WO1998051371A1

WO1998051371A1 - Bone repair enhancer

Info

Publication number: WO1998051371A1
Application number: PCT/US1998/010141
Authority: WO
Inventors: Serjan D. Nikolic
Original assignee: Nikolic Serjan D
Priority date: 1997-05-13
Filing date: 1998-05-13
Publication date: 1998-11-19
Also published as: AU7495898A

Abstract

The invention relates to a bone repair enhancer including first and second RF electrodes. A substrate couples the first RF electrode to the second RF electrodes and has a thickness that permits placement of the substrate between a skin layer and a bone structure. An RF energy source provides RF energy to at least one RF electrode over a cable. In another embodiment the enhancer includes at least one RF electrode with a length sufficient to enhance repair along at least a portion of the elongated lesion. A sensor is coupled to the at least one RF electrode. The sensor provides a signal to a feedback control device coupled to an RF energy source configured to provide RF energy to the at least one RF electrode. The level of RF energy delivered from the RF energy source to the electrode is adjusted in response to the signal from the at least one sensor.

Description

BONE REPAIR ENHANCER

FIELD OF THE INVENTION This invention relates to a device for enhancing the repair of damage to bone structures and more particularly for enhancing the repair of elongated lesions coupled to bone structures.

BACKGROUND OF THE INVENTION

Lesions to human bone structures are known to be unusually painful and have extended recovery times. Many of the most painful lesions are known to have an elongated shape on or within the bone. These elongated lesions can occur as a result of elective surgery or sudden trauma. A sternotomy provides an example of an painful elongated lesion which results from elective surgery. A sternotomy is required for most open heart surgeries and involves sawing the sternum in half so that the heart and lungs are exposed. After completion of the surgery, the chest cavity is closed by wiring the sternum back together with a series of heavy wire sutures. Once the sternum is closed a crack runs the length of the sternum.

Recovery from sternotomies is known to be very painful. Soon after the sternum is closed patients must begin inflating their lungs to overcome the depressive effects of the anesthesia and bed rest. The pain from the expansion of the chest is so substantial that patients are often given pillows to support their chest. In order to overcome the reluctance to breathe deeply, patients are often required to attend respiratory therapy. Respiratory therapy ensures that the patient's lungs are reaching full inflation and that the patient is able to cough.

The pain from a sternotomy can be minimized by enhancing the healing process. It is known that bones demonstrate an increased rate of healing when a electromagnetic field is produced in proximity to a lesion. Researchers have developed bone growth stimulators to take advantage of the increased healing, however, the elongated nature of many lesions presents design challenges for these stimulators.

The bone growth stimulators which have been developed generally fall into two groups. One known group of bone growth stimulators is implantable and passes a DC current across the bone fracture. The generator of such stimulators is implanted in the body near the site of a bone fracture. A cathode typically exits the case of the DC stimulator leading directly to the bone injury site. The stimulator case acts as the anode. Electronics within the stimulator cause a direct current to flow between the cathode and anode and thereby through the fracture.

There are numerous disadvantages associated with applying DC current bone growth stimulators to an elongated lesion. The DC characteristics of these stimulators generally require that the cathode be directly wired to or embedded in the bone on one side of the fracture. The cathodes are embedded to force the current to flow through the bone fracture site instead of through the fluid surrounding the bone fracture site. In an elongated lesion numerous cathodes would need to be attached along the length of the lesion in order to stimulate healing along the entire lesion. The numerous cathodes would add to patient discomfort and would increase the chance for infection. Further, the current will concentrate near the electrodes rather than being distributed along the length of the lesion. As a result, these electrodes may need to be adjusted after their initial placement to encourage a more uniform distribution of energy along the length of the lesion or to prevent cell necrosis resulting from an excessive amount of current concentration in one area of the sternum. Another category of bone growth stimulators are external applied or non-invasive stimulators. These devices are placed outside the body and typically produce a Bassett type signal across the fracture. A Bassett signal is the result of studies conducted by C. A. L. Bassett. The studies found that bones under stress emit an electrical signal which is thought to naturally stimulate bone growth. External stimulators generally simulate these Bassett type signals „ within the bone fracture site.

External bone growth stimulators are not appropriate for application to all areas of the body because they do not concentrate the energy at the lesion but pass a current across an entire body part. For instance, in the case of a sternum external stimulators would pass a current through the sternum but also through the heart, lungs and spine. The current may interact with any of these organs as well as other implements present in the patients chest. For instance, the current may interact with wires used to close a sternotomy or with stents used in angioplasty. As a result, external stimulators may disrupt structures which are adjacent to an elongated lesion.

For the above reasons, there is a need for a device which can enhance the repair of elongated lesions. The device should focus energy on the lesion without disrupting adjacent structures and enhance repair continuously along the length of at least a portion of the lesion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and apparatus for enhancing repair of an elongated lesion coupled to a bone structure.

Another object of the present invention is to provide a method and apparatus configured to deliver sufficient energy to an elongated lesion to enhance repair along the lesion.

Yet a further object of the present invention is to provide a method and apparatus for enhancing bone repair at an elongated lesion by focussing energy on the lesion without disrupting adjacent structures. Still a further object of the present invention is to provide a method and apparatus for enhancing bone repair along the length of an elongated lesion by focussing energy along the length of the elongated lesion.

Still a further object of the present invention is to provide a method and apparatus for enhancing bone repair along the length of an elongated lesion by focussing RF energy continuously along the length of at least a portion of the elongated lesion.

Still another object of the present invention is to provide a method and apparatus configured to deliver sufficient energy to an elongated lesion coupled to a bone structure to raise the temperature of the bone structure adjacent to an elongated lesion.

Yet another object of the present invention is to provide a method and apparatus with a feedback control device configured to raise the temperature of a bone structure adjacent to an elongated lesion to a particular level and maintain the temperature of the bone structure at that level.

These and other objects of the invention are obtained with a bone repair enhancer. The bone repair enhancer includes first and second RF electrodes. A substrate couples the first RF electrode to the second RF electrodes and has a thickness that permits placement of the substrate between a skin layer and a bone structure. An RF energy source provides RF energy to at least one RF electrode over a cable.

In another embodiment the enhancer includes at least one RF electrode with a length sufficient to enhance repair along at least a portion of the elongated lesion. A sensor is coupled to the at least one RF electrode. The sensor provides a signal to a feedback control device coupled to an RF energy source configured to provide RF energy to the at least one RF electrode. The level of RF energy delivered from the RF energy source to the electrode is adjusted in response to the signal from the at least one sensor.

At least one electrode is positioned between the patient's skin and the bone structure. The electrode is positioned sufficiently close to a lesion on the bone structure such that at least a portion of the elongated lesion receives energy continuously along its length. The portion of the elongated lesion which receives energy continuously along its length is referred to as a treatment site. The transfer of energy continuously along the treatment site causes the temperature within the treatment site to rise thereby enhancing bone repair along „ the length of the treatment site.

The geometry of the electrode maximizes the degree of enhanced healing. The electrode can have an elongated geometry which allows energy to be transferred continuously along the length of the treatment site. Since energy is transferred continuously along the length of the treatment site, healing is enhanced at each point within the treatment site.

The enhancer can operate in a monopolar mode. Each electrode is positioned adjacent to the elongated lesion and is operated as an RF emitter. A ground pad is positioned external to the patient on the opposite side of the bone structure from the electrode. The emitted energy can be focussed on the elongated lesion by including an RF insulator at the proximal side of the electrode.

The enhancer can include a second electrode and operate in a bipolar mode. The electrode acts as an emitter and the second electrode acts as a ground electrode. The electrode and second electrode are positioned adjacent to one another on opposite sides of the elongated lesion. To focus the energy on the elongated lesion an RF insulator can be positioned on the proximal side of each electrode. In one embodiment, the sensor is a temperature sensor which provides a signal representing the temperature of the bone structure adjacent to the elongated lesion. As a result, the feedback control system adjusts the energy supplied to the bone structure in response to the temperature at the bone structure. For instance, if the sensor is adjacent to the elongated lesion the feedback control system can raise the temperature of the elongated lesion to a desired temperature and maintains the elongated lesion at that desired temperature.

The substrate and one or more electrodes have a non-tissue piercing periphery to prevent further damage to the patient's skin or bone structure. The sensor can be positioned on the electrodes or on the substrate. After healing of the bone structure, the enhancer can be surgically removed. In another embodiment, the electrode and substrate have a biocompatible surfaces so that after healing is complete, the cable is removed while the electrode remains in place within the body. The electrode can also be constructed from bioabsorbable materials which can be absorbed by the body after a period of time.

Another embodiment provides a method for enhancing the repair of an elongated lesion coupled to a bone structure. The method specifies providing a bone growth enhancer including at least one energy transfer surface of sufficient length to enhance bone repair along at least a portion of the length of the elongated lesion. The energy transfer surface is positioned sufficiently close to the elongated lesion such that energy directed from the energy transfer surface reaches the elongated lesion. Sufficient energy is delivered to the elongated lesion to enhance repair of the elongated lesion while minimizing disruption of adj acent structures .

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 A is a side view of a bone repair enhancer for use on a elongated lesion coupled to a bone structure.

Figure IB illustrates a sternum which has been closed with sutures after a sternotomy.

Figure 1C is a side view of the enhancer of Figure 1A in position on the sternum illustrated in Figure IB.

Figure 2 A illustrates an electrode positioned adjacent to at least a portion of the length of an elongated lesion. Figure 2B illustrates a single strand electrode woven back and forth over an elongated lesion.

Figure 2C illustrates an electrode which is a flexible mesh.

Figure 3 is a side view of an enhancer which focusses energy on an elongated lesion by operating in a bipolar mode. Figure 4 is a side view of an enhancer which concentrates energy on an elongated lesion by placing an insulator on the proximal side of an electrode.

Figure 5 illustrates an enhancer with a first electrode positioned on the opposite of an elongated lesion from a second electrode. Figure 6 A is a side view of the distal side of the electrodes coupled by a substrate which extends along the length of the electrodes.

Figure 6B is a side view of the proximal side of electrodes coupled by a substrate which extends along the length of the electrodes.

Figure 6C is a cross sectional view of the electrodes illustrated in Figure 6A.

Figure 6D is a side view of the distal side of the electrodes coupled together by a substrate which extends along the length of segments of the electrodes.

Figure 7 is a cross section view of the energy distribution which results from placing an insulator on the proximal side of two electrodes operating in a bipolar mode.

Figure 8 is a side view of an enhancer with a first electrode positioned at an anterior of a bone structure and a second electrode positioned at an anterior of a bone structure. Figure 9 is a cross section of an elongated lesion which is a crack in a bone structure with an electrode positioned in the crack.

Figure 10A is a cross section of a decoupler coupling an electrode to a cable.

Figure 1 OB is a cross section of the decoupler of Figure 10A decoupled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1A illustrates one embodiment of a bone repair enhancer 10. The enhancer 10 includes an RF electrode 12 including an energy transfer surface 14 with a distal side 16 and a proximal side 18. An RF energy source 20 supplies RF energy to the electrode 12 over a cable 22. A sensor 24 is coupled to the electrode 12 and provides a signal to a feedback control device 26. During operation of the enhancer 10, RF energy is delivered fro ihe RF energy source 20 to the electrode 12. The feedback control device 26 continuously monitors the signal from the sensor 24 and adjusts the level of RF energy delivered from the RF energy source 20 in response to the level of the signal.

The electrode 12 is configured to be positioned adjacent to an elongated lesion which is coupled to a bone structure. One example of an elongated lesion 28 coupled to a bone structure 30 is a crack 32 along the length of a sternum 34 as illustrated in Figure IB. This type of elongated lesion 28 often results from a sternotomy which requires that the sternum 34 be sawed in half along its length.

The crack 32 results when the sternum 34 is closed with a plurality of heavy wire sutures 35.

Figure 1C illustrates the electrode 12 positioned between the a bone structure and a skin 36 of the patient 38. The distal side 16 of the electrode 12 is adjacent to the sternum 34 while the proximal side 18 of the electrode 12 is adjacent to the skin 36. The cable 22 extends percutaneously through a puncture 40 in the patient's skin 36.

The electrode can be as thick as few millimeters, as long as the electrode 12 can be comfortably positioned between the bone structure 30 and the skin 36 without causing further discomfort to the patient 38. The electrode 12 has a non-tissue piercing periphery 42 to prevent further damage to the bone structure 30.

The electrode 12 can at least partially conform to the contours of the bone structure 30. For instance, the electrode 12 can be sufficiently flexible that it substantially conforms to the general contours of the bone structure 30. The single strand electrode 12 illustrated in Figure 2B is an example of an electrode 12 with sufficient flexibility to take on the contour of the bone structure 30. Similarly, a mesh electrode (Figure 2C) would conform to the contours of the sternum. The electrode 12 can also be rigid and pre-formed to the contour of the bone structure 30. Figure 1 A illustrates an example of a pre-formed electrode 12 intended for use with a sternum.

The electrode 12 has sufficient length to allow the electrode 12 to be positioned along at least a portion of the length of the elongated lesion 28 as illustrated in Figure 2 A. The electrode 12 can be a single strand wire in contact with the elongated lesion 28 along the length of the elongated lesion 28 as illustrated in Figure 2A. The single strand wire can also be sufficiently flexible that it can be woven back and forth over the elongated lesion 28 as illustrated in Figure 2B. The electrode 12 can also be a mesh positioned adjacent to at least a portion of the elongated lesion 28 as illustrated in Figure 2C.

RF energy is delivered from the RF energy source 20 to the energy transfer surface 14. The electrode 12 is positioned sufficiently close to a portion of the lesion 28 such that at least a portion of the elongated lesion 28 receives energy continuously along its length. For purposes of definition, the portion of the elongated lesion 28 which receives energy continuously along its length is referred to as the treatment site 44. The transfer of energy continuously along the length of the treatment site 44 results in increased rate of healing continuously along the treatment site 44.

The enhancer 10 is not limited to the delivery of Bassett signals. Bassett waves are directed toward simulating the signal naturally produced by bone structures, as a result, a device using Bassett waves delivers a particular signal. However, the present invention is concerned with delivery of energy to the treatment site 44 and is not concerned so much with the configuration of the signal. As a result, the energy delivered by the enhancer 10 can be continuous or pulsatile but is not limited to Basset signals.

The elongated geometry of the electrode 12 maximizes the degree of enhanced healing. The elongated geometry of the electrode 12 allows energy to be transferred continuously along the length of the treatment site. Since energy is transferred continuously along the length of the treatment site 44, healing is enhanced at each point along the treatment site 44. As a result, the slow and painful natural healing process is minimized at each point within the treatment site 44.

The elongated geometry of the electrode 12 also minimizes bone tissue damage. The enhancer 10 increases the temperature along the treatment site 44 to an average temperature. To achieve the same average temperature by applying energy at non-continuous points along the elongated lesion 28, the temperature at the non-continuous points must be substantially higher than the average temperature and may exceed 42 degrees C. Sustained temperatures above 42 degrees C are known to cause bone tissue damage. Since the enhancer 10 applies energy continuously along the length of the treatment site 44, deviations from the average temperature along the length of the treatment site

44 are minimized. As a result, bone tissue damage is minimized.

The enhancer 10 can be operated in a monopolar mode by operating the electrode 12 as an RF energy emitter positioned adjacent to the elongated lesion 28. A ground pad 45 is positioned external to the patient 38 on the opposite side of the bone structure 30 from the electrode 12.

Figure 3 provides an example of the enhancer 10 operating in a monopolar mode where the bone structure 30 is a sternum 34. The ground pad

45 is positioned beneath the patient 38 on the opposite side of the bone structure 30 from the electrode 12. The presence of the ground pad 45 causes the RF energy to pass from the electrode 12 through the patient 38 and to the ground pad 45. The ground pad 45 has a larger surface area in contact with the patient 38 than the electrode 12. As a result, the RF energy from the electrode 12 disperses as it passes through the patient 38. The resulting RF energy density is weakest near the ground pad 45 and strongest near the electrode 12 and thus near the elongated lesion 28. As a result, the RF energy is concentrated near the elongated lesion 28 and disruption of the adjacent structures is minimized.

The energy can be further concentrated on the elongated lesion 28 by providing an RF insulator 46 such as PVC at the proximal side 18 of the electrode 12 as illustrated in Figure 4. The insulator 46 can be included at the proximal side 18 of the electrode 12 by applying an insulative coating or by adhering an insulative material to the proximal side 18 of the electrode 12. The RF insulator 46 limits the RF energy to passing through the distal side 16 of the electrode 12. Since the distal side 16 of the electrode 12 is positioned adjacent to the elongated lesion 28, the energy is concentrated on the elongated lesion 28.

Further, the insulator 46 minimizes disruption to adjacent structures by preventing the energy from passing through the proximal sides of the electrode 12 to the adjacent structures. As a result, the insulator 46 acts to focus the energy on the elongated lesion 28 and minimizes disruption of adjacent structures. The insulator or insulative coating can also be extended to cover portions of the distal side 16 so long as the desired portion of the electrode 12 is emitting RF energy.

Figure 5 illustrates another embodiment which includes a second RF electrode 12A with a second energy transfer surface 14A and a second proximal side 18A. As illustrated in Figure 5, the electrode 12 can be positioned on the opposite side of the elongated lesion 28 from the second electrode 12A.

In another embodiment, a substrate 48 couples the electrode 12 to the second electrode 12A as illustrated in Figure 6A. The substrate 48 is coupled to the proximal side 18 of the electrodes and extends along the length of the electrodes. The substrate 48 has a thickness similar to the thickness of the electrode 12 so it can be comfortably positioned between the patient's skin 36 and the bone structure 30. The substrate 48 has a non-tissue piercing periphery 50 to prevent further irritation to the patient 38 and is sufficiently flexible that it can at least partially conform to the contours of the bone structure 30. The substrate 48 can be constructed from an RF insulator 46 such as PVC.

In another embodiment, the substrate 48 extends along segments 52 of the electrodes 12 as illustrated in Figure 6D. As a result, implements coupled to the bone structure 30, such as wire sutures 35 coupled to a sternum 34, can be accommodated between the segments 52. Embodiments including a second electrode 12A can operate in a monopolar mode. The electrode 12 and the second electrode 12A both act as RF emitters by coupling them both to the RF energy source 20. A ground pad 45 is positioned external to the patient 38 on the opposite side of the bone structure 30 from the electrode 12. The electrode 12 and the second electrode

12A are positioned sufficiently close to at least a portion of the elongated lesion 28 such that at least a portion of the elongated lesion 28 receives energy continuously along its length. An insulator 46 can be used to focus the energy on the elongated lesion 28. The proximal side of the electrode 12 and the second proximal side 18 A of the second electrode 12A are both covered with an

RF insulator 46. The RF insulator 46 limits the RF energy to passing through the distal sides of the electrodes. Since the distal side of each electrode is positioned adjacent to the elongated lesion 28, the RF energy is concentrated on the bone structure 30. Embodiments including a second electrode 12A can also operate in a bipolar mode. In one embodiment the electrode 12 acts as an RF emitter while the second electrode 12A acts as a ground electrode. The electrode 12 is positioned on the opposite side of the elongated lesion 28 from the second electrode 12 A. An insulator 46 can be provided at the proximal side 18 of the electrode 12 and the second proximal side 18A of the second electrode 12 A.

For instance, the insulator 46 can be the substrate 48 as illustrated in Figure 7. Since the only section of the electrode 12 not covered by insulator is adjacent to the bone structure 30, the energy emitted from the electrode 12 passes directly through the bone structure 30 and through the elongated lesion 28 before passing to the second electrode 12 A. The resulting energy distribution is illustrated in Figure 7. Since the energy distribution is concentrated on the elongated lesion 28 disruption of adjacent structures is minimized.

Yet another embodiment operates in a bipolar mode and concentrates energy on the elongated lesion 28. Figure 8 illustrates the embodiment where the elongated lesion 28 is a crack 32 in a sternum 34. The sternum 34 has a posterior side 54 and an anterior side 56. The electrode 12 acts as an energy emitter while the second electrode 12A acts as a ground electrode. The electrode 12 is positioned at the posterior side 54 while the second electrode 12A is positioned at the anterior side 56. The energy must pass from the electrode 12 through the elongated lesion 28 to the second electrode 12A. Since the energy passes through the elongated lesion 28 the energy is focussed on the elongated lesion 28 while minimizing disruption to adjacent structures.

When the elongated lesion 28 is a crack 32 in the bone structure 30, the electrode 12 can also be positioned within the elongated lesion 28. Figure 9 illustrates the bone structure 30 as a sternum 34 with the electrode 12 positioned between the halves of the sternum 34. As a result, the RF energy is emitted directly into the bone structures 30 which comprise the elongated lesion 28. It is desirable that the electrode 12 be constructed thin enough that the halves of the bone structure 30 are able to contact one another despite the presence of the electrode 12. As a result, the bone structure 30 will heal around the electrode

12.

In another embodiment the enhancer 10 is used in conjunction with an enhancement substance including but not limited to a mixture of collagen with fibrinogen. The enhancement substance can highly conductive to RF energy. When the elongated lesion 28 is a crack 32 in the bone structure 30, the enhancement substance can be placed within the crack 32 before the enhancer is positioned adjacent to the elongated lesion 28. The enhancement substance increases the flow of RF energy through the crack 32. Thus, the enhancement substance further focusses the energy on the elongated lesion 28. The enhancement substance can also be a substance known to accelerate the healing of bone structures including but not limited to collagen glues. For instance, collagen glues are known to accelerate the healing of bone structures 30. These repair enhancement substances used in combination with the enhancer 10 can further accelerate the rate of healing. For instance, the heat applied to the enhancement substance can increase the rate that the substance blends with the bone and can further increase the rate of calcification.

The RF energy source 20 supplies RF energy to the electrode 12. The RF energy source 20 can be an RF generator and can be battery powered so the patient 38 is able to walk about with the enhancer 10 in place.

The sensor 24 can be a temperature sensor such as a thermocouple which provides a signal indicating the temperature at the bone structure 30. During operation of the enhancer 10, the feedback control device 26 maintains the temperature of the bone structure 30 at a desired temperature by continuously monitoring the signal from the sensor 24 and adjusting the level of RF energy delivered from the RF energy source 20 in response to the level of the signal. For instance, when the signal indicates that the temperature has fallen below the desired temperature, the feedback control device 26 increases the level of RF energy delivered. Similarly, the level of RF energy delivered is reduced when the signal indicates that the temperature exceeds the desired temperature. It is desired to maintain the temperature below 42 degrees C since it is know that tissue damage can occur above this level.

The sensor 24 can be positioned anywhere where the signal provided by the sensor 24 indicates the conditions at the bone structure 30. For instance, the sensor 24 can be positioned within the electrode 12 (Figure 1 A), on the surface of distal side 16 of the electrode 12 (Figure 6) or on the surface of the substrate 40 (Figure 5 A). The sensor 24 can be a single sensor, a plurality of sensors or a band as illustrated in Figure 5A.

The sensor 24 may be a plurality of temperature sensors located at discrete positions along the electrode 12 as illustrated in Figure 3. The feedback control device 26 adjusts the level of RF energy in response to the signal from any single sensor. For instance, if one sensor indicates the temperature at that sensors is greater than 42 degrees C while the other sensors indicate the temperature is below 42 degrees C, the feedback control device 26 reduces the level of RF energy to prevent cell necrosis near the single sensor. As a result tissue damage which can result from concentrations of heat within the sternum 34 can be avoided.

The electrodes 12 and substrate 40 can be constructed from or coated with a biocompatable material such as Zyderm 2 produced by Collagen Corporation, Palo Alto, California. As a result, each electrode 12 can be left in place within the patient 38. Further, the electrode 12 and substrate 40 can be constructed from a bioabsorbable material. Thus, each electrode left within the body will eventually be absorbed into the body. Bioabsorbability is advantageous when the electrode 12 is positioned within the elongated lesion 28 as illustrated in Figure 9. The bone structure 30 will initially heal around the electrode 12 and as the electrode 12 is absorbed the bone structure 30 will heal where the electrode 12 was previously located. As a result, the bone structure 30 will return to nearly its original strength over time.

The cable 22 extends percutaneously through a puncture 40 in the patient's skin 36. As illustrated in Figure IC, the portion of the cable 22 positioned within the patient's body can carry the signal from the sensor 24 to the feedback control device 26 as well as the RF energy from the RF energy source 20 to each electrode 12. The cable 22 can have a biocompatable coating such as PVC in order to prevent infection at the puncture 40 site and to prevent the skin 36 from attaching to the cable 22.

Referring again to Figure 1 A, a decoupler 58 is illustrated between the RF energy source 20 and the electrode 12. The decoupler 58 allows the cable 22 to be easily decoupled from the electrodes. The decoupler 58 can be located outside the patients body as illustrated in Figure IC. The patient 38 or physician can decouple the cable 22 so that the patient 38 is free to move about.

Figure 10A illustrates an embodiment where the decoupler 58 is adjacent to the electrode 12. The electrode 12 has at least one lead 60 and the decoupler 58 has a plurality of contacts 62 which are complimentary to the at least one lead 60. The friction between the at least one lead 60 and the contacts 62 holds the decoupler 58 in place on the electrode 12. When the enhancer 10 is in place on the patient 38 the decoupler 58 is positioned beneath the patient's skin 36. When the bone structure 30 is healed, the decoupler 58 an&cable 22 can be quickly and easily removed by applying pressure to the electrode 12 through the patient's skin 36 and pulling on the cable 22 to uncouple the contacts 62 from the at least one lead 60. The cable 22 and decoupler 58 are then removed through the puncture 40 in patient's skin 36. As a result, the electrode(s) 12 are left in place beneath the patient's skin 36.

The electrode 12 can be made from a number of materials including but not limited to stainless steel, platinum, other noble metals and the like. The electrode 12 can also be made from a memory metal such as nickel titanium available from RayChem Corporation, Menlo Park, CA. It may be desirable to construct the electrode 12 from a composite of a first material which conducts RF energy and a second material which acts as an RF insulator. The second material can function as the insulator 46 of Figure 4. Another embodiment provides a method for enhancing the repair of an elongated lesion coupled to a bone structure. The method specifies providing a bone growth enhancer including at least one energy transfer surface of sufficient length to enhance bone repair along at least a portion of the length of the elongated lesion. The energy transfer surface is positioned sufficiently close to the elongated lesion such that energy directed from the energy transfer surface reaches the elongated lesion. Sufficient energy is delivered to the elongated lesion to enhance repair of the elongated lesion while minimizing disruption of adjacent structures.

The energy can be delivered to the elongated lesion by operating the enhancer in a bipolar or by operating the enhancer in a monopolar mode. In another embodiment the method includes the step of applying an enhancement substance to the elongated lesion. Yet another embodiment includes the step of removing the at least one energy delivery surface from the bone structure.

While the above disclosure often uses the sternum as an illustration, the enhancer can be used with any elongate lesion. Elongated lesions can be any damaged bone tissue with a length substantially greater than the diameter of the „ bone and can result from elective surgery or sudden trauma. Examples of elongated lesions include splintering of a bone structure as illustrated in Figure 2B and bruises along the length of the bone structure as illustrated in Figure 2C. Many of the above embodiments will have an obvious and identifiable distal side 16 and proximal side 18. However, many of the above embodiments have a symmetrical cross section along the entire length of the electrode 12. As a result, in some embodiments, the proximal side 18 and distal side 16 of each electrode 12 is not identifiable until the electrode 12 is positioned adjacent to the elongated lesion 28.

The foregoing description of the preferred embodiment of the invention has been for the purpose of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications, variations and combinations will be apparent to practitioners skilled in this art. It is intended that the scope of the invention be defined by the following claims and their equivalents. What is claimed is:

Claims

1. An apparatus for delivery of an RF energy to a bone structure, comprising: a first RF electrode having at least one first portion and at least one second portion, the at least one first portion configured to be positioned adjacent to the bone structure; a second RF electrode; and a substrate coupled to the first and second RF electrodes, the substrate having a thickness that permits placement of the substrate in a cavity between a skin layer and a bone structure.

2. The apparatus of claim 1, further comprising: a sensor coupled to the substrate.

3. The apparatus of claim 2, wherein the sensor is a thermal sensor.

4. The apparatus of claim 2, wherein the sensor is positioned on the substrate.

5. The apparatus of claim 2, wherein the sensor is positioned on the substrate to be responsive to a temperature of the bone structure.

6. The apparatus of claim 1 , further comprising: a biocompatable coating on a surface of the substrate.

7. The apparatus of claim 1, further comprising: a cable configured to be coupled with the first and second RF electrodes.

8. The apparatus of claim 1 , wherein the bone structure is a sternum including an elongated lesion and the first and second RF electrodes are positioned on the apparatus to direct RF energy to the elongated lesion.

9. The apparatus of claim 1, further comprising: a cable configured to couple the first and second RF electrodes to a battery powered energy source.

10. The apparatus of claim 1 , wherein the first and second RF electrodes operate in a bipolar mode.

11. The apparatus of claim 1 , wherein the first and second RF electrodes are configured to deliver RF energy.

12. The apparatus of claim 1, further comprising: a cable; and a decoupler included on the cable and configured to be removably coupled with the first and second RF electrodes.

13. The apparatus of claim 1 , further comprising: a decoupler positioned on one of the first and second electrode.

14. The apparatus of claim 1 wherein the substrate has a shape which approximates a shape of a sternum.

15. A system for controlled delivery of an RF energy to a bone structure, comprising: an FIF electrode having at least one first portion and at least one second portion, the at least one first portion configured to be positioned adjacent to the bone structure; a sensor coupled to the RF electrode; and a feedback control device coupled to the sensor andxonfigured to be coupled to an RF energy source.

16. The system of claim 15, wherein the sensor is a thermal sensor.

17. The system of claim 15 , further comprising : a biocompatable coating on the surface of the RF electrode.

18. The system of claim 15, further comprising: a cable configured to be coupled with the RF electrode.

19. The system of claim 15, wherein the substrate has a shape which approximates a shape of a sternum.

20. The system of claim 15, further comprising: a cable configured to couple the RF electrode to a battery powered energy source.

21. The system of claim 15, further comprising: a second RP electrode coupled with the RF electrode.

22. The system of claim 21 , wherein the second RF electrode has an elongated geometry.

23. The system of claim 22, wherein the second RF electrode has a length sufficient to enhance repair along at least a portion of the wound.

24. The system of claim 23, wherein the second RF electrode has non-tissue piercing surface.

25. The system of claim 21 , wherein the RF electrode and the second RF electrode operate in a bipolar mode.

26. The system of claim 21 , wherein the RF electrode and the second RF electrode are configured to be positioned between the bone structure and an overlying skin surface.

27. The system of claim 23, wherein the bone structure is a sternum with a anterior surface and a posterior surface, the RF electrode is configured to be positioned at the anterior surface and the second RF electrode is configured to be positioned at the posterior surface.

28. The system of claim 15 further comprising: a cable; and a decoupler included on the cable and configured to be removably coupled with the RF electrode.

29. A method for enhancing the repair of an elongated lesion coupled to a bone structure, comprising: providing a bone growth enhancer including an energy transfer surface of sufficient length to enhance bone repair along at least a portion of the length of the elongated lesion; positioning the energy transfer surface sufficiently close to the elongated lesion to direct energy from the energy transfer surface to the elongated lesion; delivering sufficient energy to the elongated lesion to enhance repair of the elongated lesion while minimizing disruption of adjacent structures.

30. The method of claim 29, further comprising: detecting a temperature adjacent to the elongated lesion while energy is delivered to the elongated lesion.

31. The method of claim 29, wherein at least a portion of the enhancer is made of a bioabsorbable material.

32. The method of claim 29, wherein the enhancer includes a second energy transfer surface.

33. The method of claim 32, wherein the energy transfer surface and the second energy transfer surface are positioned adjacent to each other.

34. The method of claim 32, wherein the energy transfer surface and the second energy transfer surface are positioned on opposite sides of the bone structure.

35. The method of claim 29, wherein the elongated lesion is a crack in the bone structure.

36. The method of claim 35, wherein the bone structure is the sternum.

37. The method of claim 29, wherein the enhancer includes a first RF electrode.

38. The method of claim 37, wherein the RF electrode is positioned adjacent to at least a portion of the elongated lesion.

39. The method of claim 29, wherein the enhancer includes a first RF electrode and a second RF electrode.

40. The method of claim 39, wherein the bone structure is a sternum with a posterior surface and an anterior surface, the first RF electrode is positioned at the anterior surface and the second RF electrode is positioned at the posterior surface.

41. The method of claim 39, wherein the second RF electrode acts as a ground electrode and the enhancer operates a bipolar mode.

42. The method of claim 39, wherein the first RF electrode and the second RF electrode operate in a monopolar mode.

43. The method of claim 29, further comprising: applying a bone repair enhancement substance to the elongated lesion.

44. The method of claim 29, further comprising: removing the energy delivery surface from the bone structure.

45. A system for controlled delivery of energy to a bone structure, comprising: an RF electrode having shaped matched to a contour of a surface the bone structure; a sensor coupled to the RF electrode; and a feedback control device coupled to the sensor and configured to be coupled to an RF energy source.