Application of a newly designed microfork probe for robotic-guided pelvic intraoperative neuromapping.

INTRODUCTION: Robotic-assisted total mesorectal excision (TME) with pelvic intraoperative neuromapping was recently accomplished. However, neuromapping is conventionally conducted by a hand-guided laparoscopic probe. We introduce a prototype microfork probe to make robotic-guided neuromapping feasible. Experiments and Technical Setup: Two porcine experiments with nerve-sparing TME surgery were performed. A newly designed prototype bipolar microfork probe was inserted intraabdominally and guided with the robotic forceps. Intermittent neuromapping was then conducted and neuromonitoring data integrated in the surgeon console viewer.
CONCLUSION: Robotic-guided neuromapping is shown to be feasible and fully controllable from the surgeon console.

INTRODUCTION

Robotic surgical systems are becoming increasingly popular in minimal-invasive colorectal surgery not only due to three-dimensional views and improved instrument technique but also especially for narrow and deep spaces such as the pelvis. A combination of the nerve-sparing principle with the total mesorectal excision (TME) surgery for the preservation of anorectal, urinary and sexual function is challenging. Suggestive evaluation of pelvic autonomic nerve preservation in conventional laparoscopic and robotic-assisted laparoscopic TME[1] may be objectified with intraoperative neuromapping. Robotic-assisted TME with pelvic intraoperative neuromapping has been shown to be feasible.[2] Conventionally, neuromapping is conducted by a hand-guided bipolar microfork probe. However, execution from the surgeon console is technically restricted due to inability to visualise neuromonitoring signals in a real-time manner by the operating surgeon and challenges in communicating the nerve location from operating surgeon, who did the dissection, to bedside assistant, who has control of the long-shaft laparoscopic neurostimulator. A prototype microfork probe was designed to overcome these technical difficulties and return autonomy to the surgeon at the console during neuromonitoring.

TECHNICAL SPECIFICATIONS

The newly designed prototype robotic stimulation probe (inomed Medizintechnik GmbH, Emmendingen, Germany) is short shafted with an overall length of 33 mm for intracorporeal manoeuvrability. It consists of two stainless wires having a diameter of 650 μm each with a 2 mm sphere welded to their tip. The wires are injection moulded to be accurately aligned to each other for a length of 15 mm. The uninsulated front part has a length of 7 mm, and the electrical contacts are 3 mm apart. The teflon-coated cables with a length of 3 m finish in 1.5 mm touch-proof connectors.

PROOF OF CONCEPT

Two porcine experiments were performed following approval by the local Animal Research Committee (Protocol Number: 2016-075-01B). In both cases, nerve-sparing TME surgery was conducted. Intermittent neuromapping was performed based on electric stimulation of pelvic splanchnic nerves and inferior hypogastric plexus under simultaneous electromyography (EMG) of the internal anal sphincter and manometry of the urinary bladder. The prototype bipolar microfork probe was tested for robotic-guided neuromapping. The probe was controlled and directed by the robotic forceps, and both pelvic side walls were easily accessible with the robotic surgical system (da Vinci Si, Intuitive Surgical, Sunnyvale, CA, USA). After connection of the neuromonitoring device (ISIS Xpress, inomed Medizintechnik GmbH, Emmendingen, Germany) with the robotic platform through digital visual interface cable and activation of the multi-image configuration (TilePro, Intuitive Surgical, Sunnyvale, CA, USA), neuromonitoring data were integrated in the surgeon console viewer [Figure 1].

Figure 1

(a) Short-shafted prototype bipolar microfork probe during intraoperative neuromapping on the right pelvic side under robotic forceps guidance. (b) Multi-image view with intracorporeal view (upper image) and neuromonitoring signals (lower image)

With adoption of the new system, the console surgeon is able to guide and direct the microfork probe using robotic forceps and evaluate the EMG and manometry signals under the console surgeon viewer in a real-time manner. This way neuromapping could be conducted and validated from the surgeon console without the need of constant bedside assistance.

CONCLUSION

We report the technical feasibility of robotic-guided neuromapping fully controllable from the surgeon console by introduction of a new prototype bipolar microfork probe in combination with multi-image view.

Financial support and sponsorship

The project was funded by the Federal Ministry of Education and Research (BMBF, grant no. 16SV7638) and American Society of Colon and Rectal Surgeons, Robotic Research Grant (grant no. RRTG-002).

Conflicts of interest

There are no conflicts of interest.