Patent ID: 7476239
Filing Date: 2009-01-13
Classification: A61B

Abstract:
1. A polyaxial bone screw assembly comprising: a) a bone screw shank having an upper portion with a first engagement surface; b) a receiver having a cavity with a second engagement surface, the bone screw upper portion receivable in the cavity; c) a retaining and articulating structure receivable in the cavity between the shank upper portion and the receiver; the retaining and articulating structure having a third engagement surface operably mating with the shank first engagement surface and a fourth engagement surface operably mating with the receiver second engagement surface; the retaining and articulation structure being pivotal with respect to both the shank and the receiver so as to be able to freely move relative to both the shank and the receiver during positioning of the shank relative to the receiver; d) a first polyaxial articulation formed by the first engagement surface of the upper portion and the third engagement surface of the retaining and articulating structure; and e) a second polyaxial articulation formed by the fourth engagement surface of the retaining and articulating structure and the second engagement surface of the receiver whereby during positioning of the shank relative to the receiver compound articulation exists between the shank and the receiver.