Minimal shock set screw

Patent metadata

Field	Value
Publication number	US-2016367303-A1
Application number	US-201415116363-A
Country	US
Kind code	A1
Filing date	Dec 15, 2014
Priority date	Dec 13, 2013
Publication date	Dec 22, 2016
Grant date	—

Abstract

The present invention is generally directed to a reduced shock breakaway screw for use with medical implants and the like having improved solid wall geometry in the breakaway area between the upper and lower portions of the set screw. This improved geometry serves to slow down the fracturing process during shearing, thereby increasing the proportion of energy dissipated as heat from plastic deformation of the material to the amount of energy released as kinetic energy from elastic rebound.

First claim

What is claimed is:

1 . A reduced shock breakaway screw comprising:
an upper head portion having a top surface and configured to mate with a first torque applying device; a lower threaded screw portion configured to mate with a second torque applying device; a substantially annular groove separating said upper head portion from said lower threaded screw portion and defining a breakaway region; a central axis running from the top of said upper head portion to the bottom of said lower threaded screw portion; and a center hole running from the top of said upper head portion through said breakaway region and to or into said lower threaded screw portion; wherein said upper head portion will separate from said lower threaded screw portion upon application of a predetermined torque to said upper head portion.

2 . The reduced shock breakaway screw of claim 1 wherein:
said breakaway region has an inner diameter defined by the diameter of said center hole and an outer diameter defined by a bottom of said substantially annular groove; and
the inner diameter comprises from about 0.4% to about 90% of the outer diameter of said breakaway region.

3 . The reduced shock breakaway screw of claim 1 wherein:
said breakaway region has an inner dimension defined by the area of said center hole and an outer dimension defined by the area circumscribed by a bottom of said substantially annular groove; and
the area of the inner dimension comprises from about 0.0016% to about 81% of the outer dimension of said breakaway region.

4 . The reduced shock breakaway screw of claim 1 wherein said upper head portion has a cross sectional shape selected from the group consisting of square, rectangular, pentagonal, hexagonal, octagonal, torx™, and triangular.

5 . The reduced shock breakaway screw of claim 1 wherein said lower threaded screw portion further comprises a nut portion configured to mate with the second torque applying device.

6 . The reduced shock breakaway screw of claim 5 wherein said nut portion has a cross sectional shape selected from the group consisting of square, rectangular, pentagonal, hexagonal, octagonal, torx, and triangular.

7 . The reduced shock breakaway screw of claim 1 wherein said lower threaded screw portion mates with the second torque applying device in such a way as to permit the second torque applying device to apply torque to said lower threaded screw portion without applying significant torque to said upper head portion.

8 . The reduced shock breakaway screw of claim 1 wherein said lower threaded screw portion further comprises one or more recessed openings configured to receive and mate with the second torque applying device.

9 . The reduced shock breakaway screw of claim 1 wherein said lower threaded screw portion is configured to be received in a threaded bore of a surgical construct.

10 . The reduced shock breakaway screw of claim 1 wherein said lower threaded screw portion is configured to be received in a threaded bore located in a pedicle screw head, connector, ring, band clamp, or bone screw cap of a surgical construct for use with the one or more bones of a patient.

11 . The reduced shock breakaway screw of claim 1 wherein said reduced shock breakaway screw is made from a metal selected from the group consisting of titanium alloys, stainless steels, and cobalt-chromium alloys.

12 . A reduced shock breakaway screw comprising:
an upper head portion having a rectangular cross sectional area and configured to mate with a first torque applying device, wherein said upper head portion passes through a central axis of the reduced shock breakaway screw and has a first and second side, the distance between said first and second ends defining a length and the distance between said a first and second sides defining a width; a lower threaded screw portion connected to said upper head portion and having one or more recessed openings configured to mate with a second torque applying device; a first groove running along a bottom edge of the first side of said upper head portion; a second groove running along a bottom edge of the second side of said upper head portion; said first and second grooves defining a breakaway area; wherein said upper head portion will separate from said lower threaded screw portion upon application of a predetermined torque to said upper head portion.

13 . The reduced shock breakaway screw of claim 12 further comprising a first recessed opening in the lower threaded screw portion on a first side of said upper head portion and a second recessed opening in the lower threaded screw portion on a second side of said upper head portion.

14 . The reduced shock breakaway screw of claim 12 wherein said lower threaded screw portion engages the second torque applying device in such a way as to permit the second torque applying device to apply torque to said lower threaded screw portion without applying significant torque to said upper head portion.

15 . The reduced shock breakaway screw of claim 12 further comprising a hole in said upper head portion running between said first and second grooves and passing through the central axis of said reduced shock breakaway screw.

16 . The reduced shock breakaway screw of claim 12 wherein the breakaway area has a substantially hour glass shape with its narrowest point at or near the central axis of said reduced shock breakaway screw.

17 . The reduced shock breakaway screw of claim 16 further comprising a hole in said upper head portion running between said first and second grooves and passing through the central axis of said reduced shock breakaway screw.

18 . The reduced shock breakaway screw of claim 12 wherein said lower threaded screw portion is configured to be received in a threaded bore of a surgical construct for use with one or more bones of a patient.

19 . The reduced shock breakaway screw of claim 12 further comprising a center hole running along the central axis of said reduced shock breakaway screw from the top of said upper head portion through said breakaway region and to or into said lower threaded screw portion.

Assignees

• Mahajan Ajay
• King Jason
• Norman Greg
• Paul Tim
• Univ Akron

Inventors

• Mahajan Ajay
• King Jason
• Norman Greg
• Paul Tim

Classifications

• A61B17/8875

  Screwdrivers, spanners or wrenches · CPC title

• A61B2090/037

  with a frangible part, e.g. by reduced diameter · CPC title

• A61B17/7001

  Screws or hooks combined with longitudinal elements which do not contact vertebrae (A61B17/7058 takes precedence) · CPC title

• A61B17/8615 Primary

  at the central region of the screw head · CPC title

• A61B17/86 Primary

  Pins or screws {or threaded wires; nuts therefor (A61B17/72 take precedence)} · CPC title