Patent Application
20140371622
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.
Even with today's sophisticated medical devices, surgical procedures are not risk-free. Each patient'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'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.
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.
An embodiment of a method according to the present invention includes a method of avoiding nerve tissue in a surgical procedure. The targeted tissue in a first application step, a first electrical stimulation is applied with an electrode to a first tissue region along the first potential incision length. The first tissue region may be cutaneous or subcutaneous. During the first application step, a neural response may be observed. In the event that a neural response is observed, a second incision location and a second potential incision length may be identified, so as to avoid damage to the nerve which was stimulated during the first application step. In a second application step, a second electrical stimulation may be applied with the electrode to a second tissue region along the second potential incision length. During the second application, a neural response may or may not be observed. If no neural response is observed, a surgical procedure may be performed on or through the second tissue region. The surgical procedure may include the step of incising a portion of the second tissue region along a portion of the second potential incision length.
According to one aspect of a method according to the present invention, if no neural response is observed in response to a stimulation, a parameter of the stimulation may be adjusted and, in a third application step, a third electrical stimulation may be applied with an electrode to the first tissue region along the first potential incision length. The adjustment to the stimulation parameter may be a decrease in stimulation intensity by reducing one or both of stimulation pulse duration and stimulation amplitude. Alternatively, the adjustment to the stimulation parameter may be an increase in stimulation intensity by increasing one or both of stimulation pulse duration and stimulation amplitude.
Another embodiment of a method according to the present invention includes a method of locating nerve tissue to perform a surgical procedure, perhaps in the area of or on the nerve tissue. The method includes identifying a first potential incision location and a first potential incision length. In a first application step, a first electrical stimulation is applied with an electrode to a tissue region along the first potential incision length. The tissue region may include tissue that is cutaneous or subcutaneous. During the first application step, a neural response may or may not be observed. If no desired neural response is observed, a parameter of the electrical stimulation may be altered, and, in a second application step, a second stimulation may be applied with the electrode to the tissue region. During the second application step, a neural response may or may not be observed. If a neural response is observed, after the first and second application steps, an incision may be made along at least a portion of the first potential incision length, and a surgical procedure may be performed through or accomplished by the incision. The method may further include, in a third application step, applying the first stimulation to the tissue region, and observing the desired neural response during the third application step.
According to an aspect of a method according to this embodiment, the first application step may be performed before the altering step and the second application step may be performed after the altering step. The altering step may include the step of increasing or decreasing electrical stimulation intensity, which may be accomplished by increasing or decreasing, respectively, at least one of electrical stimulation amplitude and/or pulse duration.
According to another aspect of a method according to the present invention, the application steps may include the step of translating the electrode along at least a portion of an incision length while the electrode is in contact with the tissue. Thus, the electrical stimulation may be applied while the electrode is moving in contact with the tissue.
According to yet another aspect of a method according to the present invention, the surgical procedure may include the step of removing scar tissue, which may be removed through or caused by the incision. In one embodiment two devices are used for stimulation and surgery, respectively. For instance embodiments of systems disclosed herein may be used for electrical stimulation, and a scalpel may be used for performing the surgical procedure.
Another embodiment of a method according to the present invention is a method for honing in on nerve fibers disposed below or innervating animal tissue, which may be cutaneous or subcutaneous tissue. The method includes the step of applying a first electrical stimulation to animal tissue, at a first stimulation intensity, within an identified stimulation region, the first electrical stimulation being applied with an electrode in contact with the tissue. A plurality of first active stimulation locations may be identified within the stimulation region. The active stimulation locations are locations of the electrode in contact with tissue at which one or more neural responses are generated in response to the first electrical stimulation. The plurality of first active stimulation locations is disposed about a perimeter of a focused stimulation region. At a reduced stimulation intensity, a second electrical stimulation may be applied within the focused stimulation region. In a second identifying step, at least one second active stimulation location may be identified within the focused stimulation region. The reduced stimulation intensity may be generated by a step of altering an electrical stimulation parameter of the electrical stimulation. The step of altering may include reducing at least one of electrical stimulation pulse duration and electrical stimulation pulse amplitude.
According to an aspect of such embodiment, the first identifying step may include the step of translating the electrode across the tissue while applying the first electrical stimulation. The electrode may be translated in a desired pattern, such as a star pattern, a zig-zag pattern, or a spiral pattern.
According to another aspect of an embodiment of honing in on nerve fibers, the second identifying step may include the step of translating the electrode across the tissue while applying the second electrical stimulation. The electrode may be translated in a desired pattern, such as a star pattern, a zig-zag pattern, or a spiral pattern.
Yet another embodiment of a method according to the present invention includes a method of seeking a neural response to electrical stimulation. The method includes the step of identifying a prospecting location on animal tissue, which may be cutaneous or subcutaneous. This location may be selected based on prior experience with other patients or prior experience with a specific patient. Alternatively, the location may be randomly selected. An electrical stimulation maybe applied to the tissue at the prospecting location with an electrode to determine whether a neural response is generated. A neural response may or may not be observed.
If no neural response is observed, the electrode may be translated while in contact with the tissue radially outward from the prospecting location in a first direction for a first honing distance. The method may further include the step of translating the electrode in a second direction back to the prospecting location. The electrode may then be translated radially outward from the prospecting location in a third direction for a second honing distance, and a neural response to the electrical stimulation may be observed. The third direction may be substantially the same as the second direction, and the second honing distance may be substantially the same as the first honing distance.
According to an aspect of such embodiment, the step of translating in the first direction may be performed while applying the electrical stimulation to the tissue. Alternatively or additionally, one or more of the translating steps may be performed while the electrode is in contact with the tissue. The second direction may be opposite the first direction.
According to another aspect of an embodiment of seeking a neural response, the method may include the step of identifying an active stimulation location on the tissue.
According to yet another aspect of an embodiment of seeking a neural response, one or more of the following steps may be repeated: identifying a prospecting location; applying electrical stimulation to the tissue at the prospecting location with an electrode to determine whether a neural response is generated; and identifying an active stimulation location on the tissue.
Features and advantages of the inventions are set forth in the following Description and Drawings, as well as the appended description of technical features.
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.
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 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.
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.
In an exemplary embodiment, and as can be seen in
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.
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.
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
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
The nose cone 62 may also include one or more features, such as ribs or dimples 72, as shown in
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'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's proximal end 114 to the circuitry 22 within the housing 112 (see
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 500N 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
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
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
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.
Alternatively, as
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'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.
As
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).
In
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
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'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
In
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
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'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
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.
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
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'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.
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
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'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.
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.
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's arm or wrist during the surgical procedure, or positioned in close proximity to the surgical location (as shown in
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.
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.
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:
Nerve location may be performed for a variety of reasons, including location for identification prior to or during a “nerve cleaning” procedure, and location for avoidance of iatrogenic nerve injury. One problem that has long persisted in the field of reconstructive and microvascular surgery is the continued occurrence of iatrogenic nerve injury during surgery. Iatrogenic nerve injury during surgery is a deservedly feared complication, resulting in pain and possible permanent loss of function for the patient and malpractice litigation and probable liability for the physician. One retrospective study of 444 randomly sampled malpractice claims revealed that 14% were peripheral nerve injuries.
Reported nerve injury rates are surprisingly high and, as with most complications, are probably underreported.
While nerve injury is perhaps not totally avoidable, the capacity to stimulate nerves and muscles intraoperatively makes surgery safer and more predictable, and improves outcomes. This is difficult when operating through areas scarred by trauma, infection, tumors or previous surgery that obliterates the normal, anatomical landmarks. Distinguishing nerve from adjacent tissue is difficult or impossible by visual inspection. The ability to electrically stimulate tissue to elicit a response is frequently of crucial importance to identify and protect nerves whose identity and location are obscured by scarring and abnormal anatomy.
While various nerve stimulators exist, they have been problematic for a number of reasons. For instance, scar is an effective insulator and it has been discovered that a lack of response to electrical stimulation from existing nerve stimulators may be due to inadequate stimulus intensity. Thus, failure to elicit a response with conventional intraoperative stimulation may have indicated that the structure in question was not a nerve and was, therefore, safe to cut. However, it may also have meant that the stimulator was not functioning properly or that the stimulus provided by the prior art stimulator was insufficient to stimulate the nerve due to, e.g., scar-related, or other, dysfunction. When there is a failure to elicit a response, and a surgeon is still suspicious, the surgeon must extend the surgical exposure time significantly or call for the operating microscope to dissect around the structure in question thought to be innervated by nerve tissue. These processes may take considerable time, will add to the service cost through extra operating room time and expensive billing codes for microsurgery, and are not processes that most orthopedic surgeons can actually perform. Existing stimulators have been unreliable and undependable (the Vari-Stim® by Medtronic Xomed, Inc., has been recalled; Recall # Z-0947-2009), which adds to the problem of uncertainty.
Alternatively, rather than locating a nerve and then performing a surgical procedure remotely from the located nerve, it may be desirable to locate a nerve precisely to perform a surgical procedure adjacent to or on the nerve tissue. Very broad, but safe, stimulation capability, from stimulating entire muscle regions to individual nerve fibers, is desirable. These features enable the surgeon to avoid dangerous “false negative” responses, and allow the surgeon to perform threshold testing in a semi-quantitative manner. Indeed, wide-range, continuously-variable stimulus capability allows the surgeon to hone in on an area suspected of containing nerve tissue and then precisely localizing the nerve by beginning with a higher stimulus intensity and gradually lowering the intensity as the nerve is excavated from the scar tissue. This has allowed identification of nerves that were heavily scarred and indistinguishable from adjacent tissue and, in several cases, has avoided erroneous sacrifice of a critical nerve that would have significantly, detrimentally, affected the outcome of a surgery.
A first embodiment 1600 of a method according to the present invention includes the steps depicted in
The method may further include the steps of altering electrical stimulation parameters, such as by increasing or decreasing the electrical stimulation pulse current amplitude and/or the pulse time duration. Such altering of stimulation parameters may occur, for example, after it has been determined whether a neural response was generated by previous stimulation. For instance, it may be desirable to confirm the neural response to determine whether the observed response or lacking response were false. Such confirmation may be made by adjusting stimulation parameters 1614,1616 and then again applying a stimulation 1604 to the same tissue region that was stimulated when the neural response determination 1606 was made. For example, if no neural response was observed, it may be desirable to adjust electrical stimulation parameters 1614 to increase stimulation intensity (pulse duration and/or amplitude) of the electrical stimulation to confirm that the lacking neural response was not a false negative. Additionally, if a neural response was observed, it may be desirable to adjust electrical stimulation parameters 1616 to decrease stimulation intensity (pulse duration and/or amplitude) to confirm that the neural response was not a false positive. The stimulation pulse train is preferably provided continuously once it has started, but it may optionally be paused or stopped.
A second embodiment 1700 of a method according to the present invention is shown in
Since the first stimulation is provided at a maximum stimulation level, an active region 1814 including active stimulation locations 1812 is likely to be identified for a given nerve or set of nerve fibers 1802. This active region 1814 is likely to be smaller in size in at least one dimension than the tissue region 1804 identified to be at least partially stimulated prior. That is, a tissue region 1804 is swept to identify a smaller, or focused, active region 1814. The sweeping of a stimulation path may be done continuously, or interruptedly, and may be of any pattern, though a zig-zag or spiral pattern is preferred. Once an active region 1814 is identified, which may include one or more of the identified active stimulation locations 1812, a parameter of the electrical stimulation to be applied is modified or adjusted 1710. For instance, the stimulation intensity (pulse duration and/or amplitude) could be reduced. After the modification of the stimulation parameter 1710, then a second electrical stimulation 1704 is applied to the tissue region 1804. The second stimulation 1704 may be confined to the active region 1814 within the tissue region 1804, or may extend beyond the active region 1814. Preferably, the second stimulation 1704 is confined to a second stimulation path 1816 located entirely within the previously identified active region 1814 so as to minimize the stimulation area and reduce the time in which a nerve is located. In response to the second electrical stimulation 1704 applied at various stimulation locations, preferably all contained within the previously identified active region 1814, a second neural response may be generated and observed. The second neural response may be generated by stimulation of the same nerve or nerve fibers 1802 that were stimulated by the first stimulation. The surgeon may identify, measure, and/or document 1708 one or more active stimulation locations 1822 at which such response is observed. In other words, one or more positions of the electrode 111, at which a neural response is generated in response to the second stimulation 1704, is or are identified, measured, and/or documented.
The process of modifying at least one stimulation parameter and then applying stimulation may be repeated as many times as desired to achieve an active region of a desired size, indicative of present neural fibers. In such iterative application, a previously identified active region preferably becomes the next stimulation region, such that with each iteration, the area of tissue 1810 to be stimulated decreases. If the active region is of a desired size or a given stimulation intensity has been reached, thereby possibly limiting the narrowness of the active region, the method may be ended having identified an active region of a desired size or the method may continue with, for example, an incision that may be made 1712 near the active region in an attempt to, for example, expose the nerve or nerve fibers 1802.
In a variation of the second embodiment 1700, the identification step 1702, in which a stimulation region 1804 is identified, may be eliminated and replaced by, or supplemented with, a prospecting step. Reference to
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.
This application is a continuation of co-pending U.S. patent application Ser. No. 12/806,698, filed Aug. 19, 2010, and entitled “Systems and Methods for Intra-Operative Stimulation,” which claims the benefit of U.S. Patent Application Ser. No. 61/338,312, filed Feb. 16, 2010, entitled “Systems and Methods for Intra-Operative Stimulation, and is a continuation-in-part of co-pending U.S. patent application Ser. No. 11/651,165, filed Jan. 9, 2007, and entitled “Systems and Methods for Intra-Operative Stimulation,” which is a continuation-in-part of 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,” each of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61338312 | Feb 2010 | US | |
| 60657277 | Mar 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12806698 | Aug 2010 | US |
| Child | 14473221 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11651165 | Jan 2007 | US |
| Child | 12806698 | US | |
| Parent | 11099848 | Apr 2005 | US |
| Child | 11651165 | US |
