Abstract: A threaded connection for medical implants utilizes root and crest interfnce profile, such that the major and minor diameters of the thread profile on the male and female members of the connection are selected such that the minor diameter of one member is larger than the major diameter of the other, such that an interference condition is created along the helical path of the thread. This interference condition increases the radial stability of the connection and increases the torque required to loosen the connection when made up.

Abstract: An improved thread profile for use in medical implants utilizes a negative o slightly positive load flank inclination to minimize radial separation of the threaded connection by increasing the radial force required to overcome the surface and interference resistance to relative motion between the made-up abutting load faces of the connector threads.

Abstract: A threaded connection for use in medical implant surgery which utilizes a read profile which includes a load flank, a stab flank, a root intermediate the stab flank and load flank, and a crest intermediate the load flank and stab flank. The distance, measured paraxially, which the screw moves one complete revolution of the connection, is the lead of the thread. In the invention, the lead varies for either the male or female member of the connector such that the load flank, effectively, is moved away from axial interference with the cooperative member as the thread is "made up" or engaged. Accordingly, the load flank interface along the length of the connection is stressed, rather than having the load flank interface stressed predominately at the end turns of the thread, as often occurs under loading of the thread. In this manner, the stress loading of the thread is spread over the multiple turns of the thread, and pre-load is not lost by the yielding of the end turn.

Abstract: A connection for components in a medical implant assembly utilizes a tapered mating surface on each component with cylindrical splines and flutes formed on each mating surface such that the surfaces are complementary to the extent that the splines of one surface are received in the flutes of the adjacent surface. Each surface is continuous with no discontinuity which would act as a stress raiser or enhance concentration of stress in one locale. The complementary surfaces are urged into registry by a screw connection coaxially through the surfaces.