WO2004011092A1 - Technique et dispositif de traitement de douleurs dorsales - Google Patents

Technique et dispositif de traitement de douleurs dorsales Download PDF

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Publication number
WO2004011092A1
WO2004011092A1 PCT/US2003/023330 US0323330W WO2004011092A1 WO 2004011092 A1 WO2004011092 A1 WO 2004011092A1 US 0323330 W US0323330 W US 0323330W WO 2004011092 A1 WO2004011092 A1 WO 2004011092A1
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WIPO (PCT)
Prior art keywords
disc
delivery device
energy delivery
wall
energy
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PCT/US2003/023330
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English (en)
Inventor
Wolfgang Daum
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Triton Biosystems, Inc.
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Application filed by Triton Biosystems, Inc. filed Critical Triton Biosystems, Inc.
Priority to AU2003256815A priority Critical patent/AU2003256815A1/en
Publication of WO2004011092A1 publication Critical patent/WO2004011092A1/fr

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/40—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals
    • A61N1/403—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals for thermotherapy, e.g. hyperthermia
    • A61N1/406—Applying electric fields by inductive or capacitive coupling ; Applying radio-frequency signals for thermotherapy, e.g. hyperthermia using implantable thermoseeds or injected particles for localized hyperthermia

Definitions

  • This invention relates to a method and devices to modify human or animal intervertebral disc tissue, especially annular fissures which are the cause of back pain.
  • the invention uses an implant and an inductive heating process of such.
  • the intervertebral disc 1 primarily serves as a mechanical cushion between the vertebral bones 2a and 2b, permitting controlled motions within vertebral segments of the axial skeleton.
  • the normal disc is a unique, mixed structure, comprised of three component tissues: the nucleus pulposus 7 ("nucleus”), the annulus fibrosus 8 (“annulus”) and two vertebral end plates .
  • the two vertebral end plates are composed of thin cartilage overlying a thin layer of hard, cortical bone which attaches to the spongy, richly vascular, cancellous bone of the vertebral body. The end plates thus act to attach adjacent vertebrae to the disc. In other words, a transitional zone is created by the end plates between the malleable disc and the bony vertebrae.
  • the annulus 8 of the disc is a tough, outer fibrous ring which binds together adjacent vertebrae.
  • This fibrous portion which is much like a laminated automobile tire, is generally about 10 to 15 millimeters in height and about 15 to 20 millimeters in thickness.
  • the fiber layers 12 of the annulus 8 consist of fifteen to twenty overlapping multiple plies 12, and are inserted into the superior and inferior vertebral bodies at roughly a forty degree angle 16 in both directions. This configuration particularly resists torsion, as about half of the angulated fibers will tighten when the vertebrae rotate in either direction, relative to each other.
  • the laminated plies are less firmly attached to each other.
  • the healthy nucleus 7 is largely a gel-like substance having a high water content, and like air in a tire, serves to keep the annulus 8 tight yet flexible.
  • the nucleus- gel moves slightly within the annulus 8 when force is exerted on the adjacent vertebrae with bending, lifting, etc.
  • the nucleus and the inner portion of the annulus 8 have no direct blood supply.
  • the principal nutritional source for the central disc arises from circulation within the vertebral body.
  • Microscopic, villous-like fingerlings of the nucleus and annulus 8 tissue penetrate the vertebral end plates and allow fluids to pass from the blood across the cell membrane of the fingerlings and then inward to the nuclear tissue.
  • These fluids are primarily body water and the smallest molecular weight nutrients and electrolytes.
  • the natural physiology of the nucleus 7 promotes these fluids being brought into and released from the nucleus by cyclic loading. When fluid is forced out of the nucleus 7, it passes again through the end plates and then back into the richly vascular vertebral bodies.
  • This cyclic loading amounts to daily variations in applied pressure on the vertebral column (body weight and muscle pull) causing the nucleus 7 to expel fluids, followed by periods of relaxation and rest, resulting in fluid absorption or swelling by the nucleus 7.
  • the nucleus 7 changes volume under loaded and non-loaded conditions.
  • the tightening and loosening effect stimulates normal annulus 8 collagen fibers to remain healthy or to regenerate when torn, a process found in all normal ligaments related to body joints.
  • the ability of the nucleus 7 to release and imbibe fluids allows the spine to alter its height and flexibility through periods of loading or relaxation.
  • Chronic lumbar pain is a common cause of disability, with an estimated 5% of the American population suffering from chronic, disabling low back pain. Acute low back pain often responds to physical therapy and activity modification.
  • Chronic recurrent patients have multiple pain flares with varying durations of two weeks to three months. Many patients within this group will begin to have more frequent recurrences with fewer pain-free intervals as time passes.
  • Chronic persistent patients have persistent symptoms that do not abate and last longer than three months. The disc has been shown to be the pain source in the vast majority of patients with chronic symptoms. Carey T.
  • Mechanoreceptors in the disc wall have been shown to discharge with disc mobilization (Robert S. et al., Mechanoreceptors in intervertebral discs, Spine 20:2645-2651, 1995).
  • a scenario for chronic discogenic pain is created when any combination of annular fissures, delaminating, or micro fractures of collagen fibrils leads to mechanical distortion of annular lamellae.
  • a combination of mechanical and neural properties creates an interplay that leads to chronic discogenic pain.
  • Disc bulging is always associated with annular degeneration and fissures; however, this phenomenon does not always create clinically significant low back pain.
  • Lumbar disc herniation is a distinct pathologic entity. Lumbar intervertebral disc herniation typically occurs as a result of annular degeneration leading to weakening of the annulus fibrosis, leaving it susceptible to annular Assuring 15 and tearing. Nuclear migration caused by annular disruption leads to the most common forms of clinically recognized lumbar disc herniation (LDH) (i.e., contained, extruded, and sequestered).
  • LDH lumbar disc herniation
  • the spinal canal location of disc trespass will determine the type of neural compromise and clinical pain pattern.
  • the degree of neural compromise cannot be judged accurately by the size, type, or location of the disc material (Saal J.A., Natural history of nonoperative treatment of lumbar disc herniation, Spine 21; 2S-9s, 1996).
  • the leg pain disc which is the classic disc herniation with nuclear migration
  • the back pain disc which is the internally disrupted disc (discogenic pain) with annular pathology creating back pain, and variable amounts of leg and buttocks pain
  • a mixed pattern such as with small-contained disc herniation and central hemiation.
  • the postoperative disc can be a source of pain that mimics internal disc derangement.
  • chronic lumbar pain is discogenic. It is estimated, however, that more than 50% of patients with chronic low back pain have the disc as the primary source of pain.
  • Intervertebral disc abnormalities have a high incidence in the population and may result in pain and discomfort if they impinge on or irritate nerves.
  • Disc abnormalities may be the result of trauma, repetitive use, metabolic disorders and the aging process and include such disorders but are not limited to degenerative discs (i) localized tears or fissures in the annulus fibrosus, (ii) localized disc hemiations with contained or escaped extrusions, and (iii) chronic, circumferential bulging disc.
  • Disc fissures occur rather easily after structural degeneration (a part of the aging process that may be accelerated by trauma) of fibrous components of the annulus fibrosus. Sneezing, bending or just attrition can tear these degenerated annulus fibers, creating a fissure.
  • the fissure may or may not be accompanied by extrusion of nucleus pulposus material into or beyond the annulus fibrosus.
  • the fissure itself may be the sole morphological change, above and beyond generalized degenerative changes in the connective tissue of the disc. Even if there is no visible extrusion, biochemicals within the disc may still irritate surrounding structures. Disc fissures can be debilitatingly painful.
  • Treatment options for discogenic pain include conservative measures such as physical therapy and steroid injection; and more aggressive strategies include surgery with discectomy and spinal fusion.
  • the fissure may also be associated with a herniation of that portion of the annulus.
  • Treatment methods include reduction of pressure on the annulus by removing some of the interior nucleus pulposus material by percutaneous nuclectomy.
  • complications include disc space infection, nerve root injury, hematoma formation, instability of the adjacent vertebrae and collapse of the disc from decrease in height.
  • Nuclectomy can be performed by removing some of the nucleus to reduce pressure on the annulus.
  • complications include disc space infection, nerve root injury, hematoma formation, and instability of adjacent vertebrae.
  • IDT intradiscal electrothermal therapy
  • the IDET process takes about an hour to complete and is performed as follows:
  • the procedure is performed with a local anaesthetic and mild intravenous sedation.
  • a hollow introducer needle is inserted into the painful lumbar disc space using a portable x-ray machine for proper placement.
  • An electrothermal catheter (heating wire) is then passed through the needle and positioned along the back inner wall of the disc (the annulus), the site believed to be responsible for the chronic pain.
  • the catheter tip is then slowly heated up to 90 °C for 15-17 minutes. 5. The heat contracts and thickens the collagen fibers making up the disc wall, thereby promoting closure of the tears and cracks. Tiny nerve endings within these tears are cauterized (burned), making them less sensitive. 6. The catheter is removed along with the needle and, after a short period of observation, the patient goes home. 7. A lumbar support is worn for 6 to 8 weeks, followed by an appropriate course of physical therapy.
  • the IDET procedure is then repeated whenever needed.
  • the disc itself is a virtually avascular structure, and heat does not travel as easily in it as in other soft tissues. This environment allows heat to be held in the tissue with relatively little fluctuation during treatment. Adjacent structures are protected from thermal injury by the vascular circulation outside the disc, which quickly dissipates any heat escaping from the disc.
  • a catheter based heating system as described in U.S. Patent Nos. 6,290,715 and 6,261 ,311 , has the ability to deliver energy at the point of contact. Heat is transferred by conduction from the catheter to the adjacent tissue. Temperature sensors deliver feedback to the generator, which adjusts power levels as necessary to reach and maintain set target temperatures. Identifying the precise temperatures needed to affect the disc tissue and having the power to produce the required temperature in the disc offers a high degree of accuracy and consistency to this treatment. Letcher F. et al., The effect of radiofrequency current and heat on peripheral nerve action potential in the cat, J. Neurosurg. 29_:42-47, 1968, established that irreversible nerve blocks occur at 45°C in the brain, and Cosman E. R.
  • Thermal shrinkage of collagen is also dependent on the duration of the application of heat. Lower temperatures over a longer period of time result in shrinkage comparable with that achieved with a higher temperature over a shorter period of time. Under these parameters, IDET is capable of causing shrinkage of the collagenous fibers of the disc annulus. Typically, the IDET therapy has to be repeated several times to be successful. The repeated placement of the catheter is both costly and painful for the patient.
  • Intradiscal applications of other available thermal energy sources have limitations when compared with temperature-controlled thermal resistive heating. Radio frequency delivered by an intradiscal needle electrode cannot transfer the necessary range of thermal energy to achieve the desired effects, and a needle delivery system cannot access the broad expanse of the posterior annular wall. Intradiscal laser energy is potentially hazardous to bone and nerve tissue because of the lack of temperature control and extent of tissues heated.
  • intradiscal electrothermal therapy IDET can be very effective in back pain therapy. Since back pain is a constant problem to a patient the procedure has to be repeated over, during a long period. It is therefore of advantage to have a procedure in which the interventional process is replaced by a non-interventional process.
  • This invention proposes an implant which is deployed in the spinal disk and which can be repetitively heated by an inductive heating process. The replacement of a heating catheter with a permanent, or semi-permanent, implant eliminates the need for repeatedly invasive processes.
  • the invention further suggests materials and shapes of the implant and an inductive heating device.
  • one embodiment of the invention is directed to a method of delivering energy adjacent an inner wall of an intervertebral disc.
  • the method comprises positioning an energy delivery device adjacent the inner wall of the intervertebral disc, and inductively heating the energy delivery device from outside the intervertebral disc. Heat is provided from the heated implant to the inner wall of the intervertebral disc.
  • Another embodiment of the invention is directed to a system for delivering energy adjacent an inner wall of an intervertebral disc treating back pain.
  • the system comprises a source of rf energy and an rf radiator coupled to radiate rf energy form the source of rf energy.
  • the system also comprises an implantable device capable of being implanted within the intervertebral disc.
  • the implantable device is inductively heated by energy received from the rf radiator when the implantable device is implanted within the intervertebral disc.
  • Another embodiment of the invention is directed to a system for delivering an inductively heatable implant adjacent an inner wall of an intervertebral disc treating back pain.
  • the system comprises an introducer needle adapted for penetrating within the annulus fibrosus of the disc.
  • an inductively heatable implant comprising a wire.
  • the inductively heatable implant is disposed within the introducer needle.
  • the introducer needle is adapted to expel the inductively heatable implant into the nucleus pulposus of the disc, and to leave the inductively heatable implant within the nucleus pulposus.
  • FIG. 1 shows a three dimensional view of an intervertebral disc located between two lumbar discs. The spinal nerves branch out lateralis.
  • FIG. 2 shows a sagittal cross sectional view of a part of the lumbar spinal column without the spinal cord shown.
  • FIG. 3 a transverse cross sectional view of a middle lumbar intervertebral disc.
  • FIG. 4 shows is a transverse cross sectional view of a middle lumbar intervertebral disc with an embodiment of a general implant according to principles of the present invention.
  • FIG. 5 schematically shows an embodiment of an inductive heating system according to principles of the present invention.
  • FIG. 6 shows a schematic electrical circuit for an embodiment of a power generator - oscillator unit, according to principles of the present invention.
  • FIGs. 7 A and 7B schematically illustrate two different embodiments of inductor coils useful in reducing the electrical component of the rf (radio frequency) field, according to principles of the present invention.
  • FIG. 8 shows a graph of eddy current vs. frequency with permeability as a parameter, in accordance with principles of the present invention.
  • FIG. 9 shows a graph of eddy current vs. frequency with permeability as a parameter, in accordance with principles of the present invention.
  • FIG. 10 illustrates a graph of eddy current vs. frequency with coating thickness as a parameter in accordance with principles of the present invention.
  • FIG. 11 illustrates a graph of eddy current vs. frequency and permeability in accordance with principles of the present invention.
  • FIG. 12 illustrates a graph of eddy current vs. coating thickness with permeability as a parameter in accordance with principles of the present invention.
  • FIG. 13 illustrates a graph of eddy current vs. permeability with coating thickness as a parameter in accordance with principles of the present invention.
  • FIG. 14 illustrates a graph of eddy current vs. coating thickness with frequency as a parameter in accordance with principles of the present invention.
  • FIGs. 15a-15d show a sequence of views in the horizontal plane of the spinal disc with an embodiment of an implant being deployed, according to principles of the present invention.
  • FIG. 16 schematically illustrates another embodiment of an inductive heating system according to principles of the present invention.
  • FIG. 3 shows a cross-sectional-axial view (horizontal plane) of a spinal disc 1 with a fissure 15 on the left dorsal side, causing the liquid-like nucleus pulposus to "leak", causing pressure on a left spinal nerve 4.
  • FIG. 2 shows a sagittal view (median plane).
  • FIG. 4 A general approach according to the present invention is schematically presented in FIG. 4.
  • An implant 17 is deployed in the nucleus pulposus 7 on the inner wall of the annulus fibrosus 8.
  • the implant 17 itself or just a portion 18 of is made of a material of a high enough magnetic susceptibility to be heated inductively. The heating may take place by inductively heating the implant 17 using an inductive heating system outside the disc. Where an extra-corporal inductive heating system is used, the patient may receive heat treatment non-invasively, where the only invasion is to position the implant.
  • the implant 17 may be a permanent implant or a temporary implant.
  • the implant 17 may be positioned to treat any portion of the inner wall, including a posterior medial region, a posterior lateral region, an anterior medial region and/or an anterior lateral region of the inner wall of the annulus fibrosus.
  • FIG. 5 A basic set up of an embodiment of a system used for the treatment of back pain is schematically presented in FIG. 5.
  • the patient 19 is lying on the patient bed 24, for example in a prone position.
  • the inductor coil 20 hangs on a inductor holder 21 above the patient 19.
  • the rf (radio frequency) signal having a particular power and the frequency, is generated by the generator-oscillator unit 22, which may be controlled from a display-console panel 23.
  • the set-up illustrated in FIG. 5 is presented as an example of the system. In the illustrated embodiment, the inductor coil 20 does not touch the patient 19.
  • the inductor coil 20 may be mounted dorsal to the patient, as shown, or anterior to the patient.
  • the inductor coil 20 may surround the whole patient. It may be of benefit if the patient 19 is sitting or standing dorsal, anterior or even lateralis to the inductor coil 20.
  • the inductive heating system may be oriented differently relative to the patient than shown in FIG. 5.
  • the patient may be positioned on a support so that the patient is within an inductance coil, for example as taught in U.S. Patent No. 6,238,421, incorporated herein by reference.
  • the induction heating process may be carried out using a power generator - oscillator unit, an embodiment of which is illustrated in FIG. 6.
  • the desired frequency range is preferably between 50 Hz and 2 MHz, and more preferably between 100 kHz and 600 kHz and may usually be set to 250 kHz. It has been found that at frequencies above 1 MHz, heating is not restricted to the implant, and the surrounding tissue itself also heats up.
  • the sending antenna 100 itself may include an inductive component 101 and a capacitive component 102.
  • the antenna 100 is supplied with a radio frequency, high voltage signal 118.
  • the antenna 100 is preferably electrically matched to the oscillator 104 by a matching transformer 103 to maintain efficient operation.
  • the whole system may be supplied with electrical power, for example, 210 kVA at 50 Hz or 60 Hz at the low voltage end 112.
  • a computer 115 may be used to control the voltage at a thyristor unit 110.
  • Feedback 108 may be measured before the voltage is transformed in the transformer 107 to high voltage AC 120 and rectified 106 to load the oscillator 104.
  • a current flows in the induction coil 20 to produce an alternating magnetic field (AMF).
  • AMF alternating magnetic field
  • the AMF inductively heats the implant 17, for example due to eddy currents that arise from the AMF.
  • the electric energy supplied by the induction coil is first converted to magnetic energy, which is then converted to heat in the implant 17.
  • the current density in implant 17 is determined to some extent by the skin-effect. The highest current density is reached at the surface of the implant 17. The current density drops off inside the implant exponentially.
  • I IND Current in the induction coil
  • ⁇ Relative permeability of material piece
  • ⁇ 0 p Specific resistance of material piece in ⁇ mm 2 /m
  • the constant k can be empirically determined, and is related, at least in part, to the coupling factors of the physical arrangement.
  • the inductive heating power P varies quadratically with the current in the transmitting coil I I ND, and according to the square root of the specific resistance p, the permeability ⁇ and the frequency f.
  • the resistance and permeability are set in by the implant material.
  • the primary goal is to increase frequency and induction current. Increasing the frequency simultaneously increases absorption and decreases the skin-effect.
  • the penetration depth of the current in the implant, due to the skin-effect, is:
  • the skin-effect requires a certain minimal frequency at which the coupling eddy currents are effective. When the frequency is made lower, the heating effect is reduced. The heating effect is better when the frequency is increased. However, at a certain value of frequency, above about 1 MHz, the tissue is also heated, along with the implant, and so tissue heating sets an upper limit on the operational frequency.
  • the correlation among the specific resistance, permeability and coupling power is important. If the specific resistance of the material decreases, one can take advantage of the skin-effect even at low frequencies.
  • the basic principle of excitation of the heating process may be described in terms of an L-C-parallel-resonant-circuit.
  • the thickness, d, of the implant is very small compared to the diameter D of the sending inductor loop (d/D ⁇ 0.001, d is the diameter of a wire), it is possible to use a simple solution for inductance L:
  • the blind current through the coil is calculated as follows:
  • An objective of the present invention is to self-regulate temperature by means of material modification and application of the Curie effect.
  • tissue are seen to heat up.
  • the electrical and the magnetic components of the rf field contribute differently to the heating of the tissue itself.
  • Some tissue types heat up when using rf frequencies between 500 kHz and 1 MHz.
  • tissue heating at a frequency of less than 1 MHz was avoided.
  • FIG. 7a shows an arrangement in which the patient may be located within the coil 27.
  • the inductor coil 27 surrounds the patient.
  • FIG. 7b shows an inductor coil 31 , which may be placed dorsal or anterior to the patient. The patient is located proximal to that side of the arrangement in FIG. 7b, where the metal plates 32 bend.
  • the inductor coils 27 and 31 may be made out of a tube, with water, or other coolant flowing therethrough to cool down the inductor coil itself. This tubing may be formed from copper, for good heat conduction.
  • Metal plates 28 or 32 may be formed as stripes and are located in the two arrangements in such a way that they are parallel to the field lines of the magnetic rf component and perpendicular to the field lines of the electrical component. This results in the magnetic field components of the rf field being passed and the electrical field components of the rf field being blocked.
  • the material for these stripes may be copper for good heat conduction.
  • a copper cooling tube 26 or 30, carrying coolant, may be is attached to the stripes 28 or 32.
  • the whole arrangement may be covered with an electrical insulating cover 25 or 29, which might be made out of any plastic, such as PTFE, PEEK, PE, PP or PU.
  • the stripes 28 or 32 may be 1 to 4 mm in width and 0.2 to 0.5 mm in thickness.
  • the water flow through the induction coil 27 or 31 may be between 4 and 20 liter/minute at 6 bar.
  • FIG. 16 Another approach to inductively heating the implant is to place it in the AMF formed in a magnetic circuit, for example between two pole pieces.
  • a generator 1601 produces an AMF that may be guided to a specific location within a subject 1605 by a magnetic circuit 1602.
  • the magnetic circuit is c-shaped, although it will be appreciated that other shapes may also be used.
  • the subject 1605 typically lies upon an X-Y horizontal and vertical axis positioning bed 1606, between the pole pieces 1604 of the c-shaped magentic circuit.
  • the positioning bed 1606 can be positioned horizontally and vertically via a bed controller 1608.
  • the AMF generator 1601 produces an AMF in the magnetic circuit 1602 that exits the magnetic circuit 1602 at one pole face 1604, passes through the air gap and the desired treatment area of the subject 1605, and reenters magnetic circuit 1602 through the opposing pole face 1604, thus completing the circuit.
  • An operator or medical technician may control and monitor the AMF characteristics and bed positioning via a control panel 1620.
  • the frequency of the AMF may be in the range of about 100 kHz to about 600 kHz, although other frequencies may also be used.
  • a ring, or circuit, 1602 of low reluctance magnetic material may be specifically formulated for magnetic cores operating at a desired frequency, for example around 150 kHz or 250 kHz.
  • a desired frequency for example around 150 kHz or 250 kHz.
  • Fluxtrol material commercially available from Manufacturing Inc., Auburn Hills, MI, USA.
  • the implant 17 is mainly to be found in the use of a material that possesses increased receptivity for the electromagnetic field strength, which depends on a high degree of magnetic permeability or magnetic susceptibility.
  • a further phenomenon is also put to use, in which the warming of the implant occurs by means of the incidental eddy current losses.
  • the eddy current is increased through the correct choice of the material and the construction of the implant to the degree that considerably more heat is absorbed with very little additional technological effort.
  • the energy delivered to the disc via the implant 17 may be controlled so that no vaporization of tissue or other material occurs close to the inner wall of the disc.
  • the energy may be controlled so that no material other than water is removed adjacent the inner wall of the disc, and/or that no destructive lesion is formed adjacent the inner wall of the disc.
  • f w 8 - p / ⁇ ' D 2
  • p the specific of the resistance material
  • ⁇ the product of permeability and of relative permeability
  • D the thickness of the material
  • the frequency typically is far below that of commonly used generator frequencies.
  • the implant 17 is formed of a material having a permeability of more than 100.
  • the permeability preferably has a value of several thousand.
  • Some preferred metal alloys include a nickel-iron alloy or a palladium-cobalt alloy, but other alloys, such as nickel- copper, nickel-palladium, palladium-cobalt and nickel-silicon, etc., may also be utilized.
  • the metal alloy possesses a Curie temperature that may be used to ensure that implant 17 is maintained below a certain at a maximum temperature.
  • the Curie point of the material with the help of the alloy composition can, for example, be designed to allow temperatures ranging between 60 °C and 75 °C, and preferably about 65 °C.
  • the implant made of this alloy may be coated with gold or with a different overlay so that the entire arrangement is corrosion resistant and highly conductive.
  • the gold coating is varied up to a thickness of 5 ⁇ m with 0.5 ⁇ m increments.
  • the frequency ranges from 100 kHz to 1 MHz.
  • Relative magnetic permeability is 1 to 2,000.
  • the investigated parameter of all simulations is the in-coupled heat generated or lost due to eddy currents. The eddy current losses are shows as a function of excitation frequency, with the coating thickness being 0.5 micrometers.
  • FIG. 10 Two series of curves are shown in FIG. 10 for increasing permeability, with one series corresponding to a coating thickness of 0.5 ⁇ m and the other series corresponding to a coating thickness of 2.5 ⁇ m.
  • the in-coupled power, relative to the thickness of the coating, the permeability and the frequency, is shown in FIG. 11. It can be seen that the maximum value is achieved with the thinnest coating (0.5 ⁇ m) and highest permeability (2,000) as well as the highest frequency (1 MHz).
  • the coating thickness is varied with fixed frequency and permeability.
  • FIG. 12 shows the variation in eddy current as a function of the coating thickness.
  • the maximum in-coupled eddy current loss is also a function of the relative permeability. Above a value of 1,000, the coating thickness lies under 0.5 ⁇ m.
  • FIG. 13 shows a graph of eddy current loss as a function of relative permeability, for different coating thicknesses.
  • a very conductive thin coating around a core with high permeability improves the absorption of the heat generated.
  • the heat energy is primarily produced in the coating.
  • the thickness of the coating depends on the chosen excitation frequency and on the permeability of the core. At a relative permeability of several thousand, a gold coating is preferably less than 0.5 ⁇ m thick if the core only has a diameter of 90 ⁇ m. High excitation frequencies (>500 kHz) also lead to the use of thin coatings ( ⁇ 0.5 ⁇ m).
  • the Curie effect is indirectly contained in the permeability variation.
  • permeability decreases at higher temperatures.
  • the behavior of the permeability temperature ratio is, therefore, material dependent.
  • the performance can drop by factors up to several 100,000.
  • Table 1 lists the some ferromagnetic materials that are suitable as starting materials for the process described here.
  • the implant 17 may also be composed of one or more alloys, for example, nickel-copper alloys (described in Table 2), nickel-palladium alloys (described in Table 3), palladium- cobalt alloys (described in Table 4), nickel-iron alloys; and nickel-silicon alloys (described in Table 5).
  • nickel-copper alloys described in Table 2
  • nickel-palladium alloys described in Table 3
  • palladium- cobalt alloys described in Table 4
  • nickel-iron alloys nickel-iron alloys
  • nickel-silicon alloys described in Table 5
  • the palladium-cobalt alloy is interesting because, besides having ferromagnetic properties, it also behaves like palladium in pure form. Looking at its material properties, it has an extraordinary corrosion resistance in a very broad pH spectrum. Palladium alloys have been used for quite some time in dental medicine for permanent oral implants, and besides palladium's biocompatibility, there is clinical evidence of mechanical durability. Additionally, there is extensive clinical experience since its introduction in 1986 regarding its use in branchy-therapy with radioactive Pd implants for treating prostate carcinoma. In conjunction with the above named Pd-Co alloy, it is possible to reach a Curie temperature of 50°C in vitro and in calorimetric experiments. Nickel-Iron alloys
  • Biocompatibility is primarily achieved through the use of a coating of gold or other biocompatible material.
  • a stable Curie temperature of 50°C is maintained at different water flow rates.
  • Ni:Si thermoseeds Data exist for in vitro as well as in vivo Ni:Si thermoseeds.
  • the pure uncoated Ni:Si alloys are cytotoxic in vitro and in vivo, and so a coating, e.g. in the form of a plastic catheter, may be used.
  • a coating e.g. in the form of a plastic catheter.
  • dendrite arms appear, which may be reduced at considerable cost; however, they do negatively impact the ferromagnetic properties. The process to reduce the dendrite arms leads to considerable irregularities in the surface. Additional materials that may be considered for use in the implant are listed in
  • the deployment of the implant is now described with reference to FIGs. 15a-15d.
  • the procedure starts with an introducer needle 33 puncturing through the annulus fibrosus 8, and into the nucleus pulposus 7, as shown in FIG. 15a.
  • a flexible wire implant 34 is pushed outwards from the introducer needle 33, as is shown in FIG. 15b.
  • the wire implant 34 slides along the inner wall 13 of the annulus fibrosus 8.
  • the wire implant 34 may be made in such a way that it does not rupture the inner wall 13, for example, it may be coated with a low friction coating, such as Teflon, or may be polished to achieve low friction.
  • At least one portion 36 of the wire implant 34 is made in a way and with a material as described above of this invention, so that it can be heated inductively.
  • the heatable portion 36 is positioned at the fissure 15 of the annulus fibrosus 8.
  • the wire implant 34 is pushed all the way out of the introducer needle 33 and the introducer needle 33 is removed from the spinal disc 1, as shown in FIG. 15c.
  • the implanted wire 34 is made out of nickel-titanium NiTi shape memory alloy.
  • the NiTi shape memory wire 34 is prepared in such a way, that when heated, it stretches out to form a loop with having a relatively large diameter.
  • the implant may stay in the disc and can be heated as needed to serve as a heating source for the procedure.
  • a typical procedure involves the temperature of the wire implant 34 being raised to a value in the range from 60 °C to 95 °C for 10 to 20 minutes.
  • the wire implant 34 typically has a diameter of 0.5 to 2.0 mm and a length of 30 to 100 mm.
  • the wire implant 34 may be looped several times within the annulus fibrosus 8.
  • the heatable portion 36 may extend over the whole wire implant 34, or may form part of the implant 34.
  • the wire implant 34 may have circular cross-section, although elliptical cross-sections, or cross-sections of other shapes may also be used.
  • the wire or the fissure adjacent parts of the wire implant may be coated with a medical drug supporting the healing of the fissure.
  • the temperature of the implant may be only raised to the point where the drug elutes out of the coating. When the temperature is lowered again, the drug elute or diffuse out of the coating, or elutes at a lower rate than at the elevated temperature.
  • the inductively produced heat may serve as a controlling mechanism for the elution process.
  • the present invention is applicable to systems and methods useful for relieving back pain.
  • the present invention should not be considered limited to the particular examples described above, but rather should be understood to cover all aspects of the invention as fairly set out in the attached claims.
  • Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification. The claims are intended to cover such modifications and devices.
  • annulus fibrosus 9 nucleus pulposus protruding posteriorly
  • inductor coil metallic finger like plates introducer needle implant wire distal tip of implant wire heating portion of the implant 34 proximal tip of the implant antenna inductive component of antenna, inductor capacitive component of antenna, capacitor(s) matching transformer oscillator
  • HV-RF high voltage radio frequency
  • HV-DC high voltage direct current
  • HV-AC high voltage alternating current

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  • Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Prostheses (AREA)

Abstract

Les douleurs dorsales sont dues, au moins en partie, au développement de fissures (15) dans l'anneau fibreux (8) du disque intervertébral. On traite ce disque en positionnant un implant (17) chauffable par induction à l'intérieur du noyau pulpeux (7) du disque (1), de préférence près de la paroi intérieure de l'anneau fibreux. Cet implant (17) est exposé à l'énergie RF et chauffé. La chaleur passe de l'implant chauffé à l'intérieur du disque, ce qui soulage le patient.
PCT/US2003/023330 2002-07-25 2003-07-25 Technique et dispositif de traitement de douleurs dorsales WO2004011092A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003256815A AU2003256815A1 (en) 2002-07-25 2003-07-25 Method and device to treat back pain

Applications Claiming Priority (2)

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US39849702P 2002-07-25 2002-07-25
US60/398,497 2002-07-25

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005032372A1 (de) * 2005-07-08 2006-10-19 Siemens Ag Neurokapsel

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WO1997022290A2 (fr) * 1995-12-16 1997-06-26 Cardiotools Herzchirurgietechnik Gmbh Installation de chauffage par induction pour implants metalliques inseres dans un organisme vivant
US6126682A (en) * 1996-08-13 2000-10-03 Oratec Interventions, Inc. Method for treating annular fissures in intervertebral discs
WO2001017611A1 (fr) * 1999-09-08 2001-03-15 European Institute Of Science Ab Dispositif a but therapeutique sur les tissus humains, destine a influencer des particules magnetiques injectees au moyen d'un champ electromagnetique alternatif a gradient
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EP0333381A2 (fr) * 1988-03-16 1989-09-20 Metcal Inc. Elément thermique pour le traitement de tumeurs
US5084002A (en) * 1988-08-04 1992-01-28 Omnitron International, Inc. Ultra-thin high dose iridium source for remote afterloader
US5197940A (en) * 1990-01-29 1993-03-30 Hypertherm Corp. Local application tumor treatment apparatus
US5468210A (en) * 1991-10-29 1995-11-21 Tanaka Kikinzoku Kogyo K.K. Process of thermal treatment in tissue
US5429583A (en) * 1993-12-09 1995-07-04 Pegasus Medical Technologies, Inc. Cobalt palladium seeds for thermal treatment of tumors
WO1997022290A2 (fr) * 1995-12-16 1997-06-26 Cardiotools Herzchirurgietechnik Gmbh Installation de chauffage par induction pour implants metalliques inseres dans un organisme vivant
US6126682A (en) * 1996-08-13 2000-10-03 Oratec Interventions, Inc. Method for treating annular fissures in intervertebral discs
US6238421B1 (en) * 1997-08-15 2001-05-29 GüNTHER ROLF. W. Induction heating device and method for metallic implants in living beings
WO2001017611A1 (fr) * 1999-09-08 2001-03-15 European Institute Of Science Ab Dispositif a but therapeutique sur les tissus humains, destine a influencer des particules magnetiques injectees au moyen d'un champ electromagnetique alternatif a gradient

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102005032372A1 (de) * 2005-07-08 2006-10-19 Siemens Ag Neurokapsel

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