The Assisi Loop is a pulsed electromagnetic field (PEMF) device that is placed on an animal and creates a weak (what’s your definition of “weak”, bro) electromagnetic field that is purported to do lots of nifty biochemical things to speed up wound healing and reduce pain. It sounds wonderful, especially since it doesn’t have any (known) side effects and it’s not a pharmaceutical (take that, Big Pharma!). The company who sells it, Assisi Animal Health, even has peer-reviewed research and claims that their technology is proven.
I’ve seen Assisi’s booths at veterinary conferences over the years, and my party-pooping skepticism (PPS) has always been curious about their claims. Usually you can suss out baloney at a product booth by bypassing the glittery prize wheel and asking for copies of the medical research. Often, there’s none, but the majority of sales reps will guarantee you that their product works and promise that there’s some really promising preliminary data. Sometimes, they’ll hand you a sketchy mouse model study. But in the case of Assissi, they actually have clinical trials of their product. Wow! Clinical trials! In peer-reviewed journals! Color me impressed! In fact, their website has quotes such as:
The results show undeniably the Loop’s ability not only to reduce pain in a severe population, but also to help target neural tissue to recover faster.
– Assisi’s Director of Clinical Development, Deirdre Chiaramonte, DVM, ACVIM, CCRT, CERP, CVA
Well why even look further than that? I mean, peer reviewed published research and words like “undeniable” should be enough to sell me, but that dang PPS is a tricky bug to squish. Curiouser and curiouser, I got my hands on these clinical studies and took a careful look. But spoiler alert, the Loop’s undeniable ability is probably being circle-shaped, not reducing pain and speeding tissue healing.
Background
PEMF devices like the Loop are supposed to trigger a biochemical cascade that ends up with good biological effects (reduced inflammation, decreased pain, better tissue healing). Because it’s noninvasive and has no known adverse effects, it’s an attractive alternative to drugs and has been investigated for a lot of animal and human health conditions. It’s far from a proven therapy though, as Steve Novella pointed out a few years ago in a post about a PEMF device for people. He highlighted that the “research” being touted by the devicemakers was preliminary and that there was a lack of clinical trials. It’s interesting to note that systematic reviews and meta-analyses of PEMF have been lukewarm (meh, meh2, and meh3).
Despite the tepidity of the science so far, there is some scientific plausibility with PEMF therapy. Sounds lukewarm enough to start the marketing campaign! But as we know, conflicting lab studies and wishy-washy systematic reviews and meta-analyses hardly prove anything. Good clinical trials are what we really need, and in the last year, two new prospective trials using PEMF in dogs were published.
Clinical trials using PEMF in dogs
These two trials both used the Assisi Loop PEMF device as an adjunctive treatment for dogs with intervertebral disc disease (IVDD, colloquially known as a “slipped disc”), which can cause paralysis of the hindlimbs. In both studies, dogs had surgery to treat IVDD and PEMF was the intervention in the treatment group. They were well-designed clinical trials: prospective, blinded, randomized, and placebo-controlled. Positive findings in both studies were attributed to PEMF treatment, however, much like the excitement over a Van Halen reunion album, this positivity could have been misplaced.
In the first study, dogs had surgery for severe IVDD and were treated with a PEMF (or placebo) device for six weeks. The researchers found less pain at the surgical site in treatments dogs, as well as better spatial limb perception (proprioception) at the end of the study. They also found that blood levels of the biomarker for neurological injury (GFAP) were lower. While this superficially sounds good, there are a number of problems.
Firstly, this was a tiny study, with only 15 dogs in total, so it’s statistically under-powered. But more problematic is that according to the paper’s own data, the control group might have had worse injuries. The authors themselves acknowledge this when talking about how GFAP (indicating spinal cord damage) was higher in the control group. Although they speculate that this may have been a therapeutic effect from the PEMF, there’s no evidence that PEMF would lower GFAP. It’s at least as likely that the higher levels in the control dogs are from more severe spinal cord injuries. In other words, worse injury in the control group, which is a plausible explanation of the data, could also have explained this and every other difference in the study that was attributed to PEMF.
But that being said, most of the measurements were not different between the groups. Gait scores (using two separate methods), time to independent walking, hopping score, pain perception, voluntary urination, and proprioception at 2 weeks were all equivalent. Pain in these dogs was assessed in three different ways, but only one showed any difference. And this assessment (mechanical sensory threshold or MST) was only measured after the PEMF treatment had been started, so there’s no baseline for pain scores before treatment.
The most statistically significant finding from this study was the improved proprioception at six weeks, but it’s hard to interpret. While proprioception is clinically useful and a good indicator of neurologic function, there were a lot of other measures of neurologic function that were not different, and proprioception was only measured at two weeks (no difference) and six weeks. Especially if the control group truly had worse injuries, this effect could easily disappear in another study. All in all, this is a small study that showed a few effects out of many investigated, and the control group might have had worse injuries, which makes interpretation difficult if not impossible.
In the second study, the dogs were treated with a PEMF device right after surgery and continued for one week. This was a larger study, with 53 dogs total, and the authors evaluated pain scores, neurologic function, time it took to start walking again, how frequently owners gave pain medications to their dogs, and incisional wound healing. They reported a significant improvement in wound healing at 6 weeks, and a significant reduction in how frequently dog owners gave pain medication.
Again, superficially appealing, who doesn’t want better wound healing and less drugs?! But alas, there are major problems here too that make these claims troublesome. First of all, it is true that the wound healing was evaluated as better at the six week mark, but skin incisions usually heal within 2 weeks, even for spinal surgery. And the differences in the scores, while statistically significant, are probably not large enough to make much of a clinical difference. There was also no difference in neurologic grades, return to function, and pain scores.
And as for the reduction in pain medication given to the PEMF dogs, the major flaw here is that the owners didn’t rate their dog’s pain differently between groups. Let’s spell this out again: the owners were told to assess their dog’s pain using an established scale, and if they felt they needed pain medication to go ahead and give it. So yes, a secondary measure (frequency of pain drugs) was different, but the actual measure (pain assessment) was not different. It’s possible that the owners were subconsciously detecting pain that the scale didn’t pick up, but it’s also possible that this is statistical noise. As evidence of PEMF reducing postoperative pain, it’s pretty flimsy.
Conclusion: ¯\_(ツ)_/¯
Both of these studies report statistically significant effects, but they’re not particularly convincing after wading into the details. It’d be great if this device worked really well, but these studies do not prove it. Assissi Animal Health is calling the results conclusive and the clinical effect proven but I think it’s far from that. Like so much in veterinary medicine, the hype and the marketing far outpace the research. For PEMF therapy, I am strongly reminded of laser therapy, which I think may be approaching the “Oh crap what have we been doing for the last 10ish years?” phase (Skeptvet articles on laser). A mountain of data doesn’t equal a proven clinical therapy. There might be an effect from PEMF, but that’s not the only or even the most likely explanation for the results of these studies, in my opinion. Is it crazy to wait until we get some more convincing evidence before embracing PMEF?
Also, thanks for reading this somewhat dry assessment of ambiguous clinical research, because it was almost 0% fun, here’s your reward for getting to the end.