Patent Description:
Fractures are very common types of body trauma. In the United States, approximately <NUM> million fractures occur each year. In England, the fracture incidence for all age groups is <NUM>% every year. Moreover, it is suggested that ><NUM>% of people will experience a fracture in their life time. Bone fractures may be treated either conservatively or surgically. Surgical treatment comprises different methods of fixing the broken bones, such as internally-placed nails, or pins incorporated into an external frame (external fixation). Non-surgical or conservative treatment usually involves different types of plaster casts. A notable proportion of fractures are treated conservatively with cast immobilization.

Meanwhile, <NUM>% to <NUM>% of these fractures show delayed healing or nonunion. The delay unions or mal/non-unions often require further intervention and may cause serious complications, such as pain and functional limitations. Invasive and expensive re-operation is usually necessary to promote bone healing. To reduce the substantial risk of disability and the socioeconomic costs, the development of a method for accelerating fracture healing is becoming more and more important. In some cases, a surgical intervention is also required. A surgical procedure for internally fixating fractured bones with biocompatible and durable implants has widespread acceptance, while reducing the incidence of nonunion and malunion of broken bones. However, bones internally fixated with such implants are susceptible to muscle and nerve damage due to the presence of the implants and have a prolonged recovery time.

<CIT>, as well as related European patent <CIT> describes a PEMF (pulsed electromagnetic field) therapy system that uses a single-coil PEMF transducer for generating PEMF stimulation signals. The coil has a "bi-phasic" operation, such that current flows through it in two directions. A drive circuit recovers the flyback energy from the transducer coil and dumps voltage to an energy recovery capacitance circuit. The transducer is thereby energized and de-energized to provide the electromagnetic field. The single coil transducer may be fabricated on a flexible substrate and the wiring may be formed with printed circuit techniques. The same concepts may be applied to series connected coils. As described in paragraph <NUM> of the European patent, <FIG> illustrates an application of a transducer <NUM> having series-connected coils <NUM>, and is wrapped around the patient's waist. One of the coils <NUM> is placed against the patient's back, and one against the patient's abdomen.

Patent Application Publication No. <CIT>, describes an energy saving circuit configured for electro-magnetic orthopedic therapy, the circuit comprising:.

<CIT> describes, in <FIG>, "Waveforms configured by the miniature control circuit <NUM>. directed to a generating device <NUM> such as electrical coils via connector <NUM>. The generating device <NUM> delivers a pulsing magnetic field that can be used to provide treatment to a target pathway structure such as tissue.

<CIT>, Portable Non-Invasive Electromagnetic Therapy Equipment," describes "a cast-embeddable coil structure which includes a single connector fitting, designed for exposure externally of a completed cast and for removable mounting and electrical connection to a self-contained light-weight rechargeable portable signal generator unit. The signal-generator unit is mounted to the cast only for periods of therapeutic treatment, and it is removably mounted to a less-portable charging unit in intervals between periods of therapeutic treatment.

Published <CIT> discloses, in paragraph <NUM>, a power transfer mechanism <NUM>, such as a coil, located outside a patient's body, which transfers power to a small structure <NUM> placed in a subcutaneous region of the patient's body. The small structure has that electrically stimulate one or more dermatomes of interest under the patient's skin. Similar configurations are described in paragraphs <NUM>, <NUM>, and <NUM>. As stated in paragraph <NUM>, the stimulation by the electrodes modulates the patient's appetite, hunger, and satiety.

<CIT> to Griffith describes "A portable non-invasive apparatus for electro-therapeutic stimulation of tissue and bone healing readily worn and carried by a patient. " He states that "a coil-type transducer is most preferred for treating deep bone fractures," and compares the power needed using "Helmholtz paired coils, simple coil, simple coil oblique to the fracture or solenoid.

The following papers describe controlled studies of the effectiveness of PEMF for treating bone fractures: <NPL>; <NPL>; and Aggelos Assiotis et al, "<NPL>.

The following papers provide reviews of the literature on PEMF treatment of bone fractures: <NPL>; <NPL>); and <NPL>.

Additional background art includes <CIT>, <CIT>, <CIT>, China Published Patent Application <CIT>), South Korea Published Patent Application No. <CIT> (English abstract).

An aspect of some embodiments of the invention concerns an electronic patch that produces pulsed electromagnetic fields to promote tissue healing, and that optionally uses a resonant energy-saving circuit to recycle field energy from one pulse to the next, potentially allowing a smaller and thinner battery to be used, allowing the patch to be thin and flexible.

An aspect of some embodiments of the invention concerns an electronic patch that is placed on the outside of the body, with a coil, or two coils, placed for example on different sides of a limb, or more than two coils, that repeatedly produce pulsed magnetic fields at a target site adjacent to the patch inside the body. The pulsed magnetic fields induce a changing electric field at the target site, which is believed to improve healing of the tissue. The resonant circuit very efficiently transfers the electromagnetic field energy of each pulse into electrostatic energy of a capacitor, which can be stored with almost no losses and converted into electromagnetic field energy again in the next pulse. For example, more than <NUM>% of the field energy is recycled at each pulse, or more than <NUM>%, of more than <NUM>%, or more than <NUM>%, or more than <NUM>%. Optionally, the field energy is converted and stored so efficiently that the dominant energy losses are the ohmic losses from the coil.

The resonant circuit also operates in such a way there is no current, or very low current, in the coil between pulses, so the ohmic losses are almost as low as they can be. For example, the current between pulses is in the range from <NUM> nA to <NUM>µA, while the peak current during a pulse is in the range from <NUM> mA to <NUM> mA, or <NUM> mA to <NUM> A. Low current between pulses may occur because each pulse lasts for only about one half of a wave cycle or one wave cycle at the LC resonance frequency of the coil and the capacitor.

In an exemplary embodiment of the invention, at the beginning of a pulse, the current in the coil is zero, and the capacitor is charged up to an operating voltage that it maintains between pulses. The voltage across the capacitor and coil, in series, is suddenly reversed. Current starts to build up in the coil, and the capacitor starts to discharge, and to charge up with the opposite polarity. The pulse ends when the capacitor is charged up to its operating value with the opposite polarity, and the coil current has returned to zero. The coil current remains at or very close to zero, with no or almost no energy losses, until another pulse is initiated by reversing the voltage again.

Optionally, radiative losses are potentially negligible, because the resonant frequency, which is the dominant frequency of the pulses, is not too high, for example between <NUM> and <NUM>, with the coil not much more than <NUM> wide, very small compared to a wavelength at <NUM> or <NUM>. Optionally, the pulses are very short compared to the time between pulses, for example the duty cycle, the ratio of pulse times to total time, may be less than <NUM>%, or less than <NUM>%, or less than <NUM>%. For example, there may be between <NUM> and <NUM> pulses per second. In addition, the device may operate for only a few hours each day, for example between <NUM> and <NUM> hours a day.

Very efficient use of energy makes it possible to use a battery of relatively low energy storage capacity to power the patch for the full course of treatment, which may be <NUM> to <NUM> weeks, for example. Optionally, there is no need to recharge the battery during this time, and a non-rechargeable battery is optionally used. Not needing to recharge the battery has the potential advantage that the patient doesn't have to make an appointment for that purpose, saving time for the patient and for medical personnel. Furthermore, non-rechargeable batteries are cheaper, and may be smaller for the same capacity, than rechargeable batteries.

The battery may store less than <NUM> milli-amp hours of charge, or between <NUM> and <NUM> milli-amp hours, or less than <NUM> milli-amp hours, at a voltage between <NUM> and <NUM> volts, or between <NUM> and <NUM> volts, for example <NUM> volts, <NUM> volts, <NUM> volts, <NUM> volts, or <NUM> volts. Relatively low voltage batteries may be used if the energy storage requirements are low. Optionally, the battery is less than <NUM> thick, or less than <NUM> thick, or less than <NUM> thick, and fits inside the coil. With such a thin battery, the patch itself can be very thin, for example between <NUM> and <NUM> thick, optionally less than <NUM> thick, or less than <NUM> thick, or less than <NUM> thick.

Optionally the patch is made of a flexible material, such as silicone, or polyimide, or liquid crystal polymer, and is flexible enough and stretchable enough to conform to the surface of a patient's body adjacent to the site of the fractured bone. For example, the radius of curvature of the patch, when it is conforming to the surface of the body, is <NUM>, or <NUM>, or <NUM>, or <NUM>, or <NUM>, and has cylindrical curvature, or positive curvature like the surface of a sphere, or negative curvature like a saddle-shape. Even if the battery is rigid, and the electronics are comprised in a rigid board, the patch can still be relatively flexible because the small size of the battery makes it possible to provide enough space between the battery and the electronics where the patch can bend. Optionally, the electronics comprises printed electronic components that are also flexible. Optionally, a flexible battery is used.

The flexibility of the patch may make it possible for the patch to be directly in contact with the patient's skin, under a cast, if any, which may allow further reducing the current, and the ohmic losses, needed to produce fields of a given amplitude at the bone fracture or other treated tissue. Furthermore, having all the components in a single thin patch may make the treatment more pleasant for the patient, who need not even notice or think about the patch, especially when it is under a cast, in contrast to prior art which uses bulky and very noticeable components, at least some of them outside the cast. Optionally, the patch is under the cast, and has sensors to measure the pressure of the cast. For example, a pressure sensor may be used to measure the pressure, or a blood oxygen sensor in the patch, placed directly against the patient's skin, may indicate if the pressure is too high, interfering with blood circulation. Optionally, a communications link, for example a wireless link, may provide data from these sensors, under the cast, to medical personnel. Alternatively, the low blood oxygen level is communicated to medical personnel by lighting up a warning light.

Healing bone fractures is an important application of the patch, but it is potentially useful also for healing other kinds of tissue, including muscles, tendons, cartilage, and skin (scar tissue), and it may improve the quality of healing, as well as its speed. For example, it may improve the elasticity of healed tendons.

An aspect of an exemplary embodiment of the invention concerns an electronic patch with two coils, wrapped at least partly around a cylindrical body part, for example an arm, leg, hand foot, neck, pelvis or rib cage, with the two coils on different sides of the body part, optionally under a cast. The coils optionally operate in two modes. In one mode, current passes through both coils, and together they produce an electromagnetic field at the bone fracture site, or soft tissue target site, inside the body part. In the other mode, which optionally operates only occasionally, current flows only through one of the coils. The magnetic flux pulse produced by that coil links the second coil, and induces an emf (electromotive force) voltage in that coil, according to Faraday's law, which is detected by the second coil. The measured voltage in the second coil, for a given current in the first coil, provides information on the mutual inductance of the two coils, which in turn provides information on the distance between them, or at least on changes in the distance between them.

In some embodiments of the invention, the information on emf voltage is used to produce electromagnetic fields of a specified amplitude at the bone fracture site by adjusting the current in the coils, even if it is not known in advance exactly how wide the cylindrical body part is, and how far from the coils the target site is. Once the induced voltage in the second coil has been measured, the electronic patch can return to operating in the mode with current flowing in both coils, and the current in both coils set at a level that is calculated to produce the specified level of electromagnetic fields at the target site, whose distance from the coils may be estimated the emf voltage. In some embodiments of the invention, the second coil is only used for measuring the emf voltage induced by the first coil, and only the first coil ever has current in it, to produce electromagnetic fields.

Optionally, the induced emf voltage on the second coil is repeatedly measured over time, and the treatment proceeds. If the coils are getting further apart, this may indicate increased swelling of the body part, which might not be visible underneath the cast, and may indicate that the bone is not healing properly, and that some medical intervention is needed. If the coils are getting closer together, this may indicate that the arm is shrinking more quickly than expected, and the cast is loose, and is no longer effectively immobilizing the body part. In this case, it may be necessary to remove the cast and replace it. If the arm is shrinking faster than expected, that may also indicate greater than expected wasting of muscle, which may call for some medical response.

An aspect of some embodiments of the invention concerns an electronic patch, flexible enough and of suitable size to wrap at least partly around a body part while generally conforming to the surface of the body part, comprising two flexible coils, located on different sides of the body part when the patch is wrapped around the body part, that produce pulsed electromagnetic fields at a target site inside the body part, to promote tissue healing.

An aspect of some embodiments of the invention concerns an electronic patch, comprising a substrate on which is mounted at least one coil with an open region in the center at least <NUM> in diameter in all directions, the coil producing pulsed electromagnetic fields at a target site inside the body, to promote tissue healing, and one or more electronic elements that are substantially opaque to medical x-rays, wherein the opaque electronic elements are mounted away from the center of the open region.

Referring now to the drawings, <FIG> schematically illustrates a top view of an electronic patch <NUM> for treating body tissue with electromagnetic fields, according to an exemplary embodiment of the invention. The components of the patch are optionally imbedded in a substrate <NUM>, made from a flexible bio-compatible material, such as silicone, formed for example in a mold. The components include a coil <NUM>, which in the case of patch <NUM> is circular, and goes around the outside of the patch, which is <NUM> in diameter. In other embodiments of the invention, for example designed to be used on different parts of the body, the patch and the coil may be a different size or shape.

An electronics package <NUM>, and a battery <NUM>, are optionally located inside the coil. The battery supplies electric power to the coil, through the electronics package, and the electronics package includes circuitry that controls pulses of current passing through the coil, including energy saving circuitry that recycles most of the field energy in each pulse, so that the battery for the most part may only have to supply energy to make up for ohmic losses. The battery and electronics package need not be located inside the coil, but this arrangement has the potential advantage of allowing the patch to be more compact, because the size of the coil may be based on the area and depth of body tissue that is being exposed to the electromagnetic fields, and turns of coil that have much smaller radius will generally produce electromagnetic fields that do not extend as deeply or as widely.

Optionally, the battery, if it is small enough, is located off to the side of the center of the coil, or the battery is not inside the coil at all, in order to avoid having the battery block an x-ray view of fracture site or other target site.

It should be understood that the coils shown in <FIG>, and in the other drawings, are drawn schematically, with a few concentric circles representing multiple turns. Also, the connections between different turns, and the connections between different coils or between the coils and other components, are not necessarily shown.

<FIG> schematically shows a side cross-sectional view of patch <NUM>. The patch is, for example, <NUM> thick, and this thickness is largely dependent on how thin the battery is. The battery in patch <NUM> is about <NUM> thick. The more efficiently the patch uses energy to create the electromagnetic fields, the less storage capacity the battery needs, and the thinner the battery can be, and the thinner and more flexible the patch can potentially be. For example, the patch is optionally only <NUM> thick, or <NUM>, or <NUM>, or <NUM>, or <NUM>, or less, and the battery is optionally less than <NUM> or less than <NUM> or less than <NUM> thick. Optionally, the battery is not recharged during the course of treatment by the electromagnetic fields, and optionally the battery is not even rechargeable, and in this case the battery needs enough storage capacity to power the patch for the entire period of treatment. For example, the battery has between <NUM> mA-hours and <NUM> mA-hours of storage capacity, with a voltage between <NUM> volts and <NUM> volts.

If the battery is rigid, then it is potentially advantageous if the battery is not too wide, for example no wider than <NUM>, especially in a direction where the patch may have to bend in order to conform to a surface of the patient's body. It is also potentially advantageous if the electronics package is not too wide, if it is rigid, for example not wider than <NUM>, and if there is at least <NUM> between the battery and the electronics package, if they are arranged along a direction that the patch has to bend. This can help to ensure that the patch is flexible enough to conform at least generally to a surface of the patient's body, adjacent to the body tissue that is being exposed to the electromagnetic fields, as well as to ensure that the patch is comfortable for the patient to wear.

In some embodiments of the invention, the electronics package is not rigid, but, for example, comprises flexible printed electronics parts, manufactured, for example, by thinned die thermocompression laminated onto liquid crystal polymer (LCP) films. In some embodiments of the invention, the battery may be flexible, for example a flexible polymer battery may be used. However, a polymer battery may not have enough storage capacity to last for the entire course of treatment without being recharged, and a polymer battery may not be rechargeable. In general, any type of battery that is sufficiently small and thin, and has sufficiently high storage capacity may be used, including alkaline, silver, lithium, nickel oxyhydroxide, and zinc air batteries.

There is a table listing battery types, with dimensions in mm and capacity in mA-hrs, available at www(dot)en(dot)m(dot)wikipedia(dot)org/wiki/List_of_battery_sizes>. Promising batteries are those with relatively low height, for example less than <NUM> or not much more than <NUM>, and relatively high capacity, for example more than <NUM> mA-hrs, or not too much less than that. For example, the CR2032 is <NUM> high and has a capacity of <NUM> mA-hrs, the CR2016 is <NUM> high and has a capacity of <NUM> mA-hrs, the CR2025 is <NUM> thick and has a capacity of <NUM> mA-hrs, the CR2320 is <NUM> thick and has a capacity of <NUM> mA-hrs, the CR2325 is <NUM> thick and has a capacity of <NUM> mA-hrs, and the CR2330 is <NUM> thick and has a capacity of <NUM> mA-hrs.

Renata SA of Itingen, Switzerland sells a flexible Li/MnO<NUM> battery called the CP042350, which might be suitable. It is only <NUM> thick, but has an area of <NUM> by <NUM>, and a storage capacity of only <NUM> mA-hrs. A few of them might have enough storage capacity, but might take up too much area. And if they were stacked, they might not be flexible enough.

In some embodiments of the invention, more than one battery may be used. It should be understood that whenever a battery is referred to herein, more than one battery may be used. Multiple batteries Imay be connected in series, to increase the voltage, and/or in parallel, to increase the current. In either case, using multiple batteries can increase the total battery storage capacity. A potential advantage of using multiple batteries is that the battery storage capacity may be increased, without having a large rigid volume, since the individual batteries can be spaced somewhat apart in the flexible substrate, to conform to the body surface of the patient.

Optionally, the electronic patch is water resistant. For example, it can withstand exposure to water for <NUM> hours without being damaged, or <NUM> exposures to water for <NUM> minutes each, which would allow the patient to take a shower twice a day during a treatment that is <NUM> days long. Optionally, the patch is completely water proof, and can withstand exposure to water for <NUM> days, <NUM> days, <NUM> days, <NUM> days, or <NUM> days, without being damaged.

<FIG> schematically shows electronic patch <NUM> in place on a surface of a patient's body, adjacent to a fracture <NUM> in a bone. Current in coil <NUM> produces an electromagnetic field <NUM> that extends into the patient's body, reaching fracture <NUM>. The furthest part of fracture <NUM> is about <NUM> beneath patch <NUM>, which is smaller than the radius of coil <NUM>, and the electromagnetic field reaches that far, without much attenuation compared to its value at the surface of the patient. It should be understood that the magnetic field lines shown in <FIG>, and in other drawings, are drawn schematically, roughly representing the shape of the field, but they are not based on accurate magnetic field calculations.

The peak current in coil <NUM>, and the peak current in other patches shown herein, is optionally between <NUM> and <NUM> mA, or between <NUM> and <NUM> mA, or between <NUM> and <NUM> mA, or between <NUM> and <NUM> mA, or between <NUM> and <NUM> mA, or between <NUM> and <NUM> mA, or between <NUM> mA and <NUM> A, or between <NUM> and <NUM> A, or less than <NUM> mA or more than <NUM> A. The peak magnetic field produced at the target site is optionally between <NUM> and <NUM> microtesla, or between <NUM> and <NUM> microtesla, or between <NUM> and <NUM> microtesla, or between <NUM> and <NUM> microtesla, or between <NUM> and <NUM> microtesla, or less than <NUM> microtesla or more than <NUM> microtesla.

<FIG> schematically shows an electronic patch <NUM> with two circular coils <NUM> and <NUM>, each imbedded in silicone, with a flexible strip of silicone <NUM> connecting them. Patch <NUM> is designed to wrap at least part way around a cylindrical body part, for example an arm, hand, leg, foot, pelvis, rib cage or neck, with coil <NUM> on one side of the body part, and coil <NUM> on another side of the body part, optionally on an opposite side from coil <NUM>, optionally facing coil <NUM>. When they are in this position, the two coils produce magnetic fields inside the cylindrical body part, between the coils, that are oriented in approximately the same direction, and add up, similar to the magnetic field produced by Helmholtz coils. <FIG> shows coils <NUM> and <NUM> in place on opposite sides of cylindrical body part <NUM>, producing a magnetic field <NUM> inside the body part.

Having two coils on different sides of the body part, producing the electromagnetic fields at the target site inside the body part, has the potential advantage that the fields are more uniform, and less current is required, and hence lower power in required, to produce the same field. For example, if the target site is a fractured bone site, and the fracture extends across the width of a bone, then a coil at one side of the bone can more efficiently produce fields on that side of the bone, and a coil at the other side of the bone can more efficiently produce fields on that side of the bone. So the fields are potentially produced more efficiently than they would be by only one coil, whichever side it is located on.

Optionally, coil <NUM> and coil <NUM> are connected together, for example in series or in parallel, such that a current going through one of the coils in a given direction will always result in current going through the other coil in the same direction when patch <NUM> is folded over with the two coils facing each other. Alternatively, coils <NUM> and <NUM> operate independently of each other, either with a single electronics package with a controller that independently controls the current in each coil, or with separate electronics packages for each coil, and optionally with a separate battery for each coil. But <FIG> shows the case where both coils are controlled by a same electronics package <NUM>, and powered by a same battery <NUM>. Even if the currents in the two coils are controlled independently, they normally operate with the current going in the same direction around the coil, when the two coils are facing each other.

In an embodiment of the invention shown below in <FIG>, with a configuration similar to that of patch <NUM> in <FIG>, in one mode of operation, only the first coil has current flowing in it, and the second coil is used to measure the emf induced by the first coil. A potential advantage of controlling the currents separately in the two coils is that it is possible to run the patch in the mode shown in <FIG>.

In some embodiments of the invention, the two coils may be oriented at different orientations, rather than facing each other. In some embodiments there are three or more coils, which may be oriented in various ways. A potential advantage of the configuration shown in <FIG>, is that the magnetic field contributed by both the coils adds up inside the body, so the field inside the body may be greater, for a given ohmic loss in the coils, than for other arrangements of coils.

A side cross-sectional view <NUM> of patch <NUM>, showing the coils, battery, and electronics package, is shown at the bottom of <FIG>.

An alternative design for a two-coil electronic patch <NUM> is shown in <FIG>. The patch is designed for use around the wrist, to treat fractures of the distal radius, and is shown partly wrapped around a wrist <NUM> of a patient. The patch is not wrapped completely around the wrist and joined together, which gives the wrist room to expand if it becomes swollen, and in addition it is made of a stretchable material, and can expand from a length of <NUM> to <NUM>. A top view <NUM> of the patch shows a circular coil <NUM> and a circular coil <NUM>, embedded in a flexible elastic substrate <NUM>. A CR2016 battery <NUM>, and an electronic package <NUM>, which includes a controller, are located between the two coils but closer to the edge of the patch, vertically displaced from the centers of the coils as seen in the drawing. Putting the battery and electronics package outside the coils has the potential advantage that they will not block a view of the fracture in an x-ray image, if an x-ray image is taken in order to examine the fracture while the patient is wearing the electronics patch. If an x-ray image is taken looking through the holes of the coils at the fracture site, i.e. in an anterior-posterior direction, then the image will not be blocked by the battery or the electronics package as long as they are not in the center of the hole. In addition, if the battery and electronics package are displaced vertically from the centers of the holes, then the view of the fracture site, which is right between the coils, will also not be blocked if the x-ray image is taken from a lateral direction, facing in a direction perpendicular to the cylindrical axis of the body part, but parallel to the plane of the coils. It should be understood that "vertical" and "horizontal" refer here to directions in the plane of the unwrapped patch, with the horizontal direction being the direction separating the two coils, and the direction along which the patch wraps around the body part. They have nothing to do with the orientation of the patch and the body part in space.

In some embodiments of the invention, the coils have relatively low opacity to x-rays, at wavelengths of interest for medical imaging, and/or they have a similar opacity to x-rays as the substrate has, so the coils do not interfere very much with x-ray images of the wrist.

Two side views <NUM> and <NUM> show the small thickness of the patch, only <NUM>.

<FIG> compares electronic patch <NUM>, shown in <FIG>, with two alternative designs. Top view <NUM> shows the same electronic patch as shown in <FIG>, and top views <NUM> and <NUM> show two other designs, with a different placement of battery <NUM> and electronics package <NUM>. In all three designs, the same coils <NUM> and <NUM> are used, with outer diameter of <NUM> and inner diameter of <NUM>. In view <NUM>, the battery and electronics package are between the two coils, but displaced vertically, closer to the edge of the patch. Putting the battery and electronics package closer to the edge of the patch, i.e. displaced vertically, may keep them from interfering with the visibility of a fracture in the bone, in an x-ray taken from any angle, lateral or anterior-posterior. In this design the patch is <NUM> wide (the vertical direction in <FIG>). In view <NUM>, the battery and the electronics package are each between one of the coils and the edge of the patch, well away from interfering with an x-ray image of the fracture. In this design, the patch is a little wider than in view <NUM>, <NUM>. In view <NUM>, the battery and the electronics package each overlap the coil that they are near. This patch is narrower than the other designs, only <NUM>, but thicker, <NUM> as opposed to <NUM> for the patches shown in views <NUM> and <NUM>, to accommodate the overlap.

Electronics package <NUM>, in electronic patch <NUM> in <FIG>, and the similar electronics package <NUM> in electronic patch <NUM> in <FIG>, and electronics package <NUM> in <FIG> and <FIG>, optionally includes a resonant energy saving circuit. The energy saving circuit includes a capacitor in series with the coil, and pulse generating circuitry, which repeatedly changes the voltage across the capacitor and coil, to produce pulses of current in the coil. The pulse generating circuitry may comprise a controller, for example a digital controller, that is programmed to make the changes in voltage at certain times, or the changes in voltage may be generated periodically by an analog circuit with some nonlinear elements. Initially, or at least after the pulse generating circuitry has been operating for several pulses and reaches a steady state, the capacitor is charged up to a certain voltage before a pulse is initiated. When the pulse is initiated, the electric energy of the capacitor is discharged into the magnetic field energy of the coil, and is then recycled back to the capacitor, where it remains until the next pulse is initiated. Ideally, almost all of the energy of the capacitor is available for producing the electromagnetic field of the coil, and almost all of the electromagnetic field energy of the coil is recycled back to the capacitor at the end of a pulse, with very little dissipation of energy. There are ohmic losses in the coil, but these will be relatively small, compared to the energy cycling between the coil and the capacitor, if the resistance R of the coil is much less than (L/C)<NUM>/<NUM>, where L is the inductance of the coil and C is the capacitance of the capacitor. For example, R is less than (L/C)<NUM>/<NUM> by at least a factor of <NUM>, or at least a factor of <NUM>, or at least a factor of <NUM>. Radiative losses from the coil will be negligible if the resonance frequency (LC)-<NUM>/<NUM> is small compared to the speed of light divided by the coil diameter, which is <NUM> for a coil <NUM> in diameter, while the resonance frequency is typically between <NUM> and <NUM>. There may also be some energy losses from eddy currents induced by the electromagnetic field in any conductors that the field comes in contact with, including the body of the patient. Any energy losses have to be supplied by the battery.

An example of a resonant energy-saving circuit is described in published US patent application <CIT>, and will be described here in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>. Further details of how this resonant energy-saving circuit may be implemented, and in particular how the pulse generating circuitry may be implemented, may be found in that publication.

<FIG>, schematically shows a circuit diagram for a portion <NUM> of such a resonant energy-saving circuit, including a coil <NUM> with inductance L, a capacitor <NUM> with capacitance C, a zero-voltage terminal <NUM>, and a terminal <NUM> with a voltage controlled by the pulse generating circuitry, not shown in <FIG>. The changes to the voltage <NUM> are shown schematically by terminal <NUM>, which has a positive operating voltage, for example equal to the battery voltage and terminal <NUM>, which has a negative operating voltage, for example equal to the battery voltage in magnitude. Initially, at least once several pulses have been initiated and the circuit has reached a steady state, terminal <NUM> is set to the positive operating voltage of terminal <NUM>, as shown in box <NUM> of flowchart <NUM> in <FIG>, and capacitor <NUM> has a positive voltage equal to the operating voltage, and there is zero voltage across coil <NUM>, and no current flowing in the coil. To initiate a pulse, terminal <NUM> is set to the negative operating voltage of terminal <NUM>, at box <NUM> of flowchart <NUM>. At first, capacitor <NUM> remains charged at the same positive operating voltage that it had before, and coil <NUM> now has a voltage across it equal to nearly twice the operating voltage, if the positive and negative operating voltages are equal in magnitude. Current starts to flow in the coil, at box <NUM> of flowchart <NUM>, slowly at first, because the back emf of the coil nearly cancels out the voltage across it. In <FIG>, which schematically shows the current <NUM> in the coil as a function of time, shown on axis <NUM>, and the voltage <NUM> across the capacitor as a function of time, the pulse is initiated at time <NUM>. As the current in the coil starts to build up, the capacitor starts to discharge. At time <NUM>, as stated in box <NUM> of flowchart <NUM>, the capacitor has completely discharged, and almost all of its energy has gone into the electromagnetic field energy of the coil, which reaches a maximum current. The current, continuing in the same direction, starts to charge up the capacitor with the opposite polarity, as stated in box <NUM> of flowchart <NUM>. At time <NUM>, the capacitor has charged up to the operating voltage, but with polarity opposite to what it was at time <NUM>, and the current and voltage across the coil has fallen to zero, as stated in box <NUM> of flowchart <NUM>. The interval from time <NUM> to time <NUM> is one half of a wave period at the resonant frequency (LC)-<NUM>/<NUM> to first approximation, ignoring the effects of ohmic losses and any other dissipation. Again ignoring dissipation, the current as a function of time between times <NUM> and <NUM> is nearly a sine function, at the resonant frequency. The voltage across the capacitor as a function of time between times <NUM> and <NUM> is also nearly a sine function, but <NUM> degrees out of phase with the current as a function of time.

At time <NUM>, if terminal <NUM> remains at the negative operating voltage of terminal <NUM>, or if terminal <NUM> is floated, indicated by "State <NUM>" in <FIG>, then no more current will flow in coil <NUM>, and capacitor <NUM> will remain fully charged at the negative operating voltage, as stated in box <NUM> of flowchart <NUM>. This state, between pulses, will persist until terminal <NUM> is switched back to having the positive voltage of terminal <NUM>, shown in box <NUM> of flowchart <NUM> which is done at time <NUM> in <FIG>. The capacitor will start to discharge again, and the current builds up again in the coil, as stated in box <NUM> of flowchart <NUM>, but this time the current will be in the opposite direction from what it was between time <NUM> and time <NUM>. The current after time <NUM> will have the same magnitude as a function of time, though opposite in sign, as it had between times <NUM> and <NUM>, as the capacitor discharges, building up the electromagnetic field of the coil, and then charges up again with its original positive polarity, recovering field energy from the coil, as stated in boxes <NUM> and <NUM> of flowchart <NUM>. At time <NUM>, as stated in box <NUM> of flowchart <NUM>, half of a resonant frequency wave period after time <NUM>, the capacitor will again be charged to the operating voltage, with its original positive polarity, and the coil current and voltage will again be zero. The circuit has now returned to its state before time <NUM>, and can remain in this between-pulse state until a new current pulse is initiated by changing the voltage of terminal <NUM>. Optionally, terminal <NUM> is floated until the next pulse is initiated.

The resonance frequency (LC)<NUM>/<NUM>, which is related to the pulse time as explained above, is optionally between <NUM> and <NUM>. Alternatively it is between <NUM> and <NUM>, or between <NUM> and <NUM>, or between <NUM> and <NUM>, or between <NUM> and <NUM>, or between <NUM> and <NUM>, or more than <NUM>.

<FIG> is an exemplary circuit diagram for the energy saving circuit, showing how the principles of the circuit in <FIG> may be implemented. The switching of the voltage across the capacitor and coil in series between the positive and negative operating voltage is accomplished by switches based on FETs, which are opened and closed by applying an appropriate voltage to them. A microprocessor generates the signals, positive or negative square wave pulses, that control the state of the FETs. Those signals are shown in <FIG>, which also shows the current in the coil as a function of time. In <FIG>, a pulse with positive current is always followed immediately by a pulse with negative current, so the capacitor always has the same sign of operating voltage, for example positive operating voltage, during the intervals between pulses. These back-to-back pulses together last for a whole cycle of the LC resonant frequency.

<FIG> schematically shows an electronic patch <NUM> with two coils, in which one of the coils can be used as a sensor by measuring the emf induced in it by the other coil. Coil <NUM> is on top, and coil <NUM> is on the bottom, of a cylindrical body part <NUM>, containing a bone <NUM>. A controller <NUM> generates current pulses through coil <NUM>, that create an electromagnetic field for treating a fracture site <NUM> in bone <NUM>.

Controller <NUM> is optionally part of an electronics package incorporated in patch <NUM>, similar to electronic package <NUM> in <FIG>, or electronics package <NUM> in <FIG>, and controller <NUM> and patch <NUM> are optionally powered by a battery, similar to battery <NUM> in <FIG>, or battery <NUM> in <FIG>. Alternatively, controller <NUM>, and/or a power supply that powers it and/or patch <NUM>, are not part of patch <NUM> at all, but may be larger units external to patch <NUM>.

Some of the magnetic flux lines <NUM>, generated by coil <NUM>, also pass through coil <NUM>. At the time shown, at least, coil <NUM> does not have any current passing through it, and does not generate its own electromagnetic field at the fracture site. But by measuring the emf voltage generated by the changing magnetic flux going through coil <NUM>, controller <NUM> can obtain information that can be useful for calibrating and adjusting the field generated by patch <NUM>.

<FIG> shows a flowchart <NUM> illustrating an exemplary manner in which patch <NUM> operates. At <NUM>, the patch is calibrated. This is done by measuring the emf in coil <NUM>, when a known current, with known pulse shape and width, is passed through coil <NUM>, with coil <NUM> at a known position and orientation with respect to coil <NUM>. For example, coils <NUM> and <NUM> are held with their axes aligned, separated by a known distance. For example, the known distance is a standard distance that the coils would be separated, for a cylindrical body part, optionally a specific body part that the patch is designed to treat, such as a forearm at the wrist, of a standard size. Optionally, the current passed through coil <NUM> is the current needed in order to produce a specified electromagnetic field strength, for example a field strength that is believed to work well for therapy, with that pulse shape and width, at a standard target location in the body part. Once patch <NUM> has been calibrated, it is possible to calculate what current should be passed through coil <NUM>, for that pulse shape and width, in order to produce the specified electromagnetic field strength at a given location relative to coil <NUM>. At <NUM>, patch <NUM> is placed around a cylindrical body part, such as body part <NUM>. At <NUM>, a known current, of known pulse shape, optionally the same current and pulse shape used in calibrating patch <NUM>, is passed though coil <NUM>, and at <NUM>, the emf in coil <NUM>, induced by the current in coil <NUM>, is measured. By comparing the measured emf, to the measured emf found during the calibration, at <NUM>, it is possible to estimate what electromagnetic field strength would be produced at the target location by that current in coil <NUM>, and to estimate how the current in coil <NUM> should be changed to produce the specified therapeutic electromagnetic field strength at the target location. At <NUM>, the current in coil <NUM> is changed to that estimated value, and therapy is performed using the adjusted value of the current.

Optionally, patch <NUM> also has a mode of operation where coil <NUM> generates its own therapeutic electromagnetic fields at the target location in body part <NUM>, that add to the fields generated by coil <NUM>. In this case, coil <NUM> also has current going through it, when treatment is performed, and the current going through coil <NUM> is taken into account, in calculating the current that should be passed through coil <NUM>, in order to obtain the specified electromagnetic field strength at the target location. Optionally, the emf measured in coil <NUM> is also used to adjust the current going through coil <NUM>, in order to produce a specified therapeutic electromagnetic field strength at the target location.

When patch <NUM> has a mode of operation where coils <NUM> and <NUM> are both used to generate fields at the target location in the body part, it optionally stays in this mode of operation most of the time, while treatment is continuing. But occasionally, or at regular intervals, patch <NUM> may go into the mode of operation where coil <NUM> is used to measure the emf induced by coil <NUM>, at least for a short time. This may be done, for example, if medical personnel request a reading on emf in coil <NUM>, for example using a communications link with controller <NUM>. Alternatively or additionally, controller <NUM> may be programmed to switch patch <NUM> to the mode where emf is measured in coil <NUM>, for a short time, for example for <NUM> second, at regular intervals, for example once an hour, or once a day. Optionally, the regular measurements of emf in coil <NUM> are used in a closed feedback loop to keep the electromagnetic field strength at the target location at a specified value.

Optionally, the emf measured in coil <NUM> is used to calculate the distance between coil <NUM> and coil <NUM>, when patch <NUM> is in place around body part <NUM>, and that distance is used to estimate the distance from coils <NUM> and <NUM> to the target location, and then to estimate how much current is needed in coils <NUM> and <NUM> to produce the specified electromagnetic field strength at the target location, for example using magnetic simulation software. Alternatively, the distance from coil <NUM> to coil <NUM>, and the distance to the target location, is never calculated explicitly, but the measured emf of coil <NUM> when patch <NUM> is in place around body part <NUM> is compared to the measured value of emf when patch <NUM> was calibrated, for example a ratio and/or difference in the emf values is found, and that ratio and/or difference is used directly to calculate the current that should be used in coils <NUM> and <NUM> to obtain the specified electromagnetic field strength at the target location.

The measured emf of coil <NUM>, and/or the distance between coil <NUM> and coil <NUM> that can be calculated from it, may also be used in other ways, to obtain information about the state of body part <NUM>. For example, the emf of coil <NUM>, induced by coil <NUM>, is regularly measured during the course of treatment of body part <NUM>. If the distance appears to be increasing over time, because the measured emf in coil <NUM> is decreasing over time, for the same current in coil <NUM>, then that might indicate that body part <NUM> is undergoing swelling. Optionally, the measurements of emf of coil <NUM> are communicated to medical personnel, using a communications channel, for example a wireless communications channel, in controller <NUM>. Based on the degree and rate of swelling inferred from the emf measurements, the medical personnel might decide that some medical intervention is appropriate, to reduce the swelling. Alternatively, the medical personnel might decide, on the basis of the emf measurements, that the swelling is of a degree expected for that kind of bone fracture, and that no intervention is necessary.

If the distance between coil <NUM> and <NUM> is inferred to be decreasing over time, from an increase in the induced emf in coil <NUM> for a given current in coil <NUM>, then that might indicate that body part <NUM> is shrinking, perhaps due to a reduction in swelling as the bone fracture heals, or due to wasting of muscle. Whatever the cause of the shrinkage of body part <NUM>, it might indicate that the cast is becoming too loose, and can no longer keep bone <NUM> in place while the fracture is healing. In that case, it might be medically advisable to remove the cast and to replace it. On the other hand, if body part <NUM> is shrinking, but more slowly than expected, that might indicate that bone <NUM> is failing to heal properly.

<FIG> schematically shows a cast <NUM> covering an electronic patch <NUM>, in contact with body part <NUM>, within which there is a fracture site <NUM> that is being treated by electromagnetic fields generated by electronic patch <NUM>. Electronic patch <NUM> includes a coil <NUM>, a battery <NUM>, and an electronics package <NUM>. Optionally, there is also a second coil, as described for example for the patch shown in <FIG> or <FIG>. Optionally, electronic patch <NUM> includes sensors that can obtain data directly from the skin of the body part, under the cast. For example, sensor <NUM> is a pressure sensor, and sensor <NUM> is a blood oxygen sensor. The sensors are optionally part of electronics package <NUM>, or at least are connected to the electronics package for power and data processing. Optionally, one or more of the sensors causes a warning light <NUM>, located outside the cast, to light up under certain conditions, such as low blood oxygen level which can indicate that the cast is too tight. Both the pressure sensor and the blood oxygen sensor can be used to detect if the pressure under the cast is rising, for example due to swelling of body part <NUM>, or if the pressure is too high because the cast was placed too tightly to begin with, which can interfere with blood circulation, causing a drop in blood oxygen levels in the skin under the cast. The pressure sensor can also detect when the pressure under the cast is falling, which might mean that swelling of the body part is decreasing, or muscle mass is being lost. If the pressure decreases too much, the cast might be too loose to effectively hold the fractured bone in place, and it might be medically advisable to remove the cast and replace it with a cast that fits better.

Communications link <NUM>, optionally a wireless communications link, is optionally used to transmit the sensor data, and other data generated by patch <NUM>, to medical personnel, including data on the emf induced in a second coil, as described above in <FIG> and <FIG>. Communications link <NUM> is optionally one-way, for example communicating data from patch <NUM> to medical personnel. Alternatively, communications link <NUM> is two-way, and is used by medical personnel to control the operation of patch <NUM> when it is under cast <NUM>, and is not easily accessible. For example, medical personnel could use communications link <NUM> to request patch <NUM> to obtain certain data, or to turn patch <NUM> on or off, or to change parameters of its operation, such as the pulse repetition rate or the field amplitude. Alternatively, communications link is one-way, but is used only to control patch <NUM> from the outside, not to obtain data from it.

Optionally patch <NUM> has an on/off switch <NUM>. Optionally, switch <NUM> is used only before patch <NUM> is covered by cast <NUM>, and cannot be accessed once patch <NUM> has been covered. Alternatively, switch <NUM> can be used when patch <NUM> is covered by cast <NUM>. Possible designs for switch <NUM> include:.

Optionally switches operating by any of these methods, or any other method, can also be used to initiate a test to see if the patch is operating properly, and can be used to change settings such as power levels.

Optionally, if the battery is rechargeable, it can be recharged using coil <NUM>, or another coil not shown in <FIG>, by using an external coil to transfer power to coil <NUM> inductively, even if coil <NUM> is below the cast.

<FIG> and <FIG> show block diagrams for circuitry that allows the coil to receive an external command to activate the patch when it is de-activated. In <FIG>, the coil, labeled "Field transmission coil" functions as a radio receiver coil, receiving a signal from an external activator, to activate the patch. The coil passes the signal to an Incoming RF Command Detector, which interprets the signal, and tells the Master ON/OFF control to activate the energy saving circuit that generates the pulses. There is also a "Switch Control timer ON/OFF timing" module shown in <FIG>, which connects or disconnects the energy saving circuit and the battery, using the High Speed Switch, according to the on and off times set in the timer. <FIG> provides more details of how the block diagram of <FIG> is implemented in a system designed by the inventors. The Rx buffer module in <FIG>, similar to the Incoming RF Command Detector in <FIG>, interprets RF signals transmitted by an external activator and received by the field transmission coil, and sends the ON/OFF commands to a Micro-controller. The Micro-controller, which is always connected to the battery in order to receive the ON/OFF commands, connects or disconnects the battery from the Tx Driver, the circuitry, shown schematically in <FIG> and in more detail in <FIG>, that generates the pulses of current. The Tx Driver is shown connected to the resonance capacitor and the field transmission coil in series, as shown in <FIG>. Optionally, the field transmission coil is still capable of receiving commands from the activator, even when the coil is generating current pulses, because the RF signals are at a much higher frequency than the current pulses, and can be separated from the current pulses by an appropriate filter.

<FIG> shows a flowchart <NUM>, for events that occur during the time an electronic patch, such as those described herein, is used to promote tissue healing at a target site, such as a fractured bone site, using pulsed electromagnetic fields. Flowchart <NUM> is primarily concerned with an electronic patch that is located under a cast, but is not limited to that case.

At <NUM>, the patch is turned on. At <NUM>, the patch is placed on a body part adjacent to the target site. At <NUM> the body part, optionally including the patch, is optionally covered with a cast. At <NUM>, during the course of treatment, the patch is periodically turned off and on. For example, the patch is optionally turned on for only a limited number of hours each day. Turning the patch off and on is optionally done automatically with some kind of timer, possibly a timer function in the electronics package, such as the "Switch Control Timer" module shown in <FIG>. Alternatively, it is done manually, for example using a switch that is accessible outside the cast, if there is a cast covering the patch. For example, an external activator is optionally used to turn on the patch when it is "sleeping" by sending a radio signal that is received by the coil, interpreted by the Incoming RF Command Decoder module shown in <FIG>, and sent to the Master ON/OFF control module. Of course, the Switch Control Timer module, the Master ON/OFF control module, and the RF Command Decoder module are all optionally powered on, connected to the battery, even when the patch is deactivated, so that these modules can operate as described, to turn the patch on.

At <NUM> medical images are optionally made of the body part, to monitor the tissue healing, for example x-ray images. At <NUM>, pressure and/or swelling of the body part is optionally monitored, using a sensor under the cast, or using a second coil to measure emf voltage induced by a first coil. At <NUM>, if the pressure and/or swelling is found to be too high or too low, some kind of intervention is optionally taken. At <NUM>, the cast and the patch are removed at the end of treatment, for example when the tissue is healed.

Table <NUM> shows exemplary coil parameters that the inventors believe will be useful for several different types of bones.

Different power settings are optionally used for different individuals who have different amounts of subcutaneous fat in their bodies, which can affect the distance from the coil to the target site in the bone, and hence the power needed to produce electromagnetic fields of a specified intensity at the target site. For example, there may be different power settings for thin men, overweight men, thin women, and overweight women. The goal may be to produce a magnetic field of between <NUM> and <NUM>µT at the target site, for example <NUM>µT.

As used herein the term "about" refers to ±<NUM>%.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find calculated support in the following examples.

Patch <NUM> in <FIG> comprises a continuous coil <NUM>, which may be a multi-turn coil or coils, for focusing the generated electromagnetic field onto a fractured bone site. Coil <NUM> is shown in <FIG> as a circular configuration where the radial spacing between each pair of adjacent turns is uniform, but it may also be of any other symmetric configuration, such as rectangular, or any asymmetric configuration, and the radial spacing between each pair of adjacent turns may be different. When patch <NUM> is positioned on top of a flat surface, all turns of coil <NUM> are coplanar, and each turn is concentric with an adjacent turn.

A controller, part of electronics package <NUM>, powered by battery <NUM> is connected to the conductor of coil <NUM> in order to control the properties of the generated electromagnetic field that propagates from the coil to the fractured bone site. The controller comprises a current modulator and a power saving circuit for regulating the current needed to generate the electromagnetic field, but may also comprise other electronic components selected from, but not limited to, a timer, microswitch, oscillator, wireless transceiver, and inverter.

Although the only two illustrated components that are shown to be positioned radially inwardly relative to coil <NUM> are electronics package <NUM> and battery <NUM>, it will be appreciated that any other electronic component may be positioned externally to electronics package <NUM> insofar as it retains the compactness of patch <NUM> by being positioned radially inwardly relative to coil <NUM>.

As described above, patch <NUM> may be imparted with sufficient flexibility to facilitate application thereof around the circumference of an injured limb. To achieve the required degree of flexibility, the electronic components may be manufactured by low-cost printed electronics techniques and embedded within, or otherwise integrated with, one or more flexible substrates <NUM> to produce a monolithic patch. Each flexible substrate <NUM> may be a silicone substrate, a polyimide substrate, a liquid crystal polymer (LCP) substrate, a multi-layer film laminate substrate, a foil substrate, or a combination thereof. Flexible electronic components may be fabricated by thinned die thermocompression laminated into LCP films such that the films completely encapsulate the die.

Alternatively, the printed electronics techniques may include a rigid PCB and battery with an appropriate spacing between them to provide some level of flexibility.

The bottom surface <NUM> of the flexible substrate <NUM> may be provided with application means, such as adhesive elements for adhesion to a skin surface or clips for engagement with a beard or other hair covered skin surface.

In order to minimize battery consumption, the oscillator is adapted to generate a plurality of current pulses, e.g. rectangular pulses, for exciting the coil by a desired frequency and magnitude, so as to induce a desired magnetic flux. Of course, other waveforms, such as a triangular, sawtooth, and sinusoidal waveform, may also be used to excite the coil. The timer modulates the waveform by periodically deactivating the power supply from the battery to the oscillator in order to achieve a desired duty cycle which is potentially useful for saving energy. An inverter in electrical communication with the oscillator may be employed in order to periodically change the direction of the magnetic field lines and to thereby additionally improving the rate of osteogenesis.

Also, the controller may operate in a sleep mode whereby the electronic components are inactive when the electronic patch is in storage. The controller becomes activated in response to a predetermined pressure sensed by the microswitch through the flexible substrate upon external application of the electronic patch to the injured limb. Alternatively, the controller may become activated by a wireless command transmitted to the transceiver, a pull trigger, a magnetic trigger or by applying an external electric induction.

As additional means to minimize battery consumption, the controller in conjunction with the timer may be operable to reduce the magnitude of the excitation current after a predetermined interval, e.g. a week, following activation of the controller. During this interval, the generated electromagnetic field stimulated osteogenesis at the fractured bone site to such a significant degree that the osteogenesis will continue even after the magnitude of the excitation current is reduced.

In addition to a battery, the electronic components may be powered by any other power source well known to those skilled in the art, including a piezoelectric device for generating piezoelectricity, a capacitor which is charged by a radiofrequency device located at the home of a patient and therefore would not require outpatient services, a dynamo, and an electro-kinetic actuator, for example one which employs a magnetic element that is displaceable along a coil.

<FIG> is a schematic cross sectional view of injured limb <NUM> to which electronic patch <NUM> is externally applied, illustrating the ability of the coil to focus the generated electromagnetic field onto fractured bone site <NUM>. During operation of the current modulator, current flows through diametrically opposite coil portions 5A and 5B, and electromagnetic fields 17A and 17B, respectively, propagate at a right angle to a corresponding conductor of a coil portion. The magnitude of the magnetic flux is greatest at skin surface <NUM> and is reduced as a function of the distance from the conductor. At a predetermined depth below skin surface <NUM> coinciding with the location of fractured bone site <NUM>, e.g. <NUM>, electromagnetic fields 17A and 17B become superposed one with the other. Even though the magnitude of the magnetic flux has become reduced at fractured bone site <NUM>, it is additive with respect to the electromagnetic field propagating from the diametrically opposite coil portion. Similarly, other electromagnetic fields propagating from other corresponding coil portions become superposed one with the other at fractured bone site <NUM>. Fractured bone site <NUM> accordingly becomes impinged by an electromagnetic field having a surprisingly high magnitude of magnetic flux that accelerates stimulation of osteogenesis.

Aspects, embodiments and examples which do not fall under the scope of the claims do not form part of the invention and are merely provided for illustrative purposes.

Claim 1:
An electronic patch (<NUM>) for stimulating tissue healing at a target site (<NUM>) inside a cylindrical body part (<NUM>), suitably sized to wrap at least partly around the body part, with a first part of the patch on one side of the body part, and a second part of the patch on another side of the body part, the patch comprising:
a) a battery or an arrangement of multiple batteries (<NUM>);
b) a first coil (<NUM> or <NUM>) located in the first part of the patch, and a second coil (<NUM> or <NUM>) in the second part of the patch; and
c) a controller (<NUM> or <NUM>), powered by the battery or batteries;
characterized in that the controller is configured in a first mode of operation to pass a known current with known pulse shape and width through the first coil (<NUM>), producing an electromagnetic field at the target site, and to measure an emf voltage induced in the second coil (<NUM>) by the current passing through the first coil.