US Patent 7635379 Pedicle screw assembly with bearing surfaces

A motion interface structure for use with a pedicle screw is provided, the motion interface structure defining a central passage having an internal face. A helical thread is formed on at least a portion of the internal face of the central passage. The motion interface element is designed to cooperate with an upstanding region of a pedicle screw. The upstanding region includes a threaded region that is adapted to threadingly engage the helical thread associated with the motion interface element. The motion interface element may take the form of a spherical element or a universal joint mechanism. The pedicle screw and motion interface element may be incorporated into a spinal stabilization system that includes one or more additional pedicle screw/motion interface element subassemblies. The spinal stabilization system may also include a dynamic stabilizing element that provides clinically efficacious results.