Standardized fluoroscopy-guided implantation technique enables optimal electrode placement in sacral neuromodulation: a cadaver study

Abstract

Background: Sacral neuromodulation (SNM) is an established treatment option for patients with faecal incontinence. The location of the stimulating electrode is considered to be essential for treatment success. The purpose of this study was to evaluate the position of SNM electrodes after using a standardized fluoroscopy-guided implantation technique.

Methods: For this cadaver study, SNM electrodes were implanted bilaterally in 5 lower body specimens. The lower edge of the sacroiliac joint and the medial edge of the sacral foramina were marked using fluoroscopy to draw an 'H' with the crossing points identifying S3. After electrode placement the pelvis was dissected to describe the exact position of the SNM electrodes.

Results: The electrodes were inserted at an angle with a median degree measure of 60° (range 50-65°) to the skin, with a median distance of 9 mm (range 0-13 mm) from the S3 marking. All electrodes entered the third sacral foramen. The median distance of the electrodes to the sacral nerve was 0 mm (range 0-3 mm) for the most proximal, 0.5 mm (range 0-5 mm) for the second, 2.25 mm (range 0-11 mm) for the third and 1.75 mm (range 0-16 mm) for the most distant electrode. There was neither a significant difference in the proximity of the electrodes to the nerve between the right and left side (proximal to distal electrode: p = 0.18, p = 0.16, p = 0.07, p = 0.07) nor between male and female cadavers (p = 0.25, p = 0.21, p = 0.66, p = 0.66).

Conclusions: A standardized fluoroscopy-guided implantation technique enables a close contact between electrode and nerve. This can potentially result in an improved clinical outcome.

Keywords: Anatomical landmarks; Electrode localization; Faecal incontinence; Lead placement; Sacral neuromodulation; Treatment success.

Fig. 1

S3 marking a fluorescence-guided skin mark on the lower edge of the sacroiliac joint (1) and medial edge of the sacral foramina (2), b ‘H’ for the S3 marking

Fig. 2

a Electrode directly following the nerve cranially, b electrode perforating the nerve, c perforation of the presacral fascia (arrow – electrode, white line – sacral nerve S3)

Fig. 3

X-ray imaging, anterior–posterior view (1) right side with lateral flexure, (2) left side with straight electrode positioning