Utilization

Goyal et al performed an analysis using the National Inpatient Sample (NIS) data sets from the Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project from 2008 to 2014. The authors separately queried state ambulatory surgery databases from Kentucky, Florida and New York for the years 2013–2015 to demonstrate outpatient utilization of SCS as a basis for comparison. In this study, the NIS was queried for patients undergoing SCS using ICD-9 Clinical Modification procedure code of 03.93 (implantation or replacement of spinal neurostimulator leads). This code is used for both temporary (trial) leads destined for removal and for leads implanted for long-term use with an implanted pulse generator and does not distinguish between them. Initially, inpatient SCS-related procedures rose 15.7% from 2008 to 2011. This was followed by a 52.4% decrease in inpatient utilization between the years 2011 and 2014. The most common diagnoses included degenerative spine disease followed by pain syndromes. The most common primary admission diagnosis was mechanical complications of nervous system device to treat device-related malfunctions or complications although this declined steadily over time. Overall, the inpatient utilization decrease likely reflects a move to the ambulatory setting for these procedures.6

Manchikanti et al studied the utilization of SCS in fee-for-service Medicare patients from 2009 to 2018. Over that period of time, there was a 362% total increase in SCS trials performed percutaneously from 12 680 in 2009 to 36 280 in 2018, with an annual increase of 12.4%. Percutaneous SCS implantation rates increased a total of 252% over the 9-year period from 4080 in 2009 to 14 316 in 2018, with an annual increase of 15%. SCS implantation with paddle lead neurostimulator electrodes increased 142% over the study period from 3560 in 2009 to 8600 in 2018, with an annual increase to 10.3% (table 1). The trial to implant ratio increased significantly from 42.5% in 2009 to 63.6% in 2018. The vast majority of trials (90%) were performed by non-surgical physicians. In contrast, only 56% of implants were performed by non-surgical physicians.7 Romaniuk et al examined trends in utilization of SCS in fee-for-service Medicare patients from 2000 to 2019. During this time period, there was an average 21.9% annual increase in percutaneous SCS placement operations and an average 18.4% annual increase in open SCS placement operations. Numerically, percutaneous SCS placement increased from 3595 procedures in 2000 to 1 32 281 in 2019 and represents a 3579.6% increase over the study period. Open SCS placement increased from 526 in 2000 to 10 688 in 2019 and represents a 1931.9% increase over the study period.3

Diagnoses

In a retrospective analysis of more than 20 000 patients in whom SCS trial to implantation was studied from 2000 to 2009, diagnoses most commonly associated with successful SCS trials included postlaminectomy syndrome (44%, p<0.0001), CRPS (45%, p<0.0023), neuritis/radiculitis (44%, p<0.0001) and chronic pain (46%, p<0.0001).4 The most common diagnosis associated with SCS implantation in an analysis of SCS utilization in a national inpatient data set and state-level ambulatory surgery database from 2008 through 2014 was degenerative spine disease (42.73%) followed by pain syndromes (25.87%), which includes central pain syndrome, chronic pain syndrome and causalgia.6 At the present time, both FDA-approved and non-FDA-approved clinical indications have expanded. There are growing numbers of SCS implants being performed for CRPS, visceral pain, painful diabetic neuropathy and non-surgical refractory back pain.

Cost

Total inflation-adjusted expenditures for SCS in the fee-for-service Medicare population increased from $292 153 701 in 2009 to $1 142 434 137 US dollars in 2018, equating to a total increase of 291%. In 2009, these expenditures were 55% and 66% lower than facet joint interventions and epidural steroid injections, respectively. In 2018, these expenditures were 125% and 138% higher than facet joint interventions and epidural steroid injections, respectively.7 The size of the global SCS market continues to grow. It was $2.88 billion in 2019 and is predicted to grow to $4.12 billion by 2027.8

Elsamadicy et al studied the cost of failed back surgery syndrome (FBSS) in commercial, Medicare and Medicaid in patients who underwent SCS implantation as compared with those who did not. They identified 122 827 FBBS patients, with 1 17 499 patients who did not undergo SCS implantation and 5328 who did. Their retrospective study showed over a 12-year period in non-SCS patients, Medicaid patients had the lowest mean cost at $4,530, followed by commercial at $4,944, and then Medicare at $7292 US dollars. Over a 9-year period for SCS patients, commercial patients had the lowest mean cost at $2098, followed by Medicaid patients at $4045, and then Medicare patients at $7158 US dollars (table 2). The authors concluded that SCS is cost-effective across all insurance groups.9

Romaniuk et al looked at trends in reimbursement of SCS in fee-for-service Medicare patients from 2000 to 2019. Medicare paid $1.02 billion US dollars to physicians for percutaneous SCS operations and nearly $145 million US dollars to physicians in reimbursement for paddle lead SCS operations over this time period. Over these 19 years, mean Medicare reimbursement to physicians for SCS placement increased by $899.37 (202.6%) and $1882.48 (242.2%) US dollars for percutaneous and paddle lead SCS operations respectively after adjustment for inflation. The total payment to physicians for both procedures grew from $2 004 441.51 in 2000 to $206 106 434.29 US dollars in 2019. This was a net increase of $204 101 992.78 US dollars or 10 182.5%.3

The role of cost is not limited to the neuromodulation market in the USA. A recent manuscript entitled Cost-Utility and Cost-Effectiveness Analysis of Spinal Cord Stimulation for Chronic Refractory Pain in the Context of a Developing Country examined clinical outcomes, quality of life and costs of treatment before and after SCS implantation in Thailand in patient’s refractory to conventional medical management (CMM). The authors included 29 patients who underwent SCS implantation and had improvements in pain intensity and utility at all measured time points. The incremental cost–utility ratio (ICUR) per quality-adjusted life year (QALY) gained as well as the incremental cost-effective ratio per numeric rating score reduction were measured. The QALY gained in both rechargeable and non-rechargeable SCS was 2.13 QALYs. Their economic analysis demonstrated that the ICUR in the rechargeable and non-rechargeable SCS with CMM group exceeded the Thai’s willingness-to-paythreshold.10 Although this study is limited to Thailand, the issue of cost and willingness to pay relative to income in developing countries is real and will continue to play a role in the growth and utilization of this technology in the larger global community until such time as the cost becomes more realistic depending on geographic location and average income.

Patient characteristics

Rates of SCS trial and implantation in the fee-for-service Medicare population were typically higher in women compared with men year per year between the years of 2009 and 2018 and steadily increased for both groups over the 9-year study period. The rate per 1 00 000 patients increased for women from 29 in 2009 to 62 in 2018, for a total increase of 111%. For men, the rate increased from 25 to 60 per 1 00 000 patients, for a total increase of 134%. The rate of SCS implantation saw a similar trend, with a female implantation rate of 16 in 2009 and 39 in 2018 per 1 00 000 patients, for an overall increase of 140%. In men, the implantation rate increased from 17 in 2009 to 38 in 2018 per 1 00 000 patients, for an overall increase of 120%.6 A higher female implantation rate was also seen in an analysis of a national inpatient data set and state-level ambulatory surgery database from 2008 to 2014. In that analysis, women accounted for 58.60% of SCS implant procedures as compared with men (41.07%).6

Patients under the age of 65 years had the highest rate of implantation per 1 00 000 patients throughout all years studied, with a rate of 42 in 2009 and 77 in 2018, for an overall increase of 84%. This was followed by the age group 75–84 years (rate of 13 in 2009 and 40 in 2018), then those aged 65–74 years (rate of 13 in 2009 and 32 in 2018), and finally those over the age of 84 years (rate of 3 in 2009 and 15 in 2018) (all figures are per 100 000 patients). The overall increase through the 9-year study range was greatest in the 85-year-old group (324%), followed by the 75–84-year-old group (207%), then the group aged 65–74 years old (141%), and finally the group under 65 years of age (84%).7 In an analysis, a national inpatient data set and state-level ambulatory surgery database from 2008 through 2014, the age group with the greatest increase in the rate of SCS implantation was between the ages of 45 and 64 years (47.82%), followed by individuals between the ages of 65 and 84 years (27.49%).6

In the Medicare population, there were significant differences in both frequency of SCS trials and placements on the basis of race. Caucasians had the highest rate of trials, with a rate of 32 per 100 000 in 2009 and 72 in 2018. This is in comparison to African-Americans who had a rate of 21 per 100 000 in 2009 and 35 in 2018 and other racial groups (“Others”) who had a rate of 6 per 100 000 in 2009 and 20 in 2019. Caucasians had the highest rate of SCS placement, with a rate of 19 per 100 000 in 2009 and 47 in 2018. This is in comparison to African-Americans who had a rate of 13 per 100 000 in 2009 and 20 in 2018 and Others with rates of implantation of 3 per 100 000 in 2009 and 10 in 2018. The implantation rate per 100 000 increased the most in the Others group (211%), followed by Caucasian (143%), and then African American (54%).7 Studying trends of patient demographics may help pain physicians not only identify patient groups for whom SCS therapy may be beneficial but also help to ensure that all patients have equal access to this treatment modality.

Huang and colleagues performed a retrospective cohort study of 13 774 patients examining insurance disparities in the outcome of patients undergoing percutaneous or paddle lead permanent SCS placement. Medicaid patients had greater utilization of healthcare resources in terms of medications prescribed, emergency department and clinic visits and length of stay; however, commercially insured patients had significantly higher overall costs at 2 years ($101 952 vs $64,644 US dollars); these costs include index hospitalization and postoperative healthcare resources. Commercial and Medicaid patients did not have significantly different complication rates during initial hospitalization, or at 30 or 90 days postoperatively. In addition, there was no significant difference in their 2-year reoperation rates (7.32% vs 5.06% p=0.0513). In a study of SCS trial-to-permanent conversion rates from 2000 to 2009 using the Thompson Reuter MarketScan Database, 21 672 unique instances of percutaneous trials were identified. Of these, 8982 patients (41.4%) underwent permanent implantation within 3 months of their trial. Factors associated with a higher likelihood of conversion to permanent implant included having commercial insurance (43% vs 37%, p<0.0001), being of younger age (43% for those 35–44 years old vs 39% for those greater than 65 years old, p<0.00001) and having no history of previous SCS trials (44% for first-time trials vs 14% for third or subsequent trials, p<0.00001) (table 3). Geographically, patients in the North Central and Southern regions tended to have greater SCS trial success (45% and 43%, respectively) compared with the West and Northeastern regions (37% and 36%, respectively, p<0.0001).11

In an analysis, a national inpatient data set and state-level ambulatory surgery database from 2008 through 2014, Medicare was the most common payer type (44.56%), followed by private insurance (34.90%).6

Setting/provider characteristics

There has been a steady move away from inpatient SCS placement to outpatient placement performed in ambulatory surgery centers (ASC). Rates of SCS implantation increased the most in the ASC, with a rate of 2 per 100 000 in 2009 to 14 in 2018, an overall increase of 690% in the Medicare population. This is in comparison to the hospital outpatient department (HOPD) setting, which increased from 15 in 2009 to 24 in 2018, equating to an increase of 62%.7 The increase in SCS implantation occurring in ASCs may reflect a number of factors, including greater efficiency in doing the procedures in this setting as well as reduced cost compared with the HOPD setting and, thus, improved physician and patient satisfaction without compromising patient safety. Theere may also be financial incentives to the ASC owners to perform the procedures in this setting. In some patients, including the Medicare population, these patients may have other comorbidities that make it safer to perform these procedures in a HOPD. However, as far as the authors are aware, no studies have been done to date to compare complication rates for SCS implantation in the ASC versus HOPD settings. The overall volume of all SCS implantation procedures by pain management physicians (those with training in Pain management, Anesthesia, PM&R, Neurology) has increased from 51% in 2009 to 56% in 2018 for Medicare patients. Conversely, SCS implantation by surgeons (those with training in orthopedic surgery or neurosurgery) has decreased from 48% in 2009 to 42% in 2018.6 The available data do not specify what proportion of these implants was percutaneous leads versus paddle leads. The increase in SCS implantation by pain management specialists may reflect the greater exposure these individuals receive in their fellowship training. However, many pain fellows feel that there remains a deficiency in SCS training during their fellowship training and this is a predominant factor in their decision not to perform SCS implantation post-fellowship.12 These deficiencies can be overcome with mentoring and proctoring with experienced physicians in some practice settings.

Murphy et al studied the volume–outcome effect on SCS trial-to-permanent conversion rates in a retrospective and non-randomized analysis using the Marketscan database between 2007 and 2012. A total of 17 850 unique trial implants were performed. Of 13 879 patients with baseline data available, 8981 patients underwent permanent implant (64.7%). They found that higher volume providers (defined as those with greater than 25 documented implants) had a higher conversion rate (65.9%) compared with medium-volume providers (9–24 documented implants; 65.1%) and low-volume providers (less than 3–8 documented implants; 63.3%, p=0.0292). Interestingly, the high-volume implanting group also had the highest rate of explantation; however, more research would need to be done to determine the causes of explantation.13

Goyal et al performed an analysis of a national inpatient data set and state-level ambulatory surgery database from 2008 through 2014 and found that most inpatient implants occurred in large hospitals (66.71%) and at urban teaching hospitals (60.18%).6

Complications

From 2012 through 2019, a total of 26 786 spinal cord stimulators were implanted in Australia and 520 adverse events were reported to Australia’s Therapeutic Goods Association. The most common adverse events were device malfunction (used for events where the device malfunctioned but a code describing specific patient harm could not be described, eg, device migration; 296 events or 56.5%), pain (used when patient complained of pain at implant site or other body part but no reason for pain was described; 110 events or 21.05%), infection (55 events or 10.5%), hemorrhage/hematoma (7 events or 1.3%). According to the Australian National Health and Medical Research Council, 66 events (13%) were classified as life threatening and 412 (79%) were classified as severe. The most common response taken was single surgical operation (383 events or 73.1%), single surgical intervention and intravenous antibiotics (21 events or 4.0%) and multiple surgical operations (16 events or 3.1%).14

An analysis of the United States Closed Claim Project database showed that the most common complication for surgical device-related claims for implantable pain therapies was infection, accounting for 23% of all claims.15 According to a research analysis looking at insurance claims database, the infection rate for SCS was found to be 3.11%.16 Provenzano et al studied infection rates and annual expenditures related to infections following SCS implantation and implantable pulse generators (IPG) replacement. They did not find a significant difference in infection rates between the implantation and replacement groups (implantation group infection rate 3.09%, replacement group infection rate 3.23%; p value 0.8104). Median time to infection was 48.5 days and mean time to infection was 88.5 days. The unadjusted mean cost difference in patients with device-related infection was $38 990 in the implant group and $46 966 US dollars in the replacement group. Adjusted cost differences in the implant group were $59 716 in the implant group and $64 833 US dollars in the replacement group. Of those patients who developed a device-related infection, 73% underwent explant of their device. Only 26% of the explant group underwent subsequent reimplantation of their device. The median and mean time to reimplantation were 147 and 206 days, respectively.17

The use of dorsal root ganglion (DRG) stimulation, a modification of SCS, has also seen significant growth in utilization since its initial introduction in 2016 and has been associated with a significant incidence of complications as well. Sivanesan and collegues performed a retrospective analysis of complications associated with DRG stimulation in the FDA Manufacturer and User Facility Device Experience (MAUDE) database. They identified 979 unique episodes with 47% representing device-related complications and 28% procedural complications, 12% patient complaints, 2.4% serious adverse events and 4.6% “other” complications. The majority were managed with surgical revision 49.8% as opposed to explantation 16.4%.18 Eldabe et al performed a prospective, single-site, long-term follow-up of DRG stimulation for management of chronic intractable pain in 32 patients from the United Kingdom. The patients had their devices implanted between 2013 and 2015 and were contacted in 2020 for a final follow-up. At this point, 50% were still using their device and had a pain score reduction of 2.1. Pulse generators had been explanted in 8 patients because of dissatisfaction with pain relief. The patients in this study had a revision rate of 42% within the first 24 months and 56% of the IPG that were replaced due to battery depletion had a shorter than expected battery life.19 Hines et al examined outcomes in a single-center retrospective analysis of device-related complications related to DRG stimulation for pain relief in 31 patients. At a 1-year follow-up, 26% of the devices had been explanted and 29% required revision surgery. They felt this represented an unacceptably high incidence of hardware failure requiring a high rate of revision surgery and explantation procedures. They called for technological advancement and optimization to deliver high-quality care to patients with neuropathic pain.20