Recess drive bone screw and cooperable driving tool

• US 6,016,727 A
• Filed: 12/21/1998
• Issued: 01/25/2000
• Est. Priority Date: 02/28/1997
• Status: Expired due to Term

• Current Assignee: Sofamor Danek Properties, Inc. (Medtronic Plc)
• Original Assignee: Sofamor Danek Properties, Inc. (Medtronic Plc)
• Inventors: Morgan, Frank H.
• Primary Examiner(s): Smith, James G.
• Application Number:
  US09/217,108
• Time in Patent Office: 400 Days
• Field of Search: 81/436, 81/461, 411/403, 606/72, 606/73
• US Class Current: 81/436
• CPC Class Codes: A61B 17/8615 at the central region of the screw head
• CPC Class Codes: A61B 17/888 the driver bit acting on the central region of the screw head
• CPC Class Codes: A61B 17/8888 at its central region
• CPC Class Codes: B25B 15/005 with cross- or star-shaped cross-section
• CPC Class Codes: B25B 15/008 Allen-type keys
• CPC Class Codes: F16B 23/0038 substantially prismatic with up to six edges, e.g. triangular, square, pentagonal, Allen-type cross-sections
• CPC Class Codes: Y10S 606/907 Composed of particular material or coated
• CPC Class Codes: Y10S 606/916 Tool for installing or removing orthopedic fastener

Abstract

A fastener with a recessed drive socket and a driving tool with a cooperable driving head. The socket having a cylindrical interior wall interrupted by a plurality of driving corners. The driver having a tapered driving head including a plurality of sharpened driving edges adapted to engage the driving corners. The tapered driving end may be axially forced into the driving socket such that the plurality of driving edges frictionally engage the driving corners to hold the fastener on the driver and to enhance torque transmission. The cylindrical walls of the socket and the walls of the driver bit between the driving edges cooperate to define a fluid channel for passage of fluid around the driving head during positioning within the socket.

Claims

1. A bone screw for attaching an implant to a bone portion, the bone screw comprising a head adapted to engage an implant and a threaded shaft configured for engaging the bone portion, wherein the head includes a recessed drive socket for receiving a partially mating, rotational drive tool therein, wherein the socket comprises a socket cavity having a generally cylindrical wall having a longitudinal length, said cylindrical wall substantially smooth throughout said longitudinal length and interrupted by a plurality of pre-formed driving corners formed by a pair of substantially planar surfaces joined at a junction, each surface abutting the cylindrical wall, wherein said driving corners receive a portion of the driver tool therein.

2. The bone screw of claim 1, wherein said plurality of driving corners are spaced equidistant around said cylindrical wall.

3. The bone screw of claim 1, wherein each of said plurality of driving corners is a recessed area in said cylindrical wall.

4. The bone screw of claim 1, wherein said series of driving corners includes six equally spaced recesses defined in said cylindrical wall.

10. The bone screw of claim 1 wherein the threaded shaft has an outer diameter of about 1.0 mm to about 5.0 mm.

12. The bone screw of claim 1 wherein the driving corners are spaced apart by a plurality of concave surfaces.

13. The bone screw of claim 1 wherein the bone screw includes a longitudinal axis and the driving comers extend longitudinally essentially parallel to the longitudinal axis of the bone screw.

5. A bone screw and driver combination, comprising:

a bone screw having a drive socket, said socket having a substantially cylindrical wall having a longitudinal length, said wall substantially smooth throughout said longitudinal length, and a plurality of pre-formed driving corners formed by a pair of substantially planar surfaces joined at a junction, each surface abutting the cylindrical wall; and

a driver having a driving head including a plurality of driving edges sized for mating engagement with corresponding driving corners of said bone screw, said driving head further defining a recessed area between each driving edge.

6. The bone screw and driver combination of claim 5, wherein said driving head has an external diameter, a proximal portion and a distal tip, said external diameter tapering between a first diameter adjacent said proximal portion and a second diameter adjacent said distal tip, said first diameter being larger than said second diameter, wherein upon insertion of said driver head into said recessed drive socket said driving head may be advanced until a portion of said driving edges having a third diameter intermediate said first and second diameters abuttingly engage said driving corners.

7. The bone screw and driver combination of claim 6, wherein said driver is made of a first material and said fastener is made of a second material, said first material being harder than said second material, and wherein further axial movement of said driver into said fastener after abutting engagement results in a deformation of said driving corners, said deformation enhancing frictional engagement of said driver in said fastener.

8. The bone screw and driver combination of claim 7, wherein said first material is heat treated stainless steel and said second material is a titanium alloy, wherein deformation of said titanium alloy work hardens the material resulting in greater mechanical strength.

11. The bone screw and driver combination of claim 5 wherein the bone screw has an outer thread diameter of about 1.0 mm to about 5.0 mm.

9. A bone screw and driver combination, comprising:

a bone screw having a recessed drive socket, said socket defined by a substantially cylindrical interior wall having a longitudinal length, said interior wall substantially smooth throughout said longitudinal length and interrupted by a plurality of driving corners formed by a pair of substantially planar surfaces joined at a junction, each surface abutting the cylindrical interior wall,

a driver having a driving head including an outer surface defining a plurality of driving edges spaced for mating engagement with the corresponding driving corners of said bone screw, said cylindrical interior wall of said bone screw and said outer surface of said driver define at least one fluid channel, said fluid channel permitting the passage of fluid during movement of said driver with respect to said recessed drive socket.

14. The bone screw and driver combination of claim 9 wherein the fluid channel permits passage of bodily fluids.

15. The bone screw and driver combination of claim 9 wherein the fluid channel is sized to inhibit hydraulic lock of the driver by bodily fluids.

16. The bone screw of claim 9 wherein the bone screw includes a longitudinal axis and the driving comers extend longitudinally essentially parallel to the longitudinal axis of the screw.

17. A bone screw and driver combination, comprising:

a bone screw having a recessed drive socket, said socket defined by a plurality of driving corners formed by a pair of substantially planar surfaces joined at a junction, each of said driving corners separated from an adjacent driving corner by a concave surface having a longitudinal length, said concave surface substantially smooth throughout said longitudinal length, each substantially planar surface abutting a concave surface; and

a driver having a driving head including an outer surface defining a plurality of driving edges spaced apart by a plurality of recessed surfaces, wherein the driving edges are provided for mating engagement with the driving corners of said bone screw and the recessed surfaces are adapted to prevent complete engagement of said driving head with said concave surface.

18. The bone screw and driver combination of claim 17 wherein upon engagement of said driving edges with said driving corners, portions of said concave surfaces and said recessed surfaces define a plurality of fluid channels to permit passage of bodily fluids from the recessed drive socket when the driving edges engage the driving corners.

19. The bone screw and driver combination of claim 17 wherein said concave surfaces are cylindrical wall portions.

20. The bone screw and driver combination of claim 19 wherein the recessed surfaces are positioned opposite the cylindrical wall portions when the driving edges matingly engage the driving corners.

21. A bone screw for attaching an implant to a bone portion, the bone screw comprising:

a threaded shaft configured for engaging the bone portion and having an outer thread diameter of between about 1.0 mm and about 5.0 mm; and

a head adapted to engage an implant, wherein the head includes a recessed drive socket for receiving a partially mating, rotational drive tool therein, the socket comprising a socket cavity having a generally cylindrical wall having a longitudinal length, said cylindrical wall substantially smooth throughout said longitudinal length and interrupted by a plurality of pre-formed driving corners formed by the junction of a pair of substantially planar surfaces each surface abutting the cylindrical wall, said driving corners spaced apart by a plurality of concave surfaces, wherein the concave surfaces are adapted to inhibit hydraulic lock by bodily fluids from inducing bone screw pullout upon disengagement of the drive tool from the recessed socket.