Pivotal bone anchor assembly with bottom loaded shank head and articulating retainer

A pivotal bone anchor assembly intended for securing an elongate rod to a bone of a patient, the pivotal bone anchor assembly comprising:

• a shank having a body for fixation to the bone and an upper portion, the body and upper portion being aligned along a longitudinal axis of rotation thereof, the upper portion having an upper surface, a first section and a second section, the first section being below the upper surface and having a first width measured perpendicular to the longitudinal axis of rotation with a first radius, the second section located below the first section and having a second width measured perpendicular to the longitudinal axis of rotation with a second radius, the second radius being less than the first radius, the second section being disposed between the body and the first section;
• a receiver having a top portion and a base, the top portion of the receiver defining an open channel, the base having a seating surface partially defining a cavity, the open channel communicating with the cavity to define a central bore, the cavity communicating with an exterior of the base through a bottom opening sized and shaped to receive the upper portion of the shank therethrough;
• a retainer disposed within the cavity of the receiver, the retainer having a central opening with an internal surface sized and shaped to overlappingly receive the upper portion of the shank at the first section, the upper portion of the shank and the retainer being in non-swivelable relation to one another, both the upper portion and the retainer being in swivelable relation within the receiver, providing selective angular positioning of the shank with respect to the receiver, the retainer being in slidable engagement with the seating surface of the receiver, and a top surface of the shank extending above a top surface of the retainer;
• a compression insert disposed in the receiver, the compression insert having a rod-receiving surface alignable with the open channel of the receiver and opposite outer side recesses formed therein;
• and
• opposed inwardly-protruding integral structures extending inwardly from interior surfaces of the central bore of the receiver to engage with the outer side recesses of the compression insert to restrict rotational movement of the compression insert within the receiver,
• wherein the inwardly-protruding integral structures are formed in the receiver after the compression insert is disposed within the central bore and a rod-receiving surface of the compression insert is aligned with the open channel of the receiver.