SPINAL FIXATION SYSTEM

• US 20120046699A1
• Filed: 08/22/2011
• Published: 02/23/2012
• Est. Priority Date: 08/20/2010
• Status: Active Grant

• Current Assignee: K2M, Inc (Stryker Corporation)
• Original Assignee: K2M, Inc (Stryker Corporation)
• Inventors: Jones, Scott, Boachie-Adjei, Oheneba, McClintock, Larry, Strauss, Kevin, Carbone, John
• Granted Patent: US 8,882,817 B2
• Time in Patent Office: Days
• US Class Current: 606/305
• CPC Class Codes: A61B 17/7032 Screws or hooks with U-shaped head or back through which longitudinal rods pass
• CPC Class Codes: A61B 17/7037 wherein pivoting is blocked when the rod is clamped

Abstract

A polyaxial pedicle screw includes a housing, a bone screw member, and an anvil. The bone screw member includes a head and a threaded shaft extending from the head. The head is selectively securable within the housing. The anvil is positionable within the housing adjacent to the head of the bone screw member when the anvil and the head of the bone screw member are positioned within the housing. The anvil may define one or more grooves in an outer surface of the anvil. The groove defines a flap that is flexibly attached to the anvil to enable the anvil to flex an amount sufficient to maintain the head of the bone screw in constant contact with the anvil when the bone screw member is moved relative to the anvil.

Claims

1. A polyaxial pedicle screw, comprising:

a housing;

a bone screw member including a head and a threaded shaft extending from the head, the head being selectively securable within the housing; and

an anvil positionable within the housing adjacent to the head of the bone screw member when the anvil and the head of the bone screw member are positioned within the housing, the anvil defining at least one groove in an outer surface of the anvil, the groove defining at least one flap, the at least one flap being flexibly attached to the anvil to enable the anvil to flex an amount sufficient to maintain the head of the bone screw member in constant contact with the anvil when the bone screw member is moved relative to the anvil.

2. The polyaxial pedicle screw of claim 1, wherein the anvil defines a cavity having a surface with a plurality of radii of curvature to accommodate variously sized rod members.

3. The polyaxial pedicle screw of claim 2, wherein the surface of the cavity defines a first section with a first radius of curvature, a second section with a second radius of curvature, and a third section with a third radius of curvature such that the plurality of radii of curvature defines a compound curve that provides at least two lines of contact on a plurality of different diameter rod members.

4. The polyaxial pedicle screw of claim 1, wherein the outer surface of the anvil has a non-round shape to prevent disorientation of the anvil when positioning a rod member adjacent the anvil.

5. The polyaxial pedicle screw of claim 1, further comprising a set screw positionable within the housing to secure a rod member within the housing adjacent the anvil.

6. The polyaxial pedicle screw of claim 1, wherein the bone screw member is positionable at a plurality of angles relative to the housing when engaged to the housing and securable relative to the housing at a cone angle of up to approximately 80 degrees.

7. The polyaxial pedicle screw of claim 6, wherein the head of the bone screw member includes a first portion and a second portion, wherein only one of the first and second portions enable the head to fit through an opening defined in the housing and the other of the first and second portions maintains the head of the bone screw member within the housing once inserted.

8. The polyaxial pedicle screw of claim 7, wherein one of the first and second portions is cylindrically shaped and the other of the first and second portions is spherically shaped, the cylindrically shaped portion enabling the head to fit through the opening in the housing and the spherically shaped portion maintaining the head of the bone screw member within the housing once inserted.

9. The polyaxial pedicle screw of claim 8, further comprising a cap securable to the housing to prevent the bone screw member from re-orienting to a position in which the cylindrically shaped portion of the screw head is aligned with the housing opening.

10. The polyaxial pedicle screw of claim 9, wherein the housing includes a collar extending therefrom, the collar defining a cut out to facilitate the positioning of the head within the housing, the cap being securable to the collar to cover the cut out after the head of the bone screw member is positioned within the housing.

11. The polyaxial pedicle screw of claim 1, wherein the anvil includes a protuberance on the outer surface of the anvil and the housing defines a slot on an inner surface of the housing, the protuberance and the slot being engagable to maintain the alignment of the anvil with respect to the housing.

12. The polyaxial pedicle screw of claim 1, wherein the head of the bone screw member includes surface texture that frictionally engages with the anvil such that a user applied force is necessary to reposition the bone screw member relative to the anvil when the bone screw member is disposed in engagement with the anvil.

13. A polyaxial pedicle screw comprising:

a bone screw member having a threaded shaft and a head;

a housing positionable on the head of the bone screw member and defining at least one pin channel therethrough;

at least one wedge member positionable within the housing adjacent the head to facilitate the securement of the head of the bone screw member and a rod member within the housing;

the at least one wedge member defining at least one pin pocket in an outer surface thereof; and

at least one pin positionable within the at least one pin channel and the at least one pin pocket to maintain the at least one wedge member within the housing.

14. The polyaxial pedicle screw of claim 13, further comprising a set screw threadably engagable with an inner surface of the housing to secure a rod member adjacent the wedge member.

15. The polyaxial pedicle screw of claim 13, further comprising a first wedge member and a second wedge member, each of the first and second wedge members positionable adjacent the head of the bone screw member.

16. The polyaxial pedicle screw of claim 15, wherein the first wedge member and the second wedge member define a cavity having a surface with a plurality of radii of curvature to accommodate variously sized rod members.

17. The polyaxial pedicle screw of claim 16, wherein the surface of the cavity defines a first section with a first radius of curvature, a second section with a second radius of curvature, and a third section with a third radius of curvature.

18. The polyaxial pedicle screw of claim 13, wherein the bone screw member is positionable at a plurality of angles relative to the housing when engaged to the housing and securable relative to the housing at a cone angle of up to approximately 80 degrees.

19. The polyaxial pedicle screw of claim 13, wherein the head of the bone screw member includes a first portion and a second portion, wherein only one of the first and second portions enable the head to fit through an opening defined in the housing and the other of the first and second portions maintains the head of the bone screw member within the housing once inserted.

20. The polyaxial pedicle screw of claim 19, wherein one of the first and second portions is cylindrically shaped and the other of the first and second portions is spherically shaped, the cylindrically shaped portion enabling the head to fit through the opening in the housing and the spherically shaped portion maintaining the head of the bone screw member within the housing once inserted.

21. The polyaxial pedicle screw of claim 20, further comprising a cap securable to the housing to prevent the bone screw member from re-orienting to a position in which the cylindrically shaped portion of the head of the bone screw member is aligned with the housing opening.

22. A polyaxial pedicle screw comprising:

a bone screw member including a head having a threaded shaft extending from the head, the head including a first portion and a second portion;

a housing positionable on the head of the bone screw, the housing having a distal opening,

wherein the first head portion is configured and dimensioned to pass through the housing distal opening and the second head portion is configured and dimensioned not to pass through the housing distal opening.

23. The polyaxial pedicle screw of claim 22, wherein the first head portion includes a substantially cylindrically shaped section.

24. The polyaxial screw of claim 23, wherein the cylindrically shaped section defines a diameter that is less than the diameter of the housing distal opening.

25. The polyaxial screw of claim 24, wherein the housing further defines a collar extending from the distal end of the housing and defining a cut out section, whereby the screw assumes an insertion position with the neck of the screw disposed in the cut out section with the cylindrically shaped section of the head aligned with the housing distal opening.

26. The polyaxial screw of claim 22 wherein the second head portion defines a diameter larger than the diameter of the housing distal opening.

27. The pedicle screw of claim 26, wherein the second head portion includes a substantially spherical section.

28. The pedicle screw of claim 22, further comprising an anvil positionable within the housing adjacent to the head of the bone screw member when the anvil and the head of the bone screw member are positioned within the housing, the anvil defining at least one groove in an outer surface of the anvil, the groove defining at least one flap, the at least one flap being flexibly attached to the anvil to enable the anvil to flex an amount sufficient to maintain the head of the bone screw member in constant contact with the anvil.

29. The polyaxial pedicle screw of claim 28, wherein the anvil defines a cavity having a surface with a plurality of radii of curvature to accommodate variously sized rod members.

30. The polyaxial pedicle screw of claim 29, wherein the surface of the cavity defines a first section with a first radius of curvature, a second section with a second radius of curvature, and a third section with a third radius of curvature such that the plurality of radii of curvature defines a compound curve that provides at least two lines of contact on a plurality of different diameter rod members.

31. The polyaxial pedicle screw of claim 28, wherein the outer surface of the anvil has a non-round shape to prevent disorientation of the anvil when positioning a rod member adjacent the anvil.

32. The polyaxial pedicle screw of claim 28, further comprising a set screw positionable within the housing to secure a rod member within the housing adjacent the anvil.

33. The polyaxial pedicle screw of claim 28, wherein the bone screw member is positionable at a plurality of angles relative to the housing when engaged to the housing and securable relative to the housing at angles within a cone angle of up to approximately 80 degrees.

34. The polyaxial pedicle screw of claim 28, further comprising a cap securable to the housing to prevent the bone screw member from re-orienting to a position in which the screw head first portion is aligned with the housing distal opening.

35. The polyaxial pedicle screw of claim 28, wherein the anvil includes a protuberance on the outer surface of the anvil and the housing defines a slot on an inner surface of the housing, the protuberance and the slot being engagable to maintain the alignment of the anvil with respect to the housing.

36. The polyaxial pedicle screw of claim 28, wherein the head of the bone screw member includes surface texture that frictionally engages with the anvil such that a user applied force is necessary to reposition the bone screw member relative to the anvil when the bone screw member is disposed in engagement with the anvil without a rod in the housing.

37. A method of assembling a pedicle screw comprising:

providing a pedicle screw including;

a bone screw member including a head having a threaded shaft extending from the head, the head including a first portion and a second portion;

a housing positionable on the head of the bone screw, the housing having a distal opening,

wherein the first head portion is configured and dimensioned to pass through the housing distal opening and the second head portion is configured and dimensioned not to pass through the housing distal opening;

positioning the screw relative to the housing such that the first housing portion is aligned with the housing distal opening;

inserting the screw head through the housing distal opening with the first head portion aligned with the distal opening;

rotating the screw relative to the housing such that the first head portion is no longer aligned with the housing distal opening and the second head portion prevents the screw head from exiting through the distal opening.

38. The method of claim 37, further comprising mounting a collar onto the housing with the screw head disposed in the housing to prevent the screw from reassuming the position with the cylindrically shaped section aligned with the housing distal opening.