Pulsed Electromagnetic Field Therapy History, State of the Art and Future

Magnetic and electromagnetic fields are now recognized by the XXI century medicine as real physical entities that promise healing of various health problems, even when conventional medicine has failed. Today magnetotherapy provides a noninvasive, safe and easy method to directly treat the site of injury, the source of pain and inflammation, and other types of diseases and pathologies. Millions of people worldwide have received help in treatment of musculoskeletal system, as well as pain relief. Pulsed electromagnetic fields are one important modality in magnetotherapy and recent technological innovations, such as Curatron PEMF devices, offer excellent, state of the art computer controlled therapy system. In this paper the development, state of the art and future of pulsed electromagnetic field therapy are discussed. Introduction This paper was triggered by information found on Internet that a new, computerized system for pulsed electromagnetic field (PEMF) therapy has been introduced on the market. It appears that the Curatron system marks new era in the biomagnetic technology: use of computer during the planning and executing of the therapy (www.curatronic.com). It is recognized that the use of magnetic fields for therapy has a long history. Physicians from ancient Greece, China, Japan and Europe successfully applied natural magnetic materials in their daily practice. The contemporary magnetotherapy has begun immediately after the World War II by introducing both magnetic and electromagnetic fields, generated by various waveshapes of the supplying currents. Starting in Japan, this modality quickly moved to Europe, first in Romania and the former Soviet Union. During the period 1960-1985 nearly all European countries designed and manufactured own magnetotherapeutic systems. Indeed, the first book on magnetotherapy, written by N. Todorov, was published in Bulgaria in 1982 and summarizes the experience of utilizing magnetic fields for treatment of 2700 patients, having 33 different pathologies. During the 1970’s, the team of Andrew Bassett introduced a new approach for treatment of delayed fractures, that employed a very specific biphasic low frequency signal (Bassett et al., 1974,1977). This signal was allowed by FDA for application in the USA only for non-union/delayed fractures. A decade later, FDA allowed the use of pulsed radiofrequency electromagnetic field (PRF) for treatment of pain and edema in superficial soft tissues. It is now commonly accepted that weak electromagnetic fields (EMF) are capable of initiating various healing processes including delayed fractures, pain relief, multiple sclerosis and Parkinson’s disease. (Rosch, Markov, 2004). This proven benefit could be obtained by using both static and time-varying magnetic fields. Preprint: Submitted to “Electromagnetic Biology and Medicine” for publication November ‘06 2 This paper discusses only the modalities that utilize time varying low frequency EMF, known as pulsed electromagnetic fields. Therefore, a large body of research, including many clinical studies that report the successful application of static magnetic fields and high frequency EMF as well as electroporation and electrical stimulation will remain outside this paper. We suggest several excellent reviews concerning these stimulation modalities (Gardner et al., 1999; Rushton, 2002; Sluka and Walsh, 2003; Ojingwa and Isseroff, 2003; Rosch and Markov, 2004). It should be noted, that, thus far, the medical communities’ approach to magnetotherapy is as to an adjuvant therapy, especially for treatment of a variety of musculoskeletal injuries. There is a large body of basic science and clinical evidence that time-varying magnetic fields can modulate molecular, cellular and tissue function in a physiologically and clinically significant manner. (Markov, 2002; Rosch and Markov, 2004). The fundamental questions related to the biophysical conditions under which EMF signals could be recognized by cells in order to modulate cell and tissue functioning remain to be elucidated. The scientific and medical communities still lack the understanding that different magnetic fields applied to different tissues could cause different effects. The medical part of the equation should identify the exact target and the “dose” of EMF that the target needs to receive. Then, physicists and engineers should design the exposure system in such way that the target tissue received the required magnetic flux density. One should not expect, for example, that the magnetic field which is beneficial for superficial wounds, might be as good for fracture healing. Particular attention must be paid to the biophysical dosimetry which should predict which EMF signals could be bioeffective and monitor this efficiency. This raises the question of using theoretical models and biophysical dosimetry in selection of the appropriate signals and in engineering and clinical application of new PEMF therapeutic devices. Some examples for target populations The largest populations of patients that have received, or could benefit from magnetic field therapy are victims of musculoskeletal disorders, wounds and pain. Following is a summary of information for the number of people in the USA who needs help in above-mentioned areas. Five million bone fractures occur annually in the United States alone. About 5% of these became delayed or nonunion fractures (Ryaby, 1998). According to National Osteoporosis Foundation about 10 million Americans have osteoporosis and 34 million(s) of US citizens have low bone density, which put them at risk for further musculoskeletal disorders. Chronic wounds and their treatment are an enormous burden on the healthcare system, both in terms of their cost ($5 billion to $9 billion annually) and the intensity of care required. There is even more cost to society from human suffering and reduced productivity. More than 2 million people suffer from Preprint: Submitted to “Electromagnetic Biology and Medicine” for publication November ‘06 3 pressure ulcers and as many as 600,000 to 2.5 million more have chronic leg and foot wounds (Wysocki,1996). Diabetic foot ulcers are probably the most common chronic wounds in western industrialized countries. Of the millions who have diabetes mellitus, 15 per cent will suffer foot ulceration which often leads to amputation (100,000 per annum in the US alone). (Pilla, 2006) The National Institutes of Health estimate that more than 48 million Americans suffer chronic pain that results in a 65 billion loss of productivity and over $100 billion spent on pain care (Markov, 2004c). Better part of this money is spent for pain-relief medications. Recent advances in magnetotherapy suggest that carefully selected magnetic fields might be helpful in treatment of diseases as Parkinson’s, Alzheimer, as well as Reflex Sympathetic Disorders which have relatively small number of potential users. Cost and benefit of EMF therapy Improvement in even in only a small percentage of above mentioned cases would be of great benefit: less suffering, reduced expenses, decreased duration of treatment should be considered in parallel with individual and social welfare. Thus, the clinical effects of PEMF on musculoskeletal system repair are physiologically significant and often constitute the method of choice when the conventional standard of care has failed to produce adequate clinical results. PEMF modalities are usually applied directly on the targeted area of the body. Compared to regular pharmaceuticals, PEMF offers an alternative with fewer, if any, side effects. This is a tremendous advantage versus pharmaceutical treatment at which the administered medication spreads over the entire body, thereby causing adverse effects in different organs, which sometimes might be significant. One should not forget that in order to deliver the medication dose needed to treat the target tissue/organ, patients routinely receive medication dose hundreds time larger than the dose needed by the target. However, regulatory and reimbursement issues have prevented more widespread use of PEMF modalities, especially in the USA. The FDA policy toward magnetotherapy is unnecessarily restrictive. In concert with this policy, the Center for Medicare Services (CMS) for a period of time refused to allow reimbursement even for modalities cleared by FDA. It took several years of court fighting until CMS reversed its position. This was a result of the pressure from general public and physical therapy communities. In fact, the CMS has now recognized that PEMF is a plausible therapeutic modality which produces sufficient clinical outcome to permit, and reimburse for, use in the off-label application of healing chronic wounds, such as pressure sores and diabetic leg and foot ulcers (Pilla, 2006). Preprint: Submitted to “Electromagnetic Biology and Medicine” for publication November ‘06 4 PEMF Signals Today magnetic-field-dependent modalities could be categorized in six groups, but this paper is discussing only the PEMF signals (for details see Markov, 2004c). An excellent review of the physics and engineering of low frequency signals was published by Liboff, 2004. The PEMF signals in clinical use have variety of designs, which in most cases is selected without any motivation for the choice of the particular waveform, field amplitude or other physical parameters. Sinewave type signals It seems reasonable that the first and widely used waveshape is the sine wave with frequency of 60 Hz in North America and 50 Hz in the rest of the world Figure 1 Three types of sinewave signals with the same amplitude, but different frequencies Even not a subject of this paper, it should be noted that the 27.12 MHz continuous sinewave have been used for deep tissue heating in fighting various form of cancer. From the symmetrical sinewaves engineers moved to an asymmetrical waveform by means of rectification. These types of signals basically flip-flop the negative part of the sinewave into positive, thereby creating a pulsating sinewave. The textbooks usually show the rectified signal as a set of ideal semisinewaves. However, due to the impedance of the particular design such ideal waveshape is impossible to be achieved. As a result, the ideal form is distorted and in many cases a short DC-type component appears between two consecutive semi sine-waves. Preprint: Submitted to “Electromagnetic Biology and Medicine” for publication November ‘06 5 Figure 2 Example of real bridge rectified signal: a small DC component occurs between two semi sine waves and a slight distortion of the front part of semi sine wave might be observed. This form of the signals has been tested for treatment of low back pain and Reflex sympathetic disorder. However, the most successful implementation of this signal is shown in animal experiments as causing anti-angiogenic effects (Williams et al., 2001). Investigating a range of amplitudes for 120 pulses per second signal, the authors demonstrated that the 15 mT prevents formation of the blood vessels in growing tumors, thereby depriving the tumor from expanding the blood vessel network and causing tumor starvation and death. In the middle of 1980’s the Ion Cyclotron Theory was proposed by Liboff et al. (1985,1987) and shortly after that a clinical device was created based on the ICR model (Orthologics, Temple, AZ). This device is in current use for recalcitrant bone fractures. The alternating 40 μT sinusoidal magnetic field is at 76.6 Hz (a combination of Ca2+ and Mg2+ resonance frequencies). This signal, shown in has oscillating character, but due to the DC magnetic field it oscillates only as a positive signal.