Optimizing electrode implantation in sacral nerve stimulation - an anatomical cadaver study controlled by a laparoscopic camera

Sacral nerve stimulation is the therapy of choice in patients with neurogenic faecal and urine incontinence, constipation and some pelvic pain syndromes. The aim of this study is to determine the best insertion angles of the electrode under laparoscopic visualization of the sacral nerves. Five fresh cadaver pelvises were dissected through an anterior approach of the presacral space, exposing the ventral sacral roots. Needles and electrodes were inserted into the S3 foramen. Both right and left sides were used, with the traditional percutaneous procedure. The validation was done by a laparoscopic camera controlling the position of the needle and electrode on the nerve. The angles were assessed with a goniometer and were confirmed in two living patients. The mean angle of insertion in the sagittal plane was 62.9 +/- 3 degrees (range, 59-70). In the axial plane, the mean angle for the left side was 91.7 +/- 13.5 degrees (range, 80-110) and 83.2 +/-.7 degrees for the right side (range, 75-95). These angles resulted in the optimal placement of the leads along the S3 sacral root, in all these cases. This study allows direct visualization during the placement of the needle and electrode, thus permitting accurate calculations of the best angle of approach during the surgical procedure in sacral nerve stimulation. These objective findings attempt to standardize this technique, which is often performed with the aid of intra-operative fluoroscopy but still leaving a lot to chance. These insertion angles should help to find more consistent and reproducible results and thus improved outcome in patients.