Thread-thru polyaxial pedicle screw system

Abstract

A thread-thru polyaxial pedicle screw fastening system. The fastening system consists of an anchoring bone screw having threads on one end for use in anchoring to the screw to the spine and a spherical connector on the other end operating as a pivot point about which a U-shaped connecting assembly moves in a polyaxial fashion. The U-shaped connecting assembly, for receipt of a spinal connecting rod, has a biased retainer ring for maintaining a positive tension between the connecting assembly and the anchored screw. The system allows for an improved manufacturing step wherein the threaded shank of a bone screws can be passed through a lower portion of the connecting assembly allowing a variety of bone screw sizes to be used with a common sized connector. A resilient component positioned between the upper retainer ring and the connecting assembly permits relative predetermined placement and retention of the spherical connector relative to the connector assembly due to the force generated by the resilient component and frictional engagement between the surfaces of spherical connector, the retainer ring and the connector assembly. The polyaxial ball and socket can be locked into a fixed position.