Pulsed electromagnetic field (PEMF) therapy can non-invasively treat a variety of pathologies by delivering electric and magnetic fields to tissues via inductive coils. The electromagnetic fields generated by these devices have been found to affect a variety of biological processes and basic science understanding of the underlying mechanisms of action of PEMF treatment has accelerated in the last 10 years. Accumulating clinical evidence supports human and Veterinary applications of PEMF therapy for specific clinical indications including bone healing, wound healing, osteoarthritis and inflammation, and treatment of post-operative pain and edema. While there is some confusion about PEMF as a clinical treatment modality, it is increasingly being prescribed by veterinarians. In an effort to unravel the confusion surrounding PEMF devices, this article reviews important PEMF history, device taxonomy, mechanisms of action, basic science and clinical evidence, and relevant trends in veterinary medicine. The data reviewed underscore the usefulness of PEMF treatment as a safe, non-invasive treatment modality that has the potential to become an important stand-alone or adjunctive treatment modality in veterinary care.
Introduction
Pulsed electromagnetic field (PEMF) therapy is a non-invasive, non-thermal treatment that involves pulsing electromagnetic fields in tissue to promote healing (Strauch et al., 2009). Veterinary applications of PEMF therapy approved by the U.S. Food and Drug Administration (FDA) include treatment for non-union fractures and cleared to treat post-operative pain and edema, osteoarthritis, plantar fasciitis and more. Implementation of PEMF therapy in veterinary medicine is increasing. Pathologies that are often treated with PEMF devices include bone fractures, inflammation and arthritis, pain, edema, and chronic wounds. Though there is a growing body of basic and clinical evidence in support of PEMF treatment as a therapeutic modality, veterinary practitioners and animal owners report significant confusion about PEMF devices largely due to the number of different types of devices and the varying amounts of evidence that support each type of device. This lack of clarity regarding the PEMF modality is furthered by poor dissemination of data on mechanisms of action and a wide variety of unsubstantiated claims that are used for marketing purposes. In an effort to unravel the confusion surrounding PEMF devices, this article reviews important PEMF history, device taxonomy, mechanisms of action, basic science and clinical evidence, and relevant trends in veterinary medicine. The goal of this overview is to provide readers with a clearer understanding of the PEMF treatment modality, with an emphasis on recent PEMF technologies that are rooted in basic science and clinical research and are well-positioned to augment veterinary care.
History
Electromagnetic field devices have been used therapeutically for more than a century and for a variety of applications (Fig. 1) (Strauch et al., 2009). Historically, most devices have had a wide range of operating modes and were largely promoted without scientific evidence or validation. The era of modern PEMF technologies began in the 1930s when a vacuum tube-based diathermy machine, a radio-frequency electromagnetic device used to deliver heat deep into tissue, was adapted to produce little to no heat. This was accomplished by reducing the duty cycle of the diathermy device, or the percentage of the electromagnetic signal’s on-off cycle in which the signal is active, to about 4%. These new non-thermal devices were purported to have therapeutic effects in wound healing and treatment of pain, though via unknown mechanisms at the time.
Commercial distribution of these “non-thermal diathermy” devices started in 1950 (Al-Mandeel and Watson, 2008). In parallel work during the 1970s, clinician researchers began to employ direct electrical currents to treat non-union fractures, using electrodes surgically implanted in bone (Paterson et al., 1977). By the late 1970s, implanted electrodes were being replaced with non-invasive inductive antennas (Bassett et al., 1977). During that period PEMF was successfully used to treat delayed and non-union fractures in Beagles and, shortly thereafter, humans. After extensive clinical research, by the early 1980s low-powered PEMF devices called bone growth stimulators (BGS) were approved by the U.S. FDA for human use (Fig. 2) (Bassett et al., 1982). Subsequently, in the 1990’s, a next generation class of PEMF devices was developed for treating soft-tissue instead of bone. These devices were solid-state and smaller, improving upon the cumbersome large vacuum tube models.
Osteoarthritis
A non-targeted PEMF device (high frequency) was recently shown to improve pain and increase function in a RCT involving patients with knee osteoarthritis (Bagnato et al., 2016). An earlier study, investigating a targeted PEMF device therapy (high frequency) for knee osteoarthritis also showed significant reductions in pain (Nelson et al., 2013). The comparable study design and clinical populations in these trials lend to a meaningful comparison of use and effectiveness for the non-targeted and targeted PEMF devices. The results show that after one month of treatment, the targeted PEMF device, developed explicitly to reduce inflammation, produced a more pronounced reduction in the visual analog scale for pain (VAS) and did so at significantly lower doses (12 h daily vs. 30 mins daily) (Table 2). As mentioned above, a key driver for this difference in efficacy is the device waveform, which for the targeted PEMF device generates an electric field 7 times stronger than that of the non-targeted PEMF device.
Veterinary-focused research studies have also demonstrated benefits of PEMF treatment for osteoarthritis. A non-targeted PEMF device (low frequency) was found to lessen clinical signs of osteoarthritis in dogs after 20 18-minute treatments (Pinna et al., 2012). While this study lacked a sham device control group, the PEMF treatment was compared to treatment with firocoxib, a non-steroidal anti-inflammatory drug, and PEMF treatment was found to outperform drug treatment in long term follow up. Another study found that a non-targeted PEMF device (low frequency) applied for 1 h on 9 consecutive days reduced osteoarthritis pain in dogs as assessed by their owners. Animal owners who provided self-report of clinical data in this study, however, were not blinded, which underscore a need for study replication with a more rigorous design (Sullivan et al., 2013).
Inflammation, pain, and edema
The acute inflammatory cascade that occurs after tissue injury, whether surgical or traumatic in origin, is an important part of the recovery process to fight infection, promote tissue remodeling, and initiate healing. High levels of inflammation, both acute and chronic, often contribute to pain and edema at the site of injury. Several studies support the effectiveness of PEMF and targeted PEMF as treatments for inflammation, pain and swelling.
Basic science studies conducted by Kubat and colleagues found that non-targeted PEMF treatment (high frequency) was able to induce gene expression changes associated with resolution of inflammation in human cells (Kubat et al., 2015). Another non-targeted PEMF device (high frequency) study reported that continuous PEMF treatment for 7 days after breast surgery resulted in significantly lower VAS pain scores and fewer narcotic pain pills taken (Rawe et al., 2012).
Four double-blind, randomized, controlled human trials have been conducted using targeted PEMF (high frequency) in patient populations who underwent breast augmentation, bilateral mastectomy and reconstruction, breast reduction, and transverse rectus abdominus breast reconstruction, respectively (Heden and Pilla, 2008; Rohde et al., 2010; Rohde et al., 2015). In all of these studies, targeted PEMF therapy (as compared with sham treatment) was observed to significantly reduce both pain and narcotic pain medication use following these surgical procedures. The magnitude of the clinical effects observed in a study involving breast reduction surgery patients was particularly notable (Rohde et al., 2010). Targeted PEMF was applied for 20 min every 4 h after surgery and was found to reduce pain by 50%, reduce the concentration of the inflammatory cytokine interleukin-1beta at the wound site by 40% and, importantly during this period of opioid crises, reduce the use of narcotic pain medication by 50%.
PEMF devices have been applied in veterinary trials to assess efficacy of post-operative pain reduction. In a controlled study, a non-targeted PEMF device (low frequency) was applied with or without morphine to female dogs after ovariohysterectomy for 20 min every 40 min over a period of 6 h after surgery. This study failed to find a benefit of PEMF alone when compared to untreated controls (Shafford et al., 2002). A more recent randomized, sham-controlled study evaluated the effects of a targeted PEMF device (high frequency) therapy in dogs with acute intervertebral disc extrusion and paraplegia being treated with spinal decompression surgery. Targeted PEMF treatment was applied for 15 min every 2 h for two weeks then twice daily for four weeks. Treated dogs exhibited significant reductions in surgical incision site pain, lower concentrations of inflammatory biomarkers, and improved proprioceptive function compared to controls (Zidan et al., 2018).
Soft tissue wound healing
Clinical studies examining the effects of PEMF therapy on soft tissue and wound healing have demonstrated that treatment accelerated the healing of chronic wounds such as pressure sores and diabetic leg and foot ulcers. FDA-cleared or -approved PEMF devices are reimbursed by Centers for Medicare and Medicaid services as safe, effective treatments for chronic wounds and several studies support the effectiveness of PEMF for this indication (Kloth et al., 1999; Mayrovitz and Larsen, 1995; Salzberg et al., 1995; Stiller et al., 1992; Strauch et al., 2007). In a RCT conducted with paraplegic veterans with sacral ulcers, a single 30 min non-targeted PEMF treatment (high frequency) every weekday for a month resulted in 64% wound closure in the active treatment arm as compared to a 7% increase in wound size in sham treatment arm (Kloth et al., 1999).
To investigate how PEMF therapy enhanced wound repair, experiments were carried out to examine potential treatment effects on vascular function, an important aspect of wound healing. A study by Roland and colleagues found that non-targeted PEMF treatment accelerated the growth of new blood vessels by 5-fold in an arterial loop transfer in rats (Roland et al., 2000). In a subsequent trial, native arterial blood supply to a rodent tissue flap was cut off and PEMF was applied to enhance vascular performance. Whereas the sham treatment cohort had virtually complete flap failure, animals treated with PEMF twice daily for 30 min over 8 weeks exhibited significant vascularization and virtually complete flap survival (Weber et al., 2004). These data provide proof of principle that PEMF interventions are effective at promoting wound healing in part because of enhanced vascularization and associated tissue perfusion and oxygenation, all of which are important for wound repair.
Psychiatric & neurological disorders
Development of drug therapies for psychiatric and neurological disorders has been remarkably unsuccessful. Lack of effective treatment is most obvious for conditions like major depressive disorder, brain trauma, stroke, Alzheimer’s disease, and a number of other severe disorders.
Preliminary research studies have demonstrated the utility of several PEMF therapies for addressing some of the unmet treatment needs for these conditions affecting the brain. PEMF appears to be an advantageous therapeutic strategy, particularly because the electromagnetic fields generated by the devices are able to penetrate the head and reach the brain tissue being targeted. In vitro studies and studies in animals have demonstrated that PEMF can promote healing in models of stroke, traumatic brain injury, brain cancer, and Alzheimer’s disease (Arendash et al., 2010; Grant et al., 1994; Mukthavaram et al., 2015; Pena-Philippides et al., 2014; Rasouli et al., 2012). Many of these technologies are in the process of transitioning into Phase I and II clinical trials in humans to assess safety and efficacy.
PEMF treatment may have valuable applications in the treatment of small and large animal mood and behavioral disorders. This is supported by studies showing that targeted PEMF can reduce inflammatory cytokine production in the brains of laboratory animals after brain injury (Rasouli et al., 2012). Inflammatory tone is believed to be an important driver of behavior in both animals and humans (Haroon et al., 2012). Additional research in humans has found that other forms of electromagnetic intervention can effectively reduce clinical signs of depression (Pascual-Leone et al., 1996; Rohan et al., 2014). While PEMF may be useful tool for veterinary treatment of behavioral disorders, this is a new area of investigation and research studies focused on specific conditions will need to be carried out before any conclusions are drawn.
Safety
The known dangers of non-ionizing electromagnetic fields and radiofrequency fields are due to thermal effects (e.g., heating caused by microwave radiation). The Institute for Electrical and Electronics Engineers Standards for Radio Frequency Electromagnetic Field Exposure concluded that “A review of the extensive literature on radiofrequency biological effects, consisting of well over 1300 primary peer reviewed publications published as early as 1950, reveals no adverse health effects that are not thermally related”. Non-invasive, non-thermal PEMF technologies have a long history of clinical use. Since the late 1990s, PEMF devices are estimated to have delivered over 3,000,000 treatments without reports of side effects or significant adverse events. Underscoring this point, two general reviews of clinical PEMF use found no evidence of significant adverse events nor side-effects in the literature reviewed (Guo et al., 2011; Guo et al., 2012).
Current trends in veterinary medicine
Both small and large animal veterinary practices are adapting to the currently evolving animal care landscape. Unsurprisingly, the priorities of pet owners and large animal caretakers are critical drivers of change and include preference for non-invasive, non-toxic, at-home treatments that are as feasible and well-tolerated as possible. There is also increasing emphasis on rehabilitation for chronic conditions and postoperative recovery and “prehabilitation” to reduce the risk of injury or chronic disease, or to condition an animal before surgical repair, competition or work.
Animal wellness is also an underlying theme for many of the new initiatives that are being adopted by leading veterinary practices. For example, recent research innovations have led to the development of validated instruments for measuring acute and chronic pain in dogs and cats, lending to pain-management care focused on improving quality of life (Brondani et al., 2011; Wiseman-Orr et al., 2006). Another effort, led by Dr. Martin Becker of Fear FreeSM, aims to reduce animal anxiety during veterinary visits, improving the experience for both animals and pet owners and also fostering improved compliance and quality of care.
The heightened focus on animal wellness and evolving priorities of pet owners have also contributed to veterinary treatment plans involving multiple modalities of therapy applied simultaneously or in sequence. Combined modes of treatment can include drugs, surgical intervention, device therapy, nutrition, exercise, manual therapy and behavior change, and are intended to both optimize clinical outcomes and minimize adverse effects of treatment. Multipronged treatment plans are particularly valuable for vexing yet common conditions such as osteoarthritis-associated pain, in which NSAIDs, steroid drugs, or opiates are prescribed but can be poorly tolerated and are ill-suited as long-term solutions for symptom management. In contrast, because of the multiple signaling pathways at work, PEMF not only address pain but has been shown to promote resolution of pathology by promoting blood flow, secretion of growth factors, and other pathways that can contribute to healing.
Apart from pharmacologic agents, a number of non-invasive devices have been developed and clinically implemented to treat inflammatory conditions and pain in both humans and animals. These technologies rely upon electromagnetic and mechanical stimulation of tissue to reduce symptomatology and promote healing. As these technologies represent a non-pharmaceutical alternative or adjunct to NSAIDs, they have been dubbed NPAID® or non-pharmaceutical anti-inflammatory devices.
PEMF devices, described above, provide a non-invasive form of treatment, both in-office and at home, that has been repeatedly found to be safe, effective, and affordable. These characteristics are attractive for both monotherapy and as an adjunct to traditional standard of care. PEMF is commonly used adjunctively with NSAIDs and steroidal drugs to augment clinical benefit or to facilitate administration of lower doses of drugs, underscoring the trend towards multimodal treatment.
Many veterinary practices also use Class III or IV lasers as an in-office treatment for strains, sprains, osteoarthritis, and wound healing. Some lasers have also been shown to reduce both pain and inflammation (Pryor and Millis, 2015). The risk of retinal and thermal tissue damage from these devices, however, generally restricts their use to certified medical professionals. Lastly, though not anti-inflammatory in mechanism, therapeutic ultrasound, which relies on high frequency sound wave treatment of tissue, also has a long history of veterinary use and is gaining further traction as research demonstrates its utility in treating stiffness, pain, and wounds (Kavros et al., 2008; Morishita et al., 2014; Zhang et al., 2016).
Conclusions
Early PEMF devices lacked systematic evidence. Natural skepticism of the utility of PEMF was compounded by unscrupulous marketing, unsubstantiated claims, and unproven, unregulated devices. However, in the last 30 years, clinicians and scientists have developed a significant volume of research involving cell models, animals, and humans demonstrating the biological effects and clinical value of PEMF treatment for a variety of conditions. Veterinary applications of PEMF therapy has improved significantly, particularly in the areas of pain management, mitigation of inflammation, bone healing, and wound healing. The most rigorous and compelling research has been conducted on devices that are regulated by the FDA.
Here we have reviewed PEMF history, regulatory status, and key studies and cases that illustrate clinical utility. These data underscore the usefulness of PEMF treatment as a safe, non-invasive treatment modality that has the potential to become an important stand-alone or adjunctive treatment modality in veterinary care. As the field of veterinary medicine continues to mature, further development and implementation of PEMF and other NPAID technologies will serve an important role in multimodal treatment strategies that aim to maximize animal wellness.
You can read the complete study here https://www.sciencedirect.com/science/article/pii/S003452881830208X?via%3Dihub.
To learn more about PEMF therapy, including how you can get a PEMF device for your home personal use, please contact us here.