Anterior cervical plate and fixation system

• US 6,258,089 B1
• Filed: 05/19/1999
• Issued: 07/10/2001
• Est. Priority Date: 05/19/1998
• Status: Expired due to Term

• Current Assignee: Alphatec Spine Incorporated (Alphatec Holdings Incorporated)
• Original Assignee: Alphatec Manufacturing, Inc.
• Inventors: Campbell, Christopher M., Tokish, Leonard J. Jr., Anselm, Donald E., Blain, Jason D., Pastrick, Dan L., Bales, Joel P., Ramirez, George A., Delamarter, Rick B.
• Primary Examiner(s): Hirsch, Paul J.
• Assistant Examiner(s): Priddy, Michael B.
• Application Number:
  US09/314,617
• Time in Patent Office: 783 Days
• Field of Search: 623/16, 623/17, 606/60, 606/61, 606/69, 606/72, 606/73
• US Class Current: 606/86.00B
• CPC Class Codes: A61B 17/7059 Cortical plates A61B17/7007, A61B17/7058 take precedence
• CPC Class Codes: A61B 17/8042 the additional component being a cover over the screw head
• CPC Class Codes: A61B 17/8052 immobilised relative to screws by interlocking form of the heads and plate holes, e.g. conical or threaded
• CPC Class Codes: A61B 17/862 at the periphery of the screw head
• CPC Class Codes: A61B 17/8891 at its periphery

Abstract

An anterior cervical plate is disclosed, along with threaded fasteners for securing the plate to vertebrae or other osseous material. The cervical plate has several pockets or apertures, preferably at least four, to receive a corresponding number of the fasteners. The pockets have spherical surfaces, and the fasteners have heads with similarly sized spherical surfaces, which when engaged permit each of the fasteners to be oriented at a variety of projection angles with respect to the plate. In connection with each pocket, the cervical plate incorporates a fastener retaining feature. The feature can take the form of a cantilevered tab or a beam supported at its opposite ends, in each case plastically deformable between an open position for admitting the fastener and a closed position for preventing retraction.

Claims

1. An appliance attachable to osseous material within a body, including:

a biocompatible structural member having an exterior surface including opposite first and second exterior surface regions, and an interior surface region between said exterior surface regions defining a first aperture through the structural member;

a biocompatible first fastener including an elongate longitudinal shank and a head larger in diameter than the shank, said shank adapted for a insertion through the first aperture and a penetration into osseous material to a depth sufficient to bring the first exterior surface region into a surface engagement with the osseous material while the head engages the interior surface region and thereby tends to maintain said surface engagement to fix the structural member substantially integrally to the osseous material; and

a first retaining element permanently fixed to the structural member and movable from an open position for allowing travel of the head into the first aperture and against the interior surface region, to a closed position for maintaining the head against the interior surface region.

2. The appliance of claim 1 wherein:

the first retaining element is resilient and ductile, and movable from the open position to the closed position by applying an external force above an elastic limit thereof.

3. The appliance of claim 2 wherein:

said retaining element comprises a tab supported by the structural member and extending therefrom in cantilevered fashion.

4. The appliance of claim 2 wherein:

the retaining element comprises an elongate member attached at two opposite ends to the structural member.

5. The appliance of claim 1 wherein:

said first retaining element is elastic, normally tending to assume the closed position, and elastically deformable into the open position when subject to an external force.

6. The appliance of claim 1 wherein:

the first exterior surface region and the second exterior surface region are substantially parallel to one another.

7. The appliance of claim 6 wherein:

the head, when maintained in the first aperture against the interior surface region, is substantially contained between the first and second exterior surface regions.

8. The appliance of claim 1 wherein:

the shank is externally threaded, the head incorporates a non-circular recess for receiving a drive tool used to turn the fastener.

9. The appliance of claim 1 wherein:

the aperture is sized with respect to the shank to allow a pivoting of the first fastener with respect to the structural member about at least one transverse axis disposed between the first and second exterior surface regions when the head is in the aperture.

10. The appliance of claim 9 wherein:

the first fastener is pivotable about all transverse axes passing through a given point between the first and second exterior surface regions, thereby defining a conical volume within which the first fastener is selectively positionable.

11. The appliance of claim 10 wherein:

said interior surface region includes a spherical segment, and said head has a spherical surface portion in contact with the spherical segment.

12. The appliance of claim 1 further including:

a second fastener substantially identical to the first fastener, and a second aperture formed though the structural member for receiving a head of the second fastener when a shank thereof is inserted through the second aperture.

13. The appliance of claim 12 wherein:

the first and second apertures are disposed near opposite ends of the structural member, the osseous material comprises two vertebrae, and wherein the structural member is positionable with respect to the vertebrae such that the first and second fasteners are extendible through the first and second apertures respectively and into different ones of the vertebrae, and cooperate with the structural member to support the vertebrae substantially integrally with respect to one another.

14. The appliance of claim 1 wherein:

said biocompatible structural member is unitary, and the first retaining element is formed as part of the unitary biocompatible structural member.

15. The appliance of claim 1 wherein:

said first retaining element further is movable from the closed position to the open position to allow a removal of the head from the first aperture, thus to allow a withdrawal of the first fastener from the osseous material and the structural member.

16. An apparatus for fixing a body insertable member to bony material, including:

a biocompatible structural member having an exterior surface that includes a first surface region adapted for surface engagement with a bony material when the structural member is secured to the bony material, and a second surface region opposite the first surface region;

a first fastener comprising an elongate shank extending in a longitudinal direction and having a transverse shank diameter, and further including a head having a transverse head dimension larger than the shank diameter;

an interior wall defining a first aperture formed through the structural member, including a first constriction proximate the first surface region selectively sized with respect to the first fastener to allow passage of the shank through the aperture and first constriction while preventing such passage of the head to maintain the head within the aperture, said first constriction further being of sufficient size to allow a pivoting of the first fastener with respect to the structural member about at least one transverse axis, thereby to allow the selection of a penetration angle at which the shank is inserted into the bony material to secure the structural member; and

a head retaining feature integral with the structural member, disposed near the first aperture and proximate the second surface region, and adapted to cooperate with the first constriction to maintain the head in the first aperture;

wherein at least one of said head and said head retaining feature is elastically deformable to allow travel of the head past the head retaining feature into the first aperture.

17. The apparatus of claim 16 wherein:

the head and the constriction are shaped to allow said pivoting about all of the transverse axes passing through a given point within the aperture.

18. The apparatus of claim 17 wherein:

the first fastener is pivotable throughout a conical volume centered on an axis substantially perpendicular to the first surface region near the aperture and intersecting said point.

19. The apparatus of claim 16 wherein:

the interior wall and the head have respective spherical sections engaged with one another when the head is in the aperture.

20. The apparatus of claim 19 wherein:

the interior wall extends between the first and second surface regions.

21. The apparatus of claim 20 wherein:

the spherical sections of the head and the interior wall are substantially concentric, and the center of the spherical sections is disposed between the first and second surface regions, whereby the interior wall further defines the head retaining feature.

22. The apparatus of claim 21 wherein:

the head is elastically deformable to allow the head to travel past the head retaining feature into the aperture.

23. The apparatus of claim 16 wherein:

the head retaining feature maintains the head at least proximate the constriction to prevent withdrawal of the fastener from the aperture.

24. The apparatus of claim 23 wherein:

the head retaining feature comprises a retaining element fixed to the structural member, movable from an open position for allowing travel of the head into the aperture and against the constriction, to a closed position for so maintaining the head.

25. The apparatus of claim 24 wherein:

the retaining element is resilient and ductile, and movable from the open position to the closed position by applying an external force above an elastic limit thereof.

26. The apparatus of claim 24 wherein:

the retaining element is elastic, normally tending to assume the closed position and elastically deformable into the open position when subject to an external force.

27. A bone plate and fixation system, including:

a biocompatible bone plate having an exterior surface including a bone contact surface region adapted for surface engagement with vertebrae;

first and second spaced apart apertures formed through the bone plate, each of the apertures including a constriction proximate the bone contact surface region;

first and second fasteners, each fastener including an elongate shank extending in a longitudinal direction and having a transverse shank diameter, and further including a head having a transverse head dimension greater than the shank diameter;

wherein the constriction in each of the first and second apertures is selectively sized with respect to its associated fastener to allow a passage of the shank of the associated fastener through the aperture while engaging the head to prevent such passage of the head; and

first and second retaining elements permanently fixed to the structural member and associated with the first and second apertures, respectively, each retaining element being movable from an open position for allowing travel of the head of its associated fastener into its associated aperture and against the constriction thereof, to a closed position for maintaining the associated head substantially against the associated constriction.

28. The system of claim 27 wherein:

each of the retaining elements is resilient and ductile, movable from the open position to the closed position by applying an external force that exceeds an elastic limit of the retaining element.

29. The system of claim 28 wherein:

the retaining elements comprise tabs extending from the structural member in cantilevered fashion.

30. The system of claim 28 wherein:

each of the retaining elements comprises an elongate member attached at two opposite ends to the structural member.

31. The system of claim 27 wherein:

each of the retaining elements is elastic, normally tending to assume the closed position and elastically deformable into the open position when subject to an external force.

32. The system of claim 27 wherein:

the exterior surface of the bone plate further includes an outer surface region opposite the bone contact surface region, and the heads, when maintained in their respective apertures against their respective constrictions, are substantially contained between the bone contact surface region and the outer surface region.

33. The system of claim 27 wherein:

the shanks of the fasteners are externally threaded, and the respective heads incorporate non-circular recesses for receiving a drive tool used to turn the fasteners.

34. The system of claim 27 wherein:

the constrictions are of sufficient size to allow a pivoting of their respective fasteners with respect to the structural member, each about at least one transverse axis, thereby to allow the selection of respective penetration angles at which the shanks are inserted into the vertebrae to secure the structural member.

35. The system of claim 34 wherein:

each of the heads and their associated constrictions is shaped to allow said pivoting about all of the transverse axes passing through a given point within the associated aperture.

36. The system of claim 33 further including:

a fastener drive tool having a drive shaft, said shaft having an end region with a non-circular profile corresponding to said non-circular recess in the respective heads.

37. The system of claim 36 further including:

a sleeve substantially coaxial with and surrounding said end of the drive shaft.

38. The system of claim 27 wherein:

the sleeve is removably attached to the drive shaft.

39. The system of claim 38 further including:

a plurality of flexure members at a distal end of the sleeve, for gripping one of the fasteners when said end of the drive shaft is received within its associated recess.

40. The system of claim 27 further including:

a locking tool including a shaft with a locking end positionable against the retaining element and movable to plastically deform the retaining element and thereby move the retaining element into the closed position.

41. The system of claim 27 further including:

a fastener releasing tool having a shaft with a releasing end positionable against the retaining element when the same is in the closed position, and movable to force the retaining element into the open position to allow a withdrawal of the associated fastener.