Method for subcutaneous suprafascial pedicular internal fixation

• US 5,171,279 A
• Filed: 03/17/1992
• Issued: 12/15/1992
• Est. Priority Date: 03/17/1992
• Status: Expired due to Term

• Current Assignee: SDGI Holdings Incorporated (Medtronic Plc)
• Original Assignee: Danek Medical, Inc.
• Inventors: Mathews, Hallett H.
• Primary Examiner(s): SHAY, RANDY CITRIN
• Application Number:
  US07/852,577
• Time in Patent Office: 273 Days
• Field of Search: 128/898, 623/17, 606/60, 606/61, 606/54
• US Class Current: 128/898
• CPC Class Codes: A61B 17/70 Spinal positioners or stabilisers ; Bone stabilisers comprising fluid filler in an implant
• CPC Class Codes: A61B 17/7007 Parts of the longitudinal elements, e.g. their ends, being specially adapted to fit around the screw or hook heads
• CPC Class Codes: A61B 17/7049 Connectors, not bearing on the vertebrae, for linking longitudinal elements together A61B17/7055, A61B17/7053, A61B17/7019 take precedence
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence
• CPC Class Codes: A61F 2/442 Intervertebral or spinal discs, e.g. resilient non-disc-shaped intervertebral inflatable pockets A61F2/441; non-disc-shaped intervertebral fusion implants A61F2/4455
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2002/2835 Bone graft implants for filling a bony defect or an endoprosthesis cavity, e.g. by synthetic material or biological material
• CPC Class Codes: A61F 2002/2839 Bone plugs or bone graft dowels
• CPC Class Codes: A61F 2002/30329 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
• CPC Class Codes: A61F 2002/448 comprising multiple adjacent spinal implants within the same intervertebral space or within the same vertebra, e.g. comprising two adjacent spinal implants
• CPC Class Codes: A61F 2002/449 comprising multiple spinal implants located in different intervertebral spaces or in different vertebrae
• CPC Class Codes: A61F 2220/0025 Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements

Abstract

A method for internal fixation of vertebra of the spine to facilitate graft fusion includes steps for excising the nucleus of an affected disc, preparing a bone graft, instrumenting the vertebrae for fixation, and introducing the bone graft into the resected nuclear space. Disc resection is conducted through two portals through the annulus, with one portal supporting resection instruments and the other supporting a viewing device. The fixation hardware is inserted through small incisions aligned with each pedicle to be instrumented. The hardware includes bone screws, fixation plates, engagement nuts, and linking members. In an important aspect of the method, the fixation plates, engagement nuts and linking members are supported suprafascially but subcutaneously so that the fascia and muscle tissue are not damaged. The bone screw is configured to support the fixation hardware above the fascia. In a further aspect of the invention, a three component dilator system is provided for use during the bone screw implantation steps of the method.

Claims

1. A method for internal fixation of the spine comprising the steps of:

a) inserting a guide pin into a pedicle of at least two vertebrae to be instrumented for internal fixation;

b) making an incision in the skin at the entry site for each guide pin;

c) dissecting subcutaneous suprafascial tissue between each entry site;

d) initially advancing a bone screw over each guide pin through each incision and into each pedicle, the bone screw having bone engaging threads and machine threads for engaging a nut;

e) elevating the skin between each entry site;

f) inserting a fixation plate into the subcutaneous suprafascial space and supporting the plate on and between at least two bone screws with the machine threaded portion projecting above the plate; and

g) clamping the fixation plate to the bone screws using nuts engaging the machine threaded portions of the bone screws with the fixation plate supported above the fascia and muscle tissue but beneath the skin of the patient.

2. The method for internal fixation of the spine of claim 1, further comprising the following steps between the plate insertion and clamping steps:

loosely engaging a nut on the nut threaded portion of each of the bone screws; and

further advancing each bone screw deeper into the respective pedicle until the fixation plate lies immediately adjacent the fascia.

3. The method for internal fixation of the spine of claim 1, wherein:

each of the steps (a)-(g) is repeated on opposite sides of the spinous process for bilateral instrumentation of each pedicle of each vertebrae.

4. The method for internal fixation of the spine of claim 3, further comprising the steps of:

dissecting subcutaneous suprafascial tissue between the ipsilateral and contralateral bone screws at each level of instrumentation of the vertebrae; and

after the step of inserting the fixation plate, inserting a linking member between bilateral bone screws at the same level of instrumentation with the machine threaded portion of the bone screws projecting above the linking member.

5. The method for internal fixation of the spine of claim 1, wherein the step of advancing the bone screw includes the steps of:

advancing a cannulated drill bit over each guide pin; and

using the drill bit, drilling into the pedicle to a predetermined depth less than the length of the bone engaging threads of the bone screw.

6. The method for internal fixation of the spine of claim 5, wherein:

in the drilling step the predetermined depth is about one-third of the pedicle depth; and

in the step of initially advancing the bone screw, the bone screw is advanced into at least one-half of the pedicle depth.

7. The method for internal fixation of the spine of claim 1, wherein the step of advancing the bone screw includes the steps of:

dilating the tissue at each entry site using three dilators having successively larger diameters;

removing the smallest dilator;

advancing a cannulated drill bit over each guide pin through an intermediate dilator; and

using the drill bit, drilling into the pedicle to a predetermined depth less than the length of the bone engaging threads of the bone screw.

8. The method for internal fixation of the spine of claim 7, wherein the step of advancing the bone screw further includes the subsequent steps of:

removing the intermediate dilator, leaving the largest diameter dilator; and

advancing the bone screw over the guide pin and through the largest dilator.