System and methods for determining nerve proximity, direction, and pathology during surgery

• US 7,920,922 B2
• Filed: 02/24/2010
• Issued: 04/05/2011
• Est. Priority Date: 07/11/2001
• Status: Expired due to Fees

• Current Assignee: Nuvasive Incorporated
• Original Assignee: Nuvasive Incorporated
• Inventors: Farquhar, Allen, Kaula, Norbert F., Gharib, James, Blewett, Jeffrey J.
• Primary Examiner(s): KAHELIN, MICHAEL WILLIAM
• Application Number:
  US12/711,937
• Publication Number:
  US 20100152604A1
• Time in Patent Office: 405 Days
• Field of Search: 607/48, 600/554
• US Class Current: 607/48
• 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 5/24 Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• 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 method of establishing an operative corridor for spinal surgery, comprising:

mounting a plurality of EMG electrodes proximate to selected leg muscles;

activating a nerve monitoring system that outputs a stimulation current signal to one or more surgical access instruments and that, in response to signals from the EMG electrodes, displays neuromuscular response information which is indicative of nerve proximity;

advancing a plurality of sequential dilator cannulas through bodily tissue having neural structures in a selected path toward a targeted intervertebral disc of a spine, each of the sequential dilator cannulas having at least one stimulation electrode that delivers the stimulation signal to the bodily tissue before reaching the spine;

during advancement of each respective sequential dilator cannula through the bodily tissue, viewing the neuromuscular response information on a display device of the nerve monitoring system for an indication of nerve proximity when the stimulation signal is delivered to the bodily tissue from the respective sequential dilator cannula;

advancing a working corridor instrument over an outermost dilator cannula of the plurality of sequential dilator cannulas toward the targeted intervertebral disc of the spine; and

establishing an operative corridor to the targeted intervertebral disc of the spine using the working corridor instrument.

2. The method of claim 1, further comprising the step of advancing an initial dilating assembly through the bodily tissue along the selected path toward the targeted intervertebral before advancing the plurality of sequential dilator cannulas, the initial dilating assembly comprising an initial dilator cannula and a removable inner element having a stimulation electrode that delivers the stimulation signal to the bodily tissue prior to accessing the spine.

3. The method of claim 2, further comprising viewing the neuromuscular response information on the display device of the nerve monitoring system during advancement of the initial dilating assembly through the bodily tissue and prior to accessing the spine.

4. The method of claim 3, further comprising inserting a guide wire through a lumen of the initial dilator cannula after the initial dilator cannula is advanced through the bodily tissue so that the guide wire penetrates an annulus of the targeted intervertebral disc of the spine.

5. The method of claim 4, wherein the removable inner element of the initial dilating assembly comprises an obturator arranged inside the initial dilator cannula and the at least one stimulation electrode.

6. The method of claim 4, further comprising removing the removable inner element from the initial dilator cannula prior to inserting the guide wire through the initial dilator cannula.

7. The method of claim 1, wherein the neuromuscular response information displayed by the nerve monitoring system comprises EMG voltage waveforms.

8. The method of claim 1, further comprising removing the plurality of sequential dilator cannulas from the working corridor instrument prior to establishing the operative corridor to the targeted intervertebral disc of the spine.

9. The method of claim 1, wherein the working corridor instrument comprises a cannula that defines an inner lumen.

10. The method of claim 1, wherein the nerve monitoring system contemporaneously displays the neuromuscular response information which is indicative of nerve proximity and a spine image indicative of electrode placement.

11. The method of claim 1, wherein the neuromuscular response information comprises a stimulation current threshold.

12. The method of claim 11, wherein the nerve monitoring system determines the stimulation current threshold by automatically adjusting the intensity of the stimulation signal in response to signals from the EMG electrodes.

13. The method of claim 12, wherein the nerve monitoring system successively doubles the intensity of the stimulation signal until the EMG electrodes detect a response greater than a magnitude establishing a range that contains the stimulation current threshold.

14. The method of claim 13, wherein the nerve monitoring system repeatedly bisects the range until a predetermined accuracy is reached.

15. The method of claim 14, wherein the stimulation current threshold is determined to be the midpoint of the final range.

16. The method of claim 12, wherein the nerve monitoring system determines the stimulation current threshold associated with muscle exhibiting the lowest stimulation current threshold first.

17. The method of claim 11, wherein the neuromuscular response information further includes a color associated with the stimulation current threshold.

18. The method of claim 11, wherein the color associated with the stimulation current threshold is one from the group of green, yellow, and red.

19. The method of claim 1, wherein the neuromuscular response information is further indicative of nerve direction.

20. The method of claim 1, further comprising after advancing at least one dilator cannula to the targeted intervertebral disc of the spine, advancing a guide wire through a lumen of the dilator cannula so that the guide wire penetrates an annulus of the targeted intervertebral disc of the spine.

21. The method of claim 1, wherein the diameters of the dilating cannula are from the range of 6 mm to 30 mm.