Mechanical assembly including exterior surface preparation

Abstract

A system and method for improving mechanical assemblies, such as prosthetic implants, intended to be installed in living tissue such as bone. Force-imparting devices are adapted and may include angularity, which may be introduced with specialized additive manufacturing, which may impart congruent cross-sections while providing variable stiffness. In some cases, the variable stiffness may be “stretchy” in a longitudinal direction and “rigid” in a radial directional which may provide an assembly bias. Additive manufacturing may allow the material of a prosthesis to be varied (e.g., density/porosity) to create variable stiffness over a length.

What is claimed as new and desired to be protected by Letters Patent of the United States is: 
     
         1 . A modular implant for at least a partial insertion into a portion of a bone, the portion of bone having a bone variable material properties profile, comprising:
 a stem configured for installation into the portion of bone, said stem including a cavity;   a neck configured for a first engagement with said cavity with said first engagement configured to mechanically join said neck to said stem, said neck including a trunnion;   a head configured for a second engagement with said trunnion with said second engagement configured to mechanically join said head to said neck; and   a support system disposed in a region of a foundation of the implant, said support system configured to provide a propensity for a resistance to a fracture of said region.   
     
     
         2 . The implant of  claim 1  wherein said support system includes a first set of components integrated into said region. 
     
     
         3 . The implant of  claim 2  wherein said support system includes a second set of components integrated into said region, said second set of components non-aligned with said first set of components. 
     
     
         4 . The implant of  claim 1  wherein said neck includes a first reference location, a second reference location spaced apart from said first reference location, and a neck variable material properties profile including said first reference locations with said neck variable material properties profile different from and generally compatible with the bone variable material properties profile and with said neck variable material properties profile between said reference locations including a monotonically changing stiffness when extending from said first reference location to said second reference location. 
     
     
         5 . The implant of  claim 1  wherein said stem includes an element selected from the group consisting of a prosthesis, a nail, an external fixator, an implant, a plate, and combinations thereof. 
     
     
         6 . The implant of  claim 1  wherein said neck variable materials property profile includes a varying materials property gradient responsive to changes in a set of material properties over a first region including said reference locations. 
     
     
         7 . The implant of  claim 6  wherein said first region extends from a first lateral edge of said neck to a second lateral edge of said neck, wherein said first lateral edge includes said first reference location, and wherein said second lateral edge includes said second reference location. 
     
     
         8 . The implant of  claim 6  wherein said first region extends from a first end of said neck to a middle portion of said neck wherein said middle portion of said neck is located about halfway between said first end and a second end of said neck, wherein one of said ends includes said first reference location, and wherein said middle portion includes said second reference location. 
     
     
         9 . The implant of  claim 6  wherein said neck includes a neck material and wherein said varying material properties gradient of said neck variable material properties profile includes variations in a material grain size of said neck material. 
     
     
         10 . The implant of  claim 6  wherein said neck includes a neck material and wherein said varying material properties gradient of said neck variable material properties profile includes variations in a porosity of said neck material. 
     
     
         11 . The implant of  claim 6  wherein said neck includes a neck material and wherein said varying material properties gradient of said neck variable material properties profile includes variations in a crystalline structure of said neck material. 
     
     
         12 . The implant of  claim 1  wherein the bone variable material properties profile includes a metric indicating a resistance of the bone to an elastic deformation selected from the group consisting of an elastic modulus, a Young's modulus, a shear modulus, a bulk modulus, a Poisson's ratio, a Lame's first parameter, a P-wave modulus, and combinations thereof. 
     
     
         13 . The implant of  claim 1  further including a support system disposed in a region of the implant, said support system configured to provide a propensity for a resistance to a fracture of said region. 
     
     
         14 . The implant of  claim 13  wherein said support system includes a first set of components integrated into said region. 
     
     
         15 . The implant of  claim 14  wherein said support system includes a second set of components integrated into said region, said second set of components non-aligned with said first set of components.