Cost-Effectiveness Analysis of Peripheral Nerve Field Stimulation as Add-On Therapy to Spinal Cord Stimulation in the Treatment of Chronic Low Back Pain in Failed Back Surgery Syndrome Patients.

OBJECTIVE: Presently, there is only limited evidence about the cost-effectiveness of peripheral nerve field stimulation (PNFS) and no evidence to date on the cost-effectiveness of PNFS as an add-on therapy to spinal cord stimulation (SCS). In a multicenter randomized controlled trial, PNFS as add-on therapy to SCS demonstrated clinical effectiveness in treating chronic low back pain in failed back surgery syndrome (FBSS) patients. We report here the cost-effectiveness of PNFS as additional therapy. MATERIALS AND METHODS: Cost-effectiveness analysis was performed from a health-care perspective using the general principles of cost-utility analysis, using empirical data from our multicenter randomized controlled trial on the effectiveness of hybrid SCS + PNFS on low back pain in FBSS patients, who were back pain non-responders to initial SCS-therapy, over a time-horizon of three months. Outcome measures were costs and quality-adjusted life-years (QALYs). Cost and QALYs were integrated using the net monetary benefit (NMB). Differences in costs, effects, and NMB were analyzed using multilevel regression. Uncertainty surrounding the NMB was presented by cost-effectiveness acceptability curves. RESULTS: A total of 52 patients implanted with both SCS and PNFS, randomly assigned to a group with PNFS either activated or inactive, completed the controlled part of the study. With mean total costs for the SCS + active PNFS group of €1813.86 (SD €109.78) versus €1103.64 (SD €123.43) for the SCS + inactive PNFS group at three months, we found an incremental cost-utility ratio of €25.311 per QALY gained and a probability being cost-effective of more than 80% given a willingness to pay for a QALY of about €40.000. CONCLUSIONS: From a Dutch national health-care context, when the willingness to pay threshold is up to 60.000 Euros per QALY, PNFS as an add-on therapy to SCS for the treatment of low back pain in FBSS patients has a high probability of being cost-effective.

Long-Term Effect of Peripheral Nerve Field Stimulation as Add-On Therapy to Spinal Cord Stimulation to Treat Low Back Pain in Failed Back Surgery Syndrome Patients: A 12-Month Follow-Up of a Randomized Controlled Study.

OBJECTIVE: Different approaches in neuromodulation have been used to treat chronic low back pain in failed back surgery syndrome (FBSS) patients. We previously randomized 52 FBSS patients to be treated with spinal cord stimulation (SCS) and additional peripheral nerve field stimulation (PNFS) or SCS alone. At three months, we found a significant reduction of back pain in the PNFS-SCS group compared to the SCS group. In the subsequent open phase part of the study, all patients received optimal SCS and PNFS simultaneously. Here, we present the 12-month follow-up data on back and leg pain. MATERIALS AND METHODS: Data regarding back and leg pain, function, quality of life, patient satisfaction, anxiety and depression, and use of medication were collected by analyzing patients' questionnaires at 12 months and compared with data collected at baseline. Data were analyzed using multilevel regression models. RESULTS: A combined group of 50 subjects completed the 12-month follow-up. Back pain, measured on a 100-mm visual analog scale (VAS), significantly decreased over this period by 30.0 mm (95% CI: [-37.7/-22.4]; p < 0.001), while leg pain decreased by 43.7 mm (95% CI: [-51.5/-36.2]; p < 0.001). We observed statistically significant improvement in almost all secondary outcome measurements. CONCLUSIONS: At 12-month follow-up, PNFS in addition to SCS continues to provide a statistically significant and clinically relevant relief of low back pain in FBSS patients in whom SCS alone is effective for relief of leg pain only.

Subcutaneous Stimulation as ADD-ON Therapy to Spinal Cord Stimulation Is Effective in Treating Low Back Pain in Patients With Failed Back Surgery Syndrome: A Multicenter Randomized Controlled Trial.

OBJECTIVE: Suppression of back pain with traditional spinal cord stimulation (SCS) in failed back surgery syndrome patients is often insufficient. The objective of this study was to investigate the efficacy of subcutaneous stimulation (SubQ) as ADD-ON therapy to SCS in treating back pain in failed back surgery syndrome patients. MATERIALS AND METHODS: Patients with a minimal pain score of 50 on a 100 mm visual analog scale for both leg and back pain were eligible. If pain reduction after trial SCS was ≥50% for the leg but <50% for the back, patients received additional SubQ leads and were randomized in a 1:1 ratio in a study arm with subcutaneous leads switched on (SubQ ADD-ON) and an arm with subcutaneous leads switched off (Control). The primary outcome was the percentage of the patients, at three months since implantation, with ≥50% reduction of back pain. RESULTS: A total of 97 patients were treated with SCS for leg and back pain. Of these, 52 patients were randomized and allocated to the Control group (n = 24) or to the SubQ ADD-ON group (n = 28). The percentage of patients with ≥50% reduction of back pain was significantly higher in the SubQ ADD-ON group (42.9%) compared to the Control group (4.2%). Mean visual analog scale for back pain, at three months, was a statistically significant 28.1 mm lower in the SubQ ADD-ON group compared to the Control group. CONCLUSION: Subcutaneous stimulation as an ADD-ON therapy to SCS is effective in treating back pain in failed back surgery syndrome patients where SCS is only effective for pain in the leg.

The effect of spinal cord stimulation (SCS) on static balance and gait.

OBJECTIVES: To investigate whether spinal cord stimulation (SCS) has a negative effect on static balance and gait, which is implicated by the increased incidence of falls leading to frequently occurring lead migrations. MATERIALS AND METHODS: A controlled trial is performed with 11 subjects (four female, seven male) with a mean age of 46 years old. A baseline measurement consisting of static balance and gait tests was performed. Within two weeks after implantation of a spinal cord stimulator, subjects performed the same tests with both stimulation switched on and off. Static balance was assessed with eyes open and eyes closed on hard surface and foam surface. The velocity of the center of pressure and weight symmetry were the main outcome parameters. Kinematics and spatiotemporal outcome parameters were used to analyze gait. ANOVAs were used to compare between baseline, stimulation on, and stimulation off. RESULTS: Spinal cord stimulation resulted in significant pain relief as scored on a Visual Analog Scale (p < 0.001). Gait width decreased and this change (indicative of improvement in balance) was significant (p = 0.007). No other significant group differences were found between stimulation baseline and post-surgery measurements. SCS did not influence static balance or gait when group effects were analyzed. Four subjects showed significant differences in static balance between stimulation on and off. CONCLUSIONS: The lack of group differences in normal gait and static balance cannot explain the increased incidence of falls. However, four subjects showed an effect of SCS on static balance. Further research to clarify why only a part of the subjects experienced balance problems is recommended and assessments of more demanding balance and gait tasks are desirable.

Percutaneously implanted plates in failed back surgery syndrome (FBSS).

OBJECTIVE: To evaluate the clinical efficacy of pain suppression in back area and lower extremities by recently developed plate electrodes for spinal cord stimulation through percutaneous access. METHODS: A retrospective analysis is performed: 20 consecutive patients with both lower extremity pain and low back pain, with low back counting for at least 30% of the overall pain were implanted with a small profile plate type lead, S-Series (SJM), via percutaneous approach. Patients were asked to rate their back and leg pain as well as their overall satisfaction and data on quality of life (QOL) on a (0-10 point) visual analog scale (VAS) before and after implantation. Medication use, functional pain (pain when bending forward, moving), and patient satisfaction scores also were collected. RESULTS: A significant reduction of 55% and 45.7% in, respectively, VAS legs and VAS back pain was found. One year postoperatively the reduction was still present, respectively, 43% and 27% for the legs and the back. In 17 patients (85%) a clinically relevant reduction (defined as reduction of 2 points or 30% in VAS) in back pain was seen, with a mean decrease of 4.3 points (2.0-10.0) or 52% (22-100). Only three patients had no reduction in back pain, although they had reduction of their pain in the lower extremities. A significant and clinically relevant improvement of 66% and 70% was seen, respectively, for general satisfaction and QOL, respectively. One year postoperatively this improvement was still present, respectively, 69% and 75% for the satisfaction and QOL. Importantly functional pain also decreased by 51%. No infections occurred. Mean duration of post-op wound pain was 13.5 hours. CONCLUSION: Percutaneous implantation of the S-Series plate electrodes using a 10 gauge epidural needle combines the advantages of a minimal invasive technique with the possibility to cover the back area supplementing leg coverage in 85% of the failed back surgery syndrome patients.