This current study of surgical trainee’s performance found that training level and disease state influenced performance scores in real-life laparoscopic appendectomies. In assessing surgical competency, ideally one would include as many aspects as possible of the procedure [18]. Hence, both internal and external factors should be considered when evaluating surgical trainees performing a surgical procedure such as a laparoscopic appendectomy.

In this study we found an association between perforation state and the procedure being designated difficult by the trainer, yet only 9 (47%) of 19 perforated appendices were designated difficult. This suggests that disease severity influences on difficulty but that other factors than perforation may contribute to technical challenges during a procedure. Disease severity tends to be related to perforation state, i.e., such as proposed by the American Association for the Surgery of Trauma (AAST) grading system for acute appendicitis severity [19]. This is also consistent with the findings of a prospective observational trial [20] which demonstrated that the need for preoperative CT scan and a higher Appendicitis Inflammatory Response (AIR) score [21] resulted in a higher risk for a difficult appendectomy, defined as the need for help from an expert surgeon. Both the need for a preoperative CT and a higher Appendicitis Inflammatory Response (AIR) score will indicate a more advanced disease state.

The regression analysis demonstrated a very strong association between trainee experience and the achievement of proficiency. This association is in agreement with other studies that suggest a learning curve of 20–30 cases [22, 23] and thus trainee’s that have performed more than 30 cases would be considered proficient. However, studies indicate that improvement of surgical outcomes continue beyond the first 30 procedures [23].

Trainee’s performing a difficult procedure, had a significantly lower proficiency rate, compared to those who performed procedures not designated as difficult. From other studies, it is known that several factors can increase the risk of conversion from laparoscopic to open surgery and hence indicate a difficult procedure. These factors include severe inflammatory adhesions, high grades of appendiceal inflammation and perforation [24]. Patient anatomy, adhesions after prior surgery, obese patients and other patient factors can also increase the difficulty, and in a prospective observational trial [20], patient obesity (defined as Body Mass Index (BMI) > 30 kg/m2) resulted in a significant higher risk for a difficult procedure. Surgeon factors such as laparoscopic inexperience [24] also increases the risk for conversion from laparoscopic to open surgery. It is thus not surprising that inexperienced trainees will have a lower proficiency rate in difficult procedures—independent of the reason for the procedure being deemed difficult.

In a previous study [25] it was demonstrated that the chance of obtaining “proficiency” in a laparoscopic appendectomy was related to whether or not the trainee was able to complete each of the procedural steps. This current study further elaborates on how achieving proficiency also will depend on how challenging the procedure is—and this can depend on internal as well as external factors. Many of the contributing factors that play a role on performance cannot be controlled for but should be taken into consideration when deciding whether a patient planned for a procedure is suitable for a trainee to perform on. Particularly challenging steps of a procedure can be used as basis for developing specific training opportunities, i.e. by the use of simulation-based training. This will in turn enable deliberate practice—that is, training with focus on improving a particular task [26]—a prerequisite for competency-based surgical education [27].

Comparing the operating time in this study, we found no significant difference between the inexperienced and the experienced trainees. This stands in contrast with other studies [5, 28, 29], and a retrospective review [22] even demonstrated an almost linear reduction in operation time with increasing experience, which will indicate that the operative learning curve continues the first years after achievement of proficiency before reaching a plateau [6]. Operating time could also have implications for patient care as prolonged operating time is associated with an increased risk of postoperative complications [30]. However, in our current study cases that presented in an advanced disease state were not include as “training cases” in this real-time setting [31], and these cases have been demonstrated to increase operating time to such extend that one study even found that operating time was higher for trained surgeons than for trainees [6].

Previously we found an association between various procedure steps for laparoscopic appendectomy and the number of procedures required to achieve proficiency for any step [15]. The step involving division of the mesoappendix had the highest number of procedures required to achieve proficiency, and we suspect this may be related to varying degrees of inflammation possibly affecting the technical performance of the procedure. In this study, identifying the appendix had the lowest achievement of proficiency in the challenging cases.

The patients whose procedures were designated as “difficult” had significantly longer operating time than the “non-difficult” procedures (median 90 min vs 59 min; p < 0,001).

Some limitations to the study need to be mentioned. Due to the design of the study and the regulation of the regional ethics committee, no patient—nor procedure-specific information was recorded during the study. Hence, no recording of patient age, gender, body mass index, prior medical or surgical history was available. The anatomical description of the appendix was not reported, i.e. whether freely located in the pelvis or, alternatively, found as a retrocoecally placed organ. Variations in visceral fat, prior surgery or anatomical location could clearly have impacted on the procedure. Further, the procedure being designated as “difficult” was an individual judgement by the individual trainers. The trainers were not asked to register why the procedure was considered difficult (such as adhesions from previous surgery; visceral obesity; retrocoecally located appendix, or any other reason), and this combined with the individual judgement could represent a potential bias. For future studies, we believe these datapoints should be registered to better understand what makes a procedure being designated as “difficult”. Also, the trainers were either senior residents (more than 4 years of surgical training) or consultant surgeons with varying experience, and the trainer experience with laparoscopic surgery could have an influence on the individual judgement. An experienced trainee may also make the surgery appear less challenging due to his or her prior experience. Hence, we propose to make the “difficult” judgement more objective in the future with a formal assessment of what factors contribute to a difficult procedure.

Furthermore, the appendicitis severity was dichotomized into perforated and non-perforated, which may not reflect a more nuanced grade of disease impact on procedure performance. A more formal evaluation could have been entertained, with designation into more specific categories, such as the AAST severity score grading [11] to assess the local appendicitis situation. Others have evaluated the AAST severity score and validated its role in assessing severity for appendicitis [19, 32]. As disease severity may impact on procedure performance, it is important to consider this information as it may impact on the difficulty grade and the ability to master a procedure. Both patient-specific factors (age, gender, and body mass index, anatomical variation and prior surgery) and disease-specific factors (i.e., Appendicitis Inflammatory Response (AIR) score and AAST grading) should ideally have been registered in this study to better inform on the details of internal and external factors. While this was beyond the scope of the current project, future projects should address these items to help better understand the impact on training and performance.

The concept of “complicated appendicitis” has been thoroughly studied throughout the last decades. However, for both surgical trainees and trainers, the “complicated appendectomy” will be even more important to consider as external and internal factors will be an important confounder when evaluating trainee performance in a real-life setting. Even though it is not possible to control for disease severity, registering factors that constitutes a complicated appendectomy can give a better evaluation of proficiency among surgical trainees.