Abstract:
Improved assemblies, systems, and methods provide safeguarding against tissue 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. A disposable hand held stimulation system includes an operative element extending from the housing, the housing includes an operative element adjustment portion and a visual indication to provide feedback or status to the user.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of copending U.S. patent application Ser. No. 11/099,848, filed Apr. 6, 2005, and entitled “Systems and Methods for Intra-Operative Stimulation,” which 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 
     The invention relates generally to tissue identification and integrity testing, and more particularly to systems and methods for safeguarding against nerve and muscle injury during surgical procedures, location and stimulation of nerves and muscles, 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 
     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. 
     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 
     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. 
     One aspect of the invention provides devices, systems, and methods comprising a tissue stimulation system having a 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, and the operative element extends from the proximal end of the housing. The housing proximal end comprises an operative element adjustment portion to allow movement of the operative element, with the electrical stimulation being in the form of a stimulation signal having an amplitude and a duration for providing a first indication. A stimulation control device is electrically coupled to the operative element, the stimulation control device comprising a power source and stimulation signal generating circuitry. The tissue stimulation system may conform to the IPX1 water ingress standard. 
     In one aspect of the invention, the stimulation control device is positioned within the housing. The housing comprises a gripping base portion and the operative element adjustment portion. The operative element adjustment portion comprises a flexible nose cone. 
     The first indication comprises a visual indication located on the housing, and the housing may be tubular. The visual indication may also include a reflective element. The visual indication may comprise an illuminating circumferential ring indicator, the illuminating circumferential ring indicator being visible around the circumference of the tubular housing. 
     Yet another 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 proximal 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. 
     Additional aspects of the invention provide a tissue stimulation system that may be sterilized using ethylene oxide, for example, 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 first and second indication means may be combined into a single indication means. 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 proximal end of the probe, and the probe comprises a diameter between about 0.5 millimeters and about 1.5 millimeters. The tissue stimulation system may also further include a return electrode electrically coupled to the stimulation control device. 
     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 in either the left or right hand, a probe having an electrically conductive surface sized and configured for electrical stimulation of a targeted tissue region, the probe extending from the proximal end of the housing. The housing proximal end comprises a probe adjustment portion to allow movement of the probe. 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. 
     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 different medical procedures, can make use of a singe, stimulation control device, to which a selected surgical tool can be temporarily coupled for use. 
     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. 
     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. 
     Yet another aspect of the invention provides devices, systems, and methods, including a method of testing a tissue region of a patient that includes providing a tissue stimulation system having an operative element extending from a proximal end of a housing, the housing proximal end comprising an operative element adjustment portion to allow movement of the operative element, moving a first control device to an activation position causing a stimulation signal to be generated by the stimulation system and transmitted to the operative element, engaging the patient with the operative element at a targeted tissue region, and observing the targeted tissue region for a first indication. 
     The method may further include engaging the patient with a second electrode which is electrically coupled to the stimulation system, the second electrode allowing the stimulation signal to flow from the operative element, through the patient&#39;s body to the second electrode, and back to the stimulation system. 
     Another aspect of the invention provides devices, systems, and methods comprising a hand held tissue stimulation apparatus including a tubular shaped housing comprising a gripping base portion and an operative element adjustment portion, the gripping base portion comprising a first housing element and a second housing element, a stimulation control device positioned within the gripping base portion, a battery positioned within the gripping base portion and coupled to the stimulation control device to provide power to the stimulation control device, a visual indication coupled to a proximal end of the gripping base portion, the visual indication comprising an illuminating circumferential ring indicator, the illuminating circumferential ring indicator being visible around the circumference of the tubular housing, and an operative element having an electrically conductive surface sized and configured for electrical stimulation of a targeted tissue region, the operative element being coupled to the stimulation control device and extending from the proximal end of the operative element adjustment portion. 
     The operative element adjustment portion comprises a flexible nose cone sized and configured to allow movement of the operative element, and the visual indication further includes a reflector element. A return electrode electrically may be coupled to the stimulation control device. 
     According to yet another aspect of the invention, a kit of devices provides tissue stimulation to a targeted tissue region. The kit may include a hand held stimulation probe including a housing sized and configured to be held with either a left or right hand, the stimulation probe being sterilized and disposable, and including an operative element extending from a proximal end of the housing, the housing proximal end comprising an operative element adjustment portion to allow movement of the operative element, a lead including a return electrode coupled to the stimulation probe, and instructions for use describing the unpacking and tissue contact procedure for the stimulation probe. 
     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. 
     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 
         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. 
         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. 
         FIG. 3A  is a side view with a portion broken away and in section showing the stimulation probe having the stimulation control device embedded within the stimulation probe. 
         FIG. 3B  is a side 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. 
         FIG. 3C  is a side view with a portion broken away and in section showing an additional embodiment of the stimulation probe having a housing that includes a gripping base and a flexible nose cone, and an illuminating ring indicator. 
         FIG. 4A  is a side view of the stimulation probe of  FIG. 3   c , showing the users hand in a position on the stimulation probe to move the flexible nose cone. 
         FIG. 4B  is a side view of the stimulation probe of  FIG. 4A , showing the users hand flexing the flexible nose cone. 
         FIG. 5  is a side view with a portion broken away and in section showing elements of the flexible nose cone, the ring indicator, and the gripping base. 
         FIG. 6  is a graphical view of a desirable biphasic stimulus pulse output of the stimulation device. 
         FIG. 7  is a view showing how the geometry of the stimulation control device shown in  FIG. 2  aids in its positioning during a surgical procedure. 
         FIG. 8  is a block diagram of a circuit that the stimulation control device shown throughout the Figs. can incorporate. 
         FIGS. 9A and 9B  are perspective views showing the stimulation control device in use with a cutting device. 
         FIGS. 10A and 10B  are perspective views showing the stimulation control device in use with a drilling or screwing device. 
         FIGS. 11A and 11B  are perspective views showing the stimulation control device in use with a pilot auger device. 
         FIGS. 12A and 12B  are perspective views showing the stimulation control device in use with a fixation device. 
         FIG. 13  is a plane view of a kit used in conjunction with the stimulation probe shown in  FIG. 3C , and including the stimulation probe and instructions for use. 
         FIG. 14  is a perspective view of the stimulation probe shown in  FIG. 3C . 
         FIG. 15  is an exploded view of the stimulation probe shown in  FIG. 14 . 
     
    
    
     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 
     This Specification discloses various systems and methods for safeguarding against nerve, muscle, and tendon injury during surgical procedures or confirming the identity and/or location 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. 
     The systems and methods desirably allow the application of a stimulation signal at sufficiently high levels for the purposes of locating, stimulating, and evaluating nerve or muscle, or both nerve and muscle integrity innumerous 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. 
     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. 
     I. Overview of the System 
       FIG. 1  shows an illustrative system  20  for locating and identifying tissue and safeguarding against tissue and/or bone injury during surgical procedures. In the illustrated embodiment, the system  20  is configured for locating, monitoring, and stimulating tissue 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 . 
     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  110  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. 
     The stimulation signal  29  is adapted to provide an indication or status of the device. The indication may include a physical motor response (e.g., twitching), and/or one or more visual or audio signals from the stimulation control device  22 , which indicate to the surgeon the status of the device, and/or 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. 
     II. Medical Devices 
     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. 
     A. Stimulation Probe 
       FIGS. 3A to 3C  show various embodiments of a hand held stimulation monitor or probe  50  for identification and testing of nerves and/or muscles during surgical procedures. As shown, the stimulation probe  50  may accommodate within a generally tubularly housing  112  the electrical circuitry of a stimulation control device  22 . The stimulation probe  50  is desirably an ergonomic, 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. The stimulation probe  50  may be sterilized using ethylene oxide, for example. 
     The stimulation probe  50  is preferably sized small enough to be held and used by one hand during surgical procedures, and is ergonomically designed for use in either the left or right hand. In a representative embodiment, the stimulation probe  50  may have a width of about 20 millimeters to about 30 millimeters, and desirably about 25 millimeters. The length of the stimulation probe  50  (not including the operative element  110 ) may be about 18 centimeters to about 22 centimeters, and desirably about 20 centimeters. The operative element  110  may also include an angle or bend to facilitate access to deep as well as superficial structures without the need for a large incision. The operative element  110  will be described in greater detail later. A visual or audio indicator  126  incorporated with the housing  112  provides reliable feedback to the surgeon as to the request and delivery of stimulus current. 
     In one embodiment shown in  FIGS. 3C and 14 , the stimulation probe  50  includes a housing  112  that comprises a gripping base portion  60  and an operative element adjustment portion  62 . The operative element  110  extends from the proximal end of the adjustment portion  62 . In order to aid the surgeon in the placement of the operative element  110  at the targeted tissue region, the adjustment portion, as will be described as a nose cone  62 , may be flexible. This flexibility allows the surgeon to use either a finger or a thumb positioned on the nose cone  62  to make fine adjustments to the position of stimulating tip  111  of the operative element  110  at the targeted tissue region (see  FIGS. 4A and 4B ). The surgeon is able to grasp the gripping base  60  with the fingers and palm of the hand, and position the thumb on the nose cone  62 , and with pressure applied with the thumb, cause the stimulating tip  111  to move while maintaining a steady position of the gripping base portion  62 . This flexible nose cone  62  feature allows precise control of the position of the stimulating tip  111  with only the movement of the surgeon&#39;s thumb (or finger, depending on how the stimulating probe is held). 
     The flexible nose cone  62  may comprise a single element or it may comprise at least an inner portion  64  and an outer portion  66 , as shown in  FIG. 5 . In order to facilitate some flexibility of the proximal portion  114  of the stimulation probe  50 , the inner portion  64  of the nose cone  62  may be made of a thermoplastic material having some flexibility. One example may be LUSTRAN® ABS 348, or similar material. The outer portion  66  may comprise a softer over molded portion and may be made of a thermoplastic elastomer material having some flexibility. One example may be VERSAFLEX™ OM 3060-1 from GLS Corp. The nose cone  62  is desirably generally tapered. For example, the nose cone  62  may be rounded, as shown in  FIGS. 3A and 3B , or the nose cone may be more conical in shape, as shown in  FIG. 3C . 
     The nose cone  62  may also include one or more features, such as ribs or dimples  72 , as shown in  FIG. 14 , to improve the gripping, control, and stability of the stimulation probe  50  within the surgeon&#39;s hand. 
     The gripping base portion  60  of the housing  112  may also include an overmolded portion  68 . The overmolded portion  68  may comprise the full length of the gripping base portion  60 , or only a portion of the gripping base  60 . The soft overmolded portion  68  may include one or more features, such as dimples or ribs  70 , as shown, to improve the gripping, control, and stability of the stimulation probe  50  within the surgeon&#39;s hand. The overmolded portion  68  may comprise the same or similar material as the thermoplastic elastomer material used for the outer portion  66  of the flexible nose cone  62 . 
     In one embodiment, the stimulation probe  50  includes a housing  112  that carries an insulated lead  124 . The insulated lead  124  connects the operative element  110  positioned at the housing&#39;s proximal end  114  to the circuitry  22  within the housing  112  (see  FIG. 3A ). It is to be appreciated that the insulated lead is not necessary and the operative element  110  may be coupled to the circuitry  22  (see  FIG. 3C ). 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 conductive tip  111  of the operative element  110  is positioned in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve. 
     As shown, the stimulation probe  50  is mono-polar and is equipped with a single operative element (i.e., electrode)  110  at the housing proximal end  114 . A return electrode  130 ,  131  may be coupled to the stimulation probe  50  and may be any of a variety of electrode types (e.g., paddle, needle, wire, or surface), depending on the surgical procedure being performed. As shown, the various return electrodes  130 ,  131  are coupled to the housing distal end  118 . In an alternative embodiment, the stimulation device  50  itself may be bipolar by including a return electrode in the operative element  110 , which precludes the use of a return electrode coupled to the stimulation probe  50 . 
     As shown and described, the stimulation probe  50  may accommodate within the housing  112  the electrical circuitry of a stimulation control device  22 . In this arrangement, the stimulation probe  50  may have one or more user operable controls. Two are shown— 155  and  160 . Power switch  155  serves a dual purpose of turning the stimulation probe  500 N and OFF (or standby), 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). In this configuration, the switch may be a four position switch. Before the first use of the stimulation probe  50 , the power switch  155  is in the OFF position and keeps the stimulation probe off. After the stimulation probe  50  has been turned ON—by moving the switch  155  to an amplitude selection—the OFF position now corresponds to a standby condition, where no stimulation would be delivered. In one embodiment, once the stimulation probe  50  has been turned on, it cannot be turned off, it can only be returned to the standby condition and will remain operational for a predetermined time, e.g., at least about seven hours. This feature is intended to allow the stimulation probe  50  to only be a single use device, so it can not be turned OFF and then used again at a later date. 
     The pulse control device  160  allows for adjustment of the stimulation signal pulse width from a predefined range (e.g., about zero to about 200 microseconds). In one embodiment, the pulse control  160  may be a potentiometer to allow a slide control to increase or decrease the stimulation signal pulse width within the predefined range. 
     The stimulation pulse may have a non-adjustable frequency in the range of about 10 Hz to about 20 Hz, and desirably about 16 Hz. 
     As a representative example, the stimulation pulse desirably has a biphasic waveform with controlled current during the cathodic (leading) phase, and net DC current less than 10 microamps, switch adjustable from about 0.5 milliamps to about 20 milliamps, and pulse durations adjustable from about zero microseconds up to about 200 microseconds. A typical, biphasic stimulus pulse is shown in  FIG. 6 . 
     The operative element  110  exits the housing  112  at the proximal end  114  to deliver stimulus current to the excitable tissue. The operative element  110  comprises a length and a diameter of a conductive material, and is desirably fully insulated with the exception of the most proximal 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 tip or surface (or also referred to as active electrode)  111  to allow the surgeon to deliver the stimulus current only to the intended tissue. The small area of the stimulating surface  111  (the active electrode) of the operative element  110  ensures a high current density that will stimulate nearby excitable tissue. The insulation material  113  may comprise a medical grade heat shrink. 
     The conductive material of the operative element  110  comprises a diameter having a range between about 0.5 millimeters to about 1.5 millimeters, and may be desirably about 1.0 millimeters. The length of the operative element  110  may be about 50 millimeters to about 60 millimeters, although it is to be appreciated that the length may vary depending on the particular application. As shown, the operative element  110  may include one or more bends to facilitate accurate placement of the stimulating surface  111 . In one embodiment, the conductive material of operative element  110  is made of a stainless steel  304  solid wire, although other known conductive materials may be used. 
     As previously described, in monopolar operation, a return electrode (or indifferent electrode)  130  or  131 , for example, provides an electrical path from the body back to the control device  22  within the housing  112 . The return electrode  130  (see  FIG. 3A ) 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  FIGS. 3B and 3C ), 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 . It is to be appreciated that a return electrode and associated lead may be an integral part of the stimulation probe  50 , i.e., no plug or connector, as shown in  FIG. 3C . 
     Additionally, the device  50  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  50  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  111  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  111  of the stimulator  50  rather than the failure of the return electrode connection or some other instrumentation problem. 
     As a representative example, in use the indicator  126  may be configured to illuminate continuously in one color when the stimulation probe  50  is turned on but not in contact with tissue. After contact with tissue is made, the indicator  126  may flash (i.e., blink) to indicate that stimulation is being delivered. If the stimulation has been requested, i.e., the stimulation probe has been turned on, but there is no stimulation being delivered because of a lack of continuity between the operative element  110  and the return electrode  130 , or an inadequate connection of the operative element  110  or the return electrode  130  to the patient tissue, the indicator  126  may illuminate in a different color, and may illuminate continuously or may flash. 
     In one embodiment, as can be best seen in  FIGS. 3C and 5 , the indicator  126  comprises a ring indicator  128  that provides a visual indication around at least a portion, and desirably all of the circumference of the stimulation probe  50  generally near the flexible nose cone  62 . The visual ring indicator  128  may be an element of the gripping portion  60 , or it may be an element of the flexible nose cone  62 , or the ring indicator may positioned between the gripping portion  60  and the flexible nose cone  62 . The ring indicator  128  may also include a reflective element  129  to improve and focus the illumination effect of the light emitting source, e.g., one or more LEDs. The ring indicator  128  and the reflective element may be a single component, or more than one component (as can be seen in  FIGS. 5 and 15 ). 
     Audio feedback also makes possible the feature of assisting the surgeon with monitoring nerve integrity during surgery. The insulated lead  124  connects to the operative element  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  incorporated within the housing  112  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. 
       FIG. 15  shows an exploded view of a representative stimulation probe  50 . As can be seen, the stimulation control device  22  is positioned within the housing  112 . A battery  34  is electrically coupled to the control device  22 . A first housing element  90  and a second housing element  92  partially encapsulate the control device  22 . The ring indicator  128  and the reflective element  129  are coupled to the proximal end of the housing  112 . The operative element  110  extends through the nose cone  62  and couples to the control device  22 . Desirably, the stimulation probe  50  will be constructed in a manner to conform to at least the IPX1 standard for water ingress. 
     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. 7 ), to provide sufficient audio and/or 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. 
     The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, in a patient that comprises the steps of providing a hand-held stimulation probe  50 ,  100  as set forth above, engaging a patient with the first operative element  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 operative element  110 , through the patient&#39;s body to the second electrode  130 , and back to the stimulation control device  22 . The method may also include the step of observing the indicator  126  to confirm the stimulation probe  50 ,  100  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
     B. The Stimulation Control Device 
     As  FIG. 8  shows, the stimulation control device  22  includes a circuit  32  that generates electrical stimulation waveforms. A battery  34  desirably provides the power. The control device  22  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. 
     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. 
     C. Incorporation with Surgical Devices 
     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 (as previously described for the stimulation probe  50 ). 
     1. Cutting Device 
     In  FIGS. 9A and 9B , a device  200  is shown that incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except the device  200  comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 9A  shows the tool to be a cutting device  200  (e.g., scalpel) removably coupled to a stimulation control device  22 . 
     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). 
     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  desirably 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 . 
     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, needle, 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 . 
     In the embodiment shown in  FIG. 9B , 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., zero through 200 microseconds). 
     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. 
     Additionally, the device  200  may incorporate a visual or audio indicator for the surgeon, as previously described. 
     The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, 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 . The method may also include the step of observing the indicator  126  to confirm the cutting device  200  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
     2. Drilling Device 
     In  FIGS. 10A and 10B , a device  300  is shown that incorporates all the features disclosed in the description of the stimulation probe  50 ,  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. 10A  is drilling device  300  is removably coupled to a stimulation control device  22 . 
     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). 
     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). 
     The drilling device  300  desirably 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 . 
     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, needle, 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 . 
     In  FIG. 10B , 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., zero 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. 
     Additionally, the device  300  may incorporate a visual or audio indicator for the surgeon, as previously described. 
     The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, 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 . The method may also include the step of observing the indicator  126  to confirm the drilling device  400  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
     3. Pilot Auger 
     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. 
     This embodiment incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except this embodiment comprises the additional feature of providing an “energized” surgical device or tool.  FIG. 11A  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  desirably 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 . 
     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, needle, 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 . 
     As  FIG. 11B  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. 
     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. 
     The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, 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 . The method may also include the step of observing the indicator  126  to confirm the pilot auger device  400  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
     D. Incorporation with Fixation Devices 
     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. 
     This embodiment incorporates all the features disclosed in the description of the stimulation probe  50 ,  100 , except this embodiment comprises the additional feature of providing an “energized” fixation device or tool.  FIG. 12A  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 desirably 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 . 
     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, needle, 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 . 
     In yet an additional alternative embodiment (see  FIG. 12B ), 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. 
     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, needle, 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 . 
     The present invention includes a method of identifying/locating tissue, e.g., a nerve or muscle, 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 . The method may also include the step of observing the indicator  126  to confirm the fixation device  500  is generating a stimulation signal. The method may also include the step of observing a tissue region to observe tissue movement or a lack thereof. 
     IV. Technical Features 
     The stimulation control device  22 , either alone or when incorporated into a stimulation probe or surgical device, can incorporate various technical features to enhance its universality. 
     A. Small Size 
     According to one desirable technical feature, the stimulation control device  22  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 or status to the surgeon as to the request and delivery of stimulus current. 
     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. 7 ), to provide sufficient audio and/or visual feedback to the surgeon. 
     B. Power Source 
     According to one desirable technical feature, power is provided by one or more primary batteries  34  for single use positioned inside the housing and coupled to the control device  22 . A representative battery  34  may include a size “N” alkaline battery. In one embodiment, two size “N” alkaline batteries in series are included to provide a 3 volt power source. This configuration is sized and configured to provide an operating life of at least seven hours of operation—either continuous or intermittent stimulation. 
     C. The Microprocessor/Microcontroller 
     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 with 1, 2, or more colors that can be on, off, or flashing). 
     The microcontroller operates at a low voltage and low power. The microcontroller send low voltage pulses to the stimulus output stage  46  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  46  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. 
     V. Representative Use of a Stimulation Probe 
     The stimulation probe  50 ,  100 , as described, make possible the application of a stimulation signal at sufficiently high levels for the purposes of locating, 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. 
     Instructions for use  80  are desirably included in a kit  82  along with a stimulation probe  50 . The kit  82  can take various forms. In the illustrated embodiment, kit  82  comprises a sterile, wrapped assembly. A representative kit  82  includes an interior tray  84  made, e.g., from die cut cardboard, plastic sheet, or thermo-formed plastic material, which hold the contents. Kit  82  also desirably includes instructions for use  80  for using the contents of the kit to carry out a desired therapeutic and/or diagnostic objectives. 
     The instructions  80  guide the user through the steps of unpacking the stimulation probe  50 , positioning the electrodes, and disposing of the single use disposable stimulator  50 . Representative instructions may include, but are not limited to:
         Remove the stimulation probe  50  from sterile package  88 .   Remove cover  94  (e.g., a silicone cover) from the operative element  110 .   Remove protective cover  86  from the return electrode  131 .   Position the return electrode  131  in contact with the patient such that:
           1. The return electrode is desirably positioned in an area remote from the area to be stimulated.   2. The return electrode is desirably not positioned across the body from the side being stimulated.   3. The return electrode is desirably not in muscle tissue.   
           Turn the stimulation probe  50  ON by moving the power switch  155  from OFF to the 0.5 mA setting (or greater). The stimulation probe  50  desirably is turned ON before the operative element  110  makes contact with tissue.   The indicator  126  will be illuminated yellow (for example) continuously if the stimulation probe  50  is ON, but not in contact with tissue.   Contact tissue with the operative element  110 .   Adjust the pulse control  160  gradually to increase the level of stimulation. The indicator  126  will flash yellow indicating that stimulation is being delivered.   A flashing red (for example) indicator  126  means that stimulation has been requested, but no stimulation is being delivered because of inadequate connection of the operative element  110  or the return electrode  131  to the patient tissue. Check the return electrode contact and position, and check the operative element  110  contact and position.   Placing the power switch  155  to the off/standby position will stop stimulation and the visual indictor  126  will be illuminated yellow continuously.   Placing the pulse control  160  at the minimum position will stop stimulation and the visual indictor  126  will be illuminated yellow continuously.   A low/depleted battery  34  will cause the stimulation probe  50  to automatically turn OFF and the visual indicator  126  will not be illuminated. No further use of the stimulator  50  will be possible.   At end of use, move the power switch  155  to the off/standby position and move the pulse control  160  to the minimum position.   Cut off and dispose of the return electrode  131  in an appropriate sharps/biohazard container.   Dispose of the stimulation probe  50  per hospital or facility guidelines.       

     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.