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.

1 . An implant manufacturing process for producing an implant including an insertion portion configured for insertion into a prepared cavity of a live bone, the live bone at the cavity having a bone variable material properties profile, the method comprising:
 a) manufacturing additively at least an insertion portion of the implant, said insertion portion including a first set of structural regions and a second set of structural regions, each set of structural regions including a material properties profile; and   b) altering, during said manufacturing step a), said material properties profile of each said structural regions wherein said material properties profile of said first set of structural regions is different from said material properties profile of said second set of structural regions, wherein said material properties profiles of said sets of structural regions collectively define an implant material properties profile, and wherein said implant material properties profile is configured to produce one or both of a propensity for insertion and a propensity for a resistance to a fracture.   
     
     
         2 . The method 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. 
     
     
         3 . The method 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. 
     
     
         4 . The method of  claim 3  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. 
     
     
         5 . The method of  claim 3  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. 
     
     
         6 . The method of  claim 3  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. 
     
     
         7 . The method of  claim 3  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. 
     
     
         8 . The method of  claim 3  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. 
     
     
         9 . The method 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. 
     
     
         10 . The method 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. 
     
     
         11 . The method of  claim 10  wherein said support system includes a first set of components integrated into said region. 
     
     
         12 . The method of  claim 11  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.