Tools – Wrench – screwdriver – or driver therefor – Stud-removal and implacement
Reexamination Certificate
1998-11-20
2001-07-31
Smith, James G. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Stud-removal and implacement
C081S120000
Reexamination Certificate
active
06267025
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a tool for extracting broken or damaged screws embedded in bone or wood. Pedicle screws are screws that are inserted into the pedicle of a human vertebra to secure a plate or the like to an adjacent vertebra. As with all screws, they may be damaged or broken during installation or through wear, requiring removal.
Prior art approaches to removal of damaged screws include using a plurality of sharp teeth in a tool to hold the metal of the screw while turning as shown in U.S. Pat. No. 2,750,821 to Hilsinger, a modified slotted blade with sharp leading edges as shown in U.S. Pat. No. 4,434,687 to Vickio or a tool that requires drilling a bore down the center of the damaged screw or bolt to receive a reverse threaded or fluted tool, commonly called an “easy-out” as shown in U.S. Pat. No. 1,547,944 to Murphree. U.S. Pat. No. 4,350,064 to Markle issued Sep. 21, 1982, shows a more recent approach in which an easy out is attachable to an electric drill or rachet wrench.
In medical applications, it may be very difficult to use an easy-out in that drilling a pilot hole generates metal filings which cannot be allowed to be left in the surgical site, especially in the vicinity of the spinal cord. A tool that will not require drilling and that would not generate metal fragments is highly desirable.
The art described in this section is not intended to constitute an admission that any patent, publication, or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. § 1.56(a) exists.
BRIEF SUMMARY OF THE INVENTION
The invention provides a screw extractor, especially suited for medical applications such as removal of pedicle screws. The screw extractor has an elongated shaft with an upper and a lower end. The upper end is adapted to receive a source of rotational force. The lower end includes a central opening which includes tapered threads opposite the threads of a screw to be removed. The lower periphery of the end defines a hole saw to cut away the bone or wood into which the screw is inserted.
In operation, the extractor is positioned over the screw to be removed and is rotated allowing the hole saw to cut away the bone or wood surrounding the screw until the inner tapered threads bite into the screw enough that it may be rotated out of the substrate.
REFERENCES:
patent: 3106233 (1963-10-01), Wolny
patent: 3457812 (1969-07-01), Wagner
patent: 4204308 (1980-05-01), Marling
patent: 4940370 (1990-07-01), Gipson
patent: 5737981 (1998-04-01), Hildebrand
Sand Paul M.
Shinbrot Adam
Smith James G.
Sulzer Spine-Tech Inc.
Vidas Arrett & Steinkraus
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