Orthopedic implant having a porous surface and method of making same

Abstract

An orthopedic implant has a porous surface with a plurality of pores, some of which are provided with a pores-within-a-pore structure. The pores-within-a-pore structure has a pore opening ranging in size between 10 and 800 microns. The present invention also discloses a process for making an orthopedic implant which is provided in the surface thereof with a pores-within-a-pore porous structure.

What is claimed is:  
     
         1 . An orthopedic implant having a plurality of pores on at least a portion of its surface, wherein part of the plurality of pores have a pores-within-a-pore porous structure, said pores-within-a-pore porous structure comprising a first-stepped pore on said surface, and at least one second-stepped pore within the first-stepped pore, and optionally a n-stepped pore within a (n−1)-stepped pore, wherein n is third to sixth, wherein said first-stepped pore has an pore opening ranging in size between 10 and 800 microns.  
     
     
         2 . The orthopedic implant as defined in  claim 1 , wherein at least 30% of said plurality of pores have said pores-within-a-pore porous structure, and said second-stepped pore has an pore opening ranging in size between 10 and 500 microns.  
     
     
         3 . The orthopedic implant as defined in  claim 2 , wherein at least 50% of said plurality of pores have said pores-within-a-pore porous structure, said first-stepped pore has an pore opening ranging in size between 50 and 600 microns, and said second-stepped pore has a pore opening ranging in size between 50 and 400 microns.  
     
     
         4 . The orthopedic implant as defined in  claim 2 , wherein said first-stepped pore having an opening ranging in size between 100 and 500 microns, and said second-stepped pore has a pore opening ranging in size between 50 and 300 microns.  
     
     
         5 . A process for making an orthopedic implant, comprising the following steps: 
 forming a plurality of initial pores on at least one portion of a surface of an orthopedic implant; and    forming a pores-within-a-pore structure within the plurality of initial pores, said pores-within-a-pore porous structure comprising a first-stepped pore on said surface, and at least one second-stepped pore within the first-stepped pore, and optionally a n-stepped pore within a (n−1)-stepped pore, wherein n is third to sixth, wherein said first-stepped pore has an pore opening ranging in size between 10 and 800 microns,    wherein an intermediate electric current density pore etching method is used to form said pores-within-a-pore structure.    
     
     
         6 . The process as defined in  claim 5 , wherein said initial pores have a size ranging between 0.2 and 500 microns.  
     
     
         7 . The process as defined in  claim 6 , wherein said initial pores have a size ranging between 1 and 100 microns.  
     
     
         8 . The process as defined in  claim 5 , wherein said forming said plurality of initial pores on at least one portion of said surface of said orthopedic implant process is carried out by a high electric current density pore etching method.  
     
     
         9 . The process as defined in  claim 8 , wherein said high electric current density pore etching method comprises submerging the orthopedic implant in an electrolyte solution to carry out electrolysis by an electric current density higher than 0.2 A/cm 2  for a period of 30 seconds to 5 minutes.  
     
     
         10 . The process as defined in  claim 9 , wherein the electrolyte solution contains 2-5% by weight of NaCl; wherein said current density is at least 0.3 A/cm 2 ; and wherein said electrolysis is carried our for a period of 1 and 3 minutes.  
     
     
         11 . The process as defined in any one of  claims 5  to  10 , wherein said intermediate electric current density pore etching method comprises submerging the orthopedic implant in an electrolyte solution to carry out electrolysis by an electric current density ranging between 0.1 and 0.8 A/cm 2  for a period of 3 to 30 minutes.  
     
     
         12 . The process as defined  claim 11 , wherein the electrolyte solution contains 2-5% by weight of NaCl; wherein said current density ranges between 0.2 and 0.7 A/cm 2 ; and wherein the electrolysis time ranges between 5 and 20 minutes.