Percutaneous Peripheral Nerve Stimulation of the Medial Branch Nerves for the Treatment of Chronic Axial Back Pain in Patients After Radiofrequency Ablation

Abstract

Objective: Lumbar radiofrequency ablation is a commonly used intervention for chronic back pain. However, the pain typically returns, and though retreatment may be successful, the procedure involves destruction of the medial branch nerves, which denervates the multifidus. Repeated procedures typically have diminishing returns, which can lead to opioid use, surgery, or implantation of permanent neuromodulation systems. The objective of this report is to demonstrate the potential use of percutaneous peripheral nerve stimulation (PNS) as a minimally invasive, nondestructive, motor-sparing alternative to repeat radiofrequency ablation and more invasive surgical procedures.

Design: Prospective, multicenter trial.

Methods: Individuals with a return of chronic axial pain after radiofrequency ablation underwent implantation of percutaneous PNS leads targeting the medial branch nerves. Stimulation was delivered for up to 60 days, after which the leads were removed. Participants were followed up to 5 months after the start of PNS. Outcomes included pain intensity, disability, and pain interference.

Results: Highly clinically significant (≥50%) reductions in average pain intensity were reported by a majority of participants (67%, n = 10/15) after 2 months with PNS, and a majority experienced clinically significant improvements in functional outcomes, as measured by disability (87%, n = 13/15) and pain interference (80%, n = 12/15). Five months after PNS, 93% (n = 14/15) reported clinically meaningful improvement in one or more outcome measures, and a majority experienced clinically meaningful improvements in all three outcomes (i.e., pain intensity, disability, and pain interference).

Conclusions: Percutaneous PNS has the potential to shift the pain management paradigm by providing an effective, nondestructive, motor-sparing neuromodulation treatment.

Trial registration: ClinicalTrials.gov NCT03179202.

Keywords: Chronic Pain; Low Back Pain; Percutaneous Peripheral Nerve Stimulation; Radiofrequency Ablation.

Figure 1.

PNS system and lead. Participants received PNS via a rechargeable, body-worn stimulator (A), controllable by each patient by using a wireless handheld remote (B), delivered to the lumbar medial branch nerves through fine-wire, open-coil leads (C).

Figure 2.

Anatomic target and lead placement approach for medial-branch PNS. PNS leads were placed bilaterally to target the medial branch of the dorsal ramus as it courses over the lamina toward the multifidus muscle, medial and inferior to the facet joint, at the spinal level in the center of the participant’s region of pain (A). An example of lead placement insertion is shown on fluoroscopic image with an anteroposterior (AP) view (B).

Figure 3.

Comparison of needle insertion approach for medial-branch PNS and medial-branch RFA. Although the same nerve (medial branch of the dorsal ramus) is targeted with PNS as for RFA, compared with the traditional target for RFA probe placement at the “eye of the Scottie Dog” (A), the PNS lead is placed medial and inferior to the facet joint (B). The design of the PNS lead avoids the requirement to place the stimulating electrode in intimate contact with the nerve via a parallel placement at the facet joint (as is done with RFA) (C) and instead enables the PNS electrode to be positioned remote to the nerve (approximately 0.5–1.0 cm away), targeting the medial branch nerve as it courses over the lamina (D). Furthermore, a single PNS lead is typically placed on each side of the back at the spinal level in the center of the region of pain to provide relief of pain across the entire region, whereas RFA requires ablation at multiple vertebral levels.

Figure 4.

Sustained reductions in average pain intensity among responders. (A) Time course of pain relief among participants who experienced ≥50% reduction in pain intensity after 2 months of PNS (n = 10/15). Participants experienced sustained reductions in average pain intensity at 5 months after start of treatment (3 months after lead removal). (B) Proportion of participants responding with ≥50% reduction in pain intensity with PNS after 2 months of PNS (67%, n = 10/15) and the proportion of responders who experienced sustained highly clinically significant reductions in pain intensity at 5 months (80%, n = 8/10).

Figure 5.

Proportion of participants with clinically meaningful improvements with PNS. A majority of participants (n = 15) experienced clinically significant improvements in pain intensity (BPI-5), disability (ODI), and/or pain interference (BPI-9). After 2 months of PNS, 87% of participants experienced ≥30% reduction in average pain intensity, 87% experienced ≥10-point reduction in disability, and 80% experienced ≥30% reduction in pain interference. Five months after the start of PNS treatment (3 months after PNS lead removal), the results were sustained across all three clinical outcomes.