Prosthetic joint and manufacturing method for same

Abstract

Provided is an artificial joint that improves fatigue strength and fixes to a bone. An artificial joint includes a stem portion having a distal end for insertion into a bone, a proximal end opposite the distal end, and a roughened surface portion provided in a proximal end-side portion, which has a rougher surface than a distal end-side portion, and which is larger in cross-sectional area than the distal end-side portion. The roughened surface portion includes a distal end-side edge section and a proximal end-side section, the distal end-side edge section including a distal end-side edge portion of the roughened surface portion, the proximal end-side section being configured as a section closer to the proximal end than the distal end-side edge section is to the proximal end. The distal end-side edge section has a surface roughness Ra 1 lower than a surface roughness Ra 2 , Ra 3 of the proximal end-side section.

1 . A method of producing an artificial joint that, the method comprising:
 preparing a base member including a stem portion having a distal end for insertion into a bone and a proximal end opposite the distal end; and   spraying a coating material on a surface of the stem portion,   wherein the time spraying to a first surface of the stem portion is shorter than the time spraying to a second surface of the stem portion,   wherein the first surface is located closer to the distal end than the second surface.   
     
     
         2 . The method as set forth in  claim 1 , the method further comprising:
 partially covering the base member with a masking material before the spraying.   
     
     
         3 . The method as set forth in  claim 2 , wherein:
 in the masking step, the masking material overhangs the stem portion in a cross section passing through a central axis of the stem portion; and   a sloped surface is formed on the first surface, the sloped surface sloping downward toward the distal end.   
     
     
         4 . The method as set forth in  claim 1 , wherein:
 a first portion has a cross-sectional area that is larger than a cross-sectional area at a second portion;   the first portion is a part of the stem portion where the first surface is located; and   the second portion is a part of the stem portion where the second surface is located.   
     
     
         5 . The method as set forth in  claim 1 , wherein the spraying comprises a thermal spraying process. 
     
     
         6 . The method as set forth in  claim 5 , wherein an arc thermal spraying machine or a plasma spraying machine is used for the spraying. 
     
     
         7 . The method as set forth in  claim 1 , wherein the stem portion contains a titanium alloy or pure titanium. 
     
     
         8 . The method as set forth in  claim 1 , wherein a thermal sprayed layer is formed by the spraying. 
     
     
         9 . The method as set forth in  claim 8 , wherein a surface roughness of the thermal sprayed layer on the first surface is lower than a surface roughness of the thermal sprayed layer on the second surface. 
     
     
         10 . The method as set forth in  claim 8 , wherein a thickness of the thermal sprayed layer on the first surface is less than a thickness of the thermal sprayed layer on the second surface. 
     
     
         11 . The method as set forth in  claim 8 , wherein an area of the thermal sprayed layer on the first surface is smaller than an area of the thermal sprayed layer on the second surface.