Procedure for spinal pedicle screw insertion

• US 5,196,015 A
• Filed: 04/30/1992
• Issued: 03/23/1993
• Est. Priority Date: 04/30/1992
• Status: Expired due to Term

• Current Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Original Assignee: Seth L. Neubardt
• Inventors: Neubardt, Seth L.
• Primary Examiner(s): Hafer, Robert A.
• Assistant Examiner(s): BROWN, MICHAEL A
• Application Number:
  US07/876,861
• Time in Patent Office: 327 Days
• Field of Search: 606/60, 606/61, 606/64, 606/65, 606/66, 606/67, 606/68, 606/72, 606/73, 606/74, 606/75, 606/76
• US Class Current: 600/554
• CPC Class Codes: A61B 17/1655 for tapping
• 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 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 17/8875 Screwdrivers, spanners or wrenches
• CPC Class Codes: A61B 2017/00039 Electric or electromagnetic phenomena other than conductivity, e.g. capacity, inductivity, Hall effect

Abstract

Pedicle screws are inserted in spinal vertebrae in a manner to reduce the likelihood of nerve damage caused by improper screw placement. A screw opening is started in part of a skeletal region, e.g., a pedicle of a lumbar vertebra and an electric potential of a certain magnitude is applied to the inner surface of the opening while the patient is observed for nervous reactions such as leg twitching. The opening continues to be formed while the electric potential is applied until a desired hole depth is obtained in the absence of nervous reaction to the potential. The direction in which the screw opening is being formed is changed to a direction other than the last direction, after observing patient reactions to the electric potential when the screw opening was being formed in the last direction. A tool for carrying out the procedure includes a handle and a probe tip extending from the handle for forming an opening in bone tissue. Stimulator circuitry arranged inside the handle produces an electric potential of a predetermined level, and the potential is applied to the probe tip while the tool handle is manipulated to urge the probe tip into the bone tissue.

Claims

1. A technique of inserting a screw member into bone tissue, the screw member being part of a spinal fixation instrument system wherein rigid rods or plates are attached to heads of a number of screw members after insertion into adjacent parts of the bone tissue, said technique comprising the steps of:

making an incision in a patient and exposing a skeletal region for which region a bone fixation procedure is to be performed;

locating an entrance point on a part of the skeletal region into which part a screw member of a spinal fixation instrument system is to be inserted;

forming a screw opening in said part of the skeletal region for insertion of the screw member, using a determined direction for formation of the opening;

applying an electric potential of a certain magnitude to the inner surface of said opening while observing the patient for nervous reactions to said electric potential;

continuing said forming step and said applying step until a desired depth is attained for the screw opening in the absence of nervous reactions of the patient to said electric potential; and

redirecting the formation of said screw opening in a direction other than a last determined direction after observing nervous reactions of the patient to said electric potential when forming the screw opening in the last determined direction.

2. The technique of claim 1, including observing twitching of a limb of the patient as a nervous reaction for initiating such redirecting step.

3. The technique of claim 1, including carrying out said forming and said applying steps substantially simultaneously using a single tool.

4. The technique of claim 3, including using a tool having a pointed probe tip for forming the screw opening.

5. The technique of claim 3, including using a tap driver tool for forming the screw opening.

6. The technique of claim 3, including using a screw head driver tool for forming the screw opening by driving a screw member into the bone tissue.

7. The technique of claim 1, including setting the magnitude of the electric potential in said applying step to a level at which nervous reactions are observed when the potential is applied in proximity to a nerve root adjacent the screw opening.

8. The technique of claim 1, including setting the magnitude of the electric potential in said applying step to a level at which nervous reactions are observed when the potential is applied on a nerve root adjacent the screw opening.