Abstract Background and Purpose: Placement of the fourth arm (4th arm) in the lower quadrant (LQ) is commonly described for robot-assisted renal surgical procedures but has anatomic restrictions and limited ergonomics. An alternative, upper quadrant (UQ) location is desirable, but patient habitus and spacing may restrict robotic attachment. We investigate current trends in 4th arm port placement and propose an alternative method at attaching the robot-the "Floating Arm" (FLA).
Methods: Robotic surgeons from the Endourological Society were surveyed. A 20-cm extra-long (XL Protype) da Vinci instrument was developed for the FLA technique. A dry lab allowed quantitative comparison of spacing and ranges of motion for standard da Vinci ports (dVP), bariatric dVP, telescoping dVP, and FLA.
Results: There were 108 respondents who participated. Half of the respondents avoid using the 4th arm (30% lack of need and 20% because of interference). The majority (90%) typically positions the 4th arm in the LQ, but many reported limitations in this location. Few (5%) place 4th arm in the UQ, while most (73%) have never heard of UQ placement. Existing techniques may increase shoulder height clearance but inversely shorten the working length of the instrument intracorporeally. Alternatively, the XL Protype significantly increased the shoulder length and maintained available working distances intracorporeally. Adjacent arm interference angle was essentially identical (27 degrees) for all ports except a greater range of movement for the XL Protype (35 degrees).
Conclusion: Few surgeons are using an UQ positioning or use techniques to improve attachment of the 4th arm. The greatest freedom may be obtained by implementing the FLA, but this necessitates production of a longer instrument.