Review of Efficacy and Safety of Spinal Cord Stimulation in Veterans

Lower back pain (LBP) affects an estimated 9.4% of the global population and has resulted in more years lived with disability than any other health condition.¹ LBP affects a wide range of populations, but US veterans have been shown to have significantly higher rates of back pain than nonveterans. The National Institutes of Health reports that 65.6% of veterans experience chronic pain; 9.1% of veterans experience severe, chronic pain.² Chronic back pain is treated by a range of methods, including medications, surgery, physical therapy (PT), patient education, and behavioral therapy.³ However, chronic neuropathic back pain has been shown to have limited responsiveness to medication.⁴

Neuropathic pain is caused by lesions in the somatosensory nervous system, resulting in spontaneous pain and amplified pain responses to both painful and nonpainful stimuli.⁵ The most common location for neuropathic pain is the back and legs. Between 10% and 40% of people who undergo lumbosacral spine surgery to treat neuropathic radicular pain will experience further neuropathic pain.⁶ This condition is referred to as failed back surgery syndrome or postlaminectomy syndrome (PLS). While neuropathic back pain has had limited responsiveness to medication and repeated lumbosacral spine surgery, spinal cord stimulation (SCS) has shown promise as an effective form of pain treatment for those experiencing PLS and other spine disorders.^7-10 In addition, SCS therapy has had a very low incidence of complications, which may be on the decline with recent technological advancements.¹¹ Patients with a diagnosis of PLS, LBP, or complex regional pain syndrome (CRPS) who have not responded to medications, therapy, and/or injections for ≥ 6 months were eligible for a trial of SCS therapy. Trial leads were placed via the percutaneous route with the battery strapped to the waistline for 3 to 5 days and were removed in clinic. Patients who experienced > 60% pain relief and functional improvement received a SCS implant.

The effectiveness of SCS has been demonstrated in a nonveteran population, but it has not been studied in a veteran population.¹² US Department of Veterans Affairs (VA) health care coverage is different from Medicare and private insurance in that it is classified as a benefit and not insurance. The goals of treatment at the VA may include considerations in addition to feeling better, and patient presentations may not align with those in the private sector.

We hypothesize that SCS is both a safe and beneficial treatment option for veterans with chronic intractable spine and/or extremity pain. The purpose of this study was to determine the efficacy and safety of SCS in a veteran population.

Methods

The efficacy and safety of SCS was determined via a retrospective study. Inclusion criteria for the study consisted of any Southeastern Louisiana Veterans Health Care System (SLVHCS) patient who had an SCS trial and/or implant from 2008 to 2020. Eligible veterans must have had chronic pain for at least 6 months and had previously tried multiple medications, PT, transcutaneous nerve stimulation, facet injections, epidural steroid injections, or surgery without success. For medication therapy to be considered unsuccessful, it must have included acetaminophen, nonsteroidal anti-inflammatory drugs, and ≥ 1 adjuvant medication (gabapentin, duloxetine, amitriptyline, lidocaine, and menthol). A diagnosis of chronic LBP, PLS, cervical or lumbar spondylosis with radiculopathy, complex regional pain syndrome, or chronic pain syndrome was required for eligibility. Patients whose pain decreased by > 60% and had functional improvement in a 3- to 5-day trial received SCS implantation with percutaneous leads by a pain physician or paddle lead by a neurosurgeon.

The SLVHCS Institutional Review Board approved this study. Electronic health records were reviewed to determine patient age, anthropometric data, and date of SCS implantation. Patients were then called and interviewed to complete a survey. After obtaining verbal consent to the study, subjects were surveyed regarding whether the patient would recommend the procedure to peers, adverse effects (AEs) or complications, and the ability to decrease opiates if applicable. A verbal Pain Outcome Questionnaire (POQ) assessment of activities of daily living also was given during the phone interview regarding pain levels before SCS and at the time of the phone interview.¹³ (eAppendix available at doi:10.12788/fp.0204) Following the survey, a chart review was performed to corroborate the given AEs or complications and opiate use information. Before and after results of the POQ were compared via a paired sample t test, and P values < .05 were considered significant. Analyses were performed by IBM SPSS, version 26.

The primary outcome measure for this study was whether veterans would recommend SCS to their peers; in our view, this categorical outcome measure seemed to be more valuable to share with future patients who might be candidates for SCS. Since VA health care coverage and goals of treatment may be different from a nonveteran population, we opted to use this primary measure to decrease the possibility of confounding variables.

Secondary outcome measures included changes in POC scores, improvements in activities of daily living, and decreases in use of opioid pain medications.

POQ responses were recorded during the telephone interviews (0 to 10 scale). A paired sample t test was conducted to compare pain levels before and after SCS implant. Pain levels were gathered in the single phone call. Patient opioid usage, if applicable, was assessed by converting medications to morphine milligram equivalent dosing (MMED). Since patients who were on chronic opioids took multiple formulations, we changed the total daily dose to all morphine; for this study, morphine was considered equivalent to hydrocodone, and oxycodone was 1.5x morphine.