TENS has a complicated, awesome cousin: pulsed electromagnetic field therapy
Recently I published the first new feature article for PainScience.com in quite a while: Zapped! Does TENS work for pain? The peculiar popularity of being gently zapped with electrical stimulation therapy. I’ve now added an interesting new section to it about pulsed electromagnetic field therapy (PEMF). It’s amazingly positive, and inspired by some fresh science …
PEMF is clearly kin to TENS, part of the electrotherapy family. And yet it’s a different beast, much more exotic, with a more mysterious mechanism of action. PEMF is hypothesized to directly stimulate cellular repair, and not for nothing: it seems to really do that, and the effect is almost magical, speeding up bone fracture healing, and even restoring it in cases where healing has failed completely.
The scientific reviews of PEMF used for this purpose are unstintingly positive.1Shi Hf, Xiong J, Chen Yx, et al. Early application of pulsed electromagnetic field in the treatment of postoperative delayed union of long-bone fractures: a prospective randomized controlled study. BMC Musculoskelet Disord. 2013;14:35. PubMed #23331333. PainSci #53405. “Fracture patients treated with an early application of PEMF achieved a significantly increased rate of union and an overall reduced suffering time compared with patients that receive PEMF after the 6 months or more of delayed union, as described by others.”
So PEMF has been used on fractures for a long time now, but only recently have PEMF devices gotten small and cheap enough for consumers and less critical medical applications. Can they work on more ordinary problems? Like arthritis? Something TENS can only treat effectively with just the right settings and variables, that no one can seem to confirm? Apparently so …
The evidence is actually promising (more than I’m used to in musculoskeletal medicine)
Although the evidence for this isn’t unanimous, some of the best and most recent PEMF trials are unambiguously positive.3Bagnato GL, Miceli G, Marino N, Sciortino D, Bagnato GF. Pulsed electromagnetic fields in knee osteoarthritis: a double blind, placebo-controlled, randomized clinical trial. Rheumatology (Oxford). 2016 Apr;55(4):755–62. PubMed #26705327. PainSci #53404.
This was a rigorous test of wearable pulsed electromagnetic fields (PEMF) for older patients with osteoarthritis of the knee: moderate to severe cases with X-ray evidence and pain of at least 4/10 for more than six months, despite maximum tolerated medication. Sixty patients wore either a real PEMF device for 12 hours per day, or a fake; neither they nor the researchers knew who got real PEMF (double-blind). PEMF is particularly easy to test properly, because it causes no sensation, making it much easier to compare to an active placebo.
The placebo devices do not emit a radiofrequency electromagnetic field but are identical to the active devices, including a light-emitting diode light showing operation. The energy from the active device is not felt by the user, and the active device cannot be distinguished in any way from the placebo device.
Their pain and knee function were compared. PEMF won decisively: the real-PEMF patients enjoyed a 25.5% reduction in pain, compared to a 3.6% reduction for the fake-PEMF patients. Knee function improved as well, though not as much. I hope everyone got a real PEMF device at the end!
That’s compelling evidence. Not that there aren’t caveats. There are always caveats.
Although the results seem straightforwardly positive, the authors explain that “some of the effects of this therapeutic approach might be derived from neuromodulation of the pain mechanism”: that is, it might be “just” a pain-killer, as opposed to actually helping to heal arthritic cartilage. (But killing pain effectively would be a pretty good second place.)
Also, the device used is extremely low-power (a tiny battery) — so low that it's quite implausible that it could possibly have a therapeutic effect, and these results need replication to be believed, no matter how good the study seems.
The Bioelectronics Corporation manufactures PEMF devices, and provided the pulsed electromagnetic fields and placebo devices, but they did not fund the study and the authors declared no conflict of interest. These devices are widely available to consumers: see ActiPatch®.