A method and apparatus for exerting force on a first bone with respect to a fulcrum, which may be a second bone. A pedicle screw with a central threaded socket is inserted into the first bone, and a threaded closure top is driven into the central threaded socket of the pedicle screw. A base structure,...http://www.google.de/patents/US20060036245?utm_source=gb-gplus-sharePatent US20060036245 - Surgical base unit and retractor support mechanism
