Assessment of joystick and wrist control in hand-held articulated laparoscopic prototypes

Abstract

Background: Various steerable instruments with flexible distal tip have been developed for laparoscopic surgery. The problem of steering such instruments, however, remains a challenge, because no study investigated which control method is the most suitable. This study was designed to examine whether thumb (joystick) or wrist control method is designated for prototypes of steerable instruments by means of motion analysis.

Methods: Five experts and 12 novices participated. Each participant performed a needle-driving task in three directions (right → left, up → down, and down → up) with two prototypes (wrist and thumb) and a conventional instrument. Novices performed the tasks in three sessions, whereas experts performed one session only. The order of performing the tasks was determined by Latin squares design. Assessment of performance was done by means of five motion analysis parameters, a newly developed matrix for assigning penalty points, and a questionnaire.

Results: The thumb-controlled prototype outperformed the wrist-controlled prototype. Comparison of the results obtained in each task showed that regarding penalty points, the up → down task was the most difficult to perform.

Conclusions: The thumb control is more suitable for steerable instruments than the wrist control. To avoid uncontrolled movements and difficulties with applying forces to the tissue while keeping the tip of the instrument at the constant angle, adding a "locking" feature is necessary. It is advisable not to perform the needle driving task in the up → down direction.

Fig. 1

Three instruments used in this study. Up a conventional needle holder. Middle a prototype of the instrument with the tip steered by a thumb mechanism. Bottom a prototype of the instrument with the tip steered by a wrist mechanism

Fig. 2

Testing setup: a box trainer with a target plane (artificial skin pad), TrEndo tracking system, computer used to collect data, and the video system. The cover of the box trainer was nontransparent during performing the tasks

Fig. 3

The needle-driving task and the penalty matrix. The insertion, exit, and reference points, together with the penalty matrices, are presented for the up → down direction (up), down → up direction (middle), and right → left direction (bottom). The number of penalty points that is assigned to a needle-driving task is determined by the square in the penalty matrix, where the needle exits the artificial skin pad. Within the square, one of four subpenalties is added, determined by the quadrant in the square from where the needle exits

Fig. 4

The results (penalty points, time, and axial path length) of the three tasks performed by the novices using the two interfaces to control steerable prototypes. Results are presented as box and whisker plots, where every box has a line at every quartile, median, and upper quartile values. The whiskers are presented as lines that extend from each end of the box to show the extent of the rest of the data; a few extreme outliers are excluded from the plots to omit too much compression of the y-axis. *P < 0.05; **P < 0.01; ***P < 0.001; present differences between mean values. T thumb-steered prototype, W wrist-steered prototype, R → L right → left task, U → D up → down task, D → U down → up task

Fig. 5

The results (rotational orientation, rotational orientation alpha, and rotational orientation phi) of the three tasks performed by the novices using the two interfaces to control steerable prototypes. *P < 0.05; **P < 0.01; ***P < 0.001; present differences between mean values. T thumb-steered prototype, W wrist-steered prototype, R → L right → left task, U → D up → down task, D → U down → up task

Fig. 6

The results of the three tasks performed by the experts using the conventional instrument and the two interfaces to control steerable prototypes. Results are presented as lines, in which each line represents an experts’ mean score of penalty points