Influence of anatomic landmarks in the virtual environment on simulated angled laparoscope navigation

Fifty-four participants took part in this study. During three advanced laparoscopic skills courses and five basic surgical skills courses, trainees, faculty and staff of the institutes where the courses took place were invited to participate. In the information they received it was clearly stated that the researchers were not affiliated with the manufacturer of the simulator and that all data would be analysed anonymously. The participants filled out an informed consent form and a questionnaire about their demographics and general medical and laparoscopy experience.

Participants were allotted to one of two groups based on their experience with laparoscopic surgery as indicated in the questionnaire. Participants in the experienced group (Table 1) indicated to have performed more than 100 basic laparoscopic procedures clinically (such as cholecystectomies or appendectomies) and at least five advanced laparoscopic procedures (such as Nissen fundoplication or bariatric surgery), plus to be experienced with using a 30° angled laparoscope. In addition, performance on the Place Arrow (PA) task was used to verify the expertise level of the experienced participants. The performances on the PA task of three participants allotted to the experienced group were labelled as extreme outliers (z-score > 3.29), so these participants were excluded from this group. A novice group was formed by medical trainees with the minimum knowledge level of a general surgical intern, but with no clinical experience in performing laparoscopic procedures (Table 1).

Within both the experienced (N = 28) and novice (N = 23) groups, no significant differences were found between the performances of subgroups A (CN-box followed by CN-abdomen) and B (CN-abdomen followed by CN-box) on the angled laparoscope navigation task in the abstract environment (CN-box task) or in the virtual representation of the lower abdomen (CN-abdomen task). This implies that the influence of the order in which the CN tasks were performed is negligible. The performances of the subgroups were therefore combined for further analysis. None of the participants encountered tool–tool collision in the PA task, while in the CN tasks only two participants (one novice and one experienced participant) recorded one collision each with the camera to the target. Therefore, the scores on tool–tool collision, tool–tool collision time and camera target collision were excluded from the analysis.

In the experienced group, the CN-box task was accomplished in significantly less time (Fig. 3) and with shorter total tip trajectory (Fig. 4) than the CN-abdomen task. The same held for the novice group. No significant differences were found between the CN task in the two different surroundings for the number of targets lost out of view or the average speed per instrument tip (Figs. 5 and 6).

The scores of the experienced group did not differ significantly from the scores of the novice group on both the CN-box task and the CN-abdomen task. However, on the PA task the experienced group significantly outperformed the novice group. The experienced group accomplished the PA task in significantly less time (p < 0.001) and with shorter total tip trajectory (p < 0.001). In the experienced group the speed per instrument tip was also significantly faster (p = 0.032).

After performing all tasks on the simulator, the participants were asked to rate the educational value of the tasks and whether they experienced a difference between the perceived and anticipated level of difficulty of the tasks (Table 2). The opinion of the experienced and novice groups only differed significantly for the difference between the perceived and anticipated level of difficulty of the PA task (p = 0.011).

Due to the new European working-time directives (EWTD) and economical and ethical considerations, clinical training of surgical skills is losing acceptance and preclinical training and proficiency assessment on VR simulators are becoming increasingly more common [1‐3]. Handling an angled laparoscope and navigating with it within the abdominal cavity are basic laparoscopy skills for which the general value of simulator training and transfer of skills to the clinical setting has been proven [8‐10]. However, more in-depth knowledge is still needed on the physical and cognitive aspects of the interaction with the instrumentarium and interpretation of visual information during image-based procedures such as laparoscopic surgery. The visual environment in which simulator tasks are to be performed could be of influence, as was confirmed in our study.

The results of our study indicate that performances on the angled laparoscope navigation task on SimSurgery SEP differed significantly between the abstract environment and the virtual abdomen environment. The performances in the abstract virtual environment surpassed the performances in the virtual environment with anatomic landmarks in both the experienced group and the novice group. These results could (partly) be clarified by the fact that the abdominal environment used in this study was still a virtual-reality representation of the abdominal cavity. The anatomy of the abdominal cavity is a very familiar environment to laparoscopic surgeons. Hence, minor deviations in the representation of the anatomy or flawed computer graphical representation could have drawn their attention immediately and distracted them from performance of the CN task. Also, even though the novice group was inexperienced in laparoscopic surgery, with the minimum knowledge level of a surgical intern they were all supposed to be familiar with the anatomy of the abdomen. Consequently, just like the experts, they may also have been distracted from their task. It could also be that, due to the limitations of computer graphics, the level of detail of the anatomy was not sufficient to create a realistic experience of perceiving the abdominal cavity as in the operating room setting to allow skill-based behaviour by the experienced surgeons. Some surgeons commented that the CN task required too precise and sometimes too close visualisation of the targets, in this way not representing the flexibility of visualisation of anatomic structures in the operating room. This relates to personal preferences of some surgeons on visualisation of the operating field or variations that are dependent on the therapeutic task to be visualised. Finally, the performance assessment on the basis of the scores provided by the simulator could have had an influence. Each task on SimSurgery SEP incorporates several quality parameters which play a key role in accomplishing the tasks successfully. Still, the output generated by the simulator at the end of each task only presents time needed to accomplish the task, total tip trajectory and specific error scores. It could be that a potential difference in navigation with an angled laparoscope is not reflected by these individual rudimentary scores, but should be identified by other, more sophisticated performance parameters (e.g. parameters related to specific aberrations from the optimal tip trajectory, or parameters that take multiple factors into account).

VR simulators could play an important role in fulfilling the desire for objective proficiency assessment and in accomplishing a shift towards criterion-based training. The development of criterion-based training programmes with also a stronger focus on the needs of the individual trainee will most likely improve the efficiency and efficacy of laparoscopy curricula and decrease the incidence of under- or over-training [2]. However, this approach necessitates better understanding of the influence and function of different types of intrinsic and extrinsic feedback when performing different types of tasks on a simulator. The focus of future research should therefore be more on the quality of the performance and the development of more sophisticated and comprehensive performance metrics.

While the CN-box task was accomplished in significantly less time and with shorter total tip trajectory, the average speed of the instrument tips did not significantly differ. It appears that the participants followed a longer route to find and properly visualise the targets in the CN-abdomen task. The simulator data does not provide details on the actual path followed with the instrument, only on the total length. Chmarra et al. [11] analysed the shape of the path of instrument tips for a simple eye–hand coordination task with a laparoscopic grasper and identified a retracting phase and a seeking phase. Instead of following the actual shortest route between two points, being a straight line, a pull-back movement is performed first before the target is approached [11]. This pull-back movement is essential to minimise the chance of touching tissue unnecessarily and ensure patient safety. Possibly, the presence of anatomic landmarks instigated a more cautious behaviour. However, this could also be related to the irregular shape of the environment and the presence of obstacles in the CN-abdomen task versus the open and clear space in the CN-box task. Then again, similar results were found in both the novices and experienced groups, which suggests that the latter is less likely to be the case.

The questionnaire data (Table 1) show that the assisting surgeon usually handles the laparoscope. In the early days of laparoscopic surgery, many surgeons started immediately with performing the therapeutic actions with an assistant or resident holding the laparoscope, while in many teaching hospitals the senior surgeon would fulfil the role of assisting surgeon in less complicated laparoscopic procedures performed by surgical residents. This implies that senior surgeons would handle the laparoscope on a regular basis, but only during procedures involving uncomplicated utilisation of the angled laparoscope. In contrast, the younger generation of laparoscopic surgeons generally started their laparoscopic career by handling the laparoscope to assist the primary operating surgeon, during both straightforward procedures and procedures requiring more sophisticated manipulation of the laparoscope. Consequently, one might expect that the younger generation has more experience with manoeuvring laparoscopes. This could be a plausible explanation for the lack of difference in performance of the CN tasks between novices and experienced laparoscopic surgeons. Therefore, we also investigated whether the simulator performances within the experienced group were affected by the age or the years of laparoscopic experience of the participants in the experienced group. The results though did not reveal any significant differences.

In the questionnaire, the experienced participants were asked to rate whether the CN-abdomen task was a more effective tool than the CN-box task to train novices or assess experienced laparoscopists in angled laparoscope navigation (Table 2). Although the opinions upon these questions were divided, the CN-abdomen task was rated to be more effective to train novices than the CN-box task. This suggests that the requirements for a simulator for training are perceived to be different from the requirements for a simulator for assessment of laparoscopic proficiency. Just as in one of our previous studies, the CN task was rated as being more challenging than anticipated beforehand, and also more so than the PA task [5]. The study was performed during laparoscopic courses that made extensive use of box trainers or living animals, often using 30° angled laparoscopes, and sometimes also VR simulators. Frequently, the participants worked in pairs, with one person handling the laparoscope while the other performed the training task. However, somehow, the participants did not recognise this as simulation training, because many of the experienced surgeons stated to have none or only brief experience with simulations for either laparoscopic tissue manipulation or laparoscope navigation (Table 1).

The performances of experienced laparoscopic surgeons on an angled laparoscope navigation task on the SimSurgery SEP VR simulator differed significantly between the abstract environment and the virtual environment of the abdomen with anatomic landmarks. The task was performed with better simulator scores in the abstract environment, opposite to the propositions of several experienced laparoscopic surgeons in a previous study. In the group with inexperienced medical trainees, a similar difference in performances was found. This means that the influence of the virtual environment on the task performance was not related to level of experience. Further research should focus on extending knowledge on the influence and function of different types of intrinsic and extrinsic feedback provided by the simulator on the effectiveness of preclinical training (e.g. the realism of the task and its surroundings, and the added value of haptic feedback). The criteria and parameters used to assess task performance for different types of laparoscopy skills need to be further investigated as well.