US Patent 7686833 Ball jointed pedicle screw and rod system

A pedicle screw assembly includes pedicle screw having a plurality of spaced-apart posts. A ball collet having a ball collet bore is seated on the pedicle screw between the posts and a rod is gripped by an inner surface of the ball collet bore. The assembly also includes a cap that is coupled to the posts, the cap applying a compressive force to the ball collet against a seat of said pedicle screw. A free end of the rod may be provided with various structures to enable such free end to be retained by another pedicle screw.