Pivotal bone anchor assembly with twist-in-place insert

1. A pivotal bone anchor assembly for securing a longitudinal connecting member to a bone of a patient via a fastener, the pivotal bone anchor assembly comprising:

a receiver having a central bore centered on a vertical centerline axis and in communication with a bottom surface of the receiver through a lower opening, and an integral upper portion defining a channel configured to receive the longitudinal connecting member and communicating with the central bore, the central bore including a helically wound thread form threadably engageable with the fastener, an integral downward facing surface below the helically wound thread form, and at least one first interference surface;

a shank having a head portion with an upper engagement surface and an anchor portion opposite the head portion configured for attachment to the bone, the head portion configured for being positioned within a lower portion of the central bore with the shank extending downwardly through the lower opening; and

a compression insert having a central opening, at least one vertically extending outer alignment groove with an inwardly extending curvate surface, and at least one protuberant second interference surface, the compression insert being configured for top loading positioning into the central bore into a first position followed by rotation about the vertical centerline axis of the receiver into an engagement between the at least one protuberant second interference surface of the compression insert and the at least one first interference surface of the central bore that resists rotation between the compression insert and the receiver,

wherein the compression insert has radially offset upwardly facing top-most surfaces configured for engagement with the downward facing surface of the central bore upon the rotation of the compression insert in the receiver so as to inhibit the compression insert from moving upward in the central bore, and

wherein the receiver has at least one inwardly extending integral non-resilient structure positionable into the at least one vertically extending outer alignment groove of the compression insert upon the completion of the rotation of the compression insert in the receiver, so as to inhibit reverse rotation of the compression insert with respect to the receiver.

2. The pivotal bone anchor assembly of claim 1 , wherein the compression insert further comprises inwardly positioned concave surfaces configured to engage the longitudinal connecting member.

3. The pivotal bone anchor assembly of claim 1 , wherein at least one of the downward facing top-most surface of the central bore or the radially offset upwardly facing surfaces of the compression insert includes a sloped portion operable to provide a cam action that urges a lower surface of the compression insert against the upper engagement surface of the head portion of the shank.

4. The pivotal bone anchor assembly of claim 1 , wherein the downward facing surface of the central bore is downwardly inclined.

5. The pivotal bone anchor assembly of claim 1 , wherein the downward facing surface of the central bore further comprises a bottom abutment surface of the helically wound thread form formed into an interior surface of the channel.

6. The pivotal bone anchor assembly of claim 1 , further comprising a retainer configured for capturing the head portion of the shank within a lower portion of the central bore of the receiver.

7. The pivotal bone anchor assembly of claim 6 , wherein the retainer further includes an outer spherical surface configured to pivotably engage a spherical seating surface in the lower portion of the central bore to provide for pivotal motion between the receiver and the shank.

8. The pivotal bone anchor assembly of claim 1 ,

wherein the at least one inwardly extending integral non-resilient structure comprises a pair of opposed inwardly extending integral non-resilient structures and the at least one vertically extending outer alignment groove comprises a pair of vertically extending outer alignment grooves formed in opposite outer surfaces of the compression insert, and

wherein upon the completion of the rotation of the compression insert in the receiver, the pair of opposed inwardly extending integral non-resilient structures is engageable with the pair of vertically extending outer alignment grooves to inhibit the reverse rotation of the compression insert with respect to the receiver.

9. The pivotal bone anchor assembly of claim 1 , wherein the helically wound thread form comprises an interlocking flange form.

10. The pivotal bone anchor assembly of claim 1 , wherein the shank includes an axial bore extending an entire length thereof along a longitudinal axis of the shank, the axial bore having a width that is less than a most narrow width of a central non-slip tool engaging aperture formed into the head portion of the shank.

11. The pivotal bone anchor assembly of claim 1 , wherein the radially offset upwardly facing top-most surfaces of the compression insert are adjacent a radially outwardly facing concave surface on the compression insert.

12. The pivotal bone anchor assembly of claim 1 , wherein the upper portion of the receiver includes opposite outwardly facing recessed planar surfaces that are parallel with respect to each other and with the vertical centerline axis.

13. The pivotal bone anchor assembly of claim 1 , wherein the at least one vertically extending outer alignment groove of the compression insert extends to one of the radially offset upwardly facing top-most surfaces of the compression insert or to a lower surface on the compression insert.

14. The pivotal bone anchor assembly of claim 1 and further comprising the longitudinal connecting member and the fastener, wherein the fastener is configured for positioning within the central bore of the receiver above longitudinal connecting member and in engagement with the helically wound thread form to apply a downward pressure to a top of the longitudinal connecting member, so as to secure the longitudinal connecting member to the bone of the patient.

15. The pivotal bone anchor assembly of claim 1 , wherein the compression insert further comprises a lower portion with a downwardly and inwardly sloping outer surface.

16. The pivotal bone anchor assembly of claim 1 , wherein the compression insert is configured for top-loading into the central bore into the first position.

17. A pivotal bone anchor assembly for securing a longitudinal connecting member to a bone of a patient via a fastener, the pivotal bone anchor comprising:

a receiver having a central bore centered on a vertical centerline axis, a lower portion with an inner spherical seating surface partially defining a cavity communicating with a bottom surface of the receiver through a lower opening, and an integral upper portion configured to receive the longitudinal connecting member, the central bore communicating with the cavity and the bottom surface through the lower opening and including at least one first interference surface;

a shank having a shank longitudinal axis, a head with a capture structure and a top surface with a central non-slip tool engagement aperture formed therein and centered on the shank longitudinal axis, and an anchor portion opposite the head configured for fixation to the bone;

a retainer having an interior engagement surface configured to capture and hold the capture structure of the head of the shank within the cavity of the receiver, the retainer being engageable with the inner spherical seating surface of the cavity; and

a compression insert positionable in the central bore of the receiver and configured for rotation about the vertical centerline axis, the compression insert having radially offset upwardly facing top-most surfaces and a central opening centered on the vertical centerline axis when the compression insert is positioned within the central bore and configured to receive therethrough a lower end portion of a driving tool having a non-slip drive structure configured for insertion into the central non-slip tool engagement aperture of the head of the shank, the compression insert including diametrically opposite vertically extending outer alignment grooves and at least one protuberant second interference surface configured to resist rotation between the compression insert and the receiver upon engagement with the at least one first interference surface, the compression insert configured to be initially loaded into a first position in the central bore,

wherein upon rotation of the compression insert in the receiver prior to locking the pivotal bone anchor assembly with the fastener, the radially offset upwardly facing top-most surfaces of the compression insert are configured to engage a downwardly facing surface formed within the central bore of the receiver to inhibit the compression insert from moving in the central bore, and

wherein upon completion of the rotation in the receiver, the vertically extending outer alignment grooves of the compression insert are configured to receive inwardly extending integral non-resilient structures formed in the receiver to inhibit a reverse rotation of the compression insert with respect to the vertical centerline axis of the receiver.

18. The pivotal bone anchor assembly of claim 17 ,

wherein the receiver includes a first open channel, and

wherein the compression insert further comprises a pair of opposed sides forming a second open channel, the opposed sides being substantially non-resilient and having the outer alignment grooves formed therein, the second open channel configured for alignment with the first open channel upon the completion of the rotation of the compression insert in the receiver.

19. The pivotal bone anchor assembly of claim 15 , wherein the retainer is configured to pivot with respect to the receiver when engaged with the inner spherical seating surface.

20. The pivotal bone anchor assembly of claim 19 , wherein the retainer is secured to the capture structure of the head of the shank so as to pivot with the shank relative to the receiver.

21. The pivotal bone anchor assembly of claim 15 , wherein the retainer is in the shape of a ring structure with a top surface positioned below the top surface of the head of the shank when the capture structure of the head of the shank is supported by the retainer within the cavity of the receiver.

22. The pivotal bone anchor assembly of claim 15 , wherein the retainer is positioned within the cavity of the receiver prior to the shank.

23. The pivotal bone anchor assembly of claim 15 , wherein the inwardly protruding integral non-resilient structures are opposed crimped walls.

24. The pivotal bone anchor assembly of claim 17 , wherein the compression insert is configured to be top-loaded into the receiver.

25. The pivotal bone anchor assembly of claim 15 , wherein the compression insert further includes a resilient structure having an upwardly sloping surface extending upwardly from at least one of the radially offset upwardly facing surfaces and spaced above a notch formed into an outer surface of the compression insert.

26. The pivotal bone anchor assembly of claim 15 and further comprising the longitudinal connecting member and the fastener, wherein the fastener is configured for positioning within the central bore of the receiver above longitudinal connecting member and in engagement with a mating structure formed into the central bore to apply a downward pressure to a top of the longitudinal connecting member, so as to secure the longitudinal connecting member to the bone of the patient.