Abstract:
Improved assemblies, systems, and methods provide safeguarding against nerve injury during surgical procedures and/or identify nerve damage occurring prior to surgery and/or verify range of motion or attributes of muscle contraction during reconstructive surgery. A stimulation control device may incorporate a range of low and high intensity stimulation to provide a stimulation and evaluation of both nerves and muscles. A stimulation control device is removably coupled to a surgical device or is imbedded within the medical device to provide a stimulation and treatment medical device.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/657,277, filed Mar. 1, 2005, and entitled “Systems and Methods for Intra-Operative Stimulation” which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates generally to nerve and muscle identification and integrity testing, and more particularly to systems and methods for safeguarding against nerve and muscle injury during surgical procedures, identification and assessment of nerve and muscle integrity following traumatic injuries, and verification of range of motion and attributes of muscle contraction during reconstructive surgery.  
       BACKGROUND OF THE INVENTION  
       [0003]     Even with today&#39;s sophisticated medical devices, surgical procedures are not risk-free. Each patient&#39;s anatomy differs, requiring the surgeon to be ever vigilant to these differences so that the intended result is accomplished. The positioning of nerves and other tissues within a human or animal&#39;s body is one example of how internal anatomy differs from patient to patient. While these differences may be slight, if the surgeon fails to properly identify one or several nerves, the nerves may be bruised, stretched, or even severed during an operation. The negative effects of nerve damage can range from lack of feeling on that part of the body to loss of muscle control.  
         [0004]     Traumatic injuries often require surgical repair. Determining the extent of muscle and nerve injury is not always possible using visual inspection. Use of an intra-operative stimulator enables accurate evaluation of the neuromuscular system in that area. This evaluation provides valuable knowledge to guide repair/reconstructive surgery following traumatic injury, and when performing a wide range of surgeries.  
       SUMMARY OF THE INVENTION  
       [0005]     The invention provides devices, systems, and methods for intra-operative stimulation. The intra-operative stimulation enables accurate evaluation of the neuromuscular system to guide repair or reconstructive surgery.  
         [0006]     One aspect of the invention provides devices, systems, and methods comprising a tissue stimulation system comprising a housing, such as a tubular shaped housing, having a proximal end and a distal end, an operative element having an electrically conductive surface sized and configured for electrical stimulation of a targeted tissue region, the operative element extending from the distal end of the housing, and wherein the electrical stimulation is in the form of a signal having an amplitude and a duration for providing a first indication to the user of close proximity of the operative element to the targeted tissue region, and a stimulation control device electrically coupled to the operative element, the stimulation control device comprising stimulation signal generating circuitry. The housing may include a first control device for turning the stimulation signal to the operative element on and off and for providing adjustment of the stimulation signal amplitude, the first control device being electrically coupled to the stimulation control device. The housing may also include a second control device for providing adjustment of the stimulation signal duration, the second control device being electrically coupled to the stimulation control device.  
         [0007]     Additional aspects of the invention provide a tissue stimulation system that may be sterilized and prepackaged for single use. The stimulation signal of the tissue stimulation system includes an amplitude that may range between about zero milliamps and about 20 milliamps, allowing for accurate selective stimulation of both muscles and nerves, and also identification of nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions. The tissue stimulation signal duration may include a range between about zero microseconds and about 200 microseconds, for example. The first indication provided by the tissue stimulation system may include, for example, audio and visual indications. The tissue stimulation system may further include a second indication means to provide confirmation of power on to the device and delivery of a stimulation signal to the electrically conductive surface. The operative element of the tissue stimulation system may comprise a probe, for example, where the electrically conductive surface of the probe comprises between about 1 millimeter and about 10 millimeters of the distal end of the probe, and the probe comprises a diameter between about 0.5 millimeters and about 1 millimeter. The tissue stimulation system may also further include a return electrode electrically coupled to the stimulation control device.  
         [0008]     Additional aspects of the invention provide a tissue stimulation system, such as a medical device comprising a housing having a proximal end and a distal end, the housing sized and configured to be held by a user, a probe having an electrically conductive surface sized and configured for electrical stimulation of a targeted tissue region, the probe extending from the distal end of the housing, and wherein the electrical stimulation is in the form of a signal having an amplitude and a duration for providing a physical motor response, a stimulation control device electrically coupled to the probe and sized and configured to be positioned within the housing, the stimulation control device comprising stimulation signal generating circuitry. The housing may include a first control device for turning the stimulation signal to the probe on and off and for providing adjustment of the stimulation signal amplitude, the first control device being electrically coupled to the stimulation control device. The housing may also include a second control device for providing adjustment of the stimulation signal duration, the second control device being electrically coupled to the stimulation control device.  
         [0009]     According to another aspect of the invention, a stimulation control device electrically coupled to at least one surgical tool, which can comprise, e.g., a cutting, grasping, drilling, screwing, and/or viewing tool. The application of stimulation voltage or current to the device allows the clinician to observe muscle contraction or changes in the nervous system response when the surgical tool is in close proximity to viable nerve or muscle tissue. The surgical tool thus becomes a neural/muscular stimulating electrode. In use, different surgical tools, individually deployed in association with different medical procedures, can make use of a singe, stimulation control device, to which a selected surgical tool can be temporarily coupled for use.  
         [0010]     According to yet another aspect of the invention, the stimulation control device may be embedded within the surgical tool to provide a medical device capable of providing stimulation, as described above.  
         [0011]     Another aspect of the invention provides devices, systems, and methods comprising a stimulation monitor or probe and at least one electrode. In one embodiment, a hand held stimulation probe or monitor includes the stimulation control device and at least one stimulation electrode within a unified housing to provide an ergonomic stimulation device. The hand held stimulation probe can be a sterile, single use instrument intended for use during surgical procedures to identify nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions or the need for surgical interventions, or to evaluate the function of nerves already identified through visual or audible means, or by other nervous system monitoring instruments.  
         [0012]     Additional aspects of the invention provide a stimulation control device electrically coupled to a tissue cutting instrument, or a stimulation control device electrically coupled to a drilling instrument, or a stimulation control device electrically coupled to a pilot auger for hard surface rotary probing prior to pilot hole drilling, or a stimulation control device electrically coupled to a fixation device, which is commonly used in spinal stabilization procedures and internal bone fixation procedures.  
         [0013]     Features and advantages of the inventions are set forth in the following Description and Drawings, as well as the appended description of technical features. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a diagrammatic view of a system usable in association with a family of different monitoring and treatment devices for use in different medical procedures.  
         [0015]      FIG. 2  is a perspective view showing an exemplary embodiment of the system shown in  FIG. 1 , the stimulation control device being removably coupled to a stimulation probe, and showing the stimulation signal path through the system.  
         [0016]      FIG. 3A  is a perspective view showing the stimulation control device in use with a stimulation probe.  
         [0017]      FIG. 3B  is a perspective view with a portion broken away and in section showing the stimulation probe having the stimulation control device embedded within the stimulation probe, and showing an optional needle-like return electrode.  
         [0018]      FIG. 4  is a block diagram of a circuit that the stimulation control device shown throughout the Figs. can incorporate.  
         [0019]      FIGS. 5A and 5B  are perspective views showing the stimulation control device in use with a cutting device.  
         [0020]      FIGS. 6A &amp; 6B  are perspective views showing the stimulation control device in use with a drilling or screwing device.  
         [0021]      FIGS. 7A &amp; 7B  are perspective views showing the stimulation control device in use with a pilot auger device.  
         [0022]      FIGS. 8A and 8B  are perspective views showing the stimulation control device in use with a fixation device.  
         [0023]      FIG. 9  is a view showing how the geometry of the stimulation control device shown in  FIG. 2  aids in its positioning during a surgical procedure. 
     
    
       [0024]     The invention may be embodied in several forms without departing from its spirit or essential characteristics. The scope of the invention is defined in the appended claims, rather than in the specific description preceding them. All embodiments that fall within the meaning and range of equivalency of the claims are therefore intended to be embraced by the claims.  
       DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0025]     This Specification discloses various systems and methods for safeguarding against nerve, muscle, and tendon injury during surgical procedures or confirming the identity of nerves, muscles, and tendons and evaluating their function or the function of muscles enervated by those nerves. The systems and methods are particularly well suited for assisting surgeons in identification of nerves and muscles in order to assure nerve and muscle integrity during medical procedures using medical devices such as stimulation monitors, cutting, drilling, and screwing devices, pilot augers, and fixation devices. For this reason, the systems and methods will be described in the context of these medical devices.  
         [0026]     The systems and methods desirably allow the application of a stimulation signal at sufficiently high levels for the purpose of stimulating and evaluating nerve or muscle, or both nerve and muscle integrity in numerous medical procedures, including, but not limited to, evaluating proximity to a targeted tissue region, evaluating proximity to a nerve or to identify nerve tissue, evaluating if a nerve is intact (i.e., following a traumatic injury) to determine if a repair may be needed, evaluating muscle contraction to determine whether or not the muscle is innervated and/or whether the muscle is intact and/or whether the muscle is severed, and evaluating muscle and tendon length and function following a repair or tendon transfer prior to completing a surgical procedure.  
         [0027]     Still, it should be appreciated that the disclosed systems and methods are applicable for use in a wide variety of medical procedures with a wide variety of medical devices. By way of non-limiting example, the various aspects of the invention have application in procedures requiring grasping medical devices and internal viewing devices as well.  
         [0000]     I. Overview of the System  
         [0028]      FIG. 1  shows an illustrative system  20  for safeguarding against nerve injury during surgical procedures. In the illustrated embodiment, the system  20  is configured for monitoring and stimulating nerves and other structures throughout the body. The system  20  includes a stimulation control device  22  operating individually or in conjunction with one or more of a family of stimulating medical devices including, for example, a stimulation monitor or probe  100 , a cutting device  200 , a drilling or screwing device  300 , a pilot auger  400 , and a fixation device  500 .  
         [0029]     In an exemplary embodiment, and as can be seen in  FIG. 2 , the stimulation control device  22  functions in the system  20  to generate an electrical stimulation signal  29 . The stimulation signal  29  flows from the stimulation control device  22  through a lead  24  to a medical device (e.g., stimulation probe  100 ). The stimulation signal  29  then flows through a predefined insulated path  124  within the stimulation probe  100  and to an operative element, such as an electrically conductive surface, i.e., a coupled electrode  110 . The electrode is to be positioned on or near a region of a patient to be stimulated. In monopolar operation, a return electrode (or indifferent electrode)  38  provides an electrical path from the body back to the control device  22 . The stimulation control device  22  may operate in a monopolar or bipolar configuration, as will be described in greater detail later.  
         [0030]     The stimulation signal  29  is adapted to provide an indication. The indication may include a physical motor response (e.g., twitching), and/or a visual or audio signal from the stimulation control device  22 , which indicate to the surgeon close proximity of the electrode  110  to a nerve, or a muscle, or a nerve and a muscle. The stimulation control device may also indicate to the surgeon that the stimulation control device is operating properly and delivering a stimulus current.  
         [0000]     II. Medical Devices  
         [0031]     The configuration of the stimulating medical devices that form a part of the system can vary in form and function. Various representative embodiments of illustrative medical devices will be described.  
         [0032]     A. Stimulation Probe  
         [0033]      FIGS. 3A and 3B  show various embodiments of a hand held stimulation monitor or probe  100  for identification and testing of nerves and/or muscles during surgical procedures. The stimulation probe  100  is preferably a sterile, single use instrument intended for use during surgical procedures to identify nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions or the need for surgical interventions, or to evaluate the function of nerves already identified through visual means.  
         [0034]     The stimulation probe is preferably sized small enough to be held and used by one hand during surgical procedures. The angle of the stimulating tip facilitates access to deep as well as superficial structures without the need for a large incision. A visual or audio indicator  126  incorporated in the housing provides reliable feedback to the surgeon as to the request and delivery of stimulus current.  
         [0035]     In one embodiment, the stimulation probe  100  includes a housing  112  that carries an insulated lead  124 . The insulated lead  124  connects to an electrode  110  positioned at the housing&#39;s proximal end  114 . The lead  124  within the housing  112  is insulated from the housing  112  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). The electrode  110  is positioned in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve.  
         [0036]     In an additional embodiment, the stimulation probe  100  is mono-polar and is equipped with a single electrode  110  at the housing proximal end  114 . Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. In an alternative embodiment, the stimulation device  100  itself may be bipolar, which precludes the use of the return electrode  38 .  
         [0037]     As shown in  FIGS. 3A and 3B , the stimulation probe  100  may accommodate within the housing  112  the electrical circuitry of a stimulation control device  22 . In this arrangement, the stimulation probe  100  may have two operational slide controls,  155  and  160 . Power switch  155  serves a dual purpose of turning the stimulation signal to the probe  100  on and off, and also can be stepped to control the stimulation signal amplitude selection within a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch  160  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., 0 through 200 microseconds).  
         [0038]     An operative element, such as a stimulus probe  110 , exits the housing at the proximal end  114  to deliver stimulus current to the excitable tissue. The probe or electrode  110  comprises a length and a diameter, and is desirably fully insulated with the exception of the most distal end, e.g. about 1.0 millimeters to about 10 millimeters, and desirably about 4 millimeters to about 6 millimeters, which is non-insulated and serves as the stimulating surface to allow the surgeon to deliver the stimulus current only to the intended tissue. The small area of the probe (the active electrode) ensures a high current density that will stimulate nearby excitable tissue. The probe diameter may range between about 0.5 millimeters to about 1.0 millimeters, and may be desirably about 0.75 millimeters.  
         [0039]     In monopolar operation, a return electrode (or indifferent electrode)  130  provides an electrical path from the body back to the control device  22 . The return electrode  130  may be placed on the surface of intact skin (e.g., surface electrodes as used for ECG monitoring during surgical procedures) or it might be needle-like  131  (see  FIG. 3B ), and be placed in the surgical field or penetrate through intact skin. The housing&#39;s distal end  118  can incorporate a connector or jack  120  which provides options for return current pathways, such as through a surface electrode  130  or a needle electrode  131 , having an associated plug  122 .  
         [0040]     Additionally, the device  100  may desirably incorporate a visual or audio indicator  126  for the surgeon. This visual or audio indicator  126  allows the surgeon to confirm that the stimulator  100  is delivering stimulus current to the tissue it is contacting. Through the use of different tones, colors, different flash rates, etc., the indicator  126  (which can take the form, e.g., of a light emitting diode—LED) allows the surgeon to confirm that the stimulating tip  110  is in place, the instrument is turned ON, and that stimulus current is flowing. Thus the surgeon has a much greater confidence that the failure to elicit a muscle contraction is because of lack of viable nervous tissue near the tip of the stimulator  100  rather than the failure of the return electrode connection or some other instrumentation problem.  
         [0041]     Audio feedback also makes possible the feature of assisting the surgeon with monitoring nerve integrity during surgery. The insulated lead  124  connects to an electrode  110  that, in use, is positioned within the surgical field on a nerve distal to the surgical site. Stimulation of the nerve causes muscle contraction distally. The stimulation control device  22  may be programmed to provide an audio tone followed by a stimulation pulse at prescribed intervals. The audio tone reminds the surgeon to observe the distal muscle contraction to confirm upon stimulation that the nerve is functioning and intact.  
         [0042]     Alternatively, as  FIG. 2  shows, the stimulation control device  22  may be housed in a separate case, with its own input/output (I/O) controls  26 . In this alternative arrangement, the stimulation control device  22  is sized small enough to be easily removably fastened to a surgeon&#39;s arm or wrist during the surgical procedure, or otherwise positioned in close proximity to the surgical location (as shown in  FIG. 9 ), to provide sufficient audio and visual feedback to the surgeon. In this arrangement, the separate stimulation control device  22  can be temporarily coupled by a lead to a family of various medical devices for use.  
         [0043]     The present invention includes a method of locating a nerve in a patient that comprises the steps of providing a hand-held stimulation probe  100  as set forth above, engaging a patient with the first electrode  110  and the second electrode  130 , moving the power switch  155  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  110 , through the patient&#39;s body to the second electrode  130 , and back to the stimulation control device  22 .  
         [0044]     B. The Stimulation Control Device  
         [0045]     As  FIG. 4  shows, the stimulation control device  22  includes a circuit  32  that generates electrical stimulation waveforms. A battery  34  internal to the stimulator  100  desirably provides the power. The pulse generator  28  also desirably includes an on-board, programmable microprocessor  36 , which carries embedded code. The code expresses pre-programmed rules or algorithms for generating the desired electrical stimulation waveforms using the stimulus output circuit  46  and for operating the visible or audible indicator  126  based on the controls actuated by the surgeon.  
         [0046]     In one form, the size and configuration of the stimulation control device  22  makes for an inexpensive device, which is without manual internal circuit adjustments. It is likely that the stimulation control device  22  of this type will be fabricated using automated circuit board assembly equipment and methods.  
         [0047]     C. Incorporation with Surgical Devices  
         [0048]     A stimulation control device  22  as just described may be electrically coupled through a lead, or embedded within various devices commonly used in surgical procedures.  
         [0049]     1. Cutting Device  
         [0050]     In  FIGS. 5A and 5B , a device  200  is shown that incorporates all the features disclosed in the description of the stimulation probe  100 , except the device  200  comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 5A  shows the tool to be a cutting device  200  (e.g., scalpel) removably coupled to a stimulation control device  22 .  
         [0051]     In the embodiment shown, the cutting device  200  includes a body  212  that carries an insulated lead  224 . The insulated lead  224  connects to an operative element, such as electrode  210 , positioned at the body proximal end  214  and a plug-in receptacle  219  at the body distal end  118 . The lead  224  within the body  212  is insulated from the body  212  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like).  
         [0052]     In this embodiment, the electrode  210  performs the cutting feature (e.g., knife or razor). The electrode  210  performs the cutting feature in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve. The cutting device  200  preferably includes a plug-in receptacle  216  for the electrode  210 , allowing for use of a variety of cutting electrode shapes and types (e.g., knife, razor, pointed, blunt, curved), depending on the specific surgical procedure being performed. In this configuration, the lead  224  electrically connects the electrode  210  to the stimulation control device  22  through plug-in receptacle  219  and lead  24 .  
         [0053]     In one embodiment, the cutting device  200  is mono-polar and is equipped with a single electrode  210  at the body proximal end  214 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the cutting device  200  may be bipolar, which precludes the use of the return electrode  38 .  
         [0054]     In the embodiment shown in  FIG. 5B , the cutting device  200  accommodates within the body  212  the electrical circuitry of the stimulation control device  22 . In this arrangement, the cutting device  200  may have at least two operational slide controls,  255  and  260 . Power switch  255  serves a dual purpose of turning the stimulation signal to the cutting device  200  on and off, and also is stepped to control the stimulation signal amplitude selection from a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch  260  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., 0 through 200 microseconds).  
         [0055]     At the body distal end  218 , a second plug-in receptacle  220  may be positioned for receipt of a second lead  222 . Lead  222  connects to electrode  230  which functions as a return path for the stimulation signal when the cutting device  200  is operated in a mono-polar mode.  
         [0056]     Additionally, the device  200  may incorporate a visual or audio indicator for the surgeon, as previously described.  
         [0057]     The present invention includes a method of locating a nerve in a patient that comprises the steps of providing cutting device  200  as set forth above, engaging a patient with the first electrode  210  and the second electrode  230 , moving the power switch  255  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  210 , through the patient&#39;s body to the second electrode  230 , and back to the stimulation control device  22 .  
         [0058]     2. Drilling Device  
         [0059]     In  FIGS. 6A and 6B , a device  300  is shown that incorporates all the features disclosed in the description of the stimulation probe  100 , except the device  300  comprises the additional feature of providing an “energized” surgical device or tool, which comprises a drilling device  300 . In  FIG. 6A  is drilling device  300  is removably coupled to a stimulation control device  22 .  
         [0060]     In the embodiment shown, the drilling device  300  includes a body  312  that carries an insulated lead  324 . The insulated lead  324  connects to an operative element, such as electrode  310 , positioned at the body proximal end  314  and a plug-in receptacle  319  at the body distal end  318 . The lead  324  within the body  312  is insulated from the body  312  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like).  
         [0061]     In this embodiment, the electrode  310  performs the drilling feature. The electrode  310  may also perform a screwing feature as well. The electrode  310  performs the drilling feature in electrical conductive contact with a hard structure (e.g., bone).  
         [0062]     The drilling device  300  preferably includes a plug-in receptacle or chuck  316  for the electrode  310 , allowing for use of a variety of drilling and screwing electrode shapes and sizes (e.g., ¼ and ⅜ inch drill bits, Phillips and flat slot screw drivers), depending on the specific surgical procedure being performed. In this configuration, the lead  324  electrically connects the electrode  310  to the stimulation control device  22  through plug-in receptacle  319  and lead  324 .  
         [0063]     In one embodiment, the drilling device  300  is mono-polar and is equipped with a single electrode  310  at the body proximal end  314 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the drilling device  300  may be bipolar, which precludes the use of the return electrode  38 .  
         [0064]     In  FIG. 6B , the drilling device  300  is shown to accommodate within the body  312  the electrical circuitry of the stimulation control device  22 . The drilling device  300  may have at least two operational slide controls,  355  and  360 . Power switch  355  serves a dual purpose of turning the stimulation signal to the drilling device  300  on and off, and also is also stepped to control the stimulation signal amplitude selection from a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch  360  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., 0 through 200 microseconds). At the body distal end  318 , a second plug-in receptacle  320  may be positioned for receipt of a second lead  322 . Lead  322  connects to electrode  330  which functions as a return path for the stimulation signal when the drilling device  300  is operated in a mono-polar mode.  
         [0065]     Additionally, the device  300  may incorporate a visual or audio indicator for the surgeon, as previously described.  
         [0066]     The present invention includes a method of locating a nerve in a patient that comprises the steps of providing a drilling device  300  as set forth above, engaging a patient with the first electrode  310  and the second electrode  330 , moving the power switch  355  to an activation position causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  310 , through the patient&#39;s body to the second electrode  330 , and back to the stimulation control device  22 .  
         [0067]     3. Pilot Auger  
         [0068]     An additional aspect of the invention provides systems and methods for controlling operation of a family of stimulating devices comprising a stimulation control device electrically coupled to a pilot auger for hard surface rotary probing.  
         [0069]     This embodiment incorporates all the features disclosed in the description of the stimulation probe  100 , except this embodiment comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 7A  shows a pilot auger device  400  removably coupled to a stimulation control device  22 . In the embodiment shown, the pilot auger device  400  includes a body  412  that carries an insulated lead  424 . The insulated lead  424  connects to an operative element, such as an electrode  410 , positioned at the body proximal end  414  and a plug-in receptacle  419  at the body distal end  418 . The lead  424  within the body  412  is insulated from the body  412  using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like). In this embodiment, the electrode  410  performs the pilot augering feature. The electrode  410  performs the pilot augering feature in electrical conductive contact with a hard structure (e.g., bone). The pilot auger device  400  preferably includes a plug-in receptacle or chuck  416  for the electrode  410 , allowing for use of a variety of pilot augering electrode shapes and sizes (e.g., 1/32, 1/16, and ⅛ inch), depending on the specific surgical procedure being performed. In this configuration, the lead  24  electrically connects the electrode  410  to the stimulation control device  22  through plug-in receptacle  419  and lead  24 .  
         [0070]     In one embodiment, the pilot auger device  400  is mono-polar and is equipped with a single electrode  410  at the body proximal end  414 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the pilot auger device  400  may be bipolar, which precludes the use of the return electrode  38 .  
         [0071]     As  FIG. 7B  shows. the pilot auger device  400  may accommodate within the body  412  the electrical circuitry of the stimulation control device  22 . At the body distal end  418 , a second plug-in receptacle  420  may be positioned for receipt of a second lead  422 . Lead  422  connects to electrode  430  which functions as a return path for the stimulation signal when the pilot auger device  400  is operated in a mono-polar mode.  
         [0072]     The pilot auger device  400  includes a power switch  455 . When moved to an activation position, a stimulation signal is generated by the stimulation control device  22 . Additionally, the device  400  may incorporate a visual or audio indicator for the surgeon, as previously described.  
         [0073]     The present invention includes a method of locating a nerve in a patient that comprises the steps of providing a pilot auger device  400  as set forth above, engaging a patient with the first electrode  410  and the second electrode  430 , moving the power switch  455  to an activation position causing a stimulation signal to be generated by the stimulation control device  22  and transmitted to the first electrode  410 , through the patient&#39;s body to the second electrode  430 , and back to the stimulation control device  22 .  
         [0074]     D. Incorporation with Fixation Devices  
         [0075]     An additional aspect of the invention provides systems and methods for controlling operation of a family of stimulating devices comprising a stimulation control device electrically coupled to a fixation device or a wrench or screwdriver for placing the fixation device. A fixation device (e.g., orthopedic hardware, pedicle screws) is commonly used during spinal stabilization procedures (fusion), and internal bone fixation procedures.  
         [0076]     This embodiment incorporates all the features disclosed in the description of the stimulation probe  100 , except this embodiment comprises the additional feature of providing an “energized” fixation device or tool.  FIG. 8A  shows a fixation device  500  removably coupled to a stimulation control device  22 . In the embodiment shown, the fixation device  500  includes a rectangularly shaped body  512  that also serves as an operative element, such as electrode  510 . The fixation device  500  may take on an unlimited number of shapes as necessary for the particular procedure taking place. Pedicle screws  535  may be used to secure the fixation device to the bony structure. The electrode  510  performs the fixation feature in electrical conductive contact with a hard structure (e.g., bone). The fixation device  500  or wrench or screwdriver for placing the fixation device preferably includes a plug-in receptacle  519 . The fixation device  500  may take on an unlimited variety of shapes and sizes depending on the specific surgical procedure being performed. In this configuration, the lead  24  electrically connects the electrode  510  to the stimulation control device  22  through plug-in receptacle  519 .  
         [0077]     In one embodiment, the fixation device  500  is mono-polar and is equipped with the single electrode  510 . In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. The return electrode  38  may be attached to the stimulation device  22  by way of a connector or plug-in receptacle  39 . In an alternative embodiment, the fixation device  500  may be bipolar, which precludes the use of the return electrode  38 .  
         [0078]     In yet an additional alternative embodiment (see  FIG. 8B ), the fixation device may be a pedicle screw  535 . The pedicle screw  535  is removably coupled to a stimulation control device  22 . In the embodiment shown, the pedicle screw  535  includes a head  570  and a shaft  572 , which both serve as an operative element, such as electrode  574 . The electrode  574  performs the fixation feature in electrical conductive contact with a hard structure (e.g., bone), as the pedicle screw  535  is being positioned within a bony structure. The lead  24  electrically connects the electrode  574  to the stimulation control device  22 , through a break-away connection or other similar electrical connective means. The fixation device  535  may take on an unlimited variety of shapes and sizes depending on the specific surgical procedure being performed.  
         [0079]     In the mono-polar mode, the stimulation control device  22  includes a return electrode  38  which functions as a return path for the stimulation signal. Electrode  38  may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. In an alternative embodiment, the fixation device  500  may be bipolar, which precludes the use of the return electrode  38 .  
         [0080]     The present invention includes a method of locating a nerve in a patient that comprises the steps of providing a fixation device  500  as set forth above, engaging a patient with the first electrode  510  and the second electrode  38 , turning power on to the stimulation control device  22  through the I/O controls  26 , causing a stimulation signal  29  to be generated by the stimulation control device  22  and transmitted to the first electrode  510 , through the patient&#39;s body to the second electrode  38 , and back to the stimulation control device  22 .  
         [0000]     IV. Technical Features  
         [0081]     The stimulation control device  22  can incorporate various technical features to enhance its universality.  
         [0082]     A. Small Size  
         [0083]     According to one desirable technical feature, the stimulation control device can be sized small enough to be held and used by one hand during surgical procedures, or to be installed within a stimulation probe or surgical device. The angle of the stimulating tip facilitates access to deep as well as superficial structures without the need for a large incision. Visual and/or audible indication incorporated in the housing provides reliable feedback to the surgeon as to the request and delivery of stimulus current.  
         [0084]     According to an alternative desirable technical feature, the stimulation control device  22  may also be sized small enough to be easily removably fastened to a surgeon&#39;s arm or wrist during the surgical procedure, or positioned in close proximity to the surgical location (as shown in  FIG. 9 ), to provide sufficient audio and visual feedback to the surgeon.  
         [0085]     B. Power Source  
         [0086]     According to one desirable technical feature, power is provided by a primary battery for single use mounted inside the housing on or near the circuit board  22 .  
         [0087]     C. The Microprocessor/Microcontroller  
         [0088]     According to one desirable technical feature, the stimulation control device  22  desirably uses a standard, commercially available micro-power, flash programmable microcontroller  36 . The microcontroller  36  reads the controls operated by the surgeon, controls the timing of the stimulus pulses, and controls the feedback to the user about the status of the instrument (e.g., an LED or 1, 2, or more colors that can be on, off, or flashing).  
         [0089]     The microcontroller operates at a low voltage and low power. The microcontroller send low voltage pulses to the stimulus output stage that converts these low voltage signals into the higher voltage, controlled voltage, or controlled current, stimulus pulses that are applied to the electrode circuit. This stimulus output stage usually involves the use of a series capacitor to prevent the presence of DC current flow in the electrode circuit in normal operation or in the event of an electronic component failure.  
         [0090]     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.