Observations on a Study of Spinal Cord Stimulation for Pain
This post will examine the study entitled, “10kHz spinal cord stimulation: a retrospective analysis of real-world data from a community-based, interdisciplinary pain facility” and published 20 November 2018.
This link is to the paper as it appears on the Dovepress website:
Since I could not view the tables by clicking the links when I viewed the paper on the above website, I also viewed the paper on the following NCBI webpage, where I was able to access the tables:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6251433/
OverviewThe introduction describes the study as a retrospective investigation of treatment outcome data. The subjects had chronic low back pain, with or without leg pain, and were already patients at an interdisciplinary pain clinic. The main goal was to study the effect of a 10kHz Spinal Cord Stimulation device combined with conventional medical care on analgesia and perceived disability. The study ran from December 1, 2014 to Dec. 31, 2017.
Report’s Description of the Objectives, Results & ConclusionsThe study objectives were to compare the clinical condition and health usage of subjects, divided into 2 groups. One received a Spinal Cord Stimulator device plus continuing their conventional medical management (SCS+CMM group), the other group just continued their conventional medical management (CMM group).
The results are described as the study supporting the effectiveness of SCS for reducing pain, with both groups having reduced opioids use and other medical interventions. The SCS+CMM group had higher reductions in opioids and the CMM group had higher reductions in interventional treatments.
Study Subjects and How They Were Chosen The 96 study subjects had been patients at a pain clinic that uses an interdisciplinary team approach. The SCS+CMM group had 32 subjects, and the CMM group had 64. “Data were extracted from medical records, including pain severity, prescribed opioid dose in morphine milligram equivalents, patient perception of disability, and volume of interventional pain procedures and total office visits to the pain center.”
The participants were not randomized. First, 32 subjects were chosen to receive the SCS and conventional medical care. Then a group of 64 patients with chronic lower back pain were selected from 274 candidates. The 64 in the CMM group were matched to the 32 in the SCS+CMM group based on age, gender, initial pain severity, number of office visits and interventional procedures over the first 12 months, and initial opioid use. The two groups were also similar in tobacco use, marital status and employment status.
Members in the SCS+CMM group were evaluated by an interventional anesthesiologist and a pain psychologist. Some were administered self-reporting screening measures. Not all measures were administered to all subjects. An outpatient psychiatrist and referring surgeon were consulted to aid evaluation of the subjects.
Initially, the subjects chosen for the SCS+CMM group had a 7-10 day trial of a temporary SCS implant. There was a collaborative meeting of subject, treating pain physician, nurse practitioner and psychologist. Functional goals and opioid reduction targets were set, and any barriers to adherence or success were discussed.
At the end of the 7-10 day trial, pain relief and functional improvement were assessed by the pain physician, and those meeting a criteria of at least 50% reduction in pain and “marked improvement in function” proceeded to permanent implantation. Post-implant visits were scheduled every 6 months to evaluate progress with the SCS device, administer psychosocial and functional screening, ensure complaint use of the devise, assess self-reports of pain and review functional goals.
Measuring Opioid Dose, Office Visits, Interventional ProceduresFor the SCS+CMM group, daily opioid dose in morphine milligram equivalent (MME) was documented for 3 points: 12 months prior to implant, day of implant, 12 months after implant. For the CMM group, the 3 points were 12 months prior to the start of the study, at the start, and 12 months after the start. Change in dose was calculated for SCS+CMM group by subtracting the dose 12 months after implant from the dose at day of implant. The CMM subjects’ total was the dose at 24 months subtracted from the dose at 12 months.
The researchers distinguished between two types of appointments, those that they counted as part of the study results, and those not counted towards the study results. Those counted were categorized as office visits and interventional procedures. Office visits included evaluations, follow up appointments at the pain center, minor office procedures such as trigger point or bursa injections, behavioral medicine, and physical therapy. Interventional procedures included epidural injections, facet joint injections, radiofrequency ablations and major joint injections. The visits that were excluded from study results included routine medication follow up and visits related to the SCS device evaluation, installation follow up, and device programming.
For the SCS+CMM group, office visits and interventional procedures counted the total office visits and procedures for the 12 months prior to and the 12 months after implant. The CMM group’s visits and procedures were counted for the first 12 months prior to the study’s start, then the 12 months following the start of the study.
What Was MeasuredSubjects were administered the following self-reporting instruments:
Both the SCS+CMM group and the CMM group were administered the Functional Pain Scale (FPS), a scale from 0 = no pain to 10 = worst pain, including a functional description, such as 3 = affecting ability to perform current activity, 7 = can’t move painful area, talking and concentrating difficult.
The SCS+CMM group only was given the Numeric Rating Scale (NRS) at day of implant and 12 months after. (Note: this report says the NRS “was not developed or validated as a measure of pain. Test-retest reliability has been found to be only fair, although responsiveness in treated patients with chronic pain was determined to be adequate. A more recent study of low back and radiating lower extremity patients failed to demonstrate its construct validity. However, it remains the standard measure in pain outcome studies, including those evaluating SCS.”)
At time of implantation, SCS+CMM subjects were administered 3 self-report instruments: the Pain Catastrophizing Scale, in which the patient rates a statement from 0 = not at all to 4 = all the time; and the Patient Health Questionnaire (PHQ)-9 a 9-item measure of severity of depression, in which subjects rated the frequency of each item over the past 2 weeks, from 0 = not at all to 3 = nearly every day; the Generalized Anxiety Disorder-7 reporting frequency of items over the past two weeks 0-3, same as the PHQ-9.
When evaluated for inclusion in the SCS+CMM group, and again at follow up after implant, the SCS+CMM group were administered the WHO Disability Assessment Schedule 2.0 (WHODAS 2.0), rating the difficulty of various tasks over previous 30 days from “none”, to “cannot do.”
The Roland-Morris Disability Questionnaire (RMDQ) rates 24 items on the current day as True/Not True. Some SCS+CMM subjects may have completed this when evaluated for SCS or post-implant, and/or as part of routine opioid follow up. CMM subjects receiving opioids were administered the RMDQ-m during routine care. Scores for both groups were obtained at month 12 and 24.
At the end of the study, the SCS+CMM groups’ reduction in office visits was not statistically significant, and the CMM groups’ was. The researchers say the reduction in CMM subjects’ visits may be related to the difference in sample size.
Both groups had similar amounts of interventional procedures during months 1-12, and significant reductions in months 12-24. The SCS+CMM reduction was 75%, and the CMM was 34.6%.
Discussion Section of the Study ReportThe opioid doses were reported to have been reduced by 71.4% for the SCS+CMM group (23 people), which included one subject who tapered from 120 MME to zero. One SCS+CMM patient increased MME after implant, 8 remained the same. In other words, of the 32 SCS subjects, 31 were still taking opiates one year after the implant. The CMM group included 12 subjects (31.6%) whose doses were higher at the end of the study, 18 whose doses were lower.
The authors say the statistically significant difference in opioid reduction in the SCS+CMM is important because of increased emphasis of reducing US opioid use, as reflected in the controversial CDC guidelines. The researchers suggest that the CMM group’s opioid reductions being less than those of the SCS+CMM group could mean the SCS has a beneficial effect beyond the results of the model of care (which includes of visits with multiple professionals including pain physician, PA, surgeon, psychologist, psychiatrist, PT).
Both the SCS+CMM and the CMM groups had reduction in disability measurements on the RMDQ-m. The researchers are amenable to the idea that the improvements of both groups’ self-reports of physical disability may be due to the interdisciplinary approach to chronic pain treatment.
While subjects in both groups self-reported decrease in disability, the WHODAS 2.0 scores of both groups showed no change. WHODAS 2.0 measures 6 domains: cognition, mobility, self-care, getting along with others, life activities (home, work, school) and participation in community activities.
The researchers cite the following limitations to the study: subjects in retrospective cohort studies may differ in measured and unmeasured baseline characteristics; subjective patient-reported measures are susceptible to biases including social desirability, secondary gain and inaccurate memory leading to over-/under-estimating of true functional levels; the sample size was small (though within the range of failed back surgery studies); follow up was only collected for 12 months; the integrated biopsychosocial model underscored the goals of improved function and opioid reductions. The researchers admit “….it is possible that this model of care had an impact on our results.”
The researchers count the following as strengths of their study: “real-world retrospective data that reflects the clinical practice of a community-based interdisciplinary team” and “The retrospective nature of the study reflects clinical decisions made in usual daily medical care” and ”the absence of specific research objectives at the time of decision-making.”
The researchers say a prospective study comparing SCS+CMM with CMM could not be blinded.
Researchers’ ConclusionsThe researchers see a potential for integrating 10 kHz SCS in interdisciplinary pain management. They see the decrease in total opioid use of the 32 member SCS+CMM group as consistent with current views on mitigating risks of controlled substances, and see their results as demonstrating that SCS is associated with reduced pain in the lower back and lower extremities, and self-reported disability. They see this study as proof-of-concept for SCS when integrated in an interdisciplinary treatment plan.
My ResponseThere are a few points on which I can agree with the authors of this report. A retrospective investigation is far from ideal. The 12 months follow up is awfully short. The biopsychosocial model certainly could have influenced this study in a number of ways that would influence results. I agree that the sample size was small, but disagree that the existence of other equally small studies makes this less of a flaw.
I also agree with the researchers’ observation that the US currently has a strong focus with reducing risks of controlled substances. I think the intensity of the focus, and the conflation of legitimate prescribed use with illicit consumption is a major factor in how both opioids and alternatives are viewed by the government and the public.
The researchers portray their study’s reflection of real-world medical decision-making as a positive aspect of their study. This is actually a major flaw – if real world medical business-as-usual gave us reliable scientific data, there would be no need for randomized, double blind, placebo-controlled studies.
One aspect of the study that is deeply concerning – in fact, a scientific fatal flaw – is that it was not only not randomized, but the subjects in the two groups were chosen for different criteria. The SCS+CMM group were chosen for their goal of reducing opioids, while the CMM subjects were chosen for similarity to the demographic characteristics of the SCS+CMM group.
Another serious weakness of this investigation, on a level with the two subject groups being chosen using different criteria, is that the researchers report “….the absence of research objectives at the time of decision-making.” The investigation did not start out with questions to answer, but with a goal of reducing the dose of opioid medications among some patients at a pain management facility. Only later did the researchers shape into this report results of self-reporting instruments administered to some of the subjects, the total medical interventions received by subjects, and the comparison of doses at 2 of 3 instances when the dosage in MME were collected. It’s the scientific equivalent of shooting at the side of a barn, then drawing a target around the bullet holes.
Compared to the scant objective data (basically the dosages of opioids at 3 points in a 2-year period, and the numbers of interventional procedures received by the subjects) there was a high proportion of self-reporting instruments, including the NRS, which the researchers admit wasn’t developed for pain and has reliability that is only “fair.”
The one self-reporting instrument used that was somewhat less subjective in the questions it asks, is the WHODAS 2.0. This instrument touches on cognition, mobility, self-care, getting along with others, life activity and participation in community activities. That the WHODAS 2.0 showed no changes in either group suggests that there might be less to this investigation than the authors would like to believe.
Self-reporting instruments aren’t the only option for measuring pain. There are instruments for use with pre-verbal infants, demented elderly, and intubated patients, which rely on indicators such as facial expression, body movement, changes in sleep and appetite, and even tears. Adapting such instruments to verbal subjects may have been beyond the expertise of the researchers in this study, which is fair enough. But studying the effects of a medical intervention would only be strengthened by collecting as much objective data as possible, instead of relying on self-reporting instruments that were administered to only some of the participants.
Some subjects engaged in physical therapy, which could have offered opportunities to measure progress in exercises performed, increases in stamina or range of motion at points during the study. Even equipping subjects with pedometers could have provided some objective data about the real world effects of SCS+CMM compared to the CMM group.
It’s puzzling that some of the objective data collected was not used in calculating the changing opioid dosages. The dose in MME was collected for the SCS+CMM group at 12 months prior to implant, at implant, and 12 months after implant, and for the CMM group, 12 months before the study, at the start of study, and 12 months after the start. But when reporting on the change in MME of subjects in the two groups, the only calculation was the change between the SCS+CMM groups’ dose at implantation and 12 months out, and the CMM groups’ dose at start of the study and at 12 months out. To have used the data collected at 12 months prior to the implant/study commencement, would have been a simple thing to do, considering that the data was in hand. Leaving this data out is a weakness in this report.
The way the data was described — a” 71.4% reduction” of the SCS+CMM group’s opioid usage totals — is not an appropriate way to evaluate the medications used by subjects. The 71.4% is the total amount MME reduced by the SCS+CMM group as a whole comparing the entire group’s combined dose on day of implant with group’s combined dose 12 months out. It’s not even an average of the changes in doses among subjects in the group. But even if it were the average, pain medication is only useful as it treats the pain of the individual patient. Subject A’s change in dose has no bearing on Subject B’s experience of pain or daily functioning. Much more pertinent is the fact that only one of the SCS+CMM subjects got off opioids completely. Even with reduced doses, the subjects in both groups still required opioid medications – as well as at least some subjects requiring steroid injections and other interventions in addition to the SCS device – to treat their pain.
Another major concern is that after the 7-10 trial, subjects were included for permanent implant if there were a 50% reduction in pain and “marked improvement in function.” If any subjects were eliminated from the investigation at this point, it would artificially inflate the results favoring the claim that the SCS device is effective for pain. Leaving out the number of subjects who didn’t go on is a flaw that sinks this investigation to statistical irrelevance.
The researchers present SCS+CMM as a cost-effective alternative to opioid pain control.
The only possible way this might be the case would be if better studies showed the SCS works, and even then, it might only be less expensive than opioid treatment considering the current high ancillary expenditures required of patients prescribed opioids due to current political conditions. If the many factors that are unrelated to the true cost to manufacture and distribute opioids were subtracted, the comparison of costs of SCS and opioid medications would be very different. These additional expenses would include appointments with multiple members of a multidisciplinary pain team, appointments every 28 days for paper prescriptions, and frequent urine tests costing as much as $200 per test.
Another serious issue is that it’s entirely possible that these researchers were not measuring what they think they were measuring. The SCS+CMM subjects were chosen for motivation to reduce their opioid dosage, participated in multiple instances of medical care interactions such as the 7-10 days test, then had the installation of the permanent device, post-surgical follow up and programming the device. The study relied strongly on self-reporting measures that were almost all retrospective in nature, making them not very reliable measures of the interventions this paper discussed. All of the above, plus the plain fact of the installation of a medical device (as opposed to an injection or a capsule or a simple white pill) opens up the possibility that what was going on was not an actual improvement in the subjects’ conditions, but to a placebo response. The CMM group, who were chosen for different criteria, but who did experience many medical care interactions (aside from those related to the installation and operation of the SCS device), might also have been reporting placebo responses.
If the goal of reducing the opioid dose was the paramount goal of the subjects and the researchers, and both the process for selecting the subjects in the SCS+CMM group and the appointments after implantation included emphasis on the goal of dose-reduction, then finding some way to make objective measurements of improvement is even more vital.
Unfortunately, one way to reduce opioid dose is to just reduce the dose, and perhaps being less active, especially if activity aggravates the subject’s pain. If there were a study whose subjects were shown to have not just self-reported recollections of pain reduction, but increased levels of activity or fitness, or increased range of motion, and perhaps documented positive effects on appetite and sleep, that might be more supportive of the claim that the SCS+CMM has potential to reduce pain in real world situations. Absent objective measurements, there is insufficient evidence to support the SCS device for pain control.
But, even if the SCS device were ever objectively shown to be as effective for pain as this paper suggests, it would be of little use in terms of actually reducing the expense of pain treatment. Only one of the 32 SCS+CMM subjects was able to completely taper off opioid pain medication. If patients who have SCS implanted continue to have opioid prescriptions, with current pain management practices, the expense to the patient and the patient’s insurer would be little changed. Going by the most favorable reading of the data reported in this paper, that would be the situation for the vast majority of SCS patients.
The researchers admit that it’s possible the biopsychosocial model of interacting with the subjects may have impacted their results. I think this may be true not only for how the subjects responded to the interventions included in the study, but may also have influenced the researchers views of the effectiveness of the interventions. Everyone involved in the study, subject and researcher alike, is human and vulnerable to the human influences on reporting and viewing data that lead to reports of improvements that constitute placebo responses.
One final thought Patients needing pain treatment currently face inaccurate and negative views on opiates promoted by government and the media, increasing restrictions on opioids, and requirements for higher frequency of in-person appointments, and visits with a wider variety of professionals. This creates an environment where it’s all too easy for the government and the public to convince themselves that any alternative is a good alternative, ignoring inadequate data demonstrating efficacy or safety. This scenario is visible in a recent Federal Pain Task Force report that includes complaints that acupuncture and yoga are not covered by health insurance, which is a separate question from reviewing current opioid pain treatment practices (note: though acupuncture and yoga have been promoted as options for pain patients for a long time, evidence of their efficacy is still not documented).
For thousands of years, opium, and later, extracts and synthetics based on opium constituents, have been known to be the most effective treatment for pain. Prior to the 1940s, when black market dealers began cutting heroin with quinine, which could cause rapid closing of airways due to anaphylaxis or Stevens Johnson syndrome, opiates were not associated with deadliness. For most of history, the main complaint about opium was that a small percent of the population developed a habit they strongly resisted quitting. For patients with conditions that cause chronic severe pain that will need to be treated for life, this concern is moot. Habitual use and a strong resistance to quitting opiates is not incompatible with being a functional and contributing member of society. For example, famous surgeon and one of the funders of Johns Hopkins University, Dr.William Halstead, had a morphine habit for most of his adult life.
Considering the efficacy and safety of opioids, as well as recent discoveries of the dangers of fully-accepted medications (such as acetaminophen and proton pump inhibitors) and devices (such as surgical meshes and the Tiger Paw heart device), promoting alternatives to opioids just on account of the alternative not being an opioid, is to put patients at unnecessary risk. When the proposed alternative is far less effective at treating pain, and has a far shorter history of use during which flaws in the alternative may come to light, promoting the alternative does no service to people who, if their pain is controlled, could be able to function and contribute in their communities.
Sources
http://www.coma.ulg.ac.be/papers/vs/schnakers_ExpertRevNeurother2010.pdf
http://programinplacebostudies.org/wp-content/uploads/2015/07/PerspectivesNEJM-KaptchukMiller.pdf