| CPC A61B 17/7037 (2013.01) [A61B 17/7032 (2013.01); A61B 17/7035 (2013.01); A61B 17/7091 (2013.01); A61B 17/863 (2013.01); A61B 17/864 (2013.01); A61B 2090/037 (2016.02)] | 17 Claims |
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1. A pivotal bone anchor assembly for securing an elongate rod to a bone of a patient via a threaded closure top, the pivotal bone anchor assembly comprising:
a receiver comprising:
a vertical centerline axis;
a base defining a lower portion of a central bore communicating with a bottom of the receiver through a lower opening, the lower portion including an interior seating surface extending circumferentially and continuously around the central bore above the lower opening and a lower cylindrical portion adjacent to and extending upward from the interior seating surface, with at least a portion of the bottom of the receiver being defined by a sloped planar surface oriented at a non-perpendicular angle with respect to the vertical centerline axis of the receiver and extending upward from a bottommost surface of the bottom of the receiver toward the interior seating surface to define an expanded portion of the lower opening; and
first and second upright arms integrally formed with and extending upward from the base with opposed internal surfaces extending between a front face and a back face of the upright arms to define an open channel configured to receive the elongate rod, the central bore extending upward through the open channel to top surfaces of the upright arms and comprising the lower cylindrical portion having a first diameter, an upper wider portion above the lower cylindrical portion having a second diameter greater than the first diameter, and an upper internal thread form above the upper wider portion configured for engagement with the threaded closure top, each upright arm including:
a side outer surface opposite the internal surface of the respective upright arm and extending downward across the base toward the bottom surface of the receiver;
a break-off extension integrally formed with and extending upwardly from an inner edge portion on the top surface of the respective upright arm, the break-off extension having an internal thread form continuous with the upper internal thread form of the respective upright arm and an outer surface with a lower portion that tapers downwardly and inwardly toward the vertical centerline axis of the receiver and the inner edge portion; and
a radiused non-threaded tool engagement groove extending horizontally and entirely across the side outer surface to the front face and the back face of the respective upright arm, each tool engagement groove being isolated from the central bore and being located below the top surface of each upright arm;
a shank comprising a head having an at least partial spherical outer surface and an anchor portion opposite the head configured for attachment to the bone, the shank configured for positioning within the lower portion of the central bore with the shank extending downward through the lower opening and being pivotable with respect to the receiver in an unlocked configuration; and
an insert having a body configured for positioning within the lower cylindrical portion of the central bore with a downwardly-opening concave surface configured to engage the head of the shank, and a pair of insert arms defining an upwardly-facing curvate surface between the insert arms configured to receive the elongate rod when the elongate rod is positioned in the open channel, with upper ends of the insert arms projecting laterally outward and configured for positioning within the upper wider portion of the central bore,
wherein the expanded portion of the lower opening is configured to provide an increase in clearance for increased pivotal movement of the shank with respect to the receiver in the direction of the expanded portion of the lower opening when the head of the shank is received within the lower portion of the central bore of the receiver.
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