Sacral nerve stimulation is a well-established third-line therapeutic option for refractory overactive bladder, non-obstructive chronic urinary retention, and fecal incontinence. Its clinical efficacy, however, remains highly variable and is contingent upon appropriate indication, meticulous patient selection, and surgical expertise. Optimal electrode placement is influenced by the chosen surgical technique; due to anatomical variability among patients, accurate marking of the skin entry point is critically important, despite the fact that intraoperative sensory and motor responses are routinely assessed to confirm lead positioning. The standardized technique proposed by Matzel et al. offers the most structured step-by-step approach currently available. Nevertheless, alternative anatomical landmarks for initial needle placement may facilitate access—particularly when the procedure is performed under local anesthesia.

We compare the electrode placement technique classically performed by the Department with the H-marking as described in the standardized technique. 

In both techniques, the patient is placed prone with pillows supporting the hips to achieve the correct angle to enter the foramen. The feet are left uncovered for monitoring of the responses. 

The ideal lead placement is located medial and superior within the S3 foramen, along the course of the S3 root. A combination of bony and x-ray landmarks allows for the most precise placement of the electrode, accounting for the physical variability of the patients.

The procedure starts with an anteroposterior fluoroscopic view.
In the technique performed by the Department, “mid-line/2cm”, a vertical line is drawn connecting the spinous processes. Then the sacroiliac joint is marked bilaterally and a horizontal line connecting these two points is drawn. In this horizontal line, considering the vertical line the center, 2cm to each side are marked, followed by other 2cm above this point, corresponding to the S3 foramen. The needle is then inserted with a 45º angle, confirming the correct positioning with a lateral fluoroscopic view.

In Matzel technique the medial edges of the foramina are marked with a vertical line on each side and then a horizontal line connecting the lower edges of the sacroiliac joint is drawn, forming an “H” figure. The intersecting points supposedly represent the upper medial part of the 3rd sacral foramen and the needle is supposed to entry a point somewhat cephalad to them. This is estimated using lateral radiograph, extending an imaginary line from this point in the angle of the intervertebral fusion plane of S2-S3.

We present the combination of both electrode placement techniques, demonstrating their similarities and differences, showcasing that the technique used by our department can be a reliable alternative to the “H” technique. It can be observed the different angulation used by them, being that a more laterally placement of the needle allows sometimes for a better entry in S3.

The “H” technique is an established procedure, with successful outcomes. However, the abstract indication that the needle must enter a point somewhat cephalad to the intersecting points of the “H” accounts for variability and a difficulty in its reproduction.  Additionally, the alternative ‘midline/2 cm lateral’ marking helps avoid inadvertent contact with the external surface of the sacrum—an important consideration when the procedure is performed under local anesthesia—while still allowing for accurate electrode placement.

Matzel, K. E., Chartier-Kastler, E., Knowles, C. H., Lehur, P. A., Munoz-Duyos, A., Ratto, C., Rydningen, M. B., Sørensen, M., van Kerrebroeck, P., & de Wachter, S. (n.d.). Sacral neuromodulation: Standardized electrode placement technique
Dawoud, C., Reissig, L., Müller, C., Jahl, M., Harpain, F., Capek, B., Weninger, W. J., & Riss, S. (2022). Comparison of surgical techniques for optimal lead placement in sacral neuromodulation: a cadaver study. Techniques in Coloproctology, 26(9), 707–712