System and Methods for Determining Nerve Proximity, Direction, and Pathology During Surgery

• US 20090209879A1
• Filed: 05/01/2009
• Published: 08/20/2009
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: Nuvasive Incorporated
• Original Assignee: Nuvasive Incorporated
• Inventors: Medeiros, Goretti, Kaula, Norbert F., Gharib, James, Blewett, Jeffrey J., Farquhar, Allen
• Granted Patent: US 8,050,769 B2
• Time in Patent Office: Days
• US Class Current: 600/546
• CPC Class Codes: A61B 17/00 Surgical instruments, devices or methods, e.g. tourniquets A61B18/00 takes precedence; contraceptive devices, pessaries, or applicators therefor A61F6/00; eye surgery A61F9/007; ear surgery A61F11/00
• CPC Class Codes: A61B 17/02 for holding wounds open; Tractors specula A61B1/32 ; drainage appliances for wounds A61M27/00
• CPC Class Codes: A61B 18/00 Surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body eye surgery A61F9/007; ear surgery A61F11/00
• CPC Class Codes: A61B 2017/00039 Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect
• CPC Class Codes: A61B 5/1106 to assess neuromuscular blockade, e.g. to estimate depth of anaesthesia
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/395 Details of stimulation, e.g. nerve stimulation to elicit EMG response
• CPC Class Codes: A61B 5/4893 Nerves
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61B 5/743 Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots
• CPC Class Codes: A61N 1/08 Arrangements or circuits for monitoring, protecting, controlling or indicating for external stimulators A61N1/3603; for implantable neurostimulators A61N1/36128; for heart stimulators A61N1/37; for defibrillators A61N1/3925
• CPC Class Codes: A61N 1/36 for stimulation
• CPC Class Codes: A61N 1/36017 with leads or electrodes penetrating the skin

Abstract

The present invention involves systems and methods for determining nerve proximity, nerve direction, and pathology relative to a surgical instrument based on an identified relationship between neuromuscular responses and the stimulation signal that caused the neuromuscular responses.

Claims

1. A surgical system for stimulating nerves and monitoring EMG responses to the nerve simulation, comprising:

a control unit to receive user input regarding delivery of a stimulation signal and to receive neuromuscular response data, the control unit including a touchscreen color display device to provide information indicative of two or more of;

nerve proximity, nerve direction, nerve pathology, stimulation level, EMG response data, pedicle integrity, advance or hold instructions, and instrument in use, wherein the touchscreen color display device provides an evoked potentials display option that shows the voltage waveforms for eight EMG response channels;

a connector module that provides eight EMG response channels and an electrical connection for at least one nerve stimulation instrument, the connector module having a wire connection to the control unit so that the connector module is positionable apart from the control unit;

eight pairs of EMG electrodes connectable to the eight EMG response channels of the connector module, the EMG electrodes being mountable proximate to selected leg muscles;

a first stimulation instrument comprising a dilator tube and a stimulation element that delivers the stimulation signal proximate to a distal end of the dilator tube when the dilator tube advanced through tissue in a path toward a spine; and

a second stimulation instrument comprising a pedicle probe that delivers the stimulation signal when advanced into a pedicle opening formed in the spine, wherein the pedicle probe comprises a probe tip member and handle with a user-actuatable button to activate the stimulation signal for delivery by the screw test probe.

2. The system of claim 1, further comprising the one or more sequential dilator cannulas that are deliverable through the tissue in the path toward the spine.

3. The system of claim 1, further comprising an operative corridor instrument that is deliverable over the one or more sequential dilator cannulas when advanced toward the spine.

4. The system of claim 3, wherein the operative corridor instrument comprises a working cannula that defines a tubular corridor to access the spine when the working cannula is advanced to the spine.

5. The system of claim 1, wherein the stimulation element of the first stimulation instrument comprises an obturator arranged inside the dilator tube and equipped with one or more stimulation electrodes.

6. The system of claim 5, further comprising a guide wire that is insertable through the dilator tube when the obturator is removed from the dilator tube, the guide wire being insertable through the dilator tube and into an annulus of a disc of the spine.

7. A surgical system, comprising:

a control unit to deliver a stimulation signal, to receive neuromuscular response signals in response to the stimulation signal, wherein said control unit identifies a stimulation threshold level required to evoke said neuromuscular response;

at least one EMG electrode positionable proximate to a muscle for detecting said neuromuscular response signals in response to the stimulation signal; and

a surgical instrument having at least one stimulation electrode electrically coupled to said control unit for emitting the stimulation signal, wherein in response to emitting the stimulation signal from the stimulation electrode of the surgical instrument, said control unit is determines at least one of nerve proximity relative to the surgical instrument, nerve direction relative to the surgical instrument, pedicle integrity, and nerve pathology based on the identified stimulation threshold, and

wherein said control unit automatically adjusts the magnitude of successive stimulation signals by larger increments until a first bracket having a first width containing said threshold is determined, and thereafter automatically adjusts the magnitude of successive stimulation signals until a second bracket having a second width smaller than said first width and containing said stimulation threshold is determined.

8. The surgical system of claim 7, wherein said control unit is further equipped to communicate at least one of alpha-numeric and graphical information to a user regarding at least one of nerve proximity, nerve direction, pedicle integrity, and nerve pathology.

9. The surgical system of claim 8, wherein said system includes a display for communicating said at least one of nerve proximity, nerve direction, pedicle integrity, and nerve pathology.

10. The surgical system of claim 9, wherein said display shows a color indicative a degree of at least one of said nerve proximity nerve direction, pedicle integrity, and nerve pathology.

11. The surgical system of claim 7, wherein the surgical instrument further includes at least one of a device for maintaining contact with a nerve during surgery a device for accessing a surgical target site, and a device for testing screw placement integrity.

12. The surgical system of claim 11, wherein the surgical instrument includes a nerve root retractor and wherein the control unit determines nerve pathology based on the indentified stimulation threshold.

13. The surgical system of claim 11, wherein the surgical instrument includes a screw test probe and wherein the control unit determines the proximity between the screw test probe and an exciting spinal nerve root to assess whether a medial wall of a pedicle has been breached by at least one of hole formation and screw placement.

14. The surgical system of claim 11, wherein the surgical instrument includes a dilating instrument and wherein the control unit determines at least one of proximity and direction between a nerve and the instrument based on the identified stimulation threshold.

15. The surgical system of claim 14, wherein the dilating instrument includes at least one of a K-wire, an obturator, a dilating cannula, and a working corridor instrument.

16. The system of claim 15, wherein said dilating instrument establishes an operative corridor to a spinal target site.

17. The system of claim 16, wherein said dilating instrument is deliverable in a generally lateral, trans-psoas approach to the spinal target site.

18. The system of claim 7, wherein said system is equipped to audibly communicate said at least one of nerve proximity, nerve direction, pedicle integrity, and nerve pathology.

19. A system for detecting and monitoring nerves during surgery, comprising:

a surgical accessory to transmit stimulation signals to a nerve;

an EMG electrode configured to detect voltage responses to said stimulation signals from a muscle innervated by said nerve; and

a control unit communicatively linked to said accessory and said EMG electrode, said control unit being configured to (a) direct transmission of said stimulation signals from said accessory, (b) monitor said neuromuscular responses, (c) bracket a threshold stimulation value required to evoke a predetermined voltage response value from said muscle by adjusting the stimulus intensity of successive stimulation signals by increasing increments until said predetermined voltage response is detected, (d) bisect the bracket that includes the threshold stimulation value, and (e) communicate at least one of nerve proximity, nerve direction, pedicle integrity, and nerve pathology based on said threshold stimulation value.

20. The system of claim 19, wherein said control unit is further configured to repeat the bisection of the bracket containing said threshold stimulation value until the bracket reaches a predetermined width.

21. The system of claim 19, wherein said control unit includes a display that communicates at least one of said nerve proximity, nerve direction, pedicle integrity, and nerve pathology.

22. The system of claim 21, wherein said display shows a color indicative of a degree of at least one of said nerve proximity nerve direction, pedicle integrity, and nerve pathology.

23. The system of claim 21, wherein said display comprises a graphical user interface configured to receive user input.

24. The system of claim 19, wherein said system is equipped to audibly communicate said at least one of nerve proximity, nerve direction, pedicle integrity, and nerve pathology.

25. The system of claim 19, wherein the surgical accessory includes a nerve root retractor and wherein the control unit determines nerve pathology based on the stimulation threshold.

26. The system of claim 19, wherein the surgical accessory includes a dilating instrument for establishing an operative corridor to a surgical target site and wherein the control unit determines at least one of proximity and direction between a nerve and the accessory based on the stimulation threshold.

27. The system of claim 26, wherein the dilating instrument includes at least one of a K-wire, an obturator, a dilating cannula, and a working corridor instrument.

28. The system of claim 27, wherein said dilating instrument establishes an operative corridor to a spinal target site.

29. The system of claim 28, wherein said dilating instrument is deliverable in a generally lateral, trans-psoas approach to the spinal target site.

30. The surgical system of claim 19, wherein the surgical accessory includes a screw test probe and wherein the control unit determines the proximity between the screw test probe and an exciting spinal nerve root to assess whether a medial wall of a pedicle has been breached by at least one of hole formation and screw placement.

31. A surgical system, comprising:

a control unit to deliver a stimulation signal, to receive neuromuscular response signals in response to the stimulation signal, wherein said control unit identifies a stimulation threshold level required to evoke said neuromuscular response;

at least one EMG electrode positionable proximate to a muscle for detecting said neuromuscular response signals in response to the stimulation signal; and

a surgical instrument having at least one stimulation electrode electrically coupled to said control unit for emitting the stimulation signal, wherein in response to emitting the stimulation signal from the stimulation electrode of the surgical instrument, said control unit is determines at least one of nerve proximity relative to the surgical instrument, nerve direction relative to the surgical instrument, pedicle integrity, and nerve pathology based on the identified stimulation threshold, and wherein said control unit determines said stimulation threshold by automatic adjustment of successive stimulation signals in nonuniform increments and free of user intervention.

32. A system for performing surgical procedures and assessments, comprising:

a surgical accessory having at least one stimulation electrode; and

a processing system having at least one of computer programming software, firmware and hardware pre-programmed to incorporate at least two pre-selected threshold ranges, said processing system configured to transmit an electrical stimulation signal to said at least one stimulation electrode on the surgical accessory, to measure the response of nerves depolarized by said stimulation signal, to determine a stimulation threshold of said nerves by automatic adjustment of successive stimulation signals in nonuniform increments and free of user intervention, and to communicate to a user which range of said at least two pre-selected ranges that said stimulation threshold lies to indicate at least one of nerve proximity, pedicle integrity, and nerve pathology.

33. A computer-readable medium storing a software application-executable by processor and comprising instructions that when executed by the processor cause functions to be performed comprising, (a) deliver a stimulation signal of known current from a stimulation electrode to a nerve, (b) receive a voltage response value from a sensor coupled to a muscle innervated by said nerve, (c) adjust the current level of a subsequent stimulation signal based on the voltage response received in step (b) and wherein said adjustment is an automatic adjustment of the current level according to a varying increment adjustment scale, (d) repeat steps (a)-(c) until a stimulation threshold level is determined, and (e) communicate said stimulation threshold to a user to indicate at least one of nerve proximity, pedicle integrity, and nerve pathology.