Polyaxial bone anchor with spline capture connection and lower pressure insert

• US 20100191293A1
• Filed: 03/26/2010
• Published: 07/29/2010
• Est. Priority Date: 06/18/2003
• Status: Active Grant

• Current Assignee: Roger P. Jackson
• Original Assignee: Roger P. Jackson
• Inventors: Jackson, Roger P.
• Granted Patent: US 8,377,102 B2
• Time in Patent Office: Days
• US Class Current: 606/302
• 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
• CPC Class Codes: A61B 17/8605 Heads, i.e. proximal ends projecting from bone

Abstract

A medical implant assembly includes a polyaxial bone anchor having a shank with an upper portion, a receiver, a retainer for holding the shank upper portion in the receiver, a lower compression insert with surfaces for closely receiving an elongate connecting member and a closure structure that may independently engage the lower compression insert to lock the shank with respect to the receiver while selectively not locking the elongate member. Projections or splines of the shank upper portion mate with holding pockets on the retainer. The bone anchor includes a shank upper surface exclusively engaging the lower compression insert that is spaced from the retainer, the retainer and shank being configured for polyaxial motion with respect to the receiver prior to locking.

Claims

1. A polyaxial bone anchor comprising:

a) a shank having a body for fixation to a bone and an integral upper portion, the upper portion having an upper end surface and at least one laterally directed projection;

b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an external of the base through an opening sized and shaped to receive the shank upper portion therethrough;

c) a compression insert disposed in the receiver, the insert having a mating surface exclusively frictionally engageable with the upper end surface of the shank upper portion; and

d) a retainer having an external surface and a central bore with an internal surface defining the central bore having at least one substantially vertical channel for slideably receiving the projection therethrough and at least one pocket for downwardly receiving and holding the projection of the shank upper portion, the shank upper portion and the retainer being in fixed relation to one another, both the upper portion and the retainer being in swivelable relation within the receiver, providing selective angular positioning of the shank with respect to the receiver, the retainer external surface being in slidable engagement with the receiver seating surface, the retainer being substantially spaced from the compression insert at any and all angular positions of the shank with respect to the receiver.

2. The bone anchor of claim 1 further comprising a closure top engaging the compression insert to lock the angular position of the shank with respect to the receiver.

3. The bone anchor of claim 1 wherein the receiver has a projected wall surface engaging the compression insert.

4. The bone anchor of claim 3 wherein the projected wall surface prevents rotational movement of the compression insert.

5. The bone anchor of claim 3 wherein the projected wall surface biases the compression insert into non-locking frictional engagement with the shank upper portion.

6. The bone anchor of claim 1 wherein the shank is cannulated.

7. The bone anchor of claim 1 wherein the shank has an internal drive feature.

8. A polyaxial bone screw assembly comprising:

a) a receiver having a channel adapted to receive an elongate longitudinal member and having a lower restrictive neck;

b) a compression insert located in the receiver and adapted to engage the longitudinal connecting member;

c) a shank having a lower portion adapted to be implanted in a bone of a patient and an upper portion having at least one laterally directed projection;

the shank upper portion being sized and shaped to be positioned in the receiver so as to have the shank extend through the lower restrictive neck;

d) a retainer ring separate from the shank, received in the receiver and adjacent the lower restrictive neck;

the retainer ring mating with and non-pivotably coupled to the shank upper portion by downward positioning of the laterally directed projection into a holding pocket in the retainer ring, the upper portion and retainer ring being polyaxially rotatable together relative to the receiver prior to locking of the position of the shank relative to the receiver, the retainer ring'"'"'width being larger than a width of the receiver lower restrictive neck so as to hold the shank upper portion in the receiver while allowing polyaxial movement of the shank relative to the receiver during positioning; and

e) the shank upper portion being sized, shaped and positioned to engage the compression insert and receive a downward force from the compression insert.

9. The bone screw assembly of claim 8 wherein the retainer ring is spaced from and located below a top surface of the shank upper portion, the retainer ring being unengaged with the compression insert at any and all angular positions of the shank with respect to the receiver.

10. The bone screw assembly of claim 8 further comprising crimping structure on the receiver, the crimping structure engaging the compression insert and biasing the compression insert against the shank upper portion to provide non-floppy positioning of the shank with respect to the receiver.

11. The bone screw assembly of claim 8 further comprising a closure top having mating structure for mating with the receiver and capturing a longitudinal connecting member in the receiver and wherein the compression insert is sized, shaped and positioned to receive a downward force from the closure top so as to lock the position of the shank relative to the receiver channel thereby locking of the position of the shank and the receiver relative to one another.

12. A polyaxial bone screw assembly comprising:

a) a receiver having a channel adapted to receive an elongate longitudinal member and having a lower opening;

b) a shank having a lower portion adapted to be implanted in a bone of a patient and an upper portion, the shank upper portion having at least one laterally directed projection and being sized and shaped to be positioned in the receiver so as to extend through the lower opening;

c) a retaining structure non-integral with the shank and loaded into the receiver separately from the shank, the retaining structure mating with and being secured to the shank by downward positioning of the laterally directed projection into a holding pocket in the retaining structure so as to capture and pivot the retaining structure with the shank upper portion in the receiver so as to allow polyaxial movement of the shank relative to the receiver; and

d) a compression insert directly and frictionally engaging the shank upper portion and in spaced relation with the retaining structure.

13. The assembly of claim 12 further comprising a closure top engaging the compression insert to lock the angular position of the shank with respect to the receiver.

14. A polyaxial bone screw assembly comprising:

a) an elongate longitudinal connecting member;

b) a receiver having a channel for receiving the connecting member during use and having a lower bore and a lower opening;

c) a shank having a lower portion adapted to be implanted in a bone of a patient and an upper portion, the upper portion having at least one laterally directed projection and being sized and shaped to be loaded into the receiver through the lower opening;

d) a compression insert located in the receiver, the insert in engagement with the connecting member and with the shank upper portion;

e) a retainer ring separate from the shank and received in the receiver, the retainer ring mating with and secured to the shank upper portion by downward positioning of the laterally directed projection into a holding pocket in the retainer ring so as to rotate the ring together with the shank relative to the receiver during positioning, the compression insert, retainer ring and shank upper portion forming a subassembly prior to locking of the position of the shank relative to the receiver, the subassembly presenting a receiver engaging surface so as to hold the shank in the receiver in a non-floppy manner while allowing polyaxial movement of the shank relative to the receiver during positioning;

f) a closure including mating structure for mating with the receiver and closing the channel so as to capture the longitudinal connecting member in the channel; and

g) the shank upper portion being sized, shaped and positioned such that upon assembly of the bone screw and the longitudinal connecting member, the shank upper portion receives a force generated by the closure that causes frictional engagement of the retainer ring with the receiver so as to secure the shank in a selected fixed angular configuration relative to the receiver.

15. A polyaxial bone anchor comprising:

a) a shank having a body for fixation to a bone and an integral upper portion, the upper portion having an upper end surface and at least one laterally directed projection;

b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an external of the base through an opening;

c) a compression insert disposed in the receiver, the insert having a mating surface exclusively frictionally engageable with the upper end surface of the shank upper portion; and

d) a retainer having an external surface and a central bore with an internal surface defining the central bore having at least one substantially vertical channel for slideably receiving the projection therethrough and at least one pocket for downwardly receiving and holding the projection of the shank upper portion, the shank upper portion and the retainer being in fixed relation to one another, both the upper portion and the retainer being in swivelable relation within the receiver, providing selective angular positioning of the shank with respect to the receiver, the retainer external surface being in slidable engagement with the receiver seating surface, the retainer being substantially spaced from the compression insert at any and all angular positions of the shank with respect to the receiver.