Development of a CT-guided standard approach for tined lead implantation at the sacral nerve root S3 in minipigs for chronic neuromodulation

Purpose: The aim of this study was to develop a controlled approach for sacral neuromodulation (SNM) to improve both nerve targeting and tined lead placement, for which a new computed tomography (CT)-guided implantation technique was analyzed in minipigs. Materials and methods: This study included five female, adult Gottingen minipigs. In deep sedoanalgesia, the minipigs were placed in an extended prone position. Commercially available SNM materials were used (needle, introduction sheath, and quadripolar tined lead electrode). Gross anatomy was displayed by CT, and the nerves were bilaterally identified. The optimal angles to puncture the S3 foramen, the resulting access path, and the site for the skin incision were defined subsequently. The needle puncture and the tined lead placement were followed by successive CT scans/3D-reconstruction images. Once proper CT-guided placement of the needle and electrode was established, response to functional stimuli was intraoperatively checked to verify correct positioning. Results: Successful bilateral tined lead implantation was performed in four out of five minipigs. Implantation was different from the clinical situation because the puncture was done from the contralateral side at a 30 degrees angle to the midline and 60 degrees horizontal angle to ensure both passage through the foramen and nerve access. Surgery time was 50-150 minutes. Stimulation response comprised a twitch of the perianal musculature and tail rotation to the contralateral side. Conclusion: We have established a new, minimally invasive, highly standardized, CT-guided SNM electrode implantation technique. Functional outcomes are clearly defined and reproducible. All procedures can be performed without complications. Future chronic stimulation studies in minipigs can thereby be conducted using a controlled and highly standardized protocol.