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...http://www.google.fr/patents/US7635379?utm_source=gb-gplus-shareBrevet US7635379 - Pedicle screw assembly with bearing surfaces
