Method For Aiding Formation Of Bone Forming Material

Abstract

Method for aiding formation of bone forming material in the region of a bone structure of a living being. Two electrodes are applied to spaced areas on opposite sides of the region of the bone structure. An alternating electric potential difference is applied across the electrodes. This potential difference has a frequency below 100 c/s and a magnitude such that it produces a current density of at most 10 .mu.A/mm.sup.2 at the electrode surfaces in physical contact with the areas.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of Application Ser. No. 26,809, filed Apr. 9th, 1970 now U.S. Pat. No. 3,745,995.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a method for aiding formation of bone forming material in a region of the bone structure of a living being, such as a human being or an animal.

In the medical field it is often desired to speed up formation of bone forming material, e.g. in healing a fracture, or to induce the bone forming material to form at all, as in the case of pseudo-arthrosis or osteoporosis.

The method and apparatus described herein provide the possibility of accelerating the formation of bone forming material and correspondingly reducing the period of time necessary for recovering from a fracture, as well as the possibility of inducing formation of bone where this ability has been impeded by a disorder such as osteoporosis.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a novel method for helping bone disorders to mend, e.g. fractures or osteoporosis or other disorders of the mineral metabolism.

Another object of the present invention is to provide a method for shortening the period of time which is necessary to bring a fractured limb into a state where it can be used again.

A further object of the invention is to provide a method using an improved splint which promotes healing of the splinted fracture and which is simultaneously of reduced size and weight, so that the wound trauma is reduced and the aftereffects of the fracture are alleviated

The method for aiding the formation of bone forming material in a region of a bone structure of a living being includes the application of electrodes on opposite sides of the region of the bone structure and the application to these electrodes of an alternating electrical potential difference having a frequency below 100c/s and a magnitude such that it produces a current density of at most 10 .mu.A/mm.sup.2 at the surfaces of the electrodes.

The alternating electric potential difference which is applied can be unsymmetrical with respect to zero. The alternations of this applied potential difference preferably provides a wave form with gradual slopes. Additionally, this potential difference can have a wave form which is triangular and has a harmonic content below 20 percent. The frequency of the alternating potential difference can be between 1 and 65 c/s.

In the carrying out of this method for aiding the formation of bone material, it is additionally possible to utilize a magnetic field having a direction substantially parallel to the collagene fibers of the bone structure, which assists in the formation of bone material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevation view, partially in cross section, of an apparatus for practicing the method according to the present invention applied to a fractured bone.

FIG. 2 is a schematic perspective view of an embodiment of a splint for practicing the present invention and attached to a broken bone.

FIG. 3 is an enlarged cross-sectional view taken generally along the line III--III in FIG. 2.

FIG. 4 is a somewhat enlarged cross-sectional view taken generally along the line IV--IV in FIG. 2.

FIG. 5 is a schematic elevation view, partly in cross section, of a further embodiment of a splint structure.

FIG. 6 is a schematic view, partly in cross section of still another embodiment of a splint applied to a fractured bone to be mended.

FIG. 7 is a schematic perspective view of yet another embodiment of a splint structure attached to a broken bone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

There is shown in FIG. 1 a bone 10 of a living being, e.g. a femur (thigh bone) of a human being, which has gaps 12, 14 caused by a fracture.

The parts of the fractured bones are fixed in the normal position by means of two opposed splints 16,18 which may be fixed to the parts of the broken bone by means of screws as usual in the medical art. The splints may be made of a stainless steel material or a Co-Cr-alloy known as "Vitallium" and may have the form of a curved plate.

To the main surface of splint 16, which is opposite to the bone 10, is attached a pick-up arrangement which includes a rod-like magnetic core 20 bearing three pick-up coils 22,24, 26. The core and the coils are encapsulated in an appropriate plastic material 28. The core is made of a material having low reluctance, such as a magnetically soft ferrite or Permalloy. A first terminal of coil 22 is electrically connected, or d.c. coupled to splint 16, and the second terminal of coil 22 is connected through an insulated wire 30 to two rod-like electrodes 32. The insulation of the wire 30 extends up to the point where the conductor enters the bone 10, or more specifically the gap 12 between the bone portions separated by the fracture.

The first (the upper in FIG. 1) terminal of coil 24 is connected to an insulated wire which passes into the bone 10 through a hollow screw 34 insulated against the splint 16. The wire extends preferably into the endostale bone or marrow cavity of the bone 10 and is bare beginning from the point where it leaves screw 34. The other (lower) terminal of coil 24 is connected to a screw 36 which is insulated against splint 16, but has a bare tip which extends into the bone 10, preferably as far as into the endostale bone or marrow cavity, and forms an electrode.

The lower terminal of coil 26 is again connected to splint 16, and the other terminal of coil 26 is connected through an insulated wire 38 both to a rod-like electrode 40, which extends radially into gap 14, and to the second splint 18 which may be fixed to the portions of bone 10 by screws (not shown) in the usual manner.

A tube-like field coil 42 is provided which may be slipped over the broken limb into the position shown in FIG. 1. Field coil 42 comprises a plurality of windings encompassing the broken limb and, thus, magnetic core 20 bearing pick-up coils 22, 24, and 26. The field coil 42 is connected to an a.c. signal generator 44, which may be of known construction and supplies to coil 42 an alternating current, e.g. a sinusoidal current having a low harmonics content which may be less than 20 percent, preferably less than 10 percent or 5 percent. The signal delivered by the a.c. signal generator has a frequency of less than 1000 c/s, preferably less than 100 or 60 c/s, e.g. between 1 or 10 c/s and 40 c/s. The signal generator 44 may comprise a modulator for superimposing higher frequency oscillations onto the basic signal; these oscillations or undulations may have a frequency which is at least three times the frequency of the basic signal.

When excited by signal generator 44, field coil 42 produces an alternating magnetic field symbolized in FIG. 1 by field lines 48 which are picked up by core 20 and induce alternating currents in the coils 22, 24, 26, so that alternating currents or potentials are produced between the spaced electrodes connected to the terminals of said coils. It is these alternating currents or potentials having gradual, gentle slopes, low harmonics content and low frequency, which greatly enhance the formation of bone forming material, or callus. Callus forming rates which are more than three to five times faster than the normal rates have been observed in human beings to which the present apparatus and method were applied for healing a fracture. Further callus formation could be induced in pathological cases where normal callus formation had failed, as in the case of pseudo-arthrosis.

The recovery of the broken bone is further aided by the magnetic field which is produced by field coil 42 and which is essentially parallel to the structural elements of the bone to be formed.

A further embodiment of a splint for use in the present apparatus and method is depicted in FIGS. 2, 3 and 4. Splint 50 has the form of an elongated, curved plate which is attached to a broken bone 52 by screws 54. The splint 50 has a circumferential groove 56 (see FIG. 3) into which one or several pick-up coils 58 are wound. Groove 56 housing the pick-up coil or coils is enclosed with an appropriate plastic material or resin 60, e.g. an epoxy resin. The coil ends extend into bores of the bone or the gaps in the bone caused by the fracture, as shown in FIG. 4. The portion of the wires between the coil proper and the point of entrance into the bone or gap is insulated, e.g. by a teflon insulation, the bare tip of the wire forming an electrode. One of the coil ends may be connected to a screw 54 which may or may not be insulated against the splint.

The pick-up coils cooperate with a field coil (see FIG. 2) which is positioned in the vicinity of splint 50 and functions in a manner similar to coil 42 shown in FIG. 1.

FIG. 5 shows a splint 60 which is externally applied to an injured limb, i.e. to the skin 62 thereof. The splint 60 may be of any suitable material, e.g. a plastic or resin material which is hardened in situ, and comprises pointed spine-like members 64, the roots of which are embedded in the material forming the splint 60 proper. The pointed ends 66 of members 64 are inserted into the broken bone 68, preferably as far as the marrow channel as shown in FIG. 5, to fix the bone in its proper position. Simultaneously, the pointed ends 66 being of metal serve as electrodes and are connected to respective pick up coils 70 which are similar to those described in connection with FIG. 2. The portions of members 64 which are outside of bone 68 are insulated against the tissue 72 surrounding the bone 68. In operation, a current is induced in coils 70, e.g. by a pick-up coil as shown in FIG. 2 or by the stray-fields which exit in the environment and are caused by the mains, electrical appliances, and so on.

FIG. 6 shows a splint according to the present invention which is in general similar to the splint shown in FIG. 5 and comprises a plastic or resin material 80, shaped and cured in situ on the skin 82 of the outer side of an injured hand comprising broken bones 84. The main difference between the splints according to FIG. 5 and 6 respectively, is that a capacitor 88 is connected in parallel to pick-up coil 86 for tuning it to the frequency of the induced currents. The capacitor 88 is embedded in material 80 and provides for an especially low harmonics content of the induced signal, which will produce a purely sinusoidal current.

As noted above, a major advantage of the present invention is that callus is formed so quickly that the broken bone will be able to recover to a substantial portion of its original strength in a relatively short time, so that the splint need not supplement the load carrying function of the bone when the injured individual has otherwise recovered sufficiently to be able to get up again. Thus, the splint is only needed for fixing the broken bone in the proper position during the initial stage of healing and can be made much lighter and thinner than the presently used splints. The screws used to attach the splint to the bone may be correspondingly smaller, which greatly reduces the wound trauma and the aftereffects which arise after removal of the splint; e.g. the filling of the screw holes with bone forming material. Further, the use of the so-called Kuentscher-nail (a rod-like supporting element, inserted into the marrow-channel of a broken bone) may be dispensed with.

FIG. 7 shows a novel splint of such reduced dimensions, the splint comprises a curved plate-like member 90, made of stainless steel or "Vitallium", to which pick-up coil means 92 wound around a magnetic core 94 are attached. Member 90 may be made of sheet material having a thickness of 1 to 2 mm in contrast to 4 to 6 mm in the known splints. Member 90 is connected to one terminal of each of the coils making up coil means 92 through an unsymmetrically conducting device 99, such as a diode, to make the shape of the current wave unsymmetrical. Preferably, member 90 is positive during the current periods having the higher amplitude.

Pick-up coil means 92 is connected by insulated leads 96 to bare, slender, rod-like electrodes 98 adapted for insertion into a bone structure (e.g. as shown in FIG. 4) to aid forming or regeneration of bone material.

The electrode portions which are in contact with the bone structure consist preferably of a noble-metal alloy, e.g. an alloy of 90 percent by weight Pt and 10 percent by weight Ir, or stainless alloys such as Co-Cr-alloy known as "Vitallium". The insulation may consist of Teflon, and all of the materials which are in contact with bone or tissue are of course so chosen that they are compatible with the environment and the living or organic matter.

The induced current which enters into the bone region may consist, e.g., of a sinusoidal wave having low harmonics content, a triangular wave, a series of triangular or essentially sinusoidal pulses of alternating polarity, the pulses being separated by periods of time during which the current is zero or negligible. The waveforms or pulses need not to be symmetrical.

The invention is not limited to healing fractured bones, it may be applied with success also for curing other bone disorders where forming of bone material is to be enhanced or promoted. Thus, the invention may be applied, e.g., to curing osteoporosis, regenerating bone structure destroyed by a tumor, to cure an illness known as "Sudeck'sche Atrophia" and so-called false articulations (pseudo-arthrosis).

The pick-up coil means may also be positioned adjacent the peripheral edge, e.g. at the straight long edge portion, of the plate member of the splint.

EXAMPLE I

A novel splint similar to that shown in FIG. 2 was attached and electrodes, which were in the form of needles consisting of a platinum-iridium alloy, were applied as shown in FIG. 4 to the broken right femur (upper thigh bone) of a rabbit. A similar splint and similar electrodes, however, without being connected to a pick-up coil or other current source were applied to the like-wise broken left femur of the same animal. This was carried out in an operation under narcosis lege artis. The animal was kept in a barn within which an electric a.c. field was maintained producing in the windings of the pick-up coil an a.c. current of sinusoidal waveshape and a frequency of 25 c/s. The maximum current density at the areas of contact between the electrodes and the tissue or bone was about five microamperes per square millimeter. After having been kept in the electric field for three weeks, the rabbit was killed and sections of the bones in the planes of the electrodes were prepared. The sections showed that at least three times as much callus had formed in the area of those electrodes which were connected to the pick-up coil in comparison with the area connected to the other, currentless dummy electrodes.

EXAMPLE II

Similar results as in Example I have been achieved in mending an injured bone of a human being: A splint similar to that shown in FIG. 7 (without diode 99) was applied to the femur of a male (age about 50) which had been injured in a car accident about one year ago. The fracture did not heal because callus did not form by itself.

The applied novel splint comprised a metal plate of usual size to which a pick-up coil was attached having 200 windings of teflon-insulated platinum wire (diameter 0.1 millimeters) wound on a magnetic core consisting of two superimposed "Permalloy" sheets each having a length of 50 mm, a width of 4 mm and a thickness of 0.5 mm. The electrodes connected to the terminals of the pick-up coil and inserted into the gap of the fractured bone were needle-like members consisting of an alloy of 90 percent by weight platinum and 10 percent by weight iridium and having a diameter of about 0.5 to 1 mm.

A field coil was put around the splinted limb and excited by a sine-wave a.c. current of 25 c/s to produce an a.c. field of about 800 ampere-turns in the region of the pick-up coil.

After the splinted limb had been kept in the electric field and treated as described for 14 days, an x-ray investigation showed that plenty of new callus has formed in the area around and between the electrodes.

The patient who was regarded as incurable before the described treatment eventually completely recovered.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

Claims

I claim:

1. A method for aiding formation of bone forming material in the region of a bone structure of a living being, the method comprising the steps of:

a. positioning at least two electrodes into physical contact with spaced areas on opposite sides of the region of the bone structure;

b. applying an induced alternating electric potential difference across the electrodes, the potential difference having a frequency below 100 c/s and a magnitude such that it produces, at the electrode surfaces in physical contact with the areas a current density of at most 10 .mu.A/mm.sup.2.

2. A method as defined in claim 1 further comprising the step of producing, in the region, an alternating magnetic field having a direction substantially parallel to the collagene fibers of the bone structure.

3. The method as defined in claim 1 wherein alternations are used which are unsymmetrically in respect to a zero value.

4. The method as defined in claim 1 wherein the alternating electrical potential difference has a wave form with a harmonics content below 20 percent.

5. The method as defined in claim 1 wherein the alternating electric potential difference has a triangular wave form.

6. The method as defined in claim 1 wherein the alternating electric potential difference has a wave form consisting of pulses of alternating polarity.

7. The method as defined in claim 1 wherein the alternations have a wave form with gradual slopes.

8. The method as defined in claim 1 wherein the potential difference has a magnitude to produce a current density between 3 and 7 .mu.A/mm.sup.2 at the electrode surfaces in physical contact with the body substance areas.

9. The method as defined in claim 1 wherein the alternations have a frequency between 1 and 65 c/s.

10. The method as defined in claim 1 wherein the alternations have a frequency between 10 and 30 c/s.

11. The method as defined in claim 1 wherein the living being is a human being.

12. The method as defined in claim 1 wherein the spaced areas, at which the electrodes are applied, are disposed within the skin and are formed by internal body substance including soft tissue and bone substance.