interferential current therapy · repeated until no further accommodation is observed. mostpatients...

Br. J. Sp. Med; Vol 24, No. 2

Physiotherapy treatment modalities

Interferential current therapyG. C. Goats, PhD, MCSPDepartment of Physiotherapy, The Queen's College, Glasgow

IntroductionTherapists often use transcutaneous electrical stimu-lation to treat their patients. They can selectalternating current of various frequencies or directcurrent applied continuously or as a train of pulses.Each type of current has both advantages anddisadvantages when used therapeutically.

Direct current and low-frequency alternating cur-rents (> 1 kHz) encounter a high electrical resistancein the outer layers of the skin. This makes thetreatment of deep structures painful because a largetranscutaneous current must flow so that adequatecurrent passes deeply. Alternating currents ofmedium (>lkHz to <lOkHz) or high frequency(>lOkHz) meet little resistance (due to a markedreduction in the effects of skin capacitance uponcurrent flow) and penetrate the tissues easily,although such currents generally oscillate too rapidlyto stimulate the tissues directly AThese difficulties were overcome in the early 1950s

with the development of interferential current thera-py. The equipment produces two alternating currentsof slightly differing medium frequency and is usedwidely to induce analgesia, elicit muscle contraction,modify the activity of the autonomic system, promotehealing, and reduce oedema5.

Use of interference effects in therapyWhen two or more sinusoidal currents alternate atthe same frequency, rising and falling at exactly thesame time, they are said to be in phase. Wavesbecome out of phase when they are a half wavelengthout of step and the rising segment of one coincideswith the falling segment of the other. Waves in phaseinterfere constructively to produce a resultant wavewith an amplitude greater than that of either of theoriginals. Waves out of phase interact in a similar waybut interfere destructively to cancel each other out(Figure 1).

Interference also occurs between waves of slightlydiffering frequency. As one wave peak 'catches up'with the other, constructive interference causes anincrease in the amplitude of the resultant wave,

Address for correspondence: G. C. Goats PhD, MCSP, Departmentof Physiotherapy, The Queen's College, 1 Park Drive, Glasgow G36LP, UK

© 1990 Butterworth-Heinemann Ltd0306-4179/90/020087-06

which declines subsequently as the waves again driftout of phase and interfere destructively. The rate atwhich the amplitude of the resultant rises and falls isequal to the difference in frequency present betweenthe two original waves and is called a 'beatfrequency'. This process is an example of amplitudemodulation'.

Interferential current therapy exploits this principleof interference to maximize the current permeatingthe tissues whilst reducing to a minimum unwantedstimulation of cutaneous nerves.The principal components of an interferential unit,

illustrated in Figure 2, are a pair of signal generators,the output of one oscillating at the fixed frequency of4000Hz whilst the other is variable in frequencybetween 4000 and 4250 Hz. These signals are thenamplified to a therapeutically useful intensity. The

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Interferential current therapy: C. G. Goats

Figure 2. An interferential therapy unit with vacuum andflexible carbon rubber electrodes

variable-frequency oscillator can sweep automaticallybetween one pre-set frequency and another, thusproducing a range of beat frequencies that yieldseveral therapeutic effects, all of which may beobtained with a single application4.Two pairs of electrodes, conveying separately the

amplified output of the oscillators, are aligned on theskin so that the currents flowing between each pairintersect and interfere within the structure to betreated. A resultant current of low frequency isgenerated that alternates at 0-250 Hz. The precisefrequency will depend upon the difference that existsbetween the frequencies of the original currents. Thebeat frequency current flows maximally in the regionof maximum interference that develops along dia-gonals extending at 450 to the direct paths betweenthe two sets of electrodes (Figure 3). A snowflake-shaped field is created because one current flows

Circuit 1 unmodulated Resultant current100% amplitudemodulation

Figure 3. Pattern of interference current and degree ofinterference produced during a quadripolar application(by permission of Ehraf-Nonius, Delft, The Netherlands,see ref. 1)

laterally from its direct path to interact with theadjacent current. This region of maximal therapeuticeffect is usually static and situated deep within thetissues3.

Static fields are used to treat small, well definedlesions but may miss sites of more diffuse damage.This difficulty is overcome by scanning the region ofmaximum interference systematically through thetissues. A voltage (and hence a current) applied toone of the pairs of electrodes, varying rhythmically inintensity with respect to the other, will influence anarea that expands and recedes regularly. This causesthe region of maximum interference to pan throughthe tissue2. Most interferential units offer this as anautomated facility, although all such automaticfunctions have a manual over-ride.Some units allow for both currents to be applied in

one circuit using a single pair of electrodes. Inter-ference current will affect all the tissues between theelectrodes and allow poorly localized lesions to betreated adequately. This area of maximum inter-ference is, however, dispersed widely, thus reducingthe therapeutic effect. The behaviour of interferencecurrents in fluid media is considered in greater detailelsewhere6.Some manufacturers offer equipment that can also

operate at a base frequency of 2kHz. The interferencecurrents so generated are of similar frequency tothose produced by the interaction of currentsalternating at 4 kHz, although clinical practice sug-gests that the lower base frequency is able tostimulate muscles more effectively'.Recent advances in electronic design enable manu-

facturers to supply units that generate three-dimensional, or stereodynamic interference fields.Three currents of slightly differing medium frequen-cy are applied via three separate electrode pairs.These interact to affect a greater volume of tissue thanis possible with the more common twin-currentquadripolar application .

Techniques, contraindications and safetyThe area of skin to be treated is cleaned with soap andwater to reduce linear electrical resistance (reactancearising from capacitance is unchanged) and theelectrodes are fixed to the skin with tape. Someapparatus is supplied with electrodes that are held inplace by suction cups evacuated using a vacuumpump. This facility is useful when treating regionssuch as the trunk where it is difficult to strap anelectrode. The electrodes are orientated so that thetwo currents intersect within the target structure.Alternatively, the therapist may wear one electrodeof each pair as a glove and vary the site of maximuminterference during the treatment. Some units incor-porate four electrodes into a single small applicator,thus facilitating the effective treatment if superficialand localized lesions.The intensity of the current is increased gradually

until the patient reports that a further rise wouldcause discomfort. Cutaneous nerves accommodaterapidly to this stimulus and after a few seconds alarger current can be applied. This procedure is

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repeated until no further accommodation isobserved. Most patients tolerate interferential thera-py well. Further explanation of the practical aspectsof treatment are available in various authoritativetexts2'4'5' 8-10

Contraindications are few, although the prudentwould not treat patients presenting with very acuteinflammation, fever, tumour, thrombosis, those whoare pregnant, have a marked aversion to this type oftherapy, or persons wearing a cardiac pacemaker.Concern that interferential therapy might promotethe aggregation of platelets and induce thrombosisappears unfounded 1.

This apparatus should not be used within fivemetres of an operational short-wave diathermy unitbecause the cables may act as antennae and conduct adangerous quantity of RF energy to the patient2.

Physiological and therapeutic effects ofinterferential currentsThe current flowing between each pair of electrodesis insufficient to stimulate nerve and musde directlyuntil amplitude is modulated by interference. Inter-ferential therapy thus reduces the stimulation ofcutaneous sensory nerves near the electrodes whilstpromoting the effect upon deep tissues.The physiological effect of an amplitude-

modulated suprathreshold current depends uponfrequency. Neurons exhibit a maximum rate at whichaction potentials are conducted and this is a functionof the degree of myelination and the diameter of theaxon. Repetitive stimulation at any frequency up toits maximum (1 kHz for a large motor neuron) willcause action potentials to flow in the axon at the samerate. As the rate of stimulation increases above thisvalue, successive stimuli fall within the relative, andeventually the absolute refractory period of thepreceding action potential. A larger than normal flowof current is necessary to stimulate a refractoryneuronal membrane and thus the sensitivity of thenerve decreases. This effect is termed Wedenskyinhibition. Prolonged stimulation at a supramaxialfrequency will eventually cause the axon to ceaseconducting. Accommodation of the neuron is respon-sible for this effect, caused by an increased thresholdand synaptic fatigue'. Some sources report thatthese effects occur in large neurons stimulated atfrequencies as low as 40 Hz'3. Small or unmyelinatedneurons have - a slower conduction velocity andlonger refractory period than large neurons and willshow a stimulus-induced block to conduction at alower frequency.

Stimulation of muscleA neurone showing the reduced sensitivity asso-ciated with Wedensky inhibition will also have a rateof firing independent of the frequency of the appliedstimulus. This rate is dictated instead by the durationof the refractory period. Known as the Gildemeistereffect, rapid stimulation of a motor nerve with largealthough comfortable interferential currents willresult in an asynchronous depolarization of indi-


vidual motor units. This mimics the pattern observedduring a normal voluntary contraction. Traditionallow-frequency neuromuscular stimulation tends torecruit only the large axon motor neurons, whichhave a lower threshold than small fibres, andinnervate muscle fibres that fatigue readily. Thispattern of discharge is synchronous and unlike anormal contraction.Motor excitation using interferential currents is

considered by many to represent an advance over theother low-frequency methods of stimulation. Theoptimum frequency of stimulation for most voluntarymuscle appears to be 40-80Hz5 14, whilst visceralmuscle, supplied by the autonomic nervous system,is stimulated optimally at 10-50 Hz'5.

Interferential therapy can produce a torque in thequadriceps femoris greater than 50 per cent of thatachieved during a maximal voluntary contraction'6.This performance certainly equals that of the othermethods of electrical muscle stimulation14. A favour-able clinical outcome was also reported in thetreatment of muscular paralysis arising from degen-eration of the facial nerve' and radial epicondylitis'8.

Control of painThe analgesic effect of interferential therapy can beexplained in part by Wednesky inhibition of Type Cnociceptive fibres, although other mechanisms arecertainly involved. 'Pain gate' theory, proposed byMalzack and Wall'9 and much modified subsequent-ly20 remains central to this explanation. Briefly, thistheory proposes that action potentials travelling inlarge-diameter myelinated afferent nerves fromcutaneous receptors compete for access to the centralascending sensory tracts in the dorsal horn of thespinal cord with those of small-diameter unmyelin-ated sensory fibres carrying pain information. Activ-ity in the large fibres takes precedence over that insmall fibres, 'closing the gate' to pain informationentering the central nervous system and preventing itfrom reaching a conscious level. Pain is thus reduced.Large-diameter myelinated fibres are stimulatedoptimally at 100 Hz5 2' and clinical experience indi-cates that interferential therapy at this frequencyreduces pain markedly, especially when applied toacupuncture points. Pain will also reduce as motorstimulation increases the circulation of body fluid andpromotes an efflux of pain-inducing chemicals fromthe site of damage.Another system that helps to reduce pain is the

'descending pain suppression mechanism', which ismediated by the endogenous opiates. Nociceptive.information that enters the spinal cord travels to thethalamus and will interact in the mid-brain withmany structures. The raphe nuclei are amongst themost important of these, and increased activity infibres descending from the raphe nuclei to the spinalsegment at which the pain information entered willrelease inhibitory neurotransmitters that block fur-ther conductions. Interferential current with afrequency of 15Hz affects these fibres maximally5'2'.A beat frequency varying rhythmically within anarrow range about this optimum value avoids theproblem of accommodation to the stimulus"4' 5. Pain




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will initially intensify as this mechanism is activatedby transcutaneous stimulation of Type A6 and Cfibres, although the analgesia induced subsequentlyappears more enduring than that achieved byrecruiting the 'pain gate' system.

Interferential therapy is often applied clinically tocontrol pain2'5'21 but few rigorous studies arereported that justify this use. Taylor et al.23 noted thatjaw pain was not controlled adequately by interferen-tial therapy, although pain induced deliberately byimmersion of a limb in iced water was rated as lesssevere, compared to the experience of the controls,by subjects treated previously with interferentialcurrent at 100Hz (Goats et al. 1989 unpublishedfindings). Pain arising from sprained joints wasreduced markedly by a 15 minute application ofinterferential therapy at a frequency varying between0 and 100 Hz24 and classical migraine responded wellto treatment at 90-10 Hz for 10 minutes applied tothe zygomatic arch25.The placebo effect is a potent factor in the use of an

interferential therapy unit.

Autonomic effects and the control of incontinenceType A6 and C fibres, and those of the autonomicnervous system, are generally small and poorlymyelinated. Clinical evidence suggests that thesesmall neurons of the peripheral nervous system fail toconduct when stimulated at frequencies exceeding 40and 15Hz respectively2l. When extrapolated to theautonomic nervous system, this behaviour can beexploited therapeutically5'26 by using the stimulus ofan interferential current to reproduce by non-invasivemeans the vasodilatation caused by chemical sym-pathectomy in peripheral vascular disease and reflexsympathetic dystrophy27 28. There is some disagree-ment regarding the precise frequency at which thisinhibitory response occurs

Several authors report confidently that low-frequency currents can also be used to stimulate theautonomic system selectively"5'30 31*

Interferential therapy can benefit patients withboth stress and urge incontinence although thecauses of each differ. Stress incontinence results froman incompetent urethral sphincter mechanism, whilsturge incontinence arises from a disinhibition of thedetrusor muscle. Patients showing stress inconti-nence, urge incontinence, or both, and treated withinterferential therapy at 0-10 Hz for 15 minutes onthree days per week reported decreased frequency ofmicturition32. Extensive studies conducted byLaycock and Green'5 were designed to identifyprecisely the optimum frequency of stimulation, andposition of the electrodes, for the treatment ofincontinence. Drawing upon results obtained usinganimals33, they concluded that stress incontinenceshould be treated at 10-50 Hz for 15 minutes. Initiallysuch stimulation should cause the external urethralsphincter to close by a direct action upon the slowlyconducting pelvic sympathetic nerves. An additionaltreatment at the higher frequency excites maximallythe perineal branch of the pudendal nerve (which hasa conduction velocity that lies in the slow to mediumrange, depending upon the twitch speed of the

muscle fibre that it innervates) and hence recruits allelements of levator ani.Urge incontinence is treated at 5-10 Hz for 30

minutes, the lower rate of stimulation representingan attempt to excit small afferent fibres in the pudenalnerve that have a slow conduction velocity. This willproduce reflex inhibition of detrusor followingcontraction of the slow twitch pelvic floor muscles. Aclinical evaluation of these regimes is not yetavailable. Other workers have failed to identify a rolefor interferential therapy in the treatment of anorectalincontinence

Control of circulation and reducing oedemaSeveral studies investigate changes in the rate ofblood flow following transcutaneous electrical nervestimulation. Stimulation applied to the dorsal roots orspinal segment of origin of a peripheral nerve causesperipheral vasodilatation in the structures innervatedby it31. Sufferers from Raynaud's syndrome treatedfor eight minutes at 90-10OHz in the region of thestellate ganglion in the neck showed a doubling ofpulse volume in the digital vessels26. Nikolova-Troeva3 demonstrated a similarly marked symp-tomatic improvement in patients with endarteritisobliterans who failed to respond to chemical sym-pathectomy or medication. Supporting these findingsis a report that those with a peripheral vasculardisease benefit from interferential therapy at0-10OHz for 10 minutes36, although recent investi-gations cast doubt on the reproducibility of theseeffects30 37.

Interferential therapy at a frequency of 10OHz isrecommended for the reduction of acute oedema.Such stimulation will activate the musculoskeletalpump and inhibit sympathetic activity, thus assistingthe drainage of fluid from the affected area.Interferential currents also appear to have a directeffect upon the cell membrane and reduce the escapeof intracellular fluid5.Chronic oedema is treated optimally using a

two-stage application. Initially the current is appliedat 100Hz to promote vasodilation. This is followed bya treatment at 1OHz which activates the muscu-loskeletal pump to remove fluid that has returned tothe venous and lymph channels.Evidence supporting the use of interferential

therapy in the control of oedema appears mainlyanecdotal, although in most textbooks this stillappears as an indication4'5' 10.

Effects upon cell metabolism and the healingprocessIn addition to those effects described above, theelectrical stimulation of tissue appears to exert other,more subtle, influences. Treatment with interferentialcurrent alters the intracellular concentration ofenzymes and other molecules that are important inmany metabolic processes. The literature containsreports of changes in the titre of cyclic adenosinemonophosphate 8, acetylcholine esterase, alkalinephosphatase39, and lysosomal enzymes4o. Suchobservations may help to explain the effects of




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interferential therapy that are as yet understoodpoorly, such as the acceleration of bone healing1 andthe repair of nerves39, tendons and laments, , andimproved regeneration of the liver. Further con-sideration of this topic is beyond the scope of thepresent work and the interested reader is referredelsewhere''.The use of electric currents to promote the healing

of bone currently enjoys considerable interest. Anextensive literature attends this topic and again theinterested reader is referred to recent reviews forfurther information''. Interferential therapy is stilllittle used in this capacity, although good results areclaimed in the treatment of acute fractures of the tibiaand fibula at 20 Hz for 20 minutes on five days perweek49. The same author reports a beneficial effect,on the basis of empirical observations, in cases ofdelayed or non-healing. Interferential therapy at20 Hz for 20 minutes improved the union ofmandibular fractures49, and at 100 Hz for 20 minutesaccelerated the resolution of Sudeck's atrophy andpseudoarthrosis'. The rate of callus formation andsubsequent mineralization resulting from fracturesinduced experimentally in the radius and ulna wasmore rapid in animals treated with interferentialtherapy5.

Therapy in neurological impairmentSpasticity resulting from a cerebrovascular accidentwas suppressed by the stimulation of groups ofmuscles antagonistic to those in spasm. This wasachieved using an interferential current alternating at50 Hz, and although the spasticity returned after onehour, useful progress in rehabilitation was possibleduring this period52. Chronic electrical stimulationfor eight hours daily at 10 Hz helped to reverseneuropathic changes caused by diabetes in rats, andmay indicate a method by which vulnerable nervesmight be protected53.

ConclusionInterferential current therapy is used widely tostimulate tissues that lie deep within the body. Theeffects can be local or more general depending uponthe configuration of the current applied to the skin.Unlike other methods of low-frequency electricalstimulation, these currents encounter a low electricalresistance and can thus penetrate deeply withoutcausing undue discomfort.

Several physiological effects clearly occur duringinterferential current therapy, although reliable clin-ical studies seeking to evaluate the claimed therapeu-tic benefits are reported infrequently.

Research suggests that interferential therapy caneffectively stimulate voluntary muscle, promoteperipheral blood flow, and accelerate bone healing.Empirical observations support a case for using thistechnique to reduce pain and control incontinence.Interferential therapy would seem to represent avaluable adjunct to the medical and physiotherapymanagement of the pathologies seen frequently bythose specializing in sports medicine. As research

continues to clarify the precise characteristics of thecurrent required to treat these various types of lesionsuccessfully, interferential therapy will continue togrow in importance as a versatile and effectiveapproach to therapy.

References1 Hogenkamp, M., Mittelmeijer, E., Smits, I. and Van

Stralen, C. Interferential Therapy B.V. Enraf-Nonius1987, Delft, Holland

2 Kloth, L. Interference current. In: Clinical Electrother-apy Nelson, R.M., Currier, D.P. (Ed.) Ch 9, 183-207,Appleton and Lange, 1987. Norwalk, Connecticut,USA

3 Ward, A.R. Electricity Fields and Waves in TherapyScience Press, 1980. Marrickville, NSW, Australia

4 De Domenico, G. Basic Guidelines for InterferentialTherapy. Theramed Books, 1981. Ryde, NSW, Austra-lia

5 De Domenico, G. New Dimensions in InterferentialTherapy: A Theoretical and Clinical Guide. 1st Edn ReidMedical Books, 1987, Lindfield, NSW, Australia

6 Treffene, R.J. Interferential fields in a fluid mediumAust J Physiother 1983, 29 (6), 209-216

7 Szehi, E. and David, E. The stereodynamic interferen-tial current - a new electrotherapeutic techniqueElectromedica 1980, 48, 13-17

8 Ganne, J.M. Interferential therapy Aust I Physiother1976, 22 (3), 101-110

9 Savage, B. Interferential Therapy. Faber and Faber 1984,London

10 Wadsworth, H. and Chanmugam, A.P.P. Electrophy-sical Agents in Physiotherapy. 2nd Ed. Science Press,1983. Marrickville, NSW, Australia

11 Herbert, K., Bowcock, S.A., Oakley, S. and Cooke,E.D. Interferential therapy in patients on oral anti-coagulants Physiotherapy 1985, 71 (12), 521

12 Krnjevic, K. and Miledi, R. Failure of neuromuscularpropagation in rats I Physiol 1958, 140, 440-461

13 Brown, G.L. and Bums, B.D. 1985, Fatigue andneuromuscular block in mammalian skeletal muscleProc R Soc Lond 1949, 136 182-195

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15 Laycock, J. and Green, R.J. Interferential therapy inthe treatment of incontinence Physiotherapy 1988, 74(4), 161-168

16 Walmsley, R.P., Letts, G. and Vooys, J. A comparisonof torque generated by knee extension with a maximalvoluntary contraction vis-a-vis electrical stimulation JOrthop Sports Phys Ther 1984, 6 (1), 10-17

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18 Eigler, E. Success achieved by treatment with in-terferential current on patients with epicondylitishumeri. Proceedings of the 84th Congress of the GermanSociety of Physical Medicine and Rehabilitation 1979,Hannover, FRG

19 Melzack, R. and Wall, P.D. Pain mechanisms: a newtheory Science 1965, 150, 971-979

20 Wall, P.D. The discovery of transcutaneous electricalnerve stimulation Physiotherapy 1985, 71 (8), 348-358

21 De Domenico, G. Pain relief with interferentialtherapy Aust I Physiother 1982, 28 (3), 14-18

22 Watson, J. Pain mechanisms: a review. 3. Endogenouspain mechanisms Aust I Physiother 1982, 28 (2), 38-45




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23 Taylor, K., Newton, R.A., Personius, W.J. and Bush,F.M. Effects of interferential current stimulation fortreatment of subjects with recurrent jaw pain PhysTher 1987, 67 (3), 346-350

24 Nikolova-Troeva, L. Interference current therapy indistortions, contusions and luxations of the jointsMunch Med Wochensch 1967, 109 (11), 579-582

25 Truscott, B. Interferential therapy as a treatment forclassical migraine: case reports Aust J Physiother 1984,30 (1), 33-35

26 Schoeler, H. Physical block of the sympathetic chainTechnik im der Medizin 1975, 1. Deutsche Nemectron

27 Kaanda, B. Vasodilation induced by transcutaneousnerve stimulation in peripheral ischaemia (Raynaud'sphenomenon and diabetic polyneuropathy) Eur HeartJ 1982, 3, 303-314

28 Wang, J.K., Johnson, K.A. and Ilstrup, D.M. Sym-pathetic blocks for reflex sympathetic dystrophy Pain1985, 23, 13-17

29 Wong, R.A. and Jetter, D.U. Changes in sympathetictone associated with different forms of transcutaneouselectrical nerve stimulation in healthy subjects PhysTher 1984, 64 (4), 478-482

30 Bergslien, O., Thoresen, M. and Odemark, H. Theeffect of electrotherapy on human peripheral circula-tion Acta Physiol Scand 1985, 123, 35A

31 Dooley, D.M. and Kasprak, M. Modification of bloodflow to the extremities by electrical stimulation of thenervous system South Med J 1976, 69 (10), 1309-1311

32 Dougall, D.S. The effects of interferential therapy onincontinence and frequency of micturation Physiother-apy 1985, 71 (3), 135-136

33 Ohlsson, B., Lindstrom, S., Erlandson, B-E. and Fall,M. Effects of some different pulse parameters onbladder inhibition and urethral closure during intra-vaginal electrical stimulation: an experimental studyin the cat Med Biol Eng Comput 1986, 24, 27-33

34 Sylvester, K.L. and Keilty, S.E.J. A pilot study toinvestigate the use of interferential in the treatment ofano-rectal incontinence Physiotherapy 1987, 73 (4),207-208

35 Nikolova-Troeva, L. The modem electrotherapeuticmethods in the therapy of endarteritis obliterans TherGegenw 1968, 102, 190-198

36 Belcher, J.F. Interferential therapy NZ J Physiother1974, 6, 29-34

37 Bergslien, O., Thoresen, M. and Odemark, H. Theeffects of three electrotherapeutic methods on bloodvelocities in human peripheral arteries Scand J RehabilMed 1988, 20, 29-33

38 Norton, L.A., Rodan, G.A. and Bourret, L.A.Epiphyseal cartilage cAMP changes produced byelectrical and mechanical perturbations Clin Orthop1977, 124, 59-68

39 Nikolova, L. and Davidov, M. Influence of interferen-tial current on enzyme activity of traumatized nerve

(experimental study) Vopr Kurortol Fizioter Lech Fiz Kult1978, 6, 54-57

40 Nikolova, L.T., Popov, A.A., Kloucheck-Popova, E.F.and Apostolov, I.Tz. D-Galactosamine induced hepa-titis: morphological and enzyme biochemical changesby interferential currents and low-frequency magneticfield Physiotherapy 1984 70 (8), 301-305

41 Ganne, J.M. Stimulation of bone healing withinterferential therapy Aust I Physiother 1988, 34 (1),9-20

42 Stanish, W.D., Rubinovich, M., Kozey, J. andMacGillvary, C. The use of electricity in ligament andtendon repair Phys Sports Med 1985, 13 (8), 109-116

43 Geddes, L.A. A short history of the electricalstimulation of excitable tissue induding electrothera-peutic applications Physiologist 1984, 27 (1), S1-S47

44 Newton, R. High-voltage pulsed galvanic stimulation:theoretical bases and clinical applications In: ClinicalElectrotherapy. Nelson, R.M., Currier, D.P. (Ed.) Ch 8,165-182. Appleton Lange, 1987. Norwalk, Connec-ticut, USA

45 Wu, K.T., Dennis, C. and Sawyer, P.N. Effects ofelectrical currents and interfacial potentials on woundhealing I Surg Res 1967, 7, 122-128

46 Bassett, C.A.L. The development and application ofpulsed electromagnetic fields (PEMFs) for ununitedfractures and arthrodeses Clin Plast Surg 1985, 12 (2),259-272

47 Lilly-Masuda, D. and Towne, S. Bioelectricity andbone healing. I Orthop Sports Phys Ther 1985, 7 (2),54-58

48 Petersson, C.J., Holmer, N.G. and Johnell, 0.Electrical stimulation of osteogenesis Acta OrthopScand 1982, 53, 727-732

49 Ganne, J.M., Speculand, B., Mayne, L.H. and Goss,A.N. Inteferential therapy to promote union ofmandibular fractures Aust NZ J Surg 1979, 49 (1),81-83

50 Nikolova-Troeva, L. Physiotherapeutic rehabilitationin the presence of fracture complication Munch MedWochensch 1969, 111 (11), 592-599

51 Laabs, W.A., May, E., Richter, K-D., Hohling, H.J.,Althoff, J., Quint, P. and Hansjurgens, A.Knochenheilung und dynamischer interferenzstrom(DIC)- Erste vergleichende tierexperimentelle studiean schafen. Teil 1: Experimentelles vorgehen histolo-gische ergebnisse Langenbecks Arch Chir 1982, 356,219-229

52 Alfieri, V. Electrical treatment of spasticity Scand JRehab Med 1982, 14, 177-182

53 Cameron, N.E., Cotter, M.A. and Robertson, S.Chronic low frequency electrical activation for oneweek corrects nerve conduction velocity deficits in ratswith diabetes of three months duration Diabetologia1989, 32, 759-761




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