Waveform-Conversion to Salvage Failed Spinal Cord Stimulation: A Systematic Review of Current Evidence

Spinal cord stimulation (SCS) has become increasingly widespread in recent years for the management of refractory chronic pain, primarily owing to the development of novel waveform technology allowing variable spinal cord modulation, and indication expansion. The existing literature suggests that despite having favorable initial responses, the efficacy of SCS sometimes is reduced over time. To restore analgesic efficacy, a strategy of altering stimulation waveforms known as salvage therapy has been used. Here, we consolidate the existing evidence and describe the efficacy of salvage therapy.

A literature search using relevant keywords was conducted on PubMed, Web of Sciences, and Cochrane Library data bases, yielding a total of 809 articles. After a full text review and screening for consistency with eligibility criteria were conducted, 22 studies with a collective sample size of 1591 patients were included in the final analysis. Data extraction was performed by six reviewers, with a secondary reviewer verifying each entry.

Of the 1591 patients included in our review, the most frequent indication for salvage therapy was loss of waveform efficacy and paresthesia coverage. In most studies, patients received salvage therapy after experiencing loss of efficacy with a single waveform. Most studies also did not strictly control the phase in which salvage therapy was implemented, with only eight of 22 studies reporting exclusively trial phase interventions. The efficacy of salvage therapy was found to be favorable, with 685 of 879 salvage therapy trials (77.9%) being reported as successful.

New waveform technologies in SCS have expanded therapeutic options for patients with refractory chronic pain. Available evidence suggests that waveform switching may restore analgesic benefit in a subset of patients who experience loss of efficacy after an initial favorable response. However, many salvage strategies involve device revision or generator replacement, and the long-term durability of these interventions remains uncertain. Further prospective studies are needed to better define patient selection, timing of intervention, and long-term outcomes after waveform-based salvage strategies.