Article In Brief
Despite their increasing use for chronic pain, spinal cord stimulators have not proven to be more effective than conventional medical management. In fact, a new analysis finds, they are costly and associated with adverse events.
The use of spinal cord stimulators is not associated with reductions in opioid use or nonpharmacologic pain interventions, including epidural and facet corticosteroid injections, radiofrequency ablation, and spine surgery, a new study reveals. Nor is it more effective than conventional medical management of chronic pain.
Published online Nov. 28 in JAMA Neurology, the large study comparing spinal cord stimulation with conventional medical management not only suggests a lack of clinical benefit for spinal cord stimulations but also reports that the latter is associated with higher costs and potential for harm for some patients.
“There may be opportunities to redeploy the high—and increasing—use and spending associated with spinal cord stimulators toward more evidence-based interventions for chronic pain relief,” the study's authors wrote.
Spinal cord stimulators, which have been used increasingly in recent years, are neuromodulation devices implanted in the epidural space to manage chronic pain that fails to respond to conventional treatment. About 50,000 are implanted annually in the United States at a cost of roughly $3.5 billion. Some experts have recommended more widespread use of these devices to lower the risks of medications, including opioids and gabapentinoids.
Despite their growing use, the study's authors state the evidence supporting spinal cord stimulators over usual care has limitations. They contend that the US Food and Drug Administration (FDA) authorized most stimulators without clinical data, and industry funds an estimated 85 percent of large studies (involving more than 100 patients) using these stimulators. Typically, independent evaluations have been small, single-center, and nonrandomized.
A recent Cochrane systematic review of randomized trials of these devices uncovered only one study (involving 44 patients) examining pain intensity at one year or longer follow-up. While some studies found benefit in pain relief at six months from spinal cord stimulators compared with conventional medical management, benefits are often depleted after 12 to 24 months. In addition, the authors pointed out that the comparator group in many trials of the devices did not sufficiently mask a placebo effect. When a placebo control is used, treatment effects are more modest.
In September 2020, an FDA letter addressed to health care professionals noted that more than 107,000 medical device adverse-event reports related to spinal cord stimulators had been filed between July 2016 and July 2020. The incidents included patient injury, device malfunction, and 497 deaths. Also, among 4,000 types of medical devices tracked by the FDA, spinal cord simulators had the third-highest number of adverse events.
“Given the limitations in available data, there is a need for data in a larger, contemporary patient cohort to compare the long-term risks, benefits, and cost-effectiveness of spinal cord stimulators with conventional medical management,” the authors wrote. “Accordingly, we compared the long-term clinical and health care utilization outcomes among patients treated with permanent spinal cord stimulators compared with conventional medical management.”
Sanket Dhruva, MD, MHS, the study's lead author, told Neurology Today that the findings are significant. “Our study is as rigorous of a real-world evaluation of spinal cord stimulators as is possible,” said Dr. Dhruva, assistant professor of medicine at the University of California, San Francisco, School of Medicine.
“Our findings provide important information to help inform clinicians and policymakers about the need for greater use of evidence-based therapies for pain relief,” he added.
One of the study's major strengths is the two-year follow-up of a large cohort of patients using spinal cord stimulators compared to conventional medical therapy. “In addition to the clinical outcomes, we were also able to examine costs of care,” Dr. Dhruva said, noting that the devices “add significant cost and are associated with an overall high rate of complications.”
Investigators performed a 1:5 propensity-matched retrospective comparative effectiveness research analysis of insured individuals from April 1, 2016, to Aug. 31, 2018. They relied on administrative claims data, including longitudinal medical and pharmacy claims, from US commercial and Medicare Advantage enrollees 18 years or older in the Optum Labs Data Warehouse.
Included in this study were patients with incident diagnosis codes for failed back surgery syndrome, complex regional pain syndrome, chronic pain syndrome, and other chronic postsurgical back and extremity pain. The data analysis was conducted from Feb. 1, 2021, to Aug. 31, 2022.
Researchers used surrogate measures for primary chronic pain treatment modalities, including pharmacologic and nonpharmacologic pain interventions—epidural and facet corticosteroid injections, radiofrequency ablation, and spine surgery—as well as total costs.
The propensity-matched population consisted of 7,560 patients with a mean age of 63.5 years. There were 3,080 males (40.7 percent) and 4,480 females (59.3 percent).
Among matched patients, during the first 12 months, patients managed with spinal cord stimulators had higher odds of chronic opioid use (with an adjusted odds ratio [aOR] of 1.14) compared with patients receiving conventional medication management. They had lower odds of epidural and facet corticosteroid injections (aOR, 0.44), radiofrequency ablation (aOR, 0.57), and spine surgery (aOR, 0.72).
During months 13 to 24, there was no significant difference better spinal cord stimulators and conventional medical managements regarding the likelihood of chronic opioid use, epidural and facet corticosteroid injections, radiofrequency ablation, or spine surgery.
Overall, 226 of 1,260 patients (17.9 percent) treated with spinal cord stimulators experienced device-related complications within two years, and 279 of 1,260 patients (22.1 percent) underwent device revisions and/or removals, which were not always because of complications. In the first year, the total cost of care was $39,000 higher with spinal cord stimulators than conventional medications. Costs were similar between the two groups in the second year.
“The methods are rigorous, the sample size is large, and it reflects real-world practice,” said Brian Callaghan, MD, MS, FAAN, associate professor of neurology at the University of Michigan Medical School and the lead author on the AAN's recently published guidelines on treatments for painful diabetic neuropathy.
Dr. Callaghan commended the authors for correctly pointing out many of the limitations present in previous studies. “The current study looks at changes in opioid use and other interventions for pain in those with spinal cord stimulators compared to those that don't,” he said, adding that it “should limit enthusiasm for spinal cord stimulators in most chronic pain conditions.”
“The current process leads to frequent use of medical devices without strong evidence to support their use despite the potential for device-related complications and high costs.”—DR. BRIAN CALLAGHAN
“Our study is as rigorous of a real-world evaluation of spinal cord stimulators as is possible. Our findings provide important information to help inform clinicians and policymakers about the need for greater use of evidence-based therapies for pain relief.”—DR. SANKET DHRUVA
Hopefully, Dr. Callaghan noted, the study also will prompt higher-quality randomized trials of spinal cord stimulators with sham controls to determine which populations truly benefit.
He lamented that the US Food and Drug Administration “does not hold devices up to the same rigor as it does for oral medications, which leads to frequent use of spinal cord stimulators without the data to support this use.”
Consequently, “the current process leads to frequent use of medical devices without strong evidence to support their use despite the potential for device-related complications and high costs.”
Dr. Callaghan does not recommend spinal cord stimulators for patients with painful diabetic neuropathy. A recent uncontrolled study showed benefit in this population, but an uncontrolled pain study did not offer much information.
“We need to hold the studies to a higher standard,” he said.
The main limitation of this research is the potential for residual confounding, given that this is an observational study and not a randomized, controlled trial.
“Patients receiving spinal cord stimulators are likely different than those not receiving spinal cord stimulators in ways that we cannot measure,” Dr. Callaghan said.
Despite the large sample size, a retrospective study using claims data has serious limitations, said Nathaniel M. Schuster, MD, a pain and headache neurologist who is associate clinic director and associate professor at the University of California, San Diego Health's Center for Pain Medicine.
The use of claims data makes it impossible to adequately find a matching group of patients, Dr. Schuster said, adding that investigators would need to conduct a randomized, controlled trial to achieve that.
“Not all patients with failed back surgery syndrome warrant a spinal cord stimulator; the patients receiving spinal cord stimulators are typically going to have more severe pain and worse disability than those not receiving spinal cord stimulators,” he said. “This study was not able to match patients based on level of pain or disability, only by diagnosis.”
It is unlikely that patients prescribed conventional medical management were truly comparable to the patients receiving spinal cord stimulators, Dr. Schuster said. Individuals considered for these devices are generally the most refractory patients and typically have already failed extensive conventional medical management. The most common indication for a stimulator is failed back surgery syndrome (also called post-laminectomy pain syndrome or persistent spinal pain syndrome), with refractory lower back and leg pain after one or more spine surgeries, Dr. Schuster said.
Dr. Schuster added that many of the patients considering spinal cord stimulators are deciding between that option and having yet another spine surgery, which is very expensive, often riskier, and leads to a longer and more difficult recovery than implantation of a stimulator.
“At least one prior randomized, controlled trial has found spinal cord stimulators to outperform reoperation,” he said.
“They are not typically trying to decide between a spinal cord stimulator and oral medications or interventional pain procedures, such as epidural and facet corticosteroid injections or radiofrequency ablations, as they have already tried and failed those treatments, if a spinal cord stimulator is being considered,” he said.
Dr. Schuster also noted that a potential bias exists in this study given the involvement of Optum, a subsidiary of UnitedHealth.
“Research funded by device manufacturers is at risk of pro-device bias, but there is also concern for anti-device bias in such a study where most of the authors are employees of a payor,” he said.
In addition, the study only included two years of follow-up. Prior studies have shown that spinal cord stimulators become cost-effective at two and a half or three years.
When asked if the findings apply to clinical practice, Dr. Schuster said new devices were introduced around the time of the data analyzed in the study, with different devices offering different waveforms. This may have resulted in more revisions to swap one device with another that had different waveforms. Now, all devices offer multiple waveforms, so waveform changes can be made by reprogramming rather than via device removal and implantation.
“Also, dorsal root ganglion stimulation was introduced during that time, which has a higher lead migration and reoperation rate,” Dr. Schuster said. “But we don't know how many of the revisions were for dorsal root ganglion stimulation versus dorsal column stimulation (the standard spinal cord stimulator product).”
Among this new wave of devices, Nevro's paresthesia-free, high-frequency 10kHz spinal cord stimulator only provided a single waveform, but it was one that showed particularly impressive results in a randomized, controlled trial, Dr. Schuster said. Then Abbott's dorsal root ganglion stimulator arrived on the market.
“Some of the reoperations were likely related to patients changing either only the implantable pulse generator or the entire spinal cord stimulator system to switch from the traditional, tonic stimulation to the new Nevro system or vice versa,” he said.
Ultimately, however, Dr. Schuster added that “this study is a reminder to providers and patients alike that spinal cord stimulation is not a panacea and that careful patient selection is of paramount importance.”