ELECTRIC HEALING DEVICE

Abstract: Electric healing device (5, 30, 40) having a DC power supply, an anode (6, 16, 41) and a cathode (7, 14, 19, 33, 45) to supply a physiologically acceptable current to heal wounds and/or stimulate bone growth. The anode (6, 16, 41) is either titanium or anodised titanium. A method and an anode are also disclosed.

Description: "ELECTRIC HEALING DEVICE" The present invention relates to an electric healing device, which uses an unexpected property of titanium and/or anodised titanium. BACKGROUND ART The healing of fractured bones, and wounds in or on living bodies by means of applying low intensity direct current to the affected area is well known. See for example U.S. Patent Nos. 4 333 469, 4 019 510, 3 745 995, 3 783 880, 3 918 440, 3 915 151, 3 890 953, 3 964 473, 3 749 101, 3 472 233, 3 918 459, 3 386 445, 3 842 841, 3 820 534 and 3 964 477. These specifications disclose the use of metal electrodes to supply current to the area to be healed. However, the properties of titanium, were up until now held to be undesirable when titanium was to be used as an anode. The reasons being that in an anodic role, titanium will become anodised. The titanium oxide layer thereby created on the surface of the anodised titanium was previously Considered to be such a severe impedance to current flow as to render the material unsuitable for use in an anodic role. DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is disclosed an electric healing device, comprising a DC power supply having a positive terminal and a negative terminal, an anode connected to said positive terminal, and a cathode connected to said negative terminal, said anode and cathode being adapted for connection to a living body characterised in that said anode comprises titanium. According to another aspect of the present invention there is disclosed a method of healing wounds in skin, or soft tissue or of stimulating bone growth, said method comprising the step of passing a physiologically acceptable direct current through the area of the body to be healed or stimulated between an anode and a cathode characterised in that said anode comprises titanium. A titanium anode is also disclosed. The cathode can be formed from any suitable material and the metals titanium, stainless steel and silver are preferred. In the ionic medium of a living body and at body heat a titanium anode quickly anodises and thereby causes an initially high current to drop to a low stable value. Thus it is desirable to anodise the anode prior to use for two reasons. Firstly the steady state current of the healing device can then be checked within a few minutes of application of the device. Secondly, the layer of titanium oxide produced by the anodising protects the titanium anode from possible contamination by other metals. Preferably to provide a low cost DC power supply with inherent short circuit protection a battery and series resistor are used. The preferred battery is a lithium iodide cell having a voltage of from approximately 2.4 to approximately 3.6V. However power supply voltages between 1 and 6V are adequate. Where an anodised titanium anode is used the anodising voltage should be greater than or equal to the power supply voltage and preferably from 10 times to 1 times the power supply voltage. The preferred value for the abovementioned power supply resistor is 47 kilohms however resistors in the range of from 1 kilohm to 100 kilohms produce adequate results. The preferred range of current levels which are physiologically acceptable are from 1 microa p to 50 icroamps using a titanium cathode, however, with a silver cathode a current between 3 nanoamps and 200 nanoamps is preferred. The healing device of the present invention is applicable to the healing of wounds in skin, such as decubitus or leg ulcers and wounds in soft tissues. The healing device is similarly applicable to the promotion of bone growth not only at fracture sites in the healing of broken bones but also in dentistry with the permanent fixing of titanium (or anodised titanium) structures into the bone of the jaw. WI BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the apparatus of the present invention will now be described with reference to the following drawings wherein: Fig. 1 is a plan view of a first embodiment, Fig. 2 is a side view of the embodiment of Fig. 1, Fig. 3 is a cross-sectional view of a second embodiment of the present invention, Fig. 4 is a side view of a third embodiment, Fig. 5 is a schematic side view of a fourth embodiment for stimulation of bone growth; and Fig. 6 is a view of an i plantable fifth embodiment for stimulation of bone growth. BEST MODE OF CARRYING OUT THE INVENTION Illustrated in Figs. 1 and 2 is a pliable, bandage like, electric healing device 5, which comprises an anode 6, made. of titanium or anodised titanium; a cathode 7, made of any suitable cathodic material such as stainless steel or silver but preferably the same unanodised metal as the anode 6 (i.e. titanium). The anode 6 and cathode 7 are preferably formed from woven mesh or light gauge sheet and are attached to a pliant base 8, so as to enable the anode 6 and cathode 7 to be applied to a damaged tissue area. However, if desired the anode 6 and cathode 7 can be attached to separate bases. The base(s) can also be adhesive. A DC power source or battery 9 is connected in series with a resistor 10 between the anode 6 and cathode 7. The resistor 10 is preferably connected between the anode 6 and the positive terminal of the DC power source 9. The function of the resistor 10 is to enable medical staff and technicians to easily determine in situ whether or not the device 5 is operational. This is done by applying a voltmeter across the terminals of the resistor 10. The healing device 5 is applied to a wound (not shown) by placing the cathode 7 and anode 6 in such a position so as to allow the flow of electric current through the damaged tissue. For example, in the case of an acute wound, the anode 6 and cathode 7 are applied to either side of the - 4 - wound to accelerate healing. However, in the case of chronic wounds such as decubitus or leg ulcers it is more expedient to place the cathode 7 on the damaged tissue, and the anode 6 at a suitable distance away from the damaged tissue. Medications can be applied to the damaged tissue as would normally be done in general or specific procedure. However the medication need not be electrically conductive so long as there is an electrically conductive medium between the skin and the anode. The DC power source 9 must be of a voltage, less than, or equal to, the anodising voltage of the titanium if anodised titanium is used. The DC power source 9 is preferably a lithium iodide cell. Fig. 3 illustrates a second embodiment of the present invention which comprises a battery cell 20, with a titanium anode 6 and a cathode 14 insulated from each other by spacers 21. The cathode 14, anode 6 and spacers 21 contain the cell electrolyte 12 within the cell 20. The cell 20 can be applied to damaged tissue by placing the cathode 14 on the tissue and connecting the anode 6 by any conventional circuitry which allows a current in the physiologically acceptable range to pass through the damaged tissue. A third embodiment of the present invention is illustrated in Fig. 4, and comprises a metal cathode 19, a DC power supply 18, a titanium or anodised titanium primary anode 17 and a secondary anode 16. Intermediate the primary anode 17 and the secondary anode 16 is a conducting medium 15. Preferably the medium 15 takes the form of an ionic gel, conductive plastics body or even a strip of gauze impregnated or dipped in a saline solution. The secondary anode 16 can be a metal plate, a block of carbon or any other conductor. It is not necessary for the secondary anode 16 to be titanium or anodised titanium. This embodiment is applied to damaged tissue in substantially the same manner as the two previous embodiments. The embodiments of Figs. 5 and 6 relate specifically to the electrical stimulation of bone growth. As illustrated in Fig. 5 a bone growth stimulator 30 comprises a housing 31 incorporating a titanium anode (not illustrated) in contact with the skin 32 and a self-contained power source (also not illustrated). A cathode 33 is connected by a lead 34 between the housing 31 and a fracture site 35. The cathode lead 34 is placed percutaneously through the skin 32 and an uninsulated portion 36 of the lead 34, being of titanium or stainless steel or some other suitable material, is placed in the fracture site 35. The placement is carried out by a percutaneous needle or any other suitable means. Turning now to Fig. 6, an implantable bone growth stimulator 40 comprises a titanium or anodised titanium case 41, housing two batteries 42 connected in series. The number of batteries 42 used is dependent upon the respective rating of the batteries and the voltage required. One of the batteries 42 is insulated by a cylindrical spacer 48 from the case 41 and the positive terminal of the other battery 42 is electrically connected to the case 41. A resistor 43 is connected in series with the batteries 42 and a cathode 45. The resistor 43 limits the short circuit current of the stimulator 40 in the event that the uninsulated portion 47 of the cathode 45 accidentally momentarily comes into contact with the case 41. Furthermore, the resistor 43 limits the maximum current when the stimulator 40 is implanted, especially if, for example, some of the anodised coating on the case is removed during the surgical procedure to implant the stimulator 40. Preferably the resistance of the resistor is 47,000 Ohms, which will limit the current to a maximum of 50 microamperes, and would allow, within a period of approximately from 1 to 30 mintues, the current to fall to within a physiologically acceptable range of approximately 1 to 20 microamperes. The batteries 42 and the resistor 43 are encapsulated within the case 41, in a water resistant material 46. The OM water resistant material 46 can be of any suitable material such as wax, epoxy resin or a silicone rubber composition and functions to prevent ionic contamination of the ciruit comprising the case 41, batteries 42, and resistor 43. The cathode 45 sealingly exits the case 41 at 48 and is of any suitable length to implant the uninsulated portion 47 of the cathode 45 into the bone fracture site (not illustrated). The uninsulated portion 47 can be of any suitable metal such as titanium or stainless steel. The anodised titanium case 41 is placed in softer outer tissue (not illustrated). INDUSTRIAL APPLICABILITY Tests have shown that the final operating current will be determined by the operating voltage, the anodising voltage, the surface area of the anode and the time for which the anode is subjected to the anodising voltage. For example if a 10 square centimetre titanium anode is anodised at 6V, the healing devices will operate at 15-20 microamperes, whilst if anodised at 10V the devices will operate at 12-15 microamperes. Further, if anodised at 15V the operating range of the device will be 8-10 microamperes. These figures are only approximate values and they are also dependent upon the length of time during which the titanium is anodised. The bone growth stimulator 40 of the embodiment of Fig. 6 is preferably comprised of an anodised titanium case having a surface area of approximately 10 square centimetres or less. If the titanium used in the bone growth stimulators is not pre-anodised, the devices will still function satisfactorily, because once the device is implanted, the titanium will anodise itself at the working voltage. This anodisation will occur within a few minutes and the current will not be large enought to cause damage to the tissue, bone or skin with which it is in contact. A further side benefit of the use of anodised titanium is that once the titanium is anodised and depending upon the voltage and period of anodisation, the titanium changes its colouring ranging from a light gold colour to a deep gold-bronze colour. This lends itself to easy identification of an anodised sample of titanium. The foregoing describes only some embodiments of the present invention. However, modifications, obvious to those skilled in the art, may be made thereto without departing from the scope of the present invention. O

Claims: CLAIMS 1. An electric healing device comprising a DC power supply having a positive terminal and a negative terminal, an anode connected to said positive terminal, and a cathode connected to said negative terminal, said anode and cathode being adapted for connection to a living body characterised in that said anode comprises titanium. 2. A device as claimed in claim 1 wherein said titanium anode is anodised with an anodising voltage greater than or equal to the voltage of said DC power supply. 3. A device as claimed in claim 1 or 2 wherein said anode when connected to said living body is in contact with an ionic medium. 4. A device as claimed in any one of claims 1 to 3 wherein said DC power supply comprises a battery and a series connected current limiting resistor. 5. A device as claimed in claim 4 wherein said battery voltage is from 1 to 6 Volts, and said resistor has a value of from 1 kilohm to 100 kilohms. ♦ 6. A method of healing wounds in skin, or soft tissue or of stimulating bone growth, said method comprising the step of passing a physiologically acceptable direct current through the area of the body to be healed or stimulated between an anode and a cathode characterised in that said anode comprises titanium. 7. A method as claimed in claim 6 wherein is direct current is produced by a power supply, said titanium anode is anodised, and the voltage at which is anode is anodised is greater than or equal to the voltage of said power supply. 8. A method as claimed in claim 6 or 7 wherein said anode is in contact with said body via an ionic medium. 9. A titanium anode adapted to be connected to a living body. 10. A titanium anode as claimed in claim 9 adapted for use with direct current. 11. An anode as claimed in claim 10 and anodised.

Inventors: JEFFCOAT KEITH WILLIAM, JEFFCOAT, KEITH, WILLIAM
Applicants: JEFFCOAT KEITH WILLIAM, JEFFCOAT, KEITH, WILLIAM
Application year: 1983
Main classification: A61N1
IPC codes: A61N1