Abstract: An apparatus for use in placing an implant into a patient is disclosed. The apparatus features an outer assembly having an outer shaft with an expandable driving member at its distal end and an inner canulated shaft that fits within and cooperates with the outer shaft to affect the driving member. The inner shaft includes an actuation knob attached to the proximal end of the inner shaft. A locking or driving thread is included on the outer surface of the inner shaft, proximal to the adjustment knob. The outer shaft includes a housing with the threaded interior such that when the inner shaft is mounted within the outer shaft, the driving thread operates with the threaded interior of the housing to allow for the inner shaft to be advanced along the inside of the outer shaft as the knob is turned. The tip of the inner shaft interacts with the interior of the driving member to expand the driving member.

Abstract: A surgical screw is provided for use in fixing or fusing bone. The screw may include each of an inner and an outer helical thread that extends along its length. The geometries of the helices and the relationship between the inner thread and the outer thread may improve the performance of the screw. For example, the two helices may operate to improve the manner in which the screw can be strained.