Patent ID: 8439958
Filing Date: 2013-05-14
Classification: A61B,Y10T

Abstract:
1. A polyaxial bone screw assembly comprising: (a) a shank having a body for fixation to a bone and a capture structure extending upward from the body; the capture structure having an externally threaded portion; (b) a head having a top portion and a base, the head top portion defining an open channel adapted to receive an elongate implant, the base having an interior seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through an opening sized and shaped to receive the capture structure therethrough; (c) a retaining ring having an external surface and a central bore configured to be received on an exterior of the capture structure with the capture structure threaded portion extending above the retaining ring, the retaining ring external surface configured to be in slidable mating engagement with the seating surface of the head so as to enable selective angular positioning of the shank body with respect to the head during positioning in a non locked configuration; the retaining structure and the shank being joined when assembled so as to be polyaxially pivotal together with respect to the head during positioning; and (d) a fastener having a threaded internal surface that threadably mates with the shank capture structure threaded portion so as to secure the fastener and the retaining ring to the capture structure within the head cavity, the combined shank and fastener having driving structure adapted to mate with a tool for operably implanting the shank in a bone of a patient, after the shank, retainer ring, fastener and head are assembled, the shank capture structure receiving downward pressure during locking of the shank relative to the head to lock the shank in a desired angular configuration with respect to the head in a locked configuration.