| 主权项 |
1. A bone anchor comprising:
a) a shank having an elongate body and a head with a radiused surface, the body being configured for fixation to a bone; b) a receiver having a top portion and a base having a substantially cylindrical outer surface and a central axis of rotation, the receiver top portion defining a channel for receiving a longitudinal connecting member, the base having an internal seating surface partially defining a cavity, the channel communicating with the cavity, the cavity communicating with an exterior of the base through a receiver lower opening; c) a substantially cylindrical sleeve disposed about and closely receiving the receiver base, the sleeve being axially slidable with respect to the receiver during assembly of the shank with the receiver; d) a retainer having a compressible upper portion, a middle portion and an expandable lower portion, the upper portion having a first structure engaging the receiver at the internal seating surface, the lower portion expandable about the shank head, the expandable lower portion having a second structure engaging the sleeve and prohibiting movement of the sleeve in an axial direction after the shank is captured with the retainer lower portion, the retainer being rotatable with respect to the receiver prior to fixing of an angle of the shank with respect to the receiver; and e) a compression insert engaging both the retainer upper portion and the shank radiused surface. |
