| 摘要 |
An intramedullary interlock screw (16) includes an elongate shank (18) having a preferably cylindrical shank outer surface, and an external thread (20) disposed helically about the shank (18) and having a thread outer surface (26) coaxial with and substantially parallel to the shank outer surface. The shank diameter as determined by the shank outer surface is at least 0.75 times the thread diameter as determined by the thread outer surface (26), and most preferably is 0.85-0.9 times the thread diameter, resulting in a considerable reduction in thread height as compared to similarly sized conventional bone screws. Further, the thread outer surface (26) has a width at least twenty percent of the thread pitch, a substantial increase over the corresponding percentage in conventional bone screws. Both features contribute to an increase in the strength of the screw, in terms of resistance to bending forces applied laterally, i.e. perpendicular to the screw length. The increased thread width in proportion to the thread pitch reduces undesirable stress concentrations at the interface of the interlock screw (16) and an intramedullary nail (58).
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