Limitations for manual and telemanipulator-assisted motion tracking and dexterity for endoscopic surgery

Abstract

Background: Surgical precision is limited by human factors. Surgery on a moving object requires full dexterity and motion tracking. Currently, techniques for total endoscopic surgery using telemanipulation systems are being developed. Aim of this study was to assess the limitations for manual and telemanipulator-assisted motion tracking using the da Vinci™ telemanipulator system. Methods: To simulate moving object conditions, an endoscopic trainer was developed. Twenty subjects were asked to touch targets manually and with telemanipulator assistance with different patterns of increasing index of difficulty (resting model, unstabilized and stabilized model with a frequency of 35, 60 and 90/bpm). In addition, one task was performed using different scaling ratios on a resting model. The times between hits as well as misses were electronically recorded. Results: There was no significant impact of various frequencies and amplitudes for manual tracking. The average values for the delay ( k m [ms]) and information-processing ( c m [ms/bit]) constants for the manual tasks were 201 and 86 ms/bit, respectively. As compared to manual control, the delay constant for the telemanipulator-assisted tasks of resting targets was three times longer ( k t=630 ms; p<0.0005) and the information-processing constant was less ( c t=250 ms/bit; p<0.0005). When working on moving targets, telemanipulator-assisted control and tracking required significantly more time and led to more errors. At a frequency of 90 bpm, telemanipulator-assisted control and tracking became almost impossible. Conclusion: Endoscopic beating heart bypass grafting requires an optimal stabilization to avoid inaccuracies due to incomplete motion control and tracking. At higher speeds (equaling a frequency of 90 bpm), control and tracking became almost impossible, demonstrating the technical limits of current telemanipulator technology.