Retracting and seeking movements during laparoscopic goal-oriented movements. Is the shortest path length optimal?

Minimally invasive surgery (MIS) requires a high degree of eye-hand coordination from the surgeon. To facilitate the learning process, objective assessment systems based on analysis of the instruments' motion are being developed. To investigate the influence of performance on motion characteristics, we examined goal-oriented movements in a box trainer. In general, goal-oriented movements consist of a retracting and a seeking phase, and are, however, not performed via the shortest path length. Therefore, we hypothesized that the shortest path is not an optimal concept in MIS.

Participants were divided into three groups (experts, residents, and novices). Each participant performed a number of one-hand positioning tasks in a box trainer. Movements of the instrument were recorded with the TrEndo tracking system. The movement from point A to B was divided into two phases: A-M (retracting) and M-B (seeking). Normalized path lengths (given in %) of the two phases were compared.

Thirty eight participants contributed. For the retracting phase, we found no significant difference between experts [median (range) %: 152 (129-178)], residents [164 (126-250)], and novices [168 (136-268)]. In the seeking phase, we find a significant difference (<0.001) between experts [180 (172-247)], residents [201 (163-287)], and novices [290 (244-469)]. Moreover, within each group, a significant difference between retracting and seeking phases was observed.

Goal-oriented movements in MIS can be split into two phases: retracting and seeking. Novices are less effective than experts and residents in the seeking phase. Therefore, the seeking phase is characteristic of performance differences. Furthermore, the retracting phase is essential, because it improves safety by avoiding intermediate tissue contact. Therefore, the shortest path length, as presently used during the assessment of basic MIS skills, may be not a proper concept for analyzing optimal movements and, therefore, needs to be revised.