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Veterinary Application of Pulsed Magnetic Field Therapy

by Dr. D. C. Laycock Ph.D. (Med. Eng.); MIPEM*; B.Ed. (Hons)(Phys. Sciences); MBES:

CGLI (Ind. Electronics); Consultant Clinical Engineer, Westville Associates and Consultants (UK)

and M. Laycock: B.A. (Sciences); P.G.C.E.; Research Co-ordinator

Although the therapeutic use of pulsed magneticfields has long been in existence, understanding of its mode of actionhas been poorly understood. As early as 1940, Nagelshmidt proposed thatits action was at the cellular level and this has now been supported byresearch. It has been shown that damaged cells have a reduced negativecharge, with subsequent effect on the flow of ions. This causes abuild-up of fluid and prevents the normal cellular metabolism fromtaking place. Research by Bauer and more recently by Sansaverino(1980), confirmed that pulsed electromagnetic fields can restore theionic balance and return the cell to its normal functions.

Initially, pulsed magnetic fields were appliedmainly to fractures, where it was shown that they could bring about areduction in the time needed for resolution of the fractures. It hasbeen shown that under the influence of a pulsed magnetic field,osteoblasts are attracted to treatment sites, where small eddy currentsare then induced into trace elements of ferro-magnetic material withinthe bone. Also, work by Madronero has shown that calcium salts arepurified, hence bone crystals become stronger. More recently, researchby Bassett has been investigating the wider applications of pulsedmagnetic fields in the area of orthopaedics.

Bassett also foresaw the extension of pulsedmagnetic field therapy to other areas of medicine. This has now takenplace, with an increase in scientific research and clinical trials inthe UK, and throughout Europe, Russia and the USA.

The range of applications has covered :-

Treatment of vascular disorders (Steinberg 1964)

Reduction of inflammation and oedema (Golden et al 1980)

Enhancement of the rate of healing in skin grafts (Golden et al 1981)

Reduction of pain (Warnke 1983)

Treatment of neuropathy (Lau)

Nerve regeneration (Hayne)

Reduction in symptoms of Multiple Sclerosis (Guseo 1987)

Research into these and other areas have shown goodrates of success, with no detrimental side effects. For optimumresults, low-frequency sustained pulsed magnetic fields should beapplied, with specific problems responding best to specificfrequencies. For example, pain can be blocked using a base frequency of200Hz as this brings about hyperpolarisation of nerve cells andinhibits transmission of pain signals. For wound healing, a basefrequency of 50Hz is most effective, with a pulse rate of 17.5Hz.

The role of Pulsed Magnetic Field therapy in veterinary practice

Initially, pulsed magnetic field therapy was usedprimarily in treating horses for resolution of back and leg injuries.This was followed by widespread use with greyhounds, since these incurfrequent sprains, ligament injuries and fractures, all of which respondwell to pulsed magnetic field therapy. It is now used with otheranimals for similar injuries and has also been used to improvemetabolism. The range of animals treated is wide - from elephants tobuzzards! Pulsed magnetic field therapy has been found to beparticularly effective in treating leg and wing fractures of smallbirds, as they often are difficult to splint and, in the worst cases,difficult to pin because of splintering of small bones. These injuriesshow a good response given daily treatment with pulsed magnetic fieldtherapy.

The use of a 200Hz base frequency as a pain blockalso has been beneficial in facilitating the examination of an injuredanimal. Practitioners have found that an initial 10 minute treatmentreduces an animal's distress, so that it will then tolerate furtherhandling in order to apply treatment or to enable the manipulation ofan injury.

German shepherd dogs are noted for sufferingsymptoms which resemble those of Multiple Sclerosis. In the UK, somesuccess has been achieved by treating these symptoms with pulsedmagnetic field therapy. There is also evidence from research that nerveregeneration has been achieved under the influence of pulsed magneticfields.

Once a diagnosis has been made and the desiredtherapeutic frequency determined, pulsed magnetic field therapy issimple to apply and can safely be administered by the owner. This meansthat treatment can be given more than once a day on a regular basisbetween visits to the surgery - thus speeding up the rate of healingand reducing demands on the time of the practitioner. In the UK,trained animal therapists operate under the direction of veterinarysurgeons to provide pulsed magnetic field therapy as part of aphysiotherapy programme for animals. Students come from all over theworld to a training centre to be taught the methods and how to use theequipment to optimum effect.

Additional Research Click Here 

Pulsing electromagnetic field therapy in nerve regeneration: an experimental study in the cat.

A multidisciplinary approach to the study of peripheral nerveregeneration in the cat has been presented. The purpose of this workhas been to determine if pulsing electromagnetic field (PEMF) therapycan enhance peripheral nerve regeneration after injury. In equal groupsof animals, two types of pulsing electromagnetic field treatment werecompared with untreated controls. All animals underwent quantitativeelectrophysiologic and morphologic assessment at the area of injury. Inaddition, muscle fibre sizing in the periphery and retrograde labelingof anterior horn motoneurons with horseradish peroxidase were studied.Results have shown no statistical differences between the groups inelectrophysiologic or morphologic parameters. However, in animalstreated with a pulse-burst electromagnetic field there was astatistically significant improvement in the labelling and localizationof anterior horn cells in the central nervous system. These resultsindicate that pulse-burst electromagnetic radiation can increase thenumbers of motor neurons that re-establish appropriate connections tothe periphery after nerve injury. Orgel MG,
Orgel MG, O'Brien WJ, Murray H. Plast Reconstr Surg


Effects of pulsed electromagnetic fields on bone healing in a rabbit tibial osteotomy model.

OBJECTIVE: The purpose of this study was to determine the effect ofpulsed electromagnetic field (PEMF) exposure on healing tibialosteotomies in New Zealand White rabbits. DESIGN: One-millimeter Giglisaw osteotomies were stabilized by external fixation. One day aftersurgery, rabbits were randomly assigned to receive either no exposure(sham control) or thirty minutes or sixty minutes per day oflow-frequency, low-amplitude PEMF. Radiographs were obtained weeklythroughout the study. Rabbits were euthanized at fourteen, twenty-one,or twenty-eight days, and tibiae underwent either destructive torsionaltesting or histologic analysis. To determine the baseline torsionalstrength and stiffness of rabbit tibiae, eleven normal intact tibiaewere tested to failure. RESULTS: Sixty-minute PEMF-treated osteotomieshad significantly higher torsional strength than did sham controls atfourteen and twenty-one days postoperatively. Thirty-minutePEMF-treated osteotomies were significantly stronger than sham controlsonly after twenty-one days. Normal intact torsional strength wasachieved by fourteen days in the sixty-minute PEMF group, by twenty-onedays in the thirty-minute PEMF group, and by twenty-eight days in thesham controls. Maximum fracture callus area correlated with the time toreach normal torsional strength. CONCLUSION: In this animal model,low-frequency, low-amplitude PEMF significantly accelerated callusformation and osteotomy healing in a dose-dependent manner.
Fredericks D. et.al. Uni of Iowa College of Medicine, J Orthop Trauma


Pulsed electromagnetic fields simultaneously induceosteogenesis and upregulate transcription of bone morphogeneticproteins 2 and 4 in rat osteoblasts in vitro.

Pulsed electromagnetic fields (PEMF) are successfully employed in thetreatment of a variety of orthopaedic conditions, particularly delayedand nonunion fractures. In this study, we examined PEMF effects on invitro osteogenesis by bone nodule formation and on mRNA expression ofbone morphogenetic proteins 2 and 4 by reverse-transcriptase polymerasechain reaction (RT-PCR) in cultured rat calvarial osteoblasts. PEMFexposure induced a significant increase in both the number (39% overunexposed controls) and size (70% larger compared to unexposedcontrols) of bone-like nodules formed. PEMF also induced an increase inthe levels of BMP-2 and BMP-4 mRNA in comparison to controls. Thiseffect was directly related to the duration of PEMF exposure. Thisstudy shows that clinically applied PEMF have a reproducible osteogeniceffect in vitro and simultaneously induce BMP-2 and -4 mRNAtranscription. This supports the concept that the two effects arerelated.
Bodamyali T. et.al. Postgraduate Medicine, Uni of Bath, UK Biochem Biophys Res Commun


Effects of electromagnetic stimulation on the functional responsiveness of isolated rat osteoclasts.

We report the effects of pulsed electromagnetic fields (PEMFs) on theresponsiveness of osteoclasts to cellular, hormonal, and ionic signals.Osteoclasts isolated from neonatal rat long bones were dispersed ontoeither slices of devitalised cortical bone (for the measurement ofresorptive activity) or glass coverslips (for the determination of thecytosolic free Ca2+ concentration, [Ca2+]). Osteoclasts were alsococultured on bone with osteoblastlike, UMR-106 cells. Bone resorptionwas quantitated by scanning electron microscopy and computer-assistedmorphometry. PEMF application to osteoblast-osteoclast cocultures for18 hr resulted in a twofold stimulation of bone resorption. Incontrast, resorption by isolated osteoclasts remained unchanged in thepresence of PEMFs, suggesting that osteoblasts were necessary for thePEMF-induced resorption simulation seen in osteoblast-osteoclastcocultures. Furthermore, the potent inhibitory action of the hormonecalcitonin on bone resorption was unaffected by PEMF application.However, PEMFs completely reversed another quite distinct action ofcalcitonin on the osteoclast: its potent inhibitory effect on theactivation of the divalent cation-sensing (or Ca2+) receptor. For theseexperiments, we made fura 2-based measurements of cytosolic [Ca2+] insingle osteoclasts in response to the application of a known Ca2+receptor agonist, Ni2+. We first confirmed that activation of theosteoclast Ca2+ receptor by Ni2+ (5 mM) resulted in a characteristicmonophasic elevation of cytosolic [Ca2+]. As shown previously, thisresponse was attenuated strongly by calcitonin at concentrationsbetween 0.03 and 3 nM but remained intact in response to PEMFs. PEMFapplication, however, prevented the inhibitory effect of calcitonin onNi2+-induced cytosolic Ca2+ elevation. This suggested that the fieldsdisrupted the interaction between the calcitonin and Ca2+ receptorsystems. In conclusion, we have shown that electromagnetic fieldsstimulate bone resorption through an action on the osteoblast and, byabolishing the inhibitory effects of calcitonin, also restore theresponsiveness of osteoclasts to divalent cations.
Shankar V. et.al. Center for Osteoporosis and Skeletal Aging, Philadelphia J Cell Physiol


Pulsed electromagnetic fields in experimental cutaneous wound healing in rats.

Electromagnetic fields are now being used in many diseases suchas osseous, ligamental, cartilaginous, or nervous reparation, diabetes,and myocardial or cerebral ischemia. Although many publications showthe usefulness of magneto-therapy, discrepancies exist about theutility of electromagnetic fields in skin wound healing. The objectiveof this work was to study the effect of pulsed electromagnetic fieldson wound healing in rats. Twenty-two male Wistar rats were used; acircular lesion was made in the back of each animal. They were dividedinto three groups: group C (control) with sham treatment (n = 8), groupNF, treated with topical nitrofurazone solution (n = 7), and groupPEMF, treated with pulsed electromagnetic fields of 20 mT (n = 7). Thetreatments were 35 minutes twice a day. The absolute and relativevalues of the area and perimeter of the wounds showed significantlylower values in the PEMF group at days 7, 14, and 21 compared withthose in group C (p < 0.01, analysis of variance), whereas the PEMFgroup showed significantly lower values at day 21 only compared withthe NF group (p < 0.01, analysis of variance). The results suggest asignificant beneficial stimulation in the wound healing process in ratstreated with PEMF, which could lead to the development of a practicaltool for research and clinical use.
Patino O. et.al. Postgraduate Reconstr. and Plastic Surgery, Uni del Salvador J Burn Care Rehabil


Enhancement of functional recovery following acrush lesion to the rat sciatic nerve by exposure to pulsedelectromagnetic fields.

Previous studies showed that exposure to pulsed electromagneticfields (PEMF) produced a 22% increase in the axonal regeneration rateduring the first 6 days after crush injury in the rat sciatic nerve. Weused the same injury model to assess the effect on functional recovery.The animals were treated with whole body exposure to PEMF (0.3 mT,repetition rate 2 Hz) for 4 h/day during Days 1-5 while held in plasticrestrainers. Functional recovery was serially assessed up to PostinjuryDay 43 using recently described video imaging of the 1-5 toe spread andthe gait-stance duration. Footprint analysis was also used withcalculation of a sciatic function index. Those animals treated withPEMF had improved functional recovery, as compared to sham controls,using the tests for video 1-5 toe spread and gait-stance duration (P =0.001 and P = 0.081, respectively). This effect was found throughoutthe 43-day recovery period. No effect was found using the sciaticfunction index. This study confirms that functional recovery afternerve crush lesion is accelerated by PEMF and has broad implicationsfor the clinical use of these fields in the management of nerveinjuries.
Walker J. et.al. Orthopaedic Surgery, Uni of Kentucky Exp Neurol


Effect of PEMF on fresh fracture-healing in rat tibia.

The present experiment was designed to find out whether PEMFcan act as a healing agent on induced fracture of rat tibia. Eightyrats were taken for this experiment. Under general anaesthesiamid-shaft of tibia and fibula of all rats were osteotomied,Intramedullary nailing was done for proper alignment of the fracturedfragments. The animals were then divided into two groups: group-1 andGroup-II. Each group contained forty animals. Out of these fortyanimals twenty were treated as experimental and twenty as control. Fromthe third day of osteotomy, PEMF was applied to experimental ratsaround the osteotomy sites for a period of nine hours a day. PEMF wasnot applied to the control rats. The animals of group-1 and group-IIwere sacrificed after applied one week and three weeks of PEMF,respectively. Radiological and microscopical examination of the calluswere performed. Gross and microscopic measurements of the callus werestatistically analysed. The growth of callus was taken as a criterionof fracture healing. The results of the present experiment revealedsignificant enhancement of fracture healing in group-I. The results ofthe radiological evaluation of group-II experimental animals were alsoconsistent with the morphological analysis. It was concluded thathealing of fractured rat tibia was enhanced by the application of PEMFand this effect of PEMF was more pronounced at the end of third week.
Sarker A. et.al. Dep. of Path., Okayama Uni, Japan. Bangladesh Med Res Counc Bull