Anesthetic preference should be a balance of patient- and surgeon-specific needs, as the need for sedation is optional. After informed consent and discussion of risks vs. benefits, the patient is brought into the operative suite and placed in the prone position on the fluoroscopic table with or without a pillow for comfort. The patient should have standard ASA monitors with supplemental O2.

After appropriate sterile preparation with chlorhexidine solution, the patient, surgeon, and fluoroscopic unit should be draped in normal sterile fashion.

The measurements of the sacrum are performed from the aligned sacral promontory (SP), which needs to be approximately 30° cephalad to compensate for the lumbosacral angle. With a skin marker, draw a line over the sacral promontory and a line down the midline of the aligned sacrum. The superior border of the S3 approximates the inferior portion of the SI joint on fluoroscopy. (Fig. 1A.)

A Cephalad angulation required to align sacral promontory (SP) for measurements. B Measurements of sacrum with SP aligned. Blue squares represent two finder spinal needles placed lateral to S1 and S2 in coaxial view. C Fluoroscopic view with finder needles in place

The location of the sacral foramen is relatively stable among populations. Place 22-g finder needles lateral to the S1 and the S2 foramen. The lateral border of the S1 foramen is approximately 3.1 cm from the midline and 3 cm from the SP. The S2 foramen is approximately 5 cm from the SP and 1.5–2 cm from midline, but we will also place the second finder needle 3.5 cm from midline. These needles demarcate a safety boundary lateral to the sacral foramen, and their tips demarcate the osseous border of the posterior sacrum. [14] (Fig. 1B).

Take a caudal tilt with the fluoroscope 45° from the midline anterior-posterior position over the sacrum. Align the previously placed finder needles. Their aligned tips represent the posterior plate of the sacrum. The aligned shafts represent the medial border of our target needle trajectory. (Fig. 2A and B).

A A caudal tilt is taken until the spinal needles align, usually with a range of 30–50°. B Fluoroscopic view with finder needles aligned. C The RF needle entering in coaxial view lateral to the aligned finder needle points

Advance the curved tip RF cannula just lateral to the spinal needle tips in the coaxial view. (Fig. 2A). Use the curved tip of the needle to steer and stay as close to the posterior sacrum as possible in the lateral position. See Fig. 3B. The final needle position should be close to the rostral border of the sacrum in the 30° cephalad angulation view (Fig. 3C).

A Final RF needle position in the caudad tilt view. B Lateral view with the RF needle advanced to the SP. C Final position of the RF cannula in the AP view

After confirmation on AP and lateral views until the tip of the RF needle is in the dorsal ramus of L5, motor stimulation should be performed before radiofrequency lesion.

If using a 15-mm active tip needle, after RF is completed, retract the needle approximately 2 cm and repeat lesioning for a total of four lesions. If 10-mm active tip needles are used, a total of six lesions are required (Fig. 4).

Position of the needle in the posterior portion of the sacrum, lateral to the sacral foramens, retracting the needle to perform a strip lesion

Limitations: This technique was conceptualized as an alternative, cost-effective option for the treatment of chronic sacroiliac joint dysfunction. While preliminary results are promising, further research is required to demonstrate the effectiveness of this technique compared to existing techniques and technology. Additionally, this single-needle and electrode technique does not allow for bipolar radiofrequency. If bipolar is recommended, it will require an additional cannula placed adjacent to the initial cannula.