Pudendal nerve neuromodulation is an effective treatment for pudendal neuralgia and pelvic pain. While current literature describes various techniques via the transgluteal or ischiorectal approach, all utilize fluoroscopy for localization, lack an anchoring ligament, or place the lead perpendicular to the targeted nerve. In this work, we aim to describe a novel technique for pudendal neuromodulation using anatomical landmarks for anchoring to the sacrotuberous ligament with a parallel placement via a transgluteal approach.

Sacral dissections on human cadavers preserved in formaldehyde were conducted by an expert anatomist to identify anatomical landmarks as visualized in fig 1.a. Systematic photographs of PA and lateral views were taken, and a single observer used ImageJ® software to measure anatomical distances and angles. Means were computed and data were tested for normal distribution using a Shapiro-Wilk test (SAS® software).
Average measurements were used to direct transgluteal needle placement for pudendal nerve neuromodulation. Point B was determined by measuring mean distance BC from tip of coccyx (C) in midline, and point A by measuring mean distance AB directly perpendicular to line BC. Point D, the ischial tuberosity, was identified via palpation and used to mark the line AD.
A 22g spinal needle entered the skin at point A while aiming along line AD (fig 1.b). The mean angle in which the needle runs parallel to the pudendal nerve in Alcock’s canal was determined with measurements taken from systematic photographs.

Seventy-two measurements from 48 cadavers (30 left, 48 right) were quantified and used to obtain the average distances of line BC (6.5±1.4 cm), line AB (4.8±0.90 cm), and the angle of ABP (36±9°), in addition to the distance from Point A to Point P (3.8±1.3 cm) and length of the STL (6.2±1.2 cm) (Fig 1.a). All measurements exhibited normal distribution. Average lengths of the obtained measurements were used to guide eight transgluteal markings (4 left, 4 right). Mean skin to needle angle was 31° (Fig 1.b, 1.c). In all 8 (100%) transgluteal needle placements, the needle traversed the sacrotuberous ligament and ran parallel to the pudendal nerve through Alcock’s canal (Fig 1.d).

Using the average measurements from 48 cadavers, 8 needles were successfully placed through the sacrotuberous ligament, anchoring ligament, and ran parallel to the pudendal nerve. This placement technique, with the lead parallel to the pudendal nerve will place more electrodes alongside the nerve. In addition, the lead will have an anchor, with placement through the sacrotuberous ligament, to minimize lead migration.

This novel technique utilizes anatomical landmarks to accurately place a lead through the sacrotuberous ligament and through Alcock’s canal. Further work is needed to determine clinically efficacy and adverse effects.

Continence 7S1 (2023) 100763
DOI: 10.1016/j.cont.2023.100763