| CPC A61B 17/7035 (2013.01) [A61B 17/7032 (2013.01); A61B 17/863 (2013.01); A61B 17/8665 (2013.01); A61B 17/8685 (2013.01); A61B 2017/8655 (2013.01); A61B 2090/037 (2016.02)] | 25 Claims |

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1. A pivotal bone anchor assembly intended for securing an elongate rod to a bone of a patient, the pivotal bone anchor assembly comprising:
a receiver comprising a base defining a lower portion of a central bore centered about a vertical centerline axis and communicating with a bottom surface of the base through a partially circular bottom opening, and an upper portion with opposed internal surfaces extending between a front face and a back face of the receiver to define a first channel configured to receive the elongate rod, the central bore extending upward from the bottom opening through the first channel to a top of the receiver and including a guide and advancement structure adjacent the top of the receiver configured for engagement with a closure top and a lower seating surface adjacent the bottom opening, at least a portion of the bottom surface of the base extending perpendicular to the vertical centerline axis and the bottom opening including a first cut-out portion extending radially outward through the bottom surface of the base;
a bone anchor comprising a longitudinal axis, a shank body with a threaded anchor portion configured for attachment to the bone, an upper end portion opposite the threaded anchor portion, and a neck extending between the shank body and the upper end portion, the upper end portion having a rounded shape including a partially-spherical upper outer surface at a top end of the upper end portion and a partially-spherical lower outer surface transitioning downwardly and inwardly toward the neck, the upper end portion of the bone anchor being positionable into the lower portion of the central bore with the bone anchor extending downward through the bottom opening and with the lower outer surface configured for pivotal engagement with the lower seating surface of the base in an unlocked configuration prior to the pivotal bone anchor assembly being locked by the closure top, so as to provide for a first range of pivotal articulation of the bone anchor with respect to the receiver in a plurality of directions radial to the vertical centerline axis of the receiver; and
a compression insert positionable in the central bore of the receiver, the compression insert comprising an insert body and a pair of upstanding insert arms defining a second channel configured to receive the elongate rod, the second channel being alignable with the first channel when the compression insert is positioned in the receiver, the insert body having a through bore and a downwardly-facing concave lower surface configured to engage the partially-spherical upper outer surface of the bone anchor without engaging the partially-spherical lower outer surface when the longitudinal axis of the bone anchor is aligned with the vertical centerline axis of the receiver, the concave lower surface including a second cut-out portion alignable with the first cut-out portion,
wherein the neck and at least a portion of the upper end portion of the bone anchor are positionable in the first cut-out portion and the second cut-out portion, respectively, to provide for a second range of pivotal angulation of the bone anchor with respect to the receiver in the single direction of the cut-out portions radial to the vertical centerline axis of the receiver, the second range of pivotal articulation being greater than the first range of pivotal articulation.
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