Polyaxial bone anchor with pop-on shank, friction fit retainer and winged insert
A polyaxial bone screw assembly includes a threaded shank body having an integral upper portion receivable in an integral receiver, the receiver having an upper channel for receiving a longitudinal connecting member and a lower cavity cooperating with a lower opening. A down-loadable compression insert with tool receiving arm extensions, a down-loadable friction fit split retaining ring and an up-loadable shank upper portion cooperate to provide for pop- or snap-on assembly of the shank with the receiver either prior to or after implantation of the shank into a vertebra. The shank and receiver once assembled cannot be disassembled.
1. In a bone anchor, the improvement comprising:
a) a shank having a body for fixation to a bone and an integral upper substantially spherical head;
b) a receiver having a top portion and a receiver base and an outer surface, the receiver top portion defining a first open channel, the base defining a chamber and a lower opening, the chamber communicating with both the channel and the lower opening, the top portion having a pair of opposed through apertures formed therein;
c) an insert disposed within the receiver, the insert having a curved surface sized and shaped for frictional mating cooperation with the shank head and having a second open channel, the insert further having a pair of outwardly extending arm portions, each arm portion having an interior surface and each arm portion partially extending through one of the apertures of the receiver, an arm portion interior surface having a groove, the groove being engageable a first manipulation tool for movement of the insert both downwardly into contact with the shank head, upwardly away from the shank head, and rotational movement of the insert; and
d) a resilient open retainer having a retainer base, the retainer captured within the chamber and expandable about at least a portion of the shank head and wherein expansion-only locking engagement occurs between the shank upper portion and the retainer base and between the retainer base and the receiver.
2. The improvement of claim 1 wherein a pair of shallow grooves are formed in the outer surface of the receiver, each groove communicating with a respective aperture, each groove extending from the respective aperture to a top surface of the top portion of the receiver, each groove having a width for receiving a second manipulation tool.
3. The improvement of claim 1 wherein the insert has an outer surface releasably frictionally locked against the receiver.
4. The improvement of claim 1 wherein the insert being rotated into a locked position above the retainer with the second channel aligned with the first channel by the first manipulation tool in the groove on the interior surface of the insert.
5. The improvement of claim 4 wherein the insert outwardly extending arm portions are received by an inner cylindrical surface of the receiver top portion during rotation of the insert with respect to the receiver.
6. The improvement of claim 1 wherein the retainer base has at least a first planar surface seated on a second planar surface partially defining the receiver chamber.
7. The improvement of claim 1 wherein the retainer base has a first outer non-tapered surface in engagement with a second surface partially defining the receiver chamber.
8. The improvement of claim 1 wherein the retainer is partially defined by a concave inner partially spherical surface having a radius smaller than a radius of the shank head and wherein at least one of an upper and a lower edge defining the retainer inner partially spherical surface is in frictional engagement with the shank head.
9. The improvement of claim 8 wherein both the upper and lower edges defining the retainer inner partially spherical surface are in temporary frictional engagement with the shank head to provide a frictional but movable engagement between the shank head and the retainer prior to locking of the shank head with respect to the retainer.
10. The improvement of claim 1 wherein the retainer further comprises a pair of opposed outwardly extending resilient tabs and the retainer base has at least a first planar surface and the receiver has a second planar surface partially defining the receiver chamber and a second pair of opposed apertures and wherein after the shank head is received through the retainer base, the retainer base first planar surface is seated on the receiver second surface and the resilient tabs expand to a neutral state and are captured within the second pair of receiver apertures.
11. The improvement of claim 1 wherein the receiver has a cut-out along the opening of the base which creates a cupped surface.
12. The improvement of claim 11 wherein the retainer has a cut-out along the opening of the base which creates a cupped surface.
13. In a bone anchor, the improvement comprising:
a) a shank having a body for fixation to a bone and an integral upper substantially spherical head having a first radius;
b) a receiver having a base, a first pair of upright arms and an outer surface, the receiver upright arms defining an open channel, the base defining a chamber and a lower opening, the chamber communicating with both the channel and the lower opening, each arm having a through aperture formed therein;
c) an insert disposed within the receiver chamber, the insert having a surface sized and shaped for frictional mating cooperation with the shank head and having a second open channel, the insert further having a second pair of upright arms, each arm having an interior surface and each arm having an outwardly extending wing, the arm interior having a groove, the groove being engageable by a first manipulation tool for movement of the insert upward, downward, and rotationally; and
d) a resilient open retainer having a base, the retainer captured within the chamber and expandable about at least a portion of the shank head and wherein expansion-only locking engagement occurs between the shank upper portion and the retainer base and between the retainer base and the receiver, the retainer having a concave second substantially spherical surface with a radius smaller than the radius of the shank head, the second surface terminating at upper and lower edges, the edges temporarily frictionally mating with the shank head, providing a friction fit between the retainer and the shank head during non-locking angular manipulation of the shank with respect to the receiver.
14. The improvement of claim 13 wherein a pair of shallow grooves are formed in the outer surface of the receiver, each groove communicating with a respective aperture, each groove extending from the respective aperture to a top surface of the top portion of the receiver, each groove having a width for receiving a second manipulation tool.
15. The improvement of claim 13 wherein the insert has an outer surface releasably frictionally locked against the receiver.
16. The improvement of claim 13 wherein the insert is top loaded into the receiver and then rotated by the first manipulation tool into a position above the retainer with the insert second pair of arms aligned with the receiver first pair of arms and the wings located within the receiver apertures.
17. The improvement of claim 13 wherein the retainer base has at least a first planar surface seated on a second planar surface partially defining the receiver chamber.
18. The improvement of claim 13 wherein the retainer base has a first outer non-tapered surface in engagement with a second surface partially defining the receiver chamber.
19. The improvement of claim 13 wherein the retainer further comprises a pair of opposed outwardly extending resilient tabs and the retainer base having at least a first planar surface and the receiver having a second planar surface partially defining the receiver chamber and a second pair of opposed apertures and wherein after the shank head is received through the retainer base, the retainer base first planar surface is seated on the receiver second surface and the resilient tabs expand to a neutral state and are captured within the second pair of receiver apertures.
20. The improvement of claim 13 wherein the receiver has a cut-out along the opening of the receiver base which creates a cupped surface.
21. The improvement of claim 20 wherein the retainer has a cut-out along the opening of the retainer base which creates a cupped surface.
22. In a bone anchor, the improvement comprising:
a) a shank having a body for fixation to a bone and an integral upper portion having a convex substantially spherical first surface with a first radius;
b) a receiver having a base and a pair of upright arms forming an open first channel, the base defining a chamber and having a lower opening, the channel communicating with the chamber;
c) an insert disposed within the receiver chamber having a second open channel with an interior surface, the interior surface having a groove that directly engages a lock and release tool;
d) a resilient open retainer captured within the chamber and expandable about at least a portion of the shank upper portion, the retainer having a concave surface with a radius smaller than the radius of the shank upper portion first surface, the retainer concave surface terminating at upper and lower edges, the edges frictionally mating with the shank first spherical surface, providing a friction fit between the retainer and the shank during non-locking angular manipulation of the shank with respect to the receiver; and
e) wherein expansion-only locking engagement occurs between the shank upper portion and the retainer and between the retainer and the receiver.
23. The improvement of claim 22 wherein the receiver pair of upright arms is a first pair of upright arms, and the insert comprises a body and a second pair of upright arms, each insert arm having an outwardly extending wing, each wing extending through an aperture of the receiver, the insert groove being engageable by the lock and release tool for movement of the insert upward, downward, and rotationally.
24. The improvement of claim 23 wherein a pair of shallow grooves are formed in the outer surface of the receiver, each groove communicating with a respective receiver aperture, each groove extending from the respective aperture to a top surface of the receiver, each groove having a width for receiving a manipulation tool.
25. The improvement of claim 22 wherein the retainer further comprises a pair of opposed outwardly extending resilient tabs and the retainer having a base with at least a first planar surface and the receiver having a second planar surface partially defining the receiver chamber and a second pair of opposed apertures and wherein after the shank upper portion is received through the retainer base, the retainer base first planar surface is seated on the receiver second surface and the resilient tabs expand to a neutral state and are captured within the second pair of receiver apertures.
26. The improvement of claim 22 wherein the receiver has a cut-out along the opening of the receiver base which creates a cupped surface.
27. The improvement of claim 26 wherein the retainer has a cut-out along the opening of the retainer base which creates a cupped surface.