Multi-waveform Spinal Cord Stimulation with High Frequency Electromagnetic Coupled (HF-EMC) Powered Implanted Electrode Array and Receiver for the Treatment of Chronic Back and Leg Pain (SURF Study).

BACKGROUND: Novel externally powered spinal cord stimulation technology can be fully implanted when trialing the effectiveness of the therapy, since no percutaneous leads are needed, and the trial period lasted 30 days. Multiple tests of different stimulation modalities and parameters are possible, thus improving the chances that the therapy will lead to effective pain reduction. OBJECTIVES: The objective of this study was to analyze the effectiveness of the Freedom Spinal Cord Stimulator System (Stimwave LLC, Pompano Beach, FL) for the treatment of failed back surgery syndrome due to postlaminectomy syndrome utilizing multiple waveforms. STUDY DESIGN: This was a prospective, single cohort study. Patients were enrolled and implanted with up to 2 permanent, 8-contact electrode arrays with receiver, controlled regularly during 6 months of follow-up after a one month trial period. Pain and overall improvement were evaluated at 3 months and 6 months following an initial one-month implanted trial period. SETTINGS: A variety of frequency stimulation waveforms (tonic as well as subthreshold) at frequencies of 10 Hz to 1500 Hz* and 50 to 800 µs pulse width, were provided. (*Note: While 1500 Hz was utilized in the study, Stimwave Technologies is currently only permitted to provide spinal cord stimulation therapy at frequencies below 1500 Hz, therefore pulse rates used in this study are not commercially available on Stimwave Technologies' products). METHODS: Endpoints evaluated included the Visual Analog Scale (VAS) for pain intensity, Oswestry Disability Index (ODI) for functionality, Patient Global Impression of Change (PGIC) for overall health improvement, and quality of life as measured by the European Quality of Life 5 Dimension questionnaire (EQ-5D-5L). RESULTS: Thirty-nine patients completed the study. At 6 months, the responder rate (? 50% reduction VAS for back pain) was 33/39 = 85%. Mean VAS for back pain decreased 62%. The mean ODI decreased 46% from 54 to 29.2, indicating a reduction from severe to moderate disability. The median satisfaction as measured with the PGIC was 6 out of 7. The mean EQ-5D-5L utility score increased from 0.54 to 0.75. At the 6-months endpoint, 44% (17/39) of patients preferred tonic stimulation with a back pain per protocol responder rate of 82%; 41% (16/39) preferred surge with a responder rate of 56%; and 15% (6/39) preferred high density, with a responder rate of 83%. Fifteen patients reported 28 adverse events. Migration of the electrode array (n = 10) was the adverse event most reported. Two serious adverse events related to infection were reported. LIMITATIONS: This study had several limitations. Trial failures were excluded from the analysis, there was a small sample size, and there was a lack of blinding due to the suprathreshold nature of tonic stimulation. CONCLUSION: The study demonstrates that spinal cord stimulation with multiple stimulation patterns demonstrates clinical and functional efficacy when using an externally powered stimulation system.

Redefining Spinal Cord Stimulation "Trials": A Randomized Controlled Trial Using Single-Stage Wireless Permanent Implantable Devices.

BACKGROUND: "Traditional" spinal cord stimulation (SCS) trials with percutaneous electrodes externalized to a pulse generator (PG) are typically limited in duration due to risk of infection. Newer miniaturized wireless SCS technology eliminates the percutaneous extension (as well as PGs implanted for chronic use), thus facilitating a single-stage implantation after which the device can remain indefinitely. OBJECTIVE: To evaluate fully implanted wireless SCS devices during a 30-day screening trial in subjects with chronic low back pain and leg pain and a history of lumbosacral spine surgery. METHODS: In a randomized controlled trial of single-stage wireless SCS using a wireless percutaneous system, 99 subjects received either 10 kHz high frequency stimulation (HFS) or lower frequency stimulation (LFS) below 1500 Hz (Bolash R, Creamer M, Rauck R, et al. Wireless high frequency spinal cord stimulation (10 kHz) compared to multi-waveform low frequency spinal cord stimulation in the management of chronic pain in failed back surgery syndrome subjects: preliminary results of a multicenter, prospective, randomized controlled study. Pain Med 2019, https://doi.org/10.1093/pm/pnz019). In this report, we assess the 30-day trial success rate (≥50% pain relief from baseline) and complications. RESULTS: The overall trial success rate was 88% (87/99): 92% (46/50) for HFS and 84% (41/49) for LFS (NS). The trial success rate in the 64 subjects with predominant low back pain was 92% (59/64) vs. 80% (28/35) in those with leg pain ≥ low back pain (NS). During the screening trial, one infection occurred (1%) and one subject withdrew and was explanted (1%). Electrode migrations were seen on routine follow-up x-rays in 10 cases (10%). CONCLUSION: Using wireless SCS devices that allow for an extended trial period and evaluation of various waveforms, we observed a high rate trial success rate with both HFS and LFS waveforms, with minimal incidence of infection. Long-term follow-up will address the cost-effectiveness and morbidity associated with this technology, which facilitates single-stage treatment.

Wireless High-Frequency Spinal Cord Stimulation (10 kHz) Compared with Multiwaveform Low-Frequency Spinal Cord Stimulation in the Management of Chronic Pain in Failed Back Surgery Syndrome Subjects: Preliminary Results of a Multicenter, Prospective Randomized Controlled Study.

BACKGROUND: This study aimed to evaluate the wireless Freedom Spinal Cord Stimulator (WSCS) System for the treatment of chronic back and/or leg pain associated with failed back surgery syndrome (FBSS) refractory to standard medical treatment utilizing 10-kHz stimulation (high-frequency [HF]) in comparison with 10-1,500-Hz stimulation (low-frequency [LF]) waveforms. METHODS: Ninety-nine subjects were randomized in a 1:1 ratio to receive either HF or LF stimulation waveforms utilizing the same Freedom WSCS System. All subjects were implanted with two 8-electrode arrays in the exact same anatomical positions within the dorsal epidural spinal column, with the top electrode positioned at the T8 and T9 vertebrae levels, respectively, and the wireless receiver placed under the skin in a subcutaneous pocket. RESULTS: Seventy-two (HF: N = 38; LF: N = 34) subjects had completed the six-month follow-up after an initial 30-day trial period at the time of this report. For both the HF and LF arms, mean visual analog scale (VAS) scores for back and leg pain decreased significantly: 77% and 76%, respectively, for the HF arm and 64% and 64%, respectively, for the LF arm. In addition, most subjects experienced significant improvements in VAS, Oswestry Disability Index, European Quality of Life 5 Dimension questionnaire, Patient Global Impression of Change, and sleep duration. CONCLUSIONS: These preliminary results demonstrate that WSCS devices can reduce FBSS chronic pain substantially with both LF and HF stimulation waveforms over a seven-month period (30-day trial period and six-month post-trial evaluation).