Electromagnetic apparatus and method for nerve localization during spinal surgery

• US 8,052,688 B2
• Filed: 08/28/2007
• Issued: 11/08/2011
• Est. Priority Date: 10/06/2006
• Status: Expired due to Fees

• Current Assignee: Erich Wolf II
• Original Assignee: Erich Wolf II
• Inventors: Wolf, Erich II
• Primary Examiner(s): Barrett; Thomas C.
• Assistant Examiner(s): SEVILLA, CHRISTIAN ANTHONY
• Application Number:
  US11/897,169
• Publication Number:
  US 20080086140A1
• Time in Patent Office: 1,533 Days
• Field of Search: 600/546, 600/554, 606/33, 606/80, 606/79, 606/96, 606/104, 607/117, 607/48
• US Class Current: 606/80
• CPC Class Codes: A61B 17/1671 for the spine
• CPC Class Codes: A61B 17/1703 using imaging means, e.g. by X-rays
• CPC Class Codes: A61B 2017/00039 Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect
• CPC Class Codes: A61B 2017/00154 pulsed
• CPC Class Codes: A61B 5/05 Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves impedance plethysmography A61B5/0295; measuring movement of the entire body or parts thereof A61B5/11; detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof A61B5/24
• 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 5/4041 Evaluating nerves condition
• CPC Class Codes: A61B 5/4836 Diagnosis combined with treatment in closed-loop systems or methods A61B5/0036 takes precedence
• CPC Class Codes: A61N 1/0551 Spinal or peripheral nerve electrodes

Abstract

An electromagnetic pedicle awl utilizes a tightly focused time-varying magnetic flux to create a localized electromotive force (EMF) near the tip of a pedicle awl. The localized EMF creates localized eddy currents in nearby nerves which in turn excite ionic nerve channels, the excitation being detected by an electromyographic recording device. In comparison to the electrically stimulated pedicle awl of the prior art, the electromagnetic pedicle awl only excites nerves directly in front of and directly to the side of the tip. The electromagnetic pedicle awl is comprised of a tapered awl or drill tip in combination with a solid core surrounded by a solenoid. A pulsed electric current source drives the solenoid to create a time-varying magnetic field in the vicinity of the tapered tip. The awl or drill tip may be stationary with respect to the solenoid or it may rotate. The electromagnetic pedicle awl in combination with an EMG detector connected to a patient is very sensitive to the pedicle hole position with respect to adjacent nerves and reduces false placement failure.

Claims

1. A surgical awl for use in surgical procedures comprising:

a solid core having a first end and a second end;

a tapered awl tip attached to the first end of the solid core;

a handle attached to the second end of the solid core;

an electrically conductive coil around the solid core;

an electric current source, connected to the electrically conductive coil, capable of producing a time varying electrical signal;

the time varying electrical signal producing a time varying magnetic field in the conductive coil adjacent the awl tip;

the time varying magnetic field of an intensity to produce an electronically measurable excitation a set of living nerve cells; and

,

a detector for monitoring a set of muscles for the electronically measurable excitation.

2. The surgical awl of claim 1 wherein the solid core is non-conductive.

3. The surgical awl of claim 1 wherein the solid core is ceramic.

4. The surgical awl of claim 1 wherein the awl tip is fixed with respect to the conductive coil.

5. The surgical awl of claim 1 further comprised of a quick disconnect for attaching the handle to the solid core.

6. The surgical awl of claim 1 wherein the magnitude of the electric signal is adjustable.

7. The surgical awl of claim 1 wherein the electric signal automatically varies with time.

8. The surgical awl of claim 7 wherein the electric signal is one of the group of bipolar alternating, critically damped, or overdamped.

9. The surgical awl of claim 7 wherein the electric signal is pulsed.

10. The surgical awl of claim 1 wherein the detector is an electromyograph connected to the set of muscles.

11. The surgical awl of claim 10 wherein the set of muscles includes one of the group of vastus lateralis muscle, medial gastrocnemius muscle, or tibialis anterior muscle.

12. The surgical awl of claim 1 wherein the time varying magnetic field induces a time varying electric field that exceeds a rheobase value associated with the set of living nerve cells.

13. The surgical awl of claim 1 wherein the solid core is rotatably connected to the conductive coil.

14. The surgical awl of claim 1 wherein the awl tip includes a slot for reducing eddy currents.

15. The surgical awl of claim 1 wherein the conductive coil is covered with a shield of high dielectric strength.

16. The surgical awl of claim 1 wherein the conductive coil includes a set of full windings and a set of return windings adjacent the tapered awl tip.

17. The surgical awl of claim 1 wherein the surgical procedure is creating a hole in a pedicle.

18. The surgical awl of claim 1 wherein the surgical procedure is creating a passageway through a psoas muscle.

19. The surgical awl of claim 1 wherein the time varying magnetic field obeys the equation

20. A surgical awl tool for creating a pilot hole in bony material proximate to nerve cells, the tool capable of producing magnetic fields comprised of:

a solid core bushing;

a tapered drill, having a drill tip and a cylindrical shaft, the cylindrical shaft resident in the solid core bushing so that a portion of the cylindrical shaft protrudes axially from the solid core bushing;

the cylindrical shaft having a reverse thrust bearing attached near the tapered drill and set against the solid core bushing;

the cylindrical shaft having a forward thrust bearing attached to the cylindrical shaft and set against the end of the solid core bushing so as not to allow lateral movement of the tapered drill with respect to the solid core bushing;

a coil assembly for producing a magnetic field further comprised of a conductive coil of wire around the solid core bushing;

an electric current source attached to the conductive coil of wire so that a time varying magnetic field is capable of being generated in the vicinity of the drill tip of an intensity sufficient to produce an electronically measurable excitation of the nerve cells; and

,

a mechanism for detecting the excitation of the nerve cells by the time varying magnetic field as the drill tip penetrates the bony material.

21. The surgical awl of claim 20 wherein the drill tip is capable of rotation with respect to the solenoid assembly.

22. The surgical awl of claim 20 wherein the cylindrical shaft is rigidly attached to a gripping handle.

23. The surgical awl of claim 20 wherein the shaft is attached to a robot end effector.

24. The surgical awl of claim 20 wherein the solid core bushing is non-conductive.

25. The surgical awl of claim 20 wherein the electric current source produces a signal that varies with time.

26. The surgical awl of claim 25 wherein the signal is one of the group of critically damped, overdamped or bipolar alternating pulsed current.

27. The surgical awl of claim 20 wherein the mechanism is an electromyograph.

28. A surgical awl for use in surgical procedures comprising:

a hollow cylindrical core having a first end and a second end;

a tapered awl tip attached to the first end of the hollow cylindrical core;

a handle attached to the second end of the hollow cylindrical core;

an electrically conductive coil around the hollow cylindrical core;

an electric current source, connected to the electrically conductive coil, producing a time varying electrical signal;

the time varying electrical signal producing a time varying magnetic field in the conductive coil adjacent the awl tip;

the time varying magnetic field of an intensity to produce an electrically measurable excitation in a set of living nerve cells; and

,

a detector for monitoring a set of muscles for the electrically measurable excitation.

29. The surgical awl of claim 28 wherein the time varying magnetic field obeys the equation

30. The surgical awl of claim 28 wherein the hollow cylindrical core is non-conductive.

31. The surgical awl of claim 28 wherein the hollow cylindrical core is ceramic.

32. The surgical awl of claim 28 wherein the tapered awl tip is fixed with respect to the electrically conductive coil.

33. The surgical awl of claim 28 further comprised of a quick disconnect for attaching the handle to the hollow cylindrical core.

34. The surgical awl of claim 28 wherein the magnitude of the electric signal is adjustable.

35. The surgical awl of claim 28 wherein the electric signal automatically varies with time.

36. The surgical awl of claim 35 wherein the electric signal is one of the group of bipolar alternating, critically damped and overdamped.

37. The surgical awl of claim 35 wherein the electric signal is pulsed.

38. The surgical awl of claim 28 wherein the detector is an electromyograph connected to a set of muscles.

39. The surgical awl of claim 38 wherein the set of muscles includes one of the group of vastus lateralis muscle, medial gastrocnemius muscle and tibialis anterior muscle.

40. The surgical awl of claim 28 wherein the hollow cylindrical core is rotatably connected to the conductive coil.

41. The surgical awl of claim 28 wherein the tapered awl tip includes a slot for reducing an eddy current.

42. The surgical awl of claim 28 wherein the electrically conductive coil is covered with a shield of high dielectric strength.

43. The surgical awl of claim 28 wherein the electrically conductive coil includes a set of full windings and a set of return windings adjacent the tapered awl tip.

44. The surgical awl of claim 28 wherein the surgical procedure is creating a hole in a pedicle.

45. The surgical awl of claim 28 wherein the surgical procedure is creating a passageway through a psoas muscle.

46. The surgical awl of claim 28 further comprising:

an outer casing adjacent the electrically conductive coil; and

,

a faraday shield integrated into the outer casing.