1 2 3 5 task completion time 6 1 7 12 path length 13 14 15 1 16 17 Fig. 1 Three strategies of performing a goal-oriented movement in MIS. (a) a movement along the straight line between the initial and the end position; (b) a movement along a curved path between the initial and the end position, which is the result of the movement of the MIS instrument through the incision point; and (c) a realistic movement performed by the surgeon during the goal-oriented task. A – the initial position; B – the end position; P – incision (pivoting) point  The objective of this study was to examine goal-oriented movements during training of the basic MIS skills. The study consisted of two parts: first, we investigate whether goal-oriented movements can be split into two phases: a retracting phase and a seeking phase; and, subsequently, we investigate whether movements of the MIS instrument in these two phases depend on the surgeon’s experience. The performance of the participants was analyzed and compared using normalized path lengths. Methods Participants Experienced gynaecologists (with the experience of more than 100 MIS procedures), their residents (experience of 10–100 MIS procedures), and novices (medical students with no previous experience in MIS) were invited to participate in this study. Each participant, voluntarily enrolled in this study, was asked to complete a short questionnaire detailing demographic information and prior experience in laparoscopy. Task 2 Fig. 2 The positioning task. The task requires touching the top of the eight cylinders (of varying 3D position) with the tip of the MIS instrument. A correctly touched cylinder results in lighting up a lamp (above on the picture) corresponding to this cylinder. The start/end point and the order of touching the cylinders are indicated by the numbers located next to the cylinders  To mimic the in vivo gynaecological MIS situation, all participants performed the task with their left hand, while the camera was held in the right hand. To provide the same conditions for each participant, the position of the task and the incision points for the camera and the MIS instrument were standardized in the box trainer. The image of a 0° laparoscope was presented on a monitor. Before the test, all participants were instructed how to perform the positioning task. Furthermore, they were allowed to make one trial before testing. Data analysis 18 2 ABP 3 A B P ABP AB ABP A B 3 M AB AM A M MB M B \documentclass[12pt]{minimal}
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$$ {PL_{{{\rm normalized}\,\,}} = \,{{PL_{{{\rm real}\,}} \times \,100} \over {PL_{0} }}\,{\left[ \% \right]}} $$\end{document} PL real A M M B PL 0 A M M B Fig. 3 ABP A B P AB A B ABP ABP AB ABP AB ABP AB  Statistics p Results Participants Thirty-eight participants completed the task and the questionnaire. The group of experts consisted of 9 experts (age 38–59 years). The group of residents consisted of 17 gynaecological residents (age 29–41 years). The group of novices consisted of 12 medical students (age 23–28 years). All participants were right-handed. Retracting and seeking phases 4 M AB Fig. 4 ABP AB  5 Fig. 5 ABP AB p p p  ABP AB Influence of the experience 6 6 5 Fig. 6 p p  ABP AB Discussion Our findings indicate that goal-oriented movements are not performed via the shortest path. The movements clearly distinguish a retracting and a seeking phase. The results show that the normalized path length during the retracting phase is significantly shorter than during the seeking phase. Furthermore, experience in MIS does only influence the seeking phase. Experts’ and residents’ normalized path lengths were significantly shorter than the path lengths of the novices. The shorter path length in the seeking phase implies better performance; therefore, the seeking phase is characteristic of the differences in performance. This finding confirms that the path length is an important measure in the assessment of basic MIS skills, in which the seeking phase is the only component that can distinguish between novice and expert. AB AB AB ABP shorter path length To investigate whether the retracting phase really represents safety, it is necessary to design a different study. For example, one possibility would be to include obstacles which, upon touching represent an error. With such a study design, it would be feasible to determine how much retraction is necessary and whether the experts have learnt the optimal retraction amount. The present study cannot be used to decide on these aspects. The results of this study indicate that the comparison of the novices’ path length to the experts’ path length is an important and valid component of the overall criterion-based assessment of basic MIS skills. It is necessary to realize that this study was not designed to determine whether expert performance actually results in the optimal path length and, therefore, the results of this study cannot be used to indicate that experts’ movements are optimal. 13 AB This study shows for the first time the importance of proper analysis of the instruments’ movements during training of MIS skills. The clinical impact of such extended analysis is that only in this way is it possible to implement a correct objective score that will measure and certify the competence of surgeons’ basic psychomotor MIS skills in addition to the existing criteria for the assessment of MIS performance. Moreover, this extended motion analysis can result in improvement of the training of basic MIS skills, since it will identify the differences between the experts’ and novices’ performance, and which areas require more training. Conclusions shortest path length