Six-Month Follow-up of a Trial of Spinal Cord Burst Stimulation vs Placebo Stimulation and Disability in Patients With Chronic Radicular Pain After Lumbar Spine Surgery

Abstract

This follow-up study examines back pain–related disability at 6 months following a randomized trial of spinal cord burst stimulation for chronic radicular pain after lumbar spine surgery.

Although the use of spinal cord stimulation for chronic pain has increased, high-quality evidence supporting its efficacy is limited.^1,2 Spinal cord burst stimulation involves delivery of intermittent “trains” of closely spaced, high-frequency electrical stimuli to the spinal cord.³ A recent randomized, placebo-controlled, crossover trial found that among patients with chronic radicular pain after lumbar spine surgery, spinal cord burst stimulation was not superior to placebo for improving pain-related disability.⁴ The main limitation of the trial was that blinding of treatment allocation prohibited repeated fine-tuning of stimulation parameters (ie, amplitude, pulse width, and frequency) in open dialogue with patients and the use of paresthesia-inducing tonic stimulation.⁵ This post hoc follow-up study investigated back pain–related disability at 6 months following completion of the final randomization period when patients were unblinded and provided with handheld spinal cord stimulation programmers allowing changes to stimulation settings and switching between burst and tonic stimulation.

Methods

The Regional Committee for Medical Research Ethics approved the follow-up study, and all participants provided written informed consent. The protocol is available in Supplement 1. The trial was conducted at St Olavs Hospital, Trondheim, Norway, from September 2018 through April 2021. The date of final follow-up was December 20, 2022. The trial included patients aged 18 years or older who had undergone surgery for degenerative lumbar spine disease and experienced postoperative chronic radicular pain. Following implantation of the stimulator (Precision Novi, Boston Scientific Inc), patients underwent four 3-month periods with either burst stimulation (2 periods) or placebo (ie, no stimulation; 2 periods) in a randomized order. After the final randomization period, all trial participants received a programmer that allowed adjustment of stimulation amplitude and switching between burst and tonic stimulation and had follow-up appointments after 3 and 6 months.

The primary outcome was difference in score change from trial enrollment in the self-reported Oswestry Disability Index (ODI) version 2.0 between 6-month posttrial follow-up and placebo stimulation during the trial. The ODI is scored using a scale from 0 to 100 (minimum clinically important change, 10 points), with increasing values reflecting more disability. The primary statistical analyses included trial participants who had 1 or more ODI measurements following randomization. Sensitivity analyses were performed in a complete case set, which included patients who had ODI measurements at all time points during the trial and posttrial follow-up. Linear mixed models were used for statistical comparisons. Statistical tests for the primary outcome were performed at the 2-sided significance level of .05. Statistical analyses were performed using R version 3.6.3 (R Foundation for Statistical Computing).

Results

Among the 50 patients included in the original trial, 47 had 1 or more ODI measurements following randomization. In total, 34 patients completed posttrial follow-up. The complete case set consisted of 30 patients. At trial enrollment, the mean ODI score was 44.7 (SD, 11.3) points. The mean ODI score at 6-month posttrial follow-up was 34.7 points (mean change, −10.0 [95% CI, −14.5 to −5.5]) compared with 35.4 points (mean change, −9.3 [95% CI, −12.7 to −5.9]) during placebo stimulation in the trial, resulting in a mean difference of change in ODI of −0.7 points (95% CI, −4.5 to 3.2; P = .73) (Table). Sensitivity analyses showed no significant between-group differences for ODI change. Following 6-month follow-up, 4 patients had their stimulator removed due to no perceived effect and discomfort from the implanted system, and 1 patient underwent surgical revision due to epidural lead migration.

Table. Six-Month Follow-up of a Trial of Spinal Cord Burst Stimulation vs Placebo Stimulation on Self-reported Back Pain–Related Disability^a.

Outcome	Trial enrollment	Placebo stimulation including 89 stimulation periods	Posttrial follow-up including 34 observations	Difference between posttrial follow-up and placebo stimulation
				Difference (95% CI)	P value
Oswestry Disability Index score (95% CI)
Full analysis set (n = 47)b	44.7 (41.4-47.9)	35.4 (31.4-39.4)	34.7 (29.5-39.9)	−0.7 (−4.5 to 3.2)	.73
Complete case set (n = 30)c	44.3 (40.5-48.1)	35.5 (30.7-40.3)	34.2 (28.3-40.2)	−1.3 (−5.6 to 3.0)	.55

^a All patients were provided with spinal cord stimulator programmers when the trial ended.

^b Patients who had 1 or more Oswestry Disability Index measurements following randomization.

^c Patients with Oswestry Disability Index measurements at all points during the trial and posttrial follow-up.

Discussion

In this 6-month follow-up of a randomized trial on spinal cord burst stimulation for chronic radicular pain after lumbar spine surgery, the improvement in pain-related disability at posttrial follow-up was not significantly different from placebo stimulation. This follow-up study does not support the use of spinal cord stimulation to manage chronic radicular pain after spine surgery outside clinical trials. Limitations of the posttrial follow-up study included loss to follow-up, lack of details concerning the proportion of time spent using burst or tonic stimulation, and no self-reported outcome measures beyond pain-related disability.

Section Editors: Jody W. Zylke, MD, Deputy Editor; Kristin Walter, MD, Senior Editor.

Supplement 1.

Trial Protocol

Supplement 2.

Data Sharing Statement