US Patent 8460310 Surgical base unit and retractor support mechanism

An apparatus and methods for exerting force on a first bone with respect to a fulcrum, which may be a second bone. A base structure, mechanically coupled to the fulcrum, is coupled to the closure top so that a force may be exerted by the base structure, acting against the fulcrum, in at least one of axial and transverse directions with respect to a pedicle screw inserted into bone. A leg extension, allowing force to be applied through the pedicle screw to a bone, has a first end rotatably coupled to the base structure; and a second end threaded as the closure top. The base structure may also support a retractor in a manner local to the immediate region of surgery.