Pivotal bone anchor assembly with ring retainer and twist-in-place pressure insert
View Patent ↗A pivotal bone anchor assembly includes a receiver having an internal cavity with a circumferential groove adjacent a bottom opening, an upper channel with a downward-facing surface below a closure mating structure, and an internal cylindrical surface with a fixed rotation abutment surface. The assembly also includes an insert positionable into the upper channel having outer side surfaces of upstanding arms with a protruding abutment structure, a shank with a capture portion uploadable through the bottom opening, and a ring retainer uploadable into the circumferential groove to engage and hold the capture portion within the cavity. The insert is rotatable about a centerline axis of the receiver until an upwardly-facing surface on the insert rotates beneath the downward-facing surface and an outer surface of the protruding abutment structure abuts the fixed rotation abutment surface to inhibit both upward movement and further rotation, respectively, of the insert within the receiver.
1. A pivotal bone anchor assembly for a securing an elongate rod to a bone of a patient via a closure and configured to be acted upon by a drive tool, the pivotal bone anchor assembly comprising:
a receiver comprising a vertical centerline axis, an upper portion defining a first open channel configured to receive the elongate rod, and a base defining a cavity centered about the vertical centerline axis and communicating with the first open channel and with a bottom surface of the receiver through a bottom opening, the first open channel including a discontinuous closure mating structure formed therein, a discontinuous downward-facing surface below the closure mating structure, and a substantially cylindrical surface extending downward from the downward-facing surface and including a longitudinally-extending rotation abutment surface, the cavity including a circumferential groove adjacent the bottom opening having an upward-facing support surface;
a shank comprising a capture portion with a partial spherical surface and a central drive tool-engaging structure formed therein, and an anchor portion opposite the capture portion configured to fix to the bone, the capture portion being uploadable into the cavity of the receiver through the bottom opening;
a ring retainer uploadable into the circumferential groove through the bottom opening of the receiver after the capture portion so as to engage and hold the capture portion within the cavity with outer surfaces of the ring retainer positionable against the upward-facing support surface of the circumferential groove while allowing for pivotal movement between the receiver and the shank; and
a pressure insert comprising a cylindrical body having a central opening configured to allow the drive tool to pass through to engage the drive tool-engaging structure of the shank, upstanding arms with outer side surfaces including a protruding rotational abutment structure, and an interior upwardly-facing surface extending between the upstanding arms to define a second open channel configured to receive the elongate rod, the pressure insert being positionable into a first position within the first open channel of the receiver adjacent the substantially cylindrical surface, in which the central opening is centered on the vertical centerline axis of the receiver and the second open channel of the pressure insert is transverse to the first open channel, the protruding rotational abutment structure is angularly spaced from the longitudinally-extending rotation abutment surface, and with upwardly-facing surfaces on the upstanding arms being located adjacent to and angularly spaced from the discontinuous downward-facing surface below the closure mating structure,
wherein after being positioned into the first position, the pressure insert is rotatable about the vertical centerline axis of the receiver until the second open channel of the pressure insert is aligned with the first open channel, the upwardly-facing surfaces of the upstanding arms have rotated at least partially beneath the discontinuous downward-facing surface to inhibit upward movement of the pressure insert within the receiver, and an outer surface of the protruding rotational abutment structure abuts the longitudinally-extending rotation abutment surface to inhibit further rotation of the pressure insert in at least one direction within the receiver.
2. The pivotal bone anchor assembly of claim 1 , wherein the upwardly-facing surfaces on the upstanding arms are top planar surfaces.
3. The pivotal bone anchor assembly of claim 2 , wherein the top planar surfaces on the upstanding arms are configured to remain spaced from the closure when the closure is used to lock the elongate rod within the pivotal bone anchor assembly.
4. The pivotal bone anchor assembly of claim 2 , wherein the protruding rotational abutment structure extends to the top planar surfaces on the upstanding arms.
5. The pivotal bone anchor assembly of claim 1 , wherein the protruding rotational abutment structure further comprises a pair of opposite radially offset protruding rotational abutment structures.
6. The pivotal bone anchor assembly of claim 1 , wherein the pressure insert further includes an at least partial spherical lower surface configured to engage the partial spherical surface of the capture portion of the shank.
7. The pivotal bone anchor assembly of claim 1 , wherein the substantially cylindrical surface of the receiver further comprises a recess adjacent the longitudinally-extending rotation abutment surface configured to receive the protruding rotational abutment structure upon the rotation of the pressure insert about the vertical centerline axis of the receiver.
8. The pivotal bone anchor assembly of claim 1 , wherein the ring retainer includes a partially spherical inner surface including substantially a same radius as that of the partial spherical surface of the capture portion of the shank.
9. The pivotal bone anchor assembly of claim 1 , wherein the ring retainer further comprises first and second spaced ends making the ring retainer compressible.
10. The pivotal bone anchor assembly of claim 1 , wherein the ring retainer is non-pivoting with respect to the receiver when the shank is angulated relative to the receiver in a non-locked orientation.
11. The pivotal bone anchor assembly of claim 1 , wherein the pressure insert is top loaded into the first open channel of the receiver.
12. The pivotal bone anchor assembly of claim 1 , wherein the shank is cannulated with a central opening extending through an entire length thereof.
13. A pivotal bone anchor assembly for a securing an elongate rod to a bone of a patient via a closure and configured to be acted upon by a drive tool, the pivotal bone anchor assembly comprising:
a receiver comprising a vertical centerline axis, a base defining a cavity communicating with a bottom surface of the receiver through a bottom opening and including a lower circumferential groove adjacent the bottom opening having an upward-facing support surface, a pair of spaced apart upright arms extending upward from the base to define a first open channel configured to receive the elongate rod and including an integral discontinuous downward-facing surface below a discontinuous closure mating structure, and a substantially cylindrical surface between the cavity and the discontinuous downward-facing surface including a vertically-aligned rotational abutment structure;
a shank comprising a capture portion with a partial spherical surface and a central drive tool-engaging structure formed therein, and an anchor portion opposite the capture portion configured to fix to the bone, the capture portion being uploadable into the cavity of the receiver through the bottom opening;
a ring retainer comprising an open ring body having outer surfaces and an inner surface, the ring retainer being uploadable into the groove through the bottom opening of the receiver after the capture portion with the outer surfaces being engageable with the upward-facing support surface of the lower circumferential groove and the inner surface being engageable with the capture portion so as to hold the capture portion within the cavity while allowing for pivotal movement between the receiver and the shank; and
a pressure insert comprising a cylindrical body with upstanding arms, an upwardly-facing rod-receiving curvate surface extending between the upstanding arms to define a second open channel configured to receive the elongate rod, and a central opening configured to allow the drive tool to pass through to engage the drive tool-engaging structure of the shank, the upstanding arms having upwardly-facing surfaces located radially outward from the second open channel and outer side surfaces with a protruding rotational abutment structure formed therein, the pressure insert being positionable into the receiver into a first position adjacent the substantially cylindrical surface in which the central opening is centered on the vertical centerline axis of the receiver, the upwardly-facing surfaces on the upstanding arms are located adjacent to and angularly spaced from the discontinuous downward-facing surface, the protruding rotational abutment structure is angularly spaced from the longitudinally-extending rotation abutment surface, and the second open channel is transverse to the first open channel,
wherein after being positioned into the first position, the pressure insert is rotatable about the vertical centerline axis of the receiver until the protruding rotational abutment structure of the pressure insert engages with the vertically-aligned rotational abutment structure of the receiver to inhibit further rotation of the pressure insert in at least one direction, the second open channel of the pressure insert is aligned with the first open channel, and the upwardly-facing surfaces on the upstanding arms have rotated at least partially under the discontinuous downward-facing surface to inhibit the pressure insert from moving back up within the receiver.
14. The pivotal bone anchor assembly of claim 13 , wherein the upwardly-facing surfaces on the upstanding arms of the pressure insert are top planar surfaces.
15. The pivotal bone anchor assembly of claim 14 , wherein the protruding rotational abutment structure on the pressure insert extends to the top planar surfaces on the upstanding arms.
16. The pivotal bone anchor assembly of claim 13 , wherein the protruding rotational abutment structure on the pressure insert further comprises a pair of opposite radially offset protruding rotational abutment structures.
17. The pivotal bone anchor assembly of claim 13 , wherein the vertically-aligned rotational abutment structure of the receiver further comprises a vertically-aligned stop or abutment wall.
18. The pivotal bone anchor assembly of claim 13 , wherein the substantially cylindrical surface of the receiver further comprises a recess adjacent the vertically-aligned rotational abutment structure configured to receive the protruding rotational abutment structure upon the rotation of the pressure insert about the vertical centerline axis of the receiver.
19. The pivotal bone anchor assembly of claim 13 , wherein the substantially cylindrical surface of the receiver includes a run-out surface located directly beneath the discontinuous closure mating structure.
20. The pivotal bone anchor assembly of claim 13 , wherein the discontinuous closure mating structure further comprises a partial helically wound guide and advancement structure.
21. The pivotal bone anchor assembly of claim 13 , wherein the partially spherical surface of the capture portion of the shank is configured to extend above the ring retainer for engagement by a lower surface of the pressure insert.
22. The pivotal bone anchor assembly of claim 13 , wherein the pressure insert is top loaded into the first open channel of the receiver.
23. The pivotal bone anchor assembly of claim 13 , wherein the inner surface of the ring retainer further comprises a partially spherical inner surface complementary with the partial spherical surface of the capture portion of the shank.
24. The pivotal bone anchor assembly of claim 13 , wherein the ring retainer is rotational within the groove.
25. The pivotal bone anchor assembly of claim 13 , wherein the shank is cannulated with a central opening extending through an entire length thereof.
26. The pivotal bone anchor assembly of claim 13 and further comprising the elongate rod and the closure, wherein the closure is configured for positioning entirely within the first open channel of the receiver above the elongate rod and in engagement with the discontinuous closure mating structure of the upstanding arms to apply a downward pressure to a top of the elongate rod, so as to secure the elongate rod to the bone of the patient.
27. The pivotal bone anchor assembly of claim 26 , wherein the top planar surfaces on the upstanding arms of the pressure insert are configured to remain spaced from the a bottom surface of the closure when the closure is used to lock the elongate rod within the pivotal bone anchor assembly.