The present invention is a selectively expandable bone fixation screw-sleeve device which provides substantially greater holding strength in human bone than other bone screw devices. The sleeve element of this invention includes several embodiments, each having at least one corresponding screw element for selectively expanding a portion of the sleeve once it has been inserted into the bone. More specifically, in several embodiments, the sleeve includes a series of vertical slots in the end, or ends, of the cylindrical body of the sleeve. The slots define, therebetween, sections which are contiguous with the remainder of the cylindrical body, and which may rotate radially outward. In these embodiments, the sections are designed having a varying thickness, for example a single or double wedge profile, such that the insertion of the screw element into the sleeve deforms the shape of the sleeve by causing the sections to flair outward. In a different embodiment, the slots, and sections, are designed into the axially intermediate central portion of the cylindrical sleeve, and therefore flair outwardly therefrom upon insertion of a screw within the sleeve. As this invention is intended to provide imporved fixation support for orthopedic implantation assemblies, each embodiment may further include means coupled or integral with the sleeve or screw for coupling an orthopedic implant to it.