Sacral Nerve Stimulator Placement: A Novel Surgical Navigation Tool for...

Sacral neuromodulation is a therapy aimed at improving the quality of life of patients with constipation and fecal incontinence by delivering electrical impulses through a probe placed near the sacral nerve. This technology acts like a pacemaker to promote bowel and sphincter function. Placement in our institution happens in a hybrid operating room equipped with a CARM cone beam CT and a surgical navigation system. Using this technique enables us to offer this therapy to patients with dysplastic or malformed sacra whose anatomy would be otherwise prohibitive for traditional or purely fluoroscopic interventions. The patient is placed under general anesthesia and position prone with a pelvic roll for elevation and stabilization. A Foley catheter is inserted and grounding pads are applied. The surgical site is then prepped and draped in usual sterile fashion, with the drapes fastened under the bed to allow C arm rotation and easy access to the patient's feet for electrode testing. Anatomical landmarks for the intervention are identified and confirmed fluoroscopically. The horizontal axis is marked at the posterior inferior iliac spine in the cranial aspect of the sciatic notch. The vertical axis are traced overlying the medial aspect of the S3 neural foramina bilaterally, roughly 2 centimeters from the midline. Using the ruled needle provided. Conventional skin entry points are marked 2 centimeters cranially to these intersections. These would provide access to the estuary foramina at a 60 degree angle in the traditional approach without navigation. A cone beam CT run is acquired intraoperatively in a three dimensional model constructed for procedural guidance. The target anatomy is identified and a virtual path is created from the skin surface to the desired electrode location and evaluated in multiple views. The virtual tip location is confirmed with the patient's intraoperative scan. The planned needle entry site is then marked with real-time image guidance. In this case, it was identified around 1 centimeter caudle to the traditional markings. The needle is inserted under live fluoroscopy to maintain proper angulation. The needle tip location is then confirmed with multimodal navigation. The proximity to the sacral nerve is assessed through electrical stimulation. A bellows contraction identifies proper placement at the estuary foramen with confirmation by plantar flexion of the great toe. A guide wire is inserted and position is again confirmed with imaging. Insertion of the neuromodulation lead is then accomplished with standard Selinger technique using the dilator sheath provided. Location is once again reassessed before removing the guide wire and dilator. The marker should be visible halfway through the for foramen. A tied lead is then inserted under live visualization until the 3rd and 4th marks straddle the interior edge of the sacrum. This lead consists of 4 distal electrodes, times or barbs for stabilization, distance markers, and 4 proximal connectors. Lead positioning is confirmed with the bellows and toe response. The sheet is removed under live lead stabilization. Final placement is evaluated with navigation software, and a post-procedure X-ray is obtained. A small incision is made and a pocket developed over the contralateral gluteus to accommodate the remaining lead. This is where the generator is to be implanted after the initial test period. The pocket is irrigated and hemostasis is obtained with electrocautery. The lead is tunneled subcutaneously to the pocket with caution to prevent dislodgement. It is then attached to the temporary lead extension and screwed in tightly until clicks are heard. The plastic guard is slipped over the connection and secured tightly with non-absorbable sutures proximally and distally. A second subcutaneous tunnel is created to bring the lead extension across the midline to its temporary exit site through the skin. The pocket is closed in layers and all incisions are covered with surgical glue. The lead extension is connected to the external generator and secured in place with adequate padding. Over the next 2 to 4 weeks, the patient's bowel function is carefully recorded and compared to previous records. If a positive effect is demonstrated with neuromodulation, a permanent generator is implanted in a second stage. If unsuccessful, the lead can be removed without permanent damage to the nerve.