Polyaxial bone screw with cam connection and lock and release insert

• US 20110282399A1
• Filed: 05/12/2011
• Published: 11/17/2011
• Est. Priority Date: 01/22/2007
• Status: Active Grant

• Current Assignee: Roger P. Jackson
• Original Assignee: Roger P. Jackson
• Inventors: Jackson, Roger P.
• Granted Patent: US 10,792,074 B2
• Time in Patent Office: Days
• US Class Current: 606/305
• CPC Class Codes: A61B 17/702 having a core or insert, and a sleeve, whereby a screw or hook can move along the core or in the sleeve
• CPC Class Codes: A61B 17/7037 wherein pivoting is blocked when the rod is clamped
• CPC Class Codes: A61B 17/705 for linking adjacent ends of longitudinal elements
• CPC Class Codes: A61B 17/86 Pins or screws or threaded wires; nuts therefor A61B17/72 take precedence

Abstract

A polyaxial bone screw assembly includes, a threaded shank body having an integral upper portion receivable in a receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A retaining member for capturing the shank in the receiver includes a sloping surface for a frictional, press fit, cammed engagement with the shank. A compression insert having a resilient structure provides non-floppy positioning of the shank with respect to the receiver and also independent locking of the shank with respect to the receiver.

Claims

1. A bone anchor assembly comprising:

a) a receiver having a lower portion with a cavity and a lower opening communicating with the cavity and an upper portion with an upper opening communicating with a longitudinal connecting member receiving channel, the channel communicating with the cavity, a first receiver surface partially defines the channel and a second receiver surface partially defines the cavity;

b) a bone screw shank having a head and a body for fixation to bone, the head having an engagement surface;

c) a retaining member for capturing the shank head within the receiver, the retaining member having an interior surface sized and shaped for a locking press-fit, fixed engagement with the shank head engagement surface; and

d) a compression insert positioned in the receiver, the compression insert having at least one integral resilient structure with a portion thereof partially spaced from the insert, the resilient structure being compressible toward the insert by the receiver first surface with the insert also pressing against the shank head during non-floppy articulation of the shank head with respect to the receiver.

2. The assembly of claim 1 wherein the channel is a first channel and the insert further comprises a pair of opposed arms forming a second channel, the resilient structure located at an outer surface of at least one of the arms.

3. The assembly of claim 1 wherein the insert has a top surface and the resilient structure extends upwardly from the top surface.

4. The assembly of claim 1 wherein the insert is sized and shaped to have a locking position wherein the resilient structure is in a substantially neutral state, the insert frictionally locking against the receiver and the insert in locking engagement with the shank head.

5. The assembly of claim 4 wherein the resilient structure locks against the receiver second surface.

6. The assembly of claim 4 wherein the channel is a first channel and the insert further comprises a pair of opposed arms forming a second channel, the insert having at least one outer arm surface frictionally locking against the receiver second surface.

7. The assembly of claim 1 wherein the shank and retaining member cooperate in such a manner that a partial rotation between the retaining member and the shank brings the shank and retaining member into the locking press-fit engagement.

8. The assembly of claim 7 wherein the shank has a central axis and the partial rotation between the shank and retaining member is about the central axis.

9. The assembly of claim 7 wherein the shank head engagement surface is located on at least one outwardly extending projection, the projection frictionally mating with the retaining member interior surface.

10. The assembly of claim 9 wherein the at least one projection is a plurality of projections.

11. The assembly of claim 1 wherein the shank head has a lower spherical surface having a radius and the retaining member has an outer spherical surface, a radius of the outer spherical surface being the same as the radius of the shank head lower spherical surface, the outer spherical surface and the retaining member lower spherical surface being adjacent.

12. The assembly of claim 11 wherein the shank head lower spherical surface terminates at a shelf, the retaining member being seated on the shelf.

13. A bone anchor comprising:

a) a receiver having a lower portion with an inner seating surface partially defining a cavity and a lower opening communicating with the cavity and an upper portion with an upper opening communicating with a longitudinal connecting member receiving channel, the channel communicating with the cavity;

b) a shank having a head with a top surface and a first sloping surface, the shank also having a body for fixation to bone;

c) a retainer for capturing the shank head within the receiver cavity, the retainer having at least a second sloping surface sized and shaped for press fit engagement with the first sloping surface; and

d) a compression insert positioned in the receiver, the insert sized and shaped for first and second positions with respect to the receiver, and wherein in the first position, the insert frictionally engages the receiver upper portion and the shank head is in movable frictional engagement with the insert, and in the second position, the insert frictionally engages and locks against at least one of an intermediate surface defining the channel and the receiver lower portion, the insert also frictionally locking against the shank head.

14. The bone anchor of claim 13 wherein the shank head has a top surface and the insert exclusively engages the top surface and remains spaced from the retainer in all articulations of the shank with respect to the receiver.

15. The bone anchor of claim 13 wherein the receiver channel is a first channel and the insert further comprises:

a) a pair of opposed arms forming a second channel, the arms being substantially non-resilient, the second channel in alignment with the first channel; and

b) at least one outer resilient structure located near and slightly spaced from at least one of the insert arms, the resilient structure being compressible toward the at least one arm, the structure, when compressed, resiliently pressing against the receiver when in the insert first position during manipulation of the shank with respect to the receiver with the shank head being in frictional, but movable engagement with the insert.

16. The bone anchor of claim 15 wherein the resilient structure is locked against the receiver when the resilient structure is in a neutral to near neutral substantially non-compressed state and the insert is in the second position within the receiver operatively frictionally locked against the shank.

17. The bone anchor of claim 16 wherein the resilient structure presses against the receiver lower portion when in a neutral to near neutral state.

18. The bone anchor of claim 16 wherein the resilient structure is located at a top surface of the insert.

19. The bone anchor of claim 13 wherein the at least one outer compressible resilient structure and the at least one arm form a slit.

20. The bone anchor of claim 13 wherein the at least one outer compressible resilient structure and the at least one arm form a through slit running from a top surface to a lower surface of the insert.

21. The bone anchor of claim 13 wherein the shank and the retainer cooperate in such a manner that a partial rotation between the retainer and the shank results in a press fit engagement therebetween.

22. The bone anchor of claim 13 wherein the shank has a central axis and the partial rotation between the shank and the retainer is about the central axis.

23. The bone anchor of claim 13 wherein the receiver further comprises at least one spring tab resiliently pressing against the insert at an outer surface thereof, prohibiting rotation of the insert with respect to the receiver.

24. A bone anchor comprising:

a) a receiver having a lower portion with an inner seating surface partially defining a cavity and a lower opening communicating with the cavity and an upper portion with an upper opening communicating with a longitudinal connecting member receiving channel, the channel communicating with the cavity;

b) a shank having a head with at least a first engagement structure, the shank also having a body for fixation to bone;

c) a retainer for capturing the shank head within the receiver cavity, the retainer having at least a second engagement structure sized and shaped for press fit engagement with the shank first engagement structure, the shank head and the retainer cooperating in such a manner that a partial rotation between the first and second engagement structures brings the shank and the retainer into the press-fit engagement; and

d) a compression insert having at least one resilient outer surface feature compressible toward the insert, the resilient structure sized and shaped for pressing against the receiver and temporarily holding the insert in frictional engagement with the shank head for non-floppy positioning of the shank with respect to the receiver.

25. The bone anchor of claim 24 wherein the at least one resilient outer surface feature operatively frictionally locks against an inner surface of the receiver partially defining the cavity.

26. The bone anchor of claim 24 wherein the at least one outer resilient outer surface structure is located at a top surface of the insert and temporarily presses against a receiver surface partially defining the channel.

27. The bone anchor of claim 24 having at least two opposed resilient outer surface features.

28. The bone anchor of claim 24 wherein the receiver includes at least two inner cylindrical walls of different diameters.