stratification: OT was significantly reduced only in edematous and suppurative cases as the number of years of training increased CUSUM for OT showed a reduction in OT for attendings at around 300 cases (more than 30 pts/surgeon)	Not specified
Angeramo et al. [28]	Retrospective observational study	June 2000 - December 2019	Postoperative complications in colorectal surgery	132	Various laparoscopic procedures (Lavage and loop ileostomy; resection, redo anastomosis; lavage and drainage; anastomosis takedown; wall repair; bowel repair; adhesiolysis; internal hernia reduction)	3	National board-certified colorectal surgeons	3 groups (50, 52 and 30 pts each) - according to CUSUM analysis (for OT)	OT POC LOS CR Mortality	CR was higher in the first group (P = 0.02) OT was higher in the first group (P = 0.003) Overall postoperative morbidity was lower in the last group (P = 0.01) Major morbidity, mortality and LOS were comparable across the LC	50 re-laparoscopies might be needed to achieve an appropriate LC reducing OT and CR
Kubat et al. [20]	Retrospective observational study with subgroup analysis	May 2012 - August 2013	Acute cholecystitis, biliary pancreatitis, choledocholithiasis, severe chronic cholecystitis, symptomatic cholelithiasis, gallbladder polyposis	150 (76 elective surgery, 74 urgent surgery)	Robotic single port cholecystectomy	1	Experienced minimally invasive surgeon (both in multiport robotic cholecystectomy and in single-incision laparoscopic cholecystectomy)	3 groups (48, 47 and 55 pts each) - according to CUSUM analysis (for OT) Subgroup analysis for urgent cases: 3 groups (35, 34 and 15 pts each)	OT POC LOS CR HRR Mortality	OT was significantly shorter in elective interventions compared with urgent interventions (P < 0.05) LOS was longer in urgent cases (P = 0.003)	The LC is reached after 48 operations, inclusive of urgent and elective cases In the subgroup analysis, the first phase of the CUSUM chart was 25% longer in urgent cases compared to elective cases

Pts patients; LC learning curve; NR not reported; OT operative time; POC postoperative complications; LOS length of stay, CR conversion rate; TTOI time to oral intake; CUSUM cumulative sum; HRR hospital re-admission rate; PSM propensity score matching; FLS fundamentals of laparoscopic surgery