Pivotal bone anchor assembly with independent locking by a tool engaging an 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 uploadable 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. A pivotal bone anchor assembly configured for independent locking with an insert compressing tool prior to securing an elongate rod to a bone of a patient with a closure top, the pivotal bone anchor assembly comprising:
a receiver having a longitudinal axis, a base, and a pair of upstanding arms extending upwardly from the base with opposed inner surfaces defining an open channel configured for receiving the elongate rod, the inner surfaces of the upstanding arms having a closure top mating feature formed thereon, the base including a receiver cavity in communication with a bottom of the receiver through a bottom opening and with the open channel to define a receiver bore centered about the longitudinal axis, the arms configured to slidably and non-threadably receive the insert compressing tool in a direction parallel with the longitudinal axis;
a bone anchor having a capture portion with a spherical outer surface and an anchor portion configured for fixation to the bone, the capture portion configured to be pivotally disposed within the receiver cavity with the bone anchor extending through the bottom opening; and
an insert configured to be disposed at least partially within the receiver bore and thereafter configured for downward compression by the insert compressing tool until the insert comes into a compressive contact with the spherical outer surface of the capture portion of the bone anchor so as to independently lock a position of the bone anchor with respect to the receiver,
wherein with the insert compressing tool in a downward compression position, the elongate rod is receivable within the open channel of the receiver and lockable with the closure top to establish a locked configuration, and
wherein with the closure top maintaining the elongate rod and pivotal bone anchor assembly together in the locked configuration, the insert compressing tool is slidably removable from the receiver in a direction parallel with the longitudinal axis.
2. The pivotal bone anchor assembly of claim 1 ,
wherein the upstanding arms of the receiver further comprise a top surface, opposite front and back surfaces, and opposite outer side surfaces, and
wherein the outer side surfaces include tool attachment grooves extending horizontally to the front and back surface on each arm and spaced an equal and symmetrical distance below the top surface.
3. The pivotal bone anchor assembly of claim 2 , wherein the upstanding arms of the receiver further include outer grooves vertically formed into the outer side surfaces and configured to receive the insert compressing tool therein.
4. The pivotal bone anchor assembly of claim 1 , wherein the insert is configured to be held in place within the receiver bore by crimps formed in the receiver.
5. The pivotal bone anchor assembly of claim 1 , wherein the insert has a central bore configured to allow the passage of a driving tool therethrough to engage an internal drive aperture formed in the capture portion of the bone anchor.
6. The pivotal bone anchor assembly of claim 5 , wherein the insert further comprises tool engagement surfaces facing upward and positioned radially outward from the central bore of the insert.
7. The pivotal bone anchor assembly of claim 6 , wherein the tool engagement surfaces of the insert are configured to be uncovered by the elongate rod or by the closure top when the elongate rod is received within the open channel of the receiver and locked with the closure top.
8. The pivotal bone anchor assembly of claim 1 , wherein the insert further includes an internal recess configured to allow the insert to be manipulated within the receiver bore with a second tool after the insert is downwardly compressed to independently secure the pivotal bone anchor assembly.
9. The pivotal bone anchor assembly of claim 1 , wherein the insert is configured to be top loaded into the receiver bore.
10. The pivotal bone anchor assembly of claim 1 , further comprising the closure top, and wherein the closure top includes a helically wound guide and advancement structure formed into an outer sidewall surface and configured to engage the closure top mating feature formed into the opposed inner surfaces of the upstanding arms of the receiver to capture the elongate rod within the receiver open channel.
11. A pivotal receiver assembly configured for independent locking, via an insert compressing tool, to a head of a bone anchor having an anchor portion implantable into a bone of a patient, prior to securing an elongate rod to the receiver assembly and the patient bone anchor via a closure top, the pivotal receiver assembly comprising:
a receiver having a longitudinal axis, a base, and a pair of upstanding arms extending upwardly from the base with opposed inner surfaces defining an open channel configured for receiving the elongate rod, the inner surfaces of the upstanding arms having a closure top mating feature formed thereon, the base including a central opening in communication with a bottom surface of the base through a bottom opening and with the open channel to define a through-and-through aperture centered about the longitudinal axis, the upstanding arms configured to slidably receive the insert compression tool in a direction parallel with the longitudinal axis, the receiever configured to receive the head of the bone anchor in the base with the bone anchor extending downward through the receiver bottom opening and the receiver being pivotally movable with respect to the bone anchor; and
an insert configured to be disposed at least partially within the receiver and thereafter configured to be downwardly compressed by the insert compression tool until the insert comes into a compressive contact with a spherical outer surface of the head of the bone anchor so as to independently lock a position of the receiver with respect to the bone anchor,
wherein with the insert compressing tool in a downward compression position, the elongate rod is receivable within the open channel of the receiver and lockable with the closure top to establish a locked configuration, and
wherein with the closure top maintaining the elongate rod and pivotal bone anchor assembly together in the locked configuration, the insert compressing tool is slidably removable from the receiver in a direction parallel with the longitudinal axis.
12. The pivotal receiver assembly of claim 11 ,
wherein the upstanding arms of the receiver further comprise a top surface, opposite front and back surfaces, and opposite outer side surfaces, and
wherein the outer side surfaces include tool attachment grooves extending horizontally to the front and back surface on each arm.
13. The pivotal receiver assembly of claim 12 , wherein the upstanding arms of the receiver further include outer grooves vertically formed into the outer side surfaces and configured to receive the insert compressing tool therein.
14. The pivotal receiver assembly of claim 11 , wherein the insert is configured to be rotated about the longitudinal axis of the receiver within the receiver bore so as to move the insert into a position prior to be being compressed by the insert compressing tool.
15. The pivotal receiver assembly of claim 11 , wherein the insert has a central bore configured to allow the passage of a driving tool therethrough to engage the head of the bone anchor.
16. The pivotal receiver assembly of claim 15 , wherein the insert further comprises tool engagement surfaces facing upward and positioned radially outward from the central bore of the insert.
17. The pivotal receiver assembly of claim 16 , wherein the tool engagement surfaces of the insert are configured to be uncovered by the elongate rod or by the closure top when the elongate rod is received within the open channel of the receiver and locked with the closure top.
18. The pivotal receiver assembly of claim 11 , wherein the insert further includes an internal recess configured to allow the insert to be manipulated within the receiver with a second tool after the insert is downwardly compressed to independently lock the pivotal bone anchor assembly.
19. The pivotal receiver assembly of claim 11 , wherein the insert is configured to be top loaded into the receiver.
20. The pivotal receiver assembly of claim 11 , further comprising the closure top, and wherein the closure top includes a helically wound guide and advancement structure formed into an outer sidewall surface and configured to engage the closure top mating feature formed into the opposed inner surfaces of the upstanding arms of the receiver to capture the elongate rod within the receiver open channel.
21. A bone anchor assembly comprising the pivotal receiver assembly of claim 11 and further comprising the bone anchor, and wherein the bone anchor is cannulated by having a central opening extending along an entire length thereof.