A screw fastener for attachment to an orthopedic component such as an orthopedic plate for use in connection with fracture fixation, joint reconstruction or spinal stabilization or fusion is disclosed as having a shank with at least two different shank diameters, one in a plate engaging portion of the shank and one in the bone or other component engaging portion of the shank. At least two of the different shank diameters on the shank include threads, the threads on the two different diameter portions each having substantially the same thread height and pitch. A plate having a threaded aperture, or an adapter having a threaded aperture, is sized such that the threads of the smaller diameter shank portion engage and cooperate with the internal threads of the aperture to correctly align the screw fastener and the implant as the screw fastener is threaded through the implant. The threads on the larger diameter shank portion and the internal threads of the aperture of the implant are sized so that the threads of the larger diameter shank portion are fully engaged with the internal threads of the orthopedic implant.
