Education and training content for surgical residents and trainees includes history-taking, physical examination, treatment planning, surgical technique, and perioperative management. Among these aspects, the evaluation of residents’ surgical technique is crucial to validate their completion of education and training. Acute appendicitis is one of the most common diseases that surgeons encounter, and appendectomy has been ranked first among general surgical emergencies that occur in Korea [1]. Appendectomy is frequently conducted by surgical residents, so it can be a barometer for competency in basic surgical techniques among surgical residents [2-5]. Since Semm [6] reported the outcomes of laparoscopic appendectomy (LA), most appendectomies have been performed via laparoscopy. Better short-term outcomes such as less postoperative pain, shorter hospital stay, and earlier return to daily life as well as improved safety and feasibility have been demonstrated following using the laparoscopic approach to treat appendicitis over the conventional open procedure in several reports [7-10]. Therefore, LA can serve as an evaluation standard for the education and training of surgical residents.

Several reports have already highlighted LA as a viable assessment of education for surgical residents. Among them were reports showing that surgery performed by residents resulted in similar clinical outcomes as those following surgery conducted by attending or supervising surgeons [11-13]. Others have sought to delineate the learning curve (LC) for LA performed by residents [14-17]. However, limitations in this regard existed such as the heterogeneity of surgical residents, choosing and dividing enrolled patients arbitrarily without proper statistical methods, and a retrospective design.

The aims of the present study were to delineate the LC for LA performed by surgical residents using a multidimensional statistical analysis and to assess surgical technique advancement according to seniority based on residency year.

Based on evidence that surgical skill level can affect clinical outcomes, various methods have been introduced to evaluate surgical skill [21-23]. Although there are commercially available training systems for minimally invasive surgery such as computer-enhanced laparoscopic training systems, laparoscopic surgical workstations, and virtual reality simulators, limited opportunities may be available to residents due to the high cost and low compatibility of these systems [24, 25].

LA has been widely accepted as a parameter to use in evaluating the effectiveness of education and training for surgical residents. First of all, resident involvement did not increase the level of risk to patients, despite past controversy [11-13, 26-28]. Similarly, a comparison of the outcomes between residents and staff surgeons suggested that LA as performed by residents was generally safe (Table 4). Although a small difference was noted in OT (50.1 minutes vs. 38.3 minutes, P<0.001), this did not significantly affect outcomes and could be overcome by accumulating further experience.

There have been a few studies conducted assessing the LC for LA performed by residents. Kim et al. [15] reported the LC for LA by a single trainee but simply divided the trainee’s patients and compared subgroups without appropriate statistical analyses. Elsewhere, Lin et al. [16] analyzed the LC for LA procedures completed by 6 residents but dichotomized and compared patients without any statistical methods and grouped all residents together to analyze the LC, ignoring variations in ability and adaptation of each resident unintentionally. Jaffer and Cameron [29] sought to determine the LC for LA using statistical methods for OT. The LC that they suggested (n=20) was the same as that in the European Association for Endoscopic Surgery (EAES) consensus statement [30]. OT is an important and widely used item in the assessment of LC in many other surgeries, including cholecystectomy, gastrectomy, and colectomy as well as appendectomy. However, it is important to reduce intraoperative or postoperative morbidity as well as to perform the surgery faster. Recent studies have used not only OT but also other parameters to analyze LCs more accurately and objectively. Kim et al. [19] used 4 parameters to assess the LC for single-incision laparoscopic colon cancer surgery, which were conversion, postoperative complications, less than 12 lymph nodes, and local recurrence. Several authors have selected similar methods for various procedures [31, 32].

We recruited residents from each grade and employed multidimensional statistical analyses for surgical failure as well as OT to avoid the limitations of previous studies such as a lack of reflection on the advancement of surgical skills and techniques during resident training, reliance on a single resident’s experience, inadequate statistical analysis, and OT alone as a parameter. Considering perioperative outcomes from residents at different years of schooling (e.g., first year vs. third year) can facilitate the assessment of how the accumulation of surgical experience affects the LC, and we hypothesized that senior residents would show mastery of the procedure earlier on than junior residents. In terms of OT, the third-year resident (resident C) reached a steady state for his OT last, although the gap was only 5 minutes, whereas the first-year resident (A) reached her steady state last in terms of surgical failure (Figs. 2, 3). Although the senior resident went relatively slow and more strongly pursued the completeness of surgery compared to the junior resident, this difference suggests that the accumulation of surgical experience could affect surgical completion rather than OT.

Based on the accumulation of “assistance-experience” of residents during their residency training with similar “performanceexperience” (i.e., they had similar experiences with LA as an operating surgeon before starting the study), we carefully suggest that increased assistance-experience could help residents adapt to surgery and become stable earlier on in their schooling, although collecting performance-experience is definitely important as well. Resident B performed at a proficient level sooner than A and C in terms of both OT and surgical failure. However, the gap between residents B and C was only 5 cases in terms of surgical failure, whereas the gap between resident A and residents B or C was 19 to 24 cases (Fig. 3). In addition, only 2 of resident B’s patients underwent LA for perforated appendicitis, whereas residents A and C performed LA in patients presenting with perforated appendicitis in 10 and 11 cases, respectively. Further, resident B performed the 2 perforated LA cases as her fifth and 13th cases and showed 3 surgical failures before her 11th case, whereas resident C showed a relatively equal distribution of perforation of the appendix but experienced 3 surgical failures before his 16th case.

One of the limitations of CUSUM is dependence on the sequence of events. In terms of surgical failure, if a resident experiences surgical failure only early on, his or her CUSUM would yield better results. In other words, easier cases were predominant later in the study period for resident B and, consequently, surgical failure was rare. In contrast, although relatively more difficult cases were evenly distributed throughout the study period for resident C, he rarely experienced surgical failure later in the study period. This difference is also due to the approach of nonrandomization without stratification of potential influencing factors and could explain why resident B reached a steady state for OT earlier on than her senior, resident C. We sought to identify factors for surgical failure but found that only basal appendix perforation was significantly associated. However, when inflammation and peritonitis were more severe, the surgery was more difficult to conduct, which could affect the surgical failure risk despite a lack of significance in this study (Table 3).

To the best of our knowledge, this is the first comparative study to assess the LC for LA performed by residents according to the level of seniority in training using a multidimensional analysis approach. However, some limitations are inevitable. First, randomization was not performed, so a higher level of evidence could not be attained. Specifically, various factors can cause an imbalance in the difficulty of the surgery, such as BMI, location of the appendix, and perforation, and these factors need to be stratified for true randomization. Second, the emphasis placed on patient safety could possibly influence the enrollment of relatively easier cases despite the very small number of excluded patients (6.1%; 22 and 6 patients were suspected to have intra-abdominal abscess and malignancy on imaging studies, respectively). Third, the definition of surgical failure could be subjective because the concept of surgical completion varies from surgeon to surgeon. Fourth, the sample size was small and only one resident in each grade was recruited for this study, and there is the possibility that certain residents were technically more able than others. If more residents participated in a randomized controlled trial, it is expected that we could obtain a more solid conclusion. LC may be influenced not only by the surgical abilities of individuals but also their personal characteristics. Lastly, the relatively lower BMI of Asian patients could affect the accuracy of generalization of our results to other populations.

In conclusion, the resident LC for LA was 11 to 35 cases according to multidimensional statistical analyses. Senior residents tended to show mastery of the procedure earlier than their junior counterparts. The accumulation of surgical experience among residents may affect the LC for surgical completion but not that for OT. Although the experience of surgical assistance is thought to be less important than that of surgical performance in surgical resident training, such may still help to improve surgical completion rates and shorten the LC.