Ergonomic investigation of weight distribution of laparoscopic instruments

Laparoscopic surgery procedures require highly specialized visually controlled movements. Investigations of industrial applications indicate that the length as well as the weight of hand-held tools substantially affects movement time (MT). Different weight distributions may have similar effects on long-shafted laparoscopic instruments when performing surgical procedures. For this reason, the current experiment aimed at finding direct evidence of the weight distribution effect in an accurate task.

Ten right-handed subjects made continuous Fitts' pointing tasks using a long laparoscopic instrument. The factors and levels were target width: (2.5, 3, 3.5, and 4 cm), target distance (14, 23, and 37 cm), and weight distribution (uniform, front, middle, and rear). Weight distribution was made by chips of lead attached to the laparoscopic instrument. MT, error rate, and throughput (TP) were recorded as dependent variables.

There were significant differences between the weight distribution in MT and in TP. The middle position was found to require the least time to manipulate the laparoscopic instrument in pointing tasks and also obtained the highest TP.

These analyses and findings pointed to a design direction for the ergonomics and usability of the long hand-held tool such as the laparoscopic instrument in this study. To optimize efficiency in using these tools, the consideration of a better weight design is important and should not be neglected.