Patent ID: 8556938

Claim:
In a polyaxial bone anchor, the improvement comprising: a) a receiver defining a chamber communicating with a channel, the channel sized and shaped for receiving a portion of a longitudinal connecting member, the chamber having an upper and lower portion; b) a shank having an upper portion and the chamber upper portion being wider than the shank upper portion; and c) an expandable a retainer having a non-expanded configuration and an expanded configuration, the retainer being narrower than the chamber upper portion in the non-expanded configuration, the retainer being located in the chamber lower portion in the non-expanded configuration, the retainer being pushed to the chamber upper portion during assembly when the shank upper portion is uploaded into the receiver chamber, and thereafter the retainer expanding to the expanded configuration, so as to receive the shank upper portion therethrough and capture the shank upper portion in the chamber by returning to the non-expanded configuration.