Karri, Jay

Background Peripheral nerve stimulation (PNS) is an emerging neuromodulation therapy for chronic pain, yet its use in clinical practice varies significantly. Although temporary PNS is widely incorporated, either as a screening trial or a treatment itself, the evidence supporting the use of temporary PNS prior to permanent implantation is limited. We aimed to compare pain relief, opioid consumption, and adverse events between an approach implementing temporary PNS before permanent implantation (temporary-to-permanent (TTP)) vs proceeding directly to permanent PNS implantation (direct-to-permanent (DTP)). Methods A multicenter retrospective study was undertaken at seven major academic institutions from January 1, 2014, to January 1, 2024. Adult patients who underwent permanent PNS implantation for the treatment of chronic pain conditions were included and were divided into TTP or DTP cohorts based on their clinical approach. The dual primary outcomes were pain relief and opioid consumption (in oral morphine equivalents) at 6 months compared with baseline before any PNS therapy. Multivariable Tobit regression analysis was performed to identify predictors of pain relief at 6 months using a stepwise approach. Results A total of 130 patients were analyzed (54 in TTP approach, 76 in DTP approach). Patient-reported percentage pain relief was 56.7%±27.9% at 6 months compared with baseline (before PNS implantation) in the TTP cohort, and 45.1%±33.6% in the DTP cohort. The estimated mean percentage pain relief at 6 months was similar in the TTP and DTP cohorts (between-group difference 15.24%; 95% CI −0.32 to 30.80, p=0.052), with consistent findings after sensitivity analysis with multiple imputation. Opioid consumption declined similarly in the TTP (−3.1±9.9 mg) and DTP (−2.1±8.1 mg) cohorts at 6 months with no statistical difference between cohorts (mean between-group difference: −1.00, 95% CI −4.57 to 2.57, p=0.580), and with consistent findings after sensitivity analysis. Device explantation rates and adverse event profiles were comparable between cohorts. Conclusion Although temporary PNS is widely performed prior to permanent PNS implantation, there was no evidence that the TTP approach is associated with superior analgesic outcomes compared with the DTP approach. Further, patients in both approaches achieved clinically meaningful pain relief at 6 months compared with baseline status prior to PNS therapy.

The trial-to-implant ratio for spinal cord stimulation (SCS) has long served as a cornerstone metric for optimizing patient selection and cost containment. Historically, screening trials played a pivotal role in identifying non-responders, thereby minimizing unnecessary permanent implantations. The utility of the trial paradigm is supported by Medicare data from 2009, which reported a trial-to-implant ratio of 42.5%. However, advancements in SCS technology have significantly transformed the neuromodulation landscape and have been associated with higher rates of trial success. By 2018, the Medicare data showed trial-to-implant ratios exceeding 63%, with randomized clinical trials from 2020 to 2021 reporting ratios exceeding 80%–90%. These significant increases in trial-to-implant ratios suggest that only a minority of SCS candidates do not undergo a subsequent permanent device implantation. As such, re-evaluation of the trial-to-implant paradigm, from the perspective of practicing pain physicians in the USA, in light of evolving clinical practices and economic pressures, is warranted. This discourse explores the benefits and limitations of the trial-to-implant ratio, emphasizing its role as a safeguard against overutilization and a tool for standardizing clinical practices but weighed against its shortcomings including a lack of alignment with long-term outcomes, underscore the need for alternative metrics that include per capita trial utilization and explant-to-implant ratios. European responses to similar questions have resulted in utilizing validated symptom screening tools and direct-to-implant pathways in lieu of a screening trial altogether as potential strategies to optimize SCS utilization while maintaining cost-effectiveness. As healthcare systems adapt to advancements in neuromodulation, a balanced perspective on trial-to-implant ratios and complementary metrics is essential to ensure equitable access, sustainable outcomes and evidence-based care for the future of SCS therapy.