Comparison of Two Control Methods for Minimally Invasive Surgical Instruments

Laparoscopic surgery is performed with long and slender instruments through one or several incisions in the abdominal wall. Steerable instruments with flexible distal tips have been developed for improving the ease of access to anatomic structures. However, the development of an intuitive and efficient control method for such steerable instruments remains a challenge. To determine which interface are most intuitive and effective to control steerable instruments, the current study evaluates the performance of novices in orienting the tip of a steerable laparoscopic forceps using thumb control or wrist control. Using two steerable instruments, one controlled by the thumb and the other by the wrist, 24 novices were divided into two groups that had to carry out an experimental task in an EndoTrainer with one of the two instruments. The participants had to orient the tip of the instrument relative to five targets that were presented in a random order. After a break, the participants switched to a second measurement session with the other instrument, followed by a third measurement session with the first instrument. Each participant performed the task 240 times over the three measurement sessions. The performance was assessed by measuring the performance time, using a questionnaire and grading the work load. The performance time showed a significant learning curve for each control method. The shortest performance time was recorded during the third session with both control methods (42.7 s for thumb control and 44.6 s for wrist control). A significant difference in the performance time was observed in the second session (p <0.02) but not in the first and third session. The questionnaire showed that most participants had a preference for thumb control. After a brief training period, thumb control and wrist control did not reveal significant differences in task performance. However, thumb control was strongly preferred by the participants due to the perceptive feeling in performance.