HK1096620B - Systems and methods for intra-operative stimulation - Google Patents

Description

Field of the Invention

The invention relates generally to nerve and muscle identification and integrity testing, and more particularly to systems and methods for safeguarding against nerve and muscle injury during surgical procedures, identification and assessment of nerve and muscle integrity following traumatic injuries, and verification of range of motion and attributes of muscle contraction during reconstructive surgery.

Background of the invention

US-5,284,154 discloses an apparatus for locating a nerve and for protecting nerves from injury during surgery. A system according to the preamble of claim 1 is known from US-4,515,168 .

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.

Summary of the Invention

According to the present invention there is provided a tissue stimulation system according to claim 1.

The invention provides devices for intra-aperative stimulation. The intra-operative stimulation enables accurate evaluation of the neuromuscular system to guide repair or reconstructive surgery.

Additional aspects of the invention provide a tissue stimulation system that may be sterilized and prepackaged for single use. The stimulation signal of the tissue stimulation system includes an amplitude that may range between about zero milliamps and about 20 milliamps, allowing for accurate selective stimulation of both muscles and nerves, and also identification of nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions. The tissue stimulation signal duration may include a range between about zero microseconds and about 200 microseconds, for example. The first indication provided by the tissue stimulation system may include, for example, audio and visual indications. The tissue stimulation system may further include a second indication means to provide confirmation of power on to the device and delivery of a stimulation signal to the electrically conductive surface. In one embodiment, the electrically conductive surface of the probe comprises between about 1 millimeter and about 10 millimeters of the distal end of the probe, and the probe comprises a diameter between about 0.5 millimeters and about 1 millimeter. The tissue stimulation system may also further include a return electrode electrically coupled to the stimulation control device.

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 devices 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, muscles 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.

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. 1A is a perspective view showing the stimulation control device in use with a stimulation probe.
• Fig. 1B is a perspective view with a portion broken away and in section showing the stimulation probe having the stimulation control device embedded within the stimulation probe, and showing an optional needle-like return electrode.
• Fig. 2 is a block diagram of a circuit that the stimulation control device shown in the Figs. can incorporate.

Description of Referred Embodiments

This Specification discloses various systems and methods for safeguarding against nerve, muscle, and tendon injury during surgical procedures or confirming the identity of nerves, muscles, and tendons and evaluating their function or the function of muscles enervated by those nerves. The systems and methods are particularly well suited for assisting surgeons in identification of nerves and muscles in order to assure nerve and muscle integrity during medical procedures.

The systems and methods desirably allow the application of a stimulation signal at sufficiently high levels for the purpose of stimulating and evaluating nerve or muscle, or both nerve and muscle integrity in numerous medical procedures, including, but not limited to, evaluating proximity to a targeted tissue region, evaluating proximity to a nerve or to identify nerve tissue, evaluating if a nerve is intact (i.e., following a traumatic injury) to determine if a repair may be needed, evaluating muscle contraction to determine whether or not the muscle is innervated and/or whether the muscle is intact and/or whether the muscle is severed, and evaluating muscle and tendon length and function following a repair or tendon transfer prior to completing a surgical procedure.

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.

Figs. 1A and 1B show various embodiments of a hand held stimulation monitor or probe 100 for identification and testing of nerves and/or muscles during surgical procedures. The stimulation probe 100 is preferably a sterile, single use instrument intended for use during surgical procedures to identify nerves and muscles, muscle attachments, or to contract muscles to assess the quality of surgical interventions or the need for surgical interventions, or to evaluate the function of nerves already identified through visual means.

The stimulation probe is preferably sized small enough to be held and used by one hand during surgical procedures. The angle of the stimulating tip facilitates access to deep as well as superficial structures without the need for a large incision. A visual or audio indicator 126 incorporated in the housing provides reliable feedback to the surgeon as to the request and delivery of stimulus current.

In one embodiment, the stimulation probe 100 includes a housing 112 that carries an insulated lead 124. The insulated lead 124 connects to an electrode 110 positioned at the housing's distal and 114. The lead 124 within the housing 112 is insulated from the housing 112 using common insulating means (e.g., wire insulation, washers, gaskets, spacers, bushings, and the like) . The electrode 110 is positioned in electrical conductive contact with at least one muscle, or at least one nerve, or at least one muscle and nerve.

In an additional embodiment, the stimulation probe 100 is mono-polar and is equipped with a single electrode 110 at the housing proximal end 114. Electrode 110 may be any of a variety of electrode types (e.g., paddle, wire, or surface), depending on the surgical procedure being performed. In an alternative embodiment, the stimulation device 100 itself may be bipolar, which precludes the use of the return electrode 130.

As shown in Figs. 1A and 1B, the stimulation probe 100 may accommodate within the housing 112 the electrical circuitry of a stimulation control device 22. In this arrangement, the stimulation probe 100 may have two operational slide controls, 155 and 160. Power switch 155 serves a dual purpose of turning the stimulation signal to the probe 100 on and off, and also can be stepped to control the stimulation signal amplitude selection within a predefined range (e.g., 0.5, 2.0, and 20 mA). The pulse control switch 160 allows for adjustment of the stimulation signal pulse width from a redefined range, (e.g., 0. through 200 microseconds) .

An operative element, such as a stimulus probe 110, exits the housing at the distal end 114 to delivery stimulus current to the excitable tissue. The probe or electrode 110 comprises a length and a diameter, and is desirably fully insulated with the exception of the most distal end, e.g. about 1.0 millimeters to about 10 millimeters, and desirably about 4 millimeters to about 6 millimeters, which is non-insulated and serves as the stimulating surface to allow the surgeon to deliver the stimulus current only to the intended tissue. The small area of the probe (the active electrode) ensures a high current density that will stimulate nearby excitable tissue. The probe diameter may range between about 0.5 millimeters to about 1.0 millimeters, and may be desirably about 0.75 millimeters.

In monopolar operation, a return electrode (or indifferent electrode) 130 provides an electrical path from the body back to the control device 22. The return electrode 130 may be placed on the surface of intact skin (e.g., surface electrodes as used for ECG monitoring during surgical procedures) or it might be needle-live 131 (see Fig. 3B), and be placed in the surgical field or penetrate through intact skin. The housing's proximal 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.

Additionally, the device 100 may desirably incorporate a visual or audio indicator 126 for the surgeon. This visual or audio indicator 126 allows the surgeon to confirm that the stimulator 100 is delivering stimulus current to the tissue it is contacting. Through the use of different tones, colors, different flash rates, etc., the indicator 126 (which can take the form, e.g., of a light omitting diode -- LED) allows the surgeon to confirm that the stimulating tip 110 is in place, the instrument is turned ON, and that stimulus current is flowing. Thus the surgeon has a much greater confidence that the failure to elicit a muscle contraction is because of lack of viable nervous tissue near the tip of the stimulator 100 rather than the failure of the return electrode connection or some other instrumentation problem.

Audio feedback also makes possible the feature of assisting the surgeon with monitoring nerve integrity during surgery. The insulated lead 124 connects to an electrode 110 that, in use, is positioned within the surgical field on a nerve distal to the surgical site. Stimulation of the nerve causes muscle contraction distally. The stimulation control device 22 may be programmed to provide an audio tone followed by a stimulation pulse at prescribed intervals. The audio tone reminds the surgeon to observe the distal muscle contraction to confirm upon stimulation that the nerve is functioning and intact.

The hand-held stimulation probe 100, as set forth above, can be used to locate a nerve in a patient by engaging a patient with the first electrode 110 and the second electrode 130, moving the power switch 155 to an activation position causing a stimulation signal 29 to be generated by the stimulation control device 22 and transmitted to the first electrode 110, through the patient's body to the second electrode 130, and back to the stimulation control device 22.

As Fig. 2 shows, the stimulation control device 22 includes a circuit 32 that generates electrical stimulation waveforms. A battery 34 internal to the stimulator 100 desirably provides the power. The pulse generator 28 also desirably includes an on-board, programmable microprocessor 36, which carries embedded code. The code expresses pre-programmed rules or algorithms for generating the desired electrical stimulation waveforms using the stimulus output circuit 46 and for operating the visible or audible indicator 126 based on the controls actuated by the surgeon.

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.

According to one desirable technical feature, the stimulation control device can be sized small enough to be held and used by one hand during surgical procedures. The angle of the stimulating tip facilitates access to deep as well as superficial structures without the need for a large incision. Visual and/or audible indication incorporated in the housing provides reliable feedback to the surgeon as to the request and delivery of stimulus current.

According to one desirable technical feature, power is provided by a primary battery for single use mounted inside the housing on or near the circuit board 22.

According to one desirably technical feature, the stimulation control device 22 desirably uses a standard, commercially available micro-power, flash programmable microcontroller 36. The microcontroller 36 reads the controls operated by the surgeon, controls the timing of the stimulus pulses, and controls the feedback to the user about the status of the instrument (e.g. , an LED or 1, 2, or more colors that can be on, off, or flashing).

The microcontroller operates at a low voltage and low power. The microcontroller sends low voltage pulses to the stimulus output stage that converts these low voltage signals into the higher voltage, controlled voltage, or controlled current, stimulus pulses that are applied to the electrode circuit. This stimulus output stage usually involves the use of a series capacitor to prevent the presence of DC current flow in the electrode circuit in normal operation or in the event of an electronic component failure.

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.

Claims (16)

1. A hand-held tissue stimulation system (100) comprising:

   a probe (110) having an electrically conductive surface sized and configured for electrical stimulation of a targeted tissue region, wherein the electrical stimulation is in the form of a signal (29) having an amplitude and a duration for providing a physical motor response,

   a housing (112) having a proximal end (114) and a distal end, the probe extending from the distal end of the housing and the housing being sized and configured to be held in a hand by a user so as to provide for placement of the probe,

   a stimulation control device (22) positioned within the housing and electrically coupled to the probe, the stimulation control device comprising stimulation signal generating circuitry (32),

   a power source (34) positioned within the housing;

   the housing including a first control device (155) for providing adjustment of the stimulation signal amplitude, the first control device being electrically coupled to the stimulation control device,

   characterised in that the first control device (155) is also for turning the stimulation signal to the probe on and off and in that the housing includes a second control device (160) for providing adjustment of the stimulation signal duration, the second control device being electrically coupled to the stimulation control device.
2. A tissue stimulation system according to claim 1, wherein the stimulation signal amplitude ranges between zero milliamps and about 20 milliamps, allowing for selective stimulation of a muscle or a nerve.
3. A tissue stimulation system according to claim 1 or 2, wherein the stimulation signal duration ranges between about zero microseconds and about 200 microseconds.
4. A tissue stimulation system according to any one of claims 1 to 3, wherein the physical motor response includes an indication of close proximity of the probe to a nerve or to identify nerve tissue.
5. A tissue stimulation system according to any one of claims 1 to 3, wherein the physical motor response includes an indication of an intact nerve to determine if a repair is needed.
6. A tissue stimulation system according to any one of claims 1 to 3, wherein the physical motor response includes an indication of a muscle condition to identify whether the muscle is innervated or whether the muscle is intact or whether the muscle is severed.
7. A tissue stimulation system according to any one of claims 1 to 3, wherein the physical motor response includes an indication of muscle and tendon length and function following a repair or tendon transfer prior to completing a surgical procedure.
8. A tissue stimulation system according to any one of the preceding claims, further comprising a first indication means which includes a visual or audio indication (126).
9. A tissue stimulation system according to any one of the preceding claims, wherein the tissue stimulation system is sterilized and prepackaged for single use.
10. A tissue stimulation system according to any one of the preceding claims, wherein the electrically conductive surface of the probe (110) comprises between about 1 millimeter and about 10 millimeters of the distal end of the probe.
11. A tissue stimulation system according to any one of the preceding claims wherein the probe (110) comprises a diameter between about 0.5 millimeter and about 1.0 millimeter.
12. A tissue stimulation system according to any one of the preceding claims, further including a return electrode (130) electrically coupled to the stimulation control device (22)
13. A tissue stimulation system according to any one of the preceding claims, wherein the probe (110) is non-linear in shape.
14. A tissue stimulation system according to any one of the preceding claims, wherein the housing (112) is tubular shaped.
15. A tissue stimulation system according to claim 8, further including a second indication means to provide confirmation of power on to the device and delivery of a stimulation signal to the electrically conductive surface.
16. A tissue stimulation system according to claim 15, wherein the second indication means is located on the housing.