Patent ID: 7967850
Filing Date: 2011-06-28
Classification: A61B

Abstract:
1. A polyaxial bone anchor comprising: a) a shank having a body for fixation to a bone and an integral upper portion, the upper portion having an upper end surface and an outer surface with a first helically wound guide and advancement structure thereon; b) a receiver having a top portion and a base, the receiver top portion defining an open channel, the base having a seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an external of the base through an opening sized and shaped to receive the shank upper portion therethrough; c) a compression insert disposed in the receiver, the insert having a mating surface exclusively frictionally engageable with the upper end surface of the shank upper portion; and d) a retainer having an external surface and a central bore with an internal surface defining the central bore having a second helically wound guide and advancement structure thereon, the first helically wound guide and advancement structure configured to rotatably mate with the second helically wound guide and advancement structure to secure the retainer to the shank upper portion within the receiver, the shank upper portion and the retainer being in fixed 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 external surface being in slidable engagement with the receiver seating surface, the retainer being substantially spaced from the compression insert at any and all angular positions of the shank with respect to the receiver.