BACKGROUND OF THE INVENTION  
         [0001]    This invention relates generally to percutaneous electrical therapy systems for medical use, such as for pain treatment. In particular, the invention relates to a percutaneous electrical therapy system providing sharp point protection.  
           [0002]    Electrical therapy has long been used in medicine to treat pain and other conditions. For example, transcutaneous electrical nerve stimulation (TENS) systems deliver electrical energy through electrode patches placed on the surface of a patient&#39;s skin to treat pain in tissue beneath and around the location of the patches. The efficacy of TENS systems in alleviating pain is questionable at best, however.  
           [0003]    More recently, a technique in which electrodes are placed through the patient&#39;s skin into the target tissue has been proposed. Percutaneous Neuromodulation Therapy (“PNT”) (also sometimes called Percutaneous Electrical Nerve Stimulation or “PENS”) using percutaneously placed electrodes achieves significantly better pain relief results than TENS treatments using skin surface electrodes. This therapy is described in Ghoname et al., “Percutaneous Electrical Nerve Stimulation for Low Back Pain,” JAMA 281:818-23 (1999); Ghoname et al., “The Effect of Stimulus Frequency on the Analgesic Response to Percutaneous Electrical Nerve Stimulation in Patients with Chronic Low Back Pain,” Anesth. Analg. 88:841-6 (1999); Ahmed et al., “Percutaneous Electrical Nerve Stimulation (PENS): A Complementary Therapy for the Management of Pain Secondary to Bony Metastasis,” Clinical Journal of Pain 14:320-3 (1998); and Ahmed et al, “Percutaneous Electrical Nerve Stimulation: An Alternative to Antiviral Drugs for Herpes Zoster,” Anesth. Analg. 87:911-4 (1998). The contents of these references are incorporated herein by reference.  
           [0004]    Thus far, PNT practitioners have used percutaneously placed acupuncture needles attached to waveform generators via cables and alligator clips to deliver the therapy to the patient. This arrangement and design of electrodes and generator is far from optimal. For example, the prior art has not addressed the issue of sharps protection for the patients&#39; caregivers and other bystanders. It is therefore an object of this invention to reduce the exposure of electrical therapy patients&#39; caregivers to accidental exposure to bloodborne pathogens, microbes, toxins, etc., via an injury caused by unintended contact with a sharp electrode.  
           [0005]    It is a further object of this invention to provide a percutaneous electrical therapy system having electrodes and electrode assemblies that are safe, efficacious, inexpensive and easy to use.  
           [0006]    Other objects of the invention will be apparent from the description of the preferred embodiments.  
         SUMMARY OF THE INVENTION  
         [0007]    The invention is a percutaneous electrical therapy system with sharp point protection. In a preferred embodiment, the system includes a control unit; an electrode assembly adapted to deliver electrical therapy to a patient, where the electrode assembly has an electrode electrically connectable to the control unit, the electrode having a sharp point at a distal end adapted to be inserted into the patient&#39;s tissue; and a sharp point protection assembly operable with the electrode assembly for reducing risk of unintended exposure to the electrode&#39;s point. In some embodiments, the sharp point protection assembly includes a housing to contain at least the sharp point of the electrode when the electrode is in an undeployed state. In some of these embodiments, the sharp point of the electrode may be outside of the housing in a deployed state, the housing being adapted to contain a portion of the electrode in the deployed state. The housing may also be adapted to contain at least the sharp point of the electrode after the electrode has changed from the deployed state to an undeployed state.  
           [0008]    In some embodiments, the sharp point protection assembly further has a locking assembly preventing relative movement between the electrode and the housing. The locking assembly may be a spring-biased detent. The system may also include a tool adapted to release the locking assembly and to move the sharp point of the electrode out of the housing. The tool may be further adapted to move the sharp point of the electrode back into the housing after having moved the sharp point of the electrode out of the housing and to engage the locking assembly to prevent further relative movement between the electrode and the housing.  
           [0009]    In some embodiments the electrode assembly has an actuator attached to a proximal end of the electrode, the actuator being disposed within and movable within the housing. The system may also include an actuator tool adapted to interact with the actuator to move the sharp point of the electrode out of the housing. The actuator tool may be further adapted to move the sharp point of the electrode back into the housing after having moved the sharp point of the electrode out of the housing. The actuator tool may also have an electrical contact adapted to make electrical communication between the electrode and the control unit.  
           [0010]    In some embodiments, the housing is adapted to contain none of the electrode when the electrode is in a deployed state in which the sharp point of the electrode has been inserted into the patient&#39;s tissue. The housing may be adapted to contain a plurality of electrodes. The system may also include an actuator adapted to move the electrode out of the housing. The housing may be adapted to contain a plurality of electrodes, the actuator being further adapted to move each electrode out of the housing one at a time.  
           [0011]    The electrode assembly further may also include a patch adapted to be placed on the patient&#39;s skin and to support the electrode in the deployed state. The patch may have an opening adapted to surround a portion of the electrode when the electrode is in the deployed state. The patch may also include an annular member disposed in the patch opening and adapted to engage a handle portion of the electrode. The annular member may have a raised portion disposed above the patch and adapted to engage an aperture of the housing.  
           [0012]    The system may also include an electrical connector attachable to the electrode handle portion to make electrical communication between the electrode and the control unit.  
           [0013]    In some embodiments, the housing is a first housing, with the sharp point protection assembly further including a second housing to contain at least the sharp point of the electrode when the electrode has moved from the deployed state to an undeployed state. The system may also include an actuator adapted to move the electrode into the second housing. The system may also include an electrode grasper adapted to grasp the electrode in response to movement of the actuator, such as a fork adapted to mate with a handle portion of the electrode. The second housing may also be adapted to contain at least the sharp points of a plurality of electrodes, with the actuator being optionally further adapted to move a plurality of electrodes into the second housing.  
           [0014]    In some embodiments, the sharp point protection assembly includes an aperture in the housing adapted to permit the electrode to pass through for deployment of the electrode.  
           [0015]    In some embodiments, the system further comprises a movable actuator adapted to move the sharp point of the electrode into the patient&#39;s tissue. The system may also include an actuator limit element limiting movement of the actuator and controlling depth of insertion of the sharp point of the electrode into the patient&#39;s tissue.  
           [0016]    In some embodiments, the system may also include an electrode insertion depth control mechanism.  
           [0017]    In some embodiments, the system may also include a deployed electrode holding mechanism adapted to hold the electrode in place after insertion of the sharp point of the electrode into the patient&#39;s tissue.  
           [0018]    In some embodiments, the system may also include an electrode insertion axial stabilizer adapted to provide axial stability to the electrode during insertion of the sharp point of the electrode into the patient&#39;s tissue.  
           [0019]    In some embodiments, the system may also include an electrode insertion pain reducer adapted to reduce pain experienced by the patient during insertion of the sharp point of the electrode into the patient&#39;s tissue.  
           [0020]    In some embodiments, the system may also include an electrode angle of entry controller adapted to control the electrode&#39;s entry angle during insertion of the sharp point of the electrode into the patient&#39;s tissue.  
           [0021]    The invention is also a method of performing percutaneous electrical therapy, the method including the steps of providing an electrode assembly having an electrode, the electrode having a sharp point at a distal end; inserting the sharp point of the electrode into a patient&#39;s tissue without exposing the sharp point to anyone but the patient; and applying an electrical signal to the electrode from a control unit. The method may include the step of removing the electrode from the patient&#39;s tissue without exposing the sharp point to anyone but the patient. The method may also include the step of making an electrical connection between the electrode and the control unit. The method may also include the step of, after the inserting step, supporting the electrode in the patient&#39;s tissue.  
           [0022]    In some embodiments, the inserting step includes the step of using the electrode assembly to guide electrode entry angle. In some embodiments, the inserting step includes the step of using an introducer to guide electrode entry angle. In some embodiments, the inserting step includes the step of providing axial stability to the electrode during insertion. In some embodiments, the inserting step includes the steps of placing a housing adjacent the patient&#39;s tissue; and moving the sharp point of the electrode out of the housing and into the patient&#39;s tissue. This method may also include the step of placing a patch on the patient&#39;s tissue prior to the step of placing a housing, in which the step of placing a housing includes the step of placing the housing adjacent the patch. In this method, the patch may have an opening, with the moving step including the step of moving the sharp point of the electrode out of the housing, through the opening and into the patient&#39;s tissue. The method may also include the step of mechanically supporting at least a portion of the electrode with the patch.  
           [0023]    In some embodiments of the method, the moving step includes the steps of moving the entire electrode out of the housing; and removing the housing from the patient&#39;s tissue. In some embodiments, the housing is a first housing, the method further including the step of removing the electrode from the patient&#39;s tissue into a second housing without exposing the sharp point to anyone but the patient.  
           [0024]    In some embodiments, the method includes the step of removing the electrode from the patient&#39;s tissue into the housing without exposing the sharp point to anyone but the patient.  
           [0025]    The invention also includes an electrode assembly and sharp point protection assembly for a percutaneous electrical therapy system as described above, apart from the control unit.  
           [0026]    The invention is described in further detail below with reference to the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]    FIGS.  1 A-G are schematic renderings of a percutaneous electrical therapy system according to one embodiment of this invention.  
         [0028]    [0028]FIG. 1A shows electrode and sharp point protection assemblies wherein the electrode is in an undeployed and uninserted state.  
         [0029]    [0029]FIG. 1B shows the electrode and sharp point protection assemblies of FIG. 1A during deployment but prior to insertion of the electrode into a patient&#39;s tissue.  
         [0030]    [0030]FIG. 1C shows the electrode and sharp point protection assemblies of FIG. 1A during deployment and insertion of the electrode into the patient&#39;s tissue.  
         [0031]    [0031]FIG. 1D shows the electrode of FIG. 1A inserted into the patient&#39;s tissue.  
         [0032]    [0032]FIG. 1E shows the electrode of FIG. 1A attached to a control unit to provide percutaneous electrical therapy.  
         [0033]    [0033]FIG. 1F shows the electrode and sharp point protection assemblies of FIG. 1A during undeployment but prior to removing the sharp point of the electrode from the patient&#39;s tissue.  
         [0034]    [0034]FIG. 1G shows the electrode and sharp point protection assemblies of FIG. 1A during undeployment and after removing the sharp point of the electrode from the patient&#39;s tissue.  
         [0035]    FIGS.  2 A-E are schematic renderings of a percutaneous electrical therapy system according to another embodiment of this invention.  
         [0036]    [0036]FIG. 2A shows a percutaneous electrical therapy system with electrode and sharp point protection assemblies wherein the electrode is in an undeployed and uninserted state.  
         [0037]    [0037]FIG. 2B shows the percutaneous electrical therapy system of FIG. 2A during deployment, but prior to insertion, of the electrode.  
         [0038]    [0038]FIG. 2C shows the percutaneous electrical therapy system of FIG. 2A with the electrode in a deployed and inserted state.  
         [0039]    [0039]FIG. 2D shows the percutaneous electrical therapy system of FIG. 2A during undeployment of the electrode.  
         [0040]    [0040]FIG. 2E shows the percutaneous electrical therapy system of FIG. 2A after the electrode has been undeployed.  
         [0041]    [0041]FIG. 3 shows an electrode montage for use in percutaneous neuromodulation therapy to treat low back pain.  
         [0042]    [0042]FIG. 4 is an exploded sectional view of an electrode and sharp point protection assembly according to yet another embodiment of this invention.  
         [0043]    [0043]FIG. 5 is a partially exploded elevational view of the embodiment of FIG. 4.  
         [0044]    [0044]FIG. 6 is an elevational view of the embodiment of FIG. 4 showing the electrode and sharp point protection assemblies and an actuator tool.  
         [0045]    [0045]FIG. 7 is a sectional view of the embodiment of FIG. 4 showing the electrode and sharp point protection assemblies and an actuator tool.  
         [0046]    [0046]FIG. 8 is a sectional view of the embodiment of FIG. 4 showing the actuator tool in engagement with the electrode and sharp point protection assemblies prior to insertion of the electrode into a patient&#39;s tissue.  
         [0047]    [0047]FIG. 9 is a sectional view of the embodiment of FIG. 4 with the electrode in its deployed and inserted state.  
         [0048]    [0048]FIG. 10 shows a montage for using the embodiment of FIG. 4 to treat low back pain with the electrodes in a partially deployed but uninserted state.  
         [0049]    [0049]FIG. 11 shows the electrode montage of FIG. 10 at the beginning of the electrode insertion step.  
         [0050]    [0050]FIG. 12 shows the electrode montage of FIG. 10 with the electrodes deployed, inserted and attached to a control unit to provide electrical therapy to the patient.  
         [0051]    [0051]FIG. 13 is an exploded view of an electrode introducer and sharp point protection assembly of yet another embodiment of this invention.  
         [0052]    [0052]FIG. 14 is a partial sectional view of the introducer and sharp point protection assembly of FIG. 13.  
         [0053]    [0053]FIG. 15 is a sectional view of the introducer and sharp point protection assembly of FIG. 13.  
         [0054]    [0054]FIG. 16 is an elevational view of gear assemblies of the introducer and sharp point protection assembly of FIG. 13.  
         [0055]    [0055]FIG. 17 shows part of the electrode assembly of the embodiment of FIGS.  13 - 16  in a montage used for treating low back pain using PNT.  
         [0056]    [0056]FIG. 18 is an elevational view showing the introducer of FIG. 13 in the process of deploying an electrode.  
         [0057]    [0057]FIG. 19 is a sectional view showing the introducer of FIG. 13 in the process of deploying an electrode, prior to insertion of the electrode.  
         [0058]    [0058]FIG. 20 is a sectional view showing the introducer of FIG. 13 in the process of deploying an electrode, during insertion of the electrode.  
         [0059]    [0059]FIG. 21 is a sectional view showing the introducer of FIG. 13 in the process of deploying an electrode, also during insertion of the electrode.  
         [0060]    [0060]FIG. 22 is a sectional view of an inserted electrode assembly of the embodiment of FIGS.  13 - 16 .  
         [0061]    [0061]FIG. 23 is a partial sectional view of an electrode remover and sharp point protection assembly according to yet another embodiment of the invention prior to removal of an electrode.  
         [0062]    [0062]FIG. 24 is a partial sectional view of the electrode remover and sharp point protection assembly of FIG. 23 partially actuated but prior to removal of an electrode.  
         [0063]    [0063]FIG. 25 is a partial sectional view of the electrode remover and sharp point protection assembly of FIG. 23 partially actuated but prior to removal of an electrode.  
         [0064]    [0064]FIG. 26 is a partial sectional view of the electrode remover and sharp point protection assembly of FIG. 23 partially actuated and engaged with an electrode but prior to removal of the electrode.  
         [0065]    [0065]FIG. 27 is a partial sectional view of the electrode remover and sharp point protection assembly of FIG. 23 during removal of an electrode.  
         [0066]    [0066]FIG. 28 is a partial sectional view of the electrode remover and sharp point protection assembly of FIG. 23 after removal of an electrode. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0067]    Percutaneous electrical therapy systems, such as PNT systems, deliver electric current to a region of a patient&#39;s tissue through electrodes that pierce the skin covering the tissue. The electric current is generated by a control unit external to the patient and typically has particular waveform characteristics such as frequency, amplitude and pulse width. Depending on the treatment or therapy being delivered, there may be one electrode containing both a cathode and an anode or a plurality of electrodes with at least one serving as a cathode and at least one serving as an anode.  
         [0068]    The electrode has a sharp point to facilitate insertion through the patient&#39;s skin and to enhance local current density during treatment. Once inserted into the skin, the sharp point may become exposed to pathogens, microbes, toxins, etc. in the patient&#39;s tissue and/or blood. After removal of the electrode from the patient&#39;s tissue, a caregiver or other bystander may be stuck accidentally with the sharp point of the electrode, thereby exposing the caregiver to any pathogens that may be on the used electrode. This invention therefore provides a sharp point protection assembly for a percutaneous electrical therapy system.  
         [0069]    FIGS.  1 A-G are block diagrams showing deployment and use of one embodiment of this percutaneous electrical therapy system and electrode assembly invention. As shown in FIGS. 1A and 1B, the system includes an electrode  1  having a sharp point  2  at its distal end and a sharp point protection assembly  3  surrounding at least the electrode&#39;s sharp point  2  when the electrode is in its undeployed and uninserted states. The undeployed and uninserted states include pre-deployment and post-deployment states of the electrode. In this embodiment, sharp point protection assembly  3  includes a housing  4  having an aperture  5  at its distal end. An actuator  6  interacts with a handle  11  at the proximal end of electrode  2  as shown.  
         [0070]    Deployment of the electrode assembly includes the steps taken to place the electrode assembly in proper position and condition for use in electrical therapy. FIG. 1A shows the electrode assembly in an undeployed (pre-deployed) state. During deployment, aperture  5  is placed against a patient&#39;s skin  22 , as shown in FIG. 1B. Electrode  2  is then inserted into the tissue underlying the patient&#39;s skin by moving actuator  6  distally, as shown in FIG. 1C. Actuator  6  may have an optional limit stop  9  element cooperating with a limit stop area  8  of housing  4  to limit distal motion of actuator  6  and to control the depth of insertion of sharp point  2  of electrode  1 . In a preferred embodiment of the invention, for example, where the electrical therapy system is used to provide percutaneous neuromodulation therapy, the predetermined electrode depth is 3 cm. Other electrode depths may be used, of course, depending on the intended application and therapy.  
         [0071]    After insertion, housing  4  and actuator  6  (which have heretofore acted as an electrode introducer) are preferably removed, as shown in FIG. 1D. Electrode  1  is connected to a control unit  10  via a conductor or cable  16 . For use with PNT, control unit  10  preferably supplies a current-regulated and current-balanced waveform with an amplitude of up to approximately 20 mA, frequency between approximately 4 Hz and 50 Hz, and pulse width of between approximately 50 μsec and 1 msec. Other electrical waveforms having other parameters may be used, of course, depending on the therapy to be provided. Also, while FIG. 1E shows only one electrode connected to the control unit, it should be understood that a plurality of electrodes may be connected to a single control unit, as called for by the desired electrical stimulation treatment.  
         [0072]    After completion of the electrical therapy, the electrode assembly is undeployed. During undeployment, the electrode must be removed from the patient in a sharps-safe manner. In this embodiment, as shown in FIG. 1F, the aperture  5  of the housing  4  of a sharp point protection assembly  3  is placed over the handle portion  11  of electrode  1 . Sharp point protection assembly  3  may be the same assembly used to deploy and insert the electrode (i.e., the electrode introducer), or it may be an entirely different assembly (e.g., an electrode remover). The sharp point  2  of electrode  1  is then drawn into housing  4  of sharp point protection assembly  3  by moving actuator  6  proximally, as shown in FIG. 1G. Thus, sharp point protection assembly  3  of FIGS.  1 A-G helps prevent all unintended contact between the electrode&#39;s sharp point and a caregiver or other bystander before, during and after deployment of the electrode.  
         [0073]    FIGS.  2 A-E are block diagrams of another embodiment of our percutaneous electrical therapy system and electrode assembly invention. A control unit  10  is connected to an electrode  12  within an electrode assembly  13  via a conductor  16 . As above, for use with PNT, control unit  10  preferably supplies a current-regulated and current-balanced waveform with an amplitude of up to approximately 20 mA, frequency between approximately 4 Hz and 50 Hz, and pulse width of between approximately 50 μsec and 1 msec. As shown in its undeployed state in FIG. 2A and in its uninserted stated in FIG. 2B, the system includes a sharp point protection assembly  14  comprising a housing  18  surrounding the sharp point  20  of electrode  12  when the electrode point  20  has not yet been inserted through the patient&#39;s skin  22 .  
         [0074]    To begin deployment, distal face  21  of housing  18  is place against the patient&#39;s skin  22 , as shown in FIG. 2B. The system may also include an electrode actuator  19  that enables deployment and insertion of the sharp point  20  of electrode  12  through the patient&#39;s skin  22  into the underlying tissue to a predetermined depth through an aperture  24  in housing  18 , as shown in FIG. 2C. Actuator  19  may be part of the electrode assembly  13  or a separate component of the system. Actuator may have an optional limit stop element  23  that cooperates with a limit stop area  17  of housing  18  to limit distal movement of actuator  19 , thereby controlling depth of insertion of electrode  12 . In a preferred embodiment of the invention, for example, where the electrical stimulation system is used to provide percutaneous neuromodulation therapy, the predetermined electrode depth is approximately 3 cm., although other electrode depths may be used depending on the application. The control unit  10  may then provide the appropriate therapy to the patient through electrode  12  and any other electrodes connected to it.  
         [0075]    During undeployment, actuator  19  is used to draw electrode  12  back proximally into housing  18 . After removal of the electrode from the patient&#39;s skin, housing  18  of sharp point protection assembly  14  once again surrounds the sharp point  20  of the now uninserted electrode  12 , as shown in FIGS. 2D and 2E. Actuator  19  helps enable this operation to occur without ever exposing the sharp point of the electrode when the sharp point is no longer in the patient. In fact, the operator of the electrode assembly never sees the sharp point of the electrode. Thus, sharp point protection assembly  14  shields the potentially contaminated portion of the undeployed electrode and protects the patient&#39;s caregiver or other bystander from unintended contact with the sharp point of the electrode before, during and after electrical therapy.  
         [0076]    While FIGS.  2 A-E show the electrode connected to the control unit prior to deployment and insertion of the electrode into the patient&#39;s skin, the connection between the control unit and the electrode could be made during deployment or after insertion. Also, while FIGS.  2 A-E show only one electrode connected to the control unit, it should be understood that a plurality of electrodes may be connected to a single control unit, as called for by the desired electrical stimulation treatment.  
         [0077]    To use the percutaneous electrical therapy systems of FIGS.  1 A-G and FIGS.  2 A-E to treat a patient, one or more electrodes are inserted through the patient&#39;s skin into the underlying tissue. As an example, to treat low back pain using PNT with unipolar electrodes, an array or montage such as that shown in FIG. 3 may be used. The “T12”-“S1” designations refer to the patient&#39;s vertebrae. The sharp point protection assembly shields the electrode assembly operator from exposure to the electrode&#39;s sharp point prior to, during and after treatment. The control unit or generator supplies current pulses between pairs of electrodes for durations of a few minutes to several hours, preferably delivering the current-regulated waveform described above. Thirty minute treatments are recommended in the Ghoname et al. low back pain treatment articles.  
         [0078]    During deployment and treatment, the electrode assembly and other parts of the system perform other functions in addition to being a sharps-protected conduit for current flow into the patient. For example, in the embodiment of FIGS.  2 A-E, aperture  24 , distal face  21  and the interaction of actuator  19  and housing  18  cooperate as an electrode angle of entry controller to control the electrode&#39;s entry angle during insertion of the sharp point of the electrode into the patient&#39;s tissue. The interaction of aperture  5 , distal face  7  of housing  4 , and the interaction of actuator  6  and housing  4  perform this function in the embodiment of FIGS.  1 A-G.  
         [0079]    Additional optional details of the electrode assembly may be found in the following concurrently filed and commonly owned U.S. patent applications, the disclosures of which are incorporated herein by reference: Bishay et al., “Percutaneous Electrical Therapy System With Electrode Entry Angle Control;” Leonard et al., “Percutaneous Electrical Therapy System Providing Electrode Axial Support;” Leonard et al, “Percutaneous Electrical Therapy System With Electrode Depth Control;” Leonard et al., “Percutaneous Electrical Therapy System With Electrode Position Maintenance;” Leonard et al., “Electrode Introducer For A Percutaneous Electrical Therapy System;” Bishay et al, “Percutaneous Electrical Therapy System For Minimizing Electrode Insertion Discomfort;” Bishay et al., “Electrode Assembly For A Percutaneous Electrical Therapy System;” and Leonard et al., “Electrode Remover For A Percutaneous Electrical Therapy System.” 
         [0080]    FIGS.  4 - 12  show another embodiment of this invention. An electrode assembly  30  includes a base  32 , an electrode  34 , and a plunger or actuator  36 . Base  32  has a flange or flared end  44  that is adapted to make contact with a patient&#39;s skin. Base  32  may be formed from any suitable polymer or metal, such as a high density polyethylene (HDPE). Base  32  is preferably opaque so that the electrode cannot be seen by a needle-shy patient.  
         [0081]    Actuator  36  fits within a housing portion  40  of base  32  in a slidable arrangement. A locking assembly is operable to prevent relative movement between actuator  36  and housing  40  of base  32 . In this embodiment, the locking assembly of actuator  36  has integrally-formed resilient detents  48  on its exterior cylindrical surface. In the undeployed state of electrode assembly  30 , detents  48  mate with a corresponding openings  50  in base  32  to hold actuator  36  and base  32  in place with respect to each other to prevent electrode  34  from moving outside of the protective housing  40  of base  32  and thereby providing sharp point protection, as explained further below. Mechanisms other than the detent and opening arrangement shown here may be used to hold the actuator and base in place may be used without departing from the invention.  
         [0082]    In this embodiment, electrode  34  is preferably a 3 cm. long  32  gauge stainless steel needle. Other sizes and materials may be used for electrode  34 , of course, without departing from the scope of the invention. Actuator  36  is preferably formed from HDPE as well, although other suitable materials may be used.  
         [0083]    Electrode  34  has a larger-diameter handle  52  at its proximal end. Handle  52  fits within a channel  54  formed within actuator  36 . Channel  54  has a narrow opening  56  at its distal end whose diameter is slightly larger than the diameter of electrode  34  but narrower than the diameter of handle  52  to hold electrode  34  in place within actuator  36  after initial manufacture and assembly. As shown in FIG. 7, in an undeployed state the sharp point  38  of electrode  34  is disposed within housing portion  40  of base  32 , specifically, within a narrow channel  42  of the housing  40 .  
         [0084]    To deploy one or more electrode assemblies on a patient in order to provide electrical stimulation therapy (such as PNT), the distal surface  46  of flange portion  44  of base  32  is mounted on the desired site on the patient&#39;s skin, preferably with a compressible adhesive pad (not shown) surrounding a ring  43  extending downward from surface  46  around an aperture  41  formed at the distal end of channel  42 , although other means of attaching base  32  to the patient may be used as appropriate.  
         [0085]    An electrical connector and actuator tool  60  is used to insert the electrode and connect the electrode electrically with a control unit  62 . Actuator tool  60  and electrode assembly  30  also interact to provide the sharp point protection assembly of this embodiment. When the distal end of actuator tool  60  is placed against the proximal ends of base  32  and actuator  36 , the exposed proximal end  64  of electrode handle  52  makes electrical contact with a contact surface  66  within actuator tool  60 . Contact surface  66 , in turn, is electrically connected to the control unit  62  via a cable or other conductor  68 .  
         [0086]    Actuator tool  60  has two oppositely disposed pegs  70  extending outward from the distal portion of its cylindrically surface. Pegs  70  mate with two corresponding slots  72  in actuator  36  and with two corresponding grooves  74  in base  32 . (The second slot  72  and second groove  74  are each opposite the slot  72  and groove  74 , respectively, shown in FIGS. 4 and 5.) When connecting actuator tool  60  to electrode assembly  30 , pegs  70  move along longitudinal portions  76  of slots  72  and along longitudinal portions  78  of grooves  74 . Concurrently, exposed distal end  64  of electrode handle  52  begins to make sliding contact with contact surface  66  of actuator tool  60  to create the electrical connection between actuator tool  60  and electrode  32 .  
         [0087]    Clockwise rotation (looking down on the assembly) of actuator tool  60  after pegs  70  reach the end of longitudinal portions  76  and  78  moves pegs  70  into short circumferential portions  80  and  82 , respectively, of slots  72  and grooves  74 . The length of circumferential portions  80  of slots  72  is less than the length of circumferential portions  82  of grooves  74 . Continued movement of pegs  70  along circumferential portions  82  will therefore move pegs  70  against the ends  81  of circumferential slots  80 . Further clockwise rotation of actuator tool  60  will cause actuator  36  to rotate clockwise as well, thereby moving detents  48  out of openings  50  and allowing the electrode  34  and actuator  36  to move with respect to base  32 .  
         [0088]    Second longitudinal portions  84  of grooves  74  are formed in base  32  at the end of circumferential portions  82 . Movement of pegs  70  distally along longitudinal portions  84  pushes pegs  70  against the distal edges of circumferential slot portions  80 , thereby moving actuator  36  and electrode  34  distally toward the patient&#39;s skin  22 .  
         [0089]    As it moves, electrode  34  passes through channel  42 , and the sharp point of electrode  34  moves out through aperture  41 . Channel  42  and actuator  36  provide axial support to electrode  34  during this forward movement and also, along with the support provided by flange  44 , provide entry angle guidance to the electrode. In addition, downward pressure on the patient&#39;s skin during electrode deployment compresses the compressible adhesive pad and presses ring  43  against the patient&#39;s skin  22 , which helps ease electrode entry through the skin and also lessens the insertion pain experienced by the patient.  
         [0090]    Distal movement of the electrode and its actuator within base  32  continues until the distal surface  86  of a cylindrical cap portion  92  of actuator tool  60  meets an annular surface  88  of housing  40 . At this point, sharp point  38  of electrode  34  has extended a predetermined depth into the tissue underlying the patient&#39;s skin. In the preferred embodiment, this predetermined depth is approximately 3 cm., although other electrode depths may be desired depending on the treatment to be performed.  
         [0091]    An optional feature of the invention is a deployed electrode holding mechanism. In this embodiment, an interference fit between the inner surface of channel  42  and the outer surface  55  of channel  52  performs this function.  
         [0092]    Electrical stimulation treatment may begin once the electrodes have been deployed and inserted. Control unit  62  supplies stimulation current to the electrodes, e.g. in the manner described in the Ghoname et al. articles. The electrical waveform provided by the control unit depends on the application. For example, in an embodiment of a system providing percutaneous neuromodulation therapy, control unit  62  would preferably provide a current-regulated and current-balanced waveform with an amplitude of up to approximately 20 mA, frequency between approximately 4 Hz and 50 Hz, and pulse width of between approximately 50 μsec and 1 msec.  
         [0093]    The interaction of actuator tool  60  and base  32  provides stability to electrode  34  and its electrical connection to the control unit during treatment by holding the electrode in place, by providing strain relief for tugging forces on cable  68 , and by providing a robust mechanical connection. It should be noted that the sharp point of the electrode is not exposed to the operator or to any other bystander at any point during deployment and use of the electrode assembly.  
         [0094]    After treatment has been completed, the electrode may be removed from the patient. To do so, actuator tool  60  is moved proximally away from the patient. As pegs  70  move proximally along longitudinal portions  84  of grooves  74 , pegs  70  push against proximal edges of the actuator&#39;s circumferential slot portions  80 , thereby moving actuator  36  and electrode  34  proximally as well. When pegs reach the proximal end of longitudinal groove portions  84 , the sharp end  38  of electrode  34  is out of the patient and safely inside housing  40  of base  32 . Counterclockwise movement of actuator tool  60  moves pegs along circumferential portions  80  and  82  of slot  72  and groove  74 , respectively. Since, as discussed above, circumferential portion  80  is shorter than circumferential portion  82 , this counterclockwise movement will turn actuator  36  counterclockwise.  
         [0095]    At the limit of the counterclockwise movement, detents  48  move back into openings  50  to prevent further movement of the electrode and actuator with respect to base  32 . Further distal movement of actuator tool  60  moves pegs  70  distally along longitudinal portions  76  and  78  of slot  72  and groove  74 , respectively, to disconnect actuator tool  60  from electrode assembly  30 . Base  32  can then be removed from the patient.  
         [0096]    Once again, at no time during the electrode deployment, use or removal processes was the sharp point of the electrode exposed to the operator or bystanders.  
         [0097]    FIGS.  10 - 12  show the use of the electrode and sharp point protection assemblies of FIGS.  4 - 9  to treat low back pain using PNT. As shown in FIG. 10, ten electrode assemblies  30   a - j  are arranged in a montage on the patient&#39;s back and attached with adhesive. Next, ten actuator tools  60   aj  are attached to the ten electrode assemblies  30   a - j . In this example, prior to deployment the actuator tools are mounted on an actuator tool tray  61  that provides electrical communication to a control unit  62  via cable  69 . The actuator tools electrically connect with tool tray  61 , and thereby to cable  69  and control unit  62 , via individual cables  68   aj . It should be understood that the tool tray  61  and its electrical connection scheme play no part in this invention. FIG. 11 shows the beginning of the electrode insertion process.  
         [0098]    Once each electrode assembly has been actuated by its respective actuator tool to insert an electrode into the patient&#39;s tissue (as shown in FIG. 12), control unit  62  provides electrical signals to treat the patient. Preferably, half the electrodes (e.g., assemblies  30   b ,  30   d ,  30   g ,  30   h  and  30   i ) are treated as anodes, and the other half as cathodes. In the preferred embodiment, control unit  62  would provide a current-regulated and current-balanced waveform with an amplitude of up to approximately 20 mA, frequency between approximately 4 Hz and 50 Hz, and pulse width of between approximately 50 μsec and 1 msec. to treat the patient&#39;s low back pain using PNT.  
         [0099]    Another embodiment of the invention is shown in FIGS.  13 - 28 . In this embodiment, an electrode introducer and an electrode remover cooperate to provide sharp point protection.  
         [0100]    A preferred embodiment of an electrode introducer  100  is shown in FIGS.  13 - 16  and  19 - 21 . In this embodiment, introducer  100  is designed to insert multiple electrodes. It should be understood that the principles of this invention could be applied to an introducer designed to hold and insert any number of electrodes.  
         [0101]    Twelve electrodes  102  are disposed within a magazine  103  rotatably mounted within a housing  104 . In this embodiment, housing  104  is a two-part injection molded polystyrene assembly. As seen best in FIG. 14, magazine  103  rotates about a hub  105  mounted on supports formed in housing  104 . A leaf spring  106  mates with one of twelve radial grooves  108  formed in magazine  103  to form a twelve-position ratchet mechanism for rotatable magazine  103  in housing  104 .  
         [0102]    Magazine  103  has twelve electrode chambers  115  arranged radially about hub  105 . When introducer  100  is completely full, each chamber  115  contains one electrode  102 . The diameter of upper portion  118  of chamber  115  is sized to form an interference fit with the wider portions  112  and  114  of electrode handle portion  107  of electrode  102 . Lower wide portion  114  of electrode  102  is formed from a compressible material. The diameter of lower portion  119  of chamber  115  is slightly larger so that there is no interference fit between chamber portion  119  and electrode handle  107 , for reasons explained below. Each time leaf spring  106  is within a groove  108 , the opening  106  of a magazine chamber  115  is lined up with the aperture  117  of introducer  100 , as shown in FIGS. 14 and 15.  
         [0103]    A slide member  109  is disposed on a rail  110  formed in housing  104 . Extending longitudinally downward from slide member  109  is a drive rod  111 , and extending longitudinally upward from slide member  109  is a gear rack  120 . The teeth of gear rack  120  cooperate with teeth on a rotational gear  122  mounted about a shaft  124  extending into a shaft mount  126  formed in housing  104 . A second set of teeth are mounted on a smaller diameter rotational gear  128  (shown more clearly in FIG. 16) which is also mounted about shaft  124 . Gears  122  and  128  rotate together about shaft  124 .  
         [0104]    The teeth of smaller diameter gear  128  mesh with the teeth of a second gear rack  130  extending from a longitudinally-movable actuator  132 . A spring  134  mounted between actuator  132  and a spring platform  136  biases actuator  132  away from housing  104 .  
         [0105]    To deploy the electrode assembly of this embodiment, a flexible and compressible annular patch  140  is placed on the patient&#39;s skin at the desired site, preferably with adhesive (not shown). For example, to treat low back pain using PNT, the arrangement or montage shown in FIG. 17 may be used. In this montage, five electrodes serve as cathodes and five serve as anodes.  
         [0106]    As shown in FIGS. 19 and 20, patch  140  has an annular rigid member  141  disposed in its center and extending upwardly from it. Rigid member  141  has a smaller diameter opening  142  leading to a larger diameter opening  144 . The diameter of opening  142  is slightly smaller than the lower wide portion  114  of the handle portion  107  of electrode  102  and slightly larger than the diameter of the central portion  113  of handle portion  107  of electrode  102 .  
         [0107]    After the patch  140  is in place, the distal end of introducer  100  is placed against patch  140  so that introducer aperture  117  surrounds the upwardly extending portion of rigid patch member  141 , as shown in FIG. 18. This interaction aligns the opening  116  of one of the introducer&#39;s magazine chambers  115  with the opening  142  of rigid member  141  and helps control the electrode&#39;s angle of entry, as shown in FIG. 19. Downward pressure on introducer  100  compresses patch  140 , thereby causing the upper surface of rigid member  141  to engage a lower surface of magazine  103  and pressing rigid member  141  downward into the patient&#39;s skin  22 . This pressure on the patient&#39;s skin around the insertion site minimizes the pain of insertion of the electrode.  
         [0108]    Depressing actuator  132  moves gear rack  130  distally, which causes gears  128  and  122  to rotate. Because of the relative diameters and relative tooth counts of gears  128  and  122 , gear rack  120  moves longitudinally a much greater distance than the corresponding longitudinal movement of gear rack  130 . This feature enables the electrode to be inserted its required distance into the patient&#39;s skin using only a comparatively small movement of the operator&#39;s thumb. Distal movement of gear rack  120  is guided by the movement of slide member  109  along rail  110 .  
         [0109]    As slide member  109  moves distally, drive rod  111  moves into a magazine chamber  115  until the distal end of drive rod  111  engages the top surface of the electrode&#39;s handle portion  107 . As shown in FIG. 20, further distal movement of drive rod  111  pushes electrode  102  downward so that sharp point  108  of electrode  102  leaves the introducer housing and enters the patient&#39;s skin  22  and the tissue beneath the skin. Chamber  115  provides axial stability to the electrode  102  during insertion.  
         [0110]    When the top portion  112  of electrode handle portion  107  leaves the smaller diameter portion  118  of magazine chamber  115 , it enters the larger diameter portion  119  of chamber  115 . At this point (shown in FIG. 21), because the diameter of chamber portion  119  is wider than the diameter of the electrode handle  107 , the electrode is no longer attached to introducer  100 .  
         [0111]    Continued downward movement of actuator  132  and drive rod  111  pushes the lower larger diameter portion  114  of electrode handle  107  through the smaller diameter portion  142  of rigid member  141  by compressing handle portion  114 . Further downward movement pushes handle portion  114  into the larger diameter portion  144  of rigid member  141  so that the rigid member&#39;s smaller diameter portion lies between the larger diameter portions  112  and  114  of the electrode handle  107 . This interaction holds the electrode in place in the patient&#39;s tissue and helps provides depth control for electrode insertion. In this embodiment, the preferred depth of the electrode&#39;s sharp point  108  is approximately 3 cm., although other electrode depths may be desired depending on the treatment to be performed. Slider member  109  also acts as a limit stop at this point when it engages the limit stop area  145  of housing  104 , thereby also controlling electrode insertion depth.  
         [0112]    Magazine  103  is rotated to a new insertion position and placed against an empty patch  140  after insertion of each electrode until all electrodes have been deployed and inserted. A suitable electrical connector  148  such as an alligator clip is electrically connected to electrode  102  through an aperture (not shown) formed in the upper larger diameter portion  112  of electrode handle  107  to provide electrical communication between a control unit  150  and electrode  102  via a cable or other conductor  149 , as shown in FIG. 22. Patch  140  provides strain relief for electrode  102  by preventing tugging forces on cable  149  from dislodging the electrode from the patient, thereby helping keep the electrode in place.  
         [0113]    Control unit  150  supplies stimulation current to the electrodes, e.g., in the manner described in the Ghoname et al. articles. Once again, the electrical waveform provided by the control unit depends on the application. For example, in an embodiment of a system providing percutaneous neuromodulation therapy, control unit  150  would preferably provide a current-regulated and current-balanced waveform with an amplitude of up to approximately 20 mA, frequency between approximately 4 Hz and 50 Hz, and pulse width of between approximately 50 μsec and 1 msec.  
         [0114]    It should be noted that at no time during the electrode deployment, insertion and electrical therapy treatment processes was the sharp point of the electrode exposed to the operator or bystanders.  
         [0115]    In an alternative embodiment, the lower wide portion of the electrode handle is formed from a rigid material and has rounded camming edges. The central annulus of patch  140  in this alternative embodiment is either compressible or has a resilient camming opening under the camming action of the electrode handle.  
         [0116]    FIGS.  23 - 28  show a sharps-safe remover according to one embodiment of this invention. Remover  200  is designed to work with the electrode and electrode patch assembly described with respect to FIGS.  13 - 22  above. It should be understood that the principles of sharps-safe remover  200  may apply to other electrode designs as well.  
         [0117]    Remover  200  has a housing  202  with an aperture  204  at its distal end. A number of previously undeployed electrodes  102  are stored within housing  202 . A pair of rails  214  and  216  hold the electrodes  102  in alignment via the electrode handles  107 , as shown. While this embodiment of the remover is designed to provide sharps-safe removal and storage of a plurality of electrodes, the invention applies to removers designed to remove and store one or any number of electrodes.  
         [0118]    As described above, electrodes for percutaneous electrical therapy are inserted through a patient&#39;s skin into underlying tissue with handle portions exposed above the skin. The first step in undeploying and removing an inserted electrode is to line up the exposed handle  107  of an electrode with the remover&#39;s aperture  204 , as shown in FIG. 23, by placing the distal face  205  of remover  200  against the patient&#39;s skin or against any portion of the electrode assembly (such as an adhesive patch) surrounding the electrode. While not shown in FIGS.  23 - 28 , aperture  204  is sized to surround an annular member (such as annular member  141  discussed above) holding an electrode handle of an electrode assembly (such as that shown in FIGS.  13 - 22  above), the sharp point of which has been inserted through a patient&#39;s skin.  
         [0119]    An electrode engagement fork  206  is pivotably attached to a longitudinally movable actuator  208  via an arm  209  and a hinged pivot  210 . A coil spring  212  biases actuator  208  upwards towards the actuator and fork position shown in FIG. 28. A leaf spring  218  extends from arm  209 . A cross-bar  220  at the end of leaf spring  218  slides in groove  222  and a corresponding groove (not shown) on the other side of housing  202 . Leaf spring  218  is in its relaxed state in the position shown in FIG. 23. In this position, a cross-bar  224  extending from the distal end of arm  209  adjacent fork  206  lies at the top of a camming member  226  and a corresponding camming member (not shown) on the other side of housing  202 .  
         [0120]    Downward movement of actuator  208  (in response, e.g., to pressure from a user&#39;s thumb) against the upward force of spring  212  moves cross-bar  224  against a first camming surface  228  of camming member  226 , as shown in FIG. 24. Camming surface  228  pushes cross-bar  224  of arm  209  against the action of leaf spring  218  as actuator  208 , arm  209  and fork  206  move downward.  
         [0121]    [0121]FIG. 25 shows the limit of the downward movement of fork  206 . At this point, crossbar  224  clears the camming member  226 , and leaf spring  218  rotates fork  206  and arm  209  about pivot  210  to engage fork  206  with electrode handle  107 , as shown in FIG. 26. The tine spacing of fork  206  is shorter than the diameter of the upper wide portion  112  of electrode handle  107  but wider than the diameter of the narrow middle portion  113  of electrode handle  107 .  
         [0122]    Release of actuator  208  by the user permits spring  212  to move actuator  208 , arm  209  and fork  206  proximally. The engagement between fork  206  and electrode handle  107  causes the electrode to begin to move proximally with the fork out of the patient and into the remover housing, as shown in FIG. 27. At this point, cross-bar  224  is now engaged with a second camming surface  230  of camming member  226 . Camming surface  230  pushes cross-bar  224  against the action of leaf spring  218  in the other direction (to the left in the view shown in FIG. 27) as the electrode, fork and arm rise under the action of coil spring  212 .  
         [0123]    The electrode and fork continue to rise until they reach the upward limit of their permitted motion, as shown in FIG. 28. At this point, electrode handle  107  has engaged rails  214  and  216  and the most recent electrode previously stored in remover  200 . Electrode handle  107  pushes against the electrode handle of the previously stored electrode handle, which in turn pushes against any electrode handles stored above it in the stack. In this manner, the latest electrode removed by remover  200  goes into the bottom of the stack of used electrodes stored in remover  200 . Now that the sharp point  108  of electrode  102  is safely inside housing  202 , remover  200  can be withdrawn from the site on the patient&#39;s skin through which the electrode had been inserted. Once cross-bar  224  clears the top of camming member  226 , and leaf spring  218  moves arm  209  back to the center position shown in FIG. 23.  
         [0124]    It should be noted that remover  200  provides sharp point protection for the entire electrode undeployment and removal process. Once all electrodes have been removed, the used electrodes can be safely transported in the sharps-safe container provided by the housing  202  of remover  200 .  
         [0125]    Modifications of the above embodiments of the invention will be apparent to those skilled in the art. For example, while the invention was described in the context of percutaneous electrical therapy in which electrodes are used to deliver electricity to a patient, the sharps-safe features may be used with electrodes designed for medical monitoring and/or diagnosis. In addition, the sharps-safe features of this invention may be used with acupuncture needles or other needles not used for conducting electricity to or from a patient.
The invention is a percutaneous electrical therapy system with sharp point protection. In a preferred embodiment, the system includes a control unit; an electrode assembly adapted to deliver electrical therapy to a patient, where the electrode assembly has an electrode electrically connectable to the control unit, the electrode having a sharp point at a distal end adapted to be inserted into the patient's tissue; and a sharp point protection assembly operable with the electrode assembly for reducing risk of unintended exposure to the electrode's point. The invention also includes an electrode assembly and sharp point protection assembly for a percutaneous electrical therapy system as described above, apart from the control unit. The invention is also a method of performing percutaneous electrical therapy, the method including the steps of providing an electrode assembly having an electrode, the electrode having a sharp point at a distal end; inserting the sharp point of the electrode into a patient's tissue without exposing the sharp point to anyone but the patient; and applying an electrical signal to the electrode from a control unit.