05/315901

07/08/1975

12/22/1972

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ESB Incorporated (Philadelphia, PA)

607/51

607/76, 600/13

A61N1/32; A61N1/40; A61N1/36

128/1.5,21R,82.1,172.1,404,405,411,410,413,418,419F,419R,421,422

3745995

APPARATUS AND METHOD FOR AIDING FORMATION OF BONE FORMING MATERIAL

July 1973

Kraus

Doyle et al., "Journal of Bone & Joint Surgery," Vol. 45A, No. 1, Jan. 1963, pp. 15-24..

Kamm, William E.

Rossi, Esq. Esq. Anthony Robinson Robert Smith Wm Wharton J. H.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. application Ser. No. 221,653, filed Jan. 28, 1972 and U.S. application Ser. No. 290,391, filed Sept. 19, 1972, both of which have been abandoned.

I claim

1. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising:

2. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising:

3. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising:

4. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising:

5. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 4 wherein said rise time corresponds with a high frequency content within the range of from about 10 hertz to about 10 kilohertz.

6. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 4 wherein said rise time corresponds with a high frequency content within the range of from about 10 kilohertz to about 50 kilohertz.

7. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 4 wherein said rise time corresponds with a high frequency content within the range of from about 50 kilohertz to about 200 kilohertz.

8. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 4 wherein said rise time corresponds with a high frequency content within the range of from about 200 kilohertz to about 1 megahertz.

9. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising:

10. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprpsing:

11. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by increasing the absolute value of the electrical potential of the predetermined zone of the living body comprising:

12. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the local potentials at the membranes of cells and fluid interfaces in the predetermined zone of the living body comprising:

13. An electrical medical device for artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the local potentials at the membranes of cells and fluid interfaces of the predetermined zone of the living body comprising:

14. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

15. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

16. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

17. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

18. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 17 wherein said rise time corresponds with a high frequency content within the range of from about 10 hertz to about 10 kilohertz.

19. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 17 wherein said rise time corresponds with a high frequency content within the range of from about 10 kilohertz to about 50 kilohertz.

20. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 17 wherein said rise time corresponds with a high frequency content within the range of from about 50 kilohertz to about 200 kilohertz.

21. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body as set forth in claim 17 wherein said rise time corresponds with a high frequency content within the range of from about 200 kilohertz to about 1 megahertz.

22. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

23. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the electrical potential of the predetermined zone of the living body comprising the steps of:

24. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by increasing the absolute value of the electrical potential of the predetermined zone of the living body comprising the steps of:

25. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the local potentials at the membranes of cells and fluid interfaces in the predetermined zone of the living body comprising:

26. The method of aritficially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the local potentials at the membranes of cells and fluid interfaces of the predetermined zone of the living body comprising:

27. The method of artificially stimulating normal bone growth and repair processes in a predetermined zone of a living body by modifying the naturally occurring electrical potential of the predetermined zone of the living body comprising the steps of:

28. A method for artificially stimulating bone growth in a predetermined zone of a patient, comprising the steps of:

29. A method as defined in claim 28 wherein the electrode being located closer to said predetermined zone is smaller than the other of said electrodes.

30. A method for artificially stimulating bone growth in a predetermined zone of a patient, comprising the steps of:

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrical medical devices and methods, and more particularly, it relates to electrical medical devices and methods which are useful in the therapeutic treatments of cells or tissue of a living body which require a bioelectrical signal, as this term is defined herein, at the cellular or tissue level to artificially stimulate healing of the cells or tissue.

As used herein, the term "therapeutic treatment" is meant to include the promotion of, or stimuli causing the healing or of desirable cells or tissue.

As used herein, the term biolelectrical signal is a signal which activates a mechanism that promotes healing of cells or tissue in a living body.

The term "reactively coupling" as used herein is generic to include either or both capacitive coupling and inductive coupling.

The term "faradaic" and "faradaic reactions" as used herein is used as an electrochemist would use it, i.e., faradaic reactions are those that can take place at the junction of an electrolyte and an electrode; a Faraday is defined as the quantity of electricity which reacts with one chemical equivalent of any substance.

The invention will here be described in most detail in association with the promotion of bone growth or bone repair or healing since the devices and methods according to the invention have been particularly developed for such use. However, the devices and methods of the invention may be therapeutically used in all those biological processes responsive to or which are affected by bioelelctrical signals.

2. Description of the Prior Art

It is well known in the biological community that electrical activity is associated with the majority, if not all, of cellular processes. Of particular interest here is that injury, for example bone break or fracture, limb amputation, etc., is always accompanied by a so called "injury current" which is in fact observed as potential or voltage. The important fact here is that electrical activity observed after injury is always different from that observed before injury, that is, after injury there is abnormal electrical behavior. While the exact relationship of this phenomenon to the actual cellular processes in, for example, repair or growth of tissue, is not clear, it has been observed that artificial control or modification of the overall electrical activity at the injury site can, at times, aid in healing.

In the case of bone healing, it is known that electrical phenomena are associated with both this process and normal bone remodeling. These electrical phenomena appear to be generated by the potential producing or the piezoelectric-like properties of bone and surrounding tissues which are natural phenomena and most likely the reason why in most cases bone does heal naturally. In order to study this electrical effect and to attempt to further stimulate bone healing, electrodes have been directly implanted into areas of bone injury. In the majority of cases, the controlled electrical variable was continuous direct current. In the few cases where electrical input other than DC was employed, the net effect was the appearance, at the tissue level, of a voltage that was bipolar with the amplitude and frequency components of one polarity equal to those of the opposite polarity, i.e., the driving voltage was sinusoidal (AC). Even with pulsating DC, the voltage at the tissue level was bipolar with the amplitude and frequency components of both polarities thereof being equal.

In the case of bone healing as well as for most biological processes involving cellular activity, it is evident that electrical events play an important role. However, most approaches to healing reported up to the present time have placed the primary emphasis upon the use of continuous DC signals as the stimulation source. This has a number of major limitations, as for example:

A. All of the information (or coding) able to be contained in the electrical energy or signals as they are finally coupled at the cellular level is not available due to restriction to DC only and to current only;

B. The efficiency of energy transfer is unnecessarily and severely limited;

C. The stimulation at the cellular level may be non-selective as a result of A and B, above; D. The use of implanted electrodes is required in the overwhelming majority of cases with concommitant electrode/electrolyte interface restrictions. For example, no electrode material is completely inert with respect to DC at any potential when in contact with body fluids;

E. The use of implanted electrodes may be toxic due to possible deleterious faradaic reactions and the electrodes themselves become "poisoned" for long-term implants;

F. The use of implanted electrodes in which the stimulating sources is also implanted rquires initial and post treatment surgery; and,

G. Where the stimulating source is external to the living body and conductively connected to implanted electrodes; there is a transcutaneous path from the exterior to body cavities and organs with risk of superficial and deep infection.

From the foregoing, it will be understood that bone growth has been promoted by modifying the electrical potential existing in the regions of a fracture or break. It has been observed that the naturally occurring electrical potential or potential difference extending from a proximal region and extending toward the distal region of a limb rises more or less linearly. However, when there is a fracture or break; the normally occurring potentials drastically change. it is postulated that the changed potential distribution is a part of nature's mechanism for signaling the need of structural repair with concommitant bone growth. Though not so well documented by experimental or clinical data, enough has been done further to postulate that the redistribution of potentials also signals the need of repair resulting from injuries of other kinds, for example, bruised muscular tissue, broken muscular tissue, as well as abrasions, lesions and cuts.

SUMMARY OF THE INVENTION

In accordance with the present invention, advantage has been taken of the prior experimental and clinical work, as well as additional experimental and clinical work utilizing the present invention, to achieve the artificial production of a desired electrical potential or potentials within and across a predetermined zone of tissue of a living body in which it is desired to signal the need of repair work. This is accomplished by reactivity coupling electrical signals to the predetermined zone of the living body to increase the absolute value of the electrical potential of the predetermined zone and to produce current flow therein of magnitude in one direction greater than in the opposite direction. Since a living body though conductive in respect of current flow also exhibits properties of both capacitance and inductance, the reactive coupling not only becomes feasilbe but has been demonstrated to function well in the practice of this invention. Accordingly, by generating an undulating electrical signal having a wave-form whose rise time is different from its fall time, there is produced in the predetermined zone the aforesaid current flow which is of greater magnitude in one direction than in the opposite direction. The resultant potential drop due to the current flow gives rise to a different potential distribution within and across the predetermined zone of tissue and the action may be cumulative with naturally occurring change of potential to enhance and speed the repair mechanisms with faster rates of recovery from injuries of all sorts.

The present invention utilizes the concept that, at the cellular or tissue level in a living body, a bioelectrical signal will artificially stimulate healing in cells or tissue of a living body. Though this mechanism is at the present time unknown to applicant, it is believed that cell-membranes manner as electrode/electrolyte interfaces. As such, those biological events which occur at excitable and non-excitable cell-membranes can be expected to be potential or voltage dependent just as events occurring at electrode/electrolyte interfaces are potential or voltage dependent. Accordingly, it is believed that significantly large quantities of charge can be stored at cell-membranes because of double layer, adsorption, absorption and desorption processes. Also, redox processes can occur at these interfaces. Stated another way, it is believed that cellular events may be influenced by what happens at the membranes of a cell and that a membrane behaves as an electrode and thus it will respond to local potential variations which may cause, for example, absorption or desorption of a critical communicating chemical species (molecular or ionic substances) to effect the speciffic healing process involved.

It is thus proposed that the use of the principles of the present invention will enable the combined use of potential control coupled with appropriate frequency content of the electrical signals at the tissue level for the selective and efficient artificial therapeutic treatment without the disadvantages enumerated above in paragraphs (A) through (G) of the Description of the Prior Art.

Briefly, the devices in accordance with the invention comprise electrical medical devices for modifying the electrical potential of a zone of living tissue of a living body. Means are provided for generating an undulating electrical signal having a wave-form whose rise time is different from its fall time. These signals are reactively coupled to the predetermined zone to produce a current flow in the zone of magnitude in one direction greater than in the opposite direction.

Briefly, the methods in accordance with the invention comprise methods for modifying the electrical potential of a zone of living tissue by applying to the zone of living tissue an electrical signal having a wave-form whose rise time is different from its fall time and reactively coupling the signals to the predetermined zone to produce a current flow in the zone of magnitude in one direction greater than in the opposite direction.

Other features and advantages of the present invention and a more complete understanding of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings which form a part of this specification. The drawings disclose by way of example, and not by way of limitation, the principles of the invention and structural implementations of the inventive concept.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 are schematic diagrams of the embodiments of the electrical medical devices according to the invention;

FIGS. 3 and 4 are illustrations of diagrammatic electrical signals useful to explain the operation of the schematic diagrams of FIGS. 1 and 2, and to explain the invention;

FIGS. 5 and 6 show electrical medical devices of the invention with a patient on which they are being used, parts of the latter being schematized; and

FIG. 7 schematically illustrates a mechanical device in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings wherein like reference characters refer to like parts throughout the several views, there is shown in FIG. 1 an embodiment of a bioelectrochemical device of the invention. Essentially, the circuit of FIG. 1 is a two-stage rate-adjustable complementary astable blocking oscillator which generates an undulating output voltage or an electrical signal having sawtooth waveform (see FIG. 3) across its output terminals 20 and 22. Each sawtooth waveform may, for example, be of variable duration, as for example, a waveform with a typical duty cycle of 0.01 sec. with a typical rise time of 0.0001 sec. and a typically fall time of 0.0099 sec..

A pair of electrodes 50, 52 are operatively connected to the output terminals 20, 22 via transmission means for leads 54 and 55. The electrical energy represented by the sawtooth wave-form is capacitively applied by way of electrodes 50 and 52 to an "external load" 24 which is to be taken as representative of a predetermined zone of tissue of a living body where there has occurred an in vivo injury or abnormality. In the case of bone healing, the load may be considered to be a limb of a patient having a gap, fracture or break of the bone in the region between the electrodes. In this connection, it will be preferred that one of the electrodes be remotely located relative to the other and will be of greater size in reduction of current density. This will be further explained with reference to FIG. 5 hereinafter.

In the method and system embodying the present invention, advantage is taken of the fact that through a reactive coupling means current flow may be induced in living body. The latter represents conductive media of differing resistivity depending upon the particular tissues and body fluids under consideration. since there will be established between the electrodes and the body a capacitor, as will be explained more fully hereinafter, the embodiment of FIG. 1 is primiarly one of capacitive coupling. Referring now to the wave-form of FIG. 3, it will be seen that there is first applied between the electrodes 50 and 52 a voltage which rises in a very short period of time, delineated in FIG. 3 by the points RST, followed by a decreasing voltage over a substantially longer period of time, delineated by the points TU. The cycle repeats with a rapid rise in voltage in the positive direction followed by a slowly decreasing voltage in the negative going direction. Voltage can be either positive going or negative going, depending upon the convention established by the observer, also, rise time and fall time can occur in the positive going direction or the negative going direction and for purposes of this application the rise time is that portion of the driving signal of FIG. 3 expressly intended to achieve the desired therapeutic signal at the cellular level, i.e., that portion delineated by the points RST in FIG. 3. The important fact here is that the application of electrical energy with the wave-form of FIG. 3 to body tissue results in current flow within the tissue of the general character of FIG. 4. Thus with the rapidly rising voltage, there will be a corresponding relatively high value of current induced in the tissue. Thus on each rise of voltage from a negative value to a positive value, FIG. 3, there will be a corresponding high peak of current as shown in FIG. 4, delineated by points ABC. Upon decrease of the voltage from the positive value to the negative value a very low order of current is caused to flow in the tissue, delineated by points CD. In connection with the foregoing, the rising current can either be in the positive direction as shown in FIG. 4 or it may be rising in the negative direction for a sawtooth-like output where the rapid rise in voltage is in the negative direction and the slow fall in voltage is in the positive direction, the reverse of the situation illustrated in FIG. 3. By reason of the foregoing phenomena, the current flow produced in the load representing a zone of the living body has a magnitude in one direction greater than in the opposite direction. This flow of current, of course, produces potential differences across the body tissue and these potential differences are believed to modify and alter the potentials at the interfaces of the cell-membranes as well as the absolute value of the gross potential distribution along the predetermined zone of tissue undergoing treatment. The hard tissue, corresponding with bony structure, generally, is at a much deeper level than is the muscle tissue or a substantial amount of the soft tissue including the fluids generally found near the surface.

It is an important feature of this invention to cause current to flow in the tissue in which the potentials at the cellular level are to be modified. Thus, where the tissue such as the bony structure is deep below the surface, the rise time of the voltage applied to the electrodes 50 and 52 should be long enough so as to allow penetration to the depth of the bony structure. This will result in a frequency content ofo that part of the applied signal, that is, as delineated by points RST in FIG. 3, consistant with the restrictions placed on the depth of penetration by the electromagnetic skin effect. The rise time, and thus the frequency content, of the signal of FIG. 3 delineated by the points RST is selected so as to be effective in reaching the deepest portions of the body under treatment to achieve the potential changes needed at the cellular level in accordance with the teachings of the present invention.

Typically, for deep tissue, a maximal frequency content of that portion of driving signal, that is, that portion delineated by points RST of FIG. 3, should be in the range of about 10 hertz to about 10 kilohertz which corresponds to a rise time of about 0.1 sec. to about 0.0001 sec.; for intermediate depth tissue, in the range of about 10 kilohertz to about 50 kilohertz which corresponds to the rise time of about 100 microseconds to about 20 microseconds; for subcutaneous tissue, in the range of about 50 kilohertz to about 200 kilohertz which corresponds to a rise time of about 20 microseconds to about 5 microseconds; and for cutaneous tissue, in the range of about 200 kilohertz to about 1 megahertz which corresponds to a rise time of 5 microseconds to about 1 microsecond. In general, the driving signal should have a wave-form in which the fall time with respect to the rise time differs by at least one order, that is, differs by a factor of 10.

It may be pointed out here that the just given electromagnetic skin effect limitations with respect to rise time of the wave-form of FIG. 3 must be consistent with limitations imposed by the kinetic reaction speeds of those electrohemical events at the cellular level necessary to achieve the desired thereapeutic effect.

Also, while a relatively long fall time with respect to rise time is shown for the wave-form of FIG. 3, it is to be understood that a fall time having a shorter time period than the rise time of the waveform can be utilized in practicing the invention. This is because, firstly, the depth of penetration of most of the induced current in the tissue generated during the fall time can be regulated by adjusting the time period of the fall time in accordance with the restrictions placed on the depth of penetration of the induced current by the electromagnetic skin effect. This will prevent most of the induced currents from reaching the tissue under treatment. Secondly, that small portion of the induced current which does penetrate the tissue under treatment during the fall time can be made to exist for a period of time shorter than that necessary to inhibit those electrochemical events at the cellumar level, which occur during the rise time of the wave-form and achieve the desired therapeutic effect, by adjusting the fall time of the wave-form.

Typically, such fall times would be shorter than the rise time by at least one order, that is, ten times smaller, and would typically be also less than ten microseconds which corresponds to a frequency greater than 100 kilohertz.

From the foregoing, it will now be understood that the particular system utilized may take various forms; that the rise time of the driving signal is to be different from the fall time thereof; and that the system of FIG. 1 is to be taken as exemplary. More particularly, in FIG. 1, the sawtooth wave-form rate is proportional to the power supply voltage 23, the external load 24 placed on the circuit and the values of resistor 32 and variable resistor R ₃₀ . The transistor 25 is of the NPN type and the transistor 26 is the PNP type. Both transistors have the usual emitter, collector, and base electrodes. When the power supply 23 charges capacitor 28 such that point 27 is positive and point 29 is negative via resistors 30 and 32 sufficiently to forward bias the emitter base junction of the transistor 25, this transistor conducts. The resistor 31 is connected between the emitter of transistor 25 and point 35. Since the collector of transistor 25 is connected to the base of transistor 26, it in turn causes transistor 26 to conduct. As transistor 26 conducts, current flows through the primary winding 33 of the transformer 34. The secondary winding 36 of transformer 34 is so connected that the induced voltage further increases the base current supplied to transistor 25. This regenerative action causes a rapid increase in the current flow through the both transistors 25 and 26 until saturation is reached in both transistors. Transistors 25 and 26 remain saturated for the duration of the sawboth rise during which capacitor 28 is charged such that point 29 is positive and point 27 is negative.

The rise-time of the sawtooth wave-form thus produced is controlled primarily by the inductance of the transformer 34, the base to emitter forward resistance of transistor 25 and the capacitance of capacitor 28 with some secondary dependence upon the capacitance of capacitor 43 in series with the external load.

Continuing with the operation of the undulating output voltage producing circuit of FIG. 1, when the induced voltage in the secondary winding 36 begins to diminish, the current flowing into the base of the transistor 25 also diminishes which in turn reduces the base current of transistor 26. As transistor 26 turns off, the current in primary winding 33 decreases which further reduces the induced secondary voltage of winding 36. This latter regenerative action rapidly switches transistors 25 and 26 from saturation to cut-off thus terminating the rising portion of the sawtooth wave-form. The voltage which was developed across capacitor 28 during the pulse now reverse-biases the emitter-base junction of transistor 25 to the voltage level at which that capacitor 28 was previously charged. Capacitor 28 now discharges slowly through resistors 30, 32 and 31 and the power supply thus producing the falling portion of the sawtooth wave-form. When capacitor 28 is fully discharged, the cycle repeats with the charging of capacitor 28 through resistors 30 and 32. The bioelectrochemical stimulator circuit of FIG. 1 is a characterized by the fact that the signal generating rate is determined by the rate at which capacitor 28 reaches the base potential at which transistor 25 will conduct current. Accordingly, the values of the variable resistor 30, the fixed resistors 31 and 32, the power supply, and the value of the capacitor 28 may be considered as the primary RC timing means or circuit which determines the duty cycle, i.e., the sawtooth repetition rate. As described above, as the voltage of the power supply decreases the pulse rate will also decrease. Also, any external load which would be placed through capacitor 43 across capacitor 28 will increase the time necessary for capacitor 28 to reach the potential necessary to turn on transistor 25 by effectively increasing the total rate determing capacitance in the circuit. Therefore, an increase in external loading will be reflected as a decrease in the repetition rate of the sawtooth waveform produced by this circuit. Accordingly, the repetition frequency for the signal produced by the circuit of FIG. 1, is the reciprocal of the sum of the rise time and the fall time of the undulating waveform produced.

To complete the description of circuit of FIG. 1, diode 44 is required to suppress the large negative voltage spike which develops across the windings of transformer 34 at the termination of each pulse as a result of the energy stored in the inductance of transformer 34. If not suppressed this voltage spike would ultimately damage transistors 25 and 26. The capacitor 40 serves to reduce interference by suppressing extraneous high frequency magnetic signals which can be picked up directly by the transformer's magnetically permeable core and which could cause premature triggering of the circuit of FIG. 1. Finally, the resistor 46 serves to bleed off the I _cbo leakage currents of transistors 25 and 26. If these currents were not bled off during the interpulse period, these currents would be reflected in the collector of transistor 26 and magnified by the Beta of the transistor. For the specific transistors chosen, this could increase the total average current drain of the circuit of FIG. 1 by several percent at an operating temperature of 35° C to 40° C.

Now that the general principles of my invention have been explained in connection with the capacitive reactive coupling shown in the embodiment of FIG. 1, it is to be understood that inductive coupling may also be utilized. This follows by reason of the fact that living tissue is a conductive medium, as explained above. Accordingly, if a rate of change of magnetic flux is applied to a selected zone of the body to be treated, there will result a voltage loop and subsequent induced current flow in the selected zone. If that rate of change in one direction be substantially different from the rate of change in the opposite direction, then there will be achieved voltage and a current flow in the selected zone which generally corresponds with that illustrated in FIG. 4. Though those skilled in the art will understand how magnetic flux can be changed to meet the requirements of this invention, I have shown in FIG. 2 a system utilizing inductive coupling means to achieve that result.

Referring now to FIG. 2, and comparing FIGS. 1 and 2, it will be seen that they differ in that in FIG. 2 the electrode 50 has been replaced by the inducing means or coils 50a and 52a; the electrode plate 52 has been omitted, and output terminal 22 is connected to ground level via lead 56; and, an operational amplifier 47 has been included in the circuit. The operational amplifier 47 is supplied with electrical power via a dual 34V regulated D.C. power supply as typically employed for operational amplifier application, as indicated in the drawings, and is required because of the increased power requirements of the coils 50a and 52a as compared with the power requirements of the electrode plates 50 and 52 to couple into living tissue similar potential gradients. The coils 50a and 52a are electrically connected in parallel and, while two coils are shown, one coil may be utilized, if so desired, for practicing the teachings of the invention. The coils 50a and 52a are placed adjacent to and preferably not in contact with the load 25. The load 25, represents a limb of a patent under treatment just as the load 24 of FIG. 1 represented the limb of a patient.

The electrical operation of the circuit of FIG. 2 per se is the same as that of FIG. 1. Even the amplitude of the undulating output voltage, as measured between terminals 20 and 22, is the same in FIG. 2 as in FIG. 1 because of the inclusion of the operational amplifier 47 in the circuit of FIG. 2 in the follower mode.

At this point it may be explained that:

1. There exists a coupling capacitance between an electrode and an ionically conducting medium which is known as the electrical double layer capacitance. This capacitance can be utilized to transfer energy across this interface and, provided the potential across this interface does not equal or exceed that at which a faradaic reaction will take place; or the time during which a reaction potential is achieved is too short to allow the reaction to occur, this energy transfer will take place without a faradaic interaction between the electrode and adjacent ionically conducting medium;

2. There exist in any ionically or electronically conductive medium within a time-varying electro-magnetic field via induction a circulating electrical current. This current is induced by the voltage loop which always encircles magnetic flux which is changing in density with respect to time. It therefore follows that, if this medium is normally conductive, this induction can be utilized to transfer energy into this medium.

3. The efficiency with which electrical energy can be transferred into such a medium is directly proportional to the components of maximum amplitude of the electrical signals appearing in the medium and the conductivity of the medium.

4. The depth of penetration of the electrical energy will be inversely proportional to the frequency components of maximal amplitude of the electrical signals appearing in the medium.

Based upon (1) and (3), and the fact that cells, tissue and body fluids comprise ionically and electronically conductive mediums, I have discovered that one can externally or artifically stiumlate normal activity or healing in cells or tissue of a living body, for example, bone tissue. This can be accomplished (as will be more fully explained hereinafter) by generating an undulating voltage across electrodes placed adjacent to, but not necessarily embedded in the living body. The undulating voltage, when coupled to the tissue, will effect a flow of current through the tissue which current in turn will produce a voltage in the tissue that is bipolar with the amplitude and frequency components of one polarity thereof being different from those of the opposite polarity thereof. This bipolar voltage, it is postulated by applicant effects the bioelectrical signal, referred to above, which artifically stimulates healing in the tissue.

Furthermore, this can be accomplished without placing the electrodes within the living body or initiating a faradaic reaction at the interface between the electrodes and the body. Also, therapeutic action can take place in cells or tissue by the application of the electrodes directly to the surfaces of the living body, i.e., an electronic conductor-electrochemical conductor interface, or with a dielectric material interposed between the electrodes and the body surfaces, i.e., dielectric charge-electrochemical conductor interface, and based on (4), the transfer of electrical energy from the source of the undulating voltage to the side of treatment will be effected through or across the body surfaces. This is particularly desirable in the promotion of bone break or fracture healing.

Based upon (2) and (3), and the cells, tissue and body fluids comprise ionically and electronically conductive mediums, I have discovered that one also externally or artificially stimulate normal activity or healing in cells or tissue of a living body and that this can be accomplished by generating an undulating voltage across an inductive means placed adjacent to the living body. The inductive means will produce an undulating time varying electromagnetic field which field when coupled to tissue of a living body will effect a voltage loop which will in turn induce a flow of current through the tissue. The induced current in turn will produce a voltage in the tissue that is bipolar with the amplitude and frequency components of one polarity thereof being different from those of the opposite polarity thereof. This bipolar voltage, again, it is postulated by applicant, effects the bioelectrical signal, referred to above, which artificially stimulates healing in the tissue. Furthermore, this can be accomplished, as in the case when electrodes are used to couple the electrical energy to the body, without placing the inductive means in contact with the living body involved. That is, therapeutic action can take place in cells or tissue in a living body by the application of inductive means adjacent to, but not in contact with the surfaces of the body involved, and based on (4), the transfer of electromagnetic energy to the site of treatment will be effected through or across the intervening tissue. Again, this is particularly desirable in the promotion of bone break or fracture healing.

Referring now to FIGS. 3 and 4, the undulating output voltage produced by the circuits of FIGS. 1 and 2, as stated above, appears across the output terminals 20 and 22 and is illustrated as the sawtooth waveform shown in FIG. 3. As stated above, the amplitude of the output voltage produced by the circuit of FIG. 2 is the same as that produced by the circuit of FIG. 1, moreover, the shape of the waveform is substantially the same, and for purposes of explanation, FIG. 3 will be also utilized with reference to FIG. 2.

The wave-form of the signal (s) appearing in the external load of FIG. 1, namely, external load 24 is illustrated in FIG. 4. For purposes of explanation FIG. 4 will also be utilized with reference to FIG. 2. Consequently, the wave-form of the signal (s) appearing in the external load 25 is also illustrated in FIG. 4. The wave-form illustrated in FIG. 4, therefore, is representative of the current and voltage drop wave-forms at the loads 24 and 25, that is, at the tissue level.

One complete wave-form of the output voltage at the terminals 20 and 22 is designated in FIG. 3 by the points RSTU. A classical Fourier analysis of this waveform will show the frequency components of maximal amplitude (the fundamental frequency and first few harmonics) are much higher in that portion of the wave-form delieated by the points RST than in that portion delineated by the points TU.

In the circuit of FIG. 1, the electrode plates 50 and 52 and in the circuit of FIG. 2, the coils 50a and 52a are operatively connected to the output terminals 20 and 22 to effect a current flow in the respective loads 24 and 25. The manner in which this current flow is effected in each instance will be explained more fully hereinafter. It is clear from FIG. 4 that current flow at the tissue level in one direction rapidly increases from the magnitude shown at point A to a relatively higher magnitude at point B. The current then decreases to the magnitude at point C and continues at this magnitude until the point D and then the cycle repeats. The fact that the magnitude of the current in one direction greatly exceeds the magnitude of current flow in the opposite direction means that, in the zone of living tissue, either a predominantly negative potential or a predominantly positive potential, as may be desired, will be produced in the tissue to vary the naturally occurring electrical potential therein and thus, artificially stimulate growth of tissue. The predominate potential, either positive or negative, of the zone of treatement will be determined by the polarity of the driving signal with respect to the electrodes 50 and 52 and with respect to the coils 50a and 52a. As for example, reversal of the terminals 20 and 22 with respect to the electrodes 50 and 52 will result in an inversion of the signals shown in FIGS. 3 and 4. The fact that there is current flow of low magnitude in a direction not desired for modification of naturally occurring potentials, does not adversely affect the beneficial results of the therapeutic treatment achieved by the current flow in a selected direction of a magnitude many times greater than that in the opposite direction. Thus, the voltage at the tissue level, as shown in FIG. 4, may be considered of bipolar character, and the current flow in one direction of magnitude greatly in excess of the other achieves, in the coupling of the electrical signals produced by the circuits of FIGS. 1 and 2 to a living body, a potential difference which is predominantly of preferential polarity in avoidance of surgically required conductive implantation of electrodes in the tissue which is to be treated. The magnitude of this current is directly proportional to the relative values of the frequency components of maximal amplitude of the waveform as shown in FIG. 3.

Hence, the relatively higher values of the frequency components of maximal amplitude in that portion of the waveform of FIG. 3 delineated by the points RST will be reflected by a high absolute magnitude of the value of the effected current in the load (24 or 25) as shown in FIG. 4 delineated by the points ABC. The positive direction of this effected current (waveform of FIG. 4 delineated by te points ABC) reflects the upward direction of the rate of change of the driving waveform of FIG. 3. Similarly, relatively low values of the frequency components of maximal amplitude appearing in that portion of the waveform of FIG. 3 delineated by the points TU will be reflected by a low absolute magnitude of the value of the effected current in the load 24 or 25 as shown in FIG. 4 delineated by the points CD. The negative direction of this effected current (waveform of FIG. 4 delineated by the points CD) reflects the result of the downward direction of the rate of change of the driving waveform of FIG. 3.

From the foregoing, it will be understood that the magnitude of the current effected in the loads 24 or 25 is effected in such a manner so as to reflect the relative values of the frequency components of maximum amplitude of FIG. 3. That is, a classical Fourier analysis of the waveform of FIG. 4 will show that the frequency components of maximal amplitude are much higher in frequency in that portion of the waveform delineated by the points ABC than in that portion delineated by the points CD. In addition, it can be seen from FIG. 4 that at the tissue level a voltage is produced that is bipolar with the amplitude and frequency components of one polarity thereof being different from those of the opposite polarity thereof, and that the maximum amplitude of the signal (s) of FIG. 4 occurs at point B.

Referring now again to FIG. 1, the placement of the electrodes relative to the desired zone of treatment, or relative to the injury is such that the electrode having the highest current density, i.e., the smaller one, is closest to the site where the therapeutic treatment is desired. In accordance with the invention and in the promotion of bone growth, this electrode is the one in which the maximal frequency components are in the negative direction, that is, electrode 52, is chosen to be the smaller of the electrodes. Hereinafter electrode 52, will at times be referred to as the working electrode. The other electrode, electrode 50, hereinafter at times referred to as the counter-electrode, is configured for minimum current density, and it is placed for optimum potential distribution in order to keep parasitic effects, for example, neural damage, to a minimum. The electrodes 50 and 52 may be constructed of any conducting or semi-conducting material. The requirements for electrode material are:

1. that it not react with the skin causing, for example, inflamation or eruption.

2. that it not polarize excessively in the presence of body fluids in order that the desired energy and frequency content of the signals at the cellular or tissue level be the appropriate location for healing to occur.

The preferred embodiment for the electrodes 50 and 52 is silver although other suitable materials may be utilized.

It may be pointed out here that electrodes 50 and 52 may be placed in direct physical contact with the epithelial surfaces of the body under treatment in which case such a physical contact would result in an electrical-electrochemical interface, or a suitable dielecric material, as for example Mylar or even air, may be interposed between the electrodes and the epithelial surfaces of the body in which case such a physical contact would result in a dielectrical-electrochemical interface.

In the case of an electrical-electrochemical interface, the maximum potential or the time during which it is applied to any given electrode, in accordance with the teachings of the invention, are chosen to avoid faradaic reactions. Typically, as measured between the electrodes 50 and 52 is in the range of about 0.8 volts to about 1.0 volts in the positive direction and in the range of about 0.0 volts to about- 0.01 volts in the negative direction. These faradaic reactions may comprise local pH changes, local tonicity (osmolality) changes, destruction of necessary protein, lipids, etc. or electrolysis of the physiological saline by evolution of its components gases (H ₂ , Cl ₂ and O ₂ ).

If an ordinarily undesirably high potential, i.e. above about 1 volt, must be applied to the working electrode to effect the effect healing in a zone of tissue, necrosis of the tissue or other deleterious tissue effects can be avoided by holding the working electrode at this ordinarily high potential for a time period less than that necessary for faradaic reactions to occur. The exact time period's upper limit will depend on the potential drop across the working electrode-tissue interface. This latter potential is, not directly measurable. However, one can have access to a measurable potential between a working electrode and a reference electrode. This measurable potential, in turn, has two components namely, that potential across the working electrode-tissue interface which is responsibe for the occurrence of faradaic reactions, and that potential due to a voltage drop across the intervening tissue between the working and reference electrodes. Therefore, in terms of the measurable potential, the allowanble time period's upper limit is dependent upon the following factors: the working electrode area and geometry, and the tissue's geometry and conductivity between the working and reference electrodes which all determine the potential drop across this tissue volume. The voltage drop due to the impendance of tissue and body fluids when vectorially subtracted from the measured potential between working and reference electrodes will give the working electrode-tissue interface potential. This latter potential will in turn specify the preferential electrochemical reactions at this interface and, thus their kinetic reaction speeds. Their speeds, in turn, determine the maximum time period, i.e., the time periods upper limit, that the working electrode may be allowed to have a potential greater than that which will initiate faradaic reactions at the working electrode-tissue interface over long time periods. Typically, for a working electrode potential from about +1 volt to about +100 volts, respectively, referenced to a reversible Hydrogen electrode, (RHE), in the same electrolyte, i.e., tissue, the working electrode nanosecond respectively, on a one square centimeter surface area working electrode before deleterious faradaic reactions occur at the working electrode-tissue interface.

Similarly, for a working potential from about -0.01 volt to about - 100 volts, respectively, referenced to the RHE in the same electrolyte, i.e., tissue, the working electrode can remain at these potentials for only about 500 microseconds to about 1 nanosecond, respectively, on a one square centimeter surface area working electrode before deleterious faradaic reactions occur at the working electrode-tissue interface.

In summary of the above, in the case of an electrical-electrochemical interface, and in accordance with the invention, if an undesirably high potential is applied to the electrode-tissue interface for a time period not exceeding about 500 microseconds to about 1 nansecond per square centimeter of electrode surface, faradaic reactions will be avoided since they have time constants much longer than those associated with the charging and discharging of the double layer capacitance. When this time or frequency limitation cannot be met, then, in accordance with the invention, it is necessary that the amplitude of the potential measured between the working electrode and a RHE in the same electrolyte (tissue) not exceed about +0.8 to about +1.0 volts in the positive direction, or about 0.0 volts to about -0.01 volts measured between the working electrode and a RHE in the same electrolyte (tissue) in the negative direction to avoid the above mentioned faradaic reactions. These potential limits are valid for those electrodes, eg., platinum group metals, whose ions do not pass into solution to any appreciable extent when the potential is changed from the electrode's normal resting or equilibium potential. More restrictive, i.e., a smaller range of potentials, would be utilizable for most other type electrodes.

In the case of a dielectrical-electrochemical interface the problem of faradaic reactions is not present at the eoithelial surfaces of the body.

Referring now again to FIGS. 1, 3 and 4 the undulating output voltage produced by the circuit of FIG. 1, as stated above, appears across the output terminals 20 and 22 and, as stated above, illustrated as the sawtooth waveform shown in FIG. 3. The undulating output voltage is AC or capacitively coupled to the electrodes 50 and 52 via capacitor 43. This type coupling assures that no DC components appear at the terminals 20 and 22. Capacitor 43 may be omitted in those instances where the electrodes 50 and 52 have a dielectric material interposed between each of them and the surfaces associated with them for the reason that a capacitor is effectively formed by the electrode, dielectric material and the body surface in each instance. This so formed capacitor will effectively block DC components.

Generally, the current at the tissue level, the current waveform of FIG. 4 results by placing the output voltage appearing at terminals 20 and 22 across a capacitor in series and/or parallel with an impedance. The capacitor is formed by the double layer capacitance between electrode plates 50 and 52 placed on the surfaces of the body and the ionic species in the tissue fluids; the impedance is the impedance of the tissue to ionic migration through it and all other electrochemical processes involved, e.g., redox reactions, adsorption and desorption processes. The bipolar voltage at the tissue level, the voltage drop waveform of FIG. 4, is the result of the voltage drop, caused by the current flow, across the impedance of tissue and body fluids.

It is believed that the apparatus of FIG. 1 functions for the purposes disclosed because during the sawtooth's upgoing ramp (its rise time, X in FIG. 3), the magnitude of the current and the amplitude of the resulting bipolar voltage at the tissue level the sharp spike Y in FIG. 4, is above that necessary for effecting the desired stimulation, i.e., above that level necessary to effect the bioelectrical signal. The magnitude of the current and the amplitude of the bipolar voltage (FIG. 4 delineated by the points CD) which are generated at the tissue level are below the level necessary to effect stimulation, i.e. below that level to effect the bioelectrical signal.

Hence, the electrode plate 50 or 52 nearest the desired zone of treatment appears to be negative or positive to the adjacent cells or tissue. This result is achieved notwithstanding the fact that the average current flowing through the system is zero. The preselection of the location of the negative or positive polarity electrode with respect to the adjacent body surfaces will be more fully explained hereinafter. Generally, however, one of the electrode plates 50 or 52 is placed closer to the desired zone of treatment with respect to the other electrode plate. The preferred location of the electrode plates 50 and 52 is adjacent to the epithelial surfaces of the living body or patient under treatment. The term "adjacent to" as used herein means adjacent or, adjoining, or contiguous, or coterminous, or abutting. As for example, when the plates 50 and 52 are in direct physical contact with the body surfaces, the plates would be contiguous with the body surfaces, however, when a dielectric material is interposed between the plates and the body surfaces, the plates would be adjacent or near, that is, in close proximity to the body surfaces.

It is to be understood, however, if desired, the electrodes 50 and 52 may take a form which would allow them to be embedded in the zone of treatment. That is, both of the electrodes may be in the form of needle like electrodes or, alternatively, one may be needle like and the other electrode may take the form of a plate. However, as stated, the preferred location of the electrodes is external to the epithelium of the living body. A surgically non-invasive technique is preferred because in this manner the signals generated by the circuit of FIG. 1 can be coupled to the zone of treatment without creating a discontinuity in the epithelium thereby avoiding the risk of superficial and deep infection in the patient during the treatment.

Also, it may be explained that while the preferred form of the power supply 23 is a battery comprising one or more electrohemical cells, other suitable known electrical power supplies may be utilized. The entire circuit of FIG. 1, if desired, may be cast in a potting compound compatible with the environment of the body with or without the inclusion of the power supply. In this latter instance, the power supply would be operatively connected to the electrical circuit through suitable terminals provided in the casting. This feature allows the batteries to be replaced, if needed, during treatment, and it also permits the reuse of the electronic circuit components which would not normally be the case if the batteries were encapsulated along with the components making up the ciruit of FIG. 1. Furthermore, one of the electrodes 50 or 52 can take the form of a plate secured to the casting encapsulating the electronic components. Of course, in this case, the plate would be appropriately connected to the electronics within the encapsulation container. Similarly, one or both of the electrode 50 or 52 may be adapted to the form of a split, wall of a splint, cast or bandage around the zone of treatment. It should also be pointed out here that the circuit of FIG. 1 may also be cast or potted in a material compatible with the enviroment of materials utilized in the formation of casts for broken or fractured limbs and other body parts. The reasons for this being that, if desired, the circuit of FIG. 1 may be embedded within the cast used to immobilize or support the limb or other body part having a broken or fractured bone.

The encapsulated circuit of FIG. 1, may also be wholly implanted within the body of the patient under treatment if so desired. In this latter instance, a coating of silicone rubber or other like material may also be employed. That is, the potting material may have a wafer-like envelope of silicone rubber formed thereabout.

Referring now to FIG. 2, the coils 50a and 52a may be constructed of any conducting or semi-conducting material. The essential requirements for the coils are:

1. That they be placed so that they do not necessarily touch the body surfaces involved and so the associated electromagnetic field produced by them, while varying, produces voltage loops and induces circulating currents in the desired location(s); and,

2. That the coils be constructed of a material that does not offer an excessive impedance to the flow of current at the rates of voltage change normally associated with this circuit.

The preferred embodiment for the coils 50a and 52a is silver, although other suitable materials, as for example, copper may be utilized.

The preferred placement of the coils relative to the injury is such that the most concentrated electromagnetic lines of force pass through the injury site at right angles to the direction of preferred current flow, as will be explained more fully hereinafter. These coils are also preferably configured and placed so as to diffuse the current flow in those regions of the body or the surrounding tissue not in close proximity with the injury site.

Referring now to FIGS. 2, 3, and 4 the undulating output voltage produced by the circuit of FIG. 2, as stated above, appears across the terminals 20 and 22 and is illustrated as the sawtooth waveform shown in FIG. 3. As stated above, the amplitude of the output voltage produced by the circuit of FIG. 2 is the same as that produced by the circuit of FIG. 1, moreover, the shape of the waveform is substantially the same and, for purposes of explanation, FIGS. 3 and 4 will be utilized again, only at this point with reference to FIG. 2. The undulating output voltage is capacitively coupled to the operational amplifier 47 via capacitor 43. Actually, the capacitor 43 may be omitted from the circuit of FIG. 2, if desired, because, due to the inductive coupling of the output voltage to the load 25 in this instance, no DC components can appear in the load 25.

As a result of the undulating output voltage or sawtooth waveform being placed across coils 50a and 52a, there is produced an undulating current in the coils 50a and 52a which effects an undulating time verying electromagnetic field in the vicinity of the load 25, that is, a sawtooth waveform modulated electromagnetic field, which, due to the placement of the coils relative to the load 25, is coupled to the load 25.

The waveform of the signal(s) appearing in the load 25, as stated above, is illustrated in FIG. 4. The waveform illustrated in FIG. 4, as stated above, is representative of the voltage drop and induced current waveforms at the tissue level. It will be understood to those skilled in the art that the comments made above with respect to the waveforms shown in FIGS. 3 and 4 as to the bipolarity of the voltage appearing in the load, and as to what a Fourier analysis of these waveforms would show are applicable hereto.

Generally, the voltage loop results at the tissue level by placing the sawtooth waveform modulated electromagnetic field produced by the coils 50a and 52a across the tissue at right angles to the desired direction of current flow at the tissue level. This voltage loop results in current flow which in turn effects the bipolar voltage at the tissue level. The voltage drop and current waveform of FIG. 4, is the result of the voltage drop, caused by the current flow, across the impedance of tissue and body fluids.

It is believed that apparatus of FIG. 2 functions for the purpose described because during the sawtooth's upgoing ramp (its rise time, X in FIG. 3), the amplitude of the resulting bipolar voltage at the tissue level (the sharp spike in FIG. 4) is above that necessary to effect the bioelectrical signal. The magnitude of the current and the amplitude of the bipolar voltage (FIG. 4 delineated by points CD) which are generated at the tissue level during the sawtooth's fall time (Z in FIG. 3) are below the level necessary to effect stimulation, i.e., below the level necessary to effect the bioelectrical signal. Hence, the potential drop through the tissue appears, to the intervening cells, to have a polarity associated with it, that is, one end or portion of the zone under treatment appears to be positive while the other end or portion appears to be negative to the intervening cells even though the average current flowing through the system is zero.

At this point, it may be explained that, generally, the coils 50a and 52a are placed relative to the desired stimulation zone so as to maximize electromagnetic field strength within this zone. The preferred location of the coils 50a and 52a is adjacent to, but not necessarily touching the surface of the skin of the patient under treatment, however, if desired, the coils 50a and 52a may take a form which would allow them to be placed on the surface of the skin of the patient or a form which would allow them to be embedded in the zone of treatment. Both of the coils may be in the form of thin taper edged planar coils or, alternately, one may be of the taper edged planar geometry while the other coil may take the form of a small ferrite cored inductor.

Also, it may be explained that the power supply 23 together with 68V power supply for the operational amplifier 47 is a battery or batteries each comprising one or more electrochemical cells. Other suitable electrical power supplies may be used, if desired. The entire circuit of FIG. 2 if desired, may be cast in a potting compound compatible with the environment of the body (human body included) with or without the inclusion of power supply. In this latter instance, the power supply would be operatively connected to the electrical circuit through suitable terminals provided in the casting. This feature allows the batteries to be replaced, if needed, during treatment, and it also permits the resue of the electronic circuit components which would not normally be the case if the batteries were encapsulated along with the components making up the circuit of FIG. 2. Furthermore, each of the coils 50a and 52a can take the form of a wire wound bobbin secured to the casting encapsulating the electronic components. Of course, in this case, the coils would be appropriately connected to the electronics within the encapsulation container. Similarly, each of the coils 50a and 52a may be adapted to the form of a splint or wall of a splint, cast, or bandage around the injured area. It should also be pointed out here that the circuit of FIG. 2 may also be cast or potted in a material compatible with the environment of materials utilized in the formation of casts for broken or fractured limbs and other body parts. The reason for this body, that, if desired, the circuit of the invention may be embedded within the cast used to immobilize or support the limb or other body part having a broken or factured bone.

The encapsulated circuit of FIG. 2, may also be wholly implanted within the body of the patient under treatment if so desired. In this latter instance a coating of silicone rubber or other like material may also be employed. That is, the potting material may have a wafer-like envelope of silicone rubber formed thereabout.

However, as stated, the preferred location of the coils in external to the epithelial surfaces of the body because a surgically non-invasive technique is the preferred mode of coupling the electrical energy to the living body utilizing the principles of the present invention.

While emphasis, thus far, has been given to the therapeutic treatment of bone tissue as a specific example of the use of the devices of the invention, it is to be understand that the bioelectrochemical activity at cell-membranes lends itself to external control. Therefore, the bioelectrochemical devices of the invention, in all of their forms and obvious modifications, may be capble of having a beneficial healing influence in the following areas:

1. Growth

2. Remodeling

3. Therapeutic Pain Control

4. Therapeutic Muscle and Nerve Control

5. Infection

These possible areas of use are given only by way of example and not by way of limitation. These possible areas of use means that the devices of the invention may possibly be used for such things as bone repair or fracture healing, soft tissue repair and thrombosis. In other words, all of those biological processes which exhibit abnormal electrical behavior may be beneficially influenced by a "correctly programmed" bioelectrochemical apparatus. The term correctly programmed bioelectrical apparatus as used herein includes those devices for generating an undulating output voltage having a waveform whose rise time is different from its fall time and wherein the output of the devices can be programmed via the structural makeup of the devices to a specific frequency range.

Consequently, with respect to the circuits of FIGS. 1 and 2, the term correctly programmed is meant to include variations in the frequencies, the duty cycles, the rise times, the fall times, and also the polarity of the output voltage produced by the circuits of FIGS. 1 and 2. Those skilled in the art will recognize that these factors determine the characteristics of the output voltages produced by the circuits of FIGS. 1 and 2. With respect to duty cycle, rise time and frequency, the variations may be accomplished by varying resistor 30, capacitor 28 and supply voltage 23; with respect to fall time, variations may be effected by changing the inductance of the transformer windings, i.e., susbstitution of one transformer for another; with respect to polarity variations, these may be effected by reversing the transmission means 54 and 55 in the case of the circuit of FIG. 1 or transmissioon means 54 and 56 in the case of the circuit of FIG. 2.

Furthermore, in the case of the circuit of FIG. 1 correctly programmed is meant to include positioning, electrode plate area and electrode plate geometry. That is, these latter factors govern the strength and area over which the energy is transmitted from the circuit of FIG. 1 to the predetermined zone of the living body under treatment. In the cases of bone healing, and wound healing, for example, the preferred embodiments of the plate electrodes is a geometry in which the working or negative electrode plate 52 is over the area under treatment and the counter or positive electrode plate 50 is placed over an area remote from the area under treatment. In general, the working electrode or the electrode plate which is to effect the desired healing effect is about one-fifth the area of the counter or opposite electrode plate and the electrode plate configuration is chosen so that the concentrations of the electric field is as close to the desired area of treatment as possible.

In the case of the circuit of FIG. 2, correctly programmed is meant to include positioning, coil volume and coil geometry. That is, these latter factors govern the strength and area over which the energy is transmitted from the circuit of FIG. 2 to the zone of tissue of the living body under treatment. In general, the therapeutic coil geometry is chosen so that the highest concentration of the field, that is, the maximum flux density is as close to the desired area of treatment as is possible.

Referring now to FIG. 5, there is illustrated an electrical medical device of the type shown in FIG. 1 with a patient on which it is being used, parts of the patient have been schematized. The working or negative electrode 52 is adjacent to the area under treatment and the counter or positive electrode 50 is located remote from the area under treatment. The block 100 is to be taken as representative of a circuit that will generate an electrical signal undulating in both the positive and negative directions and having a waveform whose rise time differs from its fall times. With such an arrangement, during the undulations of the driving signal produced by the circuit of block 100, current flow will be effected in the part 102 of the patient under treatment. The magnitude of the current will be higher in the direction moving from the proximal region of the part 102 to the distal region of the part 102 than vice versa. The magnitude of the larger current will correspond to the current signal shown in FIG. 4 delineated by the points ABC and the smaller magnitude of current, moving in the direction from the distal region to the proximal region of the part 102, will correspond to the current signal shown in FIG. 4 delineated by the points CD. As a result of this current flow there will be established a bipolar voltage within and across the zone of treatment undulating both in the positive and negative directions with the maximum amplitude of the bipolar voltage in one direction being greater than the maximum amplitude of the bipolar voltage in the opposite direction, i.e., corresponding to the voltage drop waveform of FIG. 4. The bipolar voltage thus established in the area of treatment is of a predominantly negative polarity which increases the absolute value of the naturaly occurring electrical potential of the area under treatment which, it is speculated, may be comulative with the naturally occurring change of potential, which occurs at injury, to enhance and speed the repair mechanism with faster rates of recovery to the injured bone.

Referring now in FIG. 6, there is illustrated an electrical medical device of the type shown in FIG. 2 with a patient on which it is being used, parts of the patient have been schematized. A single coil 202 is illustrated and it is placed over the area of treatment so that it is as close to the area of treatment as is possible. The block 200 is to be taken as representative of a circuit that will generate an electrical signal undulating in both the positive and negative directions and having a waveform whose rise time is different from its fall time. With the arrangement shown in FIG. 6, during the undulations of the driving signal produced by the circuit of block 200, there is produced an undulating current in the coil 202 which in turn effects an undulating time varying electromagnetic field which, due to the placement of the coil 202 relative to the part 102 of the patient, is coupled to the part 102. A voltage loop results at the tissue level which in turn results in current flow in the part 102 which current in turn effects a bipolar voltage with and across the part 102 of the patient. The electromagnetic field produced by the coil 202 is at right angles to the desired directions of current flow and the current flow undulates in both the positive and negative directions in the part 102 of the patient. The magnitude of the current flow moving in the direction from the proximal region of the part 102 to the distal region of the part 102 will be greater than the magnitude of the current moving from the distal region to the proximal region of part 102. The greater current corresponds to the current signal shown in FIG. 4 delineated by the points ABC, and the smaller current corresponds to the current signal delineated by the points CD. As a result of this current flow there will be established a bipolar voltage within and across the zone of treatment undulating in both the positive and negative directions with the maximum amplitude of the bipolar voltage in one direction being greater than the maximum amplitude of the bipolar voltage in the opposite direction, i.e., corresponding to the voltage drop waveform of FIG. 4.

The bipolar voltage thus established in the area of treatment is of a predominantly negative polarity which increases the absolute value of the naturally occurring electrical potential of the area under treatment which it is speculated, may be comulative with the naturally occurring change of potential, which occurs at injury, to enhance and speed the repair mechanism with faster rates of recovery to the injured bone.

It will be understood to those skilled in the art, that, while only electronic circuits have been shown, a mechanical device capable of generating either an undulating electrodynamic or electromagnetic field which rises and collapses in accordance with a preselected frequency with the time period of the rise of the field being different from the time period of the collapse of the field will effect a current at the tissue level in accordance with the teachings of the present invention. Such a mechanical device is shown in schematic form in FIG. 7. In FIG. 7, 302 is a magnet rotating about an axis 304. The element 306 is a sheet of material impervious to the magnetic field of rotating magnet 302 and the element 306 has a triangular shaped opening 308 therein. It will be understood to those skilled in the art that as magnet 302 rotates past opening 308 an electromagnetic field will be created on the otherside of the element 308 which rises and falls in accordance with the rotational speed of magnet 302. Furthermore, the created magnetic field will rise and collapse at different time periods due to the triangular shaped opening 308.

It is to be borne in mind that the broadest aspects of the present invention are the treatment of cells of a living body by utilizing the interfacial properties of cell-membranes which means that cell-membranes behave an electrodes. Consequently, cell-membranes will respond to local potential variation. Although because of their particular geometry and specific sensitivities, nerve cells may be among those cells most affected by the above described local potentials, the intent of this invention is not to solely stimulate nerve cells, although this may be a required step in the healing process, but also to stimulate any other susceptible variety of cells or tissue necessary to achieve the desired end effects of healing of desirable tissue types.

While the allusion has been made throughout this specification to specific mechanistic phenomena associated with cell and tissue healing, it is to be understood that the inventor in many instances does not have full awareness of the actual processes involved. Those that have been set forth were merely attempts at an explanation for the reason that the devices described are operative for the purposes disclosed.

In a practical embodiment of the invention, as shown in FIG. 1, the components described in FIG. 1 can have the values as shown in Table 1.

TABLE 1 ______________________________________ Resistors (ohms) 30 0-1, 000K variable 31 50 k 32 50 k 46 500 k Capacitors (u F) 28 0.047 40 0.0047 43 1.0 Transistors 25 2N718A 26 2N3217 Transformer 34 UNITED TRANSFORMER CORP. No. Bit-250-48 Diode 44 Hewlett Packard HP2800 ______________________________________

In a practical embodiment of the invention, as shown in FIG. 2, the components described in FIG. 2 can have the values shown in Table 2.

TABLE 2 ______________________________________ Resistors (ohms) 30 0-1, 000K variable 31 50 k 32 50 k 46 500 k Capacitors (u F) 28 0.047 40 0.0047 43 1.0 Transistors 25 2N718A 26 2N3217 Transformer 34 UNITED TRANSFORMER CORP. No. Bit-250-48 Diode 44 Hewlett Packard HP2800 Operational Amplifier 47 RCA HC 2000 ______________________________________

While there has been described and pointed out the fundamental novel features of the invention as applied to two embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated and their operation may be made by those skilled in the art, without depending from the spirit of the invention. It is the intention, therefore, to be limited only as indicatd by the scope of the following claims.