Polyaxial bone anchor with articulating retainer and multi-start closure
An open polyaxial bone anchor includes a pre-assembled receiver, retaining member and compression insert that may be popped-on or snapped-on to the shank upper portion prior to or after implantation of the shank into a vertebra. Cooperating closures have at least two helically wound forms thereon providing a multi-start closing mechanism for use between spaced arms of the bone anchor having mating helically wound structure thereon.
1 . In a polyaxial bone anchor, the improvement comprising:
a) a receiver having an inner surface partially defining a chamber communicating with a first channel defined by opposed upstanding arms, the first channel sized and shaped for receiving a portion of a longitudinal connecting member, the chamber communicating with a lower opening, the inner surface having a first notch formed thereon, the first notch located beneath one of the arms;
b) a shank having a threaded body integral with an upper portion, the upper portion having a first curved surface portion located near a top of the upper portion, the first curved surface having a first radius, the shank body extending out of and downwardly from the receiver lower opening;
c) a resilient open retainer having a second outer curved surface portion with a second radius, the second radius being different than the shank first curved surface portion first radius, the retainer located in the chamber, the retainer expandable in the chamber about the shank upper portion and receiving the first curved surface portion therethrough to capture the shank upper portion in the chamber, the retainer being fixedly engaged to the shank at an interface located along the shank upper portion between the first curved surface portion and the shank body, the retainer and shank being in fixed relation to one another and in pivotal relationship with the receiver prior to locking of the retainer against the receiver; and
d) an insert located between the shank upper portion and the portion of the longitudinal connecting member located in the receiver channel, the insert having a second notch formed in a bottom surface thereof sized and shaped for receiving a portion of the retainer when the shank threaded body is pivoted toward the first notch in the receiver.
2 . The improvement of claim 1 further comprising:
an inwardly protruding abutment stop extending from the receiver surface and a recess formed in the abutment stop, the abutment stop being in engagement with the retainer during expansion of the retainer about the shank upper portion, the recess sized and shaped to receive a portion of the retainer to a position above the abutment stop when the shank body is pivoted toward the receiver first notch.
3 . The improvement of claim 1 wherein surfaces forming the receiver notch are stepped.
4 . The improvement of claim 1 wherein the insert has opposed outwardly extending projections.
5 . The improvement of claim 1 wherein the insert has a pair of opposed inner recesses sized and shaped for receiving tooling.
6 . In a polyaxial bone anchor, the improvement comprising:
a) a receiver having an inner surface partially defining a chamber communicating with a first channel defined by opposed upstanding arms, the first channel sized and shaped for receiving a portion of a longitudinal connecting member, the chamber communicating with a lower opening;
b) a shank having a threaded body integral with an upper portion, the upper portion having a first curved surface portion located near a top of the upper portion, the first curved surface having a first radius, the shank body extending out of and downwardly from the receiver lower opening;
c) a resilient open retainer having a second outer curved surface portion with a second radius, the second radius being different than the shank first curved surface portion first radius, the retainer located in the chamber, the retainer expandable in the chamber about the shank upper portion and receiving the first curved surface portion therethrough to capture the shank upper portion in the chamber, the retainer being fixedly engaged to the shank at an interface located along the shank upper portion between the first curved surface portion and the shank body, the retainer and shank being in fixed relation to one another and in pivotal relationship with the receiver prior to locking of the retainer against the receiver; and
d) an insert located between the shank upper portion and the portion of the longitudinal connecting member located in the receiver channel, the insert having a notch formed in a bottom surface thereof sized and shaped for receiving a portion of the retainer when the shank is pivoted at a certain angle.
7 . The improvement of claim 6 further comprising:
an inwardly protruding abutment stop extending from the receiver surface and a recess formed in the abutment stop, the abutment stop being in engagement with the retainer during expansion of the retainer about the shank upper portion, the recess sized and shaped to receive a portion of the retainer to a position above the abutment stop when the shank and attached retainer are pivoted at a particular angle within the receiver.
8 . The improvement of claim 6 wherein the receiver further comprises a stepped lower cut-out surface.
9 . The improvement of claim 8 wherein the stepped lower cut-out surface is aligned with the insert notch.
10 . The improvement of claim 6 wherein the insert has opposed outwardly extending projections.
11 . The improvement of claim 6 wherein the insert has a pair of opposed inner recesses sized and shaped for receiving tooling.
12 . In a polyaxial bone anchor, the improvement comprising:
a) a receiver having an inner surface partially defining a chamber communicating with a first channel defined by opposed upstanding arms, the first channel sized and shaped for receiving a portion of a longitudinal connecting member, the chamber communicating with a lower opening, the receiver inner surface having an inwardly protruding abutment stop extending from the receiver surface and a recess formed in the abutment stop;
b) a shank having a threaded body integral with an upper portion, the upper portion having a first curved surface portion located near a top of the upper portion, the first curved surface having a first radius, the shank body extending out of and downwardly from the receiver lower opening;
c) a resilient open retainer having a second outer curved surface portion with a second radius, the second radius being different than the shank first curved surface portion first radius, the retainer located in the chamber, the retainer expandable in the chamber and abutting against the abutment stop when the retainer expands about the shank upper portion and receives the first curved surface portion therethrough to capture the shank upper portion in the chamber, the retainer subsequently being fixedly engaged to the shank, the retainer and shank being in fixed relation to one another and in pivotal relationship with the receiver prior to locking of the retainer against the receiver; and
d) an insert located between the shank upper portion and the portion of the longitudinal connecting member located in the receiver channel, the insert having a notch formed in a bottom surface, the insert notch and the receiver abutment recess receiving a portion of the retainer when the shank is pivoted at a certain angle with respect to the receiver.
13 . The improvement of claim 12 wherein the receiver further comprises a stepped lower cut-out surface.
14 . The improvement of claim 13 wherein the stepped lower cut-out surface is aligned with the insert notch.