Wayne L Harper, William K Schmidt, Nicole J Kubat, Richard A Isenberg

Persistent pain following back surgery remains a major treatment challenge. The primary objective of this open-label exploratory study was to investigate the analgesic effectiveness of pulsed electromagnetic field therapy administered twice daily over a 45-day period in 34 subjects (68% female) with persistent or recurrent pain following back surgery. A secondary goal was to guide the design of future randomized controlled trials that could target responsive subpopulations. All predefined primary and secondary outcomes, including change in pain intensity (PI), physical function (Oswestry Disability Index), analgesic consumption, and overall well-being (Patient Global Impression of Change), are reported. A responder analysis (≥30% reduction in PI versus baseline) was added as a post hoc evaluation. Safety outcomes, as well as results of a cost-avoidance survey, are also summarized. Of the 30 per-protocol subjects who completed the study, 33% reported a clinically meaningful (≥30%) reduction in PI. A higher response rate (60%) was reported for subjects who had undergone discectomy prior to the trial compared to subjects who had undergone other types of surgical interventions (decompression or fusion) without discectomy. Improvements in PI were paralleled by improvements in secondary outcomes. Relative to baseline, responders reported an average 44% and 55% reduction in back PI and leg PI (respectively), and an average 13% improvement in Oswestry Disability Index scores. In the per-protocol population, 50% of responders and 12% of nonresponders reported less analgesia consumption at the end of treatment versus baseline. Sixty-seven percent of per-protocol responders and 0% of nonresponders reported clinically meaningful improvement in overall well-being on the Patient Global Impression of Change scale.