An ergonomic analysis of the fulcrum effect in the acquisition of endoscopic skills

Background: The loss of three-dimensional visual depth cues has been thought to be the main hindrance to the acquisition of endoscopic skills. However, the "fulcrum effect" of the abdominal wall on the manipulation of instruments has not to our knowledge been previously investigated. Methods: Subjects with no experience in endoscopy were required to make multiple defined incisions under laparoscopic laboratory conditions, within ten two-minute periods in the fil st study and 50 in the second. Eleven subjects operated under normal imaging conditions and 11 with the y-axis inverted. Results: Subjects who operated with the image inverted made significantly more incisions and significantly more correct incisions than those working under normal conditions. This effect persisted over 50 trials. Conclusions: The fulcrum effect has a major detrimental influence on acquisition of endoscopic skills. Further work is required to investigate the role of image inversion in clinical endoscopic training.