Fluoroscopy-Guided Electrode Placement for Porcine Sacral Neuromodulation Studies

Sacral neuromodulation is increasingly utilized clinically to treat conditions such as overactive bladder, urinary incontinence, and various pelvic pain disorders. Given their anatomical similarities to humans, porcine models have become prevalent in neuromodulation device research. This study introduces a validated fluoroscopy-guided implantation protocol for precise needle-based electrode placement onto porcine sacral nerves. "Blind" targeting through the posterior foramen results in an unreliable nerve-electrode interface. To address this challenge, we performed a detailed dissection and microCT characterization of pig sacral anatomy to accurately visualize the sacral nerves exiting the anterior foramen. We critically assessed the needle angles projecting through the S1, S2, and S3 foramina, with lateral fluoroscopic views confirming these angles. Delivery through the S2 and S3 foramen was deemed feasible, while S1 was deemed infeasible due to the relative positions of the posterior and anterior foramen. A step-by-step protocol for consistently achieving activation of the S2 and S3 sacral nerves was written and carried out in Yucatan minipigs (n=6). Specific fluoroscopic features corresponding to both posterior and anterior foramina were annotated in the images accompanying the procedure. We confirmed this percutaneous technique in vivo via recruitment of the bladder and external anal sphincter in response to electrical stimulation. Our results suggest that this method can significantly improve both the accuracy and precision of electrode placement onto porcine sacral nerves using minimally invasive techniques.Clinical Relevance-A standardized electrode insertion protocol was established to efficiently place electrodes onto the S2-S3 porcine sacral nerves to generate reliable bladder activation.